Patent Publication Number: US-6662769-B2

Title: Valve timing control device

Description:
This application is based on and claims priority under 35 U.S.C. §119 with respect to a Japanese Patent Application 2001-083373 filed on Mar. 22, 2001, the entire disclosure of which is incorporated herein by reference. 
     FIELD OF THE INVENTION 
     The present invention generally relates to a valve timing control device. More particularly, the present invention pertains to a valve timing control device for controlling the angular phase difference between a crankshaft of a combustion engine and a camshaft of the combustion engine. 
     BACKGROUND OF THE INVENTION 
     A known valve timing control device includes a rotary member which is rotatably arranged in a torque transmitting route between a crankshaft of an internal combustion engine and a camshaft of the engine, a rotational transmitting member which rotates relative to the rotary member, a pressure chamber formed by the rotary member and the rotational transmitting member, a vane provided on the rotary member or the rotational transmitting member to divide the pressure chamber into an advancing chamber and a retarding chamber, and a helical spring having a coil portion. A first end portion of the spring engages the rotary member and a second end portion engages the rotational transmitting member, with the spring urging the rotary member in the advancing direction to expand the advancing chamber. A controlling device supplies and discharges fluid to and from the advancing chamber and the retarding chamber to control phase alterations between the rotary member and the rotational transmitting member. An example of a known variable timing device having a construction similar to that described above is disclosed in Japanese Patent Laid-Open Publication No. Heisei 11(1999)-223112. 
     As a plurality of cams arranged on the camshaft push the valves of the internal combustion engine during engine operation, the rotary member always receives some force. The force rotates the rotational transmitting member in the delayed or retarding direction. The above-described known valve timing control device is provided with the helical spring to rotate the rotary member in the advancing direction so that the helical spring offsets this force. Thus, the response in the advancing direction of the rotary member is improved. 
     However, as shown in FIGS.  17 ( a ) and  17 ( b ), the structure of the helical spring  270  used in the known valve timing control device includes a coil portion  270   a , a first hook portion  270   b  and a second hook portion  270   c . The hook portion  270   b  engages either the rotary member or the rotational transmitting member while the hook portion  270   c  engages the other of the rotary member and the rotational transmitting member. Both of the hook portions  270   b ,  270   c  extend in the axial direction of the coil portion  270   a . Thus, the total length (LB) of the helical spring  270  is relatively long. Therefore, the overall axial length of the known valve timing control device must be rather long. 
     SUMMARY OF THE INVENTION 
     According to one aspect, a valve timing control device includes a rotary member adapted to be rotatably arranged in a torque transmitting route between a crankshaft of an internal combustion engine and a camshaft of the internal combustion engine, a rotational transmitting member rotatable relative to the rotary member, a pressure chamber formed by the rotary member and the rotational transmitting member, a vane provided on the rotary member or the rotational transmitting member dividing the pressure chamber into an advancing chamber and a delaying chamber, and a helical spring which urges the rotary member in the advancing direction to expand the advancing chamber. The helical spring includes a coil portion, a first end portion engaging the rotary member and a second end portion engaging the rotational transmitting member. At least one of the first and second end portions of the helical spring extends on an imagined radial plane arranged in a radial direction of the coil portion. 
     According to another aspect, a valve timing control device includes a rotary member adapted to be rotatably arranged in a torque transmitting route between a crankshaft of an internal combustion engine and a camshaft of the internal combustion engine, a first annular spring space formed in the rotary member and having an inner circumferential wall and an outer circumferential wall, a rotational transmitting member rotatable relative to the rotary member, a second annular spring space formed in the rotational transmitting member and having an inner circumferential wall and an outer circumferential wall, a pressure chamber formed by the rotary member and the rotational transmitting member, a vane provided on the rotary member or the rotational transmitting member dividing the pressure chamber into an advancing chamber and a delaying chamber, and a helical spring positioned in the first and second annular spring spaces to urge the rotary member in the advancing direction to expand the advancing chamber. The helical spring includes a coil portion, a first end portion and a second end portion, with the first end portion engaging a first groove formed in one of the inner circumferential wall of the rotary member and the outer circumferential wall of the rotary member, and the second end portion engaging a second groove formed in one of the inner circumferential wall of the rotational transmitting member and the outer circumferential wall of the rotational transmitting member. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING FIGURES 
     The foregoing and additional features and characteristics of the present invention will become more apparent from the following detailed description considered with reference to the accompanying drawing figures in which like reference numerals designate like elements. 
