Patent Publication Number: US-6334414-B1

Title: Valve timing adjusting apparatus

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application relates to and incorporates herein by reference Japanese Patent Applications No. 11-223974 and No. 11-223987, both being filed on Aug. 6, 1999. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a valve timing adjusting apparatus for changing the operation timing (valve timing) of a suction valve and/or an exhaust valve of an internal combustion engine. 
     2. Related Art 
     In a vane type valve timing adjusting apparatus, a camshaft is driven by means of a timing pulley, a chain sprocket, or the like that is rotated synchronously with a crankshaft of an engine. Thus, the valve timing of a suction valve and/or an exhaust valve is hydraulically controlled based on the phase difference of relative rotation between the timing pulley or chain sprocket and a camshaft. 
     In the case of such a vane type valve timing apparatus that uses working fluid, a load torque that fluctuates between positive side and negative side that is caused by driving the suction valve and/or the exhaust valve is exerted on the camshaft. For example, in the state that the working fluid is not supplied sufficiently as in the engine cranking at the starting of an engine, a vane member swings toward a housing member that accommodates the vane member, and generates hammering sound due to collision between the housing member and the vane member. 
     It is therefore proposed that a stopper piston fits a housing member when a camshaft is positioned intermediate between the most retarded angle and the most advanced angle with respect to the crankshaft to control the relative rotation of the camshaft with respect to the crankshaft. The engine is started with the camshaft being at the intermediate position between the most retarded angle and the most advanced angle. That is, the engine is thereby started in the state that the camshaft is located at the preferable position with respect to the crankshaft. 
     However, a force exerted on the stopper piston to be fitted with an fitting bore is only the urging force of a spring, it is difficult to fit the stopper piston in the fitting bore within a short time. Furthermore, in the case that a hydraulic pressure for maintaining the unrestricted state in which a contact portion is disengaged from the fitting bore is low, the stopper piston jumps out to the fitting bore side due to the urging force of the spring during the phase control for rotating the vane member relatively to the housing member. As a result the stopper piston can be caught in the fitting bore. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a valve timing adjusting apparatus for enabling an engine starting promptly while minimizing hammering sound. 
     It is another object of the present invention to provide a valve timing adjusting apparatus for preventing a constraint member from being constrained during a phase control. 
     According to a valve timing adjusting apparatus of the present invention, a constraint member is provided for constraining the relative rotation of a driven side rotor with respect to a driving side rotor when the driven side rotor is positioned at the intermediate position between the most retarded angle and the most advanced angle with respect to the driving side rotor is provided. By constraining the relative rotation of the driven side rotor with respect to the driving side rotor at the intermediate position, failure in starting an engine is reduced thus minimizing noxious exhaust gas. 
     In addition to release of constraint state associated with a contact portion and a contact receiving portion by means of the first working fluid pressure, the contact portion is displaced in the direction to be brought into contact with the contact receiving portion by means of the second working fluid pressure. For example, the first working fluid pressure that acts on the contact portion is reduced and the second working fluid pressure is increased when the engine is to be stopped. As a result, the contact portion is surely brought into contact with the contact receiving portion at the intermediate position. Thereby, the engine is surely started in a short time. 
     Furthermore, by reducing the first working fluid pressure that acts on the contact portion and by increasing the second working fluid pressure when the engine is to be started, the contact portion is held in contact with the contacted portion at the intermediate position. Because the intermediate phase can be held during cranking when the engine is to be started, the engine can be started surely in a short time. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description made with reference to the accompanying drawings. In the drawings: 
     FIG. 1 is a cross sectional view showing an entirety of a valve timing adjusting apparatus according to a first embodiment of the present invention; 
     FIG. 2 is another cross sectional view showing the entirety of the valve timing adjusting apparatus according to the first embodiment; 
     FIGS. 3A to  3 C are partial cross sectional views taken along the line III—III of FIG.  2  and showing the position of a stopper piston in the first embodiment; 
     FIG. 4 is a cross sectional view showing the position of a vane rotor located at the most advanced position in the first embodiment; 
     FIG. 5 is a cross sectional view taken along the line I-O-V of FIG. 2; 
     FIGS. 6A and 6B are cross sectional views showing position of a stopper piston and shape of a fitting member, respectively, in a second embodiment of the present invention; 
     FIGS. 7A to  7 C are partial cross sectional views taken along the line VII—VII of FIG.  8  and showing the position of a stopper piston in a third embodiment of the present invention; 
     FIG. 8 is a cross sectional view showing an entirety of a valve timing adjusting apparatus according to the third embodiment; 
     FIG. 9 is a cross sectional view showing the state that a vane rotor is positioned at the most advanced position in the third embodiment; 
     FIG. 10 is a cross sectional view taken along X-O-X of FIG. 8; 
     FIG. 11 is a cross sectional view taken along the line X-O-XI of FIG. 8; 
     FIGS. 12A and 12B are cross sectional views showing position of a stopper piston in a fourth embodiment of the present invention; and 
     FIG. 13 is a cross sectional view showing shape of a fitting member in the fourth embodiment. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The present invention will be described in detail with reference to various embodiments, in which the same or like parts are designated with the same or like reference numerals. 
     (First Embodiment) 
     Referring first to FIG. 1, a valve timing adjusting apparatus  1  is of a hydraulic pressure control type for controlling the valve timing of a suction valve of an internal combustion engine (not shown). 
     A chain sprocket  10  that serves as one side wall of a driven side rotor is coupled with a crankshaft (not shown) that serves as a driving shaft of the engine by means of a chain (not shown) to transmit driving force from the crankshaft. It rotates synchronously with the crankshaft. A camshaft  2  that serves as a driven shaft receives a driving force from the chain sprocket  10  to operate a suction valve (not shown). The camshaft  2  is capable of rotating with a predetermined phase difference with respect to the chain sprocket  10 , that is, crankshaft. The chain sprocket  10  and the camshaft  2  rotate clockwise when viewed in the direction of arrow X in FIG.  1 . This rotation direction is referred to as the advance direction. 
