Patent Application
20130280041
This application claims the foreign priority benefit of Japanese Patent Application No. 2012-0953901, filed Apr. 19, 2012, in the Japanese Intellectual Property Office, the disclosure of which is incorporated herein by reference.
1. Field
The present invention relates to an oil pump which sucks and discharges oil (lubricant oil) of an internal combustion engine (hereinafter, called an engine) or the like, and in particular, relates to an oil pump including an inner rotor and an outer rotor of a trochoid type, an internal gear type (involute type), or the like.
2. Description of the Related Art
There has been known an oil pump for an engine including a housing which has an inlet port for sucking oil, a discharge port for discharging oil, an air vent hole (an ejection port, or a deairing port) for ejecting air mixed with oil and the like, a rotary shaft (drive shaft) which is supported by the housing, an inner rotor which is rotated by the rotary shaft and which has external teeth, an outer rotor which has internal teeth engaged with the external teeth of the inner rotor and which defines a volume-varying pump chamber in cooperation with the inner rotor, and the like. Here, pumping action is obtained by rotating the inner rotor via the rotary shaft and rotating the outer rotor as being coordinated with the rotation of the inner rotor, so that oil sucked through the inlet port is pressurized and discharged through the discharge port while air (bubble) mixed with oil is ejected through the air vent hole. For example, see Japanese Patent Application No. 9-203308, Japanese Patent Application No. 6-167278, and Japanese Patent Application No. 4-65974.
Since the above conventional oil pumps are a one-stage pressurization type having only one set of pump unit which includes the inner rotor and the outer rotor, there is a fear that required discharge pressure may not be satisfied depending on an engine to which the oil pump is adopted.
Meanwhile, there has been known a fluid pump capable of ensuring high discharge pressure including a housing which has one or two inlet ports for sucking oil from the outside and one discharge port for discharging oil to the outside, a rotary shaft (drive shaft) which is supported by the housing, and a prior-stage pump unit and a latter-stage pump unit arranged in an axial direction of the rotary shaft. Here, the prior-stage pump unit is structured with one set or two sets of an inner rotor (inner gear) and an outer rotor (outer gear) and the latter-stage pump unit is structured with one set of an inner rotor (inner gear) and an outer rotor (outer gear). A discharge rate of the prior-stage pump unit and a discharge rate of the latter-stage pump unit are set to be the same. Pumping action at the first stage due to the prior-stage pump unit and pumping action at the second stage due to the latter-stage pump unit are obtained by rotating the prior-stage and latter-stage inner rotors (inner gears) via the rotary shaft and rotating the prior-stage and latter-stage outer rotors (outer gears) as being coordinated with the rotation of the inner rotors (inner gears). Fluid is pressurized as being sucked through the inlet port and double-pressurized fluid is discharged through the discharge port. For example, see Japanese Patent Application No. 2007-127071.
In the above two-stage pressurization type fluid pump, the discharge rate (discharge pressure) of the prior-stage pump unit and the discharge rate (discharge pressure) of the latter-stage pump unit are simply set to be the same without considering influence on discharge characteristics when air or the like is mixed with fluid to be sucked. Therefore, there is a fear that desired discharge characteristics (discharge rate) cannot be ensured when air or the like is mixed.
Additional aspects and/or advantages will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the invention.
To address the above issues, the present invention provides an oil pump which ensures desired pumping performance even if air or the like is mixed with oil to be sucked and provides pumping characteristics having desired high discharge pressure (discharge rate).
An oil pump according to the present invention includes an upstream pump unit which includes an upstream inner rotor and an upstream outer rotor; a downstream pump unit which includes a downstream inner rotor and a downstream outer rotor as being arranged adjacently to the upstream pump unit in a predetermined axis line direction; a rotary shaft which concurrently rotates the upstream inner rotor and the downstream inner rotor; and a housing which contains the upstream pump unit and the downstream pump unit as supporting the rotary shaft and which includes an inlet port configured to suck oil from the outside into the upstream pump unit, an ejection port configured to eject a part of the sucked oil to the outside in a pressurization process of the upstream pump unit, a communication port which provides communication between the upstream pump unit and the downstream pump unit, and a discharge port configured to discharge oil from the downstream pump unit to the outside.
