JP2002070949A - Elastic connection mechanism and lockup device for torque converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify a structure of a stopper mechanism for stopping compression of an elastic member, in an elastic connection mechanism of lockup device or the like for a torque converter. SOLUTION: This lockup device 7 for a torque converter, for transmitting torque additionally absorbing and damping torsional vibration, has a disc-shaped piston 71, a torsion spring 74, a driven member 73, and a drive member 72. The disc-shaped piston 71 is a member for performing clutch action. A spring 74 is provided in the piston 71. The driven member 73, fixed to a turbine 22, has a pawl part 73b supporting both ends in the direction of rotation of the spring 74. The drive member 72 is fixed to the piston 71, to stop relative rotation of the piston 71 and the driven member 73 by abutting to the pawl part 73b when the spring 74 advances its compression.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an elastic coupling mechanism and a lockup device for a torque converter.

[0002]

2. Description of the Related Art Generally, an elastic coupling mechanism absorbs and attenuates torsional vibration transmitted from an input rotary member to an output rotary member while transmitting torque from an input rotary member to an output rotary member. As a structure in which such an elastic connection mechanism is used, for example, a lock-up device disposed inside a torque converter is known.

[0003] A torque converter is a device that has three types of impellers (impeller, turbine, and stator) inside and transmits torque through internal working oil. The impeller is fixed to a front cover as an input-side rotating body. The turbine is located opposite the impeller in the fluid chamber. When the impeller rotates, hydraulic oil flows from the impeller to the turbine, and outputs torque by rotating the turbine.

The lock-up device is arranged in a space between the turbine and the front cover, and is a mechanism for directly transmitting torque from the front cover to the turbine by mechanically connecting the front cover and the turbine. .

[0005] Usually, this lockup device has a disk-shaped piston that can be pressed against a front cover, a retaining plate fixed to the outer peripheral portion of the piston, and a rotation plate and an outer peripheral side fixed by the retaining plate. It has a torsion spring that is supported and a driven plate that supports both ends of the torsion spring in the rotation direction. The driven plate is fixed to a turbine shell or the like of the turbine.

When the lock-up device is connected, torque is transmitted from the front cover to the piston, and further transmitted to the turbine via the torsion spring.
Also, in the elastic coupling mechanism of the lock-up device, the torsion spring is compressed in the rotational direction between the retaining plate and the driven member to absorb torsional vibration.
Decay.

As a torsion spring, low rigidity
In order to achieve a wide torsion angle, there is a structure in which a pair of coil springs are arranged so as to act in series in the rotational direction. An intermediate float body (moving element) is arranged between the rotation directions of the pair of coil springs, and connects the pair of coil springs. The intermediate float body includes, for example, an annular portion and a claw extending from the annular portion and extending between a pair of coil springs.

[0008]

In the lock-up device described above, the driven plate sometimes has a pawl for forming a stopper mechanism in addition to the pawl for transmitting torque. The pawl is arranged at an interval in the rotation direction with respect to, for example, a part of the piston or the retaining plate, and comes into contact with the part when the torsion angle of the elastic connecting portion reaches a predetermined angle. As a result, the relative rotation operation of the elastic connecting portion stops.

In the above-described structure, since a stopper claw needs to be formed on the driven plate, the structure becomes complicated and the cost increases. An object of the present invention is to simplify the structure of a stopper mechanism for stopping compression of an elastic member in an elastic coupling mechanism such as a lock-up device of a torque converter.

[0010]

According to a first aspect of the present invention, there is provided an elastic coupling mechanism comprising a first rotating body, a second rotating body, an elastic member,
It has a supporting claw and a stopper. The elastic member was arranged so as to be compressed when the first rotating body and the second rotating body relatively rotated. The support claw is a member provided on the first rotating body for supporting the end of the elastic member in the rotation direction. The stopper is provided on the second rotating body, and stops the relative rotation between the first rotating body and the second rotating body by abutting on the support claw when the compression of the elastic member proceeds.

In this mechanism, the support claw has a function of a torque transmitting portion by engaging with the elastic member, and also constitutes a part of the stopper mechanism. Therefore, it is not necessary to provide a special structure for realizing the stopper mechanism.

