Patent Publication Number: US-6907853-B2

Title: Variable valve timing control device

Description:
This application is based on and claims priority under 35 U.S.C. § 119 with respect to Japanese Application No. 2001-230790 filed on Jul. 31, 2001, the entire content of which is incorporated herein by reference. 
   FIELD OF THE INVENTION 
   This invention generally relates to a variable valve timing control device. More particularly, the present invention pertains to a variable valve control device for controlling the opening and closing timing of a valve of an internal combustion. 
   BACKGROUND OF THE INVENTION 
   A known variable valve timing control device is disclosed in Japanese Patent Laid-Open Publication No. 2001-3716. This known variable valve timing control device includes a first rotational body rotatably provided on a camshaft actuated being synchronized with the engine revolution and having a case provided with plural shoes on an internal peripheral surface, a second rotational body fixedly connected to the camshaft for slidably contacting an internal surface of the first rotational body and having a lock groove in axial direction on the sliding surface side, a lock member for locking the first rotational body and the second rotational body for unitary rotation by engaging with the lock groove and for releasing the lock by retracting from the lock groove, a biasing means for biasing the lock member towards the lock groove, and a hydraulic pressure supply means for applying the hydraulic pressure in the direction against the biasing force of the biasing means to the lock member. This variable valve timing control device further includes an engagement groove provided on at least one of the shoes in axial direction for retracting and supporting the lock member. At least one axial end of the groove is open. The side of the engagement groove facing the sliding surface of the second rotational body is open. The variable valve timing control device still further includes a plate shape lock member fitted in the engagement groove for sliding in the direction of the rotational center of the first and second rotational body, and a lock groove provided on a portion of a boss portion external peripheral surface of the second rotational body to be engaged with a tip portion of the plate shape lock member. 
   With respect to the known variable valve timing control device of the Japanese Patent Laid-Open Publication No. 2001-3716, the engagement groove is penetrated into at least one of the shoes of the case along the axial direction. 
   In the known variable valve timing control device of the Japanese Patent Laid-Open Publication No. 2001-3716, the first rotational body and the second rotational body are synchronized with each other to be rotated by the engagement of the lock member of the lock mechanism with a lock hole. In general, a cam provided on the camshaft of the internal combustion pushes down a valve body against the biasing force of the biasing means for biasing either an intake valve or an exhaust valve of the internal combustion engine (i.e., hereinafter referred as valve body) in closing direction. That is, the resistance applied to the cam when opening the valve body is large, and the resistance applied to the cam when closing the cam is small. Thus, the rotational speed of the camshaft is fluctuated relative to the rotational speed of the first rotational body (e.g., a timing pulley transmitted with the rotational force from a crankshaft via a belt) which rotates being synchronized with the engine revolution. More practically, the rotational speed of the camshaft is declined relative to the rotational speed of the first rotational body when the valve body is opened (i.e., when the cam is at a predetermined first phase). The rotational speed of the camshaft is increased relative to the rotational speed of the pulley when the valve body is closed (i.e., when the cam is at a predetermined second phase). By the change of the rotational speed in accordance with the rotational phase of the camshaft, the force for advancing or delaying the second rotational body (e.g., a rotor having a vane) relative to the rotation of the first rotational body is applied. The force applied to the second rotational body is also applied to the first rotational body via a lock portion for engaging the first rotational body and the second rotational body to be unitary rotated. In the known variable valve timing control device of the Japanese Patent Laid-Open Publication No. 2001-3716, the engagement groove engaged with the lock member is formed on one of the shoes formed on the case. The stress is repeatedly applied to the shoe portion including the engagement groove by the force for delaying and advancing the second rotational body relative to the first rotational body. Thus, it is required to ensure the strength of the portion around the engagement groove provided on the first rotational body. Notwithstanding, when reducing the size of the variable valve timing control device while managing to ensure the operation angle, it is difficult to ensure the strength of the shoe portion because the size of the shoe portion, particularly, the circumferential length is limited. In particular, provided that the engagement groove is provided on at least one of the shoes of the case along the axial direction, the shoe portion provided with the engagement groove has a structure like a cantilever, which may drastically decline the strength of the shoe portion. 