According to the above structure, in a case that the oil pump is mounted on an engine for sucking and pressure-feeding oil (lubricant oil) in an oil pan, oil is sucked into the pump chamber due to pumping action of the upstream pump unit (the upstream inner rotor and the upstream outer rotor), and then, the sucked air-mixed oil is returned to the oil pan as being ejected outside through the ejection port while being pressurized. Subsequently, remaining oil is pressurized to predetermined pressure (e.g., 3.0 MPa) and supplied from the upstream pump unit to the downstream pump unit (the downstream inner rotor and the downstream outer rotor) through the communication port. Subsequently, the oil is sucked into the pump chamber of the downstream pump unit with pumping action thereof and is further pressurized to predetermined pressure (e.g., 6.0 MPa). Then, the oil is discharged outside through the discharge port toward various lubrication areas.
Here, the ejection port for ejecting air-mixed oil is formed as being faced to the upstream pump unit at the first stage. Since the density (mass) of the air (bubble) mixed with the oil is small, air is easily collected at the inner side of the pump chamber by the action of centrifugal separation. Accordingly, mixed air can be effectively ejected.
In the above structure, the upstream pump unit may be configured to have a discharge rate being larger than a discharge rate of the downstream pump unit.
According to the above, since the discharge rate of the upstream pump unit to which the ejection port is faced is larger than the discharge rate of the downstream pump unit, oil can be discharged at a desired discharge rate from the downstream pump unit even when air-mixed oil is discharged through the ejection port.
In the above structure, the upstream pump unit may have a discharge rate equal to a sum of a discharge rate of the downstream pump unit and an ejection rate ejected through the ejection port.
According to the above, since the discharge rates of the upstream pump unit and the downstream pump unit are set in consideration of the return rate (ejection rate) to be returned to the oil pan through the ejection port, oil can be supplied (discharged) outside at the desired discharge rate while achieving high pressurization with two-stage pressurizing action.
In the above structure, the ejection rate ejected through the ejection port may be set to be 20% or more of the discharge rate of the upstream pump unit.
According to the above, air (bubble) mixed with oil in the suction process of the upstream pump unit can be ejected more effectively.
In the above structure, the upstream pump unit may be configured to have a thickness in the axis line direction being larger than a thickness of the downstream pump unit in the axis line direction.
According to the above, the discharge rate of the upstream pump unit can be easily set to be larger than the discharge rate of the downstream pump unit while basic specifications of the upstream inner rotor and the upstream outer rotor are kept the same as those of the downstream inner rotor and the downstream outer rotor only by differentiating the thicknesses thereof in the axis line direction.
The housing may include a housing body which includes a concave portion for containing the upstream pump unit and the downstream pump unit, a partition member which is interposed between the upstream pump unit and the downstream pump unit, and a housing cover with which the housing body is covered.
According to the above, desired pumping characteristics can be ensured while achieving downsizing. Further, assembling operation can be easily performed such that the upstream pump unit, the partition member, and the downstream pump unit are contained in the housing body and that the housing cover is attached thereon.
In the above structure, the ejection port may be arranged at the housing cover, the communication port may be arranged at the partition member, and the inlet port may be arranged at the partition member at a position opposite to the ejection port in the axis line direction as sandwiching the upstream pump unit.
According to the above, oil sucked through the inlet port can be reliably pressurized in the upstream pump unit while ejecting mixed air through the ejection port, and then, remaining pressurized oil can be supplied to the downstream pump unit through the communication port. As a whole, pumping performance can be improved.
In the above structure, each of the upstream pump unit and the downstream pump unit is a trochoid type having four blades and five nodes with the inner rotor and the outer rotor.
According to the above, a desired high discharge rate can be ensured while effectively ejecting mixed air. Accordingly, pumping performance and durability can be improved.
