The present invention relates to valve timing control apparatus for controlling the opening timing and/or closing timing of an engine valve such as an intake valve and an exhaust valve of an internal combustion engine.
A vane type valve timing control system of a known type includes a lock mechanism including a lock hole formed in a housing of a sprocket on a driving side, and a lock pin which is slidably received in a vane rotor joined to a camshaft and which is arranged to engage with the lock hole to lock the vane rotor unrotational at an intermediate phase position between a most advance position and a most retard position.
The valve timing control system of this type maintains a lock state of the vane rotor until the oil pressure supplied from an oil pump to a retard pressure chamber or an advance pressure chamber is increased at the time of engine start, and maintains an unlock state by utilizing the oil pressure of the oil pump after the oil pressure is increased.
Therefore, a valve timing control system as disclosed in Patent Document (JP2003-222010 A) is arranged to achieve a desired control timing by holding and canceling the lock state by using a hydraulic pressure of a hydraulic circuit different from a hydraulic circuit for the retard pressure and advance pressure.
However, the above-mentioned valve timing control system uses a lock having an annular shoulder surface formed between a large diameter portion and small diameter portion and selectively applies the fluid pressure to the annular shoulder surface. Accordingly, to ensure smooth axial movement of the lock pin, the lock pin is so arranged that both axial ends of the lock pin are always open to the atmosphere.
Therefore, to prevent leakage of the oil pressure in the retard or advance chambers, the system requires a longer side seal having a longer circumferential length for sealing the clearance between one axial end of the lock pin and the inside surface of the housing, and hence requires an increase of the circumferential width of the vane, so that it becomes difficult to increase the operating rotational angle of the vane.
Therefore, it is an object of the present invention to provide a valve timing control apparatus for an internal combustion engine, suitable for ensure a large operation angle of a vane rotor despite a lock pin moved axially by using an operating fluid pressure of a separate system.
According to one aspect of the present invention, a valve timing control apparatus comprises: a driving rotary member; a vane rotor; a lock member received in the vane and arranged to slide forwards and rearwards in an axial direction; and a lock hole to receive a forward end of the lock member; wherein the lock member includes a forward end portion to receive a first fluid pressure which is one of a fluid pressure in the retard pressure chamber and a fluid pressure in the advance pressure chamber in a pressure receiving area, and a rearward end portion to receive the first fluid pressure in a pressure receiving area, the pressure receiving area of the forward end portion receiving the first fluid pressure being equal to the pressure receiving area of the rearward end portion receiving the first pressure; and wherein the lock member further includes a pressure receiving portion including a first surface to which an operating fluid pressure is selectively applied, and a second surface which is opened through an air passage formed in the vane rotor, to atmosphere.
According to another aspect of the invention a valve timing control apparatus comprises: a driving rotary member; a vane rotor; a lock member received in the vane and arranged to slide axially; a lock receiving portion to receive a forward end portion of the lock member when the vane is at a predetermined intermediate position between a most retard position and a most advance position; and a biasing member to urge the lock member toward the lock hole; wherein the lock member includes a forward portion to receive a first fluid pressure which is one of a fluid pressure in the retard pressure chamber and a fluid pressure in the advance pressure chamber in a pressure receiving area, and a rearward portion to receive the first fluid pressure, a pressure receiving area of the forward portion receiving the first fluid pressure being equal to a pressure receiving area of the rearward portion receiving the first pressure; and wherein the valve timing control apparatus further comprises a canceling section to release the lock member from the lock receiving portion.
As shown in
Sprocket 1 is a thick plate shaped like a circular disk. Sprocket 1 includes a toothed portion 5 formed in an outer circumferential portion and arranged to engage with the timing chain. Sprocket 1 is arranged to close a rear opening of a housing (7), and thereby to serve as a rear cover. Sprocket 1 includes a support hole 6 opened through a central portion of sprocket 1, and arranged to receive a vane rotor (9) rotatably. Vane rotor or vane member (9) is fixed to camshaft 2.
Camshaft 2 is rotatably supported through cam bearings on a cylinder head (not shown). Camshaft 2 includes a plurality of cams which are integrally formed at positions arranged in the axial direction, and which are designed to open a plurality of engine valves (intake valves in this embodiment). Camshaft 2 extends from a second end to a first end (left end as viewed in
As shown in
Housing 7 of this example includes a main housing member 7a of sintered metallic material having a hollow cylindrical shape, a front cover 13 closing a front opening of the main housing member 7a, and the rear cover formed by the sprocket 1 and arranged to close the rear opening of main housing member 7a. The main housing member 7a, front cover 13 and sprocket 1 are joined together by bolts 14 (three bolts) passing, respectively, through bolt holes 10a opened, respectively, in the partition walls 10. Front cover 13 includes a central through hole 13a.
