JP2001173693A - Actuator for motor driven brake - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the friction between a gear and a housing accompanied by the movement of a rotating slide member from impairing the energy efficiency or deteriorating the durability of the housing or gear with an easy method. SOLUTION: In this actuator for motor driven brake 12, when the rotating slide member 32 arranged axially movably and rotatably about the axial center is rotated through the input gear 48 according to the braking rotation of an electric motor 54, a pair of output members 38 and 40 screwed to the rotating slide member 32 through a pair of screw mechanisms 34 and 36 having opposite torsions is protruded to extend a pair of brake shoes 15 and 18, respectively, so that a braking force is generated. In this actuator, a hard shim 70 having a small friction coefficient is arranged between the input gear 48 and a case member 62.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a motor-driven brake actuator that generates a braking force by pressing a pair of friction members against a brake rotating body by an electric motor.

[0002]

2. Description of the Related Art A motor drive brake that generates a braking force by pressing a pair of friction members against a brake rotating body by an electric motor is known as a brake for vehicles such as automobiles and trains. The device described in Japanese Patent Publication No. 6-100239 is one example.

On the other hand, Japanese Patent Application No. Hei.
Although it has not yet been published in 1-187911,
(a) a housing fixedly disposed on a vehicle body-side member;
(b) a rotating slide member that is arranged in the housing so as to be movable in a straight line direction and rotatable around the straight line, and is driven to rotate around the straight line with the brake rotation of the electric motor; At least one of both ends of the rotary slide member in the linear direction is fitted so as to be relatively rotatable around the straight line, and mechanically straddles the pair of friction members (brake shoes) together with the rotary slide member. An output member interposed and prevented from rotating about the straight line; and (d)
The output slide member is provided at a fitting portion between the output slide member and the rotary slide member, and the rotary slide member is driven to rotate around the straight line in accordance with the rotation of the electric motor for braking. The output member is relatively moved in the linear direction with respect to the rotary slide member by the action of the screw accompanying the extension of the output member to extend the entire length. Based on the elongation and the movement of the rotary slide member in the linear direction, the pair of friction members A screw mechanism for substantially uniformly pressing a member against the brake rotating body (brake drum); and (e) being disposed on the outer peripheral surface of the rotary slide member so as to be relatively movable in the axial direction and not to rotate relatively around the axis. And an input gear that is prevented from moving in the axial direction by the housing, and controls the rotation of the electric motor for braking through the input gear. And a gear mechanism for transmitting the rotation to the rotary slide member.

[0004]

However, when the input gear is provided on the outer peripheral surface of the rotary slide member so as to be relatively movable in the axial direction and not to be rotatable relative to the axis, the rotary slide member is driven to rotate. When the rotary slide member moves in a straight line, the input gear is pressed against the housing, which causes rotational resistance due to friction, impairs energy efficiency, and also causes the housing to be scraped or scraped metal dust to the gear. There was a possibility that durability would be reduced due to biting. Although it is conceivable to apply a hardening treatment to the surface of the housing, the cost is increased and it is not always satisfactory.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to reduce energy efficiency due to friction between an input gear and a housing accompanying movement of a rotary slide member, or to reduce the energy efficiency of a housing or a gear. It is an object of the present invention to prevent a decrease in the durability of the device by a simple method.

[0006]

SUMMARY OF THE INVENTION In order to achieve the above object, a first aspect of the present invention is an actuator for a motor drive brake which generates a braking force by pressing a pair of friction members against a brake rotating body by an electric motor. (A) a housing disposed fixedly on the vehicle body side member; and (b) a housing disposed so as to be movable in a straight line direction and rotatable around the straight line, and for braking the electric motor. (C) a rotary slide member rotatably driven around the straight line with the rotation, and (c) at least one of both ends in the linear direction of the rotary slide member fitted so as to be relatively rotatable around the straight line, and An output member that is mechanically interposed across the pair of friction members together with the member, and that is prevented from rotating around its straight line; A rotary member is provided at a fitting portion between the force member and the rotary slide member, and the rotary slide member is driven to rotate around the straight line with the rotation of the electric motor for braking. The output member is moved relative to the rotary slide member in the linear direction by the action of the accompanying screw to expand and contract the entire length, and based on the expansion and contraction and the movement of the rotary slide member in the linear direction, the pair of friction members (E) disposed on the outer peripheral surface of the rotary slide member so as to be relatively movable in the axial direction and not to rotate relatively around the axis, and An input gear that is prevented from moving in the axial direction; and a rotation slide member for rotating the electric motor for braking via the input gear. And (f) a thin shim provided in a portion of the housing that comes into contact with the input gear and having a coefficient of friction smaller than that of the housing.

A second invention is the actuator for a motor-driven brake according to the first invention, wherein (a) the input gear is a cylindrical gear, and (b) the shim is located between the input gear and the housing. A first disk portion, and a second disk portion located between a gear meshing with the input gear and the housing are integrally provided in one plane.

