Patent Application
20150276057
The present invention relates to an automatic transmission clutch control apparatus mounted on an automotive vehicle or the like, and is configured to hold application of a clutch without a clutch apply pressure after the clutch has been applied.
Multiplate hydraulic clutches are commonly known. A patent document 1 discloses one example. This clutch includes: friction plates spline-fitted on an inner peripheral surface of a clutch drum; friction plates spline-fitted on an outer peripheral surface of a clutch hub disposed inside of the clutch drum; a clutch piston configured to be hydraulically actuated; and a return spring configured to press the clutch piston back into a clutch release position. Application of the clutch is implemented by supplying a clutch apply pressure oil, and thereby causing the clutch piston to travel in its axial direction against an elastic force of the return spring, and causing the friction plates to be pressed on each other, to establish a clutch apply condition where torque is transmittable between the clutch drum and the clutch hub. Release of the clutch is implemented by draining the clutch apply pressure oil, and thereby causing the clutch piston to be pressed back by the return spring, and releasing the friction plates from the pressing force, to establish a clutch release condition where the torque therebetween is not transmitted.
Patent Document 1: Japanese Patent Application Publication No. H07-12221
However, the conventional clutch described above is confronted by the following problem. In the conventional clutch device, while the clutch is being applied, it is necessary to constantly apply the high clutch apply oil pressure to the clutch piston for ensuring that the friction plates are provided with a pressing force required to resist the return force of the return spring. This necessarily burdens an oil pump, and thereby adversely affects fuel efficiency. Moreover, with regard to the clutch, while the clutch is being applied, a seal ring, which is provided at a location where oil is communicated between members rotating relative to each other, prevents leakage of oil from a clutch apply oil passage. While the clutch is being applied, the high clutch apply pressure is applied to the seal ring, so that the seal ring is pressed onto one of the rotating members while they are rotating. This causes a friction loss therebetween by the seal ring, and thereby adversely affects the fuel efficiency.
The present invention is made with attention to the problem described above. It is an object of the invention to provide a clutch device with which it is possible to reduce an energy loss caused by a clutch apply oil pressure while a clutch is being applied.
According to the present invention, in order to accomplish the object described above, an automatic transmission clutch control apparatus includes a manual valve, a clutch, a clutch release valve, and a lock mechanism. The manual valve is configured to output a clutch apply pressure when a drive position is selected by operation of a selector. The clutch is configured to be brought into a clutch apply state by travel of a clutch piston by supply of the clutch apply pressure. The clutch release valve is configured to output a clutch release oil pressure by bypassing the manual valve. The lock mechanism is configured to: mechanically lock the clutch piston in a position under a condition that the clutch apply pressure is reduced, wherein the position of the clutch piston is when the clutch is bought into the clutch apply state by supply of the clutch apply pressure; and release the locking by the clutch release pressure outputted by the clutch release valve.
According to the automatic transmission clutch control apparatus of the present invention, it is unnecessary to hold the clutch apply oil pressure while the clutch is being applied, and it is possible to prevent the high clutch oil pressure from being applied to the seal ring disposed between the members rotating relative to each other under the clutch apply pressure, and thereby reduce the energy loss caused by the clutch apply oil pressure while the clutch is being applied. According to this configuration, the lock of the lock mechanism can be released irrespective of the selected position of the manual valve. This makes it possible to cause the transmitted torque to become substantially equal to zero, and prevent interlocking.
The following describes an embodiment of the present invention in detail with reference to the drawings.
First, the following describes whole configuration of a clutch device employed by an automatic transmission clutch control apparatus according to the embodiment. This clutch device is used to switch a forward-reverse switching device of a vehicular belt-type continuously variable transmission.
The following describes the forward-reverse switching device.
