Valve timing control devices

Abstract: A valve timing control device (30) has a rotor (64) fixed on a cam shaft (34) of an engine and a housing (50) rotatably mounted on the cam shaft (34). The housing (50) surrounds the rotor (34). A chamber (60) between the housing (50) and the rotor (64) has a pair of circumferentially opposed walls (60a,60b). A vane (68) is mounted on the rotor (64) and extends outwardly therefrom in the radial direction into the chamber (60) so as to divide the chamber (60) into a first pressure chamber (76) and a second pressure chamber (78). A plate spring (74) between the rotor (64) and the vane (68) and a fluid supply means (91) supplies at least a selected one of the first pressure chamber (76) and the second pressure chamber (78).

Description: Technical Field The invention relates to valve timing control devices for controlling the angular phase difference between a crank shaft and a cam shaft of a combustion engine. In general, valve timing in an internal combustion engine is determined by mechanism driven by cam shafts in accordance with either a characteristic or a specification of the internal combustion engine. As the condition of the combustion changes in response to the rotational speed of the engine, it is difficult to obtain optimum valve timing through the whole rotational range. Therefore, valve timing control devices which change the timing in response to the condition of the combustion are desirable. Background Art US 4,858,572 discloses a rotor fixed on a cam shaft, and a drive member rotatably mounted on the cam shaft surrounding the rotor. The drive member is driven by the rotational torque provided by a crank shaft. Chambers are provided between the drive member and the rotor and each of the chambers has a pair of circumferentially opposed walls. Vanes are mounted onto the rotor and extend outwardly in a radial direction into the chambers to divide each into a first pressure chamber and a second pressure chamber. Coil springs are located between the vanes and the rotor and extend outwardly in the radial direction. Fluid under pressure is supplied to a selected one of the first pressure chamber and the second pressure chamber in response to the running condition of the internal combustion engine and an angular phase difference between the crank shaft and the cam shaft is controlled so as to advance or retard the valve timing relative to the crank shaft. The fluid under pressure is supplied by an oil pump. The device is in the maximum advanced condition when the vanes contact one of the opposed walls of the chambers. The device is in the maximum retarded condition when the vanes contact the other opposed walls of the chambers. In the above device, the drive member is cylindrical. The rotor which is cylindrical is inside the drive member. The coil springs are located in holes in the vane. The hole is the inside end of the vane and extends inwardly therefrom. The length of the coil spring is longer than the length of the hole so that the coil spring pushes the vane towards the drive member. When assembling the valve timing control device, first the rotor is fixed to the cam shaft, second the coil springs are inserted into the hole of the vane, third the vanes are fitted against the power of the coil springs, and then the rotor with the vanes is inserted into the drive member. In these steps, however, the rotor has to be inserted into the drive member very slowly and carefully in order to avoid twisting the coil springs. In EP 0323275, the use of conventional leaf springs has been suggested for initially biasing the vanes until sufficient oil pressure has been developed by the engine after which the oil pressure is used to bias the vanes. The provision of oil passages to the base of each vane complicates manufacture and operation as well as increasing expense. THE INVENTION In accordance with the invention, a valve timing control device is provided comprising a rotor for fixing on a cam shaft of an engine, a housing rotatably mounted on the cam shaft and surrounding the rotor, a chamber between the housing and the rotor and having a pair of circumferentially opposed walls, a vane mounted on the rotor and extending outwardly therefrom in the radial direction into the chamber so as to divide the chamber into a first pressure chamber and a second pressure chamber, a plate spring disposed between the rotor and the vane for urging the vane radially outwardly, and a fluid supply means for supplying at least a selected one of the first pressure chamber and the second pressure chamber, CHARACTERIZED IN THAT the spring has a pair of mutually spaced-apart bent-over portions. The bent-over portions are formed by bending the leaf spring or a portion of the leaf spring back on itself as generally shown in the drawings and as described below. With this arrangement, the device is easier to assemble. DRAWINGS