JP2006220264A - Fluid type torque transmission device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve a response property for lockup operation of a lockup unit of a fluid type torque transmission device when the lockup unit is reversed. <P>SOLUTION: A torque converter 1 comprises a front cover 2 in which torque is entered, an impeller shell 9 which forms a fluid chamber together with the front cover 2, an impeller 3 having a plurality of impeller blades 10 in the impeller shell 9, a turbine 4 oppositely arranged on the impeller blade 10, and a lockup clutch 7 capable of connecting the front cover 2 and turbine 4. A step section 50 which makes a flow direction of surrounding fluid change is formed on an inner peripheral side of either of the front cover 2 and impeller shell 9. The step section 50 has a first inner peripheral surface 51, a second inner peripheral surface 52 which is formed on an axial transmission side of the first inner peripheral surface 51 and is greater than a bore of the first inner peripheral surface 51, and a step surface 53 formed between the first and second inner peripheral surfaces 51 and 52. An angle between the step surface 53 and second inner peripheral surface 52 is less than 90°. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a hydrodynamic torque transmission device, and more particularly to a hydrodynamic torque transmission device including a lockup device that is activated by a change in hydraulic pressure in a fluid chamber.

  As a fluid torque transmission device, a torque converter used in a vehicle drive system is known. The torque converter is a device that transmits the torque from the engine to the transmission side via fluid such as internal hydraulic oil, and is mainly fixed to the front cover to which the torque from the engine is input and to the transmission side of the front cover And an impeller that forms a fluid chamber together with the front cover, a turbine that is disposed to face the engine side of the impeller and outputs torque to the transmission side, and is disposed between the inner peripheral portion of the impeller and the inner peripheral portion of the turbine. A stator that rectifies the flow of hydraulic oil from the turbine toward the impeller, and a lockup device that is disposed in a space between the turbine and the front cover are provided.

  The lockup device is a device for directly transmitting torque from the front cover to the turbine by mechanically connecting the front cover and the turbine. The lockup device includes, for example, a disk-like piston that is connected by being pressed against the friction surface of the front cover, and an elastic connection mechanism that transmits torque between the piston and the turbine. The piston has a friction coupling portion on the outer peripheral portion that can be frictionally coupled to the front cover. The piston divides the space between the front cover and the turbine into a first hydraulic chamber on the front cover side and a second hydraulic chamber on the turbine side, and a differential pressure between the first hydraulic chamber and the second hydraulic chamber. Can be moved in the axial direction (see, for example, Patent Document 1).

The operation of the lockup device described above will be described. At the time of torque transmission from the engine side to the transmission side, hydraulic oil is supplied from the center side to the first hydraulic chamber, and the hydraulic fluid flows to the outer peripheral side and further flows into the fluid working chamber of the torque converter. Therefore, the piston is separated from the front cover in the axial direction (clutch release state). During the lockup coupling operation, the hydraulic circuit is switched, and the hydraulic oil in the first hydraulic chamber is discharged to the inner peripheral side. For this reason, the hydraulic pressure in the first hydraulic chamber becomes lower than the hydraulic pressure in the second hydraulic chamber, and the piston approaches the front cover side. As a result, the friction coupling portion of the piston is strongly pressed against the front cover (clutch coupling state), and torque is directly transmitted from the front cover to the turbine.
JP 2002-147564 A

  By adopting the lock-up device, it is possible to improve fuel efficiency, which has been regarded as a drawback of conventional automatic vehicles, and to improve the effectiveness of engine braking. Furthermore, with the shift to electronic control of transmission control, there is an increasing tendency to use lockup devices in a wide range, such as lockup control from the first speed and slipup slip control. In particular, attempts have been made to improve the effectiveness of the engine brake by operating a lock-up device when the engine brake is used.

