VALVE TIMING CONTROL APPARATUS

CROSS REFERENCE TO RELATED APPLICATION

This application is based on and incorporates herein by reference Japanese Patent Application No. 2007-239492 filed on Sep. 14, 2007.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a valve timing control apparatus, which changes valve timing of at least one of an intake valve and an exhaust valve of an internal combustion engine.

2. Description of Related Art

A previously proposed vane type valve timing control apparatus opens and closes at least one of an intake valve and an exhaust valve by driving a camshaft (a follower shaft) through a timing pulley and a chain sprocket, which are rotated synchronously with a crankshaft of the engine, through use of a phase difference caused by relative rotation between the timing pulley or the chain sprocket and the camshaft (see, for example, Japanese Patent No. 3567551).

In the previously proposed vane type valve timing control apparatus, a clearance is provided between a vane rotor and a housing member to receive the vane rotor in the housing member in a manner that enables relative rotation between the vane rotor and the housing member. At the time of assembling the vane rotor with, for example, bolts, the vane rotor may possibly be deformed to cause warping or bending of the vane rotor. Therefore, the clearance between the vane rotor and the housing member is set to have a predetermined axial width in view of the warping, bending or the like. Furthermore, a seal member is provided between an axial end surface of the vane rotor and the housing member to reduce leakage of oil (hydraulic fluid) through the clearance.

However, due to the presence of the clearance between the vane rotor and the housing member, the housing member may possibly be axially moved relative to the vane rotor at the time of rotating the engine in some cases. In such a case, a relative axial position of the housing member relative to the vane rotor is not kept constant, and thereby the axial width of the clearance changes from time to time. When this happens, the clearance may not be sufficiently closed with the seal member, and thereby the leakage of the oil may not be reduced.

SUMMARY OF THE INVENTION

The present invention addresses the above disadvantages. Thus, it is an objective of the present invention to provide a valve timing control apparatus, which minimizes leakage of hydraulic fluid and controls a phase of a follower shaft with relatively high accuracy through use of a relatively simple structure.

In order to achieve the objective of the present invention, there is provided a valve timing control apparatus for an internal combustion engine. The valve timing control apparatus includes a follower shaft, a drive force transmitting member, a gear, a housing member, a vane rotor and a seal member. The follower shaft drives at least one of an intake valve and an exhaust valve of the internal combustion engine to open and close the at least one of the intake valve and the exhaust valve. The drive force transmitting member transmits a drive force from a drive shaft of the internal combustion engine to the follower shaft. The gear is engaged with the drive force transmitting member and receives the drive force from the drive force transmitting member to rotate synchronously with the drive shaft. The housing member has an outer peripheral wall, along which the gear extends annularly to rotate integrally with the housing member. The vane rotor includes a supporting portion and a vane. The vane is rotated together with the supporting portion, which is in turn rotated together with the follower shaft. The vane is received in a receiving chamber formed in the housing member and is rotatable relative to the housing member only within a predetermined angular range. The seal member is placed at one axial end surface of the vane rotor and is held between the vane rotor and the housing member. The supporting portion of the vane rotor includes a tapered outer wall surface, which is tilted relative to an axis of the supporting portion. The housing member includes a tapered inner wall surface that contacts the tapered outer wall surface of the supporting portion. The seal member is provided at the one axial end surface of the vane rotor on one axial side of the vane rotor, toward which the vane rotor urges the housing member by an interaction between the tapered outer wall surface of the supporting portion and the tapered inner wall surface of the housing member.

The seal member may limit leakage of hydraulic fluid from a hydraulic chamber, which is defined in the receiving chamber and receives the hydraulic fluid to exert a hydraulic pressure to drive the vane in a circumferential direction.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention, together with additional objectives, features and advantages thereof, will be best understood from the following description, the appended claims and the accompanying drawings in which:

FIG. 1 is a schematic diagram showing a valve timing control apparatus and oil passages thereof according to a first embodiment of the present invention;

FIG. 2 is a schematic cross sectional view showing components of the valve timing control apparatus according to the first embodiment with slight exaggeration of some of the components;

FIG. 3 is a schematic diagram showing a drive force transmitting member placed around the valve timing control apparatus according to the first embodiment;

FIG. 4 is a cross sectional view taken along line IV-IV in FIG. 1;

FIG. 5 is a front view of a seal member of the valve timing control apparatus according to the first embodiment;

FIG. 6 is a view seen from a direction of VI in FIG. 5;

FIG. 7 is a schematic view showing an installed state of the seal member to the valve timing control apparatus shown in FIG. 4;

FIG. 8 is a cross sectional view showing a valve timing control apparatus according to a second embodiment of the present invention; and

FIG. 9 is a cross sectional view showing a valve timing control apparatus according to a third embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention will be described with reference to the accompanying drawings.

