Patent Publication Number: US-8522737-B2

Title: Variable valve timing mechanism with intermediate locking mechanism and fabrication method thereof

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a 371 of PCT/JP2009/057387, filed Apr. 10, 2009; the disclosure of which is incorporated herein in its entirety. 
     FIELD OF THE INVENTION 
     The present invention relates to a variable valve timing mechanism with an intermediate lock mechanism and a method for manufacturing the variable valve timing mechanism. 
     BACKGROUND OF THE INVENTION 
     As is known in the art, a variable valve timing mechanism, which varies the valve timing of engine valves (intake/exhaust valves) by varying the rotational phase of the corresponding camshaft relative to the crankshaft, has been used as a mechanism in an internal combustion engine mounted in a vehicle. The variable valve timing mechanism includes a case that rotates synchronously with the crankshaft, which is the output shaft of the engine, and a vane rotor that has a coaxial axis, is accommodated in the case in a relatively rotatable manner, and rotates synchronously with a camshaft of the engine. Accommodation chambers are formed in the case and accommodate vanes of the vane rotor. Each of the accommodation chambers is divided by a corresponding one of the vanes into an advancing hydraulic pressure chamber and a retarding hydraulic pressure chamber. The advancing hydraulic pressure chambers and the retarding hydraulic pressure chambers are controlled to rotate the vane rotor relative to the case. In this manner, the rotational phase of the camshaft relative to the crankshaft is varied. 
     In many cases, a variable valve timing mechanism having the above-described configuration includes a lock mechanism for locking the rotational phase of the vane rotor at a prescribed phase at the time when the engine is started. The lock mechanism locks the rotational phase of the vane rotor by engaging a lock pin projecting from the vane rotor with a lock hole formed in the case. 
     In some variable valve timing mechanisms, the locked rotational phase of the vane rotor, which is brought about by the lock mechanism, is set to an intermediate lock phase, which is at the middle of the rotational range of the vane rotor.  FIG. 6  shows a front cross section of a variable valve timing mechanism with an intermediate lock mechanism, which locks the rotational phase of a vane rotor at the intermediate lock phase. As shown in the drawing, the variable valve timing mechanism has a vane rotor  51  having three vanes  50  and a housing  53  including three accommodation chambers  52  for accommodating the vanes  50 . The housing  53  is fastened to a cam sprocket  54  and a cover  55  (see  FIG. 7 ), which covers the front side of the housing  53  as viewed in the drawing, in an integrally rotatable manner. The housing  53 , the cam sprocket  54 , and the cover  55  form a case for receiving the vane rotor  51 . 
     With reference to  FIG. 6 , a lock pin  56  for the intermediate lock mechanism is arranged in one of the vanes  50  of the vane rotor  51 . As illustrated in  FIG. 7 , which shows the cross section of the variable valve timing mechanism taken along curve VII-VII of  FIG. 6 , when the vane rotor  51  is in the intermediate lock phase, the phase of the lock pin  56  coincides with the phase of a lock hole  57  formed in the cam sprocket  54 . In this state, as the lock pin  56  projects toward the cam sprocket  54 , the lock pin  56  becomes engaged with the lock hole  57 , thus locking rotation of the vane rotor  51 . 
     However, for the reason described below, it is not easy to reliably lock the relative rotational phase of the vane rotor  51  at the intermediate lock phase. Specifically, in many variable valve timing mechanisms with an intermediate lock mechanism, in order to simplify a hydraulic system, a hydraulic circuit for controlling the phase of the vane rotor  51  and a hydraulic circuit for operating the lock pin  56  are not formed independently from each other. That is, as illustrated in  FIG. 8(   a ), the lock pin  56  is operated when the vane rotor  51  is advanced (the vanes  50  are). In this case, immediately after the phases of the lock pin  56  and the lock hole  57  coincide with each other, the lock pin  56  is pressed against a wall surface of the lock hole  57  at the advancing side, thus causing friction. This may hamper engagement of the lock pin  56  with the lock hole  57 . In other words, the lock pin  56  is allowed to become engaged with the lock hole  57  only at the instant when the phase of the lock pin  56  and the phase of the lock hole  57  coincide with each other. 