Vane rotor or vane member 9 is a single integral member of a metallic material including a central rotor 15 fixed to the first (left) end of camshaft 2 by cam bolt 8, and a plurality (three) of vanes 16a, 16b and 16c projecting radially outwards from the outside circumferential surface of central rotor 15, respectively, at positions arranged around the center axis at substantially regular angular intervals (in this example, 120 degrees).
Central rotor 15 extends from a front (first) end 15b to a rear (second) end 15c in the front and rear direction in the form similar to a hollow cylinder. The front end 15b is formed integrally with a tubular seal guide portion 15a which is located approximately at the center of the front end 15b and which has a thin wall tubular shape of a smaller diameter so as to form a step. The rear end 15c includes an extension extending toward camshaft 2. Central rotor 15 includes an inside cylindrical engagement hole or bore 15d extending from the front end toward the rear end inside the central rotor 15.
Vanes 16a˜16c of vane rotor 9 and partition walls 10 of housing 7 are arranged alternately around the center axis so that each vane is disposed circumferentially between adjacent two of the partition walls 10. Vanes 16a˜16c are unequal in circumferential width in the circumferential direction. The vane 16a having a greatest width and the vane 16b having a medium width are shaped like a fan or a circular sector. The vane 16c having a smallest width is shaped like a projecting thick plate. The radial outward end of each of vanes 16a˜16c is provided with a seal member 17a for sealing the boundary portion between the vane and the inside circumferential surface of main housing member 7a. The radial inward end of each of partition walls 10 of main housing member 7a is provided with a seal member 17b for sealing the boundary portion between the outside circumferential surface of central rotor 15 and the radial inward end of the partition wall 10. As best shown in
When vane member 9 is rotated relatively to the retard side (in the counterclockwise direction), as shown in
In these states shown in
Each of the (three) retard fluid pressure chambers 11 is defined between the second (advance) side surface of one of the vanes 10 facing in the second (advance) rotational (clockwise) direction and the first (retard) side surface of the adjacent partition wall facing in the first (retard) rotational (counterclockwise) direction on the advance (clockwise) side. Similarly, each of the (three) advance fluid pressure chambers 12 is defined between the first (retard) side surface of one of the vanes 10 facing in the first (retard) rotational (counterclockwise) direction and the second (advance) side surface of the adjacent partition wall facing in the second (advance) rotational (clockwise) direction on the retard (counterclockwise) side. Each of the retard pressure chambers 11 is connected through a radially extending communicating hole 11a formed in the central rotor 15, with the first hydraulic circuit 4. Similarly, each of the advance pressure chambers 12 is connected through a radially extending communicating hole 12a formed in the central rotor 15, with the first hydraulic circuit 4.
First hydraulic circuit 4 is configured to control the supply and drain of the operating oil (fluid pressure) for the retard and advance chambers 11 and 12 selectively. As shown in
Retard pressure passage 18 extends from a first port or retard pressure port of first electromagnetic selector valve 21 to an axial passage 18a extending axially in a passage forming end member 37 having an approximately cylindrical shape inserted and held in the central rotor 15 of vane rotor 9 and the seal guide portion 15a. Retard fluid passage 18 is connected through the axial passage 18a and the first communication passages 11a to the retard pressure chambers 11. Similarly, the advance fluid passage 19 extends from a second port or advance pressure port of first electromagnetic selector valve 21 to an axial passage 19a extending axially in the passage forming end member 37. Advance fluid passage 19 is connected through the axial passage 19a and the second communication passages 12a to the advance pressure chambers 12.
The passage forming end member 37 includes an external end portion fixed to a chain cover (not shown) so that the external end portion is non-rotational, and an internal axial portion formed with the passage 18a and 19a and a passage 34a of a second hydraulic circuit 28 for unlocking a lock mechanism as mentioned later.
As shown in
A suction or inlet passage 20b of oil pump 20 and the drain passage 22 are connected to the inside of oil pan 23. A main oil gallery M/G for supplying a lubricating oil to sliding contact portions in the internal combustion engine is connected to a junction point on the downstream side of discharge passage 20a of oil pump 20. A filter 50 is provided on the downstream side of discharge passage 20a of oil pump 20. Oil pump 20 is provided with a flow control valve 51 for controlling the discharge fluid quantity to a desired level by returning an excess amount of the discharged operating oil from the discharge passage 20a to oil pan 23.