First Embodiment

FIGS. 1 to 7 show a valve timing control apparatus according to a first embodiment of the present invention. The valve timing control apparatus 10 is of a hydraulically controlled type, which uses hydraulic oil as working fluid (hydraulic fluid) and which adjusts the valve timing of intake valves.

As shown in FIG. 1, the valve timing control apparatus 10 includes a housing 11 (serving as a housing member) and a vane rotor 50. The housing 11 includes a front plate housing 20, a shoe housing 30, and a plate housing 40. The front plate housing 20, the shoe housing 30, and the plate housing 40 are coaxially secured with bolts 12. A gear 13 is provided in an outer peripheral wall of the shoe housing 30.

As shown in FIG. 3, a chain 7 is wound around the gear 13 of the housing 11, a gear 8 and a gear 9. The gear 8 is coaxially fixed to a crankshaft (not shown). The gear 9 is coaxially fixed to a camshaft, which drives exhaust valves (not shown) to open and close the same. The chain 7, which serves as a drive force transmitting member, is engaged with the gear 13. The housing 11 is connected to the crankshaft (serving as a drive shaft of the engine) with the chain 7 through the gear 8. In this way, the housing 11 receives a drive force from the crankshaft and is rotated synchronously with the crankshaft. As shown in FIG. 3, the housing 11 is rotated in the clockwise direction.

With reference to FIG. 1, another camshaft 15, which serves as a follower shaft, receives the drive force of the crankshaft through the housing 11. The camshaft 15 drives intake valves (not shown) to open and close the same. The camshaft 15 is received in the plate housing 40 in such a manner that the camshaft 15 and the plate housing 40 are driven to rotate together by the drive force transmitted from the crankshaft while the camshaft 15 is rotatable relative the plate housing 40 within a predetermined range of a phase difference at the time of changing the phase difference of the camshaft 15 relative to the plate housing 40. A portion of the camshaft 15, which is received in the plate housing 40, has an outer diameter that is slightly smaller than an inner diameter of the plate housing 40.

The vane rotor 50 axially contacts an axial end surface of the camshaft 15. The camshaft 15 and the vane rotor 50 are coaxially fixed with a bolt 14. The positioning between the vane rotor 50 and the camshaft 15 in the rotational direction is implemented by fitting a positioning pin (not shown) into the vane rotor 50 and the camshaft 15. With the above described construction, the vane rotor 50 and the camshaft 15 are coaxially rotatable relative to the housing 11. The camshaft 15, the housing 11 and the vane rotor 50 are rotated in a clockwise direction when they are viewed in a direction of an arrow X shown in FIG. 1. Hereinafter, this rotational direction will be referred to as an advancing direction of the camshaft 15 relative to the crankshaft.

As shown in FIG. 4, the shoe housing 30 of the housing 11 includes a tubular peripheral wall 31 and shoes 32-35. The shoes 32-35 extend radially inwardly from the peripheral wall 31. The shoes 32-35 are formed generally in a trapezoidal shape and are arranged one after another at generally equal intervals in the rotational direction of the peripheral wall 31. The shoes 32-35 form four fan shaped receiving chambers 36, each of which extends a predetermined angular extent in the rotational direction and receives a corresponding one of a plurality of vanes 52-55 of the vane rotor 50.

The vane rotor 50 has a boss portion (serving as a supporting portion) 51 and the vanes 52-55. The vanes 52-55 are arranged along an outer peripheral surface of the boss portion 51 at generally equal intervals in the rotational direction. The vane rotor 50 is received in the housing 11 in such a manner that the vane rotor 50 is rotatable relative to the housing 11. The vanes 52-55 are rotatably received in the receiving chambers 36, respectively. An axial length of the vane rotor 50 is shorter than an axial length of the shoe housing 30.

Each vane 52-55 partitions the corresponding receiving chamber 36 into a retarding hydraulic chamber and an advancing hydraulic chamber. Specifically, a retarding hydraulic chamber 81 is formed between the shoe 32 and the vane 52, and a retarding hydraulic chamber 82 is formed between the shoe 33 and the vane 53. Also, a retarding hydraulic chamber 83 is formed between the shoe 34 and the vane 54, and a retarding hydraulic chamber 84 is formed between the shoe 35 and the vane 55. Also, an advancing hydraulic chamber 91 is formed between the shoe 35 and the vane 52, and an advancing hydraulic chamber 92 is formed between the shoe 32 and the vane 53. In addition, an advancing hydraulic chamber 93 is formed between the shoe 33 and the vane 54, and an advancing hydraulic chamber 94 is formed between the shoe 34 and the vane 55.