   A need thus exists for a variable valve timing control device which prevents the concentration of the load to a particular shoe portion for ensuring the strength thereof. 
   SUMMARY OF THE INVENTION 
   A variable valve timing control device includes a housing unitary rotating either one of a crankshaft or a camshaft of an internal combustion engine, a rotor unitary rotating with the other of the crankshaft or the camshaft of the internal combustion engine, at least one shoe portion for dividing a fluid pressure chamber provided between the housing and the rotor in a circumferential direction of the housing, a plate member for closing at least one of axial end surfaces of the housing, a plural fixing members for unitary fixing the housing and the plate member, a vane for dividing the fluid pressure chamber into an advance angle chamber and a retarded angle chamber, a lock plate provided on one of the rotor and the housing and movable in a radial direction of the rotor, an engagement groove provided on the other of the rotor and the housing for engaging with the lock plate, and a relative rotation control mechanism provided on said one of the housing and the rotor and including a retraction groove for moving the lock plate in radial direction for restricting a relative rotation between the housing and the rotor by an engagement of the lock plate with the engagement groove in accordance with a supply of fluid. One of the fixing members is provided between one of the fluid pressure chambers divided by the shoe portion and the relative rotation control mechanism and another fixing member is provided between the relative rotation control mechanism and another fluid pressure chamber. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     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 drawing figures in which like reference numerals designate like elements. 
       FIG. 1  is a cross-sectional view of a variable valve timing control device of a first embodiment of the present invention. 
       FIG. 2  is a cross-sectional view of the variable valve timing control device of  FIG. 1  take on line A—A. 
       FIG. 3  is a view showing a housing of the variable valve timing control device of the first embodiment of the present invention. 
       FIG. 4  is a view showing a second embodiment of a variable valve timing control device of the present invention. 
       FIG. 5  is a view showing a third embodiment of a variable valve timing control device of the present invention. 
       FIG. 6  is a view showing a variation of the third embodiment of the variable valve timing control device of the present invention. 
   

   DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
   A first embodiment of a variable valve timing control device of the present invention will be explained referring to  FIGS. 1-2 . In order to reduce the complication of the drawing, the hatched line of  FIG. 2  is omitted. 
   The variable valve timing control device of the present invention shown in  FIGS. 1-2  includes a rotor  21  unitary assemble to a tip portion (i.e., shown in left end of  FIG. 1 ) of a camshaft (i.e., driven shaft)  10  with bolts (not shown), a housing  30  outfitted to the rotor  21  to be rotatable relative to the rotor  21  for being transmitted with the rotational force from a crankshaft (i.e., rotation shaft; not shown) of an engine via a transmission member  90  (i.e., timing chain in this embodiment), a torsion spring S provided between the housing  30  and the rotor  21 , and a hydraulic pressure control valve  100  for controlling the supply and discharge of the operation fluid (i.e., fluid) to/from a relative rotation control mechanism B (shown in  FIG. 2 ) which controls the relative rotation between the housing  30  and the rotor  21  and the supply and discharge of the operation fluid to/from an advance angle chamber R 1  and a retarded angle chamber R 2 . The hydraulic pressure control valve  100  also controls the supply and discharge of the operation fluid to/from the relative rotation control mechanism B. 
   The camshaft  10  includes a cam (not shown) for opening and closing one of an intake valve or an exhaust valve (not shown) and is rotatably supported by a cylinder head (not shown) of the internal combustion engine. An advance angle passage  11  and a retarded angle passage  12  extended in axial direction of the camshaft  10  is provided in the camshaft  10 . The advance angle passage  11  is connected to a connection port  102  of the hydraulic pressure control valve  100  via a bore  13  in radial direction and an annular passage  14 . The retarded angle path  12  is connected to a connection port  101  of the hydraulic pressure control valve  100  via a bore  15  in radial direction and an annular passage  16 . The bores  13 ,  15  in radial direction and the annular passages  14 ,  16  are formed on the camshaft  10 . 
   The rotor  21  unitary screwed to a tip portion of the camshaft  10  with bolts (not shown) includes a central inner bore  21   a  of the rotor  21  whose front end is closed with a head portion of the bolt. The central inner bore  21   a  is in communication with the advance angle path  11  provided on the camshaft  10 . 
