Variable valve timing device

Abstract: A variable valve timing device according to the invention includes a rotation shaft and a rotation transmitting member rotatably mounted thereon. The device takes a locked condition and an unlocked condition when a locking pin (60) is inserted into and disengaged from a receiving bore (32) formed in the rotation shaft, respectively. To disengage the pin (60) from the receiving bore (32), a fluid is supplied to the base of the receiving bore (32) from an independent fluid passage (13).

Description: Field of the Invention The present invention relates to a variable valve timing device for controlling the opening and closing of intake or exhaust valves of an internal combustion engine. Background of the Invention One of the conventional variable valve timing devices is disclosed in Japanese Utility Model Laid-open Print No.2-50105 which was published in 1990 without examination. This variable valve timing device includes a rotation shaft for opening and closing a valve; a rotation transmitting member rotatably mounted on the rotation shaft; a vane connected to the rotation shaft; an operating chamber defined between the rotational shaft and the rotational transmitting member and divided into an advancing angle space and a delaying angle space by the vane extended into the operating chamber; a first passage being in fluid communication with the advance angle space for supplying and draining a fluid therein and therefrom, respectively; a second passage being in fluid communication with the delay angle space for supplying and draining the fluid therein and therefrom, respectively; a retracting bore formed in the rotation transmitting member; a spring-biased locking pin fitted in the retracting bore; a receiving bore formed in the rotation shaft and having a bottom expected to receive the locking pin when the receiving bore is brought into alignment with the retracting bore when the rotation shaft and the rotation transmitting member are in phase; and a third fluid serving for supplying an oil to the receiving bore and being in continual fluid connection to the first fluid passage. In the conventional variable valve timing device, due to the continual fluid communication between the first fluid passage and the third fluid passage, when an oil supply to the advancing angle space from the first fluid passage is established in concurrency with an oil drain from the delaying angle space into the second fluid passage, the receiving bore is supplied with the oil from the first fluid passage via the third fluid passage. Due to the resultant oil supply, the locking pin is brought into retraction into the retracting bore and the head portion of the locking pin becomes out of engagement with the receiving bore. Thus, the locking condition between the rotation shaft and rotation transmitting member which is established by the locking pin is released with the result that the rotation shaft rotates toward an advancing angle direction relative to the rotation transmitting member. If an oil supply to the delaying angle space from the second fluid passage and an oil drain from the advancing angle space into the first fluid passage are established concurrently, contrary to the above, the rotation shaft rotates toward a delaying angle position relative to the rotation transmitting member. In addition, an oil drain is established from the receiving bore into the third and the first fluid passages and under the resultant condition wherein no oil pressure is applied to the spring-biased locking pin the locking pin is brought into engagement with the receiving bore when the inner rotor and the outer rotor are in-phase with each other. Thus, the rotation of the inner rotor relative to the outer rotor is prevented. However, in the foregoing or conventional variable valve timing device, whenever the device is in operation the locking pin is brought into engagement with or disengagement from the receiving bore. In light of such repetition of the locking and unlocking movements of the locking pin, preventing damages of the locking pin, the locking pin has to be made of a relatively high cost material. In addition, under the condition of continual fluid communication between the first fluid passage and the third fluid passage, a relatively complex fluid pressure control is required for retracting the locking pin from the receiving bore in case when the locking pin is intermediately positioned between the most advancing angle position and the most delaying angle position. It is, therefore, one of the objectives of the present invention to provide a variable valve timing device which is free from the foregoing drawbacks. EP-A-799976 discloses a variable valve timing device comprising a rotational shaft for opening and closing valves; a rotation transmitting member rotatably mounted on the rotation shaft; a vane provided on either the rotation shaft or the rotation transmitting member; an operating chamber defined between the rotational shaft and the