The electronic controller includes a computer configured to sense one or more current engine operating conditions by receiving input information from various sensors such as a crank angle sensor (for sensing an engine speed), an airflow meter, an engine coolant temperature sensor, an engine temperature sensor, a throttle valve opening sensor, and a cam angle sensor for sensing a current rotational phase of camshaft 2, and to control the position of the spool in each of the first electromagnetic selector valve 21 and a later-mentioned second electromagnetic selector valve 36 by delivering a control pulse current to the electromagnetic coil of that selector valve in accordance with the sensed engine operating conditions.
In this embodiment, there is provided a holding device (or position holding means) to hold the vane member 9 relative to housing 7 at an intermediate rotational phase position (shown in
As shown in
The first lock hole 24 is elongated in the circumferential direction of sprocket 1 in the form of a circular arc (like a cocoon), as shown in
As shown in
The movement of first lock pin 26 in the advance direction (toward the adjacent retard pressure chamber 11) is limited by the abutment of the forward end portion 26a against the inner side surface 24d (as shown in
As shown in
As shown in
The movement of second lock pin 27 in the retard direction (toward the advance pressure chamber 12) is limited by the abutment of the forward end portion 27a against the riser wall surface 25c of the second bottom surface 25b (as shown in
The positions of first and second lock holes 24 and 25 relative to each other are set as shown in
Thereafter, as shown in
Thus, as the vane rotor 9 rotates relatively from a predetermined retard side position to an advance side position, the first lock pin 26 first descends the stairway of bottom surfaces 24a, 24b and 24c of first lock hole 24, and subsequently the second lock pin 27 descends the stairway of bottom surfaces 25a and 25b of second lock hole 25. Therefore, the vane rotor 9 rotates relatively in the advance direction with receiving limitation of a five-step ratchet function of limiting rotation in the retard direction, and finally reaches the intermediate phase position between the most retard phase angle and the most advance phase angle. Then, vane rotor 9 is held at the intermediate phase position.
First lock pin 26 is slidably received in a first pin hole 31a opened axially through the first vane 16a having the greatest circumferential width, as shown in
The intermediate portion 26b of first lock pin 26 is fit slidably and liquid-tightly in a sleeve 40 forcibly fit in a forward portion of the first pin hole 31a. A rear end portion 26d of first lock pin 26 on the rear side of first pressure receiving portion 26c is slidable liquid-tightly in the first pin hole 31a. The forward end portion 26a has a flat end surface which can abut on each of the bottom surfaces 24a˜24c snugly and tightly.
A first spring 29 is arranged to urge the first lock pin 26 toward the first lock hole 24. First spring 29 is disposed in an inside bore or recess formed in first lock pin 26, between the bottom of the inside bore and the inside wall surface of front cover 13 confronting the first lock hole 24 across first lock pin 26. The first spring 29 serves as an urging member or biasing member.
First lock pin 26 is arranged to receive equal fluid pressures on a front portion and a rear portion. In this example, the forward end portion 26a and rear end portion 26d are arranged to receive the same fluid pressure from the advance pressure chambers 12, respectively, through front and rear fluid holes 45a and 45b formed in the vane 16a. The fluid pressure from the front fluid hole 45a is applied to a forward end surface 26f of the forward end portion 26a and an forward facing annular surface 26g of the front end of intermediate portion 26b. On the other hand, the pressure from the rear fluid hole 45b is applied to a rear end surface 26h of the rear end portion 26d, and the bottom surface 26i of spring groove. The pressure receiving area on the front side equaling the sum of the area of the forward end surface 26f of the forward end portion 26a and the area of the forward facing annular surface 26g is equal to the pressure receiving area on the rear side equaling the sum of the area of the rear end surface 26h of the rear end portion 26d, and the area of the bottom surface 26i of spring groove. The equal pressure of the advance pressure chambers 12 is applied simultaneously to the equal pressure receiving areas on the front side and the rear side in the opposite directions (the forward direction toward the lock hole and the rearward direction away from the lock hole).
Moreover, the first pressure receiving portion 26c includes a forward facing first pressure receiving (annular shoulder) surface 26e for receiving the fluid pressure of a first cancel pressure chamber 32 as mentioned later. On the other hand, the first pressure receiving portion 26c includes a rearward facing atmospheric pressure receiving (annular shoulder) surface opening to the atmosphere through a hole 43 (air passage) formed in vane 16a and front cover 13.