     A thin plate-like intermediate plate  17  is disposed between the chain sprocket  10  and a shoe housing  12 . The intermediate plate  17  prevents working fluid from leaking between the chain sprocket  10  and the shoe housing  12 . The chain sprocket  10 , the shoe housing  12 , and the intermediate plate  17  provide a housing member that serves as a driving side rotor, and are fixed one another with bolts  20  coaxially. The shoe housing  12  comprises a cylindrical peripheral wall  13  and a front plate  14  that serves as the other side wall of the housing member and formed into a single piece. 
     As shown in FIG. 2, the shoe housing  12  has a plurality of shoes  12   a,    12   b  and  12   c  that are formed in the shape of trapezoid with approximately the same angular interval in the circumferential direction. Three fan-shaped accommodation chambers  50  are provided for accommodating vanes  15   a,    15   b  and  15   c  that serve as vane members respectively among the shoes  12   a,    12   b  and  12   c  in the peripheral direction. The cross section of the inner peripheral surface of the shoes  12   a,    12   b  and  12   c  is formed in the shape of arc. 
     The vane rotor  15  that serves as a driven side rotor has three vanes  15   a,    15   b  and  15   c  with approximately the same angular interval in the circumferential direction. The vanes  15   a,    15   b  and  15   c  are accommodated to be capable of rotating in respective accommodation chambers  50 . Each vane divides each accommodation chamber  50  into a retard hydraulic chamber  54 ,  55 ,  56 , and an advance hydraulic chamber  51 ,  52 ,  53 . The arrow for indicating the retard direction and advance direction in FIG. 2 represents the retard direction and advance direction of the vane rotor  15  with respect to the shoe housing  12 . 
     As shown in FIG. 1, the vane rotor  15  and a bushing  22  are fixed to the camshaft  2  with a bolt  21  into a single piece and provide a driven side rotor. A pin  23  is provided for positioning the vane rotor  15  with respect to the camshaft  2  in the rotation direction. 
     The camshaft  2  and bushing  22  are fitted in the inner peripheral wall  10   a  of the chain sprocket  10  and the inner peripheral wall  14   a  of the front plate  14  relatively capable of rotating. Therefore, the camshaft  2  and vane rotor  15  are relatively capable of rotating coaxially with respect to the chain sprocket  10  and the shoe housing  12 . The inner peripheral wall  10   a  of the chain sprocket  10  and the inner peripheral wall  14   a  of the front plate  14  provide a bearing member of the driven side rotor. 
     A spring  24  that serves as advance urging means is accommodated in a cylindrical recess  11  formed on the chain sprocket  10 . The one end of the spring  24  is engaged with a fitting bore  11   a  of the recess  11 , and the other end is engaged with the vane rotor  15  through a slotted hole  17   a  formed on the intermediate plate  17 . 
     The load that occurs when the camshaft  2  drives the suction valve fluctuates between positive side and negative side. Herein the positive direction of the load torque represents the retard direction of the vane rotor  15  with respect to the shoe housing  12 , and the negative direction of the load torque represents the advance direction of the vane rotor  15  with respect to the shoe housing  12 . The load torque is exerted in the positive direction, that is, retard direction in average. The urging force of the spring  24  is exerted as a torque so that the vane rotor  15  is rotated in the advance side with respect to the shoe housing  12 . The magnitude of the torque in the advance direction exerted on the vane rotor  15  by the spring is approximately the same as the average load torque applied to the camshaft  2 . 
     Sealing members  26  are fitted on the outer peripheral wall of the vane rotor  15  as shown in FIG. 2. A small clearance is formed between the outer peripheral wall of the vane rotor  15  and the inner peripheral wall of the peripheral wall  13 . Each sealing member  26  prevents leakage of working fluid between the hydraulic chambers  50  through the clearance. The sealing member  26  is pressed against the peripheral wall  13  by means of the urging force of a plate spring  27  shown in FIG.  1 . 
     Guide rings  30  and  31  are press-fitted and held in the inner wall of the vane  15   a  that forms an accommodation hole  38 , and a cylindrical stopper piston  32  that serves as a contact member is accommodated in the guide rings  30  and  31  capable of sliding in the rotation axis direction of the camshaft  2 . A fitting member  40  that serves as a contacted member shown in FIG. 1 having a circular cross section is press-fitted and held in a recess  14   b  formed on the front plate  14 . On the fitting member  40 , a fitting bore  41  with which the stopper piston  32  is in contact and capable of fitting is formed, and an enlarged bore  43  is formed. The enlarged bore  43  has the retard side end surface on the same plane as that of the retard side end surface of the fitting bore  41 . The bore  43  is shallower than the fitting bore  41  and extends to the advance side. 
     As shown in FIGS. 3A to  3 C, a tapered top end  33  of stopper piston  32  has the diameter that decreases toward the fitting direction, and the fitting bore  41  is also tapered at approximately the same angle as that of the inclination of the top end  33 . Therefore, the stopper piston  32  is fitted in the fitting bore  41  smoothly. Furthermore, because the fitting bore  41  is fitted with the stopper piston  32  without excessive play, generation of hammering sound due to fluctuation of the load torque is minimized. Furthermore, because the contact area of the top end  33  that is in contact with the fitting bore  41  is large, the stress applied to the top end  33  is reduced, and the life of the stopper piston  32  is extended. 
     A spring  37  that serves as contact urging means urges the stopper piston  32  against the fitting member  40 . The stopper piston  32 , the fitting member  40  and the spring  37  provide constraint means. Furthermore, the stopper piston  32  and the fitting member  40  provide regulation means. 
     The stopper piston  32  that is cylindrical having a bottom comprises the top end  33 , a large diameter sliding portion  34  and a small diameter sliding portion  35  located in the order from the front plate  14  side. A ring taper surface  33   a  is formed on the outer periphery of the top end  33 . The angle of the taper surface  33   a  is approximately the same as the taper angle of the fitting bore  41 . 
