Patent Publication Number: US-8991346-B2

Title: Valve timing control apparatus

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is based on and incorporates herein by reference Japanese Patent Application No. 2012-265449 filed on Dec. 4, 2012. 
     TECHNICAL FIELD 
     The present disclosure relates to a valve timing control apparatus, which controls opening timing and closing timing of intake valves or exhaust valves of an internal combustion engine. 
     BACKGROUND 
     A known valve timing control apparatus controls opening timing and closing timing of intake valves or exhaust valves by changing a rotational phase between a crankshaft and a camshaft of an internal combustion engine installed in, for example, a vehicle. 
     JP2009-515090A (corresponding to US2007/0095315A1) recites a valve timing control apparatus that includes a hydraulic pressure control valve, which is installed in a vane rotor that is rotatable relative to a housing. More specifically, the hydraulic pressure control valve is installed in a center hole of the vane rotor, which extends in a direction of a rotational axis of the vane rotor. The hydraulic pressure control valve shifts from one oil passage to another oil passage to supply the oil, which is received from an oil pump, to advancing chambers or retarding chambers formed in the housing. In this way, the valve timing control apparatus can advance or retard the vane rotor relative to the housing. 
     However, the hydraulic pressure control valve of JP2009-515090A (corresponding to US2007/0095315A1) has an output port at a location that is projected from the center hole of the vane rotor to the outside of the housing. Therefore, in the hydraulic pressure control valve, the oil of the retarding chambers is discharged from the output port to the outside of the housing at the time of supplying the oil to the advancing chambers. Also, the oil of the advancing chambers is discharged from the output port to the outside of the housing at the time of supplying the oil to the retarding chambers. Therefore, it is difficult to use a drive belt, such as a toothed belt, a flat belt or a V-belt, in a drive force transmission mechanism located between the crankshaft of the engine and the housing in the valve timing control apparatus. 
     SUMMARY 
     The present disclosure is made in view of the above points. According to the present disclosure, there is provided a valve timing control apparatus that controls opening timing and closing timing of one of an intake valve and an exhaust valve of an internal combustion engine, which is opened and closed by a driven-side shaft of the internal combustion engine, through changing of a rotational phase between a driving-side shaft of the internal combustion engine and the driven-side shaft. The valve timing control apparatus includes a housing, a vane rotor, a hydraulic pressure control valve, a solenoid, a first tubular portion and a second tubular portion. The housing is rotatable integrally with the driving-side shaft. The vane rotor is rotatable relative to the housing according to a hydraulic pressure of an advancing chamber formed in the housing and a hydraulic pressure of a retarding chamber formed in the housing. The vane rotor is fixed to the driven-side shaft. The hydraulic pressure control valve includes a sleeve and a spool. The sleeve is received in a center hole of the vane rotor, which extends in a direction of a rotational axis of the vane rotor. The spool is received in an inside of the sleeve and is configured to reciprocate along the sleeve. The hydraulic pressure control valve changes a hydraulic pressure, which is supplied to or is discharged from the advancing chamber, and a hydraulic pressure, which is supplied to or is discharged from the retarding chamber, through movement of the spool. The solenoid includes a solenoid main body and a press pin. The solenoid main body is opposed to the housing. The press pin projects from the solenoid main body and is configured to press the spool of the hydraulic pressure control valve. The solenoid controls the changing of the hydraulic pressures at the hydraulic pressure control valve. The first tubular portion extends from the housing toward the solenoid. The second tubular portion extends from the solenoid main body or an installation member, to which the solenoid main body is installed, toward the housing and is fitted to the first tubular portion. The second tubular portion cooperates with the first tubular portion to form an oil accumulation chamber that is configured to accumulate at least one of oil outputted from a gap between the housing and the vane rotor, and oil discharged from an oil passage communicated with the advancing chamber or the retarding chamber. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
         FIG. 1  is a longitudinal cross sectional view of a valve timing control apparatus according to a first embodiment of the present disclosure; 
         FIG. 2  is a cross-sectional view taken along line II-II in  FIG. 1 ; 
         FIG. 3  is a schematic view showing a structure of a drive force transmission mechanism, in which the valve timing control apparatus of the first embodiment is used; 
         FIG. 4  is a partial enlarged cross-sectional view of a portion of  FIG. 1 ; 
         FIG. 5  is a longitudinal cross sectional view of a valve timing control apparatus according to a second embodiment of the present disclosure; 
         FIG. 6  is a longitudinal cross sectional view of a valve timing control apparatus according to a third embodiment of the present disclosure; 
         FIG. 7  is a longitudinal cross sectional view of a valve timing control apparatus according to a fourth embodiment of the present disclosure; 
         FIG. 8  is a cross sectional view taken along line VIII-VIII in  FIG. 7 ; and 
         FIG. 9  is an enlarged partial cross-sectional view of a main feature shown in 
         FIG. 7 . 