     FIG.  1 ( a ) is a vertical cross-sectional view of a first embodiment of a valve timing control device in accordance with the prevent invention. 
     FIGS.  1 ( b ) and  1 ( c ) are enlarged cross-sectional views of a part of FIG.  1 ( a ). 
     FIG. 2 is a side view of the helical spring used in the valve timing control device shown in FIG.  1 ( a ). 
     FIG. 3 is an end view of the helical spring shown in FIG.  2 . 
     FIG. 4 is a sectional view of the valve timing control device when the rotary member is in the most retarded or delayed position relative to the rotational transmitting member. 
     FIG. 5 is a sectional view of the of the valve timing control device when the rotary member is in the most advanced position relative to the rotational transmitting member. 
     FIG. 6 is a sectional view of a second embodiment of a valve timing control device when the rotary member is in the most delayed or retarded position relative to the rotational transmitting member. 
     FIG. 7 is a sectional view of the valve timing control device shown in FIG. 6 when the rotary member is in the most advanced position relative to the rotational transmitting member. 
     FIG. 8 is an enlarged end view of the second end portion of the helical spring used in the valve timing control device shown in FIG.  6 . 
     FIG. 9 is an end view of a helical spring used in a third embodiment of the valve timing control device. 
     FIG. 10 is a sectional view of the third embodiment of the valve timing control device when the rotary member is in the most delayed or retarded position relative to the rotational transmitting member. 
     FIG. 11 is a sectional view of the third embodiment of the valve timing control device when the rotary member is in the most advanced position relative to the rotational transmitting member. 
     FIG. 12 is a sectional view of a fourth embodiment of a valve timing control device when the rotary member is in the most delayed or retarded position relative to the rotational transmitting member. 
     FIG. 13 is a sectional view of the fourth embodiment of the valve timing control device when the rotary member is in the most advanced position relative to the rotational transmitting member. 
     FIG. 14 is an end view of the helical spring used in the valve timing control device shown in FIGS. 12 and 13. 
     FIG. 15 is a vertical cross-sectional view of a fifth embodiment of a valve timing control device in accordance with the prevent invention. 
     FIG. 16 is a vertical cross-sectional view of a sixth embodiment of a valve timing control device in accordance with the prevent invention. 
     FIG.  17 ( a ) is a side view of a known helical spring. 
     FIG.  17 ( b ) is an end view of the helical spring shown in FIG.  17 ( a ). 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A first embodiment of a valve timing control device is shown in FIGS. 1-5 and is applied to an internal combustion engine for vehicles. As shown in FIG. 1, the valve timing control device has a rotary member  1  and a rotational transmitting member  2 . The rotary member  1  is arranged in a torque transmitting route between a crankshaft of the internal combustion engine and a camshaft  3 . The rotary member  1  is fixed to the top or end of the camshaft by way of a bolt  30  so that the rotary member  1  rotates together with the camshaft  3 . The rotational transmitting member  2  rotates relative to the rotary member  1 . 