Sun gear 2 includes an inner peripheral end portion spline-engaged with a cylindrical portion of a stationary-side sheave 6 of a primary pulley, wherein the cylindrical portion projects in the axial direction, and serves as an output member of forward-reverse switching device 1. The side surface of sun gear 2 opposite to sheave 6 is coupled to an inner peripheral portion of a forward clutch hub 15, and serves as an input member for driving torque. Ring gear 3 is meshed with a spline formed in an inner peripheral surface of an outer cylindrical part 7a of a forward clutch drum 7, and serves as an input member of forward-reverse switching device 1. Pinion carrier 5 includes an outer peripheral portion coupled to a brake drum 8, and serves as a stationary member of forward-reverse switching device 1.
Specifically, a plurality of friction plates 10a, 10b are disposed between an outer peripheral surface side of an outer cylindrical part 8a of brake drum 8 coupled to pinion carrier 5 and an inner peripheral surface of a cylindrical case-side member 9A fixed to a transmission case, and engaged with corresponding ones thereof. Moreover, a reverse brake 13 is provided to perform application and release between brake drum 8 and case-side member 9A by forward and rearward travel of a brake piston 12 in response to supply of brake pressure oil to a brake oil chamber 11 and drainage of brake pressure oil from brake oil chamber 11. A return spring 14 is arranged between a tip end portion of brake piston 12 and friction plate 10. Accordingly, when reverse brake 13 is applied, pinion carrier 5 is fixed and held stationary with respect to the case side.
On the other hand, a forward clutch 16 is provided between forward clutch drum 7 coupled to ring gear 3 and forward clutch hub 15 coupled to sun gear 2. Specific configuration of forward clutch 16 is described later.
When a driving force is inputted from an engine not shown or the like through input shaft 24 and others to forward clutch drum 7 as described below under the condition that reverse brake 13 is released and forward clutch 16 is applied, the rotating elements of the planetary gearset of forward-reverse switching device 1 rotate as a solid unit. As a result, sun gear 2 drivingly rotates at direct drive (speed ratio equal to 1), so that sheave 6 coupled to sun gear 2 rotates at the same rotational speed and same torque as the driving input. Under this condition, the vehicle is driven forward at a speed ratio corresponding to the pulley ratio.
On the other hand, when the driving force is being inputted to forward clutch drum 7 under the condition that forward clutch 16 is released and reverse brake 13 is applied in contrast to the situation described above, sun gear 2 rotates in the reverse direction at a reduced speed. Under this condition, the vehicle is driven rearward at a speed ratio corresponding to the pulley ratio. When both of forward clutch 16 and reverse brake 13 are released, forward-reverse switching device 1 is in a neutral state where even if a driving force is inputted to forward clutch drum 7, no driving force is transmitted to sheave 6 of the pulley.
The following describes specific configuration of forward clutch 16. As described above, in forward clutch 16, a plurality of drive plates 17 that are fitted with the spline of the inner peripheral side of forward clutch drum 7 and movable in the axial direction, and a plurality of driven plates 18 that are fitted with the spline of the outer peripheral surface of forward clutch hub 15 and movable in the axial direction, are arranged and layered alternately in the axial direction, wherein friction surfaces thereof are configured to press each other.
A diaphragm spring 20 is disposed between one of drive plates 17 closest to forward-reverse switching device 1 (the leftmost one in
Forward clutch piston 21 is inserted in a tubular space between outer cylindrical part 7a and inner cylindrical part 7b of forward clutch drum 7, and is configured to travel in the axial direction. Outer cylindrical part 21a of forward clutch piston 21 is folded outwardly in the radial direction, and is configured to contact the rightmost one of drive plates 17 in
The right-side portion of inner cylindrical part 7b of forward clutch drum 7 in
A separation plate 26 is attached to an outer peripheral surface of the left end portion of cylindrical part 23a of forward support drum 23 in
A clutch apply pressure chamber 30 is defined between side wall 7c of forward clutch drum 7 and forward clutch piston 21, whereas a clutch release pressure chamber 31 is defined between separation plate 26 and forward clutch piston 21.
