Valve timing control devices

Abstract: A valve timing control device (30) includes a rotor (68) fixed on a cam shaft (34). A housing (50) is rotatably mounted on the cam shaft (34) so as to surround the rotor (68). A chamber (60) between the housing (50) and the rotor (68) has a pair of circumferentially opposed walls (50b1, 50b2). A vane (74) mounted on the rotor (68) extends outwardly therefrom in the radial direction into the chamber (60) to divide the chamber (60) into a first pressure chamber (80) and a second pressure chamber (82). A device (92,98,94) supplies fluid under pressure to at least a selected one of the first pressure chamber (80) and the second pressure chamber (82). A locking mechanism (104) connects the housing (50) and the rotor (68). A device (66,106) cancels the locking mechanism (104) and keeps the locking mechanism (104) cancelled by the fluid pressure from the supplying device (92,98,94).

Description: Technical Field The invention relates to valve timing control devices for controlling the angular phase difference between the crank shaft and the cam shaft of a combustion engine. In general, valve timing is determined by mechanisms driven by cam shafts according to a characteristic of the engine or of its operation. The combustion changes in response to the rotational speed, so it is difficult to obtain optimum valve timing throughout the whole rotational range. Therefore, a device which is able to change the valve timing in response to the condition of the engine is desirable. Background Art The relevant parts of U.S. 4,858,572 are reproduced as Fig. 10 and Fig. 11 hereof. This device includes a rotor 3 which is fixed on a cam shaft 4 rotabably supported on a cylinder head 14. A drive pulley 1 is driven by rotational torque from a crank shaft (not shown) and rotatably mounted on the cam shaft 4 so as to surround the rotor 3. A plurality of chambers 8 between the drive pulley 1 and the rotor 3 each have a pair of circumferentially opposed walls 1a, 1b. A plurality of vanes 2 are mounted on the rotor 3 and extend outwardly therefrom in the radial direction into the chambers 8 so as to divide each into a first pressure chamber 9 and a second pressure chamber 9b. Each of the vanes 2 is provided with two hole 2a, 2b in which coil springs 25a, 25b are disposed therein so as to urge each of the vanes outwards in the radial direction. An outer plate 5 is fixed to the cam shaft 4 via a plate 21 by a bolt 20 so as to define the chambers 8 with the cam shaft 4 and the drive pulley 1 and so as to locate the vanes 2 in the axial direction. In this device, a fluid under pressure is supplied to a selected one of the first pressure chamber 9 and the second pressure chamber 9a by a control valve 15 in response to the running condition of the combustion engine and an angular phase difference between the crank shaft and the cam shaft 4 is controlled so as to advance or retard the valve timing relative to the crank shaft. The control valve 15 has a solenoid 13, a spring 16 and a valve spool 18 and operates in response to the current supplied to the solenoid 13 so that the fluid under pressure is supplied from an oil pump (not shown) to a passage 10 or a passage 11. The passage 10 is communicated with the first pressure chamber 9 and the passage 11 is communicated with the second pressure chamber 9a. When the fluid is supplied to the first pressure chamber 9 via the passage 10 by the control valve 15, the vanes 2 and the cam shaft 4 are rotated clockwise relative to the drive pulley 1 and the valve timing is advanced relative to the crank shaft. When the fluid is supplied to the second pressure chamber 9a via the passage 11 by the control valve 15, the vanes and the cam shaft 4 are rotated counterclockwise relative to the drive pulley 1 and the valve timing is retarded relative to the crank shaft. The valve timing control device is in the position of the maximum advanced condition, when each of the vanes 2 contacts with the opposed wall 1a of each of the chambers 8. On the other hand, the valve timing control device is in the position of the maximum retarded condition, when each of vanes 2 contacts with the opposed wall 1b of each of the chambers 8. A radial hole 1c is formed on the drive pulley 1 and a first lock pin 22 which is urged inward by a spring 23 is slidably fitted into the radial hole 1c. A radial hole 24 is formed on the rotor 3 so as to align with the radial hole 1c when the valve timing control device is in the position of the maximum retarded condition. Further, a radial hole 1d is formed on the drive pulley 1 and a second lock pin 22a which is urged inward by a spring 23a is slidably fitted into the radial hole 1d. A radial hole 24a is formed on the rotor 3 so as to align with the radial hole 1d when the valve timing control device is in the position of the maximum advanced condition. If the fluid pressure supplied to the chambers 8 from the oil pump (not shown) is not high enough when the engine is started or when the rotational torque is transmitted to the drive pulley, the walls 1b of the drive pulley 1 come into collision with the vanes 2 and noise is generated. Relative rotation between the rotor 3 and the drive pulley 1 is prevented at the maximum advanced condition and the maximum retarded condition by the lock pins 22, 22a. Thus, noise is prevented. However, the lock pins 22, 22a move in the radial holes 24, 24a every time the device is in the maximum advanced