     The variable valve timing mechanism with an intermediate lock mechanism has the following problem. Specifically, immediately after the engine is started, the intermediate lock mechanism does not receive hydraulic pressure. Accordingly, if there is space between the lock pin  56  and the lock hole  57 , variation in the cam torque cause the vane rotor  51  to chatter, generating rattling noise. To avoid this, it is necessary to prevent the gap from being formed between the lock pin  56  and the lock hole  57 . However, this requires a significantly high level of machining accuracy. 
     Conventionally, a variable valve timing mechanism with an intermediate lock mechanism including two lock pins, as described in Patent Document 1, has been proposed. As illustrated in  FIG. 9 , the variable valve timing mechanism has a vane rotor  61  having a plurality of (in the drawing, two) vanes  60 , which project from the outer periphery of the vane rotor  61 , and a housing  63  in which a plurality of accommodation chambers  62  are formed (in the drawing, two) to receive the vanes  60 . The housing  63  of the variable valve timing mechanism has two lock pins  64 ,  65 , which are spaced apart by a prescribed phase and capable of projecting toward the vane rotor  61 . A lock groove  66 , with which the two lock pins  64 ,  65  are engageable simultaneously, is formed in the outer periphery of the vane rotor  61 . 
       FIGS. 10(   a ) to  10 ( c ) illustrate the operating steps of the intermediate lock mechanism for the variable valve timing mechanism including the above-described two pins  64 ,  65 . When the vane rotor  61  is rotated clockwise as viewed in the drawings with the lock pins  64 ,  65  disengaged from the lock groove  66 , the lock pin  64  is first received in the lock groove  66  as illustrated in  FIG. 10(   a ). As the vane rotor  61  is rotated counterclockwise continuously from the state of  FIG. 10(   a ), the phase of the lock pin  65  coincides with the counterclockwise end of the lock groove  66  as viewed in the drawings and thus becomes engageable with the lock groove  66 , referring to  FIG. 10(   b ). In this state, the lock pin  64 , which is engaged, is pressed against the clockwise end of the lock groove  66  as viewed in the drawing. However, the lock pin  65 , which is not engaged, is maintained free. This allows the lock pin  65  to be smoothly received in the lock groove  66 , as illustrated in  FIG. 10(   c ). The vane rotor  61  is thus locked from rotating relative to the housing  63 . 
     Since the variable valve timing mechanism includes the two lock pins  64 ,  65 , as has been described, rotation of the vane rotor  51  is easily locked at the intermediate lock phase. However, in order to prevent chattering of the vane rotor  51  from occurring when the vane rotor  51  is locked in a state without hydraulic pressure, the lock groove  66  must be machined with significantly high accuracy, as in the case of the variable valve timing mechanism having the single lock pin  56 .
     Patent Document 1: Japanese Laid-Open Patent Publication No. 2006-170085   

     SUMMARY OF THE INVENTION 
     Accordingly, it is an objective of the present invention to provide a variable valve timing mechanism with an intermediate lock mechanism that ensures reliable locking and easily prevents chattering of a vane rotor when the vane rotor is locked. 