As shown in FIGS. 1 and 4, the boss portion 51 is formed into a generally cylindrical body and includes a tapered outer wall surface 56 at a radially outer side of the boss portion 51. The tapered outer wall surface 56 is tilted relative to the axis of the boss portion 51. Specifically, an outer diameter of the tapered outer wall surface 56 increases toward a camshaft 15 side in the axial direction. A tapered inner wall surface 37 is formed in a boss portion 51 side part (a radially inner end part) of each shoe 32-35 to contact with the tapered outer wall surface 56 of the boss portion 51. Similar to the tapered outer wall surface 56, the tapered inner wail surface 37 is tilted relative to the axis of the boss portion 51. As described above, the outer diameter of the camshaft 15 is set to be slightly smaller than the inner diameter of the plate housing 40. Accordingly, the tapered outer wall surface 56 of the boss portion 51 and the corresponding tapered inner wall surface 37 of the shoe housing 30 contact with each other at the same tilt angle, i.e., at a predetermined angle α. Thereby, the boss portion 51 serves as a bearing, which rotatably supports the housing 11.

Now, the configurations of the tapered outer wall surface 56 and of the radially opposed tapered inner wall surface 37 will be described in detail with reference to FIG. 2. For the sake of clarity, FIG. 2 shows a schematic cross-sectional view of each corresponding component, a geometric feature of which is slightly exaggerated. With reference to FIG. 2, an imaginary line L1 is drawn to extend along the tapered outer wall surface 56 and to intersect with an imaginary plane, which extends along the axis of the boss portion 51 and is parallel to the axis of the boss portion 51. This imaginary line L1 is tilted relative to the axis of the boss portion 51 by a predetermined angle α. Similarly, an imaginary line L2 is drawn to extend along the tapered inner wall surface 37 of the corresponding shoe 32-35 and to intersect with the imaginary plane, which extends along the axis of the boss portion 51 and is parallel to the axis of the boss portion 51. This imaginary line L2 is tilted relative to the axis of the boss portion 51 by the predetermined angle α. The line L1 and the line L2 intersect with the axis of the boss portion 51 on a side of the boss portion 51, which is opposite from the camshaft 15. As described above, the tapered outer wall surface 56 and the tapered inner wall surface 37 are tilted relative to the axis of the boss portion 51 at generally the same angle. Therefore, the vane rotor 50 can rotate relative to the housing 11 while the tapered outer wall surface 56 of the boss portion 51 of the vane rotor 50 slides along the tapered inner wall surface 37 of the corresponding shoe 32-35 of the shoe housing 30.

As shown in FIGS. 1 and 2, a seal member 60 is provided between the vane rotor 50 and the front plate housing 20. The seal member 60 is clamped between the front plate housing 20 and the shoe housing 30. The seal member 60 is made of metal (e.g., stainless steel) or resin. As shown in FIGS. 5 and 6, the seal member 60 is formed into a generally circular disk shape (a generally annular disk body having an outer diameter larger than that of the vane rotor 50). Furthermore, the seal member 60 has a generally annular (circular) protrusion 64, which protrudes from the rest of the seal member 60 in the axial direction. The protrusion 64 is formed, for example, by pressing a plate-shaped seal member 60 through a presswork, so that the protrusion 64 is resiliently deformable in the axial direction.

As shown in FIGS. 5 and 7, a through hole 61 extends through the seal member 60 at generally the center of the seal member 60 to receive the bolt 14 therethrough. An inner diameter of the through hole 61 is set to be slightly larger than an outer diameter of a bottom portion 142 of a head 141 of the bolt 14. Furthermore, the seal member 60 has four through holes 62, which penetrate through the seal member 60 at four locations, which correspond to four through holes 38 of the shoe housing 30. Four bolts 12 are received through the through holes 62 of the seal member 60 and the through holes 38 of the shoe housing 30. When the bolts 12 are received through the through holes 62 of the seal member 60 while the seal member 60 being clamped between the front plate housing 20 and the shoe housing 30, the seal member 60 is positioned in the circumferential position. The seal member 60 further includes through holes 63, which penetrate through the seal member 60 to conduct the oil between one axial end surface and the other axial end surface of the seal member 60.