  However, if the lock-up operation area is extended to the reverse drive area when the engine brake is used (a state where the output rotation speed is larger than the input rotation speed, so-called coast state), the problem of the deterioration of the operation responsiveness of the lock-up device becomes remarkable. Become. Generally, whether or not the operation responsiveness of the lockup device is good or bad is determined by the time until the lockup clutch is engaged after switching the lockup circuit. At the time of reverse driving, the rotational speed of the turbine is higher than the rotational speed of the impeller, so that the hydraulic oil is easily discharged from the torus to the outer peripheral side. When the hydraulic oil in the first hydraulic chamber is discharged in this state, the hydraulic oil discharged from the torus to the outer peripheral side flows along the impeller shell and the inner peripheral side wall surface of the front cover to the lockup device side, and the front cover and the piston And flows into the first hydraulic chamber through a flow path formed between the two. As a result, the hydraulic pressure in the first hydraulic chamber becomes high, and the operation responsiveness of the lockup device is deteriorated.

  An object of the present invention is to improve lockup operation responsiveness during reverse driving in a lockup device of a fluid torque transmission device.

  The fluid torque transmission device according to claim 1 is for transmitting torque from the engine side to the transmission side. The hydrodynamic torque transmitting device includes a front cover to which torque is input from the engine side, an impeller shell that is disposed on the transmission side of the front cover and forms a fluid chamber together with the front cover, and a plurality of provided in the impeller shell An impeller having an impeller blade, a turbine disposed opposite to the impeller blade in a fluid chamber, and a piston that can be connected to and disconnected from the front cover, and the front cover and the turbine can be mechanically connected. And a lock-up device. A step portion for changing the flow of the surrounding fluid is formed on the inner peripheral side of one of the front cover and the impeller shell. The step portion includes a first inner peripheral surface, a second inner peripheral surface formed on the axial transmission side of the first inner peripheral surface and having a larger inner diameter than the first inner peripheral surface, and the first and second inner peripheral surfaces. And a step surface formed therebetween. The angle formed between the step surface and the second inner peripheral surface is smaller than 90 °.

  In this fluid torque transmission device, the angle formed between the step surface and the second inner peripheral surface is smaller than 90 °, so the flow of fluid around the inner peripheral side of the front cover and the impeller shell is caused by the step portion. Can be reversed. As a result, the hydraulic pressure in the hydraulic chamber on the engine side of the piston can be kept lower than the hydraulic pressure in the hydraulic chamber on the transmission side during the lockup coupling operation. Thereby, in this fluid type torque transmission device, it is possible to improve the operation responsiveness of the lockup device during reverse driving.

  According to a second aspect of the present invention, in the first aspect, the angle formed between the step surface and the second inner peripheral surface is 45 ° or more.

  In this fluid torque transmission device, the angle formed between the step surface and the second inner peripheral surface is 45 ° or more, so the step portion can be easily formed.

  According to a third aspect of the present invention, in the fluid torque transmission device according to the first or second aspect, the outer peripheral side cylindrical portion extending toward the axial transmission side is provided on the outer peripheral side of the piston. The distal end portion on the axial transmission side of the outer peripheral cylindrical portion is disposed on the axial engine side of the stepped portion.

  In this fluid type torque transmitting device, the outer cylindrical portion is disposed on the axial engine side of the step portion, so that the fluid whose flow is reversed by the step portion is between the outer cylindrical portion and the front cover. It is possible to reliably inhibit the flow into the flow path, and to reliably maintain a state in which the hydraulic pressure in the hydraulic chamber on the engine side of the piston is lower than the hydraulic pressure in the hydraulic chamber on the transmission side during the lockup connection operation.

  The fluid torque transmission device according to claim 4 is the fluid torque transmission device according to any one of claims 1 to 3, wherein the first gap formed between the first inner peripheral surface and the outer peripheral side cylindrical portion is a stepped portion. It is smaller than the second gap as the shortest gap formed between the turbine.

  In this fluid torque transmission device, since the first gap is smaller than the second gap, it is possible to more reliably inhibit the fluid from flowing into the flow path between the outer peripheral cylindrical portion and the front cover.

  The fluid type torque transmitting device according to claim 5 is the taper shape according to any one of claims 3 to 4, wherein the tip end portion of the outer cylindrical portion gradually protrudes in the axial direction as it goes to the outer peripheral side over the entire circumference. have.