     To achieve the foregoing objective, the present invention provides a variable valve timing mechanism with an intermediate lock mechanism that varies a rotational phase of a camshaft relative to a crankshaft between a most advanced phase and a most retarded phase, and includes a first rotary body, a second rotary body, and an intermediate lock mechanism. The first rotary body rotates synchronously with one of the crankshaft and the camshaft. The second rotary body rotates synchronously with the other one of the crankshaft and the camshaft, has a coaxial axis with the first rotary body, and accommodates the first rotary body in a relatively rotatable manner. The second rotary body is formed by fastening a first member and a second member to each other. The intermediate lock mechanism locks rotation of the first rotary body relative to the second rotary body at an intermediate lock phase between the most advanced phase and the most retarded phase. The intermediate lock mechanism includes a first lock pin and a second lock pin, an advancement restricting grove, and a retardation restricting groove. The first lock pin and a second lock pin are arranged in the first rotary body, and are projectable and retractable independently from each other. The advancement restricting groove is arranged in the first member, and is formed in such a manner as to, when the first lock pin is projected, become engaged with the first lock pin to lock, at the intermediate lock phase, rotation of the first rotary body to an advancing side, and permit, at the intermediate lock phase, rotation of the first rotary body to a retarding side. The retardation restricting groove is arranged in the second member, and is formed in such a manner as to, when the second lock pin is projected, become engaged with the second lock pin to lock, at the intermediate lock phase, rotation of the first rotary body to the retarding side, and permit, at the intermediate lock phase, rotation of the first rotary body to the advancing side. 
     The variable valve timing mechanism with an intermediate lock mechanism, which is configured as described above, varies the rotational phase of the camshaft relative to the crankshaft between the most advanced phase and the most retarded phase through relative rotation between the first and second rotary bodies. Rotation of the first rotary body from the intermediate lock phase to the advancing side is locked through engagement between the first lock pin and the advancement restricting groove. Rotation of the first rotary body from the intermediate lock phase to the retarding side is locked through engagement between the second lock pin and the retardation restricting groove. In this manner, rotation of the first rotary body relative to the second rotary body is locked at the intermediate lock phase. The variable valve timing mechanism with an intermediate lock mechanism thus allows the first and second lock pins to enter the corresponding advancement/retardation restricting grooves in a free state without being pressed from the side. As a result, reliable locking by the intermediate lock mechanism is ensured. 
     Also in the above-described configuration, the advancement restricting groove and the retardation restricting groove are formed in the separate members. In this configuration, with the first lock pin held in contact with the end of the advancement restricting groove at the advancing side and the second lock pin held in contact with the end of the retardation restricting groove at the retarding side, the first member and the second member are fastened to each other. In this manner, even if there is some degree of dimensional tolerance, the lock pins and the corresponding restricting grooves are arranged in such a manner as to prevent chattering between the lock pins and the restricting grooves when locking is performed. As a result, the above-described configuration not only ensures reliable locking, but also easily prevents chattering of a vane rotor when locking is carried out. 
     As needed, ratchet grooves having a comparatively small depth may be each formed continuously from the corresponding one of the advancement restricting groove and the retardation restricting groove in the variable valve timing mechanism with an intermediate lock mechanism. In this case, when locking is not performed, the ratchet grooves and the lock pins function as a ratchet mechanism and thus guide the first rotary body to the intermediate lock phase. 
     The above described variable valve timing mechanism with an intermediate lock mechanism may be configured such that one of the first and second members is a cam sprocket and the other is a cover that is formed to cover a front surface of the cam sprocket. 
     On the other hand, to achieve the foregoing objective, the present invention provides a method for manufacturing a variable valve timing mechanism with an intermediate lock mechanism. The variable valve timing mechanism varies a rotational phase of a camshaft relative to a crankshaft between a most advanced phase and a most retarded phase, and includes a first rotary body, a second rotary body, and an intermediate lock mechanism. The first rotary body rotates synchronously with one of the crankshaft and the camshaft. The second rotary body rotates synchronously with the other one of the crankshaft and the camshaft, has a coaxial axis with the first rotary body, and accommodates the first rotary body in a relatively rotatable manner. The second rotary body is formed by fastening a first member and a second member to each other. The intermediate lock mechanism locks rotation of the first rotary body relative to the second rotary body at an intermediate lock phase between the most advanced phase and the most retarded phase. The method for manufacturing a variable valve timing mechanism with an intermediate lock mechanism includes: assembling a first lock pin and a second lock pin to the first rotary body; forming an advancement restricting groove in the first member, the advancement restricting groove becoming engaged with the first lock pin to lock, at the intermediate lock phase, rotation of the first rotary body to an advancing side and permit, at the intermediate lock phase, rotation of the first rotary body to a retarding side; forming a retardation restricting groove in the second member, the retardation restricting groove becoming engaged with the second lock pin to lock, at the intermediate lock phase, rotation of the first rotary body to the retarding side and permit, at the intermediate lock phase, rotation of the first rotary body to the advancing side; and fastening the first member and the second member to each other with the first lock pin held in contact with an end of the advancement restricting groove at the advancing side and the second lock pin held in contact with an end of the retardation restricting groove at the retarding side. 
