JP2010216501A - Piston structure for automatic transmission - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide piston structure for an automatic transmission restricted not to supply the oil pressure more than necessity. <P>SOLUTION: When the oil pressure for switching shift stage is supplied, each rib 22 of a first piston member 10 is moved toward a multiple disc clutch side by pushing force of a second cam surface 30 of a second piston member 12, resisting energizing force of a return spring 16, to rotate a body 20 of the first piston member 12 in a direction expressed with an arrow 50 when a first cam surface 26 of each rib 22 slips out of a second engagement groove 42 of a piston cover 14. A first cam surface 26 of each rib 22 is thereby engaged with a first engagement groove 40 of the piston cover 14 to fix the first piston member 10 (refer to Fig.2). As a result, even if supply of the oil pressure is stopped thereafter, the multiple disc clutch is maintained in the friction engagement state. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a piston structure of an automatic transmission that is reciprocated along an axial direction in order to engage or release a friction engagement element between a friction engagement element and an oil chamber.

  An automatic transmission used in an automobile or the like has a planetary gear composed of a sun gear, a ring gear, a pinion gear, and the like. Such switching of the characteristics of the power transmission mechanism (that is, speed change) is performed by fastening or releasing a friction engagement device such as a multi-plate clutch or a multi-plate brake.

  Generally, these multi-plate frictional engagement devices have a structure in which drive plates that are power input side plates and driven plates that are power output side plates are alternately arranged. Since the drive plate and the driven plate are clamped by the pressure from the pressure plate, power can be transmitted between these plates.

  Many automatic transmissions as described above use a one-way clutch in addition to the multi-plate frictional engagement element. For example, in a sports shift in which a shift of an automatic transmission is performed by a manual operation, there is a case where engagement control is performed such that a one-way clutch is locked and a multi-plate brake is also engaged when starting at the first speed.

  FIG. 7 is a cross-sectional view showing the structure of a conventional multi-plate frictional engagement element in which a one-way clutch is attached to the hub side.

  Referring to FIG. 7, a large number of sprags 104 are arranged between inner race 100 and hub (outer race) 102, and these members constitute a one-way clutch. In the state where the sprags 104 are arranged as shown, for example, when the hub 102 rotates in the lock direction A (clockwise in FIG. 7) as in the first speed acceleration, the sprags 104 rise and the inner race 100 And the hub 102 are locked, and the rotation of the hub 102 is locked. However, for example, when the hub 102 rotates in the direction opposite to the lock direction A as in the first speed reduction, the sprag 104 lies down and the hub 102 can rotate.

  On the other hand, between the hub 102 and the mission case 106, drive plates 108 and driven plates 110 are alternately arranged from the front surface to the back surface of FIG. The drive plate 108 is spline-fitted with the hub 102, and the driven plate 110 is spline-fitted with the transmission case 106. The hub 102, the transmission case 106, and the friction plates 108 and 110 constitute a brake. The inner race 100 is fixed to the mission case 106.

  In the above configuration, consider a case where the hub 102 rotates in the lock direction A with the brake engaged.

  When the hub 102 rotates in the lock direction A, the sprag 104 starts to rise. The one-way clutch does not act to restrict (that is, lock) the rotation of the hub 102 unless the sprag 104 rises. In other words, the regulating force of the one-way clutch is generated when the hub 102 rotates by a rotation amount corresponding to the rising amount of the sprag 104. Therefore, the rotation of the hub 102 is regulated by the regulation force of either the one-way clutch or the brake. As a result, the brake regulating force may act before the one-way clutch regulating force is generated.