rotation transmitting member and divided into an advancing angle space and a delaying angle space by the vane which extends into the operating chamber; a first fluid passage in fluid communication with the advancing angle space for supplying and discharging fluid therein and therefrom, respectively; a second fluid passage in fluid communication with the delaying angle space for supplying and discharging fluid therein and therefrom, respectively; regulating means for allowing or preventing the relative rotation between the rotational shaft and the rotation transmitting member; and a third fluid passage for supplying fluid to the regulating means. The third fluid passage of EP-A-799976 remains open and pressurized for all axial positions of a spool valve controlling the pressure supply to the first and second fluid passages. Summary of the Invention A variable valve timing device according to the present invention has the features of claim 1. The Drawings The above and other objectives, features and advantages of the present invention will be more apparent and more readily appreciated from the following detailed description of preferred exemplary embodiments of the present invention, taken in connection with the accompanying drawings, in which: Fig. 1 is a cross-sectional view of a variable valve timing device according to an embodiment of the present invention; Fig. 2 is a cross-sectional view taken along line A-A in Fig. 1; Fig. 3 is a cross-section view taken along line B-B in Fig. 1; Fig. 4 is a cross-sectional view taken along line D-D in Fig. 3; Fig. 5 is a view similar to Fig. 4 but is different in that in the former a locking pin is retracted condition; Fig. 6 is a view similar to Fig. 5 but is different in that in the former a driven member is rotated through an angle relative to a rotation transmitting member in the clockwise direction; and Fig. 7 shows a condition according to a second embodiment of the present invention which corresponds to that shown in Fig. 1. Preferred embodiments of the present invention will be described hereinafter in detail with reference to the accompanying drawings. Referring first to Figs. 1 through 4 wherein a first embodiment of a variable valve timing device in accordance with the present invention is illustrated. The variable valve timing device includes a cam shaft 10, an inner rotor 30, and a plurality of angularly spaced vanes 50 which constitute a rotational shaft for opening and closing valves. The variable valve timing device also includes an outer rotor 40 mounted on the cam shaft 10 so as to be rotated relative thereto through a limited angle, a locking pin 60 and a timing pulley 70 which constitute a rotation transmitting member. A cylinder head 81 of an internal combustion engine (not shown) rotatably holds the cam shaft 10 via a bearing 80 which is fixed to the cylinder head 81, whereby the variable valve timing device is rotatably mounted to the cylinder head 81. The timing pulley 70 is rotated in the clockwise direction in Fig. 1 by a force applied from a crank pulley via a timing belt (neither is shown). The cam shaft 10 has a cam 200 which serves for opening and closing an intake valve 210 (or an exhaust valve which is not depicted) and within the cam shaft 10 there are formed an advancing angle passage 11, a delay passage 12, and a pilot passage 13 which are extended along an axial direction of the cam shaft 10. The advancing angle passage 11 is connected to a port 101 of a first change-over valve 100 via an annular passage 91 which is formed in an inner surface of the bearing 80 and a connecting passage 92. The delay passage 12 is connected to a port 102 of the first change-over valve 100 via an annular passage 93 which is formed in the inner surface of the bearing 80 and a connecting passage 94. The pilot passage 13 is connected to a connecting port 111 of a second change-over valve 110. The first change-over valve 100 is under the control of a controller (not shown ) which is in the form of a micro-processor. The first change-over valve 100 is expected to operate such that if a delay of the phase angle is required, as shown in Figs. 2 and 3, the connecting port 102 connected to a supply port 103 is connected to an oil pump 120 driven by the internal combustion engine while the connecting port 101 is connected to a drain port 104 connected to a reservoir 130. When the variable valve timing device takes an advancing angle condition, the first change-over valve 100 is switched so as to connect the supply port 103 and the connecting port 102 to the connecting port 101 and the draining port 104, respectively. Thus, under the advancing angle condition, an oil supply is established from the oil pump 120 to the advancing angle passage 11 and an oil drain is established from the delaying angle passage 12 to the reservoir 130. To the contrary, under the delaying angle condition, the oil is supplied from the oil pump 120 to the delaying angle passage 12 and the oil is drained from the advancing angle passage 