     The retard hydraulic pressure that acts as the first working fluid pressure is applied to the top end surface  33   b  that serves as the first pressure receiving portion formed on the top end  33  from a hydraulic chamber  42 , and the retard hydraulic pressure is also applied to the annular surface  34   a  that serves as the third pressure receiving portion formed on the fitting bore side of the larger diameter sliding portion  34  from a hydraulic chamber  45 . The retard hydraulic pressure that is applied to the top end surface  33   b  and the annular surface  34   a  acts in the direction to push out the stopper piston  32  from the fitting bore  41 . 
     The annular surface  34   b  formed on the side opposite to the fitting bore side of the large diameter sliding portion  34  as the second pressure receiving portion receives the advance hydraulic pressure as the second working fluid pressure from a hydraulic chamber  46  that communicates to an advance hydraulic chamber  54  through a fluid passage  48  and a through hole  30   b  in the state that the stopper piston  32  is fitted in the fitting bore  41  or the enlarged bore  43 , that is, in the constraint state as shown in FIG.  3 A and FIG.  3 B. 
     In FIG.  3 A and FIG. 3B, the hydraulic pressure of the hydraulic chamber  46  acts in the direction to fit the stopper piston  32  in the fitting bore  41 . As shown in FIG. 3C, when the stopper piston  32  is pushed out from the enlarged bore  43 , that is, at the boundary position between unconstraint state and constraint state associated with the stopper piston  32  and the fitting member  40 , the through hole  30   b  that serves as the second working fluid passage is closed by the large diameter sliding portion  34 . Thus, the communication between the hydraulic chamber  46  and the advance hydraulic chamber  54  is shut down. At this time, the hydraulic pressure of the hydraulic chamber  46  is equalized to the atmospheric pressure, and does not act to push the stopper piston  32  toward the fitting member  40 . 
     The accommodation hole  38  of the side opposite to the fitting member side of the stopper piston  32  is open to the atmosphere through the slotted hole  17   a  formed on the intermediate plate  17  and a fluid passage  10   b  formed on the chain sprocket  10  not only when the vane rotor  15  is located within the relative rotation angle range, that is, at the most advanced position with respect to the shoe housing  12  as shown in FIG. 4 but also when the vane rotor is located at the most retarded position. Therefore, the hydraulic pressure of the working fluid that leaked from the sliding clearance between the small diameter sliding portion  35  and the guide ring  31  to the accommodation hole  38  of the side opposite to the fitting member side of the stopper piston  32  is approximately equal to the atmospheric pressure. Therefore, the working fluid that leaked to the accommodation hole  38  of the side opposite to the fitting member side of the stopper piston  32  does not act as the force to push the stopper piston  32  toward the fitting member  32 . 
     Sliding portions of the stopper piston  32  slide on the inner peripheral wall of the guide ring  30  or guide ring  31 . The top end  33  of the stopper piston  32  can be fitted in the fitting bore  41  when the vane rotor  15  is positioned at the intermediate position between the most retarded position and the most advanced position with respect to the shoe housing  12  as shown in FIG.  2 . 
     In the state that the stopper piston  32  is fitted in the fitting bore  41 , the relative rotation of the vane rotor  15  with respect to the shoe housing  12  is constrained. As shown in FIG. 3A, when the stopper piston  32  is fitted in the fitting bore  41 , the intermediate position where the relative rotation between the shoe housing  12  and the vane rotor  15  is the position that sets the optimal phase difference between the crankshaft and the camshaft  2 , that is, the optimal valve timing of the suction valve that enables the starting of the engine surely. 
     When the vane rotor  15  is rotated to the retard side with respect to the shoe housing  12  from the state shown in FIG. 3C, the circumferential position of the stopper piston  32  deviates from that of the fitting bore  41 . It becomes impossible that the stopper piston  32  is fitted in the fitting bore  41 . When the vane rotor  15  is rotated up to the most advanced angle from the intermediate position with respect to the shoe housing  12 , the stopper piston  32  locates on the enlarged bore  43  as shown in FIG.  3 B. 
     A fluid passage  44  formed on the front plate  14  communicates between a retard hydraulic chamber  51  and the hydraulic chamber  42 . A through hole  30   a  that passes through the guide ring  30  is formed on the guide ring  30 . A fluid passage  47  and the through hole  30   a  communicate between the retard hydraulic chamber  51  and the hydraulic chamber  45 . The through hole  30   b  formed on the guide ring  30  can communicate between the hydraulic chamber  46  and the fluid passage  48 . 
     As shown in FIG. 2, the retard hydraulic chamber  51  is formed between the shoe  12   a  and the vane  15   a.  The retard hydraulic chamber  52  is formed between the shoe  12   b  and the vane  15   b.  The retard hydraulic chamber  53  is formed between the shoe  12   c  and the vane  15   c.  Furthermore, the advance hydraulic chamber  54  is formed between the shoe  12   c  and the vane  15   a.  The advance hydraulic chamber  55  is formed between the shoe  12   a  and the vane  15   b.  The advance hydraulic chamber  56  is formed between the shoe  12   b  and the vane  15   c.    
     The retard hydraulic chamber  51  communicates to a fluid passage  61 . The retard hydraulic chambers  52  and  53  communicate to a fluid passage  60  formed in C-shape on the camshaft side end surface of the boss portion  15   d  shown in FIG.  2  through oil passages  62  and  63 . Furthermore, the retard hydraulic chambers  51 ,  52  and  53  communicate to a fluid passage  200  formed on the camshaft  2  shown in FIG.  1  through the fluid passages  60  and  61 . 
     As shown in FIG. 2, the advance hydraulic chamber  55  communicates to a fluid passage  72 . The advance hydraulic chambers  54  and  56  communicate to a fluid passage  70  formed in C-shape on the bushing side end surface of the boss  15   d  through oil passages  71  and  73 . Furthermore, the advance hydraulic chambers  54 ,  55  and  56  communicate to a fluid passage  201  formed on the camshaft shown in FIG. 1 through a fluid passage (not shown) formed in the axial direction of the boss portion  15   d  from the fluid passages  70  and  72 . 
