JP4400546B2 - Variable valve timing device for internal combustion engine - Google Patents

Description

  The present invention relates to a variable valve timing device that varies the valve timing of an intake valve and an exhaust valve of an internal combustion engine.

  Patent Document 1 discloses an example of a variable valve timing device that varies the valve timing of intake / exhaust valves (intake valves and exhaust valves) of an internal combustion engine. This device includes an outer rotor that rotates in conjunction with one of a camshaft and a crankshaft that drives intake and exhaust valves of an internal combustion engine, and is disposed concentrically on the inner side of the outer rotor. The valve timing of the intake / exhaust valves is changed by relatively rotating the inner rotor that rotates in conjunction with the inner rotor within a movable range from the most retarded angle position to the most advanced angle position.

The device also has a key groove recessed in the inner peripheral portion of the outer rotor and a lock key provided in the outer peripheral portion of the inner rotor so as to be movable in the radial direction. The lock key is provided in the key groove. An intermediate lock mechanism is provided for engaging the outer rotor and the inner rotor at a predetermined intermediate lock position suitable for starting the engine by fitting. Even when both rotors are not constrained to the intermediate lock position when the engine is stopped, the lock key fits into the keyway during cranking at the time of engine start, and the rotor is locked to an intermediate lock suitable for engine start. A stepped step portion higher than the bottom of the key groove is formed on the outer peripheral portion of the rotor so as to be shifted from the key groove toward the advance side so that the rotor is held in position. A taper is formed at the boundary portion.
Japanese Patent Laid-Open No. 2002-122009

  However, in the conventional lock mechanism as described above, from the position deviated from the intermediate lock position to the intermediate lock position is restored using the cam torque acting on the camshaft. In addition, when the viscosity of the oil is high and the friction is large, a high assist force by the cam torque is required, and there is a possibility that it cannot be quickly returned to the intermediate lock position. Specifically, the cam torque that acts on the camshaft when the engine is started is an alternating torque whose input direction is frequently reversed in a very short time. Therefore, as in the conventional example described above, when a step is provided in the vicinity of the keyway to assist the movement to the intermediate lock position, even if a positive cam torque acting toward the intermediate lock position acts, As long as you do not get over the part, the assist power will be wasted. For example, if the positive cam torque cannot get over the step, the negative cam torque may move away from the intermediate lock position again, and this is repeated, so that both rotors are relatively moved, especially during cold start. In a situation where it is difficult to move to the intermediate position, there is a possibility that it cannot be quickly moved to the intermediate lock position, and further improvement has been desired.

The present invention has been made in view of such problems.
That is, the variable valve timing apparatus for an internal combustion engine according to the present invention is disposed concentrically on the inner side of the outer rotor that rotates in conjunction with one of a camshaft and a crankshaft that drive intake and exhaust valves of the internal combustion engine. By rotating the camshaft and the inner rotor that rotates in conjunction with the other of the crankshaft within a movable range from the most retarded position to the most advanced position, the valve timing of the intake and exhaust valves Is variable.
A key groove recessed in one of the inner peripheral portion of the outer rotor and the outer peripheral portion of the inner rotor, and a lock key provided in a radially movable manner on the other of the inner peripheral portion of the outer rotor and the outer peripheral portion of the inner rotor. And having an intermediate lock mechanism that engages the outer rotor and the inner rotor at a predetermined intermediate lock position excluding the most retarded angle position and the most advanced angle position by fitting the lock key into the key groove.
Then, when the two rotors are relatively rotated toward the intermediate lock position, the front end surface of the lock key is circumferentially arranged so that an assist force for assisting the rotation in the rotation direction is generated. A key-side taper portion that is gradually inclined along the groove is provided, and a groove-side taper portion that is gradually inclined along the circumferential direction is provided on the bottom surface of the key groove with which the front end surface of the lock key is slidably contacted.

