AUTOMATIC TRANSMISSION PUMP APPARATUS OR PUMP APPARATUS

Abstract

The present invention provides a pump apparatus capable of preventing or reducing deterioration of efficiency of a pump. The pump apparatus includes a venturi portion provided on the way along a discharge passage. The venturi portion includes a small diameter portion having a smaller inner diameter than an inner diameter of the discharge passage from a discharge port to the venturi portion and an inner diameter gradually-increasing portion formed in such a manner that an inner diameter thereof gradually increases from the small diameter portion toward a downstream side of the discharge passage. The pump apparatus further includes a control valve configured to receive introduction of hydraulic fluid on an upstream side of the venturi portion and hydraulic fluid in the venturi portion. The control valve is configured to control a flow amount of hydraulic fluid to be supplied into an automatic transmission by switching a flow passage of the hydraulic fluid based on a differential pressure between a pressure on the upstream side of the venturi portion and a pressure in the venturi portion (50).

Description

TECHNICAL FIELD

The present invention relates to a pump apparatus.

BACKGROUND ART

Conventionally, there has been known a pump apparatus including a control valve. The control valve controls a flow amount of hydraulic fluid that the pump apparatus supplies to an apparatus. For example, a pump apparatus discussed in PTL 1 generates a differential pressure according to the flow amount to be discharged. The control vale controls the above-described flow amount by switching a flow passage of the hydraulic fluid based on the above-described differential pressure.

CITATION LIST

Patent Literature

PTL 1: Japanese Patent Application Public Disclosure No. 2010-14074

SUMMARY OF INVENTION

Technical Problem

However, the conventional pump apparatus uses an orifice for generating the differential pressure. Therefore, efficiency of the pump may be deteriorated. An object of the present invention is to provide a pump apparatus capable of preventing or reducing deterioration of the efficiency of the pump.,

Solution To Problem

To achieve the above-described object, one embodiment of the present invention includes a venturi portion provided on the way along a discharge passage to generate a differential pressure and having an inner diameter gradually increasing from a small diameter portion toward a downstream side of the discharge passage.

Therefore, the deterioration of the efficiency of the pump can be prevented or reduced.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates a configuration of a hydraulic system to which a pump apparatus according to a first embodiment is applied.

FIG. 2 schematically illustrates a configuration of the pump apparatus according to the first embodiment.

FIG. 3 illustrates a partial cross section acquired by cutting a pump housing according to the first embodiment along a plane perpendicular to a central axis of a diving shaft.

FIG. 4 illustrates a cross section as viewed from a line A-A illustrated in FIG. 3.

FIG. 5 illustrates a venturi forming block according to the first embodiment as viewed from one side in an axial direction.

An upper diagram of FIG. 6 schematically illustrates a discharge passage around a venturi portion according to the first embodiment. A lower diagram of FIG. 6 illustrates a change in a pressure that is associated with each portion illustrated in the upper diagram.

An upper diagram of FIG. 7 schematically illustrates a discharge passage around an orifice according to a comparative example. A lower diagram of FIG. 7 illustrates a change in a pressure that is associated with each portion illustrated in the upper diagram.

FIG. 8 is a graph indicating a relationship between a flow amount and a differential pressure according to the first embodiment. A solid line indicates the first embodiment, and an alternate long and short dash line indicates the comparative example.

FIG. 9 illustrates a relationship between a narrower angle and a pressure loss rate according to the first embodiment.

An upper diagram of FIG. 10 schematically illustrates a discharge passage in which a large diameter portion is provided upstream of the venturi portion according to the first embodiment. A lower diagram of FIG. 10 illustrates a change in a pressure that is associated with each portion illustrated in the upper diagram.

An upper diagram of FIG. 11 schematically illustrates a discharge passage including a stepped portion (a rear portion) on a downstream side of an inner diameter gradually-increasing portion according to the first embodiment. A lower diagram of FIG. 11 illustrates a change in a pressure that is associated with each portion illustrated in the upper diagram.

FIG. 12 illustrates a relationship between L/L0, which is a ratio of L to L0 illustrated in FIG. 11, and the pressure loss rate.

FIG. 13 illustrates a cross section acquired by cutting a venturi forming block according to a second embodiment along a plane passing through a central axis of the venturi portion.

FIG. 14 illustrates a pump housing according to a fourth embodiment as viewed from a direction in which the central axis of the driving shaft extends.

FIG. 15 illustrates a cross section as viewed from a line B-B illustrated in FIG. 14.

FIG. 16 schematically illustrates a configuration of a pump apparatus according to a sixth embodiment.

FIG. 17 illustrates a partial cross section acquired by cutting a pump housing according to the sixth embodiment along a plane including the central axis of the driving shaft.

DESCRIPTION OF EMBODIMENTS

In the following description, embodiments for implementing a pump apparatus according to the present invention will be described based on exemplary embodiments illustrated in the drawings.

First Embodiment

First, a configuration will be described. FIG. 1 illustrates a configuration of a hydraulic system to which a pump apparatus 1 is applied. The pump apparatus 1 is mounted on a vehicle of an automobile. The pump apparatus 1 is a hydraulic fluid supply source that supplies hydraulic fluid to another apparatus mounted on the vehicle (an apparatus mounted on a vehicle). The apparatus mounted on the vehicle to which the pump apparatus 1 supplies the hydraulic fluid is an automatic transmission. The automatic transmission is a stepless transmission, in particular, a belt-type continuously variable transmission (hereinafter referred to as a CVT) 10. The hydraulic fluid is ATF (automatic transmission fluid). The pump apparatus 1 is driven by an internal-combustion engine as a prime mover thereof, and introduces and discharges the hydraulic fluid from and into an oil pan 100. For example, an oil pan of the CVT 10 can be used as the oil pan 100. Various types of valves controlled by a CVT control unit are provided in a control valve of the CVT 10. The hydraulic fluid discharged from the pump apparatus 1 is supplied to each unit (a primary pulley, a secondary pulley, a forward clutch, a reverse brake, a torque converter, a lubricant/cooling system, and the like) of the CVT 10 via the control valve.

The pump apparatus 1 includes a pump housing 2, a pump element 4, a venturi portion 50, and a control valve 8. The pump housing 2 contains the pump element 4, the control valve 8, and the venturi portion 50 therein. An intake passage 3, a discharge passage 5, a high pressure passage 6, an intermediate pressure passage 7, and a return passage 9 are provided in the pump housing 2 as passages through which the hydraulic fluid flows. The intake passage 3 connects the oil pan 100 and the pump element 4 to each other. The discharge passage 5 connects the pump element 4 and the CVT 10 to each other. The venturi portion 50 is a constriction portion provided on the way along the discharge passage 5. The high pressure passage 6 connects one side of the discharge passage 5 that is closer to the pump element 4 than the venturi portion 50 is (hereinafter referred to as an upstream side) and the control valve 8 to each other. The intermediate pressure passage 7 connects the venturi portion 50 and the control valve 8 to each other. The return passage 9 connects the control valve 8 and the intake passage 3 (the oil pan 100) to each other. A driving shaft 40 is pivotally supported in the pump housing 2. The driving shaft 40 is driven by a crank shaft of the internal-combustion engine. The pump element 4 is rotationally driven by the driving shaft 40. The pump element 4 introduces the hydraulic fluid therein from the oil pan 100 via the intake passage 3. The pump element 4 discharges the hydraulic fluid to the discharge passage 5, and supplies the hydraulic fluid to the CVT 10 via the discharge passage 5. A relatively high pressure (hereinafter referred to as a high pressure) on the upstream side of the venturi portion 50 is fed into the control valve 8 via the high pressure passage 6. Further, a relatively low pressure (a pressure around an intermediate level, hereinafter referred to as an intermediate pressure) in the venturi portion 50 is fed into the control valve 8 via the intermediate pressure passage 7. The control valve 8 switches a flow passage of the hydraulic fluid based on a difference (a differential pressure) between the pressure on the upstream side of the venturi portion 50 and the pressure in the venturi portion 50. By this switching, the control valve 8 controls a flow amount of the hydraulic fluid that the pump element 4 supplies to the CVT 10.

FIG. 2 schematically illustrates a configuration of the pump apparatus 1. FIG. 2 illustrates a cross section acquired by cutting the pump element 4 in a state extracted from the pump housing 2 along a plane perpendicular to a center axis (a rotational axis) O of the driving shaft 40. FIG. 2 illustrates a partial cross section acquired by cutting the control valve 8 along a plane passing through a central axis thereof. FIG. 2 schematically illustrates each of the passages 3 and the like. A direction in which the hydraulic fluid flows is indicated by an arrowed alternate long and short dash line. FIG. 3 illustrates a partial cross section acquired by cutting the pump housing 2 along the plane perpendicular to the central axis O. FIG. 4 illustrates a cross section as viewed from a line A-A illustrated in FIG. 3. Hereinafter, an orthogonal coordinate system is set for convenience of the description. An x axis is set to a horizontal direction in FIG. 3, and a positive side thereof is set to a right side in FIG. 3. A y axis is set to a vertical direction in the sheet of FIG. 3, and a positive side thereof is set to an upper side. A z axis is set to a direction perpendicular to the sheet of FIG. 3, and a positive side thereof is set to a front side of the sheet. The driving shaft 40 (the central axis O) extends in the z-axis direction. The pump housing 2 includes a pump housing main body 20 and a venturi forming block 21. The pump housing main body 20 is made from a metallic material. An intake port 230 and a discharge port 231 are formed at the pump housing main body 20, besides each of the above-described passages 3 and the like. The venturi forming block 21 is made from a resin material. The venturi forming block 21 is a member separate from the pump housing main body 20.

The pump housing main body 20 includes a rear body 22, a side plate 23, and a front body. A containing recessed portion 220, a first hole 221, a second hole 222, a third hole 223, a fourth hole 224, a fifth hole 225, a discharge pressure chamber 226, a valve containing hole 227, a venturi forming block containing hole 228, and a bearing holding hole are formed at the rear body 22. The containing recessed portion 220 has a bottomed cylindrical shape. The containing recessed portion 220 extends in the z-axis direction and is opened on a positive side of the rear body 22 in the z-axis direction. Semi-cylindrical first and second groove portions (not illustrated) are formed on an inner peripheral surface of the containing recessed portion 220 so as to extend in the z-axis direction. The second groove portion is provided on an opposite side of a central axis of the containing recessed portion 220 from the first groove portion. The bearing holding hole (not illustrated) has a bottomed cylindrical shape. The bearing holding hole extends in the z-axis direction and is opened to a bottom portion of the containing recessed portion 220 on the negative side in the z-axis direction. A bearing is mounted on an inner periphery of the bearing holding hole. An end of the driving shaft 40 on the negative side in the z-axis direction is inserted on an inner peripheral side of the bearing and is rotatably mounted. The discharge pressure chamber 226 is a bottomed recessed portion provided at the above-described bottom portion of the containing recessed portion 220, and is opened to the above-described bottom portion.

The first hole 221 extends in the y-axis direction on a negative side of the rear body 22 in the x-axis direction and a negative side of the rear body 22 in the z-axis direction. An opening of the first hole 22 on a negative side of the rear body 22 in the y-axis direction is sealingly closed by a plug member 221a. The first hole 221 is formed so as to partially overlap the discharge pressure chamber 226 as viewed from the y-axis direction and the z-axis direction, and is connected to the discharge pressure chamber 226. The valve containing hole 227 has a generally cylindrical shape, and extends in the x-axis direction on a positive side of the rear body 22 in the y-axis direction and a negative side of the rear body 22 in the z-axis direction. In other words, a longitudinal direction of the valve containing hole 227 (the x-axis direction) extends perpendicularly to a direction along the central axis O (the z-axis direction). An end of the valve containing hole 227 on the positive side in the x-axis direction is opened on an outer surface of the rear body 22. This opening is sealingly closed by a plug member 227a. An end of the valve containing hole 227 on the negative side in the x-axis direction is connected to an end of the first hole 221 on the positive side in the y-axis direction. One end of the fifth hole 225 is opened on a portion of the valve containing hole 227 that is closer to the negative side in the x-axis direction. The other end of the fifth hole 225 is opened on the outer surface of the rear body 22.