The axial length of the vane rotor 50 is shorter than the axial length of the shoe housing 30. Thereby, an axial extent of the tapered inner wall surface 37 of the shoe housing 30, which is measured in a direction parallel to the axis of the boss portion 51, is larger than that of the tapered outer wall surface 56 of the boss portion 51, which extends continuously generally from the one end surface 57 to the other end surface 58 of the vane rotor 50. With the above construction, as shown in FIG. 2, a clearance 21 is formed between the vane rotor 50 and the front plate housing 20. The seal member 60 is provided between the vane rotor 50 and the front plate housing 20, i.e., in the clearance 21, so that the protrusion 64 of the seal member 60 slidably contacts an end surface 57 of the vane rotor 50, which is located on a front plate housing 20 side of the vane rotor 50. The protrusion 64 is resiliently deformable in the axial direction. Thereby, the protrusion 64 maintains its contact with the end surface 57 of the vane rotor 50 even when the housing 11 is moved in the axial direction relative to the vane rotor 50 to change an axial width d of the clearance 21. With this construction, the clearance 21 is closed by the seal member 60, so that leakage of the oil through the clearance 21 can be reduced. The shape of the protrusion 64 is not limited to the annular shape (circular shape) and may be changed depending on the shape of the end surface 57 of the vane rotor 50. In this way, the clearance 21 is effectively closed by the seal member 60, and thereby the leakage of the oil through the clearance 21 can be reduced.

As shown in FIG. 4, each of seal elements 16 is provided between a corresponding one of the vanes 52-55 and the peripheral wall 31 of the shoe housing 30. Each seal element 16 is fitted into a groove, which is provided in the outer peripheral wall of the corresponding one of the vanes 52-55, each seal element 16 is urged against the inner peripheral surface of the peripheral wall 31, for example, with a spring. Therefore, each seal element 16 maintains the fluidtightness between the corresponding retarding hydraulic chamber and the corresponding advancing hydraulic chamber, thereby limiting the leakage of the oil between the corresponding retarding hydraulic chamber and the corresponding advancing hydraulic chamber.

As shown in FIG. 1, a hole 521 penetrates through the vane 52 of the vane rotor 50 in the axial direction of the vane rotor 50. A disk member 522 is provided in a front plate housing 20 side part of the hole 521. The disk member 522 is formed into a generally circular disk shape and is press fitted into the hole 521, so that the disk member 522 is fixed to the vane 52. A stopper piston 100 and a spring 101 serve as a limiting member and is received in the hole 521. The stopper piston 100 is formed into a generally cylindrical shape and is reciprocally movably received in the hole 521 in the axial direction. One axial end portion of the spring 101 is in contact with the disk member 522, and the other axial end portion of the spring 101 is in contact with the stopper piston 100. The spring 101 exerts an axial resilient force. Thereby, the spring 101 urges the stopper piston 100 toward the plate housing 40 side.

An engaging ring 102, which serves as an engaging portion, is press fitted into and is held in a recess 42 formed in the plate housing 40. The stopper piston 100 is fittable (is engageable) into the engaging ring 102. The engaging sides of the stopper piston 100 and of the engaging ring 102 are tapered. Thereby, the stopper piston 100 can be smoothly fitted into the engaging ring 102. A pressure of the oil, which is supplied to a hydraulic pressure chamber 103 located on a plate housing 40 side of the stopper piston 100, and a pressure of the oil, which is supplied to a hydraulic pressure chamber 104 located radially outward of the stopper piston 100, act on the stopper piston 100 to disengage the stopper piston 100 from the engaging ring 102. The stopper piston 100 is fitted into the engaging ring 102 or is disengaged from the engaging ring 102 depending on the balance between the hydraulic force exerted from the hydraulic pressure chamber 103 and the hydraulic pressure chamber 104 and the urging force of the spring 101. As shown in FIG. 4, the hydraulic pressure chamber 103 communicates with the advancing hydraulic chamber 91 through a passage 523, and the hydraulic pressure chamber 104 communicates with the retarding hydraulic chamber 81 through a passage 524.