  According to the present invention, the key side taper portion and the groove side taper portion that are gradually inclined along the circumferential direction are provided on both the front end surface of the lock key and the bottom surface of the key groove that are in sliding contact with each other. Even in a situation where the two rotors are relatively difficult to move as at the time of starting, the movement to the intermediate lock position can be favorably assisted, and stable engine startability can be ensured.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing an example of a variable valve timing device for an internal combustion engine according to the present invention. This variable valve timing device is applied to the intake side of an internal combustion engine (engine) mounted on a vehicle, for example. Since the basic configuration and operation of this apparatus are known as disclosed in Japanese Patent Laid-Open No. 2003-247403, only a brief description will be given here. Note that FIG. 1 does not show the tapered portion and the assist mechanism, which are characteristic constituent features according to the present invention described with reference to FIGS.

  This variable valve timing device drives the intake and exhaust valves of an internal combustion engine to open and close, and variably controls the opening and closing timing, that is, the valve timing according to the engine operating state. As shown in FIG. And an outer rotor 2 fitted to the inner rotor 1 so as to be relatively rotatable. The inner rotor 1 is fixed to the tip of a camshaft rotatably supported by a cylinder block of the internal combustion engine, and rotates integrally with the camshaft 3. When the camshaft rotates together with the inner rotor 1, the intake / exhaust valves of the internal combustion engine are driven to open and close by a cam provided on the camshaft.

  The outer rotor 2 is coaxially disposed on the outer peripheral side of the inner rotor 1 so as to surround the inner rotor 1, and a timing sprocket 2A is provided on the outer periphery thereof. A transmission member such as a timing chain or a timing belt is wound around the timing sprocket 2A and the gear of the crankshaft of the internal combustion engine, and the outer rotor 2 rotates in conjunction with the crankshaft through this transmission member.

  Both rotors 1 and 2 basically rotate integrally, but the valve timings of the intake and exhaust valves are variably controlled by relatively rotating both rotors 1 and 2 according to the engine operating state. Can do. Specifically, a plurality of (four in this example) thick projections 4 functioning as shoes projecting in the radially inward direction are provided on the inner peripheral portion of the outer rotor 2. A plurality of fluid pressure chambers 40 arranged in parallel along the relative rotation direction (arrow S1, S2 direction) are recessed. On the other hand, a plurality of vane grooves 41 are radially formed on the outer peripheral portion of the inner rotor 1 at predetermined intervals so as to face the fluid pressure chambers 40. In each vane groove 41, a vane 5 that functions as a partition member is slidably inserted along a radial direction (radial direction). By the vanes 5, the fluid pressure chambers 40 are liquid-tightly defined into the retard chamber 42 and the advance chamber 43.

  The hydraulic pressure control unit 7 as fluid pressure control means includes a hydraulic pressure control valve 7 </ b> A that switches the hydraulic pressure to the retard chamber 42, the advance chamber 43, and the lock release hydraulic chamber 66. The hydraulic control valve 7A is connected to a hydraulic pump 7B that is rotationally driven by a crankshaft and a drain-side oil pan 7C. A command signal is output from the engine control unit 9 to the hydraulic control valve 7A according to the engine operating state, and the hydraulic pressure in the retard chamber 42 and the advance chamber 43 is switched and controlled by the hydraulic control valve 7A. Moves within the fluid pressure chamber 40 within a movable range from the most retarded phase (position) mechanically locked to the most advanced phase (position). The most retarded phase is, for example, a position where the vane 5 hits one end face 44r or the stopper of the protrusion 4, and is a phase in which the volume of the retard chamber 42 increases most. The most advanced angle phase is, for example, a position where the vane 5 abuts against the other end surface 44s or the stopper of the protrusion 4, and is a phase where the volume of the advance chamber 43 increases most.

  The most retarded angle position is, for example, a valve timing required on a relatively high rotation / high load side, and is set in consideration of a response delay of air at the time of high rotation. On the other hand, when starting the engine, depending on the qualities of the internal combustion engine, it may not be possible to obtain good startability due to a decrease in the actual compression ratio at the most retarded position.In such a case, the relative rotational phase position at the start of the engine Is set to an intermediate lock position that is advanced from the most retarded position. That is, the intermediate lock position is an intermediate position excluding the most retarded angle position and the most advanced angle position, which are mechanically locked both end positions, within the movable range of the relative rotational position of the outer rotor 2 and the inner rotor 1. In addition, functionally, the engine starting position is set so as to obtain a smooth startability of the internal combustion engine.