The venturi forming block containing hole 228 has a generally cylindrical shape, and extends in the x-axis direction on the negative side of the rear body 22 in the z-axis direction. In other words, a longitudinal direction of the venturi forming block containing hole 228 (the x-axis direction) extends generally in parallel with the longitudinal direction of the valve containing hole 227, and also extends perpendicularly to the direction along the central axis O (the z-axis direction). A negative side of the venturi forming block containing hole 228 in the x-axis direction is formed so as to intersect the first hole 221 and is connected to the first hole 221. Further, the negative side of the venturi forming block containing hole 228 in the x-axis direction is formed so as to partially overlap the discharge pressure chamber 226 as viewed from the y-axis direction and the z-axis direction, and is connected to the discharge pressure chamber 226. An end of the venturi forming block containing hole 228 on the negative side in the x-axis direction is opened on the outer surface of the rear body 22. This opening is sealingly closed by a plug member 228a. The second hole 222 is provided on a generally same central axis as the venturi forming block containing hole 228, and extends in the x-axis direction on a positive side of the rear body 22 in the x-axis direction and the negative side of the rear body 22 in the z-axis direction. An end of the second hole 222 on the negative side in the x-axis direction is connected to an end of the venturi forming block containing hole 228 on the positive side in the x-axis direction. An inner diameter of the second hole 222 is smaller than an inner diameter of the venturi forming block containing hole 228. The third hole 223 extends in the z-axis direction on the positive side of the rear body 22 in the x-axis direction and the negative side of the rear body 22 in the z-axis direction. An end of the third hole 223 on the positive side in the z-axis direction is connected to an end of the second hole 222 on the positive side in the x-axis direction. An end of the third hole 223 on the negative side in the z-axis direction is opened on the outer surface of the rear body 22. The fourth hole 224 connects a positive side of the valve containing hole 227 in the x-axis direction and a positive side of the venturi forming block containing hole 228 in the x-axis direction to each other.

The side plate 23 has a disk-like shape. A shaft containing hole (not illustrated) is provided at the side plate 23. The shaft containing hole penetrates through a central portion of the side plate 23. A pair of intake ports 230a and 230b and a pair of discharge ports 231a and 231b are provided on a surface of the side plate 23 on one side in an axial direction. The pair of intake ports 230a and 230b is grooves extending in a generally circular-arc manner in a direction around the shaft containing hole (hereinafter referred to as a circumferential direction), and is provided at positions opposite of the shaft containing hole from each other. The pair of discharge ports 231a and 231b is grooves extending in a generally circular-arc manner in the circumferential direction, and is provided at positions opposite of the shaft containing hole from each other. The intake ports 230 and the discharge ports 231 are arranged alternately in the circumferential direction. A communication passage (not illustrated) is provided at the side plate 23. The communication passage axially penetrates though the side plate 23 to establish communication between both side surfaces thereof. A first communication passage is opened to the intake port 230. A second communication passage is opened to the discharge port 231. The side plate 23 is installed in the containing recessed portion 220 of the rear body 22. A surface of the side plate 23 on the above-described one side faces an opening side of the containing recessed portion 220 (the positive side in the z-axis direction). A surface of the side plate 23 on the other side faces the bottom portion of the containing recessed portion 220. The shaft containing hole of the side plate 23 faces the bearing holding hole of the rear body 22. The first communication passage of the side plate 23 faces the bearing holding hole of the rear body 22. The first communication passage of the side plate 23 is connected to the intake passage 3 of the rear body 22. Each of the intake ports 230 is connected to the intake passage 3 via the first communication passage. The second communication passage of the side plate 23 is connected to the discharge pressure chamber 226 of the rear body 22. Each of the discharge ports 231 is connected to the discharge pressure chamber 226 via the second communication passage.

A front body (not illustrated) is a pump cover. The front body is fixed to the positive side of the rear body 22 in the z-axis direction so as to sealingly close the containing recessed portion 220. A bearing holding hole is provided at the front body 24. The bearing holding hole extends in the z-axis direction. A bearing is mounted on an inner periphery of the bearing holding hole. An end of the driving shaft 40 on the positive side in the z-axis direction is inserted on the inner peripheral side of the bearing, and is rotatably mounted.

The venturi forming block 21 has a generally cylindrical shape. A diameter (an outer diameter) of an outer peripheral surface of the venturi forming block 21 is approximately equal to a diameter (an inner diameter) of an inner peripheral surface of the venturi forming block containing hole 228. The venturi portion 50 is formed at the venturi forming block 21. The venturi portion 50 is a constriction portion formed at the venturi forming block 21 by molding. The venturi forming block 21 is joined to the pump housing main body 20 after the venturi portion 50 is formed. FIGS. 3 and 4 illustrate the cross section acquired by cutting the venturi forming block 21 along the plane passing through the axis line (the central axis) along a longitudinal direction of the venturi portion 50. FIG. 5 illustrates the venturi forming block 21 as viewed from a direction in which the central axis of the venturi portion 50 extends (from the negative side in the x-axis direction). Hereinafter, the direction in which the central axis of the venturi portion 50 extends will be referred to as an axial direction, and a direction around the central axis will be referred to as a circumferential direction. The venturi forming block 21 includes an inner diameter gradually-reducing portion 210, the venturi portion 50, a communication hole 213, a first communication groove 214, and a second communication groove 215. The venturi portion 50 includes a small diameter portion 51 and an inner diameter gradually-increasing portion 52.

The inner diameter gradually-reducing portion 210 is provided so as to extend in the axial direction toward an inner peripheral side of the venturi forming block 21, and is opened on an end surface of the venturi forming block 21 on one side in the axial direction. The inner diameter gradually-reducing portion 210 is a taper portion tapering from the one side in the axial direction toward the other side in the axial direction (a downstream side in the discharge passage 5), and is formed in such a manner that an inner diameter thereof gradually reduces toward the other side in the axial direction. An inner diameter of an end of the inner diameter gradually-reducing portion 210 on the one side in the axial direction is smaller than an inner diameter of the venturi forming block containing hole 228. The small diameter portion 51 is provided on the inner peripheral side of the venturi forming block 21, and extends in the axial direction. An end of the small diameter portion 51 on the one side in the axial direction is connected to an end of the inner diameter gradually-reducing portion 210 on the other side in the axial direction. An inner diameter of the small diameter portion 51 is approximately equal to an inner diameter of an end of the inner diameter gradually-reducing portion 210 on the other side in the axial direction, and is kept constant in the axial direction.

The inner diameter gradually-increasing portion 52 is provided so as to extend in the axial direction on the inner peripheral side of the venturi forming block 21. An end of the inner diameter gradually-increasing portion 52 on the one side in the axial direction is connected to an end of the small diameter portion 51 on the other side in the axial direction, and an end of the inner diameter gradually-increasing portion 52 on the other side in the axial direction is opened on an end surface of the venturi forming block 21 on the other side in the axial direction. The inner diameter gradually-increasing portion 52 is a taper portion tapering from the other side in the axial direction toward the one side in the axial direction (the upstream side of the discharge passage 5), and is formed in such a manner that an inner diameter thereof gradually increases from the one side in the axial direction toward the other side in the axial direction (the downstream side of the discharge passage 5). An inner diameter of the end of the inner diameter gradually-increasing portion 52 on the other side in the axial direction is slightly smaller than the inner diameter of the second hole 222. The venturi forming block 21 is formed in such a manner that a narrower angle e sandwiched between inner walls of the inner diameter-gradually increasing portion 52 (one of angles sandwiched between the inner walls as viewed from a direction perpendicular to the central axis of the venturi portion 50 that is equal to or smaller than 180 degree) is 60 degrees or smaller, in particular, approximately 15 degrees.

The communication hole 213 is a radial hole formed inside the venturi forming block 21 and extending in a radial direction of the venturi forming block 21. A plurality of (four) communication holes 213 are provided, and are arranged at approximately equal intervals to one another in the circumferential direction. Each of the communication holes 213 is provided at a position overlapping the small diameter portion 51 in the axial direction. A radially inner end of each of the communication holes 213 is opened to the small diameter portion 51. The first communication groove 214 is a circumferential groove formed on an outer peripheral surface of the venturi forming block 21 and extending in the circumferential direction. The first communication groove 214 is provided at a position overlapping the small diameter portion 51 and the communication hole 213 in the axial direction. A radially outer end of each of the communication holes 213 is opened to the first communication groove 214 (a bottom portion thereof). The second communication groove 215 is an axial groove formed on the outer peripheral surface of the venturi forming block 21 and extending in the axial direction. An end of the second communication groove 215 on the one side in the axial direction is connected to the first communication groove 214. An end of the second communication groove 215 on the other side in the axial direction is positioned close to the end surface of the venturi forming block 21 on the other side in the axial direction.

The venturi forming block 21 is joined to the pump housing main body 20 (the venturi forming block containing hole 228 of the rear body 22) as illustrated in FIGS. 3 and 4 after the venturi portion 50 is formed. The central axis of the venturi forming block 21 (the venturi portion 50) extends in the x-axis direction. The above-described one side of the venturi forming block 21 in the axial direction corresponds to the negative side in the x-axis direction, and the above-described other side of the venturi forming block 21 in the axial direction corresponds to the positive side in the x-axis direction. The end surface of the venturi forming block 21 on the other side in the axial direction (on which the inner diameter gradually-increasing portion 52 is opened) is in abutment with the end surface of the venturi forming block containing hole 228 on the positive side in the x-axis direction (on which the second hole 222 is opened). The end of the second communication groove 215 in the venturi forming block 21 on the above-described other side in the axial direction is connected to an opening of the fourth hole 224 in the venturi forming block containing hole 228. A third communication groove connected to the end of the second communication groove 215 on the other side in the axial direction and also extending in the circumferential direction may be provided at a position in the axial direction that radially faces the opening of the fourth hole 224 on the outer peripheral surface of the venturi forming block 21. In this case, the end of the second communication groove 215 on the other side in the axial direction and the opening of the fourth hole 224 are connected to each other via the third communication groove, which eliminates a necessity of adjusting a position of the venturi forming block 21 in a rotational direction around the central axis of the venturi forming block containing hole 228.

The pump element 4 is contained in a space surrounded by the inner periphery of the containing recessed portion 220 in the rear body 22, the surface of the side plate 23 on the positive side in the z-axis direction, and the surface of the front body on the negative side in the z-axis direction. In other words, the above-described space functions as a pump element containing portion. The driving shaft 40 is mounted in the above-described space, and the pump element 4 forms a plurality of pump chambers 400 around the driving shaft 40. As illustrated in FIG. 2, the pump element 4 is a vane pump-type pump, and includes a set of a rotor 41 and vanes 42. The rotor 41 is provided in the pump element containing portion, and is coupled with the driving shaft 40 by serration coupling. The rotor 41 is rotationally driven by the driving shaft 40, and rotates according to a rotation of the driving shaft 40. A plurality of (ten) slits 410 (radially extending grooves) is each radially provided at the rotor 41. The slits 410 are each opened on an outer peripheral surface of the rotor 41. The plurality of slits 410 are provided at approximately equal intervals in a circumferential direction of the rotor 41. The vane 42 is set in each of the slits 410. The vane 42 is a generally rectangular plate member (a vane). The vane 42 is provided so as to be able to project from the slit 410 and retract into the slit 410 (provided in a projectable and retractable manner).