FIG. 4 shows the most retarded state of the vane rotor 50 relative to the shoe housing 30. In this state, the stopper piston 100 is fitted in the engaging ring 102, so that the vane rotor 50 is coupled to the plate housing 40, and thereby rotation of the vane rotor 50 relative to the plate housing 40 is prevented. Thereby, the vane rotor 50 is rotated together with the plate housing 40, i.e., together with the housing 11. At this time, the vane 54 is in contact with the side surface of the shoe 33. Thus, even when the rotational drive force is transmitted from the crankshaft to the camshaft 15 to cause generation of the positive or negative reverse torque on the camshaft 15, the vane rotor 50 and the housing 11 do not generate rotational vibrations (rotational oscillatory movements), thereby limiting generation of the hammering sound. When the stopper piston 100 is disengaged from the engaging ring 102, the vane rotor 50 is released from the plate housing 40. Thus, the vane rotor 50 can rotate relative to the shoe housing 30 within an angular range from the most retarded position to the most advanced position.

As shown in FIG. 1, an oil pump 1, which serves as a fluid source, supplies the oil taken from an oil tank 2 to a supply passage 3. A change valve 70 is a well-known solenoid spool valve and is placed on an oil pump 1 side of a bearing 6 of the camshaft 15 in such a manner that the supply passage 3 and a discharge passage 4 are placed on one side of the change valve 70, and a retarding passage 80 and an advancing passage 90 are placed on the other side of the change valve 70. The change operation of the change valve 70 is controlled by a drive current, which is under a duty ratio control and is supplied from an electronic control unit (ECU) 5 to a solenoid drive arrangement 71. A spool 72 of the change valve 70 is displaced in accordance with the duty ratio of the drive current. Depending on the position of the spool 72, the change valve 70 performs a change operation to supply the oil to the retarding hydraulic chambers 81-84 or to the advancing hydraulic chambers 91-94 or to drain the oil from the retarding hydraulic chambers 81-84 or from the advancing hydraulic chambers 91-94. The above operation causes the change valve 70 to be changed into one of three states 701-703. When the supply of the electric power to the change valve 70 is stopped, the change valve 70 is placed into the state 701.

Annular passages 151, 152 are formed in an outer peripheral wall of the camshaft 15, which is rotatably supported by the bearing 6. The annular passage 151 is connected to the retarding passage 80, and the annular passage 152 is connected to the advancing passage 90. Four retarding passages 85 and four advancing passages 95 are formed in the interior of the camshaft 15. The retarding passages 85 are connected to the annular passage 151, and the advancing passages 95 are connected to the annular passage 152.

As shown in FIG. 4, four retarding passages 86 are formed in the interior of the boss portion 51 of the vane rotor 50. Each retarding passage 86 connects between the retarding passage 85 and a corresponding retarding passage 87, which is formed in the interior of the boss portion 51 and is communicated with the corresponding retarding hydraulic chamber. Thereby, the retarding passage 80 is communicated with each retarding hydraulic chamber through the annular passage 151 and the retarding passages 85-87. Furthermore, four advancing passages 96 are formed in the interior of the boss portion 51. Each advancing passage 96 connects between the advancing passage 95 and a corresponding advancing passage 97, which is formed in the interior of the boss portion 51 and is communicated with the corresponding advancing hydraulic chamber. In this way, the advancing passage 90 is communicated with each advancing hydraulic chamber through the annular passage 152 and the advancing passages 95-97.

Next, the operation of the valve timing control apparatus 10 will be described.

(1) As shown in FIGS. 1 and 4, at the time of starting the engine, when the oil has not been supplied from the oil pump 1 into the hydraulic pressure chambers 103, 104, the vane rotor 50 is placed at the most retarded position relative to the shoe housing 30 while the crankshaft being rotated. Furthermore, the stopper piston 100 is fitted into the engaging ring 102 by the urging force of the spring 101, so that the vane rotor 50 is coupled to the plate housing 40.

(2) When the oil is pumped from the oil pump 1 upon selecting the state 701 of the change valve 70, the oil is supplied into the retarding hydraulic chambers 81-84 through the retarding passage 80, the annular passage 151 and the retarding passages 85-87 and is also supplied to the hydraulic pressure chamber 104 through the passage 524. When the pressure of the oil, which is supplied into the hydraulic pressure chamber 104, is increased, the oil in the hydraulic pressure chamber 104 urges the stopper piston 100 toward the front plate housing 20 side part of the hole 521 against the urging force of the spring 101. Thereby, the stopper piston 100 is completely disengaged from the engaging ring 102. Thus, the vane rotor 50 is released from the plate housing 40. However, the oil, which is supplied into the retarding hydraulic chambers 81-84, exerts the pressure against the corresponding lateral surface of the respective vanes 52-55, so that the vane rotor 50 is still held in the most retarded position relative to the shoe housing 30, as shown in FIG. 4. Accordingly, generation of the hammering sound between the vane rotor 50 and the shoe housing 30 is limited.