  That is, in FIG. 7, when the hub 102 rotates in the lock direction A, the clearance a (so-called looseness) in the fitting region between the hub 102 and the drive plate 108 is clogged, and the drive plate 108 also rotates in the lock direction A. At this time, since the drive plate 108 and the driven plate 110 are in the fastening state, the driven plate 110 also rotates in the lock direction A. Accordingly, the clearance b, which is a backlash in the fitting region of the driven plate 110 and the transmission case 106, is also clogged, so that the protruding portion of the driven plate 110 contacts the side of the spline groove. Therefore, a load corresponding to the torque of the hub 102 and the degree of fastening of the plates 108 and 110 is applied to the protrusions of the friction plates 108 and 110. At the time of all development progress with a large amount of accelerator depression, the load becomes very large, and the driven plate 110 may be fatigued and its durability may be reduced. Considering that such loads are frequently applied, the approach of improving the durability and strength of the friction plate itself by using a friction plate made of an expensive material will increase the cost of the automatic transmission. It is not preferable.

  Therefore, Patent Document 1 proposes a technique for effectively reducing a load applied to a friction plate of a friction engagement device in an automatic transmission and suppressing fatigue of the friction plate.

  The automatic transmission described in Patent Document 1 includes first and second plates, and is provided in a fitting region in which a spline groove formed in the drum and a protrusion of the second plate are fitted, Biasing means for urging the protrusion of the second plate in the fitting region in a direction opposite to the locking direction in which the one-way clutch acts is provided.

Japanese Patent Laid-Open No. 2000-170792

  By the way, a shift engagement element in an automatic transmission is generally a friction engagement of a multi-plate clutch by hydraulic supply.

  In such an automatic transmission, efforts are made to improve shift shock and responsiveness by adjusting the hydraulic pressure supply during shifting. However, even after the end of shifting, it contributes to torque transmission to the output shaft, but it is necessary to continue supplying hydraulic pressure. As a result, a large amount of lubricating oil is required in the automatic transmission, which has a great influence on cost and weight increase.

  The present invention has been made in view of the above technical background, and an object of the present invention is to provide a piston structure of an automatic transmission that does not need to supply hydraulic pressure more than necessary.

  In order to achieve the above object, the present inventor has conceived that when shifting engagement is performed, the pressure is adjusted by hydraulic pressure as in the past, and the piston is mechanically fixed after the engagement is completed.

  The specific invention based on this idea is as follows.

  A piston structure of an automatic transmission according to the present invention is a piston of an automatic transmission that is reciprocated along an axial direction to engage or release a friction engagement element between a friction engagement element and an oil chamber. A first piston member disposed on the frictional engagement element side, displaceable along the axial direction and rotatable about the axis, and disposed on the oil chamber side; A second piston member provided so as to be displaceable along the first piston member, a piston cover provided on the outer peripheral side of the first and second piston members, and the first piston member on the second piston member side. And the first piston member includes a main body having an annular shape and a plurality of ribs formed on the outer peripheral surface of the main body at an equal circumference. , Second piston member side end of each rib Protrudes toward the second piston member side from the second piston side end surface of the main body, and the protruding end portion is a first cam surface inclined outward in the rotation direction of the main body. The piston member has an annular shape, and the end surface on the first piston member side is a second cam surface having a concavo-convex shape in which peaks and valleys are continuous along the circumferential direction, and the piston cover A first engagement groove having an uneven shape corresponding to the shape of the protruding end portion of the rib is formed along the circumferential direction on the first piston member side end surface. In addition, the same number of second engagement grooves as the ribs are formed on the circumferential surface in a uniform manner along the axial direction, and the first engagement grooves are circumferentially formed by the second engagement grooves. The hydraulic pressure is supplied to switch the friction engagement element from the released state to the engaged state. The ribs of the first piston member are moved to the friction engagement element side against the urging force of the urging means by the pressing force of the second cam surface of the second piston member, When the first cam surface of each rib comes out of the second engagement groove of the piston cover, the main body of the first piston member rotates, whereby the first cam surface of each rib becomes the piston. When the first piston member is fixed by engaging with the first engagement groove of the cover, and hydraulic pressure is supplied from the fixed state of the first piston member, the second piston member The ribs of the first piston member are moved toward the friction engagement element against the biasing force of the biasing means due to the pressing force of the cam surface, and come out of the first engagement groove of the piston cover. Sometimes the body of the first piston member rotates, thereby The first cam surface of each rib is engaged with the second engagement groove of the piston cover, and the fixed state of the first piston member is released.