     The fluid passage  200  communicates to a groove passage  202  formed on the outer peripheral wall of the camshaft  2 . The fluid passage  201  communicates to a groove passage  203  formed on the outer peripheral wall of the camshaft  2 . The groove passage  202  is connected to a switching valve  212  through a fluid passage  204 . The groove passage  203  is connected to the switching valve  212  through a fluid passage  205 . An oil supply passage  206  that serves as a working fluid supply passage is connected to a fluid pump  210 . An oil drain passage  207  that serves as a working fluid discharging passage is open to a drain  211 . The oil pump  210  pumps up working fluid from the drain and supplies it to hydraulic chambers through the switching valve  212 . The switching valve  212  is a well known 4-port guide valve. 
     A valve member  213  of the switching valve  212  is urged in one direction by a spring  214 , and reciprocated by controlling a current supplied to a solenoid  215 . The current supplied to the solenoid  215  is controlled by an engine control unit (ECU)  300 . The ECU  300  receives the detection signals from various sensors and transmits the signal to components of the engine. By reciprocating the valve member  213 , the combination of communication and shutdown between the fluid passages  204  and  205 , the oil supply passage  206  and the oil drain passage  207  is switched. The above oil passage structure allows working fluid to be supplied from the oil pump  210  to the retard hydraulic chambers  51 ,  52  and  53 , or the advance hydraulic chambers  54 ,  55  and  56 , and the hydraulic chambers  42 ,  45  and  46 . It also allows the working fluid to be drained from oil pressure chambers to the drain  211 . 
     In operation, when an ignition is turned off to stop the engine, a valve position  213   a  is selected because the ECU  300  turns off a current supplied to the solenoid  215 . Then, working fluid is supplied to the advance hydraulic chambers, and the retard hydraulic chambers. The hydraulic chambers  42  and  45  are opened to the drain. Thereby, the vane rotor  15  is rotated to the advance side with respect to the shoe housing  12 . 
     At this time, when the stopper piston  32  is separated from the fitting member  40  far from the position as shown in FIG. 3C, that is, when the stopper piston  32  is in unconstraint from the fitting bore  41  and the enlarged bore  43 , the communication between the hydraulic chamber  46  and the advance hydraulic chamber  54  is shut down by the large diameter sliding portion  34 . Therefore, the hydraulic pressure of the hydraulic chamber  46  does not act to push the stopper piston  32  toward the fitting member  40 . However, because the hydraulic pressure in the hydraulic chambers  42  and  45  decrease, the urging force of the spring  37  pushes the stopper piston  32  to move toward the fitting member  40 . 
     When an engine stop is indicated in the state that the vane rotor  15  is positioned with deviation to the retard side with respect to the shoe housing  12  from the intermediate position (constraint position) where the stopper piston  32  is fitted in the fitting bore  41 , the working fluid is supplied to the advance hydraulic chambers to thereby rotate the vane rotor  15  to the advance side. The stopper piston  32  is moved toward the fitting member  40  by means of the urging force of the spring  37 , and the unconstraint state changes to the constraint state. At this time, the large diameter sliding portion  34  releases the closed through hole  30   b,  and the through hole  30   b  begins to open. 
     Then, the hydraulic chamber  46  becomes communicative to the advance hydraulic chamber  54  through the through hole  30   b,  and the working fluid is supplied from the advance hydraulic chamber  54  to the hydraulic chamber  46 . Therefore, the hydraulic pressure of the hydraulic chamber  46  acts as a pushing force that pushes the stopper piston  32  toward the fitting member  40 . 
     When the vane rotor  15  reaches the intermediate position (constraint position) shown in FIG. 3A with respect to the shoe housing  12 , the stopper piston  32  is fitted in the fitting bore  41  by means of the urging force of the spring  37  and a force supplied from the hydraulic chamber  46 . If the stopper piston  32  cannot be fitted in the fitting bore  41 , the vane rotor  15  is rotated toward the advance side beyond the intermediate position and fitted with the enlarged bore  43 . 
     When an engine stop is instructed in the state that the vane rotor  15  is positioned at the advance side with respect to the shoe housing  12  with deviation from the intermediate position where the stopper piston  32  is to be fitted in the fitting bore  41 , the vane rotor  15  is rotated to the advance side and the stopper piston  32  is resultantly fitted in the enlarged bore  43 . 
     When the stopper piston  32  is fitted in the fitting bore  41  before starting of the engine, the phase difference of the vane rotor  15  with respect to the shoe housing  12 , that is, the phase difference of the camshaft  2  with respect to the crankshaft is maintained at the most preferable position for starting the engine. Thus, the engine can be started surely within a short time. 
     It is assumed here that the engine is started in the state that the stopper piston  32  is not fitted in the fitting bore  41  before the engine is started and the camshaft  2  is positioned at the advance side from the intermediate position with respect to the crankshaft. In this instance, the stopper piston  32  is fitted in the enlarged bore  43 . Because the advance torque applied to the vane rotor  15  and the camshaft  2  by the spring  24  is approximately equal to the averaged load torque, the maximum value of the load torque exerted in the retard direction of the positive side is larger than the urging force of the spring  24 . The vane rotor  15  swings to the retard side with respect to the shoe housing  12  against the urging force of the spring  24  that is exerted in the advance direction with changing of the load torque. 
     The vane rotor  15  is stopped on the retard side surface of the enlarged bore  43  at the intermediate position. The working fluid is not introduced into the hydraulic chambers  42  and  45  during cranking when the engine is to be started. When the stopper piston  32  reaches the intermediate position, the stopper piston  32  is fitted in the fitting bore  41  by means of the urging force of the spring  37  and the force received from the hydraulic chamber  46 . 
     The stopper piston  32  is fitted in the enlarged bore  43  even when the stopper piston  32  is not fitted in the fitting bore  41  before the engine is started. When the engine is started, the stopper piston  32  is fitted in the fitting bore  41  quickly, and the camshaft  2  is held at the intermediate position with respect to the crankshaft. As a result, the engine is started surely in a short time. 