   The rotor  21  includes four vanes  23  (shown in  FIG. 2 ) and vane grooves  21   b  (shown in  FIG. 2 ) being assembled with springs  24  respectively for biasing the vanes  23  in radial direction. Each vane  23  is assembled in the corresponding vane groove  21   b  to be extended in the outer radial direction for dividing a fluid pressure chamber to form an advance angle chamber R 1  and a retarded angle chamber R 2 . 
   The housing  30  includes a housing body  31 , a front plate  32 , a rear thin plate  33 , and five bolts  34  for unitary connecting the housing body  31 , the front plate  32 , and the rear thin plate. 
   A sprocket  31   a  is unitary formed on a rear external periphery of the housing body  31 . The sprocket  31   a  is connected to the crankshaft of the engine via the timing chain  90 . The housing  30  is rotated in the clockwise direction of  FIG. 2  by the transmission of the driving force from the crankshaft. 
   The housing body  31  includes four shoe portions  31   g ,  31   h ,  31   j ,  31   k  for forming four fluid pressure chambers (i.e., a first fluid pressure camber  31   c , a second fluid pressure chamber  31   d , a third fluid pressure chamber  31   e , and a fourth fluid pressure chamber  31   f ). The fluid pressure chambers  31   c ,  31   d ,  31   e ,  31   f  are projecting in radial inner direction. More practically, the first fluid pressure chamber  31   c  is divided by the shoe portion  31   g  and the shoe portion  31   k . The second fluid pressure chamber  31   d  is divided by the shoe portion  31   g  and the shoe portion  31   h . The third pressure chamber  31   e  is formed by the shoe portion  31   h  and the shoe portion  31   j . The fourth fluid pressure chamber  31   f  is divided by the shoe portion  31   j  and the shoe portion  31   k . By positioning the vanes  23  in the corresponding four fluid pressure chambers  31   c ,  31   d ,  31   e ,  31   f , respectively, the advance angle chamber R 1  and the retarded angle chamber R 2  are divided in each fluid pressure chamber. 
   The relative rotation control mechanism B is formed on the shoe portion  31   j . The relative rotation control mechanism B allows the relative rotation between the housing  30  and the rotor  21  by the unlock operation by the supply of the operation fluid from the advance angle passage  11  and restricts the relative rotation between the housing  30  and the rotor  21  towards the advanced angle side at a most retarded angle phase position (i.e., the condition shown in  FIG. 2 ) by the lock operation by the discharge of the operation fluid to the advanced angle passage  11 . The relative rotation control mechanism B includes a lock plate  61 , a lock spring  62 , a lock groove  21   h , a retraction bore  31   l , and an accommodation portion  31   m.    
   The slit shaped retraction bore  31   l  and the rectangular accommodation portion  31   m  whose width is wider than the retraction bore  31   l  are provided on the shoe portion  31   j  of the housing body  31 . The lock plate  61  is assembled on the retraction bore  31   l  being slidable in the radial direction. The lock spring  62  for biasing the lock plate  61  to be projected from the retraction bore  31   l  is placed in the accommodation portion  31   m.    
   A tip portion (i.e., internal diameter side end portion) of the lock plate  61  is slidably advancing to and retracting from the lock groove  21   h  provided on the rotor  21 . The lock plate  61  is retracted to be accommodated in the retraction bore  31   l  by moving in the radial direction against the biasing force of the lock spring  62  by the supply of the operation fluid to the lock groove  21   h . As shown in  FIG. 2 , the lock groove  21   h  is provided to face with the end portion (i.e., internal radial side end portion) of the lock groove  21   h  to each retraction bore  31   l  when the rotor  21  is at the most retarded angle phase position relative to the housing  30 . 
   Because the retraction bore  31   l  and the accommodation portion  31   m  have the openings on the both sides in the central axial direction of the hosing body  31 , a portion  31   j   1  of the shoe portion  31   j  closer to the third fluid pressure chamber  31   e  and a portion  31   j   2  of the shoe portion  31   j  closer to the fourth fluid pressure chamber  31   f  are connected via a peripheral portion  31   n  of the housing body  31 . 