or the maximum retarded position during engine running. Thus, the lock pins 22, 22a wear and the reliability of the whole device is decreased. The Invention A valve timing control device for an engine according to the invention comprises: a rotor fixed on a cam shaft; a housing rotatably mounted on the cam shaft so as to surround the rotor; a chamber between the housing and the rotor having a pair of circumferentially opposed walls; a vane mounted on the rotor and extending outwardly therefrom in the radial direction into the chamber to divide the chamber into a first pressure chamber and a second pressure chamber; supply means for supplying fluid under pressure to at least a selected one of the first pressure chamber and the second pressure chamber; locking means for connecting the housing and the rotor, the locking means comprising a pair of radially aligned holes in the housing and the rotor respectively, and a locking pin slidably received in one of the holes but biased by a spring to extend from that hole into the other of the holes; and cancelling means supplied with fluid under pressure from the fluid supply means for overcoming the bias of the spring thereby cancelling the locking means and keeping the locking means cancelled while the engine is in operation. Drawings Fig. 1 is a section through a first valve timing control device in accordance with the invention; Fig. 2 is a cross-section on A-A of Fig. 1 in a maximum retarded condition; Fig. 3 is a cross-section on A-A of Fig. 1 in a maximum advanced condition; Fig. 4 is a cross-section on A-A of Fig. 1 in a maximum retarded condition on starting the engine; Fig. 5 is a section through a second valve timing control device in accordance with the invention; Fig. 6 is a cross-section on B-B of Fig. 5; Fig. 7 is similar to Fig. 6 and shows a condition which is advanced a little from a maximum retarded condition; Fig. 8 is a section through a third valve timing control device in accordance with the invention; Fig. 9a is a cross-section of part of a fourth valve timing control device in accordance with the invention in a maximum retarded condition; Fig. 9b is similar to Fig. 9a and shows a condition which is changed from a maximum retarded condition to an advanced condition; Fig. 9c also is similar to Fig. 9a and shows a condition which is advanced a little from a maximum retarded condition; Fig. 10 is a section of a prior device as discussed above; and Fig. 11 is a cross section on D-D of Fig. 13. In Figs. 1 to 4 the valve timing control device is applied to a DOHC Double Over Head Cam Shaft engine. Referring to Fig. 1, an exhaust cam shaft 34 (a first cam shaft) and an intake cam shaft 36 (a second cam shaft) are rotatably mounted on a cylinder head 32 of an engine and are connected each other by a rotational torque transmitting means 56. The rotational torque transmitting means 56 is comprised of a gear 38 which is rotatably mounted on the exhaust cam shaft 34 and a gear 40 which is fixedly mounted on the intake cam shaft 36. An end of the exhaust cam shaft 34 is projected out of the cylinder head 32 and a timing pulley 42 is fixed to this projecting end of the exhaust cam shaft 34 by a bolt 44. A stopper pin 46 is fixed to the projecting end of the exhaust cam shaft 34 and is fitted into a notch formed on the timing pulley 42 so that the relative rotation between the timing pulley 42 and the exhaust cam shaft 34 is prevented. Rotational torque is transmitted to the timing pulley 42 via a belt 49a from a crank shaft 49 which is rotated by the engine. A cylindrical portion of the exhaust cam shaft 34 which is extended into the cylinder head 32 is provided with a male screw portion 34a on which a male screw is formed and a passage portion on which a circular groove 34b is formed in order from a front side (left side in Fig. 1). At the adjacent portion of the passage portion (at the right side of the passage portion in Fig. 1), a journal portion 34c having a larger diameter than the that of the passage portion is formed and a plurality of cam portions (not shown) are continuously formed at the right side of the journal portion 34c. On the journal portion 34c, the gear 38 having three female screw holes which are penetrated in the axial direction which are separated in the cicumferential direction at regular intervals is rotatably mounted thereon. On the passage portion of the exhaust cam shaft 34, a valve timing control mechanism 30 is mounted thereon. As shown in Fig. 2 to Fig. 4, the valve timing control mechanism 30 includes a rotor 68, five vanes 74, a housing member 50, a circular front plate 48 and a circular rear plate 52. The rotor 68 has a cylindrical shape and is fixedly mounted on the passage portion of the exhaust cam shaft 34 by a pin 70. The pin 70 is pressed in the passage portion of the exhaust cam shaft 34 in the radial direction and is fitted into a notch portion 35 formed on the inner circumferential portion of the rotor 68 so that the relative rotation between the rotor 68 and the exhaust cam shaft 34 is prevented. The housing member 50 has a cylindrical shape having an inner bore 50a and is rotatably mounted on the outer circumferential surface of the rotor 68 so as to surround the rotor 68. The housing member 50 has the same axial length as the rotor 68 and is provided with five grooves 50b which are outwardly extended from the inner bore 50a in the radial direction and which are separated in the circumferential