According to the oil pump having the above structure, desired pumping performance can be ensured even if air or the like is mixed with oil to be sucked and pumping characteristics having desired high discharge pressure (discharge rate) can be obtained.
These and/or other aspects and advantages will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:
In the following, embodiments of the present invention will be described with reference to the attached drawings.
As illustrated in
Here, the rotor case 40 and the side plate 50 are formed separately from the housing H and constitute a part of the housing H for containing the upstream pump unit 70 and the downstream pump unit 80.
The housing body 10 is made of aluminum material for weight saving and is configured to form a concave portion for containing the upstream pump unit 70 and the downstream pump unit 80 along with the rotor case 40. As illustrated in
The housing cover 20 is made of aluminum material the same as the housing body 10 for weight saving. As illustrated in
The housing cover 20 is joined to the joint face 17 while a positioning pin fitted into the positioning hole 19 is fitted into the positioning pin 26 and a positioning pin fitted into a positioning hole 45a of the rotor case 40 is fitted into the positioning hole 27. Then, the housing cover 20 is fixed to the housing body 10 by screwing the bolts B into the screw holes 18 as passing through the circular holes 25 from the outer side. Thus, the housing cover 20 closes opening of the housing body 10.
As illustrated in
As described above, the ejection port 24 for ejecting air-mixed oil is formed as being faced to the upstream pump unit 70 at the first stage. Since density (mass) of air (bubble) mixed with oil is small, air is easily collected at the inner side of a pump chamber P by the action of centrifugal separation. Accordingly, mixed air can be effectively ejected.
Here, the ejection port 24 is not limited to have the abovementioned shape. It is also possible to adopt an appropriate shape in accordance with a target ejection rate of air-mixed oil.
As illustrated in
The rotor case 40 is made of steel, casting iron, sintered steel, or the like. As illustrated in
The cylindrical portion 41 is formed to have an outer diameter dimension so that the cylindrical portion 41 is fitted into the housing body 10 as being capable of relatively moving in the direction of the axis line S in accordance with difference between thermal deformation (expansion and contraction) amounts of the housing body 10 and the rotor case 40 while being intimately contacted to the inner circumferential face of the housing body 10.
The inner circumferential face 42 is formed to have a dimension so that the first outer rotor 72 of the upstream pump unit 70 is in contact with the inner circumferential face 42 rotatably (slidably) about the axis line L1.
The inner circumferential face 43 is formed to have a dimension so that the second outer rotor 82 of the downstream pump unit 80 is in contact with the inner circumferential face 43 rotatably (slidably) about the axis line L2.
The inlet port 44b is formed so as to be faced to a pump chamber P of the upstream pump unit 70 while communicating with the inlet passage 14.
Thus, the inlet port 44b is arranged at the middle wall portion 44 as being located at the opposite side to the ejection port 24 while sandwiching the upstream pump unit 70 in the direction of the axis line S. Accordingly, oil sucked through the inlet port 44b can be reliably pressurized in the upstream pump unit 70 and is supplied to the downstream pump unit 80 through the communication port 44e. As a whole, pumping performance can be improved.
The communication port 44e is configured to cause communication between the upstream discharge port 44c and the downstream inlet port 44d so that oil discharged from the upstream pump unit 70 is introduced to the downstream pump unit 80.
The rotor case 40 is assembled (fitted) to the inner circumferential face 12 of the housing body 10 in a state of containing the upstream pump unit 70 at the inner circumferential face 42 and the downstream pump unit 80 at the inner circumferential face 43 along with the rotary shaft 30 while the positioning pin fitted into the positioning hole 16 is fitted into the positioning hole 46a as sandwiching the O-ring 60 and the side plate 50 in cooperation with the end face 13.
The side plate 50 is formed disc-shaped and is made of steel, casted iron, sintered steel, aluminum alloy, or the like. As illustrated in
The side plate 50 is configured to be assembled to the housing body 10 as sandwiching the O-ring 60 at a space against the end face 13 while positioning pin fitted into the positioning hole 16 of the housing body 10 passes through the positioning hole 53.