   Five bolts  34  for fixing the housing  30  are placed on each shoe portion  31   g ,  31   h ,  31   j ,  31   k . Three bolts  34  are respectively positioned on the shoe portions  31   g ,  31   h ,  31   k  which are positioned between the fluid pressure chambers (e.g., the shoe portion  31   g  is positioned between the first fluid pressure chamber  31   c  and the second fluid pressure chamber  31   d ). Two bolts  34  are positioned on the shoe portion  31   j  on which the retraction bore  311  and the accommodation portion  31   m  are constructed. In this case, one bolt  34  of the two is positioned on the portion  31   j   1  and the other bolt  34  is portioned on the portion  31   j   2  for positioning the retraction bore  31   l  and the accommodation portion  31   m  between the bolts  34 . According to the first embodiment, five bolts  34  are equally positioned in peripheral direction each having 72 degree interval with the neighboring bolt relative to the center of the hosing body  31 . It is preferable that the two bolts  34  positioned on the portion  31   j   1  and the portion  31   j   2  are arranged to have the same angle B (shown in  FIG. 3 ) relative to projections  31   p ,  31   q  respectively. Thus, a variable valve timing control device which operates the relative rotation control mechanism B when the relative phase between the housing  30  and the rotor  21  is at a most advance angle phase position can be constructed using the housing the same with the case that the relative rotation control mechanism B is operated when the relative phase between the lousing  30  and the rotor  21  is at the most retarded position. In this case, the same housing  30  is used by placing in reverse. 
   The torsion spring S provided between the housing  30  and the rotor  21  biases the rotation of the rotor  21  towards the advance angle side relative to the housing  30 . By using the torsion spring S, the operational response when changing the relative rotational phase of the rotor  21  relative to the housing  30  from the retarded angle side to the advanced angle side is improved. 
   The hydraulic pressure control valve  100  corresponds to a variable type electromagnetic spool valve. The hydraulic pressure control valve  100  includes a solenoid, a spool, and a spring, for moving the spool against the biasing force of the spring by the energization to the solenoid. By performing duty cycle control regarding the energization amount to the solenoid, the stroke amount of tile spool is changed, thus to control the supply and discharge of the operation fluid to/from the advance angle passage  11 , the retarded angle passage  12 , and the first control mechanism B 1 . 
   The engine includes a hydraulic pressure circuit C having an oil pump  110 , an oil pan  120 , a supply passage, and a discharge passage. The operation fluid supplied to the advance angle chamber R 1 , the retarded angle chamber R 2  and the relative rotation control mechanism B is supplied by the oil pump  110  actuated by the engine via the supply passage and the hydraulic pressure control valve  100 . The operation fluid discharged from the advance angle camber R 1 , the retarded angle chamber R 2  and the relative rotation control mechanism B reaches the oil pan  120  via the discharge passage and the hydraulic pressure control valve  100 . 
   The operation of the variable valve timing control device will be explained as follows. 
   When the relative rotation control mechanism B of the variable valve timing control device  1  is operated, the lock plate  61  is engaged with the lock groove  21   h . The fluctuation torque is applied to the camshaft  10  of the internal combustion engine under this condition. The fluctuation torque functions as the force for alternately rotating the camshaft  10  in the advanced angle direction and in the retarded angle direction. The rotor  21  is also alternately rotated in the advance angle direction and the retarded angle direction because the rotor  21  is fixed to the camshaft  10  to be unitary rotated. 
   When the internal combustion engine is stopped, the operation fluid is returned to the oil pan  12  from each advance angle chamber R 1 , each retarded angle chamber R 2 , and the lock groove  21  of the relative rotation control mechanism B through the clearance of each member. 