  In this fluid torque transmission device, the tip of the outer cylindrical portion has a tapered shape, so that the fluid reversed at the stepped portion easily flows into the transmission side of the piston. Here, the taper shape means that an angle formed between the end surface of the distal end portion of the outer cylindrical portion and the rotating shaft of the fluid torque transmitting device is smaller than at least 90 °.

  A fluid type torque transmission device according to a sixth aspect is for transmitting torque from the engine side to the transmission side. The hydrodynamic torque transmitting device includes a front cover to which torque is input from the engine side, an impeller shell that is disposed on the transmission side of the front cover and forms a fluid chamber together with the front cover, and a plurality of provided in the impeller shell An impeller having an impeller blade, a turbine disposed opposite to the impeller blade in the fluid chamber, and a piston that can be connected to and disconnected from the front cover, and the front cover and the turbine can be mechanically connected. And a lock-up device. A step portion for changing the flow direction of the surrounding fluid is formed on the inner peripheral side of at least one of the front cover and the impeller shell. The step portion includes a first inner peripheral surface, a second inner peripheral surface formed on the axial transmission side of the first inner peripheral surface and having a larger inner diameter than the first inner peripheral surface, and the first and second inner peripheral surfaces. And a stepped surface formed therebetween. On the outer peripheral side of the piston, there is an outer peripheral cylindrical portion extending toward the axial transmission side. The distal end portion on the axial transmission side of the outer peripheral cylindrical portion is disposed on the axial engine side of the stepped portion. The tip of the outer cylindrical portion has a taper shape that gradually protrudes in the axial direction as it goes to the outer peripheral side. The angle formed between the step surface and the second inner peripheral surface is 135 ° or less.

  In this fluid torque transmission device, the tip of the outer cylindrical portion has a tapered shape, so that the fluid reversed at the stepped portion easily flows into the transmission side of the piston. Here, the taper shape means that an angle formed between the end surface of the distal end portion of the outer cylindrical portion and the rotating shaft of the fluid torque transmitting device is smaller than at least 90 °.

  According to a seventh aspect of the present invention, in the fluid type torque transmission device according to the sixth aspect, an angle formed between the step surface and the second inner peripheral surface is 45 ° or more.

  In this fluid torque transmission device, the angle formed between the step surface and the second inner peripheral surface is 45 ° or more, so the step portion can be easily formed.

  According to an eighth aspect of the present invention, in the fluid type torque transmission device according to the sixth or seventh aspect, the first gap formed between the first inner peripheral surface and the outer peripheral tubular portion is a gap between the stepped portion and the turbine. It is smaller than the second gap as the shortest gap formed between them.

  In this fluid torque transmission device, since the first gap is smaller than the second gap, it is possible to more reliably inhibit the fluid from flowing into the flow path between the outer peripheral cylindrical portion and the front cover.

  In the fluid type torque transmission device according to the present invention, it is possible to improve the lock-up operation responsiveness during reverse driving.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1. Overall Configuration of Torque Converter FIG. 1 is a schematic longitudinal sectional view of a torque converter 1 as a fluid torque transmission device according to an embodiment of the present invention. 1 is the rotation axis of the torque converter 1. As shown in FIG. 1, the torque converter 1 forms a hydraulic oil chamber with a front cover 2 and an impeller shell 9 fixed to the outer peripheral side protruding portion 8 of the front cover 2. On the inner peripheral side around the joint between the front cover 2 and the impeller shell 9, a step 50 described later is formed. The front cover 2 can be attached to engine-side components (not shown) so that torque from the engine can be input. A plurality of impeller blades 10 are fixed inside the impeller shell 9. An impeller 3 is constituted by the impeller shell 9 and the impeller blade 10. A turbine 4 is disposed at a position facing the impeller 3 in the hydraulic oil chamber. The turbine 4 includes a turbine shell 11 and a plurality of turbine blades 12 fixed on the turbine shell 11. An inner peripheral end portion of the turbine shell 11 is fixed to a flange 15 of the turbine hub 13 via a rivet 14. The turbine hub 13 has a spline groove 20 that engages with a main drive shaft (not shown) of the transmission on the inner periphery.