(3) When the change valve 70 is changed from the state 701 to the state 703, the oil is supplied from the oil pump 1 to the advancing hydraulic chambers 91-94 through the advancing passage 90, the annular passage 152 and the advancing passages 95-97 and is also supplied to the hydraulic pressure chamber 103 through the passage 523. Furthermore, at this time, the retarding hydraulic chambers 81-84 and the hydraulic pressure chamber 104 are opened to the oil tank 2. The pressure of the oil supplied to the hydraulic pressure chamber 103 acts on the distal end surface of the stopper piston 100, so that the stopper piston 100 is kept urged into the front plate housing 20 side part of the hole 521 against the urging force of the spring 101. The oil, which is supplied into the advancing hydraulic chambers 91-94, exerts the pressure against the corresponding lateral surface of the respective vanes 52-55, so that the vane rotor 50 is rotated in the advancing direction shown in FIG. 4 relative to the shoe housing 30. Thereby, the valve timing of the intake valves, which are driven by the camshaft 15, is advanced. When the vane rotor 50 is moved from the most retarded position upon the rotation of the vane rotor 50 relative to the shoe housing 30, the stopper piston 100 and the engaging ring 102 are circumferentially displaced from each other. Thus, the stopper piston 100 is no longer engageable into the engaging ring 102.

(4) When the change valve 70 is placed into the state 701 once again, the vane rotor 50 is rotated in the retarding direction shown in FIG. 4 relative to the shoe housing 30. Thereby, the valve timing of the intake valves, which are driven by the camshaft 15, is retarded. When the change valve 70 is placed in the state 702 during the middle of the rotation of the vane rotor 50 relative to shoe housing 30 in the advancing direction or the retarding direction, the flow of the oil into and out of the retarding hydraulic chambers 81-84 and of the advancing hydraulic chambers 91-94 is blocked. Thus, the vane rotor 50 is held in the intermediate position, so that the desired valve timing is obtained.

Next, behavior of the valve timing control apparatus 10 during the rotation of the engine will be described with reference to FIGS. 2 and 3.

The chain 7 is wound around the gear 13 of the housing 11. Thereby, a tension F1 of the chain 7 is radially inwardly applied to the housing 11 at the gear 13. The boss portion 51 of the vane rotor 50 acts as the bearing to rotatably supports the housing 11, and the tapered outer wall surface 56 of the boss portion 51 contacts the corresponding tapered inner wall surface 37 of the shoe housing 30. The tapered outer wall surface 56 and the radially opposed tapered inner wall surface 37 are tilted by the predetermined angle α relative to the axis of the boss portion 51. Therefore, when a force is applied from the tapered inner wall surface 37 to the tapered outer wall surface 56 through the transmission of the tension F1 from the chain 7, a thrust force F2 is exerted to the tapered inner wall surface 37, i.e., to the housing 11 through the interaction between the tapered outer wall surface 56 and the tapered inner wall surface 37. The thrust force F2 is a force that is directed toward the front plate housing 20 side of the housing 11 in the axial direction. In this way, the housing 11 is urged by the vane rotor 50 toward the front plate housing 20 side in the axial direction. Therefore, the plate housing 40 is urged against the end surface 58 of the vane rotor 50, and thereby the axial width d of the clearance 21, which is formed between the vane rotor 50 and the front plate housing 20, is kept constant.

When the plate housing 40 is urged against the end surface 58 of the vane rotor 50, it is possible to reduce the leakage of the oil between the plate housing 40 and the vane rotor 50. Also, when the width d of the clearance 21 is kept constant, the seal member 60 can effectively close the clearance 21. In this way, the leakage of the oil through the clearance 21 can be reduced.

The tension F1 of the chain 7 becomes high when the rotational speed of the engine becomes high. Thus, it is desirable to set the tilt angle α of the tapered outer wall surface 56 and of the radially opposed tapered inner wall surface 37 relative to the axis of the boss portion 51 within a range of 3 to 10 degrees to avoid the excessive amount of the thrust force F2 at the time of high rotational speed of the engine while maintaining the sufficient thrust force F2 to the housing 11.