According to a second aspect of the present invention, there is provided a lock-up device for a torque converter for transmitting torque and absorbing and attenuating torsional vibration, and includes a disk-shaped piston, an elastic member, and a driven member. And a stopper. The disk-shaped piston is a member for performing a clutch operation. The elastic member is provided on the piston. The driven member has claws fixed to the turbine and supporting both ends of the elastic member in the rotation direction. The stopper is fixed to the piston, and stops the relative rotation between the piston and the driven member by abutting on the claw as the compression of the elastic member proceeds.

In this device, the claw of the driven member engages with the elastic member to function as a torque transmitting portion and constitute a part of the stopper mechanism. Therefore,
There is no need to provide a special structure to realize the stopper mechanism.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (1) Basic Structure of Torque Converter FIG. 1 is a schematic longitudinal sectional view of a torque converter 1 according to an embodiment of the present invention. The torque converter 1 is a device for transmitting torque from a crankshaft 2 of an engine to an input shaft 3 of a transmission.
An engine (not shown) is arranged on the left side of FIG. 1, and a transmission (not shown) is arranged on the right side of FIG.
OO shown in FIG. 1 is a rotation shaft of the torque converter 1. Further, an arrow R1 in FIG. 4 indicates a driving side in the rotation direction of the torque converter 1, and an arrow R2 indicates the opposite side.

The torque converter 1 mainly includes a flexible plate 4 and a torque converter body 5. The flexible plate 4 is a thin disk-shaped member that transmits torque and absorbs bending vibration transmitted from the crankshaft 2 to the torque converter body 5. Therefore, the flexible plate 4 has sufficient rigidity for transmitting torque in the rotation direction, but has low rigidity in the bending direction.

The torque converter main body 5 comprises a torus-shaped fluid working chamber 6 composed of three types of impellers (impeller 21, turbine 22, and stator 23), and a lock-up device 7.

The front cover 11 is a disk-shaped member, and is disposed close to the flexible plate 4. A center boss 16 is provided on the inner peripheral end of the front cover 11.
Are fixed by welding. The center boss 16 is a cylindrical member extending in the axial direction, and is inserted into a center hole of the crankshaft 2.

The inner peripheral portion of the flexible plate 4 is fixed to the distal end surface of the crankshaft 2 by a plurality of bolts 13. A plurality of nuts 12 are fixed to the outer peripheral side of the front cover 11 and the engine side surface at equal intervals in the circumferential direction. Bolts 14 screwed into the nuts 12 cover the outer periphery of the flexible plate 4 with the front cover 11.
It is fixed to.

On the outer peripheral portion of the front cover 11, an outer peripheral cylindrical portion 11a extending toward the transmission in the axial direction is formed. The outer peripheral edge of the impeller shell 26 of the impeller 21 is fixed to the tip of the outer peripheral side cylindrical portion 11a by welding. As a result, a fluid chamber filled with hydraulic oil is formed by the front cover 11 and the impeller 21. The impeller 21 mainly includes an impeller shell 26, a plurality of impeller blades 27 fixed inside the impeller shell 26, and an impeller hub 28 fixed to an inner peripheral portion of the impeller shell 26.

The turbine 22 has an impeller 21 in the fluid chamber.
Are arranged to face each other in the axial direction. Turbine 2
2 mainly includes a turbine shell 30, a plurality of turbine blades 31 fixed to a surface on the impeller side thereof, and a turbine hub 32 fixed to an inner peripheral edge of the turbine shell 30.
It is composed of The turbine shell 30 and the turbine hub 32 are fixed by a plurality of rivets 33.

A spline engaging with the input shaft 3 is formed on the inner peripheral surface of the turbine hub 32. Thus, the turbine hub 32 rotates integrally with the input shaft 3.

The stator 23 is a mechanism for rectifying the flow of hydraulic oil returning from the turbine 22 to the impeller 21. The stator 23 is a member integrally manufactured by casting with a resin, an aluminum alloy, or the like. Stator 23 is arranged between the inner peripheral portion of impeller 21 and the inner peripheral portion of turbine 22. The stator 23 mainly includes the annular stator shell 3.
5 and a plurality of stator blades 36 provided on the outer peripheral surface of the shell 35. Stator shell 3
5 is supported on a cylindrical fixed shaft 39 via a one-way clutch 37. The fixed shaft 39 extends between the outer peripheral surface of the input shaft 3 and the inner peripheral surface of the impeller hub 28.