     According to the above-described manufacturing method, the first member and the second member are fastened together with the first lock pin held in contact with the end of the advancement restricting groove at the advancing side and the second lock pin held in contact with the end of the retardation restricting groove at the retarding side. In this manner, even if there is some degree of dimensional tolerance, the lock pins and the corresponding restricting grooves are arranged in such a manner as to prevent chattering between the lock pins and the restricting grooves when locking is performed. Further, in the method, rotation of the first rotary body from the intermediate lock phase to the advancing side is locked through engagement between the first lock pin and the advancement restricting groove. Rotation of the first rotary body from the intermediate lock phase to the retarding side is locked through engagement between the second lock pin and the retardation restricting groove. In this manner, rotation of the first rotary body relative to the second rotary body is locked at the intermediate lock phase. The variable valve timing mechanism with an intermediate lock mechanism thus allows the first and second lock pins to enter the corresponding advancement/retardation restricting grooves in a free state without being pressed from the side. As a result, reliable locking by the intermediate lock mechanism is ensured. The above-described manufacturing method thus not only ensures the reliable locking, but also easily prevents chattering of the vane rotor when locking is performed. 
     In the above-describe method, ratchet grooves having a comparatively small depth may be each formed continuously from the corresponding one of the advancement restricting groove and the retardation restricting groove. In this case, when locking is not performed, the ratchet grooves and the lock pins function as a ratchet mechanism and thus guide the first rotary body to the intermediate lock phase. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a front cross-sectional view showing a variable valve timing mechanism with an intermediate lock mechanism according to one embodiment of the present invention; 
         FIG. 2  is a cross-sectional view taken along curve II-II in  FIG. 1 , showing the variable valve timing mechanism with an intermediate lock mechanism; 
         FIGS. 3(   a ),  3 ( b ), and  3 ( c ) are cross-sectional views each illustrating an operating step of the intermediate lock mechanism of the illustrated embodiment; 
         FIGS. 4(   d ),  4 ( e ), and  4 ( f ) are cross-sectional views each illustrating an operating step of the intermediate lock mechanism of the illustrated embodiment; 
         FIGS. 5(   a ),  5 ( b ), and  5 ( c ) are cross-sectional views each illustrating a manufacturing step of the intermediate lock mechanism of the illustrated embodiment; 
         FIG. 6  is a front cross-sectional view showing a conventional example of a variable valve timing mechanism with an intermediate lock mechanism; 
         FIG. 7  is a cross-sectional view taken along curve VII-VII in  FIG. 6 , showing the variable valve timing mechanism with an intermediate lock mechanism; 
         FIGS. 8(   a ) and  8 ( b ) are cross-sectional views each illustrating an operating step of the intermediate lock mechanism of the conventional variable valve timing mechanism with an intermediate lock mechanism; 
         FIG. 9  is a front cross-sectional view showing another conventional example of a variable valve timing mechanism with an intermediate lock mechanism; and 
         FIGS. 10(   a ),  10 ( b ), and  10 ( c ) are cross-sectional views each illustrating an operating step of the intermediate lock mechanism of the conventional variable valve timing mechanism with an intermediate lock mechanism. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     One embodiment of a variable valve timing mechanism with an intermediate lock mechanism and a method for manufacturing the variable valve timing mechanism according to the present invention will now be described in detail with reference to  FIGS. 1 to 5 . 