A cam ring 43 has an annular shape. An outer periphery of the cam ring 43 is fitted in the inner periphery of the containing recessed portion 220. A center (a central axis) of the cam ring 43 approximately coincides with the central axis O. An inner peripheral surface of the cam ring 43 has a cylindrical shape extending in the z-axis direction, and is generally ecliptic as viewed from the z-axis direction. Semi-cylindrical first and second groove portions 431 and 432 are provided on an outer peripheral surface of the cam ring 43. The second groove portion 432 is provided on an opposite side of the central axis O of the cam ring 43 from the first groove portion 431. A first pin 451 is mounted by being fitted between the above-described first groove portion of the containing recessed portion 220 and the first groove portion 431 of the cam ring 43. A second pin 452 is mounted by being fitted between the above-described second groove portion of the containing recessed portion 220 and the second groove portion 432 of the cam ring 43. Each of the pins 451 and 452 is fixed to the pump housing main body 20. The pints 451 and 452 prevent or reduce a rotation of the cam ring 43 relative to the pump housing 2. The cam ring 43 is disposed around the rotor 41 in the pump element containing portion. The cam ring 43 forms the plurality of pump chambers 400 together with the rotor 41 and the vanes 42. In other words, the side plate 23 and the front body 24 are disposed on side surfaces of the cam ring 43 and the rotor 41 in the axial direction. A space between an inner peripheral surface of the cam ring 43 and an outer peripheral surface of the rotor 41 is sealingly closed by the side plate 23 and the front body 24 on the both sides thereof in the axial direction, while being divided into the plurality of (ten) pump chambers (volume chambers) 400 by the plurality of vanes 42.

For convenience of the description, an X axis and a Y axis are set to a long-axis direction and a short-axis direction of the generally ecliptic inner peripheral surface of the cam ring 43, respectively, as illustrated in FIG. 2. The rotor 41 rotates in a counterclockwise direction in FIG. 2. A radial distance between the outer peripheral surface of the rotor 41 and the inner peripheral surface of the cam ring 43 (a radial dimension of the pump chamber 400) increases as approaching the negative side in the X-axis direction from the central axis O of the cam ring 43, or approaching the positive side in the X-axis direction from the central axis O. The vane 42 projects from the slit 410 according to this change in the distance, by which each of the pump chambers 400 is defined. A volume of the pump chamber 400 increases as approaching the negative side in the X-axis direction from the central axis O or approaching the positive side in the X-axis direction from the central axis O. Due to this difference in the volume of the pump chamber 400, the volume of the pump chamber 400 reduces on the positive side in the X-axis direction with respect to the central axis O while increasing on the negative side in the X-axis direction with respect to the central axis O, as the rotor 41 rotates (as the pump chamber 400 travels toward the negative side in the x-axis direction) on the positive side in the Y-axis direction with respect to the central axis O. The volume of the pump chamber 400 reduces on the negative side in the X-axis direction with respect to the central axis O while increasing on the positive side in the X-axis direction with respect to the central axis O, as the rotor 41 rotates (the pump chamber 400 travel toward the positive side in the X-axis direction) on the negative side in the Y-axis direction with respect to the central axis O.

In this manner, the pump chamber 400 periodically expands and contracts while rotating in the counterclockwise direction around the central axis O. The intake port 230 is opened to a region on the negative side in the X-axis direction and the positive side in the Y-axis direction, and a region on the positive side in the X-axis direction and the negative side in the Y-axis direction. In other words, the intake port 230 is opened to an intake region where the volume of the pump chamber 400 increases according to the rotation of the driving shaft 40 (i.e., an intake region where the pump chamber 400 increasing in volume according to the rotation of the driving shaft 40 among the plurality of pump chambers 400 is located). The discharge port 231 is opened to a region on the positive side in the X-axis direction and the positive side in the Y-axis direction, and a region on the negative side in the X-axis direction and the negative side in the Y-axis direction. In other words, the discharge port 231 is opened to a discharge region where the volume of the pump chamber 400 reduces according to the rotation of the driving shaft 40 (i.e., a discharge region where the pump chamber 400 reducing in volume according to the rotation of the driving shaft 40 among the plurality of pump chambers 400 is located). The pump chamber 400 introduces the hydraulic fluid therein from the intake port 230 in the intake region, and discharges the (above-described introduced) hydraulic fluid into the discharge port 231 in the discharge region. The intake and the discharge are each carried out twice per rotation of the driving shaft 40 in correspondence with the pair of intake ports 230a and 230b and the pair of discharge ports 231a and 231b. The hydraulic fluid in both the discharge ports 231 are collected into one portion. The cam ring 43 is provided immovably in the pump element containing portion. In other words, the pump element 4 is a fixed displacement pump that discharges a constant amount as a discharge amount per rotation of the driving shaft 40 (hereinafter referred to as a pump capacity). The pump element 4 may be a set of trochoidal pump-type inner and outer rotors or may be another type of pump.

The control valve 8 is a spool valve body and is contained in the valve containing hole 227. The control valve 8 is displaceable (capable of performing a stroke) in the x-axis direction in the valve containing hole 227. The control valve 8 includes a first land portion 81, a second land portion 82, a connection portion 83, a spacer portion 84, and a recessed portion 85. Each of the land portions 81 and 82 is cylindrical, and diameters thereof are approximately equal to each other. A diameter of an outer peripheral surface of each of the land portions 81 and 82 is slightly smaller than a diameter of an inner peripheral surface of the valve containing hole 227. In the control valve 8, the first land portion 81 is provided on the negative side in the x-axis direction and the second land portion 82 is provided at an end on the positive side in the x-axis direction. A circumferential groove 810 extending in a direction around the central axis of the control valve 8 (hereinafter referred to as a circumferential direction) is provided on an outer peripheral surface of the first land portion 81. A plurality of circumferential grooves 820 extending in the circumferential direction is provided on an outer peripheral surface of the second land portion 82. The connection portion 83 has a cylindrical shape sandwiched between both the land portions 81 and 82 and extending in the x-axis direction. A diameter of the outer peripheral surface of the connection portion 83 is smaller than each of the land portions 81 and 82. The spacer portion 84 has a rod shape extending from the first land portion 81 toward the negative side in the x-axis direction. The recessed portion 85 has a bottomed cylindrical shape and extends in the x-axis direction inside the second land portion 82. The recessed portion 85 is opened on an end surface of the second land portion 82 on the positive side in the x-axis direction.

A high pressure chamber 86 is defined inside the valve containing hole 227 by being surrounded by an end surface of the first land portion 81 on the negative side in the x-axis direction and the inner peripheral surface of the valve containing hole 227. An intermediate pressure chamber 88 is defined by being surrounded by an end surface of the second land portion 82 on the positive side in the x-axis direction, the inner peripheral surface of the valve containing hole 227, and an end surface of the plug member 227a on the negative side in the x-axis direction. A drain chamber 89 is defined on an outer periphery of the connection portion 83 between the first land portion 81 and the second land portion 82. A spring 88 is mounted in the intermediate pressure chamber 88. The spring 88 is a coil spring. An end of the spring 88 on the positive side in the x-axis direction is held by the plug member 227a. A negative side of the spring 88 in the x-axis direction is held inside the recessed portion 85 of the control valve 8. The spring 88 is mounted in a compressed state. The spring 88 is a return spring constantly biasing the control valve 8 toward the negative side in the x-axis direction. A displacement of the control valve 8 in the valve containing hole 227 toward the negative side in the x-axis direction is regulated by abutment of an end of the spacer portion 84 on the negative side in the x-axis direction with an end surface of the valve containing hole 227 on the negative side in the x-axis direction. The first hole 221 is opened to the high pressure chamber 86 and the fourth hole 224 is opened to the intermediate pressure chamber 88, regardless of the displacement of the control valve 8 in the valve containing hole 227.

Next, a configuration of the plurality of passages 3 and the like will be described. Each of the discharge ports 231 of the side plate 23 is in communication with the first hole 221 or the venturi forming block containing hole 228 via the discharge pressure chamber 226 of the rear body 22. A portion where the discharge pressure chamber 226 and the first hole 221 or the venturi forming block containing hole 228 are connected to each other, a negative side of the venturi forming block containing hole 228 in the x-axis direction with respect to the venturi forming block 21 (the inner diameter gradually-reducing portion 210), and the inner diameter gradually-reducing portion 210 function as the discharge passage 5 from the discharge port 231 (the discharge pressure chamber 226) to the venturi portion 50 (the small diameter portion 51 and the inner diameter gradually-increasing portion 52), i.e., the discharge passage 5 on the upstream side of the venturi portion 50. The small diameter portion 51 is formed in such a manner that the inner diameter thereof is smaller than an inner diameter of the above-described discharge passage 5. The inner diameter gradually-increasing portion 52 of the venturi portion 50 is in communication with outside the rear body 22 via the second hole 222 and the third hole 223. The second hole 222 and the third hole 223 function as the discharge passage 5 extending from the venturi portion 50 toward the CVT 10, i.e., the discharge passage 5 on the downstream side of the venturi portion 50. An inner diameter of the above-described discharge passage 5 is larger than an inner diameter of an end of the inner diameter gradually-increasing portion 52 on the positive side in the x-axis direction. A portion between portions of the first hole 221 that are connected to (intersects) the venturi forming block containing hole 228 and the valve containing hole 227, respectively, functions as the high pressure passage 6 branching off from the discharge passage 5 on the upstream side of the venturi portion 50 and is connected to the high pressure chamber 86 of the control valve 8. The communication hole 213, the first communication groove 214, and the second communication groove 215 of the venturi forming block 21, and the fourth hole 224 of the rear body 22 function as the intermediate pressure passage 7 (a venturi portion pressure introduction passage) branching off from the venturi portion 50 (the small diameter portion 51) in the discharge passage 5 and is connected to the intermediate pressure chamber 88 of the control valve 8. The communication hole 213 functions as a venturi portion pressure introduction hole. The fifth hole 225 of the rear body 22 functions as the return passage 9 extending from the drain chamber 89 of the control valve 8 toward the oil pan 100.

As illustrated in FIGS. 3 and 4, the longitudinal direction of the venturi portion 50 (the x-axis direction) extends generally perpendicularly to the direction in which the central axis O of the driving shaft 40 extends (the z-axis direction), and also extends generally in parallel with the longitudinal direction of the control valve 8 (the x-axis direction). The venturi portion 50 is disposed in such a manner that the upstream side thereof faces the high pressure chamber 86 of the control valve 8. In other words, the discharge passage 5 on the upstream side of the venturi portion 50 and the high pressure chamber 86 at least partially overlap each other in the x-axis direction. More specifically, the negative side of the venturi forming block containing hole 228 in the x-axis direction with respect to the venturi forming block 21, and the high pressure chamber 86 (when the control valve 8 is maximally displaced toward the negative side in the x-axis direction) at least partially overlap each other as viewed from the y-axis direction.

[Functions]

Next, functions and effects will be described. An upper diagram of FIG. 6 schematically illustrates the discharge passage 5 around the venturi portion 50. An arrow indicates the direction in which the hydraulic fluid flows. It is defined that u₁ and p₁ represent a flow speed and a pressure of the hydraulic fluid in the discharge passage 5 on the upstream side of the venturi portion 50, respectively. It is defined that u₂ and p₂ represent a flow speed and a pressure at the small diameter portion 51. It is defined that u₃ and p₃ represent a flow speed and a pressure in the discharge passage 5 on the downstream side of the venturi portion 50, respectively. A lower diagram of FIG. 6 illustrates a change in the pressure P that is associated with each of the portions illustrated in the upper diagram. The inner diameter (a cross-sectional area) of the small diameter portion 51 is smaller than the inner diameter (a cross-sectional area) of the discharge passage 5 on the upstream side of the venturi portion 50. Therefore, u₂ is higher than u₁. This increase in the flow speed is proportional to the flow amount and inversely proportional to a difference in the cross-sectional area. The pressure reduces in a quadratic function manner according to the increase in the flow speed based on Bernoulli's principle. Therefore, p₂ is lower than p₁. This reduction in the pressure corresponds to the increase in the flow speed, i.e., the flow amount. In this manner, a differential pressure Δp=p₁−p₂ is generated according to the flow amount at the venturi portion 50 (the small diameter portion 51) as the constriction portion. The inner diameter of the inner diameter gradually-increasing portion 52 gradually increases at the venturi portion 50 as approaching the downstream side. Therefore, the flow speed at the inner diameter gradually-increasing portion 52 gradually reduces as approaching the downstream side. Since the reduction in the flow speed is gentle, energy is not lost so much. Therefore, the pressure in the inner diameter gradually-increasing portion 52 gradually increases as the hydraulic fluid flows toward the downstream side, according to the reduction in the flow speed. If the inner diameter on the downstream side at the venturi portion 50 increases to around the inner diameter of the discharge passage 5 on the upstream side of the venturi portion 50, the flow speed reduces to around u₁, and the pressure increases (recovers) to around p₁. Since the inner diameter of the constriction portion on the downstream side (the inner diameter gradually-increasing portion 52) gently increases in this manner, a large loss of energy is prevented or cut down. Therefore, on the downstream side of the constriction portion, the flow speed reduces to a similar level to the upstream side of the constriction portion, and the pressure also recovers to a similar level to the upstream side of the constriction portion.