The toroidal fluid working chamber 6 is formed in the fluid chamber by the shells 26, 30, and 35 of the impellers 21, 22, and 23 described above. An annular space 9 is provided between the front cover 11 and the fluid working chamber 6 in the fluid chamber.

Although the one-way clutch 37 shown in the figure has a structure using a ratchet, it may have a structure using rollers and sprags. A first thrust bearing 41 is arranged between the inner peripheral portion of the front cover 11 and the turbine hub 32 in the axial direction. In a portion where the first thrust bearing 41 is provided, a first port 17 through which hydraulic oil can be communicated in a radial direction is formed. The first port 17 includes an oil passage provided in the input shaft 3, a first hydraulic chamber A (described later), the turbine 22 and the front cover 11.
And in the space between them. A second thrust bearing 42 is provided between the turbine hub 32 and the inner peripheral portion of the stator 23 (specifically, the one-way clutch 37).
Is arranged. In the portion where the second thrust bearing 42 is disposed, the second port 18 through which the hydraulic oil can communicate is formed on both sides in the radial direction. That is, the second port 18 is connected to the input shaft 3 and the fixed shaft 39.
And the fluid working chamber 6 are communicated with each other. Further, a third thrust bearing 43 is arranged between the stator 23 (specifically, the shell 35) and the impeller 21 (specifically, the impeller hub 28) in the axial direction. In the portion where the third thrust bearing 43 is disposed, the third port 19 through which hydraulic oil can communicate on both sides in the radial direction.
Are formed. That is, the third port 19 is connected to the oil passage between the fixed shaft 39 and the impeller hub 28,
The fluid working chamber 6 is communicated with the fluid working chamber 6. In addition, each oil passage is connected to a hydraulic circuit (not shown), and supply and discharge of hydraulic oil to the first to third ports 17 to 19 can be performed independently. (2) Structure of Lockup Device The lockup device 7 is disposed in the space 9 between the turbine 22 and the front cover 11, and is a mechanism for mechanically connecting the two as necessary. The lockup device 7 has a disk shape as a whole, and divides the space 9 substantially in the axial direction. Here, the space between the front cover 11 and the lockup device 7 is defined as a first hydraulic chamber A,
The space between the lockup device 7 and the turbine 22 is
Hydraulic chamber B.

The lock-up device 7 has the functions of a clutch and an elastic coupling mechanism, and mainly includes a piston 71, a driven member 73, a plurality of torsion springs 74, and a spring holder 75.

The piston 71 is a member for connecting / disconnecting the clutch, and further functions as an input member in the lock-up device 7 as an elastic connecting mechanism. The piston 71 has a disk shape with a center hole formed therein. The piston 71 extends over the entire radius in the space 9 so as to divide the space 9 substantially in the axial direction. On the inner peripheral edge of the piston 71, an inner peripheral side tubular portion 71b extending toward the transmission in the axial direction is formed. The inner peripheral side cylindrical portion 71b is supported by the outer peripheral surface of the turbine hub 32 so as to be movable in the rotation direction and the axial direction. The turbine hub 32
A flange 32a for restricting the movement of the piston 71 toward the transmission in the axial direction by being in contact with the inner peripheral cylindrical portion 71b is formed on the outer peripheral surface of the inner peripheral cylindrical portion 71b. Further, the inner peripheral side cylindrical portion 71b is formed on the outer peripheral surface of the turbine hub 32.
An annular seal ring 32b is provided in contact with the inner peripheral surface of the ring. Thus, the inner peripheral edge of the piston 71 is sealed in the axial direction. Further, a friction coupling portion 71c is formed on the outer peripheral side of the piston 71. The friction coupling portion 71c is an annular portion having a predetermined length in the radial direction, and has a planar shape in which both surfaces in the axial direction are surfaces perpendicular to the axial direction. An annular friction facing 76 is provided on the engine side of the friction connecting portion 71c in the axial direction.
Thus, the clutch of the lockup device 7 is constituted by the piston 71 and the flat friction surface of the front cover 11.