direction. The housing member 50 is also provided with three holes which are penetrated in the axial direction and which are separated in the circumferential direction at regular intervals. The rear plate 52 is rotatably mounted on the journal portion 34c so as to locate between the gear 38 and one side faces of the housing 50 and the rotor 68 and is provided with three holes which are penetrated in the axial direction and which are separated in the circumferential direction at regular intervals. The front plate 48 is located so as to be opposite to the other aide faces of the housing member 50 and the rotor 68 and is provided with three holes which are penetrated in the axial direction and which are separated in the circumferential direction at regular intervals. Three bolts 86 are fitted into the holes of the front plate 48, the housing member 50 and the rear plate 52 and are screwed into the female screw holes of the gear 38. Thereby, the front plate 48 is fluid-tightly pressed to the other side face of the housing 50 and the rear plate 52 is fluid-tightly pressed to one side face of the housing 50. Now, one side face of the rotor 68 is contacted with a stepped portion of the journal portion 34c and under this condition a nut 72 is screwed onto the male screw portion 34a of the exhaust cam shaft 34 so as to press the rotor 68 toward the journal portion 34c. Thereby, rotor 68 is rotated with the exhaust cam shaft 34 in a body. Thereby, five chambers 60 which are separated in the cicumferential direction at regular intervals and each of which has a pair of circumferentially opposed walls 50b1, 50b2 are defined among the rotor 68, the housing member 50, the front plate 48 and the rear plate 52. On the outer circumferential portion of the rotor 68, five grooves 76 which are extended inwardly therefrom in the radial direction and which are separated in the cicumferential direction are formed thereon. Five vanes 74 which are extended outwardly in the radial direction into the chambers 60 are mounted in the grooves 76, respectively. Thereby, each of chambers 60 is divided into a first pressure chamber 80 and a second pressure chamber 82, both of which are fluid-tightly separated from each other. A plate spring (not shown) is interposed between the bottom of the groove 76 and the vane 74 and thereby the vanes 74 are normally urged outwards. The rotor 68 is provided with five first passages 68a and five second passages 68b. One end of each of the first passages 68a is communicated with each of radial holes 84a and the other end of each of the first passages 68a is communicated with each of the first pressure chambers 80. On the other hand, one end of each of the second passages 68b is communicated with the circular groove 34b and the other end of each of the second passages 68b is communicated with each of the second pressure chambers 82. Each of the radial holes 84a extends radially outward from a passage 84 which is formed in the exhaust cam shaft 34 at its axial center and which is extended in the axial direction. The circular groove 34b is communicated with a pair of passages 86 which are formed in the exhaust cam shaft 34 so as to locate on the coaxial circle about the axial center of the shaft 34 and which are extended in parallel in the axial direction. A portion which is located between the cylindrical portion and the projecting end portion of the exhaust cam shaft 34 is rotatably supported on the cylinder head 32 and a cover (not shown) and is provided with a circular groove 90. The circular groove 90 is communicated with the passages 86. The supporting surfaces of the cylinder head 32 and the cover (not shown) for supporting the exhaust cam shaft 34 is provided with a circular groove 88. The circular groove 88 is communicated with the passage 84 via a passage 84b. A fluid supplying device is comprised of a changeover valve 92, a fluid pump 98 and a controller 94. In this embodiment, the changeover valve 92 is an electromagnetic valve which is 4 ports - 3 positions type. The fluid pump 98 is driven by the engine. The pump 98 may be a pump for lubricating the engine. The circular groove 88 is communicated to a A port of the changeover valve 92 and the circular groove 90 is communicated to a B port of the changeover valve 92. A P port of the changeover valve 92 is communicated to a discharge portion the fluid pump 98 and a R port of the changeover valve 92 is communicated to a reservoir 96. The position of the changeover valve 92 is controlled by the controller 94 so that a first condition 92a in which the discharged fluid from the pump 98 is supplied to the circular groove 88 and in which the circular groove 90 is communicated to the reservoir 96, a second condition 92b in which the communication between the circular grooves 88, 90 and the pump 98 and the reservoir 96 are interrupted, respectively and in which the discharged fluid from the pump 98 is supplied to the reservoir 96 and a third condition 92c in which the discharged fluid from the pump 98 is supplied to the circular groove 90 and in which the circular groove 88 is communicated to the reservoir 96 are selectively obtained. The controller 94 controls the above conditions of the changeover valve 92 based on parameter signals such as an engine speed, an amount of opening of a throttle valve (not shown) and so on. A locking mechanism 104 is disposed between the rotor 68 and the housing member 50. The locking mechanism 104 