     The rotational transmitting member  2  includes a housing  20 , a first plate  22  and a second plate  23 . The housing  20  is arranged around the rotary member  1  and has four bores  20   p  for receiving fixing bolts  21  as shown in FIGS. 4 and 5. The axial center of the housing  20  is coincident with the axial center of the rotary member  1 . The first plate  22  serves as a front plate and is arranged on one surface of the housing  20 , and the second plate  23  serves as a rear plate and is arranged on the other surface of the housing  20 . Each of the fixing bolts  21  has a screw portion  21   c  to fix the housing  20 , the first plate  22  and the second plate  23  together. 
     The outer surface of the housing  20  is provided with a timing sprocket  23   a  to connect with a gear  25  of the crankshaft via a transmitting means  24 , for example a timing chain or a timing belt. When the gear  25  of the crankshaft of the internal combustion engine rotates, the housing  20  with the first and second plates  22 ,  23  rotates via the transmitting means  24  and the timing sprocket  23   a . At that time, the housing  20  causes the rotary member  1  with the camshaft  3  to rotate so that the camshaft  3  pushes down the valves of the internal combustion engine so as to open the valves. 
     As shown in FIG. 4, the housing  20  has four projections  4 , each of which extends toward the center of the housing  20 . A sliding surface  48  is formed on the tip of the projections  4  to slide around or along the circumference of the rotary member  1 . Each projection  4  has circumferentially spaced end portions  44   s ,  44   r . A pressure chamber  40  is defined by each of the openings between the projections  44   s ,  44   r . Thus, in this embodiment, there are four pressure chambers  40  which are distributed in the circumferential direction of the housing  20 . Each pressure chamber  40  is encircled or surrounded by the outer circumference of the rotary member  1 , the housing  20 , the first plate  22  and the second plate  23 . 
     Distributed circumferentially about the housing  20  are four vane grooves  41 , each of which faces toward the pressure chamber  40  and receives a vane  5 . The vanes  5  are arranged on imaginary lines P 4  passing through the axial center of the rotary member  1  and arranged so that adjacent ones are at right angles to each other. Each vane  5  divides the respective pressure chamber  40  into a delaying or retarding chamber  42  and an advancing chamber  43 . The delaying chambers  42  are connected with pressure passages. The advancing chambers  43  are connected with other pressure passages. The pressure passages are located in the rotary member  1 . 
     One of the projections  4  has a locking mechanism  6 . The locking member  6  prohibits the rotary member  1  from rotating in the advanced direction relative to the rotational transmitting member  2  when the rotary member  1  is the most delayed or retarded position. The locking mechanism  6  is comprised of a locking body  60  and a spring  61  for urging the locking body  60  toward the axial center of the rotary member  1  (i.e., the direction indicated by the arrow K 1  in FIG.  4 ). Here, the locking body  60  is arranged on an imaginary line P 5  passing through the axial center of the rotary member  1 . 
     When the internal combustion engine is stopped, the rotary member  1  rotates in the delayed direction (i.e., the direction indicated by the arrow S 1  in FIG. 4) and reaches the most delayed position shown in FIG.  4 . Only the vane  5   a  of the plural vanes  5  contacts the end portion  44   r  of the projection  4 . Thus, the contact between the vane  5   a  and the end portion  44   r  is as a stopper for preventing the rotary member  1  from further rotating in the delayed direction relative to the rotational transmitting member  2 . When the rotary member  1  is in the most delayed or retarded position, the locking body  60  of the locking mechanism  6  moves into a locking bore  12  of the rotary member  1  by the urging force of the spring  61  so that the rotary member  1  can not rotate in any direction. This condition is desirable for starting the internal combustion engine. As the fluid pressure is not stable at the starting of the internal combustion engine, the locking mechanism  6  maintains the rotational phase between the rotary member  1  and the rotational transmitting member  2 . 
     After a short period has passed from the starting of the internal combustion engine, the fluid pressure becomes stable. The fluid pressure moves to the top or end of the locking body  60  via a fluid pressure passage formed in the rotary member  1 . The fluid pressure pushes the end or top of the locking body  60  in order to move the locking body  60  in the K 2  direction of FIG.  5 . Thus, the locking mechanism  6  is released so that the rotary member  1  rotates relative to the rotational transmitting member  2 . Therefore, the rotational phase of the camshaft  3  can rotate relative to that of the crankshaft of the internal combustion engine in the S 1  or S 2  direction of FIGS. 4 and 5. 