The drive member 72 is fixed to the piston 71 and applies torque of the piston 71 to the torsion spring 7.
4 is a member for transmission. The drive member 72 is
As shown in FIG. 4, an annular fixing portion 72a and a fixing portion 72
a, a plurality of claw portions 72b extending radially outward from the fixed portion 72a, and a plurality of arcuate portions 72c extending radially outward from the fixed portion 72a
It is composed of The fixed part 72a is
And is fixed by a plurality of caulks 71f. Each claw portion 72b extends radially outward, curves so as to project toward the engine side in the axial direction, and further extends toward the transmission side in the axial direction. In this embodiment, a total of four claw portions 72b are formed. The curved portion of the claw portion 72b is in contact with the friction connecting portion 71c of the piston 71.

The arc-shaped portion 72c is formed in the rotation direction of the claw portion 72b, and extends in an arc along the outer periphery of the fixed portion 72a. The arc-shaped portion 72c extends outward in the radial direction and is inclined as a whole toward the transmission in the axial direction. The arc-shaped portion 72c includes a first portion 72d, a second portion 72e, and a third portion 72f from a radially inner side to an outer side. The first portion 72d is entirely formed in the rotation direction between the claws 72b. The second portion 72e is a portion extending further outward from the first portion 72d. The second portion 72e is the first portion 72
The length of the first portion 72d in the rotation direction is shorter than that of the first portion 72d. Therefore, the second portion 72e is
It has an end face in the rotation direction separated from the claw 72b in the rotation direction. The third portion 72f is a portion extending further outward from the second portion 72e. The third portion 72f is the second portion 72
The length of the second portion 72e in the rotation direction is shorter than that of the second portion 72e in the rotation direction. The third portion 72f is a portion for supporting a spring holder 75 (described later) in a radial direction and an axial direction.

An arc-shaped spring accommodating portion is provided between the claws 72b of the drive member 72 in the rotational direction, that is, on the outer peripheral side of the arc-shaped portion 72c. In this embodiment, four spring housings are formed.

A pair of torsion springs 74a, 74 are provided between the respective spring accommodating portions, ie, between the claws 72b in the rotational direction.
b are arranged to act in series in the direction of rotation.
That is, a total of eight torsion springs 74 are provided.
Is used. Here, the torsion spring is a coil spring extending in the rotation direction, but may include not only a single coil spring but also a combination of a small coil spring and an elastic body in the coil spring. Also, in each spring housing,
The one in the rotation direction R1 is referred to as a torsion spring 74a, and the one in the rotation direction R2 is referred to as a torsion spring 74a.
b. The claw portion 72b is provided with a torsion spring 74a.
Abuts or approaches the R1 side end of the torsion spring 7
4b is in contact with or close to the R2 side end.

The spring holder 75 is assembled to the drive member 72, and the piston 71 and the drive member 72
And the driven member 73 can be relatively rotated. The spring holder 75 is a ring-shaped sheet metal member, and is disposed on the outer peripheral edge of the friction coupling portion 71c of the piston 71 on the axial transmission side. The spring holder 75 mainly includes a cylindrical portion 75a and an annular portion 75 extending radially inward from an end of the cylindrical portion 75a on the transmission side in the axial direction.
b. The cylindrical portion 75 a is arranged on the outer peripheral side of the torsion spring 74. Annular part 75b
Has an outer peripheral portion and an inner peripheral portion pressed down from the outer peripheral portion toward the engine side by press working. Annular part 75b
An inner peripheral surface 75g is formed at the boundary between the outer peripheral portion and the inner peripheral portion. The inner peripheral surface 75 g is provided on the third portion 72 of the drive member 72.
f is in contact with the outer peripheral surface. By this contact, the spring holder 75 moves the drive member 72 and the piston 71
Are positioned in the radial direction. Since the spigot portion of the radial support portion is formed by the press fracture surface, it is easy to form. Further, the inner peripheral portion of the annular portion 75b is located on the engine side in the axial direction of the third portion 72f of the drive member 72. This structure prevents the spring holder 75 from coming off the drive member 72 and the piston 71 toward the transmission in the axial direction.