  A stator 5 is disposed between the inner periphery of the impeller 3 and the inner periphery of the turbine 4. The stator 5 adjusts the direction of hydraulic fluid returned from the turbine 4 to the impeller 3 and is supported by a fixed shaft (not shown) via a one-way clutch 6. The lock-up clutch 7 (lock-up device) is disposed in a space between the front cover 2 and the turbine 4 and is a device for mechanically connecting the front cover 2 and the turbine 4. The lockup clutch 7 mainly includes a piston 22 and an elastic coupling mechanism 40 for elastically coupling the piston 22 to the turbine 4.

  The piston 22 is a disk-shaped member, and divides the space between the front cover 2 and the turbine shell 11 into a first hydraulic chamber A on the front cover 2 side and a second hydraulic chamber B on the turbine 4 side. Are arranged as follows. The piston 22 is made of, for example, a thin sheet metal. The piston 22 has an inner peripheral cylindrical portion 23 extending toward the transmission side on the inner peripheral side. As shown in FIG. 2, the inner peripheral cylindrical portion 23 is supported on the outer peripheral surface 19 of the cylindrical portion 16 formed on the outermost periphery of the flange 15 of the turbine hub 13 so as to be relatively movable in the axial direction and the circumferential direction. Has been. That is, the inner peripheral surface 25 of the inner peripheral cylindrical portion 23 is in contact with the outer peripheral surface 19 of the cylindrical portion 16. An annular groove 17 is formed on the outer peripheral surface 19 of the cylindrical portion 16 at an intermediate position in the radial direction. A seal ring 18 is disposed in the annular groove 17, and the seal ring 18 is in contact with the inner peripheral surface 25 of the inner peripheral side tubular portion 23. In this manner, the seal ring 18 seals the inner peripheral portions of the first hydraulic chamber A and the second hydraulic chamber B.

  An outer peripheral cylindrical portion 24 extending to the transmission side is formed on the outer peripheral portion of the piston 22. An annular friction facing 35 (friction engaging portion) is provided on the engine side in the outer peripheral portion of the piston 22. The friction facing 35 is opposed to an annular flat friction surface 2 a formed on the inner periphery of the front cover 2. By the engagement between the friction facing 35 and the friction surface 2a, the outer peripheral portions of the first hydraulic chamber A and the second hydraulic chamber B are sealed.

  The elastic coupling mechanism 40 is disposed between the piston 22 and the turbine 4, more specifically, between the outer peripheral portion of the piston 22 and the outer peripheral portion of the turbine shell 11. The elastic coupling mechanism 40 includes a retaining plate 27 as a drive side member, a driven plate 33 as a driven side member, and a plurality of coil springs 32 disposed between the plates 27 and 33. The retaining plate 27 is an annular plate member disposed on the outer peripheral side of the piston 22, that is, on the inner peripheral side of the outer peripheral side tubular part 24. The inner peripheral portion of the retaining plate 27 is fixed to the piston 22 by a plurality of rivets (not shown). The retaining plate 27 is a member for holding the coil spring 32 and for transmitting torque by engaging with both sides of the coil spring 32 in the circumferential direction. The retaining plate 27 has holding portions 28 and 29 that respectively support the outer peripheral side and the inner peripheral side of the plurality of coil springs 32 arranged in the circumferential direction. The inner peripheral holding portion 29 is formed by being cut and raised from the disc-shaped portion of the retaining plate 27. Further, the retaining plate 27 has engaging portions 30 and 31 for supporting both sides of each coil spring 32 in the circumferential direction. The engaging portions 30 and 31 are formed by being cut and raised from the disc-shaped portion of the retaining plate 27. The driven plate 33 is an annular plate member fixed to the rear surface of the outer peripheral portion of the turbine shell 11. The driven plate 33 is formed with a plurality of claw portions 34 arranged in the circumferential direction and extending toward the engine side. The claw portions 34 are engaged with both ends of each coil spring 32 in the circumferential direction. Thereby, torque transmitted from the retaining plate 27 is transmitted to the driven plate 33 via the coil spring 32.