     When the fluid pressure in the advanced chamber  43  is discharged via an advancing fluid supplying passage and the fluid pressure is supplied into the delayed chamber  42  via a delaying fluid supplying passage, the rotary member  1  with the vanes  5  rotates in the delayed or retarded direction (i.e., the S 1  direction of FIGS. 4 and 5) relative to the housing  20 . 
     On the other hand, when the fluid pressure in the delayed chamber  42  is discharged via the delaying fluid supplying passage and the fluid pressure is supplied into the advanced chamber  43  via the advancing fluid supplying passage, the rotary member  1  with the vanes  5  rotates in the advanced direction (i.e., the S 2  direction of FIGS. 4 and 5) relative to the housing  20 . 
     FIG. 5 illustrates the most advancing condition where the rotary member  1  with the vanes  5  is furthest rotated relative to the housing  20 . As shown in FIG. 5, one vane  5   b  of the plural vanes  5  contacts the end portion  44   s  of one of the projections  4 . Thus, the contact between the vane  5   b  and the end portion  44   s  serves as another stopper for preventing the rotary member  1  from rotating further in the advanced direction relative to the rotational transmitting member  2 . 
     The term “the delayed direction” means that the opening and closing timing of the valves of the internal combustion engine is late while the term “the advanced direction” means that the opening and closing timing of the valves of the internal combustion engine is early. When the rotary member  1  with the vanes  5  rotates in the delayed direction, the capacity of the delayed chamber  42  increases and that of the advanced chamber  43  decreases. When the rotary member  1  with the vanes  5  rotates in the advanced direction, the capacity of the delayed chamber  42  decreases and that of the advanced chamber  43  increases. Therefore, the timing valve control device controls the opening and closing timing of the valves so as to control the engine performance. 
     As shown in FIG. 1, a spring space  80 , which is ring-shaped or annular, is arranged between the first plate  22  of the rotational transmitting member  2  and the rotary member  1 . The spring space  80  consists of a first spring space  81  and a second spring space  82 . The first spring space  81  is formed on the end surface of the rotary member  1  in the axial direction. The second space  82  is formed on the surface of the first plate  22  which faces the first spring space  81 . The first spring space  81  has an inner circumferential wall  81  a, an outer circumferential wall  81   b  and a first groove  1   m . The first groove  1   m  receives a first end portion  27   b  of a helical spring  27 . The first groove  1   m  extends in the radial direction of the rotary member  1  and is formed in the outer circumferential wall  81   b  as shown in FIG.  1 ( b ). The second spring space  82  has an inner circumferential wall  82   a , an outer circumferential wall  82   b  and a second groove  22   m . The second groove  22   m  receives a second end portion  27   c  of the helical spring  27 . The second groove  22   m  extends in the radial direction of the first plate  22  and is formed in the outer circumferential wall  82   b  as shown in FIG.  1 ( c ). 
     The helical spring  27  is made of metal and consists of a torsion spring or coil portion  27   a  having the first end portion  27   b  and the second end portion  27   c  as shown in FIGS. 2 and 3. As shown in FIG. 1, the helical spring  27  is arranged in the spring space  80 . Specifically, the torsion spring or coil portion  27   a  is arranged in the axial direction of the rotary member  1 . As shown in FIG. 3, the end portions  27   b ,  27   c  of the helical spring  27  extend on an imagined radial plane arranged in the radial direction of the coil portion  27   a  and extend in the radial direction of the coil portion  27   a . As illustrated in FIG. 3, the extended length of the first end portion  27   b  (the distance that the first end portion  27   b  extends outwardly from the outer periphery of the coil portion  27   a ) is designated as E 1 , and the extended length of the second end portion  27   c  (the distance that the second end portion  27   c  extends outwardly from the outer periphery of the coil portion  27   a ) is designated as E 2 . 