       FIG. 1  shows a front cross section of the variable valve timing mechanism with an intermediate lock mechanism of the illustrated embodiment. As shown in  FIG. 1 , the variable valve timing mechanism with an intermediate lock mechanism has a vane rotor  2  including a plurality of (in the drawing, three) vanes  1 , which project from the outer periphery of the vane rotor  2 , and a housing  4  in which a plurality of (in the drawing, three) accommodation chambers  3  are formed to accommodate the corresponding vanes  1 . The vane rotor  2 , which serves as a first rotary body, is connected to a camshaft of an internal combustion engine in an integrally rotatable manner. The housing  4  is fastened to a cam sprocket  5 , which is drivably connected to the crankshaft, or the engine output shaft, through a timing chain in a synchronously rotatable manner, and a cover  6  (shown in not  FIG. 1  but  FIG. 2 ) for covering a front surface of the housing  4  by means of a plurality of bolts  7 . In the present embodiment, the housing  4 , the cam sprocket  5 , and the cover  6 , which are fastened together as an integral body, configure a vane rotor accommodating case serving as a second rotary body. 
     Each of the accommodation chambers  3  in the housing  4  is divided into an advancing hydraulic pressure chamber  8  and a retarding hydraulic pressure chamber  9  by a corresponding one of the vanes  1 , which are accommodated in the accommodation chambers  3 . The variable valve timing mechanism with an intermediate lock mechanism controls the hydraulic pressure in the advancing hydraulic pressure chamber  8  and the hydraulic pressure in the retarding hydraulic pressure chamber  9  to rotate the vane rotor  2  relative to the aforementioned case. This varies the rotational phase of the corresponding camshaft relative to the crankshaft and thus the valve timing of the engine valves that are opened or closed by the cam formed in the camshaft. 
     The variable valve timing mechanism has the intermediate lock mechanism for locking rotation of the vane rotor  2  relative to the case (the housing  4 , the cam sprocket  5 , and the cover  6 ) at the intermediate lock phase, which is set between the most advanced phase and the most retarded phase of the vane rotor  2 . The intermediate lock mechanism has two lock pins formed in one of the vanes  1  of the vane rotor  2 , which are a first lock pin  10  and a second lock pin  11 . 
       FIG. 2  shows a cross section taken along curve II-II in  FIG. 1 , showing the variable valve timing mechanism in the vicinity of the first and second lock pins  10 ,  11 . With reference to  FIG. 2 , the first lock pin  10  is capable of projecting toward the cover  6 , and the second lock pin  11  is capable of projecting toward the cam sprocket  5 . The surface of the cover  6  facing the first lock pin  10  has an advancement restricting groove  12 , which becomes engaged with the first lock pin  10  when the first lock pin  10  is projected, thus locking rotation of the vane rotor  2  to the advancing side at the intermediate lock phase and permitting rotation of the vane rotor  2  to the retarding side in the intermediate lock phase. The surface of the cam sprocket  5  facing the second lock pin  11  has a retardation restricting groove  13 , which becomes engaged with the second lock pin  11  when the second lock pin  11  is projected, thus locking rotation of the vane rotor  2  to the retarding side at the intermediate lock phase and permitting rotation of the vane rotor  2  to the advancing side in the intermediate lock phase. 
     When the first lock pin  10  is in the advancement restricting groove  12 , relative rotation of the vane rotor  2  to the advancing side is locked at the intermediate lock position. When the second lock pin  11  is in the retardation restricting groove  13 , relative rotation of the vane rotor  2  to the retarding side is locked at the intermediate lock position. Accordingly, when the first lock pin  10  and the second lock pin  11  are received in the advancement restricting groove  12  and the retardation restricting groove  13 , respectively, the relative rotation of the vane rotor  2  is locked at the intermediate lock phase. In the present embodiment, the cover  6  having the advancement restricting groove  12  corresponds to the first member and the cam sprocket  5  having the retardation restricting groove  13  corresponds to the second member. 