2. Structure around the stepped portion FIG. 2 is a partial longitudinal sectional view around the stepped portion. A stepped portion 50 for changing the flow direction of the surrounding fluid is formed over the entire circumference on the inner circumferential side around the joint between the outer circumferential side protruding portion 8 of the front cover 2 and the impeller shell 9. Specifically, the step portion 50 is for reversing the flow of hydraulic oil from the transmission side to the engine side around the inner periphery of the front cover 2 and the impeller shell 9. Specifically, on the engine side of the impeller shell 9, a cylindrical second outer peripheral cylindrical portion 9 a having a larger diameter than the outer peripheral protruding portion 8 is provided. The second outer peripheral cylindrical portion 9a is fitted on the outer peripheral side of the outer peripheral protruding portion 8, and the tip of the second outer peripheral cylindrical portion 9a and the outer peripheral surface of the outer peripheral protruding portion 8 are fixed by welding. Yes. The step portion 50 includes a first inner peripheral surface 51, a second inner peripheral surface 52, and a step surface 53. The first inner peripheral surface 51 is formed on the inner peripheral side of the outer peripheral side protruding portion 8 over the entire periphery. The second inner circumferential surface 52 is formed over the entire circumference on the inner circumferential side of the second outer circumferential cylindrical portion 9 a and has an inner diameter larger than that of the first inner circumferential surface 51. The step surface 53 is formed between the first inner peripheral surface 51 and the second inner peripheral surface 52. More specifically, the step surface 53 is an end surface of the axial end portion 8a of the outer peripheral projection 8. If the angle formed between the step surface 53 and the second inner peripheral surface 52 is α ₁ [°], the step surface 53 has a range of α ₁ <135 °, preferably 45 ° ≦ α ₁ <90 °. It is provided in a range, more preferably in a range of 60 ° ≦ α ₁ ≦ 80 °.

  The radial dimension of the step surface 53 is preferably set large. In this embodiment, the radial dimension of the step surface 53 can be set large by increasing the thickness of the axial end 8a. The thickness of the axial end 8a is desirably secured at least 1 mm or more.

  The piston 22 has a stepped portion 50 so that the hydraulic oil inverted by the stepped portion 50 does not flow into the first hydraulic chamber A through the flow path 60 between the outer peripheral side protruding portion 8 and the outer peripheral side cylindrical portion 24. It is arranged on the engine side. Specifically, the distal end portion on the transmission side of the outer peripheral side cylindrical portion 24 of the piston 22 is disposed on the axial direction engine side of the step portion 50. More specifically, the distance from the tip P formed between the step surface 53 and the first inner peripheral surface 51 to the tip Q of the outer cylindrical portion 24 on the axial engine side is the axial distance D [ mm], the piston 22 is arranged so that D ≧ 0 mm when the piston 22 is moved to the axial transmission side when the lockup is released.

The tip of the outer cylindrical portion 24 has a tapered shape that gradually protrudes in the axial direction toward the outer peripheral side over the entire circumference. Assuming that the angle formed between the end surface 24a of the distal end portion of the outer cylindrical portion 24 and the rotation axis OO is α ₂ [°], the end surface 24a has a range of α ₂ <90 °, more preferably 45. It is provided to be in a range of ° ≦ α ₂ ≦ 80 °.

A first gap L ₁ [mm] is formed between the outer peripheral side protruding portion 8 of the front cover 2 and the outer peripheral side cylindrical portion 24 of the piston 22 in the radial direction. A second gap L ₂ [mm] is formed between the tip P formed between the step surface 53 and the first inner peripheral surface 51 and the turbine shell 11. The second gap L ₂ is the shortest gap between the tip P and the turbine shell 11. Further, a third gap L ₃ [mm] is formed between the outermost peripheral end of the turbine shell 11 and the second outer peripheral cylindrical portion 9a of the impeller shell 9 in the radial direction. The front cover 2, the impeller 3, the turbine 4, the piston 22, and the like are provided so as to satisfy L ₁ ≦ L ₂ and L ₃ ≦ L ₂ .