In the configuration described above, a lock mechanism 32 is provided between inner cylindrical part 21b of forward clutch piston 21 and cylindrical part 23a of forward support drum 23, wherein lock mechanism 32 includes a part thereof. Lock mechanism 32 is configured to mechanically hold forward clutch piston 21 in the engaged position, and thereby hold forward clutch 16 in the applied state, even if the clutch apply pressure is reduced or removed. Lock mechanism 32 includes inner cylindrical part 21b of forward clutch piston 21, cylindrical part 23a of forward support drum 23, an auxiliary piston 33, balls 34, a press spring 35, and seal members 22, 28, 39, and is configured as described below.
As shown in
On the other hand, inner cylindrical part 7b of forward clutch drum 7 that supports inner cylindrical part 21b of forward clutch piston 21 is formed with a plurality of ball-retaining holes 36, and a clutch apply pressure through hole 7d, and an annular seal groove 7e, wherein ball-retaining holes 36 are arranged in the circumferential direction, and each ball-retaining hole 36 is capable of receiving insertion of ball 34, and clutch apply pressure through hole 7d is located at the right side in
Ball 34 is constantly in ball-retaining hole 36, and travels in the radial direction within ball-retaining hole 36 depending on the positions of forward clutch piston 21 and auxiliary piston 33. However, irrespective of the position of auxiliary piston 33, ball 34 constantly projects inward and outward in the radial direction from ball-retaining hole 36, and thereby is in contact with first tapered surface 21c of forward clutch piston 21 and a second tapered surface 33d of auxiliary piston 33 described later. The number of ball-retaining holes 36 in which balls 34 are inserted may be determined based on a maximum transmissible torque through forward clutch 16.
Auxiliary piston 33 is an annular member, and is arranged movable in the axial direction of the clutch between inner cylindrical part 7b of forward clutch drum 7 and cylindrical part 23a of forward support drum 23. Auxiliary piston 33 is in contact with the radially inside portion of ball 34 at its outer peripheral side, and is formed with a ball travel slope part 33b on which ball 34 can be moved in the radial direction depending on the position of auxiliary piston 33. The ball travel slope part 33b is formed as a recess in a part of the outer periphery of auxiliary piston 33.
The bottom portion of ball travel slope part 33b includes a second tapered surface 33d whose depth gradually gets shallower as followed rightward in
Seal member 22 is inserted in an annular seal groove 33c in the left-side portion of the outer peripheral surface of auxiliary piston 33 with respect to ball travel slope part 33b in
Press spring 35 is arranged between the right end side surface of auxiliary piston 33 in
A clutch apply pressure through hole 37 and a clutch release pressure through hole 38 are formed in cylindrical part 23a of forward support drum 23 arranged inside of the annular auxiliary piston 33, wherein clutch apply pressure through hole 37 is configured to supply and drain the clutch apply pressure oil to and from clutch apply pressure chamber 30 through the space where press spring 35 is arranged, and wherein clutch release pressure through hole 38 is configured to supply and drain the clutch release pressure oil to and from clutch release pressure chamber 31. Clutch apply pressure through hole 37 and clutch release pressure through hole 38 are configured to fail to communicate with each other by seal member 39 that is disposed between cylindrical part 23a of forward support drum 23 and auxiliary piston 33.
Boss part 9a of case-side member 9B is formed with a clutch apply pressure communication passage 40 and a clutch release pressure communication passage 41 which are configured to communicate with clutch apply pressure through hole 37 and clutch release pressure through hole 38 formed in cylindrical part 23a of forward support drum 23, respectively.
Clutch apply pressure communication passage 40 and clutch release pressure communication passage 41 are connected to a control valve device 42. Control valve device 42 is configured to set the clutch apply pressure and the clutch release pressure to optimal values, and determine timings of supply and drainage. Accordingly, control valve device 42 also functions to drain the clutch apply pressure oil from clutch apply pressure chamber 30 after lock mechanism 32 is locked by application of forward clutch 16.
The following describes a principle of lock mechanism 32.