     Because the valve position  213   a  of the switching valve  212  is selected during cranking when the engine is to be started, the working fluid is supplied to the advance hydraulic chambers and the hydraulic chamber  46 , and the retard hydraulic chambers and the hydraulic chamber  42  are opened to the drain. Therefore, the stopper piston  32  will not be pulled out from the fitting bore  41  or the enlarged bore  43 . 
     After the engine is started, the working fluid is charged to the retard hydraulic chambers and the hydraulic pressure of the hydraulic chambers  42  and  45  increases up to a predetermined pressure. Then, the stopper piston  32  is pulled out from the fitting bore  41 . The relative rotation of the vane rotor  15  with respect to the shoe housing  12 , that is, the phase control becomes possible. When the stopper piston  32  moves from the fitting bore  41  in the unconstraint direction shown in FIG. 3C, the through hole  30   b  is closed by the large diameter sliding portion  34 . The communication between the hydraulic chamber  46  and the advance hydraulic chamber  54  is shut down. The hydraulic chamber  46  is almost sealed. 
     The hydraulic pressure of the working fluid increases to a sufficient value after the engine is started. Then, either one of the valve portions  213   a,    213   b  and  213   c  of the valve member  213  is selected depending on the instruction given by the ECU  300 . Thereby, the supply of the working fluid to the hydraulic chambers and drain of the working fluid from the hydraulic chambers are controlled. The relative rotation of the vane rotor  15  with respect to the shoe housing  12  is controlled. 
     While the engine is being operated normally, the stopper piston  32  is kept at the position far from the position where the stopper piston  32  is just pulled out as shown in FIG.  3 C. Therefore, the hydraulic chamber  46  is almost sealed as described above. Even though the hydraulic pressure of the hydraulic chambers  42  and  45  decrease so that the stopper piston  32  is to be moved toward the fitting member  40 , the hydraulic pressure  46  acts as a damper chamber and the moving speed is reduced. 
     Therefore, even though the stopper piston  32  is to be moved toward the fitting member  40  due to reduction of the hydraulic pressure when the stopper piston  32  passes on the fitting member  40  concomitantly with the relative rotation of the vane rotor  15  with respect to the shoe housing  12 , the hydraulic chamber  46  acts as a damper chamber and the stopper piston  32  passes on the fitting member  40  without fitting with the fitting member  40 , and thus the stopper piston  32  is prevented from being fitted with the fitting member  40 . 
     The first working fluid pressure is assigned to the retard side and the second working fluid pressure is assigned to the advance side. The advance pressure is increased when the engine is to be stopped to thereby help the fitting of the stopper piston  32  for stopping. 
     (Second Embodiment) 
     In a second embodiment shown in FIG. 6A, the stopper piston  32  is provided with only one pressure receiving portion for receiving the retard hydraulic pressure as the first pressure receiving portion at the top end surface  32   a  of the top end. The second pressure receiving portion for receiving the advance hydraulic pressure is formed as an annular surface of the top end on the side opposite to the fitting member  40 . 
     When the stopper piston  32  is pulled out entirely from the fitting bore  41  and the enlarged bore  43  and brought into the unconstraint state, a through hole  30   b  is closed by the top end. Thereby, the communication between the hydraulic chamber  46  and the advance hydraulic chamber  54  is shut down, and the hydraulic chamber  46  acts as a damper chamber. 
     The taper angle θ of the top end is formed to be 15 degrees or less. Because the taper angle θ is sharp, a frictional force that overcomes the load torque that the camshaft  2  receives is generated in the space of the fitting bore  41  formed on the fitting member  40  by means of the force received from the spring  37  and the advance hydraulic pressure of the hydraulic chamber  46 . As a result, the stopper piston  32  is kept fitted in the fitting bore  41 . Furthermore, the variation of the fitting depth of the stopper piston  32  that is fitted in the fitting bore  41  is reduced. 
     The fitting bore  41  formed on the fitting member  40  is a slotted hole that extends in the rotation direction of the stopper piston  32 , that is, in the direction perpendicular to the rotation direction of the vane rotor  15  as shown in FIG.  6 B. In detail, the diameter D 2  of the fitting bore  41  in the direction perpendicular to the rotation direction is larger than the diameter D 1  of the fitting bore  41  in the rotation direction. 
     Even if the fitting bore  41  or stopper piston  32  has some manufacturing allowance in the direction perpendicular to the rotation direction, the stopper piston  32  can be fitted in the fitting bore  41 . The limitation on the manufacturing allowance can be mitigated. As a result, the manufacturing becomes easy and the manufacturing cost is reduced. 
     In the first and second embodiments, the retard hydraulic pressure is applied to the stopper piston in the direction to pull out the stopper piston from the fitting bore and the enlarged bore, and the advance hydraulic pressure is applied to the stopper piston in the direction to push the stopper piston in the fitting member. Therefore, the retard hydraulic chamber is opened to the drain and the working fluid is supplied to the advance hydraulic chamber when an engine stop is instructed. The stopper piston can be thereby fitted surely in the fitting bore at the intermediate position. Because the engine is started in the state that the vane rotor is held at the intermediate position with respect to the shoe housing, the engine can be started surely in a short time. 
     In addition to the constraint means for constraining the vane rotor at the intermediate position with respect to the shoe housing by fitting the stopper piston in the fitting bore, the enlarged bore serving as regulation means for preventing the vane rotor from rotating from the intermediate position toward the retard side and for allowing the vane rotor to rotate toward the advance side is formed. Therefore, the stopper piston is fitted in the enlarged bore and stopped at the retard side of the enlarged bore, and the stopper piston is thereby fitted surely with the fitting bore. As a result, the engine is stopped in the state that the vane rotor is held at the intermediate position with respect to the shoe housing, which position is most suitable for engine starting. Therefore, the engine can be started surely in a short time. 
     Because the through holes  30   b  and  30   b  that communicate between the hydraulic chamber  46  and the advance hydraulic chamber  54  are closed/opened by displacing the stopper piston, the through holes  30   b  and  30   b  are surely opened/closed by displacing the stopper piston  32 . Furthermore, because other opening/closing valves and switching valves are not needed for opening/closing the second working fluid passage that communicates between the hydraulic chamber  46  and the advance hydraulic chamber  54 , the number of necessary parts is reduced, the assembling work becomes simple, and the manufacturing cost is reduced. 