The O-ring 60 is formed circularly of elastically-deformable rubber material or the like and is arranged between the end face 13 of the housing body 10 and the side plate 50. The fi-ring 60 is assembled as being compressed by a predetermined compression amount in the direction of the axis line S to urge the side plate 50 toward the end face 46 of the rotor case 40.
The upstream pump unit 70 is made of steel, sintered steel, or the like. As illustrated in
The first inner rotor 71 is formed as an external gear which has four crests (external teeth) and roots (cavities) while including a fitting hole 71a into which the shaft portion 33 of the rotary shaft 30 is fitted.
The first outer rotor 72 is formed as an internal gear which has five crests (inner teeth) and roots (cavities) to be engaged with the four crests (external teeth) and roots (cavities) of the first inner rotor 71 at the inner circumference thereof while including an outer circumferential face 72a which is slidably fitted to the inner circumferential face 42 of the rotor case 40.
When the first inner rotor 71 is rotated along with the rotary shaft 30 in an arrow direction about the axis line S (counterclockwise in
The downstream pump unit 80 is made of steel, sintered steel, or the like. As illustrated in
The second inner rotor 81 is formed as an external gear which has four crests (external teeth) and roots (cavities) while including a fitting hole 81a into which the shaft portion 34 of the rotary shaft 30 is fitted.
The second outer rotor 82 is formed as an internal gear which has five crests (inner teeth) and roots (cavities) to be engaged with the four crests (external teeth) and roots (cavities) of the second inner rotor 81 at the inner circumference thereof while including an outer circumferential face 82a which is slidably fitted to the inner circumferential face 43 of the rotor case 40.
When the second inner rotor 81 is rotated along with the rotary shaft 30 in an arrow direction about the axis line S (clockwise in
The above structure is configured to satisfy an expression of “Qu=Qd+Qe” while Qu, Qd, and Qe denote a discharge rate (suction rate) of the upstream pump unit 70, a discharge rate (suction rate) of the downstream pump unit 80, and an ejection rate (of air-mixed oil) ejected through the ejection port 24, respectively.
In this manner, since the discharge rates Qu, Qd are set in consideration of the return rate (ejection rate Qe) to be returned to an oil pan OP through the ejection port 24, oil can be supplied (discharged) outside at the desired discharge rate Qd while achieving high pressurization with two-stage pressurizing action.
Here, it is preferable that the ejection rate Qe ejected through the ejection port 24 is set in a range between 20% and 50% inclusive of the discharge rate Qu of the upstream pump unit 70.
With the above, air (bubble) mixed with oil in the suction process of the upstream pump unit 70 can be ejected more effectively.
Further, as illustrated in
Owing to arrangement of the thicknesses Wu, Wd in the direction of the axis line S, the discharge rate Qu of the upstream pump unit 70 can be easily set to be larger than the discharge rate Qd of the downstream pump unit 80 while basic specifications of the upstream inner rotor 71 and the upstream outer rotor 72 are kept the same as those of the downstream inner rotor 81 and the downstream outer rotor 82.
In a case that the oil pump having the above structure is mounted on an engine with the oil pan OP, as illustrated in
In the above structure, the housing body 10 and the housing cover 20 form the housing H and the rotor case 40 defining the middle wall portion 44 as the partition member separately contains the upstream pump unit 70 and the downstream pump unit 80 in advance. Accordingly, for assembling the oil pump, it is only required to place the upstream pump unit 70 and the downstream pump unit 80 into the rotor case 40 along with the rotary shaft 30, to sequentially place the O-ring 60, the side plate 50, and the rotor case 40 into the housing body 10, and then, to attach the housing cover 20 thereon. In this manner, assembling operation can be easily performed.