As described above, according to the first embodiment, the thrust force F2 is exerted to the housing 11 due to the interaction between the tapered outer wall surfaces 56 and the corresponding tapered inner wall surface 37. In this way, the housing 11 is urged in the predetermined direction, and the constant axial width d of the clearance 21, which is formed between the vane rotor S0 and the front plate housing 20, is maintained. Thereby, the clearance 21 can be effectively closed by the seal member 60 to reduce the leakage of oil through the clearance 21. Therefore, with use of the simple structure, the leakage of the oil can be reduced, and the phase of the camshaft 15 can be controlled with relatively high accuracy.

According to the first embodiment, the gear 13 extends annularly along the outer peripheral wall of the housing 11 at the axial location within the width W between the end surface 57 and the end surface 58 of vane rotor 50. That is, the gear 13 is provided along the outer peripheral wall of the housing 11 at the location radially outward of the boss portion 51. Thus, the tension F1 of the chain 7 is directly applied to the tapered outer wall surface 56 through the gear 13. In this way, the thrust force F2 is more effectively applied to the housing 11 to more stably maintain the constant axial width d of the clearance. Therefore, the leakage of the oil can be reduced with use of the simple structure, and the phase of the camshaft 15 can be highly accurately controlled.

In the first embodiment, the stopper piston 100 is fitted into the engaging ring 102, which is provided in the plate housing 40. That is, the stopper piston 100 is fitted into the engaging ring 102, and this engaging ring 102 is provided in the plate housing 40 that is located on the opposite axial side, which is opposite from the axial side toward which the housing 11 is urged by the vane rotor 50 due to the interaction between the tapered outer wall surface 56 and the tapered inner wall surface 37. When the vane rotor 50 urges the housing 11, the plate housing 40 is urged against the end surface 58 of the vane rotor 50. Thus, the stopper piston 100 can be fitted into the engaging ring 102 without being influenced by the clearance 41, which is formed between the vane rotor 50 and the plate housing 40. Furthermore, at the time of providing the seal member 60 in the clearance 21, which is formed between the vane rotor 50 and the front plate housing 20, it is not required to form a through hole in the seal member 60 to receive the stopper piston 100. Also, the seal member 60 can be easily installed. Therefore, it is possible to reduce the costs required for processing and installation of the seal member 60.

Second Embodiment

FIG. 8 shows a valve timing control apparatus according to a second embodiment of the present invention. In the following description, components, which are similar to those of the first embodiment, will be indicated by the same reference numerals and will not be described further. The second embodiment is a modification of the first embodiment, so that the same components, which are basically the same as those of the first embodiment, are provided in the second embodiment while the shape and location of some of the components are different from those of the first embodiment.

In the first embodiment, the tapered outer wall surface 56 of the boss portion 51 is tapered in the axial direction away from the camshaft 15. In contrast, according to the second embodiment, the tapered outer wall surface 56 of the boss portion 51 is tapered in an axial direction toward the camshaft 15. In other words, the tapered outer wall surface 56 of the boss portion 51 and the opposed tapered inner wall surface 37 of the shoe housing 30 are tilted by the predetermined angle α in a direction that is opposite from that of the first embodiment. Here, the imaginary line L1, which extends along the tapered outer wall surface 56 and intersects with an imaginary plane that extends along the axis of the boss portion 51 and is parallel to the axis of the boss portion 51, is tilted relative to the axis of the boss portion 51 by the predetermined angle α. Also, the imaginary line L2, which extends along the tapered inner wall surface 37 of the corresponding shoe 32-35 and intersects with the imaginary plane that extends along the axis of the boss portion 51 and is parallel to the axis of the boss portion 51, is tilted relative to the axis of the boss portion 51 by the predetermined angle α. These imaginary lies L1, L2 intersect with each other on the camshaft 15 side of the boss portion 51.

The seal member 60 is provided between the vane rotor 50 and the plate housing 40. The seal member 60 is clamped between the plate housing 40 and the shoe housing 30. The protrusion of the seal member 60 slidably contacts the end surface 58 of the vane rotor 50, which is located on the plate housing 40 side of the vane rotor 50. The inner diameter of the through hole 61 of the seal member 60 is set to be slightly larger than the outer diameter of the vane rotor 50 side end portion of the camshaft 15. With this structure, the seal member 60 closes the clearance 41, which is formed between the vane rotor 50 and the plate housing 40. The hydraulic pressure chamber 103 and the engaging ring 102 are provided in the vane rotor 50 side inner wall of the front plate housing 20.

Similar to the first embodiment, the gear 13 extends annularly along the outer peripheral wall of the housing 11 within the width W between the end surface 57 and the end surface 58 of vane rotor 50. That is, the gear 13 is provided along the outer peripheral wall of the housing 11 at the location radially outward of the boss portion 51.