includes a receiving hole 112 which is formed on the outer circumferential portion of the rotor 68, a stepped cancelling hole 62 which is formed on the inner circumferential portion of the housing member 50 so as to be able to align with the receiving hole 112 and a stepped locking pin 106 which is slidably fitted into the cancelling hole 62. The cancelling hole 62 has a stepped portion 64 and a small diameter portion 66 which is opened into the inner circumference of the housing member 50 and whose diameter is the same as that of the receiving hole 112. In the radially outer end portion of the cancelling hole 62, a snap ring and a retainer are fixed therein and a spring 108 is disposed between the retainer and the locking pin 106 so as to urge the locking pin 106 inwardly. The locking pin 106 has a small diameter portion 110 whose outer diameter is nearly the same as the diameter of the small diameter portion 66 of the cancelling hole 62 and a large diameter portion 111. Thereby, the small diameter portion 110 of the locking pin 106 can be fitted into the small diameter portion 66 of the cancelling hole 62 and the receiving hole 112 by the spring 108 when the receiving hole 112 is aligned with the cancelling hole 62 at the maximum retarded condition. The receiving hole 112 is communicated with the passage 84 via a radial hole 84c and a radial hole 68c which are formed on the cam shaft 34 and the rotor 68, respectively. Further, a circular space 62a which is formed between the large diameter portion 111 of the locking pin 106 and the stepped portion 64 of the cancelling hole 62 is communicated with the adjacent second pressure chamber 82 via a passage 114 which is formed on the housing member 50. The operation of the valve timing control device having the above structure will now be described. On start-up of the engine, the exhaust cam shaft 34 is rotated counterclockwise by the timing pulley 42 in Fig. 2 . Thereby, exhaust valves (not shown) are opened and closed. Simultaneously, the rotor 68 is rotated and then gear 38 is rotated via the vanes 74, the housing member 50 and the bolts 54. The rotation of the gear 38 is transmitted to the gear 40 and then the intake cam shaft 36 is rotated so that intake valves (not shown) are opened and closed. At this time, the pressure in the chambers 60 decreases while the engine is stopped therefore it takes a predetermined time to increase the pressure in the chambers 60 by the pressurized fluid from the oil pump 98 after the starting of the engine. Therefore, the rotor 68 is rotated relative to the housing member 50 to the maximum retarded condition in which each of the vanes 74 contacts with each of the opposed wall 50b2 shown in Fig. 2 and Fig. 4. In this condition, the receiving hole 112 is aligned with the cancelling hole 62, the small diameter portion 110 of the locking pin 106 is fitted into the receiving hole 112 by the spring 108 as shown in Fig. 4 and the rotor 68 and the housing member 50 are connected with each other. Thereby, the vanes 74 are prevented from colliding with the housing member 50 by the variation of torque acting on the cam shaft 34 and the generation of noise is prevented. Now, at this time, the changeover valve 92 is in the first condition 92a. When the pressure of the fluid discharged from the oil pump 98 becomes sufficient and with the changeover valve 92 in the first position, the pressurized fluid is supplied to the first chambers 80 and simultaneously to the receiving hole 112. Thereby, the locking pin 106 is pushed out from the receiving hole 112 against the urging force of the spring 108 as shown in Fig. 2 and relative rotation between the housing member 50 and the rotor 68 is allowed. Then, the housing member 50, the front plate 48 and the rear plate 52 are rotated counterclockwise with the gear 38 relative to the rotor 68 by the pressure in the first pressure chambers 80 towards the maximum advanced condition in which the vanes 74 contact with the opposed walls 50b1, respectively as shown in Fig. 3 and in which the angular phase of the intake cam shaft 36 is advanced relative to that of the the crank shaft 49 by maximum value. In this condition, if pressurized fluid is supplied from the pump 98 to the second pressure chambers 82 by the changeover valve 92 moving to the third condition, the housing member 50, the front plate 48 and the rear plate 52 are rotated clockwise relative to the exhaust cam shaft 34 in Fig. 3. Thereby, the valve timing control mechanism moves to the position of the maximum retarded condition in which the vanes 78 are contacted with the walls 50b2 and in which the angular phase of the intake cam shaft 36 is retarded relative to that of the crank shaft 49 by maximum value from the above mentioned maximum advanced condition as shown in Fig. 3. At this time, although the pressure in the receiving hole 112 is decreased, the pressure in the adjacent second pressure chamber 82 is applied to the circular space 62a. Therefore, the locking pin 106 is in the condition in which the small diameter portion 110 is pushed out from the receiving hole 112. Now, depending on the manner in which the control of the changeover valve 92 is executed, the vanes 74 can be stopped in any position (intermediate advanced position) between the maximum advanced position and the maximum retarded position. This requires that balance be achieved between the fluid pressure of the first pressure chambers 80 and the fluid pressure