Next, operation of the oil pump will be described with reference to
First, when the rotary shaft 30 is rotationally driven by an engine, the upstream pump unit 70 (the first inner rotor 71 and the first outer rotor 72) is rotated counterclockwise in
Owing to continuous rotation of the upstream pump unit 70, the oil sucked into the pump chamber P is pressurized. In the pressurization process, air-mixed oil is forcedly ejected outside through the ejection port 24 at the predetermined ejection rate Qe. Further, the remaining oil (Qu−Qe) obtained by subtracting the ejection rate Qe from the discharge rate Qu is discharged (supplied) as being pressurized to predetermined discharge pressure (about 3.0 MPa) toward the downstream pump unit 80 through the upstream discharge port 44c, the communication port 44e, and the downstream inlet port 44d.
Subsequently, the oil is sucked into the pump chamber P of the downstream pump unit 80 through the downstream inlet port 44d with clockwise rotation in
Owing to continuous rotation of the downstream pump unit 80, the oil sucked into the pump chamber P is pressurized and discharged (supplied) toward an external lubrication area through the discharge port 52 and the discharge passage 15 at predetermined discharge pressure (about 6.0 MPa) and the predetermined discharge rate (discharge rate Qd).
Practically, cooperative action of the upstream pump unit 70 (the first inner rotor 71 and the first outer rotor 72) and the downstream pump unit 80 (the second inner rotor 81 and the second outer rotor 82) causes continuously operation of a series of processes, that is, sucking oil from the oil pan OP at the first stage, pressurizing oil at the first stage, ejecting mixed air and oil (air-mixed oil) at the first stage, discharging remaining oil at the first stage toward the downstream side (sucking oil at the second stage), pressurizing oil at the second stage, and discharging oil at the second stage.
In this manner, air (bubble) mixed with oil is ejected along with oil (as air-mixed oil) through the ejection port 24 which is faced to the upstream pump unit 70 at the first stage. Since density (mass) of the air (bubble) mixed with oil is small, air is easily collected at the inner side of the pump chamber P by the action of centrifugal separation. Accordingly, mixed air can be effectively ejected. Further, since the discharge rates Qu, Qd are set in consideration of the return rate (ejection rate Qe) to be returned to the oil pan OP through the ejection port 24, oil can be supplied (discharged) outside at the desired discharge rate Qd while achieving high pressurization with two-stage pressurizing action.
In the description of the above embodiment, the present invention is applied to the structure in which the rotor case 40 and the side plate 50 are arranged at the inside of the housing H (the housing body 10 and the housing cover 20) as a second housing. However, not limited to the above, the present invention may be applied to a structure without including the rotor case 40 and the side plate 50.
In the description of the above embodiment, the present invention is applied to the two-stage trochoid pump which includes the upstream pump unit 70 (the first inner rotor 71 and the first outer rotor 72) and the downstream pump unit 80 (the second inner rotor 81 and the second outer rotor 82). However, not limited to the above, the present invention may be applied to a structure including an inner rotor and an outer rotor of an internal gear type (involute type).
In the description of the above embodiment, the present invention is applied to a structure in which the housing H is separated into the housing body 10 and the housing cover 20. However, not limited to the above, the present invention may be applied to a structure in which a housing includes a first housing half body and a second housing half body which define a concave portion respectively.
In the description of the above embodiment, the oil pump of the present invention is adopted to an engine which is mounted on an automobile or the like. However, not limited to the above, an oil pump of the present invention may be adopted to a continuously variable transmission (CVT) or the like other than an engine.
As described above, according to an oil pump of the present invention, desired pumping performance can be ensured even if air or the like is mixed with oil to be sucked and pumping characteristics having desired high discharge pressure (discharge rate) can be achieved. Accordingly, in addition to be naturally adopted to an engine which is mounted on an automobile or the like, an oil pump of the present invention is useful for motorcycles, other vehicles having an engine mounted, continuously variable transmissions (CVTs) and other mechanisms requiring pressured feeding of lubricant oil, and the like.
Although a few embodiments have been shown and described, it would be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2012-095390 | Apr 2012 | JP | national |