FIG. 1 is a section through a valve timing control device applied to a double overhead cam shaft engine as taught by the prior art; FIG. 2 is a section along the line II-II in FIG. 1; FIG. 3 is a section on an enlarged scale, of a portion of the plate spring in FIG. 1; FIG. 4 is an enlarged section of a portion of a modified plate spring in accordance with the present invention; FIG. 5 is a detail of another modified plate spring according to the invention; FIG. 6 is an enlarged section of yet another modified plate spring according to the invention; and FIG. 7 and FIG. 8 are detailed views of yet another modified plate spring according to the invention. FIGs. 1 to 3 show a valve timing control device applied to an engine of DOHC (Double Over Head Cam Shaft) type. Referring to FIG. 1, an exhaust cam shaft 34 and an intake cam shaft 36 are rotatably mounted on a cylinder head 32 of an engine and are connected each other by gears 38 and 40. The gear 38 is rotatably mounted on the exhaust cam shaft 34 and the gear 40 is rotatably mounted on the intake cam shaft 36. An end of the exhaust cam shaft 34 projects out of the cylinder head 32 and a timing pulley 42 is fixed to the 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 41 from a crank shaft 43 which is rotated by the engine. A cylindrical portion 45 of the exhaust cam shaft 34 extends into the cylinder head 32 and is provided with a male screw portion 47 on which a male screw is formed. A journal portion 49 has a larger diameter than that of the cylindrical portion 45. On the journal portion 49, the gear 38 which has three female screw holes which are penetrated in the circumferential direction at regular intervals is rotatably mounted thereon. On the cylindrical portion 45 of the exhaust cam shaft 34, a valve timing control mechanism 30 is mounted thereon. As shown in FIGs. 1 and 2, the valve timing control mechanism 30 includes a rotor 64, five vanes 68, a housing member 50, a circular front plate 48 and a circular rear plate 52. The rotor 64 is a cylindrical shape and is fixedly mounted on the cylindrical portion 45 of the exhaust cam shaft 34. The housing member 50 is a cylindrical shape with an inner bore 50a and is rotatably mounted on the outer circumferential surface of the rotor 64 so as to surround the rotor 64. The housing member 50 has the same axial length as the rotor 64 and is provided with five grooves 60 which outwardly extend from the inner bore 50a in the radial direction and are separated in the circumferential direction at regular intervals. The housing member 50 is also provided with three holes which are penetrated in the axial direction and are separated in the circumferential direction at the regular intervals. The rear plate 52 is rotatably mounted on the journal portion 49 and is located between the gear 38 and one side faces of the housing member 50 and the rotor 64. The rear plate 52 is provided with three holes which are penetrated in the axial direction and are separated in the circumferential direction at the regular intervals. The front plate 48 is located to be opposite to the other side faces of the housing member 50 and the rotor 64. The front plate 48 is provided with three holes which are penetrated in the axial direction and are separated in the circumferential direction at regular intervals. Three bolts 54 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. The front plate 48 is fluid-tightly pressed onto one side face of the housing member 50 and the rear plate 52 is fluid-tightly pressed onto the other side face of the housing member 50. One side face of the rotor 64 is contacted with a stepped portion 49a of the journal portion 49 and under this condition a nut 65 is screwed onto the male screw portion 47 of the exhaust cam shaft 34 so as to press the rotor 64 toward the journal portion 49. Thereby, the rotor 64 is fixed with the exhaust cam shaft 34 in a body. Five chambers 60 which are separated in the circumferential direction at regular intervals and each of which has a pair of circumferentially opposed walls 60a, 60b are defined among the rotor 64, the housing member 50, the front plate 48 and the rear plate 52. On the outer circumferential portion of the rotor 64, five grooves 70 which extend inwardly therefrom into the radial direction and are separated in the circumferential direction at regular intervals are formed thereon. The five vanes 68 which extend outwardly in the radial direction into the chambers 60 are mounted in the grooves 70, respectively. Thereby, each of chambers 60 is divided into a first pressure chamber 76 and a second pressure chamber 78, both are fluid-tightly separated from each other. As shown in FIG. 3, the inside surface of each of the vanes 68 has a groove 72 into which a plate spring 74 is inserted. The plate spring 74 includes a curved portion 74b at the center of the plate spring 74. Both