Patent Application
20060207537
This application is based on and claims priority under 35 U.S.C. ยง 119 to Japanese Patent Application Nos. 2005-072492 and 2005-198191, filed on Mar. 15, 2005 and Jul. 7, 2005 respectively, the entire content of which is incorporated herein by reference.
This invention generally relates to a variable valve timing control device. More particularly, the present invention pertains to a variable valve timing control device for controlling an opening and closing timing of an intake valve and an exhaust valve of an internal combustion engine.
In recent years, a variable valve timing control device is assembled on one end of a camshaft so as to control an opening and closing timing of an intake valve and an exhaust valve in response to an operation state of an internal combustion engine. In addition, engine accessories such as a vacuum booster and a fuel pump, i.e. a driven unit, are also assembled on one end of the camshaft for the purposes of reducing an overall height of the engine.
As a power transmission system to the driven unit, JP2001-263025A discloses a driving unit for driving a fuel pump by a camshaft of an internal combustion engine as a driving shaft of the fuel pump is connected to one end of the camshaft by means of an Oldham's coupling. According to the driving unit disclosed, a pump-side coupling is arranged between a coupling member constituting the Oldham's coupling and the driving shaft of the fuel pump for the purposes of performing a power transmission to the driving shaft of the fuel pump.
However, since the pump-side coupling is arranged between the coupling member and the driving shaft of the fuel pump and fixed by a nut, the number of parts is increased and the assembly is thus complicated. In addition, the arrangement of the pump-side coupling may cause a long installation length of the driven unit. Thus, flexibility of installation of the driven unit may be decreased. Further, an entire length of the engine may be increased, which leads to a reduction of mounting flexibility of the engine.
Furthermore, a separate assembly of a variable valve timing control device and the driven unit on the camshaft may cause a complicated process and an increase of a size, which leads to a further reduction of mounting flexibility of the engine.
In order to solve the aforementioned problems, Japanese Patent Application No. 2003-305694 filed on Mar. 24, 2005 discloses, for the purposes of achieving a reduction of entire length of a driving member and a simplified assembly, a variable valve timing control device in which an engaging groove engageable with a coupling member that is connected to a driven unit is formed on axially one end of a plate consisting of a housing member of the variable valve timing control device.
However, in view of abrasion resistance of the engaging groove, since iron sintered alloy having a high specific gravity is used for the plate, a rotational inertia force of the plate is increased, which may lead to deterioration of rotational responsiveness of the camshaft. In addition, since a rotational fluctuation of the camshaft is increased, adverse affect such as acceleration of abrasion of a bearing portion of the camshaft may occur.
Thus, a need exists for a variable valve timing control device in which a rotational inertia force of a plate can be reduced so as to enhance a rotational responsiveness of a camshaft and durability of a bearing portion of the camshaft.
According to an aspect of the present invention, a variable valve timing control device includes a housing member integrally rotating with one of a crankshaft and a camshaft of an internal combustion engine, a rotor member assembled on the housing member so as to rotate relative thereto and integrally rotating with the other one of the crankshaft and the camshaft, a vane provided on the rotor member so as to integrally rotate therewith, a fluid pressure chamber formed between the housing member and the rotor member and divided into an advanced angle chamber and a retarded angle chamber by the vane, a lock mechanism for restricting a relative rotation between the housing member and the rotor member by a lock member movably provided on the housing member to be inserted into a lock groove formed on the rotor member, and for allowing the relative rotation between the housing member and the rotor member by the lock member to be retracted from the lock groove, a fluid pressure circuit for controlling an operation fluid to be supplied to or discharged from the advanced angle chamber, the retarded angle chamber, and the lock mechanism, a plate provided on an axially one end side of the housing member and integrally rotating with the housing member, an engaging groove formed on an axially one end side of the plate, and a contacting member arranged in the engaging groove so as to rotate integrally with the plate and engaging with a coupling member so as to be assembled thereon.
The foregoing and additional features and characteristics of the present invention will become more apparent from the following detailed description considered with reference to the accompanying drawings, wherein:
A first embodiment of the present invention is explained with reference to FIGS. 1 to 4.