Second lock pin 27 is slidably received in a second pin hole 31b opened axially through the second vane 16b having the medium circumferential width. Second lock pin 27 has a stepped outside circumference like the first lock pin 26. The forward end portion 27a is a portion having the smallest outside diameter. In addition to forward end portion 27a, the second lock pin 27 has an intermediate portion 27b having a medium outside diameter, extending from the forward end portion 27a toward the rear end of second lock pin 27, and a second pressure receiving portion 27c shaped like an outward flange forming a greatest diameter portion on the rear side of intermediate portion 27b. In this example, the forward end portion 27a, intermediate portion 27b and second pressure receiving portion 27c are integral parts of the single integral second lock pin 27.
The intermediate portion 27b of second lock pin 27 is fit slidably and liquid-tightly in a sleeve 41 forcibly fit in a front potion of the second pin hole 31b. A rear end portion 27d of second lock pin 27 on the rear side of second pressure receiving portion 27c is slidable liquid-tightly in the second pin hole 31b. The forward end portion 27a has a flat end surface which can abut on each of the bottom surfaces 25a and 25b snugly and tightly.
A second spring 30 is arranged to urge the second lock pin 27 toward the second lock hole 25. Second spring 30 is disposed in an inside bore or recess formed in second lock pin 27, between the bottom of the inside bore and the inside wall surface of front cover 13 confronting the second lock hole 25 across second lock pin 27. Second spring 30 serves as the urging member or biasing member.
Second lock pin 27 is arranged to receive equal fluid pressures on a front portion and a rear portion. In this example, the forward end portion 27a and rear end portion 27d are arranged to receive the same fluid pressure from the advance pressure chambers 12, respectively, through front and rear fluid holes 46a and 46b formed in the vane 16b. The fluid pressure from the front fluid hole 46a is applied to a forward end surface 27f of the forward end portion 27a and an forward facing annular surface 27g of the front end of intermediate portion 27b. On the other hand, the pressure from the rear fluid hole 46b is applied to a rear end surface 27h of the rear end portion 27d, and the bottom surface 27i of spring groove. The pressure receiving area on the front side equaling the sum of the area of the forward end surface 27f of the forward end portion 27a and the area of the forward facing annular surface 27g is equal to the pressure receiving area on the rear side equaling the sum of the area of the rear end surface 27h of the rear end portion 27d, and the area of the bottom surface 27i of spring groove. The equal pressure of the advance pressure chambers 12 is applied simultaneously to the equal pressure receiving areas on the front side and the rear side.
Moreover, the second pressure receiving portion 27c includes a forward facing second pressure receiving (annular) surface 27e for receiving the fluid pressure of a second cancel pressure chamber 33 as mentioned later. On the other hand, the second pressure receiving portion 27c includes a rearward facing atmospheric pressure receiving (annular) surface opening to the atmosphere through a hole 44 (air passage) formed in vane 16b and front cover 13.
As shown in
The first cancel pressure chamber 32 receives the fluid pressure, applies the received pressure to the first pressure receiving surface 26e, and thereby withdraws the first lock pin 26 from the first lock hole 24 against the spring force of the first spring 29 to disengage the first lock pin 26 from first lock hole 24. Similarly, the second cancel pressure chamber 33 receives the fluid pressure, applies the received pressure to the second pressure receiving surface 27e, and thereby withdraws the second lock pin 27 from the second lock hole 25 against the spring force of the second spring 30 to disengage the second lock pin 27 from second lock hole 25.
The supply/drain passage 34 extends from a first end connected with a port of second electromagnetic valve 36, to a second end connected with supply/drain branch passages 34a formed in the passage forming member 37. Each of supply/drain branch passages 34a first extends axially, and is bent to a radial direction. The supply/drain branch passages 34a are connected, respectively, through the first and second fluid passage holes 38a and 38b, with the first and second cancel pressure chambers 32 and 33.
The passage forming member 37 includes annular grooves formed in the outside circumference surface at axial positions and arranged to receive (three) annular seal members 39, respectively, to sealingly separate the open ends of the passages 18a and 19a and the supply/drain passages 34a opened in the support hole 15d.
The second electromagnetic selector valve 36 of this example is a 4-port, 3-position proportional type valve configured to move a spool (not shown) axially back and forth against a valve spring by an on-off control current delivered from the electronic controller. Thus, second electromagnetic valve 36 connects the supply/drain passage 34, selectively with the passage 35a or 35b, and seals off the operating fluid in the cancel pressure chambers 32 and 33, by shutting the supply/drain passage 34 off from the passages 35a and 35b.