The hydraulic fluid (p₁) on the upstream side of the venturi portion 50 is introduced into the high pressure chamber 86 via the high pressure passage 6. The hydraulic fluid (p₂) in the venturi portion 50 (the small diameter portion 51) is introduced into the intermediate pressure chamber 88 via the intermediate pressure passage 7. The drain chamber 89 is kept at the low pressure (is opened to an atmospheric pressure similarly to the intake passage 3). A force F1 toward the positive side in the x-axis direction due to pi in the high pressure chamber 86 and a force F2 toward the negative side in the x-axis direction due to p₂ in the intermediate pressure chamber 88 are applied to the control valve 8. Further, a force F3 toward the negative side in the x-axis direction due to the spring 88 is applied to the control valve 8. When the difference between F1 and F2, F1−F2 (the force corresponding to the differential pressure Δp) exceeds F3, the control valve 8 is displaced toward the positive side in the x-axis direction. When the high pressure chamber 86 and the return passage 9 are brought into communication with each other due to this displacement, the hydraulic fluid introduced from the discharge passage 5 on the upstream side of the venturi portion 50 to the high pressure passage 6 (the high pressure chamber 86) starts to be returned to the intake passage 3 (one side where the intake ports 230 are located) via the return passage 9. In other words, the control valve 8 switches the flow passage in such a manner that the hydraulic fluid is returned toward the intake side based on the differential pressure Δp between the upstream side of the venturi portion 50 and the small diameter portion 51. When the hydraulic fluid starts to be returned toward the intake side, the flow amount to be supplied to the CVT 10 via the discharge passage 5 is limited to a required amount. In this manner, the venturi portion 50, the high pressure passage 6, the intermediate pressure chamber 7, the control valve 8, and the return passage 9 function as a controller that controls the discharge flow amount of the pump element 4.

In the conventional pump apparatus, the orifice has been used as a means for generating the differential pressure. The orifice can be formed with, for example, such a simple structure that only a constriction of a thin plate is provided in the flow passage. The pressure difference is generated according to the flow amount between the upstream side and the downstream side of the orifice. However, the orifice leads to a turbulence of the flow at an exit of the constriction, thereby resulting in a loss of the energy and thus a reduction in the pressure on the downstream side of the orifice. The lost energy undesirably spreads outward by being converted into heat, noise, and the like. Therefore, the efficiency of the pump undesirably reduces. As the differential pressure is further increasing, the efficiency of the pump is reducing. Hereinafter, a pump apparatus similar to the present exemplary embodiment that uses an orifice 500 instead of the venturi portion 50 will be referred to as a comparative example. A narrower angle θ at an exit of the orifice 500 is 120 to 180 degrees. FIG. 7 is a similar diagram to FIG. 6 that illustrates the comparative example. An upper diagram of FIG. 7 illustrates the discharge passage 5 around the orifice 500. It is defined that u₁ and p₁ represent the flow speed and the pressure of the hydraulic fluid in the discharge passage 5 on the upstream side of the orifice 500, respectively. It is defined that u₂ and p₂ represent the flow speed and the pressure in the discharge passage 5 on the downstream side of the orifice 500, respectively. An inner diameter of the orifice 500 is smaller than the inner diameter of the discharge passage 5 on the upstream side of the orifice 500. Therefore, the flow speed at the orifice 500 is higher than and the pressure at the orifice 500 is lower than p₁. An inner diameter of the exit of the orifice 500 suddenly increases as approaching the downstream side. Therefore, an eddy current occurs at the exit of the orifice 500, and the energy is significantly lost. Therefore, although u₂ reduces to u₁, p₂ does not increase (recover) to p₁. In other words, the pressure undesirably reduces (a pressure loss). The conventional pump apparatus results in supply of the pressure p₂ to the CTV 10 after the pressure reduces in this manner.

On the other hand, the pump apparatus 1 according to the present embodiment uses a venturi tube instead of the orifice as method means for generating the differential pressure. The venturi portion 50 has the gently increasing inner diameter on the downstream side (the inner diameter gradually-increasing portion 52) of the constriction portion, thereby preventing or cutting down the significant loss of the energy. Therefore, the pressure recovers according to the reduction in the flow speed. In other words, the pressure loss at a differential pressure generation means is prevented or cut down. Therefore, the present embodiment can generate the differential pressure while preventing or reducing the deterioration of the efficiency of the pump. Especially, the automatic transmission such as the stepless transmission uses a larger flow amount compared to a power steering apparatus and the like, and therefore can acquire a considerable effect of preventing or cutting down the pressure loss. An entrance at the constriction portion at the venturi portion 50 (the upstream side of the small diameter portion 51) is also formed in such a manner that the dimeter of the inner diameter gradually-reducing portion 210 gently reduces, which can prevent or reduce the occurrence of the turbulence of the flow. As a result, the energy is not lost significantly, and the pressure reduces according to the increase in the flow speed. Therefore, the present embodiment can further efficiently reduce the pressure (can prevent or cut down the pressure loss as a whole). Therefore, the present embodiment can further improve the efficiency of the pump.

In the comparative example, an attempt to cut down the energy loss at the orifice 500 to prevent or reduce the deterioration of the efficiency of the pump leads to an unintentional reduction in the differential pressure (the force F1−F2 corresponding thereto). Activating the control valve 8 with the small Δp leads to an unstable behavior of the control valve 8. As a result, a wide variation undesirably occurs in the discharge flow amount of the pump element 4 targeted for the control (hereinafter referred to as a control flow amount). On the other hand, the present embodiment can increase the differential pressure (the force F1−F2 corresponding thereto) while preventing or reducing the deterioration of the efficiency of the pump. Therefore, the present embodiment can also prevent or reduce the above-described variation in the control flow amount. FIG. 8 is a graph indicating a relationship between the discharge flow amount (the flow amount passing through the differential pressure generation means) Q of the pump element 4, and the difference Δp between the pressures applied to the both sides of the control valve 8 in the axial direction (the differential pressure generated at the differential pressure generation means). Supposing that the efficiency of the pump (the pressure loss at the differential pressure generation means) is the same between the present embodiment and the comparative example, a characteristic of the present embodiment is indicated by a solid line, and a characteristic of the comparative example is indicated by an alternate long and short dash line. According to Q, Δp changes in a quadratic curve manner. The activation (displacement) of the control valve 84 is controlled according to Δp, i.e., Q. A change rate of Δp to Q is higher in the present embodiment than in the comparative example. Q required to generate the same level of Δp is smaller in the present embodiment than in the comparative example. In other words, a larger pressure of Δp (the force F1−F2 corresponding thereto) can be generated in the present embodiment than in the comparative example even if Q is the same therebetween. Therefore, the present embodiment can stabilize the behavior of the control valve 8, and prevent or reduce the variation in the control flow amount.

Further, a load from outside (an external force) may be applied to the control valve 8 besides F1 to F3. In this case, the control flow amount may deviate from an originally intended amount. For example, there is a relatively large amount of contamination in the hydraulic fluid under a use environment in the automatic transmission (the CVT 10). If a load is generated on the control valve 8 due to, for example, the presence of the contamination in a gap between the outer peripheral surface of the control valve 8 and the inner peripheral surface of the valve containing hole 227, this makes the control valve 8 less movable, thereby undesirably causing the deviation of the control flow amount from the originally intended amount by a flow amount corresponding to this load. On the other hand, in the present embodiment, the differential pressure Δp (the force F1−F2 corresponding thereto) can be considerably changed with a small change in the flow amount Q. Therefore, the deviation of the control amount can be reduced. In FIG. 8, it is defined that δp represents the above-described load converted into Δp, and δQ represents the deviation of Q corresponding to this δp. In other words, a predetermined amount of Q corresponds to an arbitrary pressure of Δp, and a deviation of the above-described arbitrary pressure of Δp by δp causes a deviation of Q from the above-described predetermined amount of Q by δQ. The change rate of Q to Δp is smaller in the present embodiment than in the comparative example. Therefore, δQ corresponding to the same deviation of δp is smaller in the present embodiment than in the comparative example (δQ₂<δQ₁). In other words, even when the same load is applied to the control valve 8, the flow amount is less changed in the present embodiment than in the comparative example. Therefore, the present embodiment can reduce the deviation of the control flow amount.

Then, it is also conceivable to increase a gap area of a clearance portion between the control valve 8 and the valve containing hole 227 around the control valve 8 to prevent a lock of the control valve 8 due to the contamination. However, the increase in the gap area of the clearance portion leads to an increase in a leak amount around the control valve 8 (via the clearance portion). This results in the undesirable deterioration of the efficiency of the pump. On the other hand, the present embodiment can generate a large differential pressure Δp with a relatively small flow amount Q while preventing or cutting down the energy loss at the constriction portion. Therefore, the diameter of the control valve 8 can be reduced without requiring a significant reduction in the force F1−F2 applied to the control valve 8. Reducing the diameter of the control valve 8 also allows a reduction in the gap area of the above-described clearance portion. As a result, the present embodiment reduces the leak amount around the control valve 8, thereby succeeding in preventing or reducing the deterioration of the pump efficiency.

The narrower angle e sandwiched between the inner walls of the inner diameter gradually-increasing portion 52 is an angle by which the exit flares at the venturi portion 50 as the constriction portion. Setting θ to 60 degrees or smaller can acquire a sufficient effect of preventing or cutting down the pressure loss. FIG. 9 illustrates a relationship between θ and a pressure loss rate. The pressure loss rate is a rate when the pressure rate in the comparative example is defined to be 1. When θ is 60 degrees or smaller, the pressure loss rate falls below 1. In other words, the pressure loss is smaller than the comparative example. In the present embodiment, the venturi portion 50 (the inner diameter gradually-increasing portion 52) is formed in such a manner that θ becomes 60 degrees or smaller. Therefore, the pressure loss is prevented or cut down more than in the comparative example. Therefore, the present embodiment can further reliably prevent or reduce the deterioration of the pump efficiency. For example, by setting θ to approximately 15 degrees, the present embodiment can prevent or cut down an excessive increase in the length of the venturi portion 50 in the longitudinal direction (a dimension in the axial direction) while acquiring a sufficiency effect of preventing or cutting down the pressure loss.

The space in the venturi forming block containing hole 228 on the negative side in the x-axis direction with respect to the venturi forming block 21 functions as the discharge passage 5 on the upstream side of the venturi portion 50. The second hole 222 functions as the discharge passage 5 on the downstream side of the venturi portion 50. The inner diameter of the venturi forming block containing hole 228 is larger than the inner diameter of the second hole 222. In other words, the above-described space in the discharge passage 5 on the upstream side of the venturi portion 50 is a large diameter portion 53 having a larger inner diameter than the downstream side (the second hole 222). The pressure in this large diameter portion 53 is introduced into the high pressure chamber 86 of the control valve 8 as the pressure on the upstream side of the venturi portion 50 (the high pressure). Therefore, FIG. 6 can be redrawn like FIG. 10. In FIG. 10, it is defined that u₁* and p₁* represent a flow speed and a pressure in the large diameter portion 53. The other symbols are similar to FIG. 6. If the inner diameter (the cross-sectional area) of the large diameter portion 53 is larger than the inner diameter (the cross-sectional area) of the discharge passage 5 on the upstream side of the large diameter portion 53, u₁* is lower than u₁ (≈u₃). According thereto, p₁* is higher than p₁ (≈p₃). The other characteristics are similar to FIG. 6. Therefore, defining that Δp* represents the differential pressure generated at the venturi portion 50 (the small diameter portion 51), Δp*(=p₁*−p₂)>Δp(=p₁−p₂) is satisfied, so that a larger differential pressure is generated than when the large diameter portion 53 is not provided (FIG. 6). As a result, the difference F1−F2 between the forces applied to the control valve 8 increases, so that the present embodiment can further effectively acquire the above-described functions and effects.