   The operation fluid cannot be sufficiently discharged even if the oil pump  110  is actuated by the internal combustion engine at the initial phase immediately after the engine start, particularly, during warming up the engine. The insufficient discharge of the operation fluid when the oil pump  110  is actuated by the internal combustion engine during the engine warming up is caused by an unstable operation of the internal combustion engine immediately after the start of the engine. The insufficient discharge of the operation fluid at the initial stage of the engine start also derives from the increased discharge pressure and the small operation fluid volume because the operation fluid discharged from the oil pump  110 , for example, the engine oil used for lubricating the internal combustion engine includes high viscosity under the low temperature. Thus, the operation fluid cannot be sufficiently supplied from the hydraulic pressure circuit C to each advance angle chamber R 1  and each retarded angle chamber R 2  respectively even when the hydraulic pressure control valve  100  is controlled. In this case, the relative rotational position of the rotor  21  relative to the housing  30  is not maintained by applying the fluid pressure in the advance angle chamber R 1  to the vane  23 , instead, the relative rotational position of the rotor  21  relative to the hosing  30  is maintained at the most retarded angle phase position by the relative rotation control mechanism B. The aforementioned fluctuation torque is applied to the camshaft  10  of the internal combustion engine and the rotor  21 . Because the operation fluid is not supplied to the advance angle chamber R 1  and the retarded angle chamber R 2 , the rotation of the rotor  21  in the advance angle direction and in the retarded angle direction is restricted by the relative rotation control mechanism B, more particularly, restricted by the lock plate  61  engaged with the lock groove  21   h . By the rotational force of the rotor  21 , the lock groove  21   h  provided on the rotor  21  forces to rotate the lock plate  61  engaged with the lock groove  21   h . The lock plate  61  transmits the rotational force from the rotor  21  to the housing  30  (i.e., shoe portion  31   j ) via the retraction bore  31   l . That is, the force for rotating the rotor  21  by the fluctuation torque is applied to the shoe portion  31   j  provided with the retraction bore  31   l  of the housing  30  via the lock plate  61 . Because the bolts  34  are provided on the portion  31   j   1  and the portion  31   j   2  of the shoe portion  31   j  respectively according to this embodiment, the portion  31   j   1  and the portion  31   j   2  is included in a U-shaped section (i.e., when viewed from the cross-section) which is formed by being sandwiched by the front plate  32  and the rear plate  33 . The movement of the shoe portion  31   j  is restricted in the peripheral direction by the housing, the front plate  32 , and the rear plate  33  fixed with the bolt  34  not to change the shape even at the relative rotation of the rotor  21  relative to the hosing  30 . Thus, the rigidity of the portion  31   j   1  and the portion  31   j   2  is improved for preventing the displacement of the portion  31   j   1  and the portion  31   j   2  by the fluctuation torque. In addition, because the retraction bore  31   l  and the accommodation portion  31   m  are provided on the shoe portion  31   j  and respective bolts  34  are respectively positioned on the portions  31   j   1  and the  31   j   2  which are approximately separate portions, the rigidity of the portions  31   j   1  and  31   j   2  can be improved. Accordingly, because the concentration of the stress to the peripheral portion  31   n  of the housing body  31  is mitigated, the generation of the defect such as the generation of the crack on the housing  30  due to the fluctuation torque can be prevented. 
     FIG. 4  shows a second embodiment of a variable valve timing control device. The variable valve timing control device of the second embodiment is the same with the variable valve timing control device according to the first embodiment except the positioning of the bolts  34  to the housing  30 . Thus, The explanation will be omitted by applying the same numerals with the first embodiment to the same construction with the first embodiment. 
   As shown in  FIG. 4 , the bolts  34  provided on the portions  31   j   1  and  31   j   2  of the shoe portion  31   j  according to the second embodiment have an angle D relative to the retraction bore  31   l  respectively. Thus, the circumferential length of the portion  31   j   1  and the circumferential length of the portion  31   j   2  of the shoe portion  31   j  can be formed in approximately the same length. Accordingly, the rigidity of the portions  31   j   1  and  31   j   2  of the shoe portion  31   j  can be approximately the same to ensure the strength of the portions  31   j   1  and  31   j   2 . In addition, because the dimension of the shoe portion  31   j  fastened with one bolt  34  is approximately the same with the dimension of the shoe portions  31   g ,  31   h ,  31   k , the sealing effect between the fluid pressure chambers  31   c ,  31   d ,  31   e ,  31   f  can be further improved. The shoe portions  31   g ,  31   h ,  31   k ,  31   j  including the portions  31   j   1 ,  31   j   2  are functioning as the bearing of the rotor  21 . The circumferential length of the portion  31   j   1  and the portion  31   j   2 , and the length of the shoe portions  31   g ,  31   h ,  31   k , can be approximately the same. Thus, because the rotor  21  evenly contacts the shoe portion functioning as the bearing, the life duration of the bearing is improved and the partial wear-out of the rotor  21  can be prevented. Further, by equalizing the bearing load, the rotor  21  is easily slidable and the sliding resistance can be reduced. 