[OPERATIONS] The thus-constructed valve timing control apparatus or system is operated as follows:
[OPERATION CONTROL AFTER SHORT STOP] When the engine is stopped by turn-off of the ignition switch after a normal vehicle driving operation, the oil pump 20 is stopped too. Accordingly, the supply of the operating oil to the pressure chambers 11 or 12 is stopped, and the vane rotor 9 is allowed to rotate freely in the forward and backward directions. When the cam torque timing in the alternating torque at the time of the engine stoppage is a negative torque, the vane rotor 9 rotates in the advance direction and the system becomes unable to hold the vane rotor 9 at the most retard phase, so that an engine stop control is required to achieve a positive torque at the time of engine stoppage.
In this case, the electronic controller supplies electricity to first electromagnetic selector valve 21, thereby holds the spool at the intermediate neutral position, and shuts the passages 18 and 19 from the passages 20a and 22.
In the stop state in which the drive of oil pump 20 is stopped, the operating fluid in discharge passage 20a may return from oil pump 20 to oil pan 23 because of the lift (or head) of the pump, and moreover the operating fluid in the pressure chambers 11 and 12 may flow downwards. If the operating oil is removed from pressure chambers 11 and 12, the vane rotor 9 at the most retard side may flap due to the alternating torque at the time of an engine start, and cause flapping noises by collision with the partition walls 10. Therefore, the control system according to this embodiment seals the operating fluid in the pressure chambers 11 and 12 by shutting off the fluid passages 18 and 19, and thereby prevent flapping of vane rotor 9.
If the engine is restarted in the state in which the warm up state is maintained, after the elapse of a short time within 15 minutes, for example, the effective compression ratio is lowered because, at this instant, the vane rotor 9 is held at the rotational phase position on the most retard side shown in
The above-mention operation control after a short time stoppage is performed, for example, in the case of idling stop of stopping the operation of the engine during a driving operation of the vehicle automatically irrespectively of turn on/off of the ignition switch when the time from a stop to a restart is short. The system can lower the effective compression ratio and improve the engine starting performance in the same manner.
[OPERATION CONTROL AFTER LONG STOP] When the ignition key is turned to start cranking after the elapse of a long time longer than 15 minutes, for example, in the state in which the engine is cooled, then the electronic controller shifts the spool in first electromagnetic selector valve 21 axially to the valve position to connect the discharge passage 20a with one of the retard pressure passage 18 and advance pressure passage 19, and to connect the drain passage 22 with the other of the retard and advance pressure passages 18 and 19.
Simultaneously, the electronic controller energizes the second electromagnetic selector valve 36 to connect the supply/drain passage 34 with the drain branch passage 35b. Therefore, the operating fluid is drained from the first and second cancel pressure chambers 32 and 33, and the first and second lock pins 26 and 27 are urged forwards (toward the respective lock holes 24 and 25) by the springs 29 and 30, respectively.
In this early stage of the cranking operation, the discharge pressure of oil pump 20 is still low, the oil pressure supplied through the one of the retard and advance pressure passage 18 and 19 is still low.
Therefore, the vane rotor or vane member 9 rotates slightly to the advance side by the alternating torque acting on camshaft 2, specifically by the negative torque, and hence the forward end portion 26a of first lock pin 26 abuts on the first bottom surface 24a of first lock hole 24, as shown in
Thereafter, the first lock pin 26 descends stepwise through second bottom surface 24b to third bottom surface 24c and slides on the third bottom surface 24c to the advance side as shown in
In this state, as shown in
With this operation of the lock pins 26 and 27, the vane rotor 9 is held at the intermediate phase position as shown in
When the normal engine operation is started after the warm-up of the engine, and the engine speed enters a high speed range, for example, then the first electromagnetic selector valve 21 connects the discharge passage 20a with advance pressure passage 19 and connects the drain passage 22 with retard pressure passage 18.
Therefore, the pressure in each retard pressure chamber 11 becomes lower and the pressure in each advance pressure chamber 12 becomes higher. As a result, the vane rotor 9 is rotated to the most advance side. Thus, the system can advance the intake valve opening timing, increase the overlap with the exhaust valve, and increases the engine output by increasing the intake air quantity.