     
    
    
     DETAILED DESCRIPTION 
     Various embodiments of the present disclosure will be described with reference to the accompanying drawings. 
     First Embodiment 
       FIGS. 1 to 4  show a first embodiment of the present disclosure. A valve timing control apparatus  1  of the present embodiment is used in a drive force transmission mechanism of an internal combustion engine  2  of a vehicle (e.g., an automobile) shown in  FIG. 3 . The drive force transmission mechanism is placed in an inside of an engine cover  3 . In the drive force transmission mechanism, a drive belt  17  is would around a pulley  12 , a pulley  15  and a pulley  16 . The pulley  12  is fixed to a crankshaft  11 , which serves as a driving-side shaft of the engine  2 . The pulley  15  is fixed to a camshaft  13 , which serves as a driven-side shaft, and the pulley  16  is fixed to a camshaft  14 , which serves as a driven-side shaft. A torque of the crankshaft  11  is transmitted to the camshafts  13 ,  14  through the drive belt  17 . The camshaft  13  drives intake valves  18  to open and close the intake valves  18 . The camshaft  14  drives exhaust valves  19  to open and close the exhaust valves  19 . In the valve timing control apparatus  1  of the first embodiment, the pulley  15  is connected to the drive belt  17 , and a vane rotor  30  is connected to the camshaft  13 . The crankshaft  11  and the camshaft  13  are rotated such that a predetermined phase difference is formed between the crankshaft  11  and the camshaft  13 , and thereby the opening timing and the closing timing of the intake valves  18  are controlled. 
     An arrow shown in  FIG. 3  indicates a rotational direction of the drive belt  17 . 
     As shown in  FIGS. 1 and 2 , the valve timing control apparatus  1  includes a housing  20 , the vane rotor  30 , a hydraulic pressure control valve  40  and a solenoid  50 . 
     The housing  20  includes a front plate  21 , a rear plate  22 , a tubular portion  23  and shoes  24 - 26 . The front plate  21 , the rear plate  22  and the tubular portion  23  are held together by bolts  27 . 
     The front plate  21  is configured into an annular form (a ring form). A first tubular portion  91 , which is configured into a cylindrical tubular form, axially extends from a radially inner end of the front plate  21  on an axial side where the solenoid  50  is located. The front plate  21  is formed integrally with the first tubular portion  91 . 
     The rear plate  22  is configured into an annular form and is axially opposed to the front plate  21  such that the vane rotor  30  is axially held between the rear plate  22  and the front plate  21 . The rear plate  22  has a rear hole  28 , into which a rear bushing  38  of the vane rotor  30  is received. 
     The tubular portion  23  and the shoes  24 - 26  are integrally formed and are held between the front plate  21  and the rear plate  22  in the axial direction. The shoes  24 - 26  are arranged one after another at predetermined intervals in a circumferential direction of the tubular portion  23  and extend radially inward from the tubular portion  23 . A hydraulic pressure chamber  35 , which has a fan-shaped cross-section, is formed between each circumferentially adjacent two of the shoes  24 - 26 . 
     The drive belt  17  is wound around the pulley  15 , which is formed in the outer peripheral part of the tubular portion  23 , so that the housing  20  is rotated integrally with the crankshaft  11 . 
     The vane rotor  30  is rotatable relative to the housing  20 . The vane rotor  30  includes a rotor (also referred to as a boss)  31 , a rear bushing  38  and a plurality of vanes  32 - 34 . The rotor  31  is configured into a cylindrical tubular form. The rear bushing  38  axially extends from the rotor  31 . The vanes  32 - 34  radially outwardly extend from the rotor  31 . 
     Each outer peripheral wall portion of the rotor  31 , which is circumferentially placed between corresponding adjacent two of the vanes  32 - 34 , is fluid-tightly slidable along an inner peripheral wall portion of a corresponding one of the shoes  24 - 26  of the housing  20 . The rotor  31  has a center hole  36 , which extends in a direction of a rotational axis of the rotor  31  at a center of the rotor  31 . The center hole  36  axially receives a hydraulic pressure control valve  40 . 
     The rear bushing  38  is configured into a tubular form and extends from the rotor  31  into the rear hole  28  of the rear plate  22 . The rear bushing  38  and the camshaft  13  are fluid-tightly fixed with each other. The rear bushing  38  is rotatable relative to the rear hole  28  of the rear plate  22 . 
     Each of the vanes  32 - 34  partitions a corresponding one of the hydraulic pressure chambers  35  of the housing  20  into an advancing chamber  60 - 62  and a retarding chamber  63 - 65 . The hydraulic pressure is supplied to or is discharged from the advancing chambers  60 - 62  through advancing oil passages  70 - 72 . Also, the hydraulic pressure is supplied to or is discharged from the retarding chambers  63 - 65  through retarding oil passages  73 - 75 . 