ends 74a and 74c of the plate spring 74 are attached onto the vane 68 and the curved portion 74b of the plate spring 74 is attached onto the rotor 64. Thereby, the vanes 68 are pushed toward outwardly in the radial direction from the rotor 64. The housing member 50 has a hole 62 which extends inwardly thereof in the radial direction and is penetrated in the radial direction. The bottom end of the hole 62 has a small hole portion 63. The small hole portion 63 accommodates a pin 104 which is urged towards the rotor 64 by a coil spring 106. The pin 104 has a large diameter portion 104a engaged in the hole 62 and a small diameter portion 104b. The coil spring 106 is supported in the hole 62 by a clip 102. On the other hand, the rotor 30 on the outer circumferential surface has a hole 108 which extends inwardly thereof in the radial direction and into which the small diameter portion 104b of the pin 104 may be inserted. The rotor 64 is provided with six first passages 80 and five second passages 82. One end of each of the first passages 80 is communicated with either a first pressure chamber 76 or the hole 64. The other end of each of the first passages 80 is communicated with a main first passage 80a which is formed in the exhaust cam shaft 34 at its axial center. On the other hand, one end of each of the second passages 82 is communicated with a second pressure chamber 78. The other end of each of the second passages 82 is communicated with a main second passage 82a which is formed in the exhaust cam shaft 34 to be located on the coaxial circle around the axial center of the exhaust cam shaft 34. The main second passage 82a extends in parallel with the main first passage 80a in the axial direction. A fluid supplying device 91 is comprised of a changeover vale 90, a controller 92 and a fluid pump 96. The changeover valve 90 is an electromagnetic valve which is 4 ports - 3 positions type. The,fluid pump 96 is driven by the engine and discharges the fluid (oil) which may be used from lubricating the engine. The position of the changeover valve 90 is selectively controlled by the controller 92 so that in a first condition the valve 90 is at a position 90a in which the discharged fluid from the pump 96 is supplied to the main first passage 80a and in which the main second passage 82a is communicated with a reservoir 94, in a second condition the valve 90 is at a position 90b in which the communication between the main passages 80a, 82a and the pump 96 and the reservoir 94 are interrupted, respectively and in which the discharged fluid from the pump 96 is supplied to the reservoir 94, and in a third condition the valve 90 is at a position 90c in which the discharged fluid from the pump 96 is supplied to the second main passage 82a and in which the first main passage 80a is communicated to the reservoir 94. The controller 92 controls the above conditions of the changeover valve 90 based on parameter signals which may be an engine speed, an amount of opening of a throttle valve (not shown) and so on. The operation of the valve timing control device having the above structure will now be described. When the engine starts, the exhaust cam shaft 34 is rotated clockwise by the timing pulley 42 in FIG.1. Thereby, exhaust valves (not shown) are opened and closed. Simultaneously, the rotor 64 is rotated and the gear 38 is rotated via the vanes 68, the housing member 50 and the bolts 54. The rotation of the gear 38 is transmitted to the gear 40 and the intake cam shaft 36 is rotated so that intake valves (not shown) are opened and closed. The gear 38 is rotatably mounted on the journal portion 49 of the exhaust cam shaft 34. Therefore, when the pressurized fluid is supplied from the pump 96 to the second pressure chambers 78 by changing the changeover valve 90 into the third condition via the main second passage 82a and the second pressure passages 82, the housing member 50, the front plate 48 and the rear plate 52 are rotated in the clockwise direction with the gear 38 relative to the exhaust cam shaft 34 in FIG. 2. Thereby, the timing control mechanism 30 is in the position of the maximum advanced condition in which the valves 68 are contacted with the walls 60b of the chambers 60. The angular phase of the intake cam shaft 36 is advanced relative to that of the exhaust cam shaft 34 (the crank shaft 43) by maximum valve. At the same time, the small diameter portion 104b of the pin 104 is inserted into the hole 108 of the rotor by the coil spring 106 In this condition, when the pressurized fluid is supplied from the pump 96 to the first pressure chambers 76 by changing the changeover valve 90 into the first condition via the main first passage 80a and the first pressure passages 80, the pressurized fluid urges the pin 104 fully into the hole 52 of the housing member 50. The housing member 50, the front plate 48 and the rear plate 52 are rotated in the