In this state, as mentioned before, the second electromagnetic selector valve 36 is held in the position to supply the fluid pressure to each of the pressure chambers 32 and 33 by connecting the supply/drain passage 34 with supply passage 35a and to shut off the drain passage 35b. Therefore, the vane rotor 9 is allowed to rotate freely.
In this way, the control system according to this embodiment is arranged to vary the engine compression ratio at the time of a restart, in accordance with the time length of the engine stop period, that is, the temperature of the engine. Therefore, the system can improve the engine startability by reducing the torque load at the time of a start, reduce vibrations and improve the exhaust emission performance.
Furthermore, the position holding device or means (26, 27, 24, 25, 28) can hold the vane rotor 9 reliably at the intermediate phase position. The lock guide groove of each lock hole (24, 25) is arranged to have the stepped bottom (24a˜24c, 25a˜25b) to guide the lock pin only in the direction toward the lock hole (24, 25), so that the lock pin is guided reliably and stably.
The operating fluid pressure for the cancel pressure chambers 32 and 33 is prepared by a hydraulic circuit separately from the pressure for the retard and advance chambers 11 and 12. Therefore, the system can supply the operating fluid pressure responsively to the cancel chambers 32 and 33, as compared to the arrangement using the fluid pressure for the chambers 11 and 12 to the chambers 32 and 33. As a result, the system can move each lock pin 26 or 27 rearwards quickly, and eliminate the need for seal mechanism between the chambers 11 and 12 and the chambers 32 and 33.
Instead of providing air passages to both axial ends of a lock pin as in the earlier technology, each lock pin (26, 27) according to the embodiment is balanced in the axial direction by the application of the oil pressure on both ends of the lock pin to ensure smooth movement of the lock pin. Therefore, the system can move the lock pin quickly in the axial direction by the spring (29, 30) and the cancel pressure in the cancel pressure chamber (32, 33).
Thus, the system according to the embodiment can achieve the same effect of air passages by applying the equal oil pressures to the forward end portion and riverward end portion of the lock member without the need for forming an air passage in the lock hole forming member (1a, 1b). Therefore, it is possible to reduce side clearances between both axial end surfaces of the widest vane 16a and the confronting surfaces of front cover 13 and sprocket 1.
Therefore, it is possible to reduce the circumferential width of the widest vane 16a as compared to the earlier technology. Consequently, it is possible to increase the rotational angular range of vane rotor 9 relative to housing 7 by increasing the angular range of vane 16a between the circumferentially confronting side surfaces 10b and 10c of the partition walls 10.
The air holes 43 and 44 for leading the upper side surfaces of first and second pressure receiving portions 26c and 27c opposite to the pressure receiving surfaces 26e and 27e, to the outside or the atmosphere are formed in the vanes 16a and 16b and the front cover 13. There are no connections with the advance pressure chambers 12, so that the operating fluid does not leak in this portion.
The arrangement of supplying the advance pressure of advance chambers 12 to both of the forward and rearward end portions of the lock pin (26, 27) is effective for stabilizing the behavior of the lock pin. At the time of engine start, air may be involved in the operating oil supplied to retard chambers 11. Therefore, if this operating oil is supplied to both ends of each lock pin 26 or 27, the air involved in the operating oil might make unstable the behavior of the lock pin, resulting in generation of undesired noises. On the other hand, the operating oil supplied to advance chambers 12 during steady state operation after engine start is almost free from air involvement. Therefore, the arrangement of supplying the advance pressure of advance chambers 12 to both ends of the lock pin can make stable the behavior of the lock pin (26, 27) and prevent generation of undesired noises.
The riser wall surface 25c between first and second bottom surfaces 25a and 25b of the second lock guide groove is made high. This riser wall structure can increase the strength, and improve the durability of enduring repetitive collision of the second lock pin 27 against the riser wall surface 25c. When, on the other hand, first lock pin 26 is engaged with first lock hole 24, the forward end portion 26a abuts against the inner side surface 24d rising from the deepest bottom surface 24c and having a greater surface area. This structure further improves the durability.
Each of the first and second lock guide grooves is cocoon-shaped. Therefore, each of first and second lock pins 26 and 27 can move smoothly in the guide groove with rotation of vane rotor 9.
The illustrated example of the embodiment employs, as a parameter, the elapsed time from an engine stop to a restart. By using the engine temperature sensed by the engine temperature sensor directly as the parameter, instead of using the elapsed time, it is possible to a practical control system arranged to control the valve timing in accordance with the engine temperature, for example by examining whether the engine temperature is lower than or equal to a predetermined temperature or higher than the predetermined temperature.