11 to the reservoir 130. The second change-over valve 110 is operated in a manner similar to the first change-over valve 100 and is expected to take either a supply condition as shown in Figs. 2 and 3 or a drain condition. Under the supply condition, the connecting port 111 of the second change-over valve 110 is connected to the oil pump 120 via a supply port 112 and is isolated from drain port 113. On the other hand, under the drain condition, the connecting port 111 of the second change-over valve 110 is isolated from the supplying port 112 and is connected to the drain port 113. Thus, under the supply and the drain conditions, oil is supplied to and is drained from the pilot passage 13 respectively. The inner rotor 30 is fixedly secured to a left end portion of the cam shaft 10 by means of a bolt 19. It is provided with grooves 31 in the radial direction so as to receive therein vanes 50. The inner rotor 30 includes a receiving bore 32 which receives the head portion of a locking pin 60 under the condition shown in Figs. 1 through 4 in which the rotational shaft is in the maximum timing delay condition relative to the rotating transmitting member. The inner rotor 30 further has a connecting passage 33 for establishing a fluid communication between a bottom of the receiving bore 32 and the pilot passage 13, a connecting passage 34 for establishing a fluid communication between the advancing angle passage 11 and each of advancing angle chambers R1 which will be detailed later, an annular passage 35 (cf. Fig. 1), a radial passage 36 (cf. Fig. 1), and a connecting passage 37 (cf. Fig. 2) for establishing a fluid communication between the delaying angle passage 12 and each of delaying angle chambers R2 which will be detailed later. It is to be noted that each vane 50 is urged outwardly by a spring (not shown) accommodated in each corresponding groove 31. The outer rotor 40 is mounted on the outer periphery of the inner rotor 30 so as to have a limited rotational range relative thereto. Plates 41 and 42 are secured to either side of the outer rotor 40, respectively, by means of a bolt 43. The timing pulley 70 which is adjacent to the plate 42 is secured thereto by means of a bolt 44 which passes through the plate 41, the inner rotor 30, the plate 42 and the timing pulley 70. Thus, the outer rotor 40, both plates 41,42 and the timing pulley 70 are fixed relative to each other. The rotor 40 is provided with a retraction bore 46 and five concave portions 45 disposed along the inner circumference thereof. The vane 50 extends into the concave portion 45 which defines therein an operating chamber R0, resulting in that the operating chamber R0 is divided into advancing angle chamber R1 and delaying angle chamber R2 which are located at the counter-clockwise side and the clockwise side thereof, respectively. The retraction bore 46 accommodates the locking pin 60 and a spring 61 which urges the locking pin 60 toward the inner rotor 30. The retraction bore 46 is concentric with a diameter of a cross-section of the inner rotor 30. The locking pin 60, when fully accommodated in the retraction bore 46, permits the outer surface of the inner rotor 30 to rotate relative thereto. The spring 60 is a compressed spring which is disposed between the locking pin 60 and a retainer 62 secured to an outer side of the retraction bore 46. The removal or extraction of the retainer 62 is prevented by a clip 63 which is secured to the outer rotor 40. The variable valve timing device as constructed above operates as follows from an initial condition where the locking pin 60 is fitted into the receiving bore 32 and the volume within the advancing angle chamber R1 is at a minimum. Oil under pressure is supplied to the receiving bore 32 from the oil pump 120 via the second change-over valve 110 and the pilot passage 13, as indicated in Fig. 5. The resultant oil pressure urges the locking pin 60 outwardly against the force of the spring 61, which results in the disengagement of the locking pin 60 from the receiving bore 32. Thus permitting clockwise movements of the rotation side members such as the cam shaft 10, the inner rotor 30 and the vanes 50 relative to the rotation transmitting members such as the outer rotor 40 and the timing pulley 70. If the first change-over valve 100 is switched to the advancing angle position while the variable valve timing device is in the most delayed angle condition as shown in Fig. 5 under which the volume of the advancing angle chamber R1 is at a minimum and the locking pin 60 is in the released or unlocked position, oil is supplied from the oil pump 120 to the advancing angle chamber R1 via the change-over valve 100 and the advancing angle chamber 11, and oil is drained from the delaying angle chamber R2 to the reservoir 130. Then, the rotation shaft side members such as the cam shaft 10, the inner rotor 30 and the vanes 50 are rotated relative to the rotation transmitting member such as the outer rotor 40 and the timing pulley 70 in the clockwise direction