     A seal member  39  is installed to an outer peripheral wall portion of each of the vanes  32 - 34 . The seal member  39  limits the flow of the oil between the corresponding advancing chamber  60 - 62  and the corresponding retarding chamber  63 - 65 , which are located on one circumferential side and the other circumferential side, respectively, of the vane  32 - 34  having the seal member  39 . The vane rotor  30  is rotatable relative to the housing  20  according to the hydraulic pressure of the advancing chambers  60 - 62  and the hydraulic pressure of the retarding chambers  63 - 65 . 
     A counterclockwise arrow and a clockwise arrow shown in  FIG. 2  indicate the advancing direction and the retarding direction, respectively, of the vane rotor  30  relative to the housing  20 . 
     A stopper piston  80  is received in a hole of the vane rotor  30  in a manner that enables axial reciprocation of the stopper piston  80 . A ring  82  is received in a recess  81  of the rear plate  22 , and the stopper piston  80  can be fitted into or removed from the ring  82  upon the reciprocation of the stopper piston  80 . The stopper piston  80  can be fitted into the ring  82  by an urging force of a spring  83  when the vane rotor  30  is placed in a most retarded position relative to the housing  20 . 
     A first pressure chamber  84  and a second pressure chamber  85  are formed around the stopper piston  80 . One of the first pressure chamber  84  and the second pressure chamber  85  is communicated with the retarding chambers  63 - 65 , and the other one of the first pressure chamber  84  and the second pressure chamber  85  is communicated with the advancing chambers  60 - 62 . 
     When a sum of the hydraulic pressure of the first pressure chamber  84  applied to the stopper piston  80  and the hydraulic pressure of the second pressure chamber  85  applied to the stopper piston  80  becomes larger than the urging force of the spring  83 , the stopper piston  80  is removed from the ring  82 . 
     The hydraulic pressure control valve  40  includes a sleeve  41  and a spool  42 . The sleeve  41  is configured into a tubular bolt form. The spool  42  is received in the sleeve  41 . 
     The sleeve  41  extends through the center hole  36  of the vane rotor  30  and is threadably engaged with a female-thread of the camshaft  13 , and a head  43  of the sleeve  41  contacts the vane rotor  30 . In this way, the camshaft  13 , the vane rotor  30  and the sleeve  41  are fixed together. 
     As shown in  FIGS. 1 and 4 , the sleeve  41  has a first port  401 , a second port  402  and a third port  403 , which radially extend through an outer peripheral wall of the sleeve  41  and are axially arranged one after another in this order from the head  43  side of the sleeve  41 . Furthermore, the sleeve  41  has a slide chamber  44  and an axial passage  45 . The slide chamber  44  axially receives the spool  42 . The axial passage  45  communicates between the slide chamber  44  and an oil discharge passage (also referred to as a first oil discharge passage)  131  of the camshaft  13 . 
     The first port  401  is communicated with the advancing oil passages  70 - 72  of the vane rotor  30 . 
     The second port  402  is communicated with a supply passage  133  of the vane rotor  30 . The supply passage  133  of the vane rotor  30  is communicated with a hydraulic pressure supply passage  130  of the camshaft  13 . Thereby, the oil, which is pumped by an oil pump  5  from an oil pan  4  of the vehicle, is supplied to the second port  402  through the supply passage  133  of the vane rotor  30  and the hydraulic pressure supply passage  130  of the camshaft  13 . 
     The third port  403  is communicated with the retarding oil passages  73 - 75  of the vane rotor  30 . 
     The spool  42  is received in the slide chamber  44  of the sleeve  41  in a manner that enables reciprocation of the spool  42  in the axial direction. A stopper ring  431 , which is installed to the head  43  of the sleeve  41 , limits removal of the spool  42  from the slide chamber  44  of the sleeve  41 . 
     A spring  46  is placed between the spool  42  and an inner wall of the slide chamber  44  of the sleeve  41 . The spring  46  urges the spool  42  toward the stopper ring  431 . 
     The spool  42  has an inside passage  47 , which is formed in the inside of the spool  42 . The inside passage  47  is communicated with the slide chamber  44  of the sleeve  41 . 
     The spool  42  has a front groove and hole portion  421 , a middle groove portion  422  and a rear groove and hole portion  423 , which are formed in the outer peripheral wall of the spool  42  and are arranged in this order from the front side to the rear side in the axial direction. 
     A first land  424  is formed between the front groove and hole portion  421  and the middle groove portion  422  in the outer peripheral wall of the spool  42 . A second land  425  is formed between the middle groove portion  422  and the rear groove and hole portion  423  in the outer peripheral wall of the spool  42 . 