In the illustrated example, the position holding device is constructed by the first lock section including first lock pin 26 and first, second and third bottom surfaces 24a˜24c and the second lock section including second lock pin 27 and first and second bottom surfaces 25a and 25b. Therefore, it is possible to reduce the wall thickness of the sprocket 1 in which the lock holes 24 and 25 are formed. The arrangement using a single lock pin and a single staircase of steps 24a, 24b, 24c, 25a and 25b requires a thick wall for the sprocket 1 to ensure the height of this staircase. By contrast, the arrangement of the illustrated example makes it possible to reduce the wall thickness of sprocket 1, to reduce the axial dimension of the valve timing control apparatus and to improve the flexibility of the layout.
The lock member (26, 27) is in the form of a cylindrical lock pin and the pressure receiving portion (26c, 27c) is in the form of an outward flange. Therefore, the lock member can be fabricated easily and inexpensively.
The present invention is not limited to the illustrated embodiment. The valve timing control apparatus according to the present invention can be applied not only to the intake side, but also to the exhaust side.
According to one of possible interpretations of the illustrated embodiment, a valve timing control apparatus includes a basic structure which comprises: a driving rotary member adapted to receive a rotational force from a crankshaft; a vane rotor which is adapted to be connected with a camshaft, which is arranged to rotate relative to the driving rotary member, and which includes at least one vane defining a retard pressure chamber and an advance pressure chamber in the inside (cavity) of the driving rotary member; a lock member received in the vane and arranged to slide axially; a lock receiving portion such as a lock hole (formed in the driving rotary member (lock hole forming member 1a, 1b)) to receive a forward end of the lock member when the vane is rotated relatively to a predetermined angular position; and a biasing member to urge the lock member toward the lock receiving portion. The lock member includes forward and rearward end portions arranged to receive equal fluid pressures, respectively, in rearward and forward directions (to balance the lock member in an axial direction). In addition to the basic structure, the valve timing control apparatus may further comprise any one or more of following features (f1)˜(f19).
(f1)) The lock member (26, 27) may further include a pressure receiving portion (26c, 27c) (in the form of an outward flange, in the illustrated example) including a first surface (26e, 27e) (lower surface) to which an operating fluid pressure (cancel pressure) is selectively applied, and a second surface (upper surface) which is opened, through an air passage (43, 44) formed in the vane rotor, to the atmosphere (to an outside to receive an atmospheric pressure). (f2) The valve timing control apparatus further comprises a canceling section to release the lock member from the lock receiving portion (lock hole) selectively.
(f3) The lock hole is elongated circumferentially so as to form a lock guide groove elongated in one of an advance direction and a retard direction (or circumferentially around the center axis of the vane rotor 9) and arranged to allow the vane rotor to rotate relative to the driving rotary member in a state in which the forward end of the lock member is received in the lock guide groove. (f4) The lock member is a lock pin including a (cylindrical) shank and an (circular) outward flange (26c, 27c) serving as the pressure receiving portion (formed between the forward end portion (26a, 27a) and the rearward end portion (26d, 27d)). In this case, the lock member can make easier the production process and prevent an increase of the manufacturing cost.
(f5) The driving rotary member includes a cylindrical housing including at least one shoe or partition wall projecting radially inwards, and a cover member closing an open end of the housing and including a through hole formed on a radial inner side of an outside circumference of the vane rotor, the vane is formed with the air passage extending to the though hole of the cover member and thereby opening the second surface of the pressure receiving portion to the atmosphere. (f6) The valve timing control apparatus further comprises a first hydraulic circuit (4, 21) to regulate the fluid pressure in the retard pressure chamber and the fluid pressure in the advance pressure chamber, and a second hydraulic circuit (28, 36) to supply the operating fluid pressure different from the fluid pressure in the retard pressure chamber and the fluid pressure in the advance pressure chamber. This feature can improve the response speed for supplying the operating fluid pressure to the cancel pressure chamber for the pressure receiving portion, and eliminate the need for seals in various portions.
(f7) The first hydraulic circuit includes a first control valve to regulate the fluid pressure in the retard pressure chamber and the fluid pressure in the advance pressure chamber, and the second hydraulic circuit includes a second control valve to regulate the operating fluid pressure applied to the first surface of the pressure receiving portion of the lock member. (f8) The second control valve is a selector valve having at least a first valve position to increase the operating fluid pressure (by connecting a cancel pressure chamber (32, 33) with a pump outlet passage 20a) and a second valve position to decrease the operating fluid pressure (by connecting the cancel pressure chamber (32, 33) with a drain passage 22).