3. Operation The operation of the torque converter 1 described above will be described. When torque is input from the engine to the front cover 2, the impeller 3 rotates together with the front cover 2. Thereby, hydraulic fluid flows from the impeller 3 to the turbine 4 to rotate the turbine 4. Torque transmitted to the turbine 4 is transmitted to a main drive shaft (not shown). When the lockup is released, hydraulic oil is supplied into the first hydraulic chamber A from the inner peripheral side. The hydraulic oil flows radially outward in the first hydraulic chamber A, and further passes through the flow path 60 between the outer peripheral cylindrical portion 24 of the piston 22 and the outer peripheral protruding portion 8 of the front cover 2 in the axial transmission. To the side and finally into the fluid working chamber (torus). As a result, the hydraulic pressure in the first hydraulic chamber A becomes higher than the hydraulic pressure in the second hydraulic chamber B, and the piston 22 keeps moving most to the axial transmission side. As a result, the friction facing 35 of the piston 22 is separated from the friction surface 2a of the front cover 2, and the lockup release state is maintained.

  At the time of lockup connection, the hydraulic circuit is switched, and the hydraulic oil in the first hydraulic chamber A is discharged from the inner peripheral portion. Therefore, the hydraulic pressure in the first hydraulic chamber A is lower than the hydraulic pressure in the second hydraulic chamber B. As a result, the piston 22 moves to the front cover 2 side, the friction facing 35 is strongly pressed against the friction surface 2a of the front cover 2, and a lock-up connection state is established.

  Here, the flow of hydraulic oil when a lockup clutch is connected during reverse driving in a conventional torque converter will be described. FIG. 4 shows the flow of hydraulic oil when a lockup clutch is connected during reverse driving in a conventional torque converter. During reverse driving, the rotational speed of the turbine 4 on the output side is higher than the rotational speed of the impeller 3, so that hydraulic oil is discharged from the torus to the outer peripheral side. When the lockup clutch 207 is connected in this state, the hydraulic pressure in the first hydraulic chamber A becomes lower than the hydraulic pressure in the second hydraulic chamber B, so that the hydraulic oil discharged from the torus to the outer peripheral side is the inner peripheral side wall surface of the impeller shell 209. And then flows to the lockup clutch 207 side. There is a step that is smaller than the thickness of the outer peripheral projection 8 of the front cover 2 at the joint between the impeller shell 209 and the front cover 202, but the step has a shape that does not particularly consider the flow of hydraulic oil. Therefore, the hydraulic oil passes through the flow path 260 between the outer peripheral side protruding portion 208 of the front cover 202 and the outer peripheral side cylindrical portion 224 of the piston 222 without substantially impeding the flow at this step. Flow into. As a result, it is difficult to keep the hydraulic pressure in the first hydraulic chamber A lower than the hydraulic pressure in the second hydraulic chamber B during the lockup coupling operation, and the operation responsiveness of the lockup clutch 207 is deteriorated.

However, if it is the torque converter 1 in this embodiment, the action | operation responsiveness of the lockup clutch 7 at the time of reverse drive can be improved rather than before. FIG. 3 shows the flow of hydraulic oil when the lockup clutch 7 is connected during reverse driving in the torque converter 1 as one embodiment of the present invention. When the lockup clutch 7 is connected during reverse driving, the hydraulic oil discharged from the torus to the outer peripheral side flows along the inner peripheral side wall surface of the impeller shell 9 to the lockup clutch 7 side. At this time, since the above-described step portion 50 is provided at the joint portion between the impeller shell 9 and the front cover 2, the hydraulic oil flowing to the engine side along the second inner peripheral surface 52 is caused to flow toward the inner peripheral side by the step surface 53. And it is reversed to the transmission side. The flow of hydraulic oil is reversed because the angle α ₁ [°] formed between the step surface 53 and the second inner peripheral surface 52 is in a range of 45 ° ≦ α ₁ <90 °, more preferably This is because the step surface 53 is formed so as to be in the range of 60 ° ≦ α ₁ ≦ 80 °. As a result, the hydraulic oil can be prevented from flowing into the flow path 60, and the hydraulic pressure in the first hydraulic chamber A can be kept lower than the hydraulic pressure in the second hydraulic chamber during the lockup connection operation. Thereby, in this torque converter 1, the action | operation responsiveness of the lockup clutch 7 at the time of reverse drive can be improved compared with the past. At this time, it is preferable to set the thickness of the axial end portion 8a of the outer peripheral protrusion 8 to be thick. For example, by ensuring the thickness of the axial end portion 8a to be 1 mm or more, the flow of hydraulic oil can be reduced. The effect of inversion can be further improved.