In summary, the force pressing the auxiliary piston 33 via ball 34 by forward clutch piston 21 by the return force F of diaphragm spring 20 is equal to the component F sin φ sin φ cos φ in the axial direction. Accordingly, in this embodiment where θ is set to 10° and φ is set to 25°, auxiliary piston 33 can be held by a force that is about 15% of return force F of diaphragm spring 20.
Next,
The following describes operation of the clutch device described above.
In lock mechanism 32, forward clutch piston 21 is in the clutch release position, namely, in the rightmost position in
Accordingly, although auxiliary piston 33 is biased to the clutch apply side (leftward in
When a select lever is put into a forward drive position under a condition that the engine is energized by a driver, the clutch apply pressure oil is supplied from control device 42 to clutch apply pressure chamber 30 via clutch apply pressure communication passage 40, clutch apply pressure through hole 37, and the space where press spring 35 is inserted, etc. When clutch apply pressure chamber 30 is filled with the clutch apply pressure oil, then the internal pressure of clutch apply pressure chamber 30 rises gradually so that forward clutch piston 21 starts to travel leftward in
Ball 34 of lock mechanism 32 is constantly applied with the pressing force leftward in
On the other hand, along with the forward travel of forward clutch piston 21, first tapered surface 21c of forward clutch piston 21, which suppresses outward movement of ball 34 in the radial direction, also travels forward so that the contact point between first tapered surface 21c and ball 34 moves outwardly in the radial direction. In this way, ball 34 starts to move outwardly in the radial direction.
This outward movement of ball 34 in the radial direction causes auxiliary piston 33, whose second tapered surface 33d has been pressed by press spring 35 to be constantly in contact with ball 34, to start to move leftward in
In this way, as the clutch pressure rises, diaphragm spring 20 gets compressed to cause an elastic force to press drive plates 17 and driven plates 18. This causes a frictional torque therebetween, and thereby establishes a half-clutch condition shown in
As the clutch apply pressure further rises, diaphragm spring 20 is completely compressed to reach a condition shown in
Thereafter, after a predetermined period of time, the clutch apply pressure oil is drained from clutch apply pressure chamber 30 by control device 42. At this moment, the oil pressure pressing the forward clutch piston 21 in the clutch apply direction disappears, but lock mechanism 32 is maintained in the lock state mechanically locked in the lock position described above, so that forward clutch piston 21 is also maintained at the position. Accordingly, forward clutch 16 is maintained in the applied state, and forward clutch drum 7 and forward clutch hub 15 rotate as a solid unit, while fully transmitting the inputted torque.
Under the completely applied condition, diaphragm spring 20 is completely compressed, to cause an elastic force, wherein the elastic force is required to be sufficient to transmit the entire inputted torque between drive plates 17 and driven plates 18. Moreover, under the completely applied condition, the lock position of lock mechanism 32 is mechanically determined by the completely compressed state of diaphragm spring 20, so that the lock position is constantly maintained optimal irrespective of variation of diaphragm spring 20 and wear of drive plates 17 and driven plates 18 due to getting old.
In order to release forward clutch 16 from the applied state, the clutch release pressure oil is supplied from control device 42 to clutch release pressure chamber 31 via clutch release pressure communication passage 41, clutch release pressure through hole 38, etc. When clutch release pressure chamber 31 is filled with the clutch release pressure oil and the release pressure rises gradually, the pressure directly pressing the forward clutch piston 21 rightward in
As a result, auxiliary piston 33 is pressed by the release pressure to travel rightward in
When diaphragm spring 20 is returned from the compressed (elastically deformed) state, the pressing force to drive plates 17 and driven plates 18 disappears, so that forward clutch hub 15 becomes free from forward clutch drum 7. Forward clutch piston 21 is pressed onto side wall 7c of forward clutch drum 7, and is maintained at this position by return spring 29. After a time period has elapsed to ensure that release of forward clutch 16 is completed, control device 42 drains the clutch release pressure oil from clutch release pressure chamber 31, to reach the condition shown in
The following describes a clutch control apparatus for controlling the clutch device described above. The clutch control apparatus includes control device 42. Control device 42 includes a microcomputer, a control valve, etc., and includes a hydraulic circuit as partly shown in
Second pilot valve 53 produces a second pilot pressure by lowering the first pilot pressure supplied from first pilot valve 51, and supplies the second pilot pressure to an on-off switching solenoid valve 54 and a third pilot valve 55.