  In the above configuration, when the hydraulic pressure is supplied to switch the friction engagement element from the released state to the engaged state, each rib of the first piston member is caused by the pressing force of the second cam surface of the second piston member. The body of the first piston member moves to the friction engagement element side against the biasing force of the biasing means, and the first cam surface of each rib comes out of the second engagement groove of the piston cover. Is rotated, whereby the first cam surface of each rib is engaged with the first engagement groove of the piston cover, and the first piston member is fixed. As a result, the engagement state of the friction engagement element is maintained even if the hydraulic pressure supply is subsequently stopped.

  When the hydraulic pressure is supplied from the fixed state of the first piston member, the ribs of the first piston member become the urging force of the urging means by the pressing force of the second cam surface of the second piston member. The main body of the first piston member is rotated when the first cam surface of each rib comes out of the first engagement groove of the piston cover by moving to the friction engagement element side. The first cam surface of the rib engages with the second engagement groove of the piston cover, and the fixed state of the first piston member is released.

  According to the present invention, it is not necessary to supply hydraulic pressure more than necessary to maintain the engagement state of the friction engagement element.

It is a figure which shows the motion of the piston structure of the automatic transmission concerning embodiment of this invention schematically. FIG. 2 is a diagram schematically showing the movement of the piston structure of the automatic transmission according to the embodiment of the present invention, and is a continuation of FIG. 1. FIG. 3 is a diagram schematically showing the movement of the piston structure of the automatic transmission according to the embodiment of the present invention, and is a continuation of FIG. 2. It is an outer periphery expanded view which shows the structure of a 1st piston member. It is an outer periphery expansion | deployment figure which shows the structure of a 2nd piston member. It is an inner periphery expanded view which shows the structure of a piston cover. It is sectional drawing which showed the structure of the conventional multi-plate friction engagement element with which the one-way clutch was attached to the hub side.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

<Configuration>
1 to 3 are diagrams schematically showing the movement of the piston structure of the automatic transmission according to the embodiment of the present invention.

  Referring to FIGS. 1 to 3, the piston structure of the automatic transmission according to the present embodiment extends along the axial direction in order to frictionally engage or release the multi-plate clutch between the multi-plate clutch and the oil chamber. A first piston member 10 disposed on the multi-plate clutch side, displaceable along the axial direction and rotatable about the axis, and disposed on the oil chamber side. The second piston member 12 provided to be displaceable along the axial direction, the piston cover 14 provided on the outer peripheral side of the first and second piston members 10, 12, and the first piston member 10. And a return spring 16 that urges toward the second piston member 12 side.

  FIG. 4 is an outer peripheral development view showing the configuration of the first piston member 10.

  Referring to FIG. 4, the first piston member 10 includes a main body 20 having an annular shape, and a plurality of (four in the present embodiment) formed on the outer peripheral surface of the main body 20 at an equal circumference. The rib 22 is provided.

  The end of each rib 22 on the second piston member 12 side protrudes from the end surface of the main body 20 on the second piston member 12 side toward the second piston member 12. The protruding end portion is a first cam surface 26 that is inclined outwardly in the rotation direction 24 of the main body 20.

  FIG. 5 is an outer peripheral development view showing the configuration of the second piston member 12.

  Referring to FIG. 5, the second piston member 12 has an annular shape concentric with the main body 20 of the first piston member 10. The end surface on the first piston member 10 side of the second piston member 12 is a second cam surface 30 having an uneven shape in which peaks and valleys are continuous along the circumferential direction.

  FIG. 6 is an inner peripheral development view showing the configuration of the piston cover 14.