     In the variable valve timing mechanism of the illustrated embodiment, ratchet grooves  14 ,  15 , which are smaller in depth than the advancement restricting groove  12  and the retardation restricting groove  13 , are formed continuously from the corresponding restricting grooves  12 ,  13  at the retardation sides. The ratchet grooves  14 ,  15  function as a ratchet mechanism together with the first and second lock pins  10 ,  11 . In this manner, when the engine is started with operation of the intermediate lock mechanism suspended, the first and second lock pins  10 ,  11  are guided to the advancement restricting groove  12  and the retardation restricting groove  13 . This facilitates operation of the intermediate lock mechanism. 
     Specifically, if engine start is initiated when the first lock pin  10  and the second lock pin  11  are disengaged from the advancement restricting groove  12  and the retardation restricting groove  13 , respectively, and the relative rotation of the vane rotor  2  is not locked at the intermediate lock phase, the variable valve timing mechanism with an intermediate lock mechanism operates in the following manner. That is, when cranking is carried out to initiate the engine start, the camshaft generates alternating torque acting alternately to the advancing side and the retarding side. The alternating torque rotates the vane rotor  2 , the phase of which is unfixed, alternately to the advancing side and the retarding side with respect to the vane rotor accommodating case. When the torque to the advancing side is produced, the vane rotor  2  is rotated to the advancing side, thus causing the first lock pin  10  to enter the ratchet groove  14 . When the torque to the advancing side is generated for a second time, the vane rotor  2  is rotated to the advancing side from the phase in which the first lock pin  10  is received in the ratchet groove  14 . This allows the second lock pin  11  to enter the ratchet groove  15 . When a subsequent advancing torque is generated, the vane rotor  2  is rotated to the advancing side from the phase in which the second lock pin  11  is received in the ratchet groove  15 , thus allowing the first lock pin  10  to be received in the advancement restricting groove  12 . When a subsequent advancing torque is produced, the vane rotor  2  is rotated to the advancing side from the phase in which the first lock pin  11  is received in the advancement restricting groove  12 . The second lock pin  11  is thus received in the retardation restricting groove  13 . As has been described, each time the torque to the advancing side is generated, the vane rotor  2  is rotated closer to the intermediate lock phase in a stepped manner. As a result, the ratchet grooves  14 ,  15  allow the intermediate lock mechanism to operate through autonomous restoration when the intermediate lock mechanism is unlocked. 
     Operation of the intermediate lock mechanism will hereafter be described. Specifically, the following description is focused on a case in which the intermediate lock mechanism is operated as the vane rotor  2  is relatively rotated toward the advancing side from the most retarded phase. 
     As the vane rotor  2  is relatively rotated toward the advancing side from the state in which each vane  1  is at the most retarded phase as illustrated in  FIG. 3(   a ), the first lock pin  10  is received in the ratchet groove  14  in the cover  6 , referring to  FIG. 3(   b ). Then, as illustrated in  FIG. 3(   c ), the second lock pin  11  is received in the ratchet groove  15  in the cam sprocket  5 . 
     Afterwards, as the vane rotor  2  is relatively rotated further toward the advancing side, the first lock pin  10  enters the advancement restricting groove  12 , with reference to  FIG. 4(   d ). Relative rotation of the vane rotor  2  toward the advancing side is continued until the first lock pin  10  reaches the end of the advancement restricting groove  12  at the advancing side. Then, as illustrated in  FIG. 4(   e ), the phase of the second lock pin  11  coincides with the phase of the end of the retardation restricting groove  13  at the retarding side. The second lock pin  11  thus becomes engageable with the retardation restricting groove  13 . In this state, the first lock pin  10  is pressed against the end of the advancement restricting groove  12  at the advancing side, but the second lock pin  11  is held free without being pressed sideways. This allows the second lock pin  11  to be received smoothly in the retardation restricting groove  13 , as illustrated in  FIG. 4(   f ). As a result, the vane rotor  2  is locked at the intermediate lock phase by the intermediate lock mechanism. 