     As shown in FIGS.  1 ( a ),  1 ( b ) and  1 ( c ), the first end portion  27   b  of the helical spring  27  is engaged with the rotary member  1  and the second end portion  27   c  of the helical spring  27  is engaged with the first plate  22  of the rotational transmitting member  2 . The helical spring  27  urges the rotary member  1  in the advanced direction (i.e., the &#39;S 2 ” direction in FIGS. 4 and 5) relative to the housing  20 . The purpose of the urging force of the helical spring  27  is to offset the above-mentioned force which occurs during the internal combustion engine driving (i.e., the force received by the rotary member and associated with the cams pushing the valves of the internal combustion engine during engine operation). 
     As shown in FIGS.  1 ( a ),  1 ( b ) and  1 ( c ), the width of the first spring space  81  which is formed between the inner circumferential wall  81   a  and the outer circumferential wall  81   b  is larger than the thickness of the coil portion  27   a . There are thus plenty of gaps  91  between the torsion spring  27   a  and the walls  81   a ,  81   b  in the first spring space  81 . Further, in much the same way, there are plenty of gaps  92  between the coil portion  27   a , the inner circumferential wall  81   a  and the outer circumferential wall  81   b  in the second spring space  82 . When the rotary member  1  rotates in any direction relative to the housing  20  of the rotational transmitting member  2 , the coil portion  27   a  is twisted. However, the gaps  91 ,  92  inhibit or prevent the coil portion  27   a  from touching the circumferential walls  81   a ,  81   b ,  82   a ,  82   b  so as to obtain the expected urging force. 
     According to the embodiment described above, both end portions  27   b ,  27   c  extend in the radial direction of the torsion spring  27   a  as shown in FIGS.  1 ( b ),  1 ( c ),  2  and  3 . The axial length LA of the helical spring  27  is the same as the length of the coil portion  27   a . Therefore, the total axial length of the valve timing control device becomes relatively small. In addition, even if the relative rotation between the rotary member  1  and the rotational transmitting member makes the diameter of the coil portion  27   a  small, the engagement portion of the end portions  27   b ,  27   c  are secured. Therefore, the engagement condition of the helical spring  27  between the rotary member  1  and the rotational transmitting member  2  is maintained. 
     FIGS. 6-8 illustrate a second embodiment of the valve timing control device. In this second embodiment, the parts of the valve timing control device that are the same as those in the first embodiment are identified with the same reference numerals as those used in FIGS. 1-5. Having described such features above, a detailed description of such features will not be repeated. 
     As shown in FIGS. 6 and 7, an enlarged projection  95  is provided on the inner circumferential wall  81   a . The outwardly directed enlarged projection  95  extends in the axial direction of the rotary member  1 . As shown in FIG. 8, another outwardly directed enlarged projection  96  is provided on the inner circumferential wall  82   a . This enlarged projection  96  extends in the same direction as the enlarged projection  95 . The enlarged projections  95 ,  96  are adapted to engage portions of the coil portion  27   a  adjacent the two end portions  27   b ,  27   c  as shown in FIGS. 6-8. The enlarged projections  95 ,  96  thus inhibit or prevent the inner surface of the coil portion  27   a  from coming into contact with the inner circumferential walls  81   a ,  82   b . Here, if the rotary member  1  and the first plate  22  are made of sintering material or casting material, forming the enlarged projections  95 ,  96  is relatively easy. Even if the relative rotation between the rotary member  1  and the rotational transmitting member  2  causes the diameter of the coil portion  27   a  to become small, the inner surface of the coil portion  27   a  contacts substantially only the enlarged projections  95 ,  96 . Therefore, this second embodiment provides not only the advantages described above in connection with the first embodiment, but also the additional advantage that the frictional resistance between the helical spring  27  and the inner circumferential walls  81   a ,  82   a  do not have to be enlarged. 