  With reference to FIG. 6, the piston cover 14 has an annular shape concentric with the main body 20 of the first piston member 10 and the second piston member 12. A first engagement groove 40 having an uneven shape corresponding to the shape of the protruding end portion of the rib 22 is formed along the circumferential direction on the end surface of the piston cover 14 on the first piston member 10 side. Further, the same number of second engaging grooves 42 as the ribs 22 are formed on the inner peripheral surface of the piston cover 14 along the axial direction so as to have a uniform circumference. The first engagement groove 40 is divided in the circumferential direction by the second engagement groove 42.

<Operation>
Now, as shown in FIG. 1A, the first cam surface 26 of each rib 22 of the first piston member 10 engages with the second engagement groove 42 of the piston cover 14, and the first piston. Consider a case where the member 10 is fixed and the fixed state of the first piston member 10 is released. At this time, the supply of hydraulic pressure is stopped.

  When the N-speed shift is started in the state of FIG. 1A, hydraulic pressure is supplied from the oil chamber. Then, as shown in FIG. 1B, the first piston member 10 resists the urging force of the return spring 16 by the pressing force of the second cam surface 30 of the second piston member 12, and the multi-plate clutch side Move to. Along with this movement, the multi-plate clutch is frictionally engaged. At this time, when the first cam surface 26 of each rib 22 of the first piston member 10 exits the second engagement groove 42 of the piston cover 14, the main body 20 of the first piston member 10 moves in the direction of the arrow 50. Rotate. Then, as shown in FIG. 2, the first cam surface 26 of each rib 22 of the first piston member 10 is engaged with the first engagement groove 40 of the piston cover 14, and the first piston member 10 is Fixed.

  Thereafter, the supply of hydraulic pressure from the oil chamber is stopped. At this time, the first piston member 10 is fixed by the first cam surface 26 of each rib 22 of the first piston member 10 engaging the first engagement groove 40 of the piston cover 14 as described above. Therefore, the friction engagement state of the multi-plate clutch is maintained.

  When the N + 1 shift is started in the state of FIG. 2, the hydraulic pressure supply from the oil chamber is resumed. Then, as shown in FIG. 3A, each rib 22 of the first piston member 10 resists the urging force of the return spring 16 by the pressing force of the second cam surface 30 of the second piston member 12. Move to the multi-plate clutch. Along with this movement, when the first cam surface 26 of each rib 22 of the first piston member 10 exits the first engagement groove 40 of the piston cover 14, the main body 20 of the first piston member 10 is moved. It rotates in the direction of arrow 50. Then, as shown in FIG. 3 (B), each rib 22 of the first piston member 10 engages with the second engagement groove 42 of the piston cover 14, and the first piston member 10 is fixed. Is released.

  In order to release the fixed state of the first piston member 10 as described above, it is necessary to push the first piston member 10 into the multi-plate clutch side. However, when the hydraulic pressure is supplied, the multi-plate clutch is fixed. The required amount of sliding is secured by flexing the elastic snap ring.

<Action and effect>
According to the present embodiment, the following operations and effects are achieved.

  When hydraulic pressure is supplied to switch the multi-plate clutch from the disengaged state to the engaged state (that is, the gear position is switched), the first piston is pressed by the pressing force of the second cam surface 30 of the second piston member 12. Each rib 22 of the member 10 moves toward the multi-plate clutch against the urging force of the return spring 16, and the first cam surface 26 of each rib 22 slips out of the second engagement groove 42 of the piston cover 14. The main body 20 of the first piston member 10 rotates, whereby the first cam surface 26 of each rib 22 engages with the first engagement groove 40 of the piston cover 14 and the first piston member. As a result of fixing 10, the friction engagement state of the multi-plate clutch is maintained even if the hydraulic pressure supply is subsequently stopped. When hydraulic pressure is supplied from this state, each rib 22 of the first piston member 10 resists the urging force of the return spring 16 by the pressing force of the second cam surface 30 of the second piston member 12. When the first cam surface 26 of each rib 22 moves out of the first engagement groove 40 of the piston cover 14 by moving to the clutch side, the main body 20 of the first piston member 10 rotates, thereby The first cam surface 26 of the rib 22 engages with the second engagement groove 42 of the piston cover 14 and the fixed state of the first piston member 10 is released.