As shown in FIGS. 1 to 4, a variable valve timing control device 1 includes a rotor member 2 for opening or closing a valve that consists of a camshaft 10 rotatably supported on a cylinder head 100 of an internal combustion engine and a rotor 20 integrally fixed to a tip end portion of the camshaft 10. The variable valve timing control device 1 also includes a housing member 3 that consists of a housing 30 being rotatable relative to the rotor 20 within a predetermined range, a front plate 40, and a rear plate 50. Then, a timing sprocket 31 is integrally formed on an outer periphery of the housing 30. Further, the variable valve timing control device 1 includes a torsion spring 60 disposed between the rotor 20 and the front plate 40, five vanes 70 assembled on the rotor 20, a lock key (lock member) 80 assembled on the housing 30, and the like. A vacuum pump (driven unit) 300 is connected to an axially one end (left side in
The timing sprocket 31 receives a rotation force in a clockwise direction thereof, which is shown as a rotation direction of the camshaft 10 in
The camshaft 10 includes a known cam (not shown) for opening or closing an exhaust valve (not shown). A retarded angle fluid passage (fluid circuit) 11 and an advanced angle fluid passage (fluid circuit) 12 extending in an axial direction of the camshaft 10 are formed inside of the camshaft 10. The retarded angle fluid passage 11 is connected to a second connecting port 202 of a switching valve 200 through a passage 71 provided on the camshaft 10 in a radial direction thereof, an annular groove 14 provided on the camshaft, and a connecting passage 16 provided on the cylinder head 100. In addition, the advanced angle fluid passage 12 is connected to a first connecting port 201 of the switching valve 200 through a passage 72 provided on the camshaft 10 in the radial direction thereof, an annular groove 13 provided on the camshaft 10, and a connecting passage 15 provided on the cylinder head 100.
The switching valve 200 has a known structure in which a spool 204 is moved against a biasing force of a spring (not shown) by energizing a solenoid 203. When the solenoid 203 is energized, as shown in
The rotor 20 is integrally fixed to the camshaft 10 with a single installation bolt 95 that penetrates through a through-hole 20a formed on an axial center of the rotor 20 for the purposes of forming the rotor member 2. A front end (i.e. left side in
The housing member 3 is constituted such that one side of the housing 30 in the axial direction thereof is integrally fixed to the front plate 40 while the other side of the housing 30 in the axial direction there of is integrally fixed to the rear plate 50. The housing 30, the front plate 40, and the rear plate 50 are connected with six connecting bolts 90. The housing 30 is assembled on an outer periphery of the rotor 20 so as to be rotatable relative thereto within a predetermined angle range. The vacuum pump 300 is connected to an axially one end (left side in
The timing sprocket 31 is integrally formed on the outer periphery of the housing 30. Five protruding portions 33 are formed on an inner periphery of the housing 30. An inner peripheral face of each protruding portion 33 is slidably in contact with an outer peripheral face of the rotor 20. That is, the housing 30 is rotatably supported on the rotor 20. A retracting groove 34 for accommodating the lock key 80, and a receiving hole 35 connected to the retracting groove 34 for accommodating a coil spring 81 that biases the lock key 80 in the radially inward direction of the housing 30 are formed on one of the protruding portions 33.
A cylindrical portion 41 having a substantially cylindrical shape is formed on axially one end side of the front plate 40 as shown in
As shown in
The clip 45 has a tapered shape whose width is gradually decreased towards a bottom portion from an opening side, and forms a tapered gap 46 with the engaging groove 42. A width of the tapered gap 46 is gradually increased towards the bottom portion thereof. Further, a hook portion 45a is formed on the clip 45 in such a manner that respective side portions of the clip 45 provided on the bottom side thereof are expanded as shown in
Each vane 70 divides a fluid pressure chamber R0, which is formed between the housing 30 and the rotor 20 and also between the protruding portions 33 adjacent to each other in the circumferential direction, into an advanced angle chamber R1 and a retarded angle chamber R2. The relative rotation between the rotor 20 and the housing 30 on the most advanced angle side is restricted at a position where the vane 70, i.e. a vane 70a in
One end of the torsion spring 60 engages with the front plate 40 while the other end engages with the rotor 20. The torsion spring 60 biases the inner rotor 20 towards the advanced angle side (clockwise direction in
According to the present embodiment, as shown in
Next, a second embodiment is explained with reference to FIGS. 5 to 11.