     Next, a method for manufacturing the variable valve timing mechanism with an intermediate lock mechanism will be described. 
     To manufacture the variable valve timing mechanism, the first and second lock pins  10 ,  11  are assembled to the vane rotor  2 . Further, the retardation restricting groove  13  and the advancement restricting groove  12  are formed in the cam sprocket  5  and the cover  6 , respectively. Afterwards, as illustrated in  FIG. 5(   a ), with the vane rotor  2  accommodated, the housing  4 , the cam sprocket  5 , and the cover  6  are assembled temporarily without fastening a bolt  7 . At this stage, even though the first and second lock pins  10 ,  11  are received in the advancement/retardation restricting grooves  12 ,  13 , a clearance is ensured between each pin and the corresponding restricting groove. As a result, the phase of the vane rotor  2  (each vane  1 ) is not fully fixed. 
     Subsequently, as illustrated in  FIG. 5(   b ), the first lock pin  10  is brought into contact with the end of the advancement restricting groove  12  at the advancing side, and the second lock pin  11  is brought into contact with the end of the retardation restricting groove  13  at the retarding side. In this manner, the clearances are canceled with respect to the restricting grooves. Then, in this state, with reference to  FIG. 5(   c ), the bolt  7  is fastened to fix the housing  4 , the cam sprocket  5 , and the cover  6  together as an integral body. 
     The variable valve timing mechanism with an intermediate lock mechanism of the present embodiment has the advantages described below. 
     (1) In the present embodiment, the intermediate lock mechanism of the variable valve timing mechanism includes the first and second lock pins  10 ,  11  and the advancement/retardation restricting grooves  12 ,  13  that are configured as will be described. Specifically, the first and second lock pins  10 ,  11 , which are projectable and retractable independently from each other, are formed in the vane rotor  2 . The cover  6  includes the advancement restricting groove  12 , which becomes engaged with the first lock pin  10  when the first lock pin  10  is projected, thus locking rotation of the vane rotor  2  to the advancing side at the intermediate lock phase and permitting rotation of the vane rotor  1  to the retarding side at the intermediate lock phase. The cam sprocket  5  has the retardation restricting groove  13 , which becomes engaged with the second lock pin  11  when the second lock pin  11  is projected, thus locking rotation of the vane rotor  2  to the retarding side at the intermediate lock phase and permitting rotation of the vane rotor  2  to the advancing side at the intermediate lock phase. In the variable valve timing mechanism with an intermediate lock mechanism configured as described above, the first lock pin  10  is engaged with the advancement restricting groove  12  to lock the rotation of the vane rotor  2  from the intermediate lock phase to the advancing side. Also, the second lock pin  11  is engaged with the retardation restricting groove  13  to lock the rotation of the vane rotor  2  from the intermediate lock phase to the retarding side. As a result, the rotation of the vane rotor  2  relative to the case (the housing  4 , the cam sprocket  5 , and the cover  6 ) is locked at the intermediate lock phase. In this variable valve timing mechanism with an intermediate lock mechanism, the first and second lock pins  10 ,  11  are received in the corresponding advancement/retardation restricting grooves  12 ,  13  each in a free state without being pressed from the side. This ensures reliable locking by the intermediate lock mechanism. Further, in the present embodiment, the advancement restricting groove  12  and the retardation restricting groove  13  are formed in the separate members. In this arrangement, the cam sprocket  5  and the cover  6  are fastened together with the first lock pin  10  held in contact with the end of the advancement restricting groove  12  at the advancing side and the second lock pin  10  held in contact with the end of the retardation restricting groove  13  at the retarding side. In this manner, even if there is a some degree of dimensional tolerance, the lock pins and the relative grooves are arranged without causing chattering between the lock pins and the corresponding restricting grooves at the time when locking is performed. As a result, the above-described configuration not only ensures reliable locking, but also easily prevents chattering of the vane rotor when the vane rotor is locked. 