  That is, when the gear shift is engaged, the pressure is regulated by hydraulic pressure as before, and the first piston member 10 is mechanically fixed after the friction engagement of the multi-plate clutch is completed. It is possible to stop the supply of hydraulic pressure after completion, and the amount of oil that has been continuously supplied can be reduced. That is, it is not necessary to supply hydraulic pressure more than necessary to maintain the friction engagement state of the multi-plate clutch. Therefore, the amount of oil filling the automatic transmission is reduced, leading to a reduction in the weight of the automatic transmission and a reduction in oil cost.

  In addition, in the FR (Front engine Rear drive) HV (Hybrid Vehicle) transmission, an electric oil pump is added to supply the hydraulic pressure necessary for torque transmission when the engine is stopped, but this piston structure reduces the number of parts. Can also contribute.

  The present invention is not limited to the above embodiment.

  For example, in the above-described embodiment, an example in which the piston structure of the automatic transmission according to the present invention is applied to bring the multi-plate clutch into an engaged state or a released state has been described. However, the present invention is not limited to such a configuration. Even if the piston structure of the automatic transmission according to the present invention is applied to bring the multi-plate brake into an engaged state or a released state, the object of the present invention can be sufficiently achieved.

  It goes without saying that various design changes and modifications can be made within the scope of the claims attached to this specification.

10 first piston member 12 second piston member 14 piston cover 16 return spring 20 main body 22 rib 26 first cam surface 30 second cam surface 40 first engagement groove 42 second engagement groove

Claims (1)

A piston structure of an automatic transmission that is reciprocated along an axial direction to engage or disengage a friction engagement element between a friction engagement element and an oil chamber,
A first piston member disposed on the friction engagement element side and provided so as to be displaceable along the axial direction and rotatable about the axis;
A second piston member disposed on the oil chamber side and provided to be displaceable along the axial direction;
A piston cover provided on the outer peripheral side of the first and second piston members;
Biasing means for biasing the first piston member toward the second piston member,
The first piston member includes a main body having an annular shape and a plurality of ribs formed on the outer peripheral surface of the main body so as to have a uniform circumference. , Projecting toward the second piston member side from the second piston side end surface of the main body, the projecting end portion is a first cam surface inclined outward in the rotation direction of the main body,
The second piston member has an annular shape, and the first piston member side end surface is a second cam surface having an uneven shape in which peaks and valleys are continuous along the circumferential direction,
The piston cover has an annular shape, and a first engagement groove having an uneven shape corresponding to the shape of the protruding end portion of the rib along the circumferential direction on the first piston member side end surface. And the same number of second engaging grooves as the ribs are formed on the circumferential surface in a uniform manner along the axial direction. The first engaging grooves are second engaging grooves. Is divided in the circumferential direction by
When the hydraulic pressure is supplied to switch the friction engagement element from the released state to the engaged state, the ribs of the first piston member are moved by the pressing force of the second cam surface of the second piston member. When the first cam surface of each of the ribs moves out of the second engagement groove of the piston cover by moving toward the friction engagement element side against the biasing force of the biasing means, the first The main body of the piston member rotates, whereby the first cam surface of each rib engages with the first engagement groove of the piston cover, and the first piston member is fixed.
When hydraulic pressure is supplied from the fixed state of the first piston member, each rib of the first piston member is biased by the biasing means by the pressing force of the second cam surface of the second piston member. The main body of the first piston member is rotated when it moves to the friction engagement element side against the first engagement groove of the piston cover and thereby the first of the ribs A piston structure of an automatic transmission in which a cam surface is engaged with a second engagement groove of the piston cover to release the fixed state of the first piston member.

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