     The first land  424  enables and disables communication between the first port  401  and the front groove and hole portion  421 . The first land  424  also enables and disables communication between the first port  401  and the middle groove portion  422 . 
     The second land  425  enables and disables communication between the third port  403  and the middle groove portion  422 . The second land  425  also enables and disables communication between the third port  403  and the rear groove and hole portion  423 . 
     The front groove and hole portion  421  is communicated with an oil accumulation chamber (also referred to as an oil well or an oil pool)  90  and the inside passage  47 . In this way, the oil accumulation chamber  90  is communicated with the oil discharge passage  131  of the camshaft  13  through the front groove and hole portion  421 , the inside passage  47 , the slide chamber  44  and the axial passage  45 . 
     The front groove and hole portion  421 , the inside passage  47 , the slide chamber  44  and the axial passage  45  form a communication passage  100  that communicates between the oil accumulation chamber  90  and the oil discharge passage  131 . 
     The middle groove portion  422  communicates between the first port  401  and the second port  402  or communicates between the second port  402  and the third port  403 . 
     The rear groove and hole portion  423  is communicated with the inside passage  47 . 
     The solenoid  50  is installed to an installation hole  6  of the engine cover  3  with bolts  7 . The engine cover  3  serves as an installation member, to which a solenoid main body  51  of the solenoid  50  is installed. Besides the solenoid main body  51 , the solenoid  50  further includes a press pin  52 . The press pin  52  projects from the solenoid main body  51 . A small gap  10  is formed between the solenoid main body  51  and an inner peripheral wall  6   a  of the installation hole  6 . This gap  10  is used to coaxially align the solenoid  50  and the housing  20  with each other, i.e., to enable adjustment of the alignment between a rotational axis Oa of the housing  20  and a central axis Ob of the press pin  52 . 
     The solenoid main body  51  is operated through energization from an undepicted electronic control unit (ECU) to axially drive the press pin  52 . The press pin  52  can press the spool  42  toward the spring  46 . 
     When the spool  42  is moved, the hydraulic pressure, which is supplied to the advancing chambers  60 - 62  and the hydraulic pressure, which is supplied to the retarding chambers  63 - 65 , are controlled. The ECU drives the solenoid  50  to coincide the rotational phase of the vane rotor  30  relative to the housing  20  with a target rotational phase. 
     A second tubular portion  92 , which is configured into a cylindrical tubular form, extends from the solenoid main body  51  toward the housing  20 . The solenoid main body  51  and the second tubular portion  92  are integrally formed. 
     The second tubular portion  92  is fitted to an outer peripheral wall section (also referred to as a radially outer side section) of the first tubular portion  91 . Thereby, the oil accumulation chamber  90  is formed in the inside of the first tubular portion  91  and the second tubular portion  92 . The oil accumulation chamber  90  accumulates, i.e., stores the oil, which is discharged from a gap(s), such as a gap  110 , formed between the housing  20  and the vane rotor  30 , and/or the oil, which is discharged from the advancing oil passages  70 - 72  or the retarding oil passages  73 - 75 . 
     The first tubular portion  91  includes a first guiding part  93 , which is configured into a cylindrical tubular form. An outer peripheral wall section (also referred to as a radially outer side section)  93   a  of the first guiding part  93 , which is formed as a part of the outer peripheral wall of the first tubular portion  91 , slidably contacts the second tubular portion  92 . The second tubular portion  92  includes a second guiding part  94 , which is configured into a cylindrical tubular form. An inner peripheral wall section (also referred to as a radially inner side section)  94   b  of the second guiding part  94 , which is formed as a part of the inner peripheral wall of the second tubular portion  92 , slidably contacts the first tubular portion  91 , more specifically, the outer peripheral wall section  93   a  of the first guiding part  93 . When the first guiding part  93  and the second guiding part  94  slidably contact with each other, the rotational axis Oa of the housing  20  and the central axial Ob of the press pin  52  of the solenoid  50  are substantially placed along a common axis (a central axis) O to coaxially align the housing  20  and the solenoid  50  with each other. In this way, the press pin  52  of the solenoid  50  can reliably press the spool  42 , which is placed along the rotational axis Oa of the housing  20 . 
     The second tubular portion  92  includes a stepped part  95 , which has an inner diameter that is larger than an inner diameter of the second guiding part  94 . A seal member  96  is made of, for example, a resin material or a rubber material and is configured into an annular form (a ring form). The seal member  96  is fixed to the stepped part  95  of the second tubular portion  92  by, for example, press-fitting. The seal member  96  has a seal surface  97 , which fluid-tightly and slidably contacts the outer peripheral wall of the first tubular portion  91 . The seal member  96  includes a spring  98 , which is configured into an annular form and is placed in the inside of the seal member  96 . The spring  98  urges the seal surface  97  of the seal member  96  in a radially inner direction to improve the fluid-tightness between the seal surface  97  and the outer peripheral wall section of the first tubular portion  91 . 