A plurality of claw portions 75c are formed on the inner peripheral edge of the annular portion 75b of the spring holder 75. Claw part 7
5c are formed in a row in the rotation direction, and extend toward the engine in the axial direction. The claw portion 75c is formed corresponding to the third portion 72f of the drive member 72, that is, at an intermediate position in the rotation direction between the claw portions 72b. The claw portion 75c extends between the pair of torsion springs 74a and 74b, and functions as a torque transmitting portion for connecting the two in the rotational direction. The tip of the claw portion 75c is close to the curved portion of the claw portion 72b of the drive member 72, so that the spring holder 75 separates the drive member 72 and the piston 7
1 is restricted from moving toward the transmission in the axial direction.

As described above, in the state where the spring holder 75 is guided by the drive member 72 (in the state where it is immovably engaged in the radial and axial directions),
It can be moved in the rotation direction. In other words, the spring holder 75 is provided with the drive member 7 as a restricting portion.
The support 2 is provided so as to be relatively rotatable and restricted from moving outward in the radial direction. With such a structure, the spring holder 75 can support the load of the torsion spring 74 that moves radially outward due to the centrifugal force. Therefore, it is necessary to provide a cylindrical portion for receiving the spring on the outer peripheral edge of the piston 71. There is no.

The annular portion 7 of the spring holder 75
5b includes a claw 72b of the drive member 72 at the time of assembly.
Are formed with a plurality of notches 75d for penetrating through. A protruding portion 75e that protrudes in the axial direction from the other portion is formed at an axial end of the cylindrical portion 75a corresponding to the cutout 75d on the engine side in the axial direction. Projection 75
"e" is a structure for maintaining the balance in the rotational direction by compensating for the decrease in rigidity due to the notch 75d.
A cutout 75f is formed at the end of the cylindrical portion 75a in the axial direction corresponding to the claw portion 75c so as to be recessed in the axial direction from other portions. Notch 75f is claw 75c
This is a structure for maintaining a balance in the rotational direction by compensating for an increase in rigidity.

The driven member 73 is a member for transmitting the torque from the torsion spring 74 to the turbine 22. The driven member 73 is an annular member made of sheet metal provided on the outer peripheral side of the turbine shell 30 of the turbine 22. The driven member 73 has an annular fixing portion 73a fixed to the turbine shell 30 and a plurality of claws 73b extending from the outer peripheral edge toward the engine in the axial direction. The claw 73b of the driven member 73 is connected to the claw 7 of the drive member 72.
2b, and extends into the curved portion of the claw portion 72b. The claw portion 73b has the same rotation direction width as the claw portion 72b of the drive member 72.
Similarly, the rotation direction R1 of the torsion spring 74a
It is in contact with or close to the side end and the end in the rotation direction R2 of the torsion spring 74b.

The claw portion 73b is movable in the axial direction with respect to the drive member 72. That is, the piston 71 can move in the axial direction by a change in the hydraulic pressure while maintaining the state of being engaged with the torsion spring 74.

The claw portion 73b is located at an intermediate position in the rotation direction between the second portions 72e of the drive member 72.
e is separated from the end face in the rotation direction by a predetermined angle in the rotation direction.
The driven member 73 can rotate relative to the drive member 72 until the claw portion 73b comes into contact with the end surface in the rotation direction of the second portion 72e. In other words, the drive member 72
The second portion 72e and the claw portion 73b of the driven member 73 form a stopper mechanism for stopping the relative rotation between the two. As described above, the claw portion 73b has a function of a torque transmitting portion by engaging with the torsion spring 74, and also constitutes a part of a stopper mechanism of the elastic connecting portion. Therefore, it is not necessary to provide a special structure for the stopper mechanism. (4) Operation of lockup device The speed ratio of the torque converter 1 increases, and the input shaft 3
Reaches a certain number of rotations, the hydraulic oil in the first hydraulic chamber A is discharged from the first port 17. As a result, the first hydraulic chamber A
The piston 71 is moved to the front cover 11 side by the hydraulic pressure difference between the front cover 11 and the second hydraulic chamber B, and the friction facing 76 is pressed against the flat friction surface of the front cover 11. As a result, the torque of the front cover 11 is transmitted from the piston 71 to the driven member 73 via the torsion spring 74. Further, the torque is transmitted from the driven member 73 to the turbine 22. That is, the front cover 11 is mechanically connected to the turbine 22, and the torque of the front cover 11 is directly output to the input shaft 3 via the turbine 22.