     FIGS. 9-11 illustrate a third embodiment of the valve timing control device. The parts of the valve timing control device that are the same as those in the first embodiment are identified with the same reference numerals as those used in FIGS. 1-5. Having described such features above, a detailed description of such features will not be repeated. 
     In this third embodiment, the helical spring  27  has two inwardly directed curved portions  97 ,  98 . The curved portion  97  is arranged at the one end, which is the end wire rod, of the coil portion  27   a , near the base of the end portion  27   b  (i.e., where the end portion  27   b  meets the coil portion  27   a ). The curve portion  98  is arranged at the other end wire rod of the coil portion  27   a , near the base of the end portion  27   c  (i.e., where the end portion  27   c  meets the coil portion  27   a ). Even if the relative rotation between the rotary member  1  and the rotational transmitting member  2  causes the diameter of the coil portion  27   a  to become small, the inner surface of the coil portion  27   a  substantially does not contact the inner circumferential walls  81   a ,  82   a . Rather, only the tops of the curve portions  97 ,  98  contact the circumferential walls  81   a ,  82   a . This third embodiment provides advantages similar to those described above in connection with the second embodiment. 
     FIGS. 12-14 illustrate a fourth embodiment of the valve timing control device. The parts of the valve timing control device that are the same as those in the first embodiment are identified with the same reference numerals as those used in FIGS. 1-5. Having described such features above, a detailed description of such features will not be repeated. 
     As shown in FIG. 14, the curvature (radius of curvature) of both end wire rods of the coil portion  27   a  are smaller than the curvature (radius of curvature) of the wire rod forming the other portion (middle portion) of the torsion spring  27   a . Thus, the coil portion  27   a  of the fourth embodiment has two smaller diameter portions  100 ,  102 . The smaller diameter portion  100  is arranged on one end wire rod of the coil portion  27   a , near the base of the end portion  27   b  (i.e., where the end portion  27   b  meets the coil portion  27   a ). The other smaller diameter portion  102  is arranged on the other end wire rod of the coil portion  27   a , near the base of the end portion  27   c  (i.e., where the end portion  27   c  meets the coil portion  27   a ). Even if the relative rotation between the rotary member  1  and the rotational transmitting member  2  causes the diameter of the coil portion  27   a  to become small, the inner surface of the coil portion  27   a  does not contact the inner circumferential walls  81   a ,  82   a . Rather, only the tops of the small diameter portions  100 ,  102  contact the walls  81   a  and  82   a . Therefore, this fourth embodiment provides similar advantages to those associated with the second and third embodiments. 
     In the above-described embodiments, four pressure chambers  40  and vanes  5  are provided. However, the number of vanes and pressure chambers is not limited in this regard. Also, as described above, the rotational transmitting member  2  is rotated by the crankshaft and the rotary member  1  is attached to the cam shaft  3 . However, it is also possible for the rotary member  1  to be rotated by the crankshaft while the housing member  20  of the rotational transmitting member  2  is integrally attached on the cam shaft  3 . Further, the vanes  5  can be integrally mounted on the rotary member  1 . 
     Additionally, in the above-described embodiments, the vanes  5  are supported on the rotary member  1 . However, it is also possible to support the vanes  5  on the housing  20  of the rotational transmitting member  2 . 
     In the embodiments described above, the locking body  60  provides a lock between the rotary member  1  and the housing  20  when the rotary member  1  rotates relative to the housing  20  and is at the most delayed position. However, it is possible that the locking body  60  provides a lock when the rotary member  1  is positioned at an intermediate portion between the most delayed position and the most advanced position. It is also possible that the locking body  60  provides the lock when the rotary member  1  is at the most advanced position. This type of valve timing control device is normally used for the camshaft  3  for operating exhaust valves. 