     Next, the operation of the valve timing control apparatus  1  will be described. 
     (Engine Start Time) 
     As shown in  FIGS. 1 and 2 , in a state where the engine  2  is stopped, the stopper piston  80  is receive in the inside of the ring  82 , and the vane rotor  30  is held in the most retarded position relative to the housing  20 . In a state immediately after starting of the engine  2 , the sufficient amount of oil is not supplied to the retarding chambers  63 - 65 , the advancing chambers  60 - 62 , the first pressure chamber  84  and the second pressure chamber  85  (these chambers also being referred to as hydraulic chambers), so that the stopper piston  80  is maintained in the received state, in which the stopper piston  80  is received in the inside of the ring  82 . Therefore, it is possible to limit generation of a hitting sound (hammering sound), which would be generated between the housing  20  and the vane rotor  30  due to a torque change applied to the camshaft  13 . 
     (After Engine Start) 
     After the start of the engine  2 , when the sufficient amount of oil is supplied to each hydraulic chamber from the oil pump  5 , the stopper piston  80  is removed from the ring  82  against the urging force of the spring  83  by the hydraulic pressure of the first pressure chamber  84  and the hydraulic pressure of the second pressure chamber  85 . Thereby, the rotation of the vane rotor  30  relative to the housing  20  is enabled. 
     (Time of Advancing Operation) 
     In the advancing operation of the valve timing control apparatus  1 , the solenoid  50  receives a corresponding command from the ECU and removes (or releases) the press force of the press pin  52 , which presses the spool  42  of the hydraulic pressure control valve  40  toward the spring  46 . In this way, the oil is supplied from the hydraulic pressure supply passage  130  to the advancing chambers  60 - 62  through the second port  402 , the first port  401  and the advancing oil passages  70 - 72 . In contrast, the oil of the retarding chambers  63 - 65  is discharged to the inside passage  47  through the retarding oil passages  73 - 75 , the third port  403 , and the rear groove and hole portion  423 . In this way, the hydraulic pressure of the advancing chambers  60 - 62  is applied to the vanes  32 - 34 , and thereby the vane rotor  30  is rotated relative to the housing  20  in the advancing direction. 
     (Time of Retarding Operation) 
     In the retarding operation of the valve timing control apparatus  1 , the solenoid  50  receives a corresponding command from the ECU and drives the press pin  52  to press the spool  42  of the hydraulic pressure control valve  40  toward the spring  46 . In this way, the oil is supplied from the hydraulic pressure supply passage  130  to the retarding chambers  63 - 65  through the second port  402 , the third port  403  and the retarding oil passages  73 - 75 . In contrast, the oil of the advancing chambers  60 - 62  is discharged to the inside passage  47  or the oil accumulation chamber  90  through the advancing oil passages  70 - 72 , the first port  401  and the front groove and hole portion  421 . In this way, the hydraulic pressure of the retarding chambers  63 - 65  is applied to the vanes  32 - 34 , and thereby the vane rotor  30  is rotated relative to the housing  20  in the retarding direction. 
     (Intermediate Holding Operation) 
     When the vane rotor  30  reaches the target phase, the hydraulic pressure control valve  40  limits the discharge of the hydraulic pressure from the retarding chambers  63 - 65  and the advancing chambers  60 - 62  to the oil pan  4 . At this time, the minute amount of hydraulic pressure is supplied from the hydraulic pressure supply passage  130  to the retarding chambers  63 - 65  and the advancing chambers  60 - 62  through the retarding oil passages  73 - 75  and the advancing oil passages  70 - 72 . Thereby, the vane rotor  30  is held in the target phase. 
     (Time of Engine Stop) 
     When a command, which stops the engine  2 , is outputted during the operating period of the valve timing control apparatus  1 , the vane rotor  30  is rotated relative to the housing  20  in the retarding direction through the operation, which is similar to the retarding operation discussed above, and the vane rotor  30  is stopped in the most retarded position. In this state, when the operation of the oil pump  5  is stopped to cause a reduction in the pressure of the first pressure chamber  84  and a reduction in the pressure of the second pressure chamber  85 , the stopper piston  80  is urged into the inside of the ring  82  by the urging force of the spring  83 . In this state, the engine  2  is stopped. 
     Now, the advantages of the first embodiment will be described. 