(f9) The first fluid pressure received by the forward end portion (26a, 27a) and the rearward end portion (26b. 27b) of the lock member (26, 27) is the fluid pressure in the advance pressure chamber. In this case, the advance fluid pressure is applied equally to both of the forward end portion and the rearward end portion, so that the forward force and rearward force produced by the fluid pressures are balanced and the lock member can move quickly by the operating fluid pressure applied to the pressure receiving portion (and a biasing member). (f10) The lock guide groove includes a stepped bottom descending stepwise toward the lock hole (or toward the deepest bottom).
(f11) In addition to the vane which is a first vane, the lock member which is a first lock member received in the first vane, the lock hole which is a first lock hole, the biasing member which is a first biasing member, the vane rotor further includes a second vane defining a retard pressure chamber and an advance pressure chamber in the inside of the driving rotary member, and the valve timing control apparatus further comprises a second lock member received in the second vane and arranged to slide forwards and rearwards in the axial direction (of the vane rotor 9), a second lock hole (formed in the driving rotary member (lock hole forming member 1a, 1b)) to receive a forward end of the second lock member when the second vane is at a predetermined angular position, and a second biasing member to urge the second lock member toward the second lock hole. The second lock member includes forward and rearward end portions arranged to receive equal fluid pressures, respectively, in rearward and forward directions (to balance the lock member in the axial direction). The second lock member (26, 27) may further include a pressure receiving portion (26c, 27c) (outward flange) including a first surface (26e, 27e) (lower surface) to which an operating fluid pressure (cancel pressure) is selectively applied, and a second surface (upper surface) which is opened, through an air passage (43, 44) formed in the vane rotor, to the atmosphere (to an outside to receive an atmospheric pressure).
(f12) Each of the first and second lock holes is elongated circumferentially so as to form a (first or second) lock guide groove elongated in one of an advance direction and a retard direction (or circumferentially around the center axis of the vane rotor 9) and arranged to allow the vane rotor to rotate relative to the driving rotary member in a state in which the forward end of the (first or second) lock member is received in the (first or second) lock guide groove. (f13) The first lock hole is arranged to allow the vane rotor to rotate relative to the driving rotary member in a state in which the forward end of the first lock member is received in the first lock guide groove, and the second lock hole is arranged to allow the vane rotor to rotate relative to the driving rotary member in a state in which the forward end of the second lock member is received in the second lock guide groove.
(f14) The first lock member and the first lock hole are arranged to allow rotation of the vane rotor relative to the driving rotary member within a predetermined angular range in a state in which the first lock member is engaged with the first lock hole; and the second lock member and the second lock hole are arranged to lock the vane rotor to prevent rotation of the vane rotor relative to the driving rotary member when the second lock member is engaged with the second lock hole (or the second lock member abuts on a lowest bottom (25b) of the second lock hole) in the state in which the first lock member is engaged with the first lock hole. (f15) The second lock guide groove (or the second lock hole) includes a stepped bottom descending stepwise toward a deepest bottom. (f16) The first lock guide groove (or the first lock hole) includes a stepped bottom descending stepwise to a deepest bottom, and the first and second lock holes are so arranged that the second lock member descends the stepped bottom of the second lock guide groove and engages with the deepest bottom of the second lock hole after the first lock member descends the stepped bottom of the first lock guide groove and engages with the deepest bottom of the first lock hole. (f17) The number of steps of the stepped bottom of the first lock guide groove is greater than the number of steps of the stepped bottom of the second lock guide groove. (f18) The height of a riser wall surface rising from a lowest bottom surface (25b) of the second guide groove is greater than the height of a riser wall surface rising from a lowest bottom surface (24c) of the first lock guide groove. (f19) At least one of the first lock hole, the first lock guide groove, the second lock hole and the second lock guide groove is elongated circumferentially, or shaped like a cocoon.
This application is based on a prior Japanese Patent Application No. 2010-243845 filed on Oct. 29, 2010. The entire contents of this Japanese Patent Application are hereby incorporated by reference.
Although the invention has been described above by reference to certain embodiments of the invention, the invention is not limited to the embodiments described above. Modifications and variations of the embodiments described above will occur to those skilled in the art in light of the above teachings. The scope of the invention is defined with reference to the following claims.
Number | Date | Country | Kind |
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2010-243845 | Oct 2010 | JP | national |