In the second embodiment, at the time of rotating the engine, when the radial force is applied from the tapered inner wall surface 37 to the tapered outer wall surface 56 due to the conduction of the tension F1 from the chain 7 to the housing 11, the thrust force F2 is axially applied to the housing 11 toward the plate housing 40 side due to the interaction between the tapered outer wall surface 56 and the tapered inner wall surface 37. In this way, the housing 11 is urged by the vane rotor 50 toward the plate housing 40 side in the axial direction. Therefore, the front plate housing 20 is urged against the end surface 57 of the vane rotor 50, and thereby the axial width d2 of the clearance 41, which is formed between the vane rotor 50 and the plate housing 40, is kept constant.

The leakage of the oil between the front plate housing 20 and the vane rotor 50 can be reduced by urging the front plate housing 20 against the end surface 57 of the vane rotor 50. Also, when the width d2 of the clearance 41 is kept constant, the seal member 60 can effectively close the clearance 41. In this way, the leakage of the oil through the clearance 41 can be reduced. Therefore, the leakage of the oil can be reduced with use of the simple structure, and the phase of the camshaft 15 can be highly accurately controlled.

Third Embodiment

FIG. 9 shows a valve timing control apparatus according to a third embodiment of the present invention. In the following description, components, which are similar to those of the first embodiment, will be indicated by the same reference numerals and will not be described further. The third embodiment is a modification of the first embodiment, and the location of the gear 13 is different from that of the first embodiment.

In the third embodiment, the gear 13, which is engaged with the chain 7, extends annularly along the outer peripheral wall of the plate housing 40. That is, the gear 13 is provided along the outer peripheral wall of the housing 11 at the location outside of the range of the width W between the end surface 57 and the end surface 58 of the vane rotor 50. In other words, the gear 13 is provided to the outer peripheral wall of the housing member 11 such that the axial extent of the gear 13 does not overlap with the axial extent of the vane rotor 50. Even in the third embodiment, similar to the first embodiment, the boss portion 51 of the vane rotor 50 acts as the bearing that rotatably supports the housing 11. Thus, at the time of rotating the engine, when the radial force is applied from the tapered inner wall surface 37 to the tapered outer wall surface 56 due to the conduction of the tension F1 from the chain 7 to the housing 11, the thrust force F2 is applied to the housing 11 due to the interaction between the tapered outer wall surface 56 and the tapered inner wall surface 37. In this way, similar to the first embodiment, the housing 11 is urged by the vane rotor 50 toward the front plate housing 20 side in the axial direction. Thereby, the axial width d of the clearance 21, which is formed between the vane rotor 50 and the front plate housing 20, is kept constant, and the clearance 21 can be effectively closed by the seal member 60 to reduce the leakage of the oil through the clearance 21. Therefore, the leakage of the oil can be reduced with use of the simple structure, and the phase of the camshaft 15 can be highly accurately controlled.

Now, modifications of the above embodiments will be described.

The gear of the housing in the second embodiment may be provided in the outer peripheral wall of the plate housing instead of the shoe housing. That is, in this modification, the gear can be provided in any appropriate location as long as the gear is provided to the outer peripheral wall of the housing. When the gear is provided in the outer peripheral wall of the housing, the boss portion of the vane rotor can act as the bearing to rotatably support the housing, and thereby the force is applied to the tapered outer wall surface in the radial direction.

In the above embodiments, the chain is used as the drive force transmitting member, which transmits the drive force from the crankshaft to the housing. However, the drive force transmitting member is not limited to the chain. Specifically, in this modification, a belt or a gear may be used as the drive force transmitting member in place of the chain. Even in the case where the drive force transmitting member is the belt or the gear, the force can be applied to the housing in the radially inward direction in a manner similar to that of the chain. In this way, the thrust force is applied to the housing, and thereby the housing is urged in the desired direction. As a result, the axial width of the clearance between the vane rotor and the housing is kept constant, and this clearance can be effectively closed by the seal member.

Furthermore, in the above embodiments, the valve timing control apparatus is applied to the intake valves of the engine. Alternatively or additionally, the valve timing control apparatus may be applied to exhaust valves of the engine. Also, the present invention may be applied to a valve timing control apparatus, which does not have the stopper piston.

Additional advantages and modifications will readily occur to those skilled in the art. The invention in its broader terms is therefore not limited to the specific details, representative apparatus, and illustrative examples shown and described.

VALVE TIMING CONTROL APPARATUS

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CPC

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Priority Claims (1)