     FIGS. 5-6  show a third embodiment of a variable valve timing control device. The variable valve timing control device of the third embodiment is the same with the variable valve timing control device of the second embodiment except the positioning of the projections  31   p ,  31   q . The same numerals are provided on the same construction with the second embodiment and the explanation is omitted. 
   As shown in  FIG. 5 , the vane  23  contacts the projection  31   p  provided on one peripheral end surface of the shoe portion  31   k  side in the first fluid pressure chamber  31   c  when the relative phase position of the rotor  21  relative to the housing  30  is at tile most retarded angle position (i.e., the condition that the relative rotation between the rotor  21  and the housing  30  is restricted by the relative rotation control mechanism B). As shown with chain double-dashed lines in  FIG. 5 , the vane  23  contacts the projection  31   q  provided on one peripheral end surface of the shoe portion  31   h  side in the second fluid pressure chamber  31   d  when the relative phase position of the rotor  21  relative to the housing  30  is at the most advance angle position. 
   As shown in  FIG. 6 , the vane  23  contacts the projection  31   p  provided on one peripheral end surface of the shoe portion  31   g  side in the second fluid pressure chamber  31   d  when the relative phase position of the rotor  21  relative to the housing  30  is at the most retarded angle position (i.e., the condition that the relative rotation between the rotor  21  and the housing  30  is restricted by the relative rotation control mechanism B). As shown with chain double-dashed lines in  FIG. 6 , the vane  23  contacts the projection  31   q  provided on the other peripheral end surface of the shoe portion  31   g  side in the first fluid pressure chamber  31   c  when the relative phase position of the rotor  21  relative to the housing  30  is at the most advance angle position. 
   According to the foregoing embodiments of the variable valve timing control device, the projections  31   p ,  31   q  for restricting the relative rotation of the rotor  21  and the housing  30  by the contact of the vane  23  to the housing  30  when the relative rotation of the rotor  21  and the housing  30  is restricted by the relative rotation control mechanism B are provided in the fluid pressure chambers divided with the shoe portions  31   g ,  31   h ,  31   k  which are not provided with the retraction bore  31   l . Thus, the concentration of the load generated by the fluctuation torque, which is applied from the vane  23  to the housing  30 , to a single shoe portion can be prevented. Thus, the rigidity of the housing  30  can be improved. 
   According to the embodiments of the present invention, the rigidity of the shoe portion provided with the engagement groove or the accommodation groove of the relative rotation control mechanism can be improved by providing the fixing members between one of the fluid pressure chambers divided by the shoe portion and the relative rotation control mechanism and another fixing member is provided between the relative rotation control mechanism and another fluid pressure chamber respectively. Thus, because the rigidity of the position on which the stress is concentrated is improved, the durability of the housing can be improved. 
   According to the embodiments of the present invention, by positioning tile fixing member having an equal angle relative to the rotational center of the housing the fastening force of the plate member fastened to the housing can be equalized. Thus, the sealing effect of the fluid pressure chamber in axial direction can be improved. 
   According to the embodiments of the present invention, by positioning the fixing members between one of the fluid pressure chambers divided by the shoe portion and the relative rotation control mechanism and another fixing member is provided between the relative rotation control mechanism and another fluid pressure chamber respectively having an equal angle relative to the relative rotation control mechanism, the length of the circumferential length of the portions of the shoe portion provided with the engagement groove or the accommodation groove can be approximately the same each other. Thus, because the dimension to be fastened with the fixing member is approximately the same with other shoe portions which are not provided with the relative rotation control mechanism and the sealing effect in axial direction between the fluid pressure chambers can be improved. 
   The principles, preferred embodiments and modes 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 change 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.