counterclockwise direction with the gear 38 relative to the exhaust cam shaft 34 in FIG. 2. Thereby, the timing control mechanism 30 is in the position of the maximum retarded condition in which the valves 68 are contacted with the walls 60a of the chambers 60. The angular phase of the intake cam'shaft 36 is retarded relative to that of the exhaust cam shaft 34 (the crank shaft 43) by maximum valve from the above mentioned maximum advanced condition. Depending on the manner in which the control of the changeover valve 90 is executed, the vanes 68 can be stopped in any position (intermediate advanced position) between the maximum advanced position and the maximum retarded position. This requires that the fluid pressure of the first pressure chambers 76 and the fluid pressure of the second pressure chambers 78 be balanced when the vanes 68 are in 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 43 and the intake cam shaft 34 is adjusted. In FIG. 4, the same parts as in Fig. 3 are indicated by the same numerals of FIG. 3. A plate spring 110, according to the invention includes two bent-over portions 112, 114 as shown in FIG. 5 so that each end 116, 118 of the plate spring 110 is attached onto the rotor 64 and the flat surface between the bent-over portions 112, 114 of the plate spring 110 is attached onto the vane 68. FIGs. 6 to 8 illustrate two other modified versions of the plate springs 120 and 130. In FIG. 6, the same parts as in FIG. 3 are indicated by the same numerals of FIG. 3. In this modified embodiment, the inside surface of each of the vanes 68 has a flat surface instead of the groove 72. The plate springs 120 (130) includes two bending portions 122, 126 (132, 136) producing two bent-over portions have the same bending direction as shown in FIG. 7 and FIG. 8. As shown in FIG. 7, the plate spring 120 includes the first bent-over portion 124 and the second bent-over portion 128. The first bent-over portion 124 is mounted on the second bent-over portion 128. The two ends 124a and 128a of the plate spring 120 are attached onto the rotor 64 and the flat surface of the plate spring 120 is attached onto the vane 68. As shown in FIG. 8, the plate spring 130 includes the first bent-over portion 134 and the second bent-over portion 138. The first bent-over portion 134 and the second bent-over portion 138 are located in parallel with each other. The two bent-over portions 134 and 138 are attached on the rotor 64 and the flat surface of the plate spring 130 is attached on the vane 68.

Claims: A valve timing control device (30) comprising: a rotor (64) for fixing on a cam shaft (34) of an engine; a housing (50) rotatably mounted on the cam shaft (34) and surrounding the rotor (64); a chamber (60) between the housing (50) and the rotor (64) and having a pair of circumferentially opposed walls (60a,60b); a vane (68) mounted on the rotor (64) and extending outwardly therefrom in the radial direction into the chamber (60) so as to divide the chamber into a first pressure chamber (76) and a second pressure chamber (78); a plate spring (110,120,130) disposed between the rotor (64) and the vane (68) for urging the vane radially outwardly; and a fluid supply means (91) for supplying at least a selected one of the first pressure chamber (76) and the second pressure chamber (78); CHARACTERIZED IN THAT the spring (110,120,130) has a pair of mutually spaced-apart bent-over portions (112,114;124,128; 134,138), A valve timing control device (30) according to claim 1, wherein the vane (68) has a groove (72) contacting the plate spring (110,12C,130). A valve timing control device (30) according to claim 1 or claim 2, wherein the plate spring (110) includes a curved portion between the bent-over portions. A valve timing control device (30) according to any preceding claim, wherein the bent-over portions (112,114) of the plate spring (110) face each other. A valve timing control device (30) according to any of claims 1 to 3, wherein the bent-over portions (124,128;134,138) of the plate spring (120,130) face in the direction of insertion of the plate spring (120,130). A valve timing control device (30) according to claim 5, wherein the plate spring (120) includes a first plate (122) which has a first bent-over portion (124) and a second plate (126) which has a second bent-over portion (128). A valve timing control device (30) according to claim 6, wherein the first plate (122) is mounted on the second plate (126). A valve timing control device (30) according to claim 5, wherein the bent-over portions (134,138) are parallel with each other. A valve timing control device (30) according to any preceding claim, wherein the bent-over portions (112,114;124,128;134,138) are bent towards the rotor (64).

Inventors: KIRA NAOKI, KIRA, NAOKI
Applicants: AISIN SEIKI, AISIN SEIKI KABUSHIKI KAISHA
Application year: 1997
Main classification: F01L1
IPC codes: F01L1