in Fig. 5. At full advancement, the volume of the delaying angle chamber R2 is at a minimum as shown in Fig. 6. It is to be noted that under the resultant condition as shown in Fig. 6 the receiving bore 32 is isolated from the retraction bore 46, which leads to a leakage of the oil from the retraction bore 46 through a gap between the inner rotor 30 and the outer rotor 40. Thus, the locking piston 60 which is urged by the spring 61 is brought into sliding contact with the outer surface of the inner rotor 40. If the first change-over valve 100 is switched to the delaying angle position while the valve timing device is in its fully advanced condition as shown in Fig. 6, oil is supplied to the delaying angle chamber R2 from the oil reservoir 120 via the change-over valve 100 and the delaying angle passage 12, and oil in the advancing angle chamber R1 is drained therefrom to the reservoir 130. Then, the rotation side members such as the cam shaft 10, the inner rotor 30 and the vanes 50 are rotated relative to the rotation transmitting members such as the outer rotor 40 and the timing pulley 70 in the counter-clockwise direction in Fig. 6, and the fully delayed condition as shown in Fig. 5 is established. It is to be noted that during the transfer from the most fully advanced condition shown in Fig. 6 to the fully delayed condition shown in Fig. 5, the receiving bore 32 comes into fluid communication with the retracting bore 46 and thus oil supplied to the receiving bore 32 through the pilot passage 13 begins to urge the locking pin 60 in the outward direction against the biasing force of the spring 61. This means that the locking pin 60 is held within the retraction bore 46, so that the locking pin 60 is out of contact with the outer surface of the inner rotor 30. In the foregoing structure, the oil supply to and the oil drain from the pilot passage 13 is established by the second change-over valve 110 which is independent of the oil supply from the oil pump 120 to either the advancing angle passage 11 or the delaying angle passage 12, and the concurrent oil drain to the reservoir 13 from either of the passages 11,12. Thus, for example, whenever the internal combustion engine is in operation and except for a time duration immediately after the initiation in which the rotation is unstable, oil can be supplied in stable and continual manner to the receiving bore 32 via the pilot passage 13, and during the time duration subsequent to the initiation of the internal combustion engine and upon termination thereof, the oil can be drained from the receiving bore 32 to the reservoir 130. Thus, while the internal combustion is in rotation except for the foregoing time duration subsequent to the initiation of the internal combustion engine, the head portion of the locking pin 60 is retracted into the retraction bore 46 after disengagement from the receiving bore 32 and locking pin 64 can remain in the unlocked condition. In addition, during the time duration subsequent to the initiation of the internal combustion engine and upon termination thereof, the head portion of the locking pin 60 is inserted into the receiving bore 32 establishing a locked condition. It can be appreciated that in permitting the locking mechanism to operate only when a time duration immediately after the initiation of the engine has expired and when the engine terminates, respectively, there is a reduction in the frequency of insertion and retraction movements of the locking pin 60 into and from, respectively, the receiving bore 32, thereby ensuring smooth and reliable locking and unlocking and remarkably increased durability of the locking pin 60 and its related elements. Referring to Fig. 7 in which a second embodiment of a variable valve timing device according to the present invention is depicted. In this structure, a groove 47 is formed in the inner surface of the outer rotor 40 so as to extend in the circumferential direction. The passage 47 serves for establishing a continual fluid communication between the retracting bore 46 and the receiving bore 32. Thus, regardless of the relative phase angle between the rotation side members such as the cam shaft 10, the inner rotor 30 and the vanes 50 and the rotation transmitting members such as outer rotor 40 and the timing pulley 70, the groove 47 enables a continuous oil supply from the receiving bore 32 to the retracting bore 46, thereby retaining the locking pin 60 in the retracting bore 46. Thus, it is possible to avoid sliding contact of the locking pin 60 against the outer surface of the inner rotor 30 during relative rotation, which would otherwise occur as described previously. This will help to further reduce nose generation. Instead of the foregoing structure constructed such that the vanes 50 are provided in the inner rotor 30 and the locking pin 60 and the spring 61 are provided in the outer rotor 40, the vanes 50 can be provided in the outer rotor 40 and the locking pin 60 and the spring 61 can be provided in the inner rotor 30.