  Moreover, the effect of the step part 50 can be further improved by adjusting the positional relationship between the step part 50 and the piston 22. Specifically, as described above, the piston 22 is arranged so that D ≧ 0 mm when the piston 22 is most moved to the axial transmission side when the lockup is released. As a result, it is possible to prevent the hydraulic oil that has been reversed to the inner peripheral side and the transmission side by the stepped portion 50 from flowing into the flow path 60. As a result, in the torque converter 1, the lock-up clutch can be maintained at the time of reverse drive as compared with the prior art in which the hydraulic pressure of the first hydraulic chamber A can be kept lower than the hydraulic pressure of the second hydraulic chamber during the lock-up coupling operation. 7 actuation responsiveness can be improved.

Further, the shape of the distal end portion of the outer peripheral cylindrical portion 24 of the piston 22 is tapered as described above. Specifically, the end surface 24a is in the range of α ₂ <90 °, more preferably 45 ° ≦ α ₂ ≦ 80 °. Therefore, it is possible to reliably prevent the hydraulic oil inverted by the stepped portion 50 from flowing into the flow path 60, and the operation of the lock-up clutch 7 at the time of reverse driving compared to the conventional case. Responsiveness can be improved. Even when the above-described step surface 53 is formed in a range of 90 ° ≦ α ₁ <135 °, this effect can be obtained by making the shape of the tip of the outer cylindrical portion 24 tapered. Obtainable.

Furthermore, the effect of the stepped portion 50 can be further improved by adjusting the relationship between the gaps of the flow paths. Specifically, as described above, the front cover 2, the impeller 3, the turbine 4, the piston 22, and the like are formed to satisfy L ₁ ≦ L ₂ . By satisfying L ₁ ≦ L ₂ , it is possible to inhibit the hydraulic oil inverted by the step portion 50 from flowing into the flow path 60. As a result, the hydraulic pressure in the first hydraulic chamber A can be kept lower than the hydraulic pressure in the second hydraulic chamber B during the lockup coupling operation, and the operation responsiveness of the lockup clutch 7 at the time of reverse driving compared to the conventional case. Can be improved.

4). Other Embodiments The present invention is not limited to the above-described embodiments, and various changes and modifications can be made without departing from the scope of the present invention.

(1) Stepped portion In the above-described embodiment, the stepped portion 50 is formed at the joint portion between the impeller shell 9 and the front cover 2 by using the thickness of the outer peripheral protruding portion 8, but is not limited thereto. For example, the step portion may be formed by deforming either the front cover or the impeller shell.

(2) Lock-up clutch In the above-described embodiment, the elastic coupling mechanism 40 of the lock-up clutch 7 is disposed on the outer peripheral side, but the present invention is not limited to this. It may be a lock-up clutch in which the elastic coupling mechanism 40 is disposed on the inner peripheral side.

The torque converter 1 as a fluid type torque transmission device of one embodiment of the present invention. The longitudinal cross-section partial figure of a step part periphery. The figure which shows the flow of the hydraulic fluid at the time of connecting the lockup clutch 7 at the time of reverse drive in the torque converter 1 of one Embodiment of this invention. The figure which shows the flow of the hydraulic fluid at the time of connecting a lockup clutch at the time of reverse drive in the conventional torque converter.