     (1) In the first embodiment, the first tubular portion  91 , which extends from the housing  20 , and the second tubular portion  92 , which extends from the solenoid main body  51 , are fitted together to form the oil accumulation chamber  90 . In this way, a portion of the oil, which is discharged from the gap(s) between the housing  20  and the vane rotor  30 , or the oil, which is discharge from the advancing oil passages  70 - 72  or the retarding oil passages  73 - 75 , is accumulated in the oil accumulation chamber  90 . Thereby, the leakage of the oil to the outside of the housing  20  can be limited in the valve timing control apparatus  1 . Thus, it is possible to use the drive belt (e.g., a toothed belt, a flat belt or a V-belt) in the drive force transmission mechanism between the housing  20  and the driving-side shaft (i.e., the crankshaft  11 ) in the valve timing control apparatus  1 . 
     (2) In the first embodiment, the first guiding part  93  of the first tubular portion  91  and the second guiding part  94  of the second tubular portion  92  slidably contact with each other, so that the rotational axis Oa of the housing  20  and the central axis Ob of the press pin  52  of the solenoid  50  are substantially coaxially aligned along the common axis O. In this way, the press pin  52  can reliably contact the center (the central axis) of the spool  42 , so that the hydraulic pressure control valve  40  can be reliably controlled by the solenoid  50 . 
     (3) In the first embodiment, the seal member  96  is placed between the first tubular portion  91  and the second tubular portion  92 . The first tubular portion  91  and the second tubular portion  92  are substantially coaxially arranged through the slide contact between the first guiding part  93  of the first tubular portion  91  and the second guiding part  94  of the second tubular portion  92 . In this way, the plate thickness (the radial thickness) of the seal member  96  becomes generally uniform along the entire circumferential extent of the seal member  96 , so that the leakage of the oil from the oil accumulation chamber  90  can be reliably limited. 
     (4) In the first embodiment, the oil discharge passage  131  of the camshaft  13  and the oil accumulation chamber  90  are communicated with each other through the front groove and hole portion  421 , the inside passage  47 , the slide chamber  44  and the axial passage  45  of the hydraulic pressure control valve  40 . In this way, the oil, which is accumulated in the oil accumulation chamber  90 , can be discharged to the oil discharge passage  131  of the camshaft  13 . Thus, the leakage of the oil from the oil accumulation chamber  90  can be reliable limited by limiting the pressure increase of the oil accumulation chamber  90 . 
     (5) In the first embodiment, the gap  10 , which enables the coaxial alignment, is provided between the solenoid main body  51  and the inner peripheral wall  6   a  of the installation hole  6  of the engine cover  3 , to which the solenoid main body  51  is installed. In this way, the housing  20  and the solenoid  50  can be reliably coaxially aligned with each other through the fitting between the first tubular portion  91  and the second tubular portion  92 . 
     Second Embodiment 
       FIG. 5  shows a second embodiment of the present disclosure. In the following embodiments, the components, which are similar to those of the first embodiment, will be indicated by the same reference numerals and will not be described again for the sake of simplicity. 
     In the second embodiment, the first tubular portion  91 , which extends from the housing  20 , is fitted to the outer peripheral wall (the radially outer side section) of the second tubular portion  92 , which extends from the solenoid main body  51 . Specifically, an inner peripheral wall section (also referred to as a radially inner side section)  93   b  of the first guiding part  93 , which is formed as a part of the inner peripheral wall of the first tubular portion  91 , slidably contacts an outer peripheral wall section (also referred to as a radially outer side section)  94   b  of the second guiding part  94 , which is formed as a part of the outer peripheral wall of the second tubular portion  92 . Thereby, the housing  20  is substantially coaxially aligned with the solenoid  50 . 
     The second tubular portion  92  includes the stepped part  95 , which has the inner diameter that is smaller than the inner diameter of the second guiding part  94 . The seal member  96  is fixed to the inner peripheral wall of the first tubular portion  91 , which is opposed to the stepped part  95 , by, for example, press-fitting. The seal surface  97  of the seal member  96  fluid-tightly and slidably contacts the stepped part  95  of the second tubular portion  92 . In this way, the leakage of the oil from the oil accumulation chamber  90  is limited. 
     According to the second embodiment, the advantages, which are similar to those of the first embodiment, are achieved. 
     Third Embodiment 
       FIG. 6  shows a third embodiment of the present disclosure, which is a modification of the first embodiment. In the third embodiment, the second tubular portion  92  is formed separately from the solenoid main body  51  and is installed to the engine cover  3 . The inner peripheral wall of the second tubular portion  92  contacts a cylindrical tubular portion  53  of the solenoid main body  51 . The cylindrical tubular portion  53  and the press pin  52  are substantially coaxial with each other. Thereby, the second tubular portion  92  and the solenoid  50  are substantially coaxially installed. 