According to the variable valve timing control device 1 of the second embodiment, the cylindrical portion 41 having a substantially cylindrical shape and on which the engaging groove 42 engaging with the coupling member 310 connected to the vacuum pump 300 is formed on one end side of the front plate 40. Then, the plane portions 41a are formed on the respective sides of the cylindrical portion 41 such that the plane portions 41a are in parallel with the engaging groove 42 and the rotational axis of the front plate 40.
An assembly method of the variable valve timing control device 1 according to the second embodiment is explained below.
As shown in
Next, a positioning jig J2 for the rotor 20 having a shaft portion 501 closely made contact with a center bore 20c of the rotor 20 is inserted into the center bore 20c. The jig J2 includes a center bore 502 having a diameter specified such that the center bore 502 is closely made contact with the small diameter shaft portion 401 of the jig J1.
The small diameter shaft portion 401 of the jig J1 is inserted from a side of the front plate 40 into the center bore 502 of the jig J2 while the plane portions 403a of the jig J1 and the plane portions 41a of the front plate 40 are closely made contact with each other. Then, the front plate 40 and the rear plate 50 are fully tightened by the bolts 90. A desired accuracy of eccentricity between the center bore 20c of the rotor 20 and the engaging groove 42 can be obtained. As a result, an eccentric error between a center line of the engaging groove 42 and an axial center of the camshaft 10 as a driving shaft may be reduced, which can prevent increase of rotational fluctuation or noise occurrence.
Further, by the assembly of the clip 45 on the front plate 40 beforehand, foreign substance such as metal powder that may be generated at a time of assembly of the clip 45 on the front plate 40 is prevented from being mixed into the variable valve timing control device 1.
According to the second embodiment, the plane portions 41 a in parallel with the engaging groove 42 are formed on the respective sides of the cylindrical portion 41 formed on one end of the front plate 40, and then the jig J1 having the planes, i.e. the plane portions 403a, closely made contact with the plane portions 41a are used. At this time, alternatively, after the clip 45 is assembled on the engaging groove 42 whose axial length is longer than that of the clip 45, a jig J3 having a protruding portion that is closely made contact with an axially end side of the engaging groove 42 may be used for assembly as shown in
An operation of the variable valve timing control device 1 having the aforementioned structure is explained below. When the internal combustion engine is stopped, the oil pump 205 is stopped and also the switching valve 200 is not energized. Thus, the operation fluid is not supplied to the fluid pressure chambers R0. At this time, as shown in
When the retarded angle phase is required for the valve timing depending on the operation condition of the internal combustion engine, the duty ratio for energizing the switching valve 200 is brought to be large and then the position of the spool 204 is switched. The operation fluid supplied from the oil pump 205 is provided to the retarded angle chamber R2 by passing through the connecting passage 16, and the retarded angle fluid passages 11, 20b and 23. At the same time, the operation fluid is supplied to the lock groove 22 through a lock fluid passage 28 and then led to a head portion 80a of the lock key 80. Therefore, fluid pressure is applied to the head portion 80a of the lock key 80 so that the lock key 80 is retracted from the lock groove 22. The relative rotation between the housing 30 and the rotor 20 is permitted accordingly. Meanwhile, the operation fluid stored in the advanced angle chamber R1 is sent to the advanced angle fluid passages 24 and 12, and the connecting passage 15 to be discharged from the discharge port 207 of the switching valve 200. The rotor 20 is rotated relative to the housing 30 in the retarded angle direction accordingly. The side face 33b of the protruding portion 33 of the housing 30 and the side face of the vane 70b are made contact with each other so as to restrict the rotation of the rotor 20 relative to the housing 30 in the advanced angle direction.