Explanation of symbols

1 Torque converter (fluid torque transmission device)
2 Front cover 2a Friction surface 3 Impeller 4 Turbine 5 Stator 7 Lock-up clutch (lock-up device)
DESCRIPTION OF SYMBOLS 8 Outer peripheral side protrusion part 9 Impeller shell 9a 2nd outer peripheral side cylindrical part 22 Piston 24 Outer peripheral side cylindrical part 40 Elastic connection mechanism 50 Step part 51 First inner peripheral surface 52 Second inner peripheral surface 53 Step surface A First hydraulic pressure Chamber B 2nd hydraulic chamber

Claims (8)

A fluid type torque transmission device for transmitting torque from the engine side to the transmission side,
A front cover to which torque is input from the engine side;
An impeller having an impeller shell disposed on the transmission side of the front cover and forming a fluid chamber together with the front cover; and a plurality of impeller blades provided inside the impeller shell;
A turbine disposed opposite the impeller blades in the fluid chamber;
A piston that can be connected to and disconnected from the front cover; and a lockup device that can mechanically connect the front cover and the turbine;
On the inner peripheral side of at least one of the front cover and the impeller shell, a step portion for changing the flow direction of the surrounding fluid is formed,
The step portion includes a first inner peripheral surface, a second inner peripheral surface that is formed on the transmission side in the axial direction of the first inner peripheral surface and has a larger inner diameter than the first inner peripheral surface, and the first and first 2 having a step surface formed between the inner peripheral surfaces,
An angle formed between the step surface and the second inner peripheral surface is smaller than 90 °,
Fluid torque transmission device. An angle formed between the step surface and the second inner peripheral surface is 45 ° or more.
The fluid type torque transmission device according to claim 1. On the outer peripheral side of the piston, it has an outer peripheral side tubular portion extending in the axial direction on the transmission side,
The distal end portion on the transmission side in the axial direction of the outer peripheral cylindrical portion is disposed on the engine side in the axial direction of the stepped portion,
The fluid type torque transmission device according to claim 1 or 2. A first gap formed between the first inner circumferential surface and the outer circumferential cylindrical portion is smaller than a second gap as a shortest gap formed between the stepped portion and the turbine. ,
The fluid type torque transmission device according to any one of claims 1 to 3. The tip of the outer cylindrical part has a taper shape that gradually protrudes in the axial direction over the entire circumference as it goes to the outer peripheral side.
The fluid type torque transmission device according to any one of claims 3 to 4. A fluid type torque transmission device for transmitting torque from the engine side to the transmission side,
A front cover to which torque is input from the engine side;
An impeller having an impeller shell disposed on the transmission side of the front cover and forming a fluid chamber together with the front cover; and a plurality of impeller blades provided inside the impeller shell;
A turbine disposed opposite the impeller blades in the fluid chamber;
A piston that can be connected to and disconnected from the front cover; and a lockup device that can mechanically connect the front cover and the turbine;
On the inner peripheral side of at least one of the front cover and the impeller shell, a step portion for changing the flow direction of the surrounding fluid is formed,
The step portion includes a first inner peripheral surface, a second inner peripheral surface that is formed on the transmission side in the axial direction of the first inner peripheral surface and has a larger inner diameter than the first inner peripheral surface, and the first and first 2 having a step surface formed between the inner peripheral surfaces,
On the outer peripheral side of the piston, it has an outer peripheral side tubular portion extending in the axial direction on the transmission side,
The distal end portion on the transmission side in the axial direction of the outer peripheral side tubular portion is disposed on the engine side in the axial direction of the stepped portion,
The distal end portion of the outer cylindrical portion has a taper shape that gradually protrudes in the axial direction over the entire circumference as it goes to the outer periphery side,
The fluid torque transmission device, wherein an angle formed between the step surface and the second inner peripheral surface is 135 ° or less. An angle formed between the step surface and the second inner peripheral surface is 45 ° or more.
The fluid torque transmission device according to claim 6. A first gap formed between the first inner circumferential surface and the outer circumferential cylindrical portion is smaller than a second gap as a shortest gap formed between the stepped portion and the turbine. ,
The fluid type torque transmission device according to claim 6 or 7.

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