Claims: A variable valve timing device comprising: a rotational shaft for opening and closing valves; a rotation transmitting member rotatably mounted on the rotational shaft; a vane provided on either the rotational shaft or the rotation transmitting member; an operating chamber (R0) defined between the rotational shaft and the rotation transmitting member and divided into an advancing angle space (R1) and a delaying angle space (R2) by the vane (50) which extends into the operating chamber (R0); a first fluid passage (11) in fluid communication with the advancing angle space (R1) for supplying and discharging fluid therein and therefrom, respectively; a second fluid passage (12) in fluid communication with the delaying angle space (R2) for supplying and discharging fluid therein and therefrom, respectively; regulating means for allowing or preventing the relative rotation between the rotational shaft and the rotation transmitting member; and a third fluid passage (13) for supplying fluid to the regulating means: CHARACTERIZED IN THAT Fluid supply and discharge to and from the first and second fluid passages (11;12) is controlled by a change-over valve (100), while supply and discharge of fluid to and from the third fluid passage (13) is controlled by a further changeover valve (110) independent of said change-over valve (100). A variable valve timing device according to claim 1, wherein the regulating means includes: a retraction bore (46) formed in one of the rotational shaft and the rotation transmitting member, a spring-biased locking pin (60) fitted into the retraction bore (46), and a receiving bore (32) formed on the other of the rotational shaft and the rotation transmitting member; whereby on alignment of the receiving bore (32) with the retraction bore (46), the spring-biased locking pin (60) is capable of engaging the receiving bore (32) thereby preventing relative rotation of the rotational shaft with respect to the rotation transmitting member, and the receiving bore (32) is supplied with fluid from the third fluid passage (13), the pressure of which tends to urge the spring-biased locking pin (60) into the retraction bore (46). A variable valve timing device according to claim 2, wherein a groove (47) is provided on either the inner surface of the rotation transmitting member or on the outer surface of the rotational shaft in order to establish continuous fluid communication between the retraction bore (46) and the receiving bore (32). A variable valve timing device according to any preceding claim, wherein for a time duration subsequent to initiation, the further change-over valve (110) is maintained in the condition enabling the discharge of fluid from the regulating means, thereby causing the regulating means to prevent relative rotation of the rotational shaft and the rotation transmitting member. A variable valve timing device according to claim 4, wherein the further change-over valve (110) changes condition after a time duration subsequent to initiation, so as to enable the supply of fluid to the regulating means, thereby causing the regulating means to permit relative rotation of the rotational shaft and the rotation transmitting member. A variable valve timing device according to claim 4 or claim 5, wherein upon termination, the further change-over valve (110) reverts to the condition enabling the discharge of fluid from the regulating means through the third fluid passage (13).

Inventors: FUJIWAKI KENJI, FUJIWAKI, KENJI
Applicants: AISIN SEIKI, AISIN SEIKI KABUSHIKI KAISHA
Application year: 1998
Main classification: F01L1
IPC codes: F01L1, F01L13