When the advanced angle phase is required for the valve timing depending on the operation condition of the internal combustion engine, the duty ratio for energizing the switching valve 200 is brought to be small and then the position of the spool 204 is switched. The operation fluid supplied from the oil pump 205 is provided to the advanced angle chamber R1 by passing through the connecting passage 15, and the advanced angle fluid passages 12 and 24. Meanwhile, the operation fluid stored in the retarded angle chamber R2 is sent to the retarded angle fluid passages 23 and 11, and the connecting passage 16 to be discharged from the discharge port 207 of the switching valve 200. The rotor 20 is rotated relative to the housing 30 in the advanced angle direction accordingly. The side face 33a of the protruding portion 33 of the housing 30 and the side face of the vane 70aare made contact with each other so as to restrict the rotation of the rotor 20 relative to the housing 30 in the retarded angle direction. When the operation fluid is discharged from the lock groove 22, the lock key 80 movably arranged on the housing 30 is inserted into the lock groove 22, thereby restricting the relative rotation between the housing 30 and the rotor 20.
During the operation of the combustion engine, the vacuum pump 300 is rotatably driven by the coupling member 30, which engages with the engaging groove 42 of the front plate 40 by means of the clip 45. At this time, a relative sliding is possibly generated between the clip 45 and the coupling member 310 because of a positional difference between a rotation center of the vacuum pump 300 and that of the front plate 40. However, the bent portions 45d formed on both radially end portions of the clip 45 are caught by the end faces of the engaging groove 42, and thus the clip 45 is prevented from moving. Further, a hitting sound generated between the coupling member 310 and the engaging groove 42 upon rotation fluctuation of the camshaft 10 is absorbed by the tapered gap 46 formed between the engaging groove 42 and the clip 45. The operation noise of the variable valve timing control device 1 can be thus reduced.
According to the aforementioned embodiments, the coupling member 310 of the vacuum pump 300 is connected to the front plate 40 by means of the clip 45. Thus, consideration of abrasion resistance of the front plate 40 may not be required. Material used for the front plate 40 is selectable accordingly. Since the front plate 40 can be made of relatively lightweight material, the rotational inertia force of the front plate 40 may be reduced, thereby enhancing the rotational responsiveness of the camshaft 10 and the durability of a bearing portion of the camshaft 10. Further, the rotational fluctuation of the camshaft 10 may be reduced to thereby enhance the durability of the bearing portion of the camshaft 10.
Furthermore, according to the aforementioned embodiments, the clip 45 may be formed easily and at a low cost, such as by press molding. In addition, a pressing direction of the clip 45 can be arranged on the engaging groove 42 side, which may cause an edge portion formed at a time of pressing of the clip 45 to enter into a side face of the engaging groove 42 so as to prevent the clip 45 from disengaging from the engaging groove 42.
Furthermore, according to the aforementioned embodiments, the clip 45 is made of stainless spring steel, for example. Thus, rust is not generated upon shipment and rust prevention is not required.
Furthermore, according to the aforementioned embodiments, the plane portions 41a are formed on the front plate 40 so as to be parallel with the rotational axis thereof. Thus, the front plate 40 can be assembled on the basis of the plane portions 41a. The eccentric error between the center line of the engaging groove 42 and the axial center of the camshaft 10 can be reduced and also the engaging groove 42 is prevented from being damaged upon assembly.
Accordingly, a smooth rotation of the camshaft 10 and reduction of the operation noise of the variable valve timing control device 1 can be achieved, which may contribute to a long lifetime of the coupling member 310.
Furthermore, according to the aforementioned embodiments, the plane portions 41a are in parallel with the engaging groove 42. Thus, the eccentric error between the center line of the engaging groove 42 and the axial center of the camshaft 10 may be further reduced.
The principles, preferred embodiment and mode of operation of the present invention have been described in the foregoing specification. However, the invention which is intended to be protected is not to be construed as limited to the particular embodiments disclosed. Further, the embodiments described herein are to be regarded as illustrative rather than restrictive. Variations and changes may be made by others, and equivalents employed, without departing from the spirit of the present invention. Accordingly, it is expressly intended that all such variations, changes and equivalents which fall within the spirit and scope of the present invention as defined in the claims, be embraced thereby.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2005-072492 | Mar 2005 | JP | national |
| 2005-198191 | Jul 2005 | JP | national |