The inner diameter of the end of the inner diameter gradually-increasing portion 52 on the other end in the axial direction that is opened on the end surface of the venturi forming block 21 on the other side in the axial direction is slightly smaller than the inner diameter of the second hole 222. Therefore, FIG. 6 can be redrawn like FIG. 11. The inner diameter gradually-increasing portion 52 includes the taper portion on the upstream side that is formed so as to keep θ constant at 60 degrees or smaller (in particular, approximately 15 degrees), and a stepped portion on the downstream side that is formed so as to have θ larger than 60 degrees continuously from the discharge passage 5 on the downstream side of the venturi portion 50. Hereinafter, the above-described taper portion on the upstream side will be referred to as a front portion 520, and the above-described stepped portion on the downstream side will be referred to as a rear portion 521. The inner diameter gradually-increasing portion 52 includes the front portion 520 and the rear portion 521. In the present embodiment, θ of the rear portion 521 is approximately 180 degrees. In other words, the rear portion 521 flares as if extending generally perpendicularly to the inner walls of the discharge passage 5 on the downstream side of the venturi portion 50. Hypothetically supposing that the inner diameter gradually-increasing portion 52 is formed as far as the inner diameter thereof reaches the same diameter as the inner diameter of the discharge passage 5 on the downstream side of the venturi portion 50 with θ kept constant at 60 degrees or smaller, L0 is defined to represent a length of this (hypothetical) inner diameter gradually-increasing portion 52 in the longitudinal direction at this time. Then, L is defined to represent a length of the front portion 520 in the longitudinal direction.

FIG. 12 illustrates a relationship between L/L0, which is a ratio of L to L0, and the pressure loss rate. The pressure loss rate is a rate of a pressure loss when L/L0 is 0, i.e., a rate when the pressure loss in the comparative example is defined to 1. In a range where L/L0 is higher than 0 and equal to or lower than 0.65, the pressure loss rate reduces according to the increase in L/L0. In a range where L/L0 is higher than 0.65, the pressure loss rate does not reduce more than that even when L/L0 increases. Therefore, as long as a region of a certain length is ensured as the region where θ is 60 degrees or smaller (the front portion 520), the pressure loss can be more prevented or cut down than in the comparative example. However, even if the length L of the front portion 520 increases to longer than 65% of L0, this does not achieve the effect of preventing or cutting down the pressure loss more than that. Therefore, it is preferable to form the front portion 520 in such a manner that the L/L0 exceeds 0 and reaches or falls below 0.65, i.e., as far as a position where L reaches or falls below 65% of L0. In this case, the rear portion 521 where θ exceeds 60 degrees is provided on the downstream side of the front portion 520. Stopping keeping θ at 60 degrees or smaller at the rear portion 521 in this manner allows the venturi portion 50 to be formed continuously from the discharge passage 5 (the inner diameter of the venturi portion 50 to be returned to the initial diameter) on the downstream side, with a relatively short length (shorter than L0). As a result, the present embodiment can reduce the length of the venturi portion 50 in the longitudinal direction. The present embodiment can improve the above-described effect of reducing the length by allowing θ at the rear portion 521 to approach generally 180 degrees as illustrated in FIG. 11. In the range where L/L0 is higher than 0 and equal to or lower than 0.65, a reduction amount (a reduction rate) of the pressure loss rate with respect to the increase in L/L0 increases as L/L0 approaches 0. Then, in a range where L/L0 is 0.4 or higher, a sufficiently low pressure loss rate (sufficiently close to the pressure loss rate when L/L0 is 0.65) can be acquired. Therefore, it is preferable to form the front portion 520 in such a manner that L/L0 reaches or exceeds 0.4, i.e., as far as a position where L reaches or exceeds 40% of L0. In this case, the present embodiment can improve the above-described effect of reducing the length by allowing L to approach 40% of L0 while acquiring the sufficient effect of preventing or cutting down the pressure loss.

The venturi portion 50 is long compared to the orifice (the dimension in the axial direction is large). Therefore, processing thereof is comparatively difficult. On the other hand, in the present embodiment, the venturi portion 50 is formed in the venturi forming block 21. This venturi forming block 21 is joined to the pump housing main body 20.

As a result, the venturi portion 50 is realized inside the pump housing main body 20. In this manner, the present embodiment can improve workability of the venturi portion 50 by forming the venturi portion 50 in the venturi forming block 21 that is a separate member from the pump housing main body 20. The present embodiment can be realized by forming at least the small diameter portion 51 and the inner diameter gradually-increasing portion 52 constituting the venturi portion 50 in the venturi forming block 21. In other words, the constriction portion having the same diameter as the small diameter portion 51 and a predetermined length and the inner diameter gradually-reducing portion 210 may be provided on the pump housing main body 20 side, or may be provided on the venturi forming block 21 side. The venturi forming block 21 is made from the resin material. The venturi portion 50 including the inner diameter gradually-increasing portion 52 is formed by molding. Therefore, the inner diameter gradually-increasing portion 52 can be easily formed compared to forming the inner diameter gradually-increasing portion 52 by machining processing.

Further, the venturi portion 50 should have a long dimension (a large space in the longitudinal direction) compared to the orifice. On the other hand, in the present embodiment, the venturi portion 50 is disposed in such a manner that the longitudinal direction of the venturi portion 50 (the x-axis direction) and the direction of the rotational axis (the central axis O) of the driving shaft 40 (the z-axis direction) extend generally perpendicularly to each other.

Therefore, the present embodiment can prevent or cut down an increase in the dimension of the pump apparatus in the direction of the rotational axis of the driving shaft 40 (the axial direction). On the other hand, the pump housing 2 has a dimension enough to contain the control valve 8 therein from the beginning. Then, in the present embodiment, the venturi portion 50 is disposed in such a manner that the longitudinal direction of the venturi portion 50 and the longitudinal direction of the control valve 8 extend generally in parallel with each other. The venturi portion 50 is disposed so as to utilize the originally existing space extending in the longitudinal direction of the control valve 8 in this manner, so that the present embodiment can prevent or cut down the increase in a size of an outer shape of the pump apparatus (in the radial direction of the control valve 8).

Further, the venturi portion 50 is disposed in such a manner that the discharge passage 5 on the upstream side of the venturi portion 50 faces the high pressure chamber 86 of the control valve 8. Therefore, the present embodiment can shorten the high pressure passage 6 (the first hole 221) establishing the communication between the upstream side of the venturi portion 50 and the high pressure chamber 86. More specifically, both the venturi forming block containing hole 228 and the valve containing hole 227 extend in the x-axis direction and are disposed generally in parallel with each other. The first hole 221 extends linearly in the y-axis direction, and connects the negative side of the venturi forming block containing hole 228 in the x-axis direction with respect to the venturi forming block 21 and the high pressure chamber 86 in the valve containing hole 227 to each other, thereby connecting the upstream side of the venturi portion 50 and the high pressure chamber 86 with a shortest distance. The venturi portion 50 may be disposed in such a manner that the second communication groove 215 (at least a part thereof) in the venturi forming block 21 faces the intermediate pressure chamber 88 of the control valve 8. In this case, the present embodiment can shorten the intermediate pressure passage 7 (the fourth hole 224) establishing the communication between the second communication groove 215 and the intermediate pressure chamber 88.

The communication holes 213 of the venturi forming block 21 are opened on the inner peripheral surface of the venturi portion 50 on the radially inner side. The communication holes 213 are provided in the venturi portion 50, and function as openings for introducing the pressure in the venturi portion 50 into the control valve 8 (the intermediate pressure chamber 88). Then, due to presence of, for example, a bend or a curve in the discharge passage 5 on the upstream side of the venturi portion 50, this passage 5 may have unevenness in a flow speed distribution in a direction around the axis line along the longitudinal direction thereof(hereinafter referred to as a circumferential direction). This case also leads to occurrence of unevenness in a pressure distribution in the circumferential direction in the venturi portion 50. This unevenness undesirably varies depending on the flow amount and a temperature condition. On the other hand, in the present embodiment, the plurality of (four) openings is provided in the circumferential direction of the venturi portion 50 as the above-described openings of the communication holes 213. The pressure is extracted from a plurality of portions in the circumferential direction in the venturi portion 50 in this manner, which allows the pressure in the venturi portion 50 to be stably introduced into the intermediate pressure chamber 88 in spite of the above-described unevenness in the pressure distribution. In other words, the pressures (the hydraulic fluid) extracted from the above-described openings of the plurality of communication holes 213 are collected into the single intermediate pressure passage 7 (the fourth hole 224) via the first and second communication grooves 214 and 215, and then are introduced into the intermediate pressure chamber 88. At this time, the above-described uneven pressure distributions are canceled out by each other, which results in introduction of an average pressure in the circumferential direction in the venturi portion 50 into the intermediate pressure chamber 88. Therefore, the variation in the pressure extracted from inside the venturi portion 50 is reduced. Therefore, the activation of the control valve 8 is stabilized, and the deviation of the control flow amount is reduced. The number of communication holes 213 may be any number as long as this number is two or more. In the present embodiment, the above-described openings of the communication holes 213 are disposed at generally equal intervals in the circumferential direction, so that the present embodiment can further stably reduce the variation in the pressure extracted from inside the venturi portion 50.

The communication holes 213 are provided at the positions overlapping the small diameter portion 51 in the axial direction (the longitudinal direction) of the venturi portion 50. In other words, the above-described openings of the communication holes 213 are provided at the small diameter portion 51. Therefore, this configuration results in extraction of the pressure from a portion smallest in diameter in the venturi portion 50, i.e., a portion in the venturi portion 50 where the pressure is minimized, and introduction of this pressure into the intermediate pressure chamber 88. As a result, the present embodiment can most efficiently utilize the differential pressure generated in the venturi portion 50.

Second Embodiment

The pump apparatus 1 according to a second embodiment is different from the first embodiment in terms of the configuration of the venturi forming block 21. The second embodiment will be described below focusing on only configurations different from the first embodiment. Configurations shared with the first embodiment will be identified by the same reference numerals as the first embodiment, and descriptions thereof will be omitted. FIG. 13 illustrates a cross section acquired by cutting the venturi forming block 21 along a plane passing through the central axis of the venturi portion 50. The venturi forming block 21 is not provided with the inner diameter gradually-reducing portion 210 like the first embodiment. The small diameter portion 51 is opened on the end surface of the venturi forming block 21 on the one side in the axial direction (the outer surface of the venturi forming block 21). The communication hole 213 is provided at the position overlapping the one side of the inner diameter gradually-increasing portion 52 in the axial direction (the one side where the small diameter portion 51 is located). A radially inner end of the communication hole 213 is opened to the one side of the inner diameter gradually-increasing portion 52 in the axial direction (the one side where the small diameter portion 51 is located). The communication hole 213 forms a part of the intermediate pressure passage 7. The communication hole 213 introduces a pressure on the one side of the inner diameter gradually-increasing portion 52 in the axial direction (the one side where the small diameter portion 51 is located) among pressures in the venturi portion 50 into the intermediate pressure chamber 88 of the control valve 8.

Next, functions will be described. Like the present embodiment, the pressure in the venturi portion 50 that is introduced into the intermediate pressure chamber 88 may be not only the pressure in the small diameter portion 51 but also the pressure in the inner diameter gradually-increasing portion 52. The pressure on the one side of the inner diameter gradually-increasing portion 52 in the axial direction (the one side where the small diameter portion 51 is located) is introduced into the intermediate pressure chamber 88. Therefore, a lower pressure among the pressures in the inner diameter gradually-increasing portion 52 can be used. Therefore, the present embodiment allows a sufficiently large differential pressure to be applied to the control valve 8.