of the second pressure chambers 82 when the vanes 74 have achieved an arbitrary position. The amount of the advance can therefore be set to any value between a zero level and a maximum level. As mentioned above, the opening and closing timing of the intake valves (not shown) driven by the intake cam shaft 36 is adjusted and the angular phase difference between the crank shaft 49 and the intake cam shaft 36 is adjusted. As mentioned above, according to the first embodiment, the locking pin 106 is pushed out from the receiving hole 112 during the running of the engine or when the supplied fluid pressure from the oil pump 98 is sufficiently high. Only when the engine is started or the supplied fluid pressure from the oil pump 98 is not sufficiently high isthe locking pin 106. fitted into the receiving hole 112. Therefore, the number of the operations by the locking pin 106 is remarkably reduced and thereby the durability and the reliability of the locking mechanism 104 is remarkably improved. Fig. 5 to Fig. 7 show a second embodiment of the present invention. In Fig. 5 to Fig. 7, the same parts as compared with Fig. 1 to Fig. 4 are identified by the same reference numerals. Referring to Fig. 5 to Fig. 7, a cam shaft 200 which is provided with a plurality of cam portions (not shown) driving valves (not shown) is rotatably supported on a cylinder head (not shown) of an engine at its plural journal portions. An end of the cam shaft 200 is projected out of the cylinder head and a timing gear 201 is rotatably mounted on this projecting end of the cam shaft 200. Rotational torque is transmitted to the timing gear 201 via a chain 202 from a crank shaft 203 which is rotated by the engine. The timing gear 201 is provided with three female screw holes which are penetrated in the axial direction and which are separated in the cicumferential direction at regular intervals. A cylindrical rotor 204 having a stepped inner bore 204a is fixedly mounted on the projecting end of the cam shaft 200 by a pin (not shown) so that the relative rotation between the rotor 204 and the cam shaft 200 is prevented. The rotor 204 is fitted onto the projecting end of the cam shaft 200 at its large diameter portion of the stepped inner bore 204a and a stepped portion between the large diameter portion and a small diameter portion of the stepped inner bore is contacted with a top surface of the projecting end of the cam shaft 200. One side surface of the rotor 204 is contacted with the flat surface of the timing gear 201. A cylindrical housing member 205 having a inner bore 205a is rotatably mounted on the outer circumferential surface of the rotor 204 so as to surround the rotor 204. The housing member 205 has the same axial length as the rotor 204 and is provided with five grooves 205b which are outwardly extended from the inner bore 205a in the radial direction and which are separated in the circumferential direction. The housing member 205 is further provided with three penetrating holes in the axial direction which are separated from each other at regular intervals. One side surface of the housing 205 is contacted with the flat surface of the timing gear 201. A circular front plate 206 which is provided with three penetrating holes in the axial direction which are separated from each other at regular intervals is disposed adjacent to the other side surfaces of the rotor 204 and the housing member 205. Each of the holes of the front plate 206, each of the holes of the housing member 205 and each of the female screw holes of the timing gear 201 are coaxially arranged each other and a bolt 207 is fitted into each of the coaxially arranged holes. Each of the bolts 207 is screwed into each of the female screw holes of the timing gear 201. Thereby, the housing member 205, the timing gear 201 and the front plate 206 are united. The flat surface of the timing gear 201 is fluid-tightly pressed onto one side surfaces of the rotor 204 and the housing member 205 and one side surface of the front plate 206 is fluid-tightly pressed onto the other side surfaces of the rotor 204 and the housing member 205. A central screw hole 200a which is opened outside is formed at a axial center of the projecting end of the cam shaft 200. A central bolt 207 is screwed into the central screw hole 200a and thereby the rotor 204 is fixed to the projecting end of the cam shaft 200. Thereby, five chambers 208 which are separated in the cicumferential direction and each of which has a pair of circumferentially opposed walls 205b1, 205b2 are defined among the rotor 204, the housing member 205, the front plate 206 and the timing gear 201. On the outer circumferential portion of the rotor 204, five grooves 204c which are extended inwardly therefrom in the radial direction and which are separated in the cicumferential direction are formed thereon. Five vanes 209 which are extended outwardly in the radial direction into the chambers 208 are mounted in the grooves 205c, respectively. Thereby, each of chambers 208 is divided into a first pressure chamber 208a and a second pressure chamber 208b, both of which are fluid-tightly separated from each other. Numeral 218 is a plate spring which urges each of the vane 209 outwards in the radial direction. The rotor 204 is provided with five first passages 211 and five second passages 210. One end of each of the first passages 21 is communicated with a circular groove 213 which is formed on the large diameter portion