     (Third Embodiment) 
     In a third embodiment shown in FIGS. 7A-7C to  11 , the top end surface  33   b  that serves as the first pressure receiving portion formed on the top end  33  receives the retard hydraulic pressure that serves as the first working fluid pressure from the hydraulic chamber  42 . The annular surface  34   a  that serves as the second pressure receiving portion formed on the fitting bore side of the large diameter sliding portion  34  receives the advance hydraulic pressure from the hydraulic chamber  45  and the retard hydraulic pressure exerted on the top end surface  33   b.  The advance hydraulic pressure exerted on the annular surface  34   a  act in the direction to pull out the stopper piston  32  from the fitting bore  41 . The hydraulic chamber  42  communicates to the retard hydraulic chamber  51  through the fluid passage  44  formed on the front plate  14 . The hydraulic chamber  45  communicates to the advance hydraulic chamber  54  through the fluid passage  47  formed on the vane  15   a  and the through hole  30   a  formed on the guide ring  30 . 
     The fluid passage  47  and the through hole  30   a  provide the second pressure receiving passage. The pressure receiving area of the top end surface  33   b  is larger than the pressure receiving area of the annular surface  34   a  and the annular surface  34   b  that serves as the third pressure receiving portion that will be described hereinafter. Furthermore, the pressure receiving area of the annular surface  34   a  is larger than the pressure receiving area of the annular surface  34   b.    
     The annular surface  34   b  that serves as the third pressure receiving portion formed on the side opposite to the fitting bore side of the large diameter sliding portion  34  receives the advance hydraulic pressure that serves as the second working fluid pressure from the hydraulic chamber  46 . The hydraulic chamber  46  communicates to the advance hydraulic chamber  54  through the fluid passage  48  formed on the vane  15   a  and the through hole  30   b  formed on the guide ring  30 . The fluid passage  48  and the through hole  30   b  provide the third pressure receiving passage. 
     As shown in FIG. 7A, in the state that the stopper piston  32  is fitted in the fitting bore  41 , the through hole  30   a  is closed by the large diameter sliding portion  34 . Then, because the working fluid in the advance hydraulic chamber  54  is not supplied to the hydraulic chamber  45 , the hydraulic pressure of the hydraulic chamber  45  does not act in the direction to pull out the stopper piston  32  from the fitting bore  41 . 
     Furthermore, as shown in FIG. 7C, when the stopper piston  32  is pulled out from the enlarged bore  43 , that is, at the boundary position between the unconstraint state and the constraint state associated with the stopper piston  32  and the fitting member  40 , the through hole  30   b  is closed by the large diameter sliding portion  34 . The working fluid in the advance hydraulic chamber  54  is not supplied to the hydraulic chamber  46 . At this time, because the hydraulic pressure of the hydraulic chamber  46  is equal to the atmospheric pressure, the hydraulic pressure does not act as the force to push the stopper piston  32  toward the fitting member  49 . 
     As shown in FIG. 7C, when the vane rotor  15  rotates toward the retard side with respect to the shoe housing  12  in the state that the stopper piston  32  is pulled out from the fitting bore  41  and the enlarged bore  43 , the circumferential position of the stopper piston  32  and that of the fitting bore  41  are deviated each other. As a result, it becomes impossible for the stopper piston  32  to be fitted in the fitting bore  41 . 
     In operation of the third embodiment, when an ignition is turned off to stop the engine, a valve position  213   a  is selected because the ECU  300  turns off a current supplied to the solenoid  215 . Then, working fluid is supplied to the advance hydraulic chambers and the hydraulic chambers  45  and  46 . The retard hydraulic chambers and the hydraulic chamber  42  are opened to the drain. Thereby, the vane rotor  15  is rotated to the advance side with respect to the shoe housing  12 . 
     At this time, when the stopper piston  32  is separated from the fitting member  40  far from the position as shown in FIG. 3C, that is, when the stopper piston  32  is in unconstraint from the fitting bore  41  and the enlarged bore  43 , the communication between the hydraulic chamber  46  and the advance hydraulic chamber  54  is shut down by the large diameter sliding portion  34 . Therefore, the hydraulic pressure of the hydraulic chamber  46  does not act to push the stopper piston  32  toward the fitting member  40 . However, because the hydraulic pressure in the hydraulic chamber  42  decrease, the urging force of the spring  37  pushes the stopper piston  32  to move toward the fitting member  40 . 
     When an engine stop is indicated in the state that the vane rotor  15  is positioned with deviation to the retard side with respect to the shoe housing  12  from the intermediate position (constraint position) where the stopper piston  32  is fitted in the fitting bore  41 , the working fluid is supplied to the advance hydraulic chambers to thereby rotate the vane rotor  15  to the advance side. The stopper piston  32  is moved toward the fitting member  40  by means of the urging force of the spring  37 , and the unconstraint state changes to the constraint state. At this time, the large diameter sliding portion  34  releases the closed through hole  30   b,  and the through hole  30   b  begins to open. 
     Then, the hydraulic chamber  46  becomes communicative to the advance hydraulic chamber  54  through the through hole  30   b,  and the working fluid is supplied from the advance hydraulic chamber  54  to the hydraulic chamber  46 . Therefore, the hydraulic pressure of the hydraulic chamber  46  acts as a pushing force that pushes the stopper piston  32  toward the fitting member  40 . 
     As shown in FIG. 9, when the vane  15   b  is stopped by the shoe  12   b  and the vane rotor  15  reaches the most advanced position with respect to the shoe housing  12 , the stopper piston  32  is positioned in the enlarged bore  43  as shown in FIG.  7 B. 