     The housing  20  and the second tubular portion  92  are held substantially coaxial with each other through the slide contact between the first guiding part  93  of the first tubular portion  91  and the second guiding part  94  of the second tubular portion  92 . Since the second tubular portion  92  and the solenoid  50  are substantially coaxial with each other, the housing  20  and the solenoid  50  are substantially coaxial with each other. In this way, the press pin  52  of the solenoid  50  can reliably press the spool  42  of the hydraulic pressure control valve  40 , which is placed along the rotational axis Oa of the housing  20 . 
     According to the third embodiment, the advantages, which are similar to those of the first and second embodiments, are achieved. 
     Fourth Embodiment 
       FIGS. 7 to 9  show a fourth embodiment of the present disclosure. The valve timing control apparatus of the fourth embodiment adjusts the opening timing and closing timing of the exhaust valves  19 . 
     In the housing  20 , a seal member  29  is held between the front plate  21 , which is located on the front side of the seal member  29 , and the tubular portion  23  and the shoes  24 ,  26 , which are located on the rear side of the seal member  29 . Furthermore, a seal member  291  is held between the rear plate  22 , which is located on the rear side of the seal member  291 , and the tubular portion  23  and the shoes  24 - 26 , which are located on the front side of the seal member  291 . In this way, leakage of the oil to the outside of the housing  20  can be limited. 
     The rear plate  22  includes an annular portion  221  and a cylindrical tubular portion  222 . The annular portion  221  is configured into an annular form (a ring form). The cylindrical tubular portion  222  axially extends from a radially inner part (an inner peripheral edge) of the annular portion  221  toward an engine head  8 . 
     The cylindrical tubular portion  222  is fitted into a recess  9  of the engine head  8 . The cylindrical tubular portion  222  is installed to the engine head  8  in a rotatable manner. 
     A seal member  99  is installed between an outer peripheral wall of the cylindrical tubular portion  222  of the rear plate  22  and an inner peripheral wall of the recess  9  of the engine head  8 . The seal member  99  limits leakage of the oil thought the gap(s) between the cylindrical tubular portion  222  of the rear plate  22  and the engine head  8 . 
     The vane rotor  30  includes a second communication passage  37 , which extends through the vane rotor  30  in the direction of the rotational axis. One end of the second communication passage  37  of the vane rotor  30  opens to an inside of the first tubular portion  91 , and the other end of the second communication passage  37  opens to an inside of the cylindrical tubular portion  222  of the rear plate  22 . The space in the inside of the cylindrical tubular portion  222  of the rear plate  22  is communicated with a second oil discharge passage  132  of the engine head  8 . Therefore, the oil accumulation chamber  90  is communicated with the second oil discharge passage  132  of the engine head  8  through the second communication passage  37  of the vane rotor  30  and the space in the inside of the cylindrical tubular portion  222  of the rear plate  22 . 
     An annular member  48  is installed between the head  43  of the sleeve  41  and the vane rotor  30 . A return spring  49  is installed at an outside of the head  43  of the sleeve  41 . One end portion of the return spring  49  is engaged with a groove  481  of the annular member  48 , and the other end portion of the return spring  49  is engaged with a groove  911  formed in the inner peripheral wall of the first tubular portion  91 . The return spring  49  urges the vane rotor  30  in the advancing direction. 
     The spool  42  has a front groove and hole portion  421 , a middle groove portion  422  and a rear groove and hole portion  423 , which are formed in the outer peripheral wall of the spool  42  and are arranged in this order from the front side to the rear side in the axial direction. 
     The front groove and hole portion  421  is communicated with the inside passage  47  and is not opened to the oil accumulation chamber  90 . 
     The middle groove portion  422  and the rear groove and hole portion  423  are similar to the middle groove portion  422  and the rear groove and hole portion  423  of the first to third embodiments. 
     The second tubular portion  92 , which extends from the solenoid main body  51  toward the housing  20 , is fitted to the first tubular portion  91  to form the oil accumulation chamber  90 , and this oil accumulation chamber  90  accumulates the oil, which is leaked from the gap(s) between the housing  20  and the vane rotor  30 . In the fourth embodiment, the oil is not directly discharged from the advancing oil passages  70 - 72  or the retarding oil passages  73 - 75  into the oil accumulation chamber  90 . 
     Next, the operation of the valve timing control apparatus of the fourth embodiment will be described. 
     (Engine Start Time) 
     As shown in  FIGS. 7 and 8 , in the state where the engine  2  is stopped, the stopper piston  80  is receive in the inside of the ring  82 , and the vane rotor  30  is held in the most retarded position relative to the housing  20 . 
     (After Engine Start) 
     After the start of the engine  2 , when the sufficient amount of oil is supplied to each corresponding hydraulic chamber from the oil pump  5 , the stopper piston  80  is removed from the ring  82 . Thereby, the rotation of the vane rotor  30  relative to the housing  20  is enabled. 