  Therefore, a lock mechanism is provided that mechanically holds the relative rotational phase of the outer rotor 2 and the inner rotor 1 at the intermediate lock position. The lock mechanism is recessed in the outer peripheral portion of the inner rotor 1 and is supported by the key groove 66 functioning also as the unlocking hydraulic chamber and the protrusion 4 of the inner rotor 1 so as to be movable in the radial direction. And a lock key 6 that engages and fits into the key groove 66 in a protruding posture. In this embodiment, the keyway 66 also serves as the unlocking hydraulic chamber. However, the present invention is not limited to this, and both may be formed separately. As the lock key 6 described above, each protrusion 4 has a pair of lock keys 6A and 6B, more specifically, a retard-side lock key 6A that prevents the inner rotor 1 from moving in the retard direction, and the inner rotor 1 is advanced. And an advance side lock key 6B for preventing movement in the direction. Further, on the back side of each lock key 6, a spring 61 that urges the lock key 6 in a radially inward direction that is a lock direction is disposed. For simplification, the spring 61 is not shown in FIGS. When the hydraulic pressure in the unlocking hydraulic chamber 66 is low and the relative rotational phase of the outer rotor 2 and the inner rotor 1 reaches a predetermined intermediate lock position, the lock key 6 moves inward in the radial direction, which is the locking direction, by the biasing force of the spring 61. By automatically moving and the leading end portion of the lock key 6 engaging with the key groove 66 on the lock hydraulic chamber side, the relative rotational phase of the outer rotor 2 and the inner rotor 1 is locked, and the outer rotor 2 and the inner rotor 1 are intermediately locked. Rotates integrally while maintaining the position.

  When the relative rotational phase of the outer rotor 2 and the inner rotor 1 is changed according to the driving conditions of the internal combustion engine, the lock by the retard lock key 6A and the advance lock key 6B is released. In this case, a predetermined hydraulic pressure is supplied to the unlocking hydraulic chamber 66, the pressure surface of the tip of the lock key 6 is pressurized by this hydraulic pressure, and the lock key 6 is moved radially outward to release the lock. When the lock key 6 is unlocked in this way, the outer rotor 2 and the inner rotor 1 can be rotated relative to each other, and the rotational phase of the camshaft 3 relative to the rotational phase of the crankshaft, that is, the outer rotor, according to the driving conditions of the internal combustion engine. The valve timing of the intake and exhaust valves can be adjusted by adjusting the rotational phase position of the inner rotor 1 with respect to 2 in the retard direction (arrow S1 direction) or the advance angle direction (arrow S2 direction).

  As shown in FIGS. 2 and 3, key-side taper portions 70 </ b> A and 70 </ b> B that are gradually inclined along the circumferential direction are provided over the entire front surface of the lock keys 6 </ b> A and 6 </ b> B. A groove-side taper portion 71 that is gradually inclined along the circumferential direction is provided on the bottom surface of the key groove 66 in which the tip surfaces of 6A and 6B are in sliding contact. In the first embodiment shown in FIGS. 2 and 3, the inclination directions of the key side taper portions 70A and 70B of the pair of lock keys 6A and 6B arranged close to each other are different from each other. Specifically, the key-side taper portion 70A of the advance side lock key 6A forms an inclined surface that inclines in the protruding direction (upward in FIGS. 2 and 3) toward the retard direction S1, and the retard side lock key 6B The key side taper portion 70B is an inclined surface that inclines in the protruding direction toward the advance direction S2.

  Further, the groove-side taper portion 71 has a substantially V-shaped cross section with a pair of inclined surfaces (71A, 71B) inclined convexly with the intermediate lock position as a vertex, that is, a pair of inclinations that are reversed from each other starting from the top portion. It has surfaces (71A, 71B). The groove side taper portion 71A closer to the advance side is inclined in the same direction as the key side taper portion 70A of the advance side lock key 6A facing at the intermediate lock position, and the groove side taper portion 71B closer to the retard side is The key-side taper portion 70B of the lock key 6B facing at the intermediate lock position is inclined in the same direction.

  In other words, in the first embodiment, the key-side taper portions 70A and 70B of the pair of lock keys 6A and 6B provided close to each other are inclined in the protruding direction toward the direction of approaching each other, and the groove-side taper is formed. The portions 71A and 71B have a shape recessed in a substantially V-shaped cross section having two inclined surfaces with which the pair of key side taper portions 70A and 70B are in sliding contact with each other.