If the small diameter portion 51 is not opened on the outer surface of the venturi forming block 21 and is provided inside the venturi forming block 21, a mold would have to be inserted from the both sides of the venturi forming block 21 in the axial direction when the venturi portion 50 is formed by molding. When the venturi portion 50 is subjected to the machining processing, the machining processing would have to be performed from the both sides of the venturi forming block 21 in the axial direction. On the other hand, in the present embodiment, the small diameter portion 51 is opened on the outer surface of the venturi forming block 21. Therefore, when the venturi portion 50 is formed by molding, this can be achieved by inserting the mold only from the opening side of the inner diameter gradually-increasing portion 52 in the axial direction of the venturi forming block 21. When the venturi portion 50 is subjected to the machining processing, this can be achieved by performing the machining processing only from the opening side of the inner diameter gradually-increasing portion 52 in the axial direction of the venturi forming block 21. Therefore, manufacturability of the venturi portion 50 (the venturi forming block 21) can be improved.

Third Embodiment

In the pump apparatus 1 according to a third embodiment, the pump housing main body 20 is made from a metallic material similarly to the first embodiment. On the other hand, the venturi forming block 21 is also made from a metallic material unlike the first embodiment. More specifically, the venturi forming block 21 is made from a sintered material. The venturi portion 50 is formed with use of a mold when metallic powder is molded by being compacted in a powder compacting process. This compact is sintered, by which the venturi forming block 21 is formed.

If the pump apparatus 1 is configured in such a manner that the venturi forming block 21 is joined to the pump housing main body 20 (the venturi forming block containing hole 228 of the rear body 22), this configuration can raise a problem such as occurrence of a distortion between the venturi forming block 21 and the pump housing main body 20 after the venturi forming block 21 is joined to the pump housing main body 20. On the other hand, in the present embodiment, the venturi forming block 21 is made from the metallic material. Therefore, the venturi forming block 21 has a similar linear expansion coefficient to the pump housing main body 20. Therefore, the present embodiment can prevent or reduce occurrence of a problem like the above-described example. Further, the venturi portion 50 (the inner diameter gradually-increasing portion 52 and the like) is formed with use of the mold. Therefore, the venturi portion 50 can be easily formed compared to forming the venturi portion 50 (the inner diameter gradually-increasing portion 52 and the like) by the machining processing.

Fourth Embodiment

The pump apparatus 1 according to a fourth embodiment is different from the first embodiment in terms of the layout of the venturi portion 50 and the like. The fourth embodiment will be described below focusing on only configurations different from the first embodiment. Configurations shared with the first embodiment will be identified by the same reference numerals as the first embodiment, and descriptions thereof will be omitted. FIG. 14 illustrates the pump housing 2 as viewed from the direction in which the driving shaft 40 (the central axis O) extends (as viewed from the negative side in the z-axis direction), and a part of an inner structure and contained components are indicated by broken lines. FIG. 15 illustrates a cross section as viewed from a line B-B illustrated in FIG. 14. An orthogonal coordinate system is set in a similar manner to the first embodiment (FIG. 3 and the like). The pump housing 2 does not include the venturi forming block 21 like the first embodiment. The pump housing main body 20 (the rear body 22) does not include the venturi forming block containing hole 228 like the first embodiment. The inner diameter gradually-reducing portion 210 and the venturi portion 50 are directly formed inside the rear body 22.

The inner diameter gradually-reducing portion 210 and the venturi portion 50 extend in the z-axis direction on the positive side of the rear body 22 in the x-axis direction and the negative side of the rear body 22 in the y-axis direction. In other words, the longitudinal direction of the venturi portion 50 extends generally in parallel with the direction of the central axis O (the z-axis direction) and also extends perpendicularly to the longitudinal direction of the valve containing hole 227 (the x-axis direction). The venturi portion 50 does not overlap the containing recessed portion 220 in the direction perpendicular to the z axis (the radial direction of the rotational axis of the driving shaft 40) (the venturi portion 50 is located on the radially outer side with respect to the containing recessed portion 220), but overlaps the containing recessed portion 220 in the z-axis direction. The inner diameter gradually-reducing portion 210 includes a first inner diameter gradually-reducing portion 210a where a narrower angle sandwiched between inner walls thereof is relatively large, and a second inner diameter gradually-reducing portion 210b where a narrower angle thereof is relatively small. An end of the first inner diameter gradually-reducing portion 210a on the positive side in the z-axis direction is opened on the surface of the rear body 22 on the positive side in the z-axis direction. An inner diameter of the first inner diameter gradually-reducing portion 210a gradually reduces from the positive side toward the negative side in the z-axis direction. An end of the second inner diameter gradually-reducing portion 210b on the positive side in the z-axis direction is connected to an end of the first inner diameter gradually-reducing portion 210a on the negative side in the z-axis direction. An inner diameter of the second inner diameter gradually-reducing portion 210b gradually reduces from the positive side toward the negative side in the z-axis direction. An end of the small diameter portion 51 on the positive side in the z-axis direction is connected to an end of the second inner diameter gradually-reducing portion 210b on the negative side in the z-axis direction. An end of the small diameter portion 51 on the negative side in the z-axis direction is connected to an end of the inner diameter gradually-increasing portion 52 on the positive side in the z-axis direction. The inner diameter of the inner diameter gradually-increasing portion 52 gradually increases from the positive side toward the negative side in the z-axis direction. An end of the inner diameter gradually-increasing portion 52 on the negative side in the z-axis direction is opened on the surface of the rear body 22 on the negative side in the z-axis direction.

The second hole 222 extends in the z-axis direction on the negative side of the rear body 22 in the x-axis direction and the negative side of the rear body 22 in the y-axis direction. An end of the second hole 222 on the negative side in the z-axis direction is connected to an end of the first hole 221 on the negative side in the y-axis direction. An end of the second hole 222 on the positive side in the z-axis direction is opened on the surface of the rear body 22 on the positive side in the z-axis direction. The third hole 223 is formed inside the front body 24 and is disposed so as to extend in the x-axis direction. An end of the third hole 223 on the negative side in the x-axis direction is bent toward the negative side in the z-axis direction and opened on the surface of the front body 24 on the negative side in the z-axis direction, and is also connected to the end of the second hole 222 on the positive side in the z-axis direction. An end of the third hole 223 on the positive side in the x-axis direction is bent toward the negative side in the z-axis direction and opened on the surface of the front body 24 on the negative side in the z-axis direction, and is also connected to the end of the first inner diameter gradually-reducing portion 210a on the positive side in the z-axis direction. An inner diameter of the end of the first inner diameter gradually-reducing portion 210a on the positive side in the z-axis direction is approximately equal to an inner diameter of the third hole 223. The fourth hole 224 connects the end of the valve containing hole 227 on the positive side in the x-axis direction and the small diameter portion 51 of the venturi portion 50.

Next, functions and effects will be described. The pump housing 2 does not include the venturi forming block 21, and the inner diameter gradually-reducing portion 210 and the venturi portion 50 are directly formed inside the pump housing 2 (the rear body 22). Therefore, the present embodiment can reduce the number of components.

The venturi portion 50 should have a long dimension (a large space in the longitudinal direction) compared to the orifice. On the other hand, the pump housing 2 has a dimension of the driving shaft 40 in the rotational axis direction that is enough to contain the pump element 4 therein from the beginning. In the present embodiment, the venturi portion 50 is disposed so as to be located on the radially outer side with respect to the pump element containing portion (the containing recessed portion 220) and overlap the pump element containing portion (the containing recessed portion 220) in the direction of the rotational axis (the central axis O) of the driving shaft 40. The venturi portion 50 is disposed so as to utilize the originally existing space extending in the direction of the rotational axis of the driving shaft 40 in this manner, by which the present embodiment can prevent or cut down the increase in the size of the outer shape of the pump element 1 (in the direction of the rotational axis of the driving shaft 40). Further, the venturi portion 50 is disposed in such a manner that the longitudinal direction of the venturi portion 50 and the direction of the rotational axis (the central axis O) of the driving shaft 40 extend generally in parallel with each other. Therefore, the present embodiment can prevent or cut down the increase in the dimension of the pump apparatus 1 in the radial direction of the rotational axis of the driving shaft 40. The functions and effects due to the above-described layout can also be acquired even when the venturi portion 50 is formed in the venturi forming block 21.

Fifth Embodiment

The pump apparatus 1 according to a fifth embodiment is different from the first embodiment in terms of the housing where the venturi portion 50 and the control valve 8 are set up. The fifth embodiment will be described below focusing on only differences from the first embodiment. A transmission housing 10a is a housing of the CVT unit, and is a separate member from the pump housing 2. The pump housing 2 may be disposed integrally with the transmission housing 10a, or may be spaced apart from the transmission housing 10a. While the pump element 4 is provided in the pump housing 2, the venturi portion 50 and the control valve 8 are provided in the transmission housing (for example, a housing of the control valve) 10a as indicated by a broken line illustrated in FIG. 1.

In this manner, the venturi portion 50 or the control valve 8 is not provided on the pump housing 2 side but is provided on the transmission housing 10a side, by which the present embodiment can reduce the size of the unit including the pump element 4 and improve layout flexibility thereof. When the control valve 8 is provided on the transmission housing 10a side, the hydraulic fluid supplied from the pump element 4 (the pump housing 2) to the transmission housing 10a is a flow amount before the hydraulic fluid is controlled by the control valve 8. The control valve 8 controls the flow amount of the hydraulic fluid to be supplied from the pump element 4 to the CVT 10. The above-described “flow amount of the hydraulic fluid to be supplied from the pump element 4 to the CVT 10” means a flow amount to be actually supplied to the CVT 10 existing inside the transmission housing 10a. As indicated by an alternate long and short dash line in FIG. 1, the venturi portion 50 may be provided in the transmission housing 10a, and the pump element 4 and the control valve 8 may be provided in the pump housing 2. Further, the venturi portion 50 and the control valve 8 may be provided in a housing other than the transmission housing 10a.

Sixth Embodiment

The pump element according to a sixth embodiment is a variable displacement pump in which the pump capacity is variably controlled. The sixth embodiment will be described below focusing on only configurations different from the first embodiment. Configurations shared with the first embodiment will be identified by the same reference numerals as the first embodiment, and descriptions thereof will be omitted. FIG. 16 is a similar view to FIG. 2 that schematically illustrates a configuration of the pump apparatus 1. FIG. 17 illustrates a partial cross section acquired by cutting the pump housing 2 along the plane including the central axis O. The z axis is set to a horizontal direction in FIG. 17, and a positive side thereof is set to a right side in FIG. 17. The containing recessed portion 220, an intake pressure chamber 220a, the discharge pressure chamber 226, the valve containing hole 227, the venturi forming block containing hole (not illustrated), a bearing holding hole 229, and the plurality of passages 3 and the like are formed in the rear body 22. The plurality of passages 3 and the like include the intake passage 3, the discharge passage 5, the high pressure passage 6, the intermediate pressure passage 7, a first control passage 60, a second control passage 70, and the return passage 9. The intake pressure chamber 220a and the discharge pressure chamber 226 are opened to the bottom portion of the containing recessed portion 220. A bush 401 as a bearing is mounted on an inner periphery of the bearing holding hole 229. The end of the valve containing hole 227 on the negative side in the x-axis direction is opened on the outer surface of the rear body 22. A solenoid 80 is fitted in this opening via a seal member 253. A rod 800 protrudes from the solenoid 80 toward the positive side in the x-axis direction.

A shaft containing hole 234 is provided at the side plate 23. The intake port 230, the discharge port 231, an intake-side backpressure port 232, and a discharge-side backpressure port 233 are provided at the surface of the side plate 23 on the one side in the axial direction. The intake port 230 and the discharge port 231 are grooves extending in the circumferential direction in a generally circular-arc manner, and are provided at positions opposite of the shaft containing hole 234 from each other. The intake-side backpressure port 232 is a groove extending in the circumferential direction in a generally circular-arc manner on one side closer to the shaft containing hole 234 (the radially inner side) with respect to the intake port 230, and is provided in a range overlapping the intake port 230 in the circumferential direction. The discharge-side backpressure port 233 is a groove extending in the circumferential direction in a generally circular-arc manner on the radially inner side with respect to the discharge port 231, and is provided in a range overlapping the discharge port 231 in the circumferential direction. The intake port 230 and the intake-side backpressure port 232 are connected to the intake pressure chamber 220a of the rear body 22 via a communication passage in the side plate 23. The discharge port 231 and the discharge-side backpressure port 233 are connected to the discharge pressure chamber 226 via a communication passage in the side plate 23. An annular seal groove is formed on the surface of the side plate 23 on the negative side in the z-axis direction so as to surround an outer edge of the side plate 23. An annular seal member 250 is mounted in this seal groove. An annular seal groove is formed on the surface of the bottom portion of the containing recessed portion 220 on the positive side in the z-axis direction so as to surround an opening of the bearing holding hole 229. An annular seal member 251 is mounted in this seal groove. An annular seal groove is formed on the surface of the bottom portion of the containing recessed portion 220 on the positive side in the z-axis direction so as to surround an outer periphery of an opening of the discharge pressure chamber 226. An annular seal member 252 is mounted in this seal groove. The seal member 252 defines a high pressure region and a low pressure region on an inner peripheral side and an outer peripheral side of the seal member 252, respectively.