Third pilot valve 54 produces a third pilot pressure by lowering the second pilot pressure supplied from second pilot valve 53, and supplies the third pilot pressure to a two-directional linear solenoid valve 56. Since pressure is lowered sequentially by each pilot valve, the obtained pressures are in order of line pressure>first pilot pressure>second pilot pressure>third pilot pressure.
Three-directional linear solenoid valve 52 is capable of lowering the first pilot pressure supplied from first pilot valve 51 depending on an operating state of the vehicle, and adjusts the pressure to an optimal apply/release pressure for application of forward clutch 16 and reverse brake 13 depending on the operating state, and then supplies the adjusted pressure to a manual valve 57. Three-directional linear solenoid valve 52 is controlled by the microcomputer.
Manual valve 57 switches the flow of oil depending on the position of a valve spool that is changed by operation of select lever 58 by a driver. Manual valve 57 can be switched by the driver to a P position for parking of the vehicle, an R position for rearward drive, an N position for producing a neutral state where no torque is transmitted, a D position for forward drive, and an L position capable of generating engine braking in forward drive. Specific configuration of manual valve 57 is described later.
On-off switching solenoid valve 54 supplies the clutch release oil pressure (“OFF PRESSURE” in
Two-directional linear solenoid valve 56 regulates the third pilot pressure supplied from third pilot valve 54 variably depending on the operating state, and outputs the regulated third pilot pressure to a lockup control valve 59.
Lockup control valve 59 performs lockup and release of the lockup by distributing the third pilot pressure regulated by two-directional linear solenoid valve 56 to an apply chamber and a release chamber of a lockup mechanism of a torque converter not shown. The magnitude of the regulated third pilot pressure may be set to achieve a slip lockup condition.
The following describes manual valve 57. The relationship between ports and spool is set so that when select lever 58 is put in a selected position releasing the forward clutch 16, namely, in the P or R or N position, the apply/release pressure regulated by three-directional linear solenoid valve 52 can be supplied as the clutch release pressure to forward clutch 16 and lock mechanism 32. It is in this point that manual valve 57 is different from normal manual valves.
When in the P or N position, supply of the clutch apply pressure to forward clutch 16 and reverse brake 13 is prevented, and the oil is drained from clutch apply pressure chamber 30 and brake oil chamber 11 via manual valve 57. Accordingly, forward clutch 16 and reverse brake 13 are in their neutral states where no torque is transmissible. On-off switching solenoid valve 54 also prevents supply of the second pilot pressure to clutch release pressure chamber 31 of forward clutch 16 and auxiliary piston 33 of lock mechanism 32. In contrast, the clutch release pressure is supplied to clutch release pressure chamber 31 and auxiliary piston 33 from manual valve 57, so that forward clutch 16 is released naturally, and lock mechanism 32 is forced to be released from the lock state. Under this condition, three-directional linear solenoid valve 52 is controlled to produce a pressure sufficient for the release of locking.