  FIG. 3 shows a state where the inner rotor 1 is offset to the retard side S1 from the intermediate lock position shown in FIG. For example, when the engine is started, as shown in FIG. 3, when the inner rotor 1 is shifted from the intermediate lock position to the retard side, one key side taper portion 70 </ b> A and a groove side taper portion 71 </ b> A that inclines in the same direction are provided. Due to the sliding contact, the load in the advance direction F2, that is, the assist force F2 in the direction toward the intermediate lock position is applied due to the inclination of both. Although not shown in the figure, when the position is shifted to the advance side from the intermediate lock position, due to the inclination of the other key side taper portion 70B and the other groove side taper portion 71B inclined in the same direction, An assist force in a direction toward the intermediate lock position is applied. Therefore, it is easy to return to the intermediate lock position.

  As described above, in the first embodiment, the inclination directions of the pair of taper portions, that is, the assisting directions are opposite to each other, so that the intermediate lock position is shifted to either the retard side or the advance side. Even so, the assist force to the intermediate lock position will act. However, when the position to be avoided is specified as one of the retard side and the advance side with respect to the intermediate lock position and the direction to be assisted is specified as one, the second embodiment described later is used. Thus, what is necessary is just to set the inclination direction of a some taper part to the same direction.

  In the second embodiment shown in FIGS. 4 and 5, the advance-angle side lock key 6A and the retard-angle side lock key 6B are arranged relatively apart from each other as compared with the first embodiment. The surfaces are key-side taper portions 72A and 72B that are inclined over the entire surface in the protruding direction (upward direction in FIGS. 4 and 5) toward the retard side S1. The inner rotor 1 has key grooves 66A and 66B having the same shape corresponding to the lock keys 6A and 6B, respectively. Similar to the key side taper portions 72A and 72B, groove side taper portions 73A and 73B that are inclined toward the inner side of the inner rotor 1 toward the retard side S1 are formed on the bottom surfaces of the key grooves 66A and 66B. . Each of the key grooves 66A and 66B is provided with stopper portions 74A and 74B that face the side surfaces of the lock keys 6A and 6B so as to be in contact with the side surfaces of the lock keys 6A and 6B. The top part of 74B and the top part of said key side taper part 72A, 72B are connected by the substantially flat top surfaces 75A, 75B.

  FIG. 5 shows a state in which the inner rotor 1 is displaced to the retard side S1 from the intermediate lock position shown in FIG. As shown in FIG. 5, when starting the engine from a state in which the internal combustion engine is stopped due to displacement to the retard side S1 from the intermediate lock position for some reason, the key side taper portions 72A and 72B of the lock keys The groove side taper portions 73A and 73B that are inclined in the same direction are in sliding contact with each other, and due to the inclination of both, a load in the advance angle direction F2, that is, an assist force F2 in the direction of the intermediate lock position acts. . Therefore, it is easy to return to the intermediate lock position.

  The torque acting from the camshaft side when the engine is started is an alternating torque whose input direction is frequently reversed in a very short time. Therefore, as in the conventional example described above, when a step is provided in the vicinity of the keyway in order to assist the movement to the intermediate lock position, even if the cam torque in the positive direction toward the intermediate lock position acts, The assist power is wasted unless the step is overcome. For example, if it is not possible to get over the step by the positive cam torque, the rotor is moved away from the intermediate lock position by the subsequent negative cam torque, and the two rotors move relative to each other, particularly during cold start. In difficult situations, it cannot be quickly moved to the intermediate lock position.

  In contrast, in the first and second embodiments described above, both the key side taper portion and the groove side taper portion that are in sliding contact with each other are gradually inclined along the circumferential direction, so that the positive direction toward the intermediate lock position is achieved. When the cam torque is applied, movement toward the intermediate lock position is always assisted by the inclination described above. On the other hand, when the cam torque in the negative direction away from the intermediate lock position is applied, the inclination is determined by the inclination described above. Since the movement in the direction away from the head is always restrained and such an inclination is continuously formed, even if it is gradually, the head moves toward the intermediate lock position reliably and without waste. Therefore, it is possible to assist the movement to the intermediate lock position by effectively using the cam torque, which is an alternating torque, even in a situation where both rotors are relatively difficult to move as in cold start. Therefore, the engine can be quickly moved to the intermediate lock position to ensure stable engine startability.