of the stepped bore 204a of the rotor 204. The other end of each of the first passages 211 is communicated with each of the first pressure chambers 208a. On the other hand, one end of each of the second passage 210 is communicated with a circular groove 212 which is formed on the outer circumferential portion of the projecting end of the cam shaft 200. The other end of each of the second passages 210 is communicated with each of the second pressure chambers 208b. The circular groove 213 is communicated with a pair of grooves which are symmetrically formed with regard to the axial center of the cam shaft 200 on the top surface of the projecting end of the cam shaft 200. The grooves are communicated with a pair of passages 214 which are formed on a coaxial circle about the axial center of the cam shaft 200 and which are extended in the axial direction. The circular groove 212 is communicated with a pair of passages 215 via a pair of radial passages which are symmetrically formed with regard to the axial center of the cam shaft 200 in the projecting end and which are extended in the radial direction. The passages 214 are formed on the coaxial circle about the axial center of the cam shaft 200 and are separated from the passages 215 in the circumferential direction at a predetermined angle. The passages 215 are extended in the axial direction and a ball is pressed into one end of each passages 215 which is opened toward the stepped portion of the rotor 204. A pair of circular grooves 216 and 217 are formed on the journal portion of the cam shaft 200. The circular groove 216 is communicated with the passages 214. The circular groove 217 is communicated with the passages 215. A fluid supplying device is comprised of a changeover valve 219, a fluid pump 220 and a controller 221. In this embodiment, the changeover valve 219 include a housing 219a having five connecting ports 219a1 to 219a5, a spool 219b, a spring 219c and a solenoid 219d. The spool 219b is located in an initial position shown in Fig. 5 when the current is not supplied to the solenoid 219d and the spool 219b is moved rightward against the spring 219c when the current is supplied to the solenoid 219d by the controller 221 based on parameter signals such as an engine speed, an amount of opening of a throttle valve (not shown) and so on. The first connecting port 219a1 is communicated to the discharged side of the oil pump 220, the second connecting port 219a2 is communicated to the circular groove 216 via a passage 223, the third connecting port 219a3 is communicated to the circular groove 217 via a passage 224 and the fourth and fifth connecting ports 219a4, 219a5 are communicated to a reservoir 222. Thereby, the pressurized fluid is supplied from the oil pump 220 to the circular groove 216 when the current is not applied to the solenoid 219d. When the current is applied to the solenoid 219d, the pressurized fluid is supplied from the oil pump 220 to the circular groove 217. A locking mechanism 223 is disposed between the rotor 204 and the housing member 205. The locking mechanism 223 includes a receiving hole 224 which is formed on the outer circumferential portion of the rotor 204, a cancelling hole 225 whose diameter is almost the same as that of the receiving hole 224 and which is formed on the inner circumferential portion of the housing member 205 so as to be able to align with the receiving hole 224 when the valve timing control device is in a maximum retarded condition and a locking pin 226 which is slidably fitted into the cancelling hole 225. The outer end of the cancelling hole 225 is closed by a cover 227 having a small hole and a spring 228 is disposed between the locking pin 226 and the cover 227 so as to urge the locking pin 226 inwardly. Thereby, the locking pin 226 can be fitted into the receiving hole 224 by the spring 228 when the receiving hole 224 is aligned with the cancelling hole 225 at the maximum retarded condition in which the vanes 209 contact with the walls 205b1 of the housing member 205 as shown in Fig. 6. The receiving hole 224 is communicated with the circular groove 212 via a radial hole 229 which is formed on the rotor 204. The operation of the valve timing control device having the above structure will now be described. With the starting of the engine, the cam shaft 200 is rotated clockwise by the timing gear 201 in Fig. 5. Thereby, the housing member 205 is rotated and the rotational torque of the housing member 205 is transmitted to the rotor 204 via the vanes 209. Then, the cam shaft 200 is rotated clockwise in Fig. 6 and the valves (not shown) are opened and closed. At this time, the pressure in the chambers 208 is low and therefore it takes a predetermined time to increase the pressure in the chambers 208 by the pressurized fluid from the oil pump 220 after the starting of the engine. Therefore, the housing member 205 is rotated relative to the rotor 204 until the maximum retarded condition in which the each of the vanes 209 contacts with each of the opposed walls 205b1 shown in Fig.6. In this condition, the receiving hole 224 is aligned with the cancelling hole 225, the locking pin 226 is fitted into the receiving hole 224 by the spring 228 and the rotor 204 and the housing member 205 are connected with each other. Thereby, the vanes are prevented from colliding with the housing member 205 by the variation of torque acting on the cam shaft 200 and the generation of the noise is prevented. When