     When the vane rotor  15  reaches the intermediate position (constraint position) shown in FIG. 7A with respect to the shoe housing  12 , the stopper piston  32  is stopped on the retard side end surface of the enlarged bore  43 . The stopper piston  32  is fitted in the fitting bore  41  by the urging force of the spring  37  and the force received from the hydraulic chamber  46 . When the stopper piston  32  is fitted in the fitting bore  41 , the through hole  30   a  is closed by the large diameter sliding portion  34 . Therefore, because the working fluid in the hydraulic chamber  45  does not act as a force to pull out the stopper piston  32  from the fitting bore  41 , the constraint state shown in FIG. 7A is held. If the stopper piston  32  fails to fit in the fitting bore  41 , then the vane rotor  15  rotates toward the advance side with respect to the intermediate position and fits in the enlarged bore  43 . 
     When an engine stop is instructed in the state that the vane rotor  15  is positioned on the advance side with respect to the shoe housing  12  from the intermediate position where the stopper piston  32  is fitted in the fitting bore  41 , the vane rotor  15  rotates toward the advance side. The stopper piston  32  is thereby fitted in the enlarged bore  43 . 
     In the case that the stopper piston  32  is fitted in the fitting bore  41  before the engine is started, the phase difference of the vane rotor  15  with respect to the shoe housing  12 , that is, the phase difference of the camshaft  2  with respect to the crankshaft, is held in the most preferable phase for starting the engine. As a result, the engine can be started surely in a short time. 
     It is assumed that the engine is started in the state that the stopper piston  32  is not fitted in the fitting bore  41  before the engine is started and the camshaft  2  is positioned on the advance side to the crankshaft with respect to the intermediate position. At this time, the stopper piston  32  is fitted in the enlarged bore  43 . Because the advance torque exerted on the vane rotor  15  and the camshaft  2  by the spring  24  is approximately equal to the averaged load torque, the maximum value of the load torque exerted in the positive side retard direction is larger than the urging force of the spring  24 . 
     Because the working fluid is not supplied to the retard hydraulic chambers and the advance hydraulic chambers during cranking when the engine is to be started, the vane rotor  15  swings toward the retard side with respect to the shoe housing  12  against the urging force of the spring  24  that is exerted in the advance direction concomitantly with the variation of the load torque. The vane rotor  15  is stopped on the surface of the retard side of the enlarged bore  43  at the intermediate position. 
     When the stopper piston  32  reaches the intermediate position, the stopper piston  32  is fitted in the fitting bore  41  by means of the urging force of the spring  37  and the force received from the hydraulic chamber  46  because the working fluid is not introduced in the hydraulic chambers  42  and  45 . 
     The stopper piston  32  is fitted in the enlarged bore  43 , even though the stopper piston  32  is not fitted in the fitting bore  41  before the engine is started. The stopper piston  32  is fitted in the fitting bore  41  promptly when the engine is started, the camshaft  2  is held at the intermediate position with respect to the crankshaft, and thereby the engine is started surely in a short time. 
     Because the valve position  213   a  of the switching valve  212  is selected during cranking when the engine is to be started, the working fluid is supplied to the advance hydraulic chambers and the hydraulic chambers  45  and  46 . The retard hydraulic chambers and the hydraulic chamber  42  are opened to the drain. Furthermore, in the state that the stopper piston  32  is fitted in the fitting bore  41  as shown in FIG. 7A, the through hole  30   a  is closed by the large diameter sliding portion  34 . Thus, the working fluid in the hydraulic chamber  45  does not exert a force to pull out the stopper piston  32  from the fitting bore  41 . Therefore, the stopper piston  32  is not pulled out from the fitting bore  41 . 
     After the working fluid is charged in the retard hydraulic chamber and the hydraulic pressure increases up to a predetermined pressure after the engine is started, the stopper piston  32  is pulled out from the fitting bore  41 , the relative rotation of the vane rotor  15  with respect to the shoe housing  12 , that is, the phase control becomes possible. Because the through hole  30   b  is closed by the large diameter sliding portion  34  when the stopper piston  32  moves in the unconstraint direction shown in FIG. 7C from the fitting bore  41 , communication between the hydraulic chamber  46  and the advance hydraulic chamber  54  is shut down, and the hydraulic chamber  46  is almost sealed. 
     When the hydraulic pressure of the working fluid increases sufficiently after the engine is started, the any one of the valve positions  213   a,    213   b  and  213   c  of the valve member  213  is selected correspondingly to the instruction supplied from the ECU  300 . Thereby, supply of the working fluid to the hydraulic chambers and discharge of the working fluid from the hydraulic chambers are controlled. The relative rotation of the vane rotor with respect to the shoe housing  12  is controlled. 
     The stopper piston  32  is positioned at the place farther from the position shown in FIG. 7C in the pulling out direction. Therefore, the hydraulic chamber  46  is almost sealed as described above, when the stopper piston  32  is to be moved toward the fitting member  40  due to reduction of the hydraulic pressure of the hydraulic chambers  42  and  45 . The hydraulic chamber  46  functions as a damper chamber to thereby reduce the moving speed. 
     Therefore, when the stopper piston  32  passes through the intermediate position during advance angle control, the stopper piston  32  passes on the fitting member  40  before the stopper piston  32  is fitted in the fitting member  40  by means of the damper action of the hydraulic chamber  46  in addition to the advance hydraulic pressure exerted on the annular surface  34   a.  As a result, the stopper piston  32  is prevented from being fitted with the fitting member  40 . 
     When the stopper piston  32  passes through the intermediate position during retard angle control, the stopper piston  32  passes on the fitting member  40  before the stopper piston  32  is fitted with the fitting member  40  by means of the damper action of the hydraulic chamber  46  in addition to the retard hydraulic pressure exerted on the tope end surface  33   b.  The stopper piston  32  is prevented from being fitted with the fitting member  40 . The stopper piston  32  has the top end surface  33   b  on which the retard hydraulic pressure is exerted in the direction to pull out the stopper piston  32  from the fitting member  40 , and has the annular surface  34   a  on which the advance hydraulic pressure is exerted in the direction to pull out the stopper piston  32  from the fitting member  40 . As a result, the stopper piston  32  is held in the unconstraint state associated with the fitting member  40 . Furthermore, because the hydraulic chamber  46  functions as a damper chamber in the unconstraint state, the stopper piston  32  is held in the unconstraint state associated with the fitting member  40 . 