A bush 402 as a bearing is mounted on an inner periphery of a bearing holding hole 244 of the front body 24. An intake port 240 and a discharge port 241, and an intake-side backpressure port 242 and a discharge-side backpressure port 243 are formed on the end surface of the front body 24 on the negative side in the z-axis direction at positions generally corresponding in the z-axis direction to the individual ports 230 and 231 and the individual ports 232 and 233 formed at the side plate 23 and with similar shapes to them, respectively. The front body 24 is fixed by being fastened to the rear body 22 with use of a bolt 26.

An adapter ring 44 is mounted in the containing recessed portion 220 of the rear body 22 on the positive side of the side plate 23 in z-axis direction. The adapter ring 44 has an annular shape, and an outer periphery of the adapter ring 44 is fitted to the inner periphery of the containing recessed portion 220. An inner peripheral surface of the adapter ring 44 has a generally cylindrical shape extending in the z-axis direction and is generally ecliptic as viewed from the z-axis direction. A first groove portion 441, a second groove portion 442, a first flat surface portion 443, a second flat surface portion 444, and a recessed portion 445 are provided on this inner peripheral surface. The first groove portion 441 has a semi-cylindrical shape extending in the z-axis direction, and is provided on the first flat surface portion 443. The first and second control passages 60 and 70 are provided on both sides of the first groove portion 441 so as to radially penetrate through the adapter ring 44. The second groove portion 442 is provided on an opposite side of a center (a central axis) of the adapter ring 44 from the first groove portion 441, and extends in the z-axis direction. The second flat surface portion 444 is provided between the first and second groove portions 441 and 442 (a generally middle position therebetween) in a circumferential direction of the adapter ring 44. The recessed portion 445 is provided on an opposite side of the center of the adapter ring 44 from the second flat surface portion 444.

The pump element 4 is contained in a space surrounded by an inner peripheral surface of the adapter ring 44, the surface of the side plate 23 on the positive side in the z-axis direction, and the surface of the front body 24 on the negative side in the z-axis direction. In other words, the above-described space functions as the pump element containing portion. Eleven slits 410 are provided at the rotor 41. The cam ring 43 is annularly formed, and the inner peripheral surface thereof has a generally cylindrical shape. A semi-cylindrical groove portion 433 extending in the z-axis direction is provided on an outer peripheral surface of the cam ring 43. The cam ring 43 is provided in the pump element containing portion so as to surround the rotor 41. The cam ring 43 forms the plurality of pump chambers 400 together with the rotor 41 and the vanes 42. In other words, the side plate 23 and the front body 24 are disposed on the side surfaces of the cam ring 43 and the rotor 41 in the axial direction. The space between the inner peripheral surface of the cam ring 43 and the outer peripheral surface of the rotor 41 is sealingly closed on the both sides thereof in the axial direction by the side plate 23 and the front body 24, while being divided into the eleven pump chambers 400 by the plurality of vanes 42.

The cam ring 43 is provided displaceably in the pump element containing portion. A pin 453 is installed by being fitted between the first groove portion 441 of the adapter ring 44 and the groove portion 433 of the cam ring 43. The pin 453 is fixed to the pump housing 2. The pin 453 prevents or reduces a rotation of the adapter ring 44 relative to the pump housing 2 and also prevents or reduces a rotation of the cam ring 43 relative to the adapter ring 44. The cam ring 43 is contained on the inner peripheral side of the adapter ring 44 swingably relative to the pump housing 2. The cam ring 43 is supported on the first flat surface portion 443 relative to the adapter ring 44. The cam ring 43 swings with the first flat surface portion 443 serving as a supporting point thereof by being displaced while rolling on the first flat surface portion 443. Hereinafter, an amount by which a center (a central axis) of the inner peripheral surface of the cam ring 43 is offset from the center (the central axis O) of the rotor 41 (the driving shaft 40) will be referred to as an eccentric amount 5.

A seal member 46 is mounted in the second groove portion 442 of the adapter ring 44. When the cam ring 43 swings, the first flat surface portion 443 of the adapter ring 44 contacts the outer peripheral surface of the cam ring 43 and the seal member 46 also contacts the outer peripheral surface of the cam ring 43. The above-described space between the inner peripheral surface of the adapter ring 44 and the outer peripheral surface of the cam ring 43 is liquid-tightly divided into a pair of spaces by the first flat surface portion 443 (a portion thereof in abutment with the outer peripheral surface of the cam ring 43) and the seal member 46. In other words, two fluid pressure chambers 61 and 71 are formed as the pair of spaces between the cam ring 43 and the pump element containing portion. For convenience of the description, an X axis and a Y axis are set to a long-axis direction and a short-axis direction of the generally ecliptic inner peripheral surface of the adapter ring 44, respectively, as illustrated in FIG. 16. On the outer peripheral side of the cam ring 43, a first fluid pressure chamber 61 is defined on the negative side in the X-axis direction that is one side where the eccentric amount δ increases, and a second fluid pressure chamber 71 is defined on the positive side in the X-axis direction that is the other side where δ reduces. When δ increases, a volume of the first fluid pressure chamber 61 reduces and a volume of the second fluid pressure chamber 71 increases. One end of a spring 47 is set in the recessed portion 445 of the adapter ring 44 inside the second fluid pressure chamber 71. The other end of the spring 47 is set on the outer peripheral side of the cam ring 43. The spring 47 is mounted in a compressed state, and constantly biases the cam ring 43 relative to the adapter ring 44 toward the negative side in the X-axis direction (the one side where the first fluid pressure chamber 61 is located). The displacement of the cam ring 43 toward the negative side in the X-axis direction is regulated by abutment of the outer peripheral surface of the cam ring 43 with the second flat surface portion 444 of the adapter ring 44 inside the first fluid pressure chamber 61.

The rotor 41 rotates in a clockwise direction in FIG. 16. With the center of the cam ring 43 located eccentrically from the central axis O (toward the negative side in the X-axis direction), a radial distance between the outer peripheral surface of the rotor 41 and the inner peripheral surface of the cam ring 43 (a radial dimension of the pump chamber 400) increases as approaching the negative side in the X-axis direction from the positive side in the X-axis direction. The vane 42 projects from the slit 410 and retracts into the slit 410 according to this change in the distance, by which each of the pump chamber 400 is defined. The volume of the pump chamber 400 on the negative side in the X-axis direction becomes larger than the volume of the pump chamber 400 on the positive side in the X-axis direction. Due to this difference in the volume of the pump chamber 400, the volume of the pump chamber 400 reduces as the rotor 41 rotates (as the pump chamber 400 travels toward the positive side in the X-axis direction) on the positive side in the Y-axis direction with respect to the central axis O, while increasing as the rotor 41 rotates (as the pump chamber 400 travels toward the negative side in the X-axis direction) on the negative side in the Y-axis direction with respect to the central axis O. The pump chamber 400 periodically expands and contracts while rotating in the clockwise direction around the central axis O. The intake port 230 is opened to the intake region where the volume of the pump chamber 400 increases according to the rotation of the driving shaft 40. The discharge port 231 is opened to the discharge region where the volume of the pump chamber 400 reduces according to the rotation of the driving shaft 40.

The intake passage 3 connects the oil pan 100 and the intake pressure chamber 220a to each other. The discharge passage 5 connects the discharge pressure chamber 226 and the CVT 10 to each other. The high pressure passage 6 branches off from the discharge passage 5 on the upstream side of the venturi portion 50 in the discharge passage 5, and is connected to the positive side of the valve containing hole 227 in the x-axis direction. The intermediate pressure passage 7 branches off from the venturi portion 50 (the small diameter portion 51) in the discharge passage 5 and is connected to the negative side of the valve containing hole 227 in the x-axis direction. The first control passage 60 and the second control passage 70 connect the control valve 8 and the pump element 4 to each other. The first control passage 60 is connected to the positive side of the valve containing hole 227 in the x-axis direction with respect to the high pressure passage 6, and is also connected to the first fluid pressure chamber 61 by penetrating through the adapter ring 44. The second control passage 70 is connected to the negative side of the valve containing hole 227 in the x-axis direction with respect to the intermediate pressure passage 7, and is also connected to the second fluid pressure chamber 71 by penetrating through the adapter ring 44. The return passage 9 is connected to between the first control passage 60 and the second control passage 70 in the valve containing hole 227. Regardless of the displacement of the control valve 8 inside the valve containing hole 227, the high pressure passage 6 is opened to the high pressure chamber 86, the intermediate pressure passage 7 is opened to the intermediate pressure chamber 88, and the return passage 9 is opened to the drain chamber 89.

The control valve 8 switches the flow passage of the hydraulic fluid between the first control passage 60 and the second control passage 70. In an initial state where the control valve 8 is maximally displaced toward the negative side in the x-axis direction, an opening portion of the first control passage 60 in the valve containing hole 227 is in communication with the drain chamber 89 while being out of communication with the high pressure chamber 86 due to the first land portion 8. In the same initial state, an opening portion of the second control passage 70 is in communication with the intermediate pressure chamber 88 while being out of communication with the drain chamber 89 due to the second land portion 82. As a result, the hydraulic fluid in the intermediate pressure chamber 88 flows into the second fluid pressure chamber 71. The high pressure is not supplied into the first fluid pressure chamber 61 and the intermediate pressure is supplied into the second fluid pressure chamber 71, so that the cam ring 43 is displaced into an eccentric state. Therefore, the pump discharge flow amount increases according to the number of rotations. With the control valve 8 displaced toward the positive side in the x-axis direction by a predetermined amount or more, the opening portion of the first control passage 60 is in communication with the high pressure chamber 86 while being out of communication with the drain chamber 89 due to the first land portion 81. In the same state, the opening portion of the second control passage 70 is in communication with the drain chamber 89 while being out of communication with the intermediate pressure chamber 88 due to the second land portion 82. As a result, the flow passage is switched, so that the hydraulic fluid in the high pressure chamber 86 starts to flow into the first fluid pressure chamber 61 via the first control passage 60. The high pressure is supplied into the first fluid pressure chamber 61, and the intermediate pressure is not supplied into the second fluid pressure chamber 71. Therefore, the eccentric amount δ of the cam ring 43 reduces and the pump capacity reduces, so that the pump discharge flow amount does not increase even when the number of rotations of the pump increases. In other words, the control valve 8 switches the flow passage in such a manner that the hydraulic fluid introduced via the high pressure passage 6 is introduced into the first fluid pressure chamber 61 based on the differential pressure Δp between the upstream side and the small diameter portion 51 of the venturi portion 50. When the hydraulic fluid starts to be introduced into the first fluid pressure chamber 61, the flow amount to be supplied to the CVT 10 via the discharge passage 5 is limited to a required amount. In this manner, the venturi portion 50, the high pressure passage 6, the intermediate pressure passage 7, the control valve 8, the first control passage 60, the second control passage 70, the first fluid pressure chamber 61, and the second fluid pressure chamber 71 function as a controller that controls the discharge flow amount of the pump element 4.