     (Time of Retarding Operation) 
     In the retarding operation of the valve timing control apparatus, the solenoid  50  receives the corresponding command from the ECU and drives the press pin  52  to press the spool  42  of the hydraulic pressure control valve  40  toward the spring  46 . In this way, the oil is supplied from the hydraulic pressure supply passage  130  to the retarding chambers  63 - 65  through the second port  402 , the third port  403  and the retarding oil passages  73 - 75 . In contrast, the oil of the advancing chambers  60 - 62  is discharged to the inside passage  47  through the advancing oil passages  70 - 72 , the first port  401  and the front groove and hole portion  421 . In this way, the hydraulic pressure of the retarding chambers  63 - 65  is applied to the vanes  32 - 34 , and thereby the vane rotor  30  is rotated relative to the housing  20  in the retarding direction. 
     (Time of Advancing Operation) 
     In the advancing operation of the valve timing control apparatus, the solenoid  50  receives the corresponding command from the ECU and removes the press force, which drives the press pin  52 , so that the press force of the press pin  52 , which presses the spool  42  of the hydraulic pressure control valve  40  toward the spring  46 , is removed. In this way, the oil is supplied from the hydraulic pressure supply passage  130  to the advancing chambers  60 - 62  through the second port  402 , the first port  401  and the advancing oil passages  70 - 72 . In contrast, the oil of the retarding chambers  63 - 65  is discharged to the inside passage  47  through the retarding oil passages  73 - 75 , the third port  403 , and the rear groove and hole portion  423 . In this way, the hydraulic pressure of the advancing chambers  60 - 62  is applied to the vanes  32 - 34 , and thereby the vane rotor  30  is rotated relative to the housing  20  in the advancing direction. 
     (Time of Engine Stop) 
     When the command, which stops the engine  2 , is outputted during the operating period of the valve timing control apparatus, the vane rotor  30  is rotated relative to the housing  20  in the retarding direction through the operation, which is similar to the retarding operation discussed above, and the vane rotor  30  is stopped in the most retarded position. In this state, when the operation of the oil pump  5  is stopped to cause a reduction in the pressure of the first pressure chamber  84  and a reduction in the pressure of the second pressure chamber  85 , the stopper piston  80  is urged into the inside of the ring  82  by the urging force of the spring  83 . In this state, the engine  2  is stopped. 
     Now, the advantages of the fourth embodiment will be described. 
     (1) In the fourth embodiment, the vane rotor  30  has the second communication passage  37  that communicates between the second oil discharge passage  132 , which is formed in the engine head  8 , and the oil accumulation chamber  90 . Thereby, the oil, which is accumulated in the oil accumulation chamber  90 , can be outputted to the second oil discharge passage  132  of the engine head  8  through the second communication passage  37 . Thus, the leakage of the oil from the oil accumulation chamber  90  can be reliable limited. 
     (2) In the fourth embodiment, the oil, which is discharged from the advancing oil passages  70 - 72  or the retarding oil passages  73 - 75 , flows from the first port  401  or the third port  403  of the sleeve  41  to the oil discharge passage  131  of the camshaft  13  through the inside passage  47  in the spool  42  without passing through the oil accumulation chamber  90 . 
     In this way, the hydraulic pressure, which is applied from the oil accumulation chamber  90  to the vane rotor  30 , is reduced, and thereby the frictional force between the vane rotor  30  and the housing  20  is reduced. 
     Furthermore, since the oil pressure, which is applied from the oil accumulation chamber  90  to the solenoid  50 , is reduced, the reliability of the solenoid  50  can be improved. 
     Furthermore, the pressure loss of the oil, which flows from the advancing chambers  60 - 62  or the retarding chambers  63 - 65  to the oil discharge passage  131 , is reduced. 
     Thus, the response of the phase control operation of the vane rotor  30  relative to the housing  20  can be improved. 
     Now, modifications of the above embodiments will be described. 
     In the above embodiments, the oil passages, which are communicated with the first port  401  of the hydraulic pressure control valve  40 , are advancing oil passages  70 - 72 . Furthermore, the oil passages, which are communicated with the third port  403  of the hydraulic pressure control valve  40 , are the retarding oil passages  73 - 75 . Alternatively, in a modification of the above embodiments, the oil passages, which are communicated with the first port  401  of the hydraulic pressure control valve  40 , may be retarding oil passages  73 - 75 , and the oil passages, which are communicated with the third port  403  of the hydraulic pressure control valve  40 , may be the advancing oil passages  70 - 72 . 
     The present disclosure is not limited to the above embodiments, and the above embodiments may be further modified according to the principle of the present disclosure. For example, any one or more of the above features of any one of the embodiments may be combined with any one or more of the above features of any other one or more of the above embodiments.