     (2) According to the manufacturing method of the present embodiment, the variable valve timing mechanism with an intermediate lock mechanism is manufactured through the steps of: 
     assembling the first and second lock pins  10 ,  11  to the vane rotor  2 ; 
     forming, in the cover  6 , the advancement restricting groove  12 , which becomes engaged with the first lock pin  10  to lock rotation of the vane rotor  2  to the advancing side at the intermediate lock phase and permit rotation of the vane rotor  2  to the retarding side at the intermediate lock phase; 
     forming, in the cam sprocket, the retardation restricting groove  13 , which becomes engaged with the second lock pin  11  to lock the rotation of the vane rotor  2  to the retarding side at the intermediate lock phase and permit the rotation of the vane rotor  2  to the advancing side at the intermediate lock phase; and 
     fastening the cover  6  and the cam sprocket  5  to each other with the first lock pin  10  held in contact with the end of the advancement restricting groove  12  at the advancing side and the second lock pin  11  held in contact with the end of the retardation restricting groove  13  at the retarding side. 
     This manufacturing method allows arrangement of the lock pins and the corresponding restricting grooves without causing chattering between the lock pins and the restricting grooves at the time when locking is performed, even if there is some degree of dimensional tolerance. Further, in the manufacturing method, the first lock pin  10  is engaged with the advancement restricting groove  12  to lock the rotation of the vane rotor  2  from the intermediate lock phase to the advancing side. The second lock pin  11  is engaged with the retardation restricting groove  13  to lock the rotation of the vane rotor  2  from the intermediate lock phase to the retarding side. In this manner, rotation of the vane rotor  2  relative to the case (the housing  4 , the cam sprocket  5 , and the cover  6 ) is locked at the intermediate lock phase. The variable valve timing mechanism with an intermediate lock mechanism allows the first and second lock pins  10 ,  11  to enter the corresponding advancement/retardation restricting grooves  12 ,  13  in a free state without being pressed from the side. The intermediate lock mechanism thus ensures reliable locking. This not only ensures the reliable locking, but also easily prevents chattering of the vane rotor when locking is performed. 
     (3) In the present embodiment, the ratchet grooves  14 ,  15 , which are comparatively small in depth, are formed continuously from the corresponding advancement/retardation restricting grooves  12 ,  13  in the variable valve timing mechanism with an intermediate lock mechanism. Accordingly, when locking is not performed, the ratchet grooves  14 ,  15  and the first and second lock pins  10 ,  11  function as a ratchet mechanism and thus guide the vane rotor  2  to the intermediate lock phase. 
     The above-described embodiment may be modified according to the forms described below. 
     In the above-described embodiment, the advancement restricting groove  12  is formed in the cover  6 , and the retardation restricting groove  13  is formed in the cam sprocket  5 . However, the advancement restricting groove  12  may be formed in the cam sprocket  5 , and the retardation restricting groove  13  may be formed in the cover  6 . 
     In the above-described embodiment, the second rotary body is configured by three members, which are the housing  4 , the cam sprocket  5 , and the cover  6 . However, the second rotary body may be configured by two separate members or four or more separate members. Also in these cases, the same advantages as the advantages of the above-described embodiment are ensured as long as the advancement restricting groove  12  and the retardation restricting groove  13  are formed in separate members. 
     In the above-described embodiment, the ratchet grooves  14 ,  15 , which have a comparatively small depth, are formed continuously from the corresponding advancement/retardation restricting grooves  12 ,  13 . However, even without the ratchet grooves  14 ,  15 , reliable locking by the intermediate lock mechanism may be ensured.