the pressure of the fluid discharged from the oil pump becomes sufficiently high and current is supplied to the solenoid 219, pressurized fluid is supplied to the second chambers 208b and simultaneously to the receiving hole 224. Thereby, the locking pin 226 is pushed out from the receiving hole 225 against the urging force of the spring 228 as shown in Fig. 6 and relative rotation between the housing member 205 and the rotor 204 is allowed. Then, when the current supply to the solenoid 219d is stopped, the pressurized fluid is supplied to the first chambers 208a and thereby the rotor 204 begins to rotate clockwise relative to the housing member 205 as shown in Fig. 7. Then, the rotor 204 is rotated clockwise relative to the housing member 205 towards the maximum advanced condition in which the vanes 209 contact with the opposed walls 205b2, respectively and in which the angular phase of the cam shaft 200 is advanced relative to that of the crank shaft 203 by maximum value. In this condition, when the pressurized fluid is supplied from the pump 220 to the second pressure chambers 208b by the changeover valve 219, the rotor 204 is rotated counterclockwise relative to the housing member 205. Thereby, the valve timing control mechanism moves towards the position of the maximum retarded condition in which the vanes 209 is contacted with the walls 205b1 and in which the angular phase of the cam shaft 200 is retarded relative to that of the crank shaft 203 by maximum value from the above mentioned maximum advanced condition. At this time, although the receiving hole 224 is aligned with the cancelling hole 225, since the pressurized fluid is supplied to the receiving hole 224, it is prevented the locking pin 226 from fitting into the receiving hole 224 by a damping effect due to the pressurized oil supplied to the receiving hole 224. Now, depending on the manner in which the control of the changeover valve 220 is executed, the vanes 209 can be stopped in any position (intermediate advanced position) between the maximum advanced position and the maximum retarded position. This requires that balance be achieved between the fluid pressure of the first pressure chambers 208a and the fluid pressure of the second pressure chambers 208b when the vanes 209 have achieved an arbitrary position. The amount of the advance can therefore be set to any value between a zero level and a maximum level. As mentioned above, the opening and closing timing of the valves (not shown) driven by the cam shaft 200 is adjusted and the angular phase difference between the crank shaft 203 and the cam shaft 200 is adjusted. According to the second embodiment, since the damping effect due to the pressurized fluid supplied to the receiving hole before the receiving hole is aligned with the cancelling hole is obtained, the number of the operation of the locking pin 226 is remarkably reduced and thereby the durability and the reliability of the locking mechanism 223 is remarkably improved. Fig. 8 shows a third embodiment of the present invention. In Fig. 8, the same parts as compared with Fig. 5 to Fig. 7 are identified by the same reference numerals. Referring to Fig. 8, an orifice 229a is formed in the radial passage 229. According to this embodiment, it is able to surely store the supplied pressurized fluid in the receiving hole 224. Accordingly, it is able to surely obtain the same effect of the above second embodiment. Fig. 9a to Fig. 9c show a fourth embodiment of the present invention. In Fig. 9a to Fig. 9c, the same parts as compared with Fig. 5 to Fig. 7 are identified by the same reference numerals. Referring to Fig. 9a to 9c, a small diameter portion is formed on the bottom of the receiving hole 224 and is communicated to the radial passage 229. A checking ball 230 which can close the opening end of the radial passage 229 is disposed in the small diameter portion and a retainer 231 is fixed to the opening end of the small diameter portion. According to this embodiment, since the damping effect due to the pressurized fluid supplied to the receiving hole 224 before the receiving hole 224 is aligned with the cancelling hole 225 is obtained, it is able to prevent the locking pin from fitting into the receiving hole 224. Fig. 9a shows a maximum retarded condition. In this condition, the pressurized fluid is filled into the receiving hole 224. When the pressure in the second chambers 208b is released and the pressurized fluid begins to supply to the first chambers 208a as shown in Fig. 9b, the checking ball 230 closes the opening end of the radial passages 229 and thereby the damping effect is obtained. Therefore, as shown in Fig. 9c, the rotor 204 is smoothly rotated relative to the housing member 205. According to this embodiment, it is able to surely obtain the same effect of the second embodiment. In the above mentioned first to fourth embodiments, the locking mechanism connects the rotor with the housing member when the valve timing control device is in the maximum retarded condition. However, it is able to connect the rotor with the housing member when the valve timing control device is in the maximum advanced condition. In this case, a spring whose biasing force is smaller than the force due to the pressure in the chamber is disposed between the rotor and the housing member so that the valve timing control device is shifted to the maximum advanced condition by the spring when the pressure in the chamber decreases.