     Regarding the lengths of the first and second end portions  27   b ,  27   c , end portions  27   b ,  27   c  of the same length are desirable. However, it is also possible for one length to be longer than the other one. Of course, it is also acceptable that only one end portion  27   b ,  27   c  extends on the radial surface of the coil portion  27   a . In this case, it is preferred that the second end portion  27   c  extend on the radial surface of the coil portion  27   a  because the total axial length of the valve timing control device can be made relatively small. 
     In addition, in the embodiments described above, the end portions  27   b ,  27   c  extend in the radial direction of the coil portion  27   a . However, the precise angle of the end portions  27   b ,  27   c  is not important, but both of the end portions  27   b ,  27   c  are on the same surface, which is the axial direction of the coil portion  27   a . Thus, it is possible that the angle between the end portions  27   b ,  27   c  and the end of the torsion spring is not a right angle. It is also possible for the end portion  27   b  and/or  27   c  to be extended in the inner direction of the torsion spring  27   a.    
     FIG. 15 illustrates a fifth embodiment of the valve timing control device. The parts of the valve timing control device that are the same as those in the first embodiment are identified with the same reference numerals as those used in FIGS. 1-5. Having described such features above, a detailed description of such features will not be repeated. 
     As shown in FIG. 15, a pulley  104  connected with the gear  25  of the crankshaft via the transmitting means  24  is fixed on the second plate  23  of the rotational transmitting member  2  by way of bolts  137 . The bolts  137  are bored through or positioned at the outer end portion  23   a  of the second plate  23 . 
     A front cover  134  is made from a sheet of pressed iron plate. The front cover  134  has a bottom or end wall  134   a , a circumferential wall  134   b  and an outer circumferential portion  134   c . The bottom wall  134  faces the first plate  22 , the circumferential wall  134   b  faces the housing  20  and the outer circumferential portion  134   c  faces the outer end portion  23   a  of the second plate  23 . The outer circumferential portion  134   c , the outer end portion  23   a  and the pulley  104  are integrally fixed by the bolts  137 . 
     The surface of the outer end portion  23   a  of the second plate  23  which faces the outer circumferential portion  134   c  is provided with a U-shaped groove  23   b . The groove  23   b  is a circular groove extending around the housing  20 . A seal ring  138  is positioned in the groove  23   b  to prevent oil from leaking. 
     The bottom or end wall  134   a  of the front cover  134  has a hole or through opening  134   d  for screwing or tightening the bolt  30 . The hole  134   d  is closed liquidly (in a liquid-tight manner) by a lid  35 . Thus, the front cover  134  covers the rotational transmitting member  2  for protecting the transmitting means  24 , for example the timing belt, against the pressure fluid. In addition, it is not necessary to secure any space for inserting the seal ring  138 . Therefore, the axial length of the rotational transmitting member  2  is relatively small. 
     FIG. 16 illustrates a sixth embodiment of the valve timing control device according to the present invention. The parts of the valve timing control device that are the same as those in the first embodiment are identified with the same reference numerals as those used in FIGS. 1-5. Having described such features above, a detailed description of such features will not be repeated. 
     As shown in FIG. 16, a bolt receiving bore of the second plate  23  is a bottomed bore or blind bore  23   c . Thus, the sealing characteristic around the fixing bolt  21  are improved. 
     The principles, preferred embodiments and modes of operation of the present invention have been described in the foregoing specification. However, the invention which is intended to be protected is not to be construed as limited to the particular embodiments disclosed. Further, the embodiments described herein are to be regarded as illustrative rather than restrictive. Variations and changes may be made by others, and equivalents employed, without departing from the spirit of the present invention. Accordingly, it is expressly intended that all such variations, changes and equivalents which fall within the spirit and scope of the present invention as defined in the claims, be embraced thereby.