     In the third embodiment, the through hole  30   a  that communicates between the hydraulic chamber  45  and the advance hydraulic chamber  54  and the through hole  30   b  that communicates between the hydraulic chamber  46  and the advance hydraulic chamber  54  are opened/closed by displacing the stopper piston  32 . Thus, the through holes  30   a  and  30   b  are opened/closed surely by displacing the stopper piston  32 . Because other open/close valves and switching valves are not needed for opening/closing the through holes  30   a  and  30   b,  the number of needed parts is reduced, assembling work becomes simple, and the manufacturing cost is reduced. 
     Furthermore, the pressure receiving area of the top end surface  33   b  is larger than that of the annular surface  34   a  and the annular surface  34   b.  Therefore, even though the retard hydraulic pressure decreases due to pulsation, the stopper piston  32  and the fitting member  40  are held in the unconstraint state by means of the force received from the retard hydraulic pressure. 
     Furthermore, the force received from the hydraulic chamber  45  in the direction to pull out the stopper piston  32  from the fitting bore  41  is larger than the force received from the hydraulic chamber  46  in the direction to push the stopper piston  32  toward the fitting member  40 . Therefore, the unconstraint state associated with the stopper piston  32  and the fitting member  40  can be held during normal operation of the engine. 
     (Fourth Embodiment) 
     In a fourth embodiment shown in FIGS. 12A and 12B, the stopper piston  32  has the top end surface  33   a  that serves as the first pressure receiving portion formed on the top end, the annular surface  34   a  that serves as the second pressure receiving portion formed on the fitting bore side of the large diameter sliding portion  34  and the annular surface  34   b  that serves as the third pressure receiving portion formed on the side opposite to the fitting bore side of the large diameter sliding portion  34 . The pressure receiving area of the top end surface  32   a  is larger than the pressure receiving surface of the annular surface  34   a  and the annular surface  34   b.  Furthermore, the pressure receiving area of the annular surface  34   a  is larger than the pressure receiving surface of the annular surface  34   b.    
     It is possible that the through hole  30   a  that serves as the second pressure receiving passage formed on the guide ring  30  supplies the working fluid of the advance hydraulic pressure to the hydraulic chamber  45 . The through hole  30   a  is restricted at some portion of the passage. When the stopper piston  32  is to be moved toward the fitting member  40  side, the restricted passage of the through hole  30   a  functions to reduce the speed of motion of the stopper piston  32  toward the fitting member  40 . Therefore, the fitting of the stopper piston  32  in the fitting member  40  due to reduction of the working fluid hydraulic pressure during normal operation of the engine is prevented, and the phase is controlled smoothly. 
     The through hole  30   b  that serves as the third pressure receiving passage formed on the guide ring  30  supplies the working fluid of the advance hydraulic pressure to the hydraulic chamber  46 . As shown in FIG. 12B, the through hole  30   b  is closed by the large diameter portion  34  when the stopper piston  32  is positioned farthest from the fitting member  40 , but is opened when the stopper piston  32  moves only slightly toward the fitting member  40  side from the position shown in FIG.  12 B. Therefore, the hydraulic chamber  46  functions to push the stopper piston  32  toward the fitting member  40  when the working fluid of the advance hydraulic pressure is supplied, and does not act as a damper chamber. 
     The taper angle θ of the top end  34  of the stopper piston  32  is smaller than 15 degrees as in the second embodiment (FIG.  6 A). Further, the diameter D 2  of the fitting bore  41  in the direction perpendicular to the rotation direction is larger than the diameter D 1  of the fitting bore  41  in the rotation direction as in the second embodiment (FIG.  6 B). 
     Even if the fitting bore  41  or the stopper piston  32  has some manufacturing allowance in the direction perpendicular to the rotation direction, the stopper piston  32  can be fitted in the fitting bore  41 . Because the limit of the manufacturing allowance is eased, the manufacturing cost is reduced. 
     In the third and fifth embodiments, the retard hydraulic pressure and advance hydraulic pressure are exerted on the stopper piston in the direction to be pulled out from the fitting bore and enlarged bore. Either of the retard hydraulic pressure and the advance hydraulic pressure is exerted on the stopper piston in the direction to be pulled out from the fitting bore and the enlarged bore during phase control in normal operation of the engine. The stopper piston is prevented from being fitted in the fitting bore during normal operation of the engine. 
     Furthermore, the advance hydraulic pressure is exerted on the stopper piston in the direction to be pushed toward the fitting member. Therefore, when an engine stop is instructed, the stopper piston is surely fitted in the fitting bore at the intermediate position because the retard hydraulic chamber is opened to the drain and the working fluid is supplied to the advance hydraulic chamber. 
     In the third to fifth, the first pressure receiving portion for receiving the retard hydraulic pressure in the direction to pull out the stopper piston from the fitting bore and the second pressure receiving portion for receiving the advance hydraulic pressure in the direction to pull out the stopper piston from the fitting bore are formed separately on the stopper piston. Alternatively, one pressure receiving portion for receiving the hydraulic pressure in the direction to pull out the stopper piston from the fitting bore may be formed, and the retard hydraulic pressure and the advance hydraulic pressure may be switched by use of, for example, a differential pressure regulating valve to thereby exert the retard hydraulic pressure or the advance hydraulic pressure that has been switched to the pressure receiving portion. 
     The present invention should not be limited to the above disclosed embodiments, but may be implemented in many other ways. 
     For instance, the vale timing adjusting apparatus drives only the exhaust valve, or both the suction valve and exhaust valve. Further, the stopper piston may be moved in the radial direction to be fitted in the fitting bore. The stopper piston may be accommodated in the housing member side and the fitting bore, and the enlarged bore may be formed on the vane rotor side. A timing pulley or timing gear may be employed in place of the chain sprocket. The driving force of the crankshaft that serves as the driving shaft may be received by the vane member to rotate the camshaft that serves as the driven shaft and the housing member.