Claims: A valve timing control device (30) for an engine comprising: a rotor (68;204) fixed on a cam shaft (34;200), a housing (50;205) rotatably mounted on the cam shaft (34;200) so as to surround the rotor (68;204), a chamber (60;208) between the housing (50;205) and the rotor (68;204) having a pair of circumferentially opposed walls (50b1,50b2;205b2,205b1), a vane (74;209) mounted on the rotor (68;208) and extending outwardly therefrom in the radial direction into the chamber (60;208) to divide the chamber (60;208) into a first pressure chamber (80;208a) and a second pressure chamber (82;208b), supply means (92,98,94;219,220,221) for supplying fluid under pressure to at least a selected one of the first pressure chamber (80;208a) and the second pressure chamber (82;208b), and locking means (104;223) for connecting the housing (50;205) and the rotor (68;204), the locking means (104;223) comprising a pair of radially aligned holes (62,112;225;224) in the housing (50;205) and the rotor (68;204) respectively, and a locking pin (106:226) slidably received in one of the holes (62;225) but biased by a spring (108;228) to extend from that hole (62;225) into the other of the holes (112:224) cancelling means (84c,68c,114;229) supplied with fluid under pressure from the fluid supply means (92,98,94;219,220,221) for overcoming the bias of the spring (108;228) thereby cancelling the locking means (104;223) characterized by said fluid under pressure keeping the locking means (104;223) cancelled while the engine is in operation. A device according to claim 1, wherein the fluid supply means (92,98,94;219,220,221) includes a first passage means (68a,84a,84,84b;211,213,214,216,223) for supplying fluid under pressure to the first pressure chamber (80;208b), and a second fluid passage means (68b,86,90;210,212,215,217,224) for supplying fluid under pressure to the second pressure chamber (82;208b). A device according to claim 2, wherein the cancelling means (84c,68c,114;229) comprises a third passage means (84c,64;229) in fluid communication with the other of the holes (112;224), the third passage means (84c,68,114;229) being supplied with fluid under pressure from one of the first and second passage means to overcome the bias of the spring (108;228). A device according to claim 3, wherein the locking means (84c,68c,114) further comprises a forth passage means (114) in fluid communication with that pressure chamber (80;82) which is supplied with fluid under pressure from the other of the first and second passage means. A device according to claim 4, wherein the locking pin (106) has a small diameter portion (66) and a large diameter portion (111), the small diameter portion (66) extendible from said one of the holes (62) to engage the other hole (112), the third passage means (84c,64) and the fourth passage means (114) supplying fluid under pressure to the small diameter portion and the large diameter portion respectively. A device according to claim 3, wherein the third passage means (229) includes an orifice (229a) A device according to claim 3, wherein the third passage means (229) includes a checking ball (230).

Inventors: AOKI KONGO, EGUCHI KATSUHIKO, KIRA NAOKI, NAKADOUZONO HIROYUKI, OGAWA KAZUMI, AOKI, KONGO, EGUCHI, KATSUHIKO, KIRA, NAOKI, NAKADOUZONO, HIROYUKI, OGAWA, KAZUMI
Applicants: AISIN SEIKI, AISIN SEIKI KABUSHIKI KAISHA
Application year: 1997
Main classification: F01L1
IPC codes: F01L1