  When the internal combustion engine is stopped at the most retarded position and the internal oil is full, it is more difficult to convert to the intermediate lock position when starting the engine due to the viscosity of the oil. In the meantime, the viscosity of the oil becomes extremely large. Therefore, in order to satisfactorily return to the intermediate lock position even in such a situation, the inner rotor 1 and the outer rotor 2 are forced and mechanically moved in the circumferential direction from the most retarded position to the intermediate lock position in the vicinity of the most retarded position. Assist means for energizing is provided.

  If only a metal torsion spring having a small change in spring constant due to temperature is used as this assist means, a good assist force can be obtained under operating conditions that require assist, such as during cold start. When switching to the most retarded position in the warm operation state, an unnecessary assist force to the intermediate lock position is excessively applied, which may cause a decrease in responsiveness and controllability.

  Therefore, for example, in the third embodiment shown in FIG. 6, an arc spring using rubber whose spring constant changes with temperature is used as the assist means. Specifically, an assist mechanism 80 that urges the vane 5 in the direction toward the intermediate lock position (left direction in FIG. 6) is provided in the vicinity of the retarded end face 44r of the fluid pressure chamber 40 of the outer rotor 2. The assist mechanism 80 has a rubber-like cylindrical compression rubber spring 81 and an auxiliary arc spring 82, and the tip of the auxiliary arc spring 82 has a remarkably large change in spring constant due to temperature as compared with a metal material. Further, a plate-like stopper portion 83 that can come into contact with the side surface of the vane 5 and the front end surface of the compression rubber spring 81 is provided.

  By adopting a material such as rubber that has a large change in spring constant due to temperature in this way, the spring load becomes sufficiently large at low temperatures, and the assist force toward the advance side toward the intermediate lock position becomes large. Sufficient assist force in the direction from the most retarded position to the intermediate lock position at the time of engine start is ensured, and the spring load is reduced during warm conditions, reducing unnecessary assist force in the vicinity of the most retarded position. It is eliminated and good responsiveness and controllability can be secured.

  The shape of the compression rubber spring is not limited to the cylindrical shape as shown in FIGS. 6 and 7A. For example, the compression rubber spring is a tapered compression rubber spring 81B having a substantially conical shape as shown in FIG. 7B. Alternatively, it may be a leaf spring shape.

1 is a cross-sectional view showing an example of a variable valve timing device for an internal combustion engine to which the present invention is applied. Sectional drawing in the intermediate | middle lock position which shows the intermediate | middle lock mechanism based on 1st Example of this invention. Sectional drawing in the position which deviated from the intermediate | middle lock position which shows the intermediate | middle lock mechanism which concerns on the said 1st Example to the retard angle side. Sectional drawing in the intermediate | middle lock position which shows the intermediate | middle lock mechanism based on 2nd Example of this invention. Sectional drawing in the position which shifted | deviated from the intermediate | middle locking position which shows the intermediate | middle locking mechanism which concerns on the said 2nd Example to the retard side. Sectional drawing which shows the assistance means which concerns on 3rd Example of this invention. Explanatory drawing which shows the example of a shape of the compression rubber spring of the said assist means.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Inner rotor 2 ... Outer rotor 4 ... Protruding part 5 ... Vane 6 ... Lock key 7 ... Hydraulic switching valve (hydraulic control means)
DESCRIPTION OF SYMBOLS 40 ... Fluid pressure chamber 42 ... Delay angle chamber 43 ... Advance angle chamber 66 ... Key groove 70A, 70B, 72A, 72B ... Key side taper part 71A, 71B, 73A, 73B ... Groove side taper part 80 ... Assist mechanism (assist means) )
81, 81B ... Compression rubber spring

Claims (3)