In the lock-up connection state described above, the lock-up device 7 transmits torque and absorbs and attenuates torsional vibration input from the front cover 11. Specifically, when torsional vibration is input from the front cover 11 to the lockup device 7, the torsion spring 74 is compressed in the rotational direction between the piston 71 and the driven member 73. More specifically, the torsion spring 74 is compressed in the rotational direction between the claw 72b of the drive member 72 and the claw 73b of the driven member 73. At this time, the pair of torsion springs 74a, 7
Since 4b acts in series in the rotational direction, torsional characteristics with low rigidity and a wide torsion angle can be obtained.

As described above, when torsional vibration is input and the torsion spring 74 repeats compression, the torsion spring 74 moves radially outward due to centrifugal force and slides on the spring holder 75. However, since the spring holder 75 is a member that moves in the rotational direction together with the torsion spring 74, the sliding resistance between the two members is extremely small. Therefore, the torsional vibration absorbing performance is sufficiently maintained. (6) Advantageous Effects of the Present Invention a) The spring holder 75 supports the outer peripheral side of the torsion spring 74 by the cylindrical portion 75a while being restricted from moving in the radial direction by the arc portion 72c of the drive member 72. Thus, the spring holder 75
By restricting the movement of the torsion spring 74 to the outer periphery, the outer cylindrical portion of the disc-shaped piston 71 can be omitted.

B) The spring holder 75 functions as an intermediate float body for the pair of torsion springs 74a and 74b, and the outer cylindrical portion of the piston can be omitted with a simple structure.

C) In the lock-up device 7, the structure is simplified, the number of parts is reduced, and the cost and weight can be reduced. In particular, since the structure of the spring holder 75 has been simplified, weight reduction and equipment development man-hours have been reduced.

In particular, since the drive member 72 has only the function of transmitting torque and does not have the function of holding the torsion spring, the structure is simplified and the weight and thickness can be reduced.

D) Since the spring holder 75 supports only the transmission side of the torsion spring 74 in the axial direction, the torsion spring 74 is in direct contact with the piston 71. As a result, the coil diameter of the torsion spring 74 can be made sufficiently large, and the design for realizing low rigidity becomes easy.

E) Further, since the spring holder 75, the torsion spring 74, and the driven member 73 can be arranged in an extra space between the outer peripheral portion of the piston 71 and the outer peripheral portion of the turbine 22, space efficiency is improved. That is, the axial dimension of the torque converter does not become extremely large due to these members.

The structure of the lockup device is not limited to the above embodiment. For example, the present invention can be applied to a lockup device for a double-plate clutch in which a plurality of plates are arranged between a piston and a front cover.

[0046]

In the elastic connecting mechanism according to the present invention, the supporting claw has the function of the torque transmitting portion by engaging with the elastic member and constitutes a part of the stopper mechanism. Therefore, it is not necessary to provide a special structure for realizing the stopper mechanism.

[Brief description of the drawings]

FIG. 1 is a schematic longitudinal sectional view of a torque converter employing a first embodiment of the present invention.

FIG. 2 is a partially enlarged view of FIG.

FIG. 3 is a view corresponding to FIG. 2, and a cross-sectional view at a position different from FIG. 2;

FIG. 4 is a partial perspective view of an elastic connecting portion of the lock-up device.

[Explanation of symbols]

 Reference Signs List 7 lock-up device 11 front cover 71 piston 72 drive member 72e second portion 73 driven member 73b claw portion 74 torsion spring

Claims (2)

[Claims] A first rotating body, a second rotating body, an elastic member arranged to be compressed when the first rotating body and the second rotating body rotate relative to each other; A supporting claw provided for supporting a rotation direction end of the elastic member; and a supporting claw provided on the second rotating body, wherein the first rotating body and the first rotating body are brought into contact with the supporting claw when compression of the elastic member progresses. A stopper for stopping the relative rotation of the second rotating body. 2. A lock-up device for a torque converter for transmitting torque and absorbing and attenuating torsional vibration, comprising: a disk-shaped piston for performing a clutch operation; and a piston provided on the piston. An elastic member, a driven member having a claw fixed to the turbine and supporting both ends of the elastic member in the rotation direction, and a driven member fixed to the piston and abutting on the claw as the compression of the elastic member proceeds And a stopper for stopping the relative rotation of the piston and the driven member.