The activation of the control valve 8 is controlled based on the differential pressure Δp applied to the both sides of the control valve 8 in the axial direction according to the discharge flow amount of the pump element 4, and is also controlled based on a thrust force applied from the solenoid 80 to the control valve 8. In other words, a distal end of the rod 800 of the solenoid 80 is in abutment with the end surface of the control valve 8 on the negative side in the x-axis direction. The rod 800 is displaceable in the x-axis direction due to an electromagnetic force generated by the solenoid 80. The control valve 8 is subjected to a force F4 applied from the solenoid 80 toward the positive side in the x-axis direction via the rod 800. The thrust force F4 of the solenoid 80 is controlled based on an instruction from the CVT control unit. When a sum of the difference between F1 and F2, i.e., F1−F2 (the force corresponding to the differential pressure Δp) and F4 (F1−F2+F4) exceeds F3, the control valve 8 is displaced toward the positive side in the x-axis direction. With the solenoid 80 deactivated, the force competing against the initial set load F3 of the spring 88 is only the force F1−F2 due to the differential pressure Δp. On the other hand, the differential pressure Δp (i.e., F1−F2) cannot be sufficiently secured until the discharge flow amount increases to some degree. This leads to such an operation of maintaining a certain flow amount after achieving a relatively large discharge flow amount. Generating F4 by supplying power to the solenoid 80 can bring about the same effect as changing the initial set load F3 of the spring 88 to a lower load. In other words, this configuration allows the control valve 8 to be displaced and switch the flow passage with the relatively small differential pressure Δp (i.e., F1−F2). Therefore, this configuration leads to such an operation of maintaining a certain flow amount after achieving a relatively small discharge flow amount. In this manner, the present embodiment can control the discharge flow amount with use of a magnetic attractive force (the thrust force F4) generated by the solenoid 80. The CVT control unit appropriately controls a line pressure of the CVT 10 according to running conditions such as the number of revolutions of the engine, an opening degree of an accelerator (an opening degree of a throttle valve), and a vehicle speed. According thereto, the CVT control unit supplies a current to the solenoid 80 based on the number of revolutions of the engine, the opening degree of the accelerator, and the like to control the magnetic attractive force (the thrust force F4), thereby changing the discharge flow amount (the pump capacity) of the pump element 4. The pump apparatus 1 may be configured to omit the solenoid 80.

The present embodiment can also acquire each of functions and effects regarding the venturi portion 50 similar to the first embodiment even for the variable displacement pump.

Other Embodiments

Having described the pump apparatus according to the present invention based on the embodiments thereof, the specific configuration of the present invention is not limited to the embodiments, and the present invention also includes a design modification and the like thereof made within a range that does not depart from the spirit of the present invention. For example, the stepless transmission to which the pump apparatus supplies the hydraulic fluid is not limited to the CVT, and may be, for example, a toroidal-type transmission. The automatic transmission to which the pump apparatus supplies the hydraulic fluid is not limited to the stepless transmission, and may be a stepped transmission. The apparatus mounted on the vehicle to which the pump apparatus supplies the hydraulic fluid is not limited to the automatic transmission, and may be a power steering apparatus or the like. Further, the configurations of the individual embodiments can also be arbitrarily combined to each other or one another.

The present application claims priority to Japanese Patent Application No. 2015-004311 filed on Jan. 13, 2015. The entire disclosure of Japanese Patent Application 2015-004311 filed on Jan. 13, 2015 including the specification, the claims, the drawings, and the abstract is incorporated herein by reference in its entirety.

REFERENCE SIGNS LIST

1 pump apparatus

10 CVT (automatic transmission)

2 pump housing

20 pump housing main body

21 venturi forming block

213 communication hole (opening)

230 intake port

231 discharge port

4 pump element

40 driving shaft

400 pump chamber

41 rotor

410 slit

42 vane

43 cam ring

5 discharge passage

50 venturi portion

51 small diameter portion

52 inner diameter gradually-increasing portion

520 front portion

521 rear portion

53 large diameter portion

61 first fluid pressure chamber

71 second fluid pressure chamber

8 control valve

86 high pressure chamber

87 intermediate pressure chamber

Claims

1. An automatic transmission pump apparatus for supplying hydraulic fluid to an automatic transmission of a vehicle, the automatic transmission pump apparatus comprising: a pump housing including a pump element containing portion;a driving shaft pivotally supported on the pump housing;a pump element provided in the pump element containing portion and configured to be rotationally driven by the driving shaft, the pump element forming a plurality of pump chambers around the driving shaft;an intake port formed at the pump housing and opened to an intake region where a volume of a pump chamber increases according to a rotation of the driving shaft among the plurality of pump chambers;a discharge port formed at the pump housing and opened to a discharge region where the volume of the pump chamber reduces according to the rotation of the driving shaft among the plurality of pump chambers;a discharge passage connected to the discharge port; anda venturi portion provided on the way along the discharge passage, the venturi portion including a small diameter portion having a smaller inner diameter than an inner diameter of the discharge passage from the discharge port to the venturi portion and an inner diameter gradually-increasing portion formed in such a manner that an inner diameter thereof gradually increases from the small diameter portion toward a downstream side of the discharge passage; anda control valve configured to receive introduction of hydraulic fluid on an upstream side of the venturi portion and hydraulic fluid in the venturi portion, the control valve including a spool valve body controlled based on a differential pressure between the hydraulic fluid on the upstream side of the venturi portion and the hydraulic fluid in the venturi portion, the control valve being configured to control a flow amount of the hydraulic fluid to be supplied into the automatic transmission at least by switching a flow passage of the hydraulic fluid introduced from the upstream side of the venturi portion.

2. The automatic transmission pump apparatus according to claim 1, wherein the pump housing includes a pump housing main body including the pump element containing portion, and a venturi forming block that is a separate member from the pump housing main body and is joined to the pump housing main body, wherein the venturi portion is formed at the venturi forming block, andwherein the venturi forming block is jointed to the pump housing main body after the venturi portion is formed.

3. The automatic transmission pump apparatus according to claim 2, wherein the pump housing main body is made from a metallic material, wherein the venturi forming block is made from a resin material, andwherein the venturi portion is formed by molding.

4. The automatic transmission pump apparatus according to claim 2, wherein the pump housing main body is made from a metallic material, wherein the venturi forming block is made from a sintered material, andwherein the venturi portion is formed with use of a mold in a powder compacting process.

5. The automatic transmission pump apparatus according to claim 2, wherein the small diameter portion of the venturi portion is formed so as to be opened on an outer surface of the venturi forming block.

6. The automatic transmission pump apparatus according to claim 1, wherein the venturi portion is provided in such a manner that a longitudinal direction of the venturi portion and a direction of a, rotational axis of the driving shaft extend generally perpendicularly to each other.

7. The automatic transmission pump apparatus according to claim 6, wherein the venturi portion is provided at a position that does not overlap the intake port on a cross section perpendicular to the rotational axis of the driving shaft but overlaps the intake port in the direction of the rotational axis of the driving shaft.

8. The automatic transmission pump apparatus according to claim 6, wherein the venturi portion is provided in such a manner that a longitudinal direction of the venturi portion and a longitudinal direction of the control valve extend generally in parallel with each other.

9. The automatic transmission pump apparatus according to claim 8, wherein the control valve includes a high pressure chamber into which a pressure on the upstream side of the venturi portion is introduced and an intermediate pressure chamber into which a pressure in the venturi portion is introduced, and wherein the venturi portion is disposed in such a manner that the upstream side of the venturi portion faces the high pressure chamber of the control valve.

10. The automatic transmission pump apparatus according to claim 1, wherein the venturi portion is provided in such a manner that a longitudinal direction of the venturi portion and a direction of a rotational axis of the driving shaft extend generally in parallel with each other.

11. The automatic transmission pump apparatus according to claim 10, wherein the venturi portion is provided at a position that is located on a radially outer side with respect to the pump element containing portion in a radial direction of the rotational axis of the driving shaft, and overlaps the pump element containing portion in the direction of the rotational axis of the driving shaft.

12. The automatic transmission pump apparatus according to claim 1, wherein the venturi portion includes an opening provided on the small diameter portion or one side of the inner diameter gradually-increasing portion that is closer to the small diameter portion in a longitudinal direction of the venturi portion, the opening being configured to supply the hydraulic fluid in the venturi portion into the control valve, and wherein the opening includes a plurality of openings provided in a direction around an axis line along the longitudinal direction of the venturi portion.

13. The automatic transmission pump apparatus according to claim 1, wherein the venturi portion is formed in such a manner that a narrower angle sandwiched between inner walls of the inner diameter gradually-increasing portion is 60 degrees or smaller.

14. The automatic transmission pump apparatus according to claim 13, wherein, when it is defined that L represents a length of a longitudinal direction of the inner diameter gradually-increasing portion when the inner diameter gradually-increasing portion is formed as far as an inner diameter thereof reaches a same diameter as an inner diameter of the discharge passage from the discharge port to the venturi portion while the narrower angle sandwiched between inner walls of the inner diameter gradually-increasing portion is kept constant, the inner diameter gradually-increasing portion includes a front portion formed as far as a position where the length in the longitudinal direction is 65% of the length L or longer while the narrower angle sandwiched between the inner walls of the inner diameter gradually-increasing portion is kept constant at 60 degrees or smaller, and a rear portion provided on a downstream side of the front portion and formed in such a manner that the narrower angle exceeds 60 degrees.

15. The automatic transmission pump apparatus according to claim 1, wherein the control valve or the venturi portion is provided at a housing that is a separate member from the pump housing.

16. The automatic transmission pump apparatus according to claim 1, wherein the venturi portion includes an opening provided at the small diameter portion and configured to supply the hydraulic fluid in the venturi portion to the control valve.

17. The automatic transmission pump apparatus according to claim 1, wherein the pump element is a pump element for a fixed displacement pump in which a discharge amount per rotation of the driving shaft is constant, and wherein the control valve switches the flow passage of the hydraulic fluid so as to return the hydraulic fluid introduced from the upstream side of the venturi portion to an intake port side.

18. The automatic transmission pump apparatus according to claim 1, wherein the pump element includes a rotor including a plurality of slits in a circumferential direction,a vane provided so as to be projectable and retractable from and into each of the slits of the rotor,a cam ring provided displaceably in the pump element containing portion and annularly formed, the cam ring forming the plurality of pump chambers together with the rotor and the vane, anda first fluid pressure chamber and a second fluid pressure chamber that are a pair of spaces formed between the cam ring and the pump element containing portion, the first fluid pressure chamber and the second fluid pressure chamber being respectively provided on one side where a volume reduces and an opposite side where the volume increases when an eccentric amount of the cam ring with respect to the rotor increases,wherein the pump element is a pump element of a variable displacement pump in which a discharge amount per rotation of the driving shaft is variably controlled, andwherein the control valve switches the flow passage of the hydraulic fluid so as to introduce the hydraulic fluid introduced from the upstream side of the venturi portion into the first fluid pressure chamber.

19. A pump apparatus comprising: a pump housing including a pump element containing portion;a driving shaft pivotally supported on the pump housing;a pump element provided in the pump element containing portion and configured to be rotationally driven by the driving shaft, the pump element forming a plurality of pump chambers around the driving shaft;an intake port formed at the pump housing and opened to an intake region where a volume of a pump chamber increases according to a rotation of the driving shaft among the plurality of pump chambers;a discharge port formed at the pump housing and opened to a discharge region where the volume of the pump chamber reduces according to the rotation of the driving shaft among the plurality of pump chambers;a discharge passage connected to the discharge port; anda venturi portion provided on the way along the discharge passage, the venturi portion including a small diameter portion having a smaller inner diameter than an inner diameter of the discharge passage from the discharge port to the venturi portion and an inner diameter gradually-increasing portion formed in such a manner that an inner diameter thereof gradually increases from the small diameter portion toward a downstream side of the discharge passage; anda control valve configured to receive introduction of hydraulic fluid on an upstream side of the venturi portion and hydraulic fluid in the small diameter portion, the control valve including a spool valve body controlled based on a differential pressure between the hydraulic fluid on the upstream side of the venturi portion and the hydraulic fluid in the small diameter portion, the control valve being configured to control a flow amount of the hydraulic fluid to be supplied into an apparatus mounted on a vehicle at least by switching a flow passage of the hydraulic fluid introduced from the upstream side of the venturi portion.