An outer rotor that rotates in conjunction with one of the camshaft and crankshaft that drives the intake and exhaust valves of the internal combustion engine, and is arranged concentrically inside the outer rotor, and rotates in conjunction with the other of the camshaft and crankshaft. In the variable valve timing device of the internal combustion engine that makes the valve timing of the intake and exhaust valves variable by relatively rotating within the movable range from the most retarded angle position to the most advanced angle position,
A key groove recessed in one of the inner peripheral portion of the outer rotor and the outer peripheral portion of the inner rotor, and a lock key provided in the other of the inner peripheral portion of the outer rotor and the outer peripheral portion of the inner rotor so as to be movable in the radial direction. And having an intermediate lock mechanism for engaging the outer rotor and the inner rotor at a predetermined intermediate lock position excluding the most retarded angle position and the most advanced angle position by fitting the lock key into the key groove,
When the two rotors are relatively rotated toward the intermediate lock position, the tip surface of the lock key is provided along the circumferential direction so that an assisting force assisting the rotation in the rotation direction is generated. A variable internal combustion engine characterized in that a key-side taper portion that gradually inclines is provided, and a groove-side taper portion that gradually inclines along the circumferential direction is provided on the bottom surface of the key groove to which the front end surface of the lock key slides. Valve timing device. An outer rotor that rotates in conjunction with one of the camshaft and crankshaft that drives the intake and exhaust valves of the internal combustion engine, and is arranged concentrically inside the outer rotor, and rotates in conjunction with the other of the camshaft and crankshaft. In the variable valve timing device of the internal combustion engine that makes the valve timing of the intake and exhaust valves variable by relatively rotating within the movable range from the most retarded angle position to the most advanced angle position,
A key groove recessed in one of the inner peripheral portion of the outer rotor and the outer peripheral portion of the inner rotor, and a lock key provided in the other of the inner peripheral portion of the outer rotor and the outer peripheral portion of the inner rotor so as to be movable in the radial direction. And having an intermediate lock mechanism for engaging the outer rotor and the inner rotor at a predetermined intermediate lock position excluding the most retarded angle position and the most advanced angle position by fitting the lock key into the key groove,
A key-side taper portion that gradually slopes along the circumferential direction is provided on the tip surface of the lock key, and a groove-side taper that gradually slopes along the circumferential direction on the bottom surface of the key groove with which the tip surface of the lock key slides. Set up a section,
A pair of lock keys are provided close to each other, and the key side taper portions of the pair of lock keys are inclined in a direction to protrude toward the directions approaching each other,
The groove side tapered portion, the variable valve timing of the internal combustion engine characterized in that it forms a recessed shape substantially V-shaped cross section having two inclined surfaces the pair of key-side taper portion is sliding respectively apparatus. An outer rotor that rotates in conjunction with one of the camshaft and crankshaft that drives the intake and exhaust valves of the internal combustion engine, and is disposed concentrically inside the outer rotor, and rotates in conjunction with the other of the camshaft and crankshaft. In the variable valve timing device of the internal combustion engine that makes the valve timing of the intake and exhaust valves variable by relatively rotating within the movable range from the most retarded angle position to the most advanced angle position,
A key groove recessed in one of the inner peripheral portion of the outer rotor and the outer peripheral portion of the inner rotor, and a lock key provided in a radially movable manner on the other of the inner peripheral portion of the outer rotor and the outer peripheral portion of the inner rotor. And having an intermediate lock mechanism for engaging the outer rotor and the inner rotor at a predetermined intermediate lock position excluding the most retarded angle position and the most advanced angle position by fitting the lock key into the key groove,
A key-side taper portion that gradually slopes along the circumferential direction is provided on the tip surface of the lock key, and a groove-side taper that gradually slopes along the circumferential direction on the bottom surface of the key groove with which the tip surface of the lock key slides. Set up a section,
A fluid pressure chamber recessed in one of the inner peripheral portion of the outer rotor and the outer peripheral portion of the inner rotor, and a radial chamber projecting radially from the other of the inner peripheral portion of the outer rotor and the outer peripheral portion of the inner rotor, the fluid pressure chamber being a retarded chamber And a vane partitioning into an advance chamber, and a fluid pressure control means for controlling the fluid pressure in the retard chamber and the advance chamber,
And assist means for biasing the outer rotor and the inner rotor in a circumferential direction from the most retarded position to the intermediate lock position,
The assist means includes a variable valve timing device of the internal combustion engine you characterized in that it comprises a compression rubber spring spring constant changes according to temperature.

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