Next, when select lever 58 is operated to the R position, manual valve 57 is switched to supply the brake apply pressure to brake oil chamber 11 of reverse brake 13, and thereby applies reverse brake 13, and thereby fix pinion carrier 8 to case-side member 9A. In this situation, three-directional linear solenoid valve 52 regulates the brake apply pressure to be sufficient to prevent slippage of reverse brake 13. The clutch release pressure is supplied to clutch release pressure chamber 31 and auxiliary piston 33 from manual valve 57 as in the P or N position, to force lock mechanism 32 to be released from the lock state, and release forward clutch 16. The oil in clutch apply pressure chamber 30 of forward clutch 16 is drained via manual valve 57. On-off switching solenoid valve 54 is configured so that the release pressure is drained from clutch release pressure chamber 31, when the release of forward clutch 16 or the lock release of lock mechanism 32 is detected, or when a predetermined period (period during which the release of forward clutch 16 or the lock release of lock mechanism 32 can be completed) has elapsed from start of supply of the release pressure.
Next, when select lever 58 is operated to the D position for forward drive, the clutch apply pressure flows from manual valve 57 to clutch apply pressure chamber 30 of forward clutch 16, and thereby causes forward clutch piston 21 to travel. In response to this travel, auxiliary piston 33 of lock mechanism 32 travels. When forward clutch 16 is completely applied and brake piston 12 stops after maximum travel, auxiliary piston 33 is locked in a lock position corresponding to this condition.
When a time period has elapsed to ensure the completion of the locking, three-directional linear solenoid valve 52 drains the clutch apply pressure from clutch apply pressure chamber 30. This eliminates the necessity of supply of the clutch apply pressure even while forward clutch 16 is being applied. When the D position is selected, manual valve 57 prevents the output of the clutch release pressure and thereby fails to supply the clutch release pressure to clutch release pressure chamber 31. Under this condition, the oil in brake oil chamber 11 of reverse brake 13 is drained via manual valve 57, so that reverse brake 13 is free in the released state.
The following describes effects produced by the automatic transmission clutch control apparatus according to the embodiment described above. The automatic transmission clutch control apparatus according to the embodiment includes lock mechanism 32 that locks forward clutch 16 in the clutch apply position in relation to forward clutch piston 21, and drain the clutch apply pressure oil from clutch apply pressure chamber 30 of forward clutch 16 while the clutch is being applied after the lock. This configuration eliminates the necessity of holding of the clutch oil pressure, and enhances the fuel efficiency by reduction of energy loss, because the high clutch oil pressure as a factor of friction loss is not applied to seal members 25a, 25b, 25c, etc., which are arranged between the members rotating relative to each other under the clutch apply pressure. This effect is significant because the clutch device is forward clutch 16 that is maintained in the applied state for a long time period of driving.
The feature that lock release valve 54 is provided which can output the clutch release pressure by bypassing the manual valve 57, serves to force lock mechanism 32 to be released from the lock state independently of the position of manual valve 57. For example, when one of the forward position and the reverse position is quickly shifted to the other so that reverse brake 13 and forward clutch 16 are simultaneously applied to establish an interlock condition, on-off switching solenoid valve 54 supplies the clutch release pressure (second pilot pressure) to clutch release pressure chamber 31 of forward clutch 16 and auxiliary piston 33 of lock mechanism 32, to force forward clutch 16 to be released. When a selecting operation is performed to shift a drive position to a non-drive position, on-off switching solenoid valve 54 supplies the clutch release pressure (second pilot pressure) to clutch release pressure chamber 31 of forward clutch 16 and auxiliary piston 33 of lock mechanism 32, to force forward clutch 16 to be released, and thereby prevent that driving is continued in the non-drive position in conflict with the selecting operation, and thereby prevent the driver from feeling uncomfortable and insecure.
Although the present invention has been described with reference to the embodiment, the present invention is not limited to the embodiment, but contains design changes within the scope of the concept of the invention.
For example, the selector according to the present invention is not limited to the select lever according to the embodiment, but may be a type that select buttons are pressed selectively. Lock mechanism 32 may be different from the embodiment. For example, the configuration described in Japanese Patent Application No. 2012-123864 filed by the present applicant.
The clutch device according to the present invention is not limited to continuously variable transmissions, but may be another device, or may be applied to a clutch device other than the forward clutch.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2012-212215 | Sep 2012 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2013/073734 | 9/4/2013 | WO | 00 |