[0008]

In such a motor-driven brake actuator, a shim having a small coefficient of friction is provided between the housing and the input gear, and the input gear is moved to the shim when the rotary slide member moves in a straight line. Due to the pressing, the rotational resistance due to friction is small and the decrease in energy efficiency is suppressed, and since the friction is small, wear and damage of shims and input gears are suppressed, and the durability is improved. Further, since it is only necessary to dispose the shim on the housing, the apparatus is configured at a lower cost as compared with a case where the surface of the housing is subjected to a curing treatment.

According to the shim of the second invention having the first disk portion and the second disk portion, rotation around a straight line is prevented only by disposing the shim in the housing, and the posture is determined.
There is no need for a claw or an engagement recess for positioning the posture, so that the device is simple and inexpensive, and the work of assembling the shim is easy.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Here, as the shim, a hard plate material having a small friction coefficient, for example, a stainless steel plate is preferably used, but plate materials made of various materials having a smaller friction coefficient than the housing can be adopted. . The appropriate thickness of the shim is, for example, about 0.1 to 0.2 mm. This shim may be arranged in a pair on both sides of the input gear.For example, when one of the shims is supported by a bearing and the other is in surface contact with the housing, it may be arranged only on the surface contact side. It may be arranged only on one side.

In the second aspect of the invention, the shim includes the first disk portion and the second disk portion. However, a disk-shaped shim corresponding to the input gear can be used, and the friction can be increased. May be positioned so as to be substantially non-rotatable with respect to the housing. In addition, the shim may be similarly arranged at a part other than the input gear at a part where the gear and the housing are in direct contact. When a helical gear is used as the gear mechanism, since a thrust force is generated according to the meshing load, it is effective to arrange shims.

As the input gear, for example, a cylindrical gear such as a spur gear or a helical gear is preferably used, but a bevel gear or a worm may be used. This input gear is
For example, it is disposed on the rotary slide member so as to be relatively movable in the axial direction (in a straight line direction) via a detent key, a spline, a serration, etc., and to be relatively unable to rotate around the axis.

The present invention is suitably applied to a drum brake of a leading trailing type or a duo servo type, but can also be applied to other brake devices such as a disc brake. Further, the present invention can be applied to both a service brake and a parking brake, and can have both functions of the service brake and the parking brake. When used as a parking brake, for example,
As described in Japanese Patent No. 0239, a brake maintenance mechanism for preventing reverse rotation of an electric motor or the like may be provided. When a worm is used as the input gear, it can be used as a parking brake without a brake maintaining mechanism.

When used as a service brake, the braking force is controlled by torque control or forward / reverse rotation control of the electric motor in accordance with the driver's required braking amount such as the operating position and operating force of a brake operating member such as a brake pedal. Is possible. The braking can be released by reverse rotation of the electric motor, but a pair of friction members may be retracted by the return elastic member such as a return spring when the operation of the electric motor is stopped. In the power transmission path between the electric motor and the input gear, the power is transmitted by being engaged during braking, but if a clutch device is provided to cut off the power transmission during non-braking, the electric motor does not rotate in reverse. The brake can be easily released by the return elastic member.

Preferably, a pair of output members are screwed at both ends of the rotary slide member in the linear direction through a pair of screw mechanisms having opposite twists so as to be relatively rotatable about the straight line. And the pair of output members are configured to be mechanically engaged with the pair of friction members in a state where rotation about the straight line is prevented. In this case, since a screw mechanism is provided at both ends of the rotary slide member and the pair of output members are relatively moved in a straight line direction, the rotation (axial direction) of the rotary slide member for each brake is reduced. The operation is stable and the durability is improved. Although the pair of screw mechanisms have opposite twists, the leads and diameters of the screws may be the same or different.

When only a single output member is provided at one end of the rotary slide member, for example, the other end of the rotary slide member may be directly engaged with the friction member so as to be relatively rotatable around a straight line, or may be rotated. A connecting member may be provided at the other end of the sliding member so as to be rotatable around a straight line without using a screw mechanism, and the connecting member may be engaged with a friction member or the like.

The motor-driven brake generates a braking force by pressing a pair of friction members against a brake rotating body (a brake drum or a brake disk) that rotates together with wheels by, for example, moving a pair of friction members closer to or away from each other. The rotary slide member is disposed, for example, on a straight line substantially parallel to the approach or separation direction of the pair of friction members, and is interposed directly or indirectly across the pair of friction members together with the output member. Can be In the case of a drum brake, for example, the rotary slide member is disposed on a straight line substantially coincident with the approach and separation directions of a pair of friction members (brake shoes), and the rotary slide member and the output member are, for example, a pair of friction members. Engaged with one and the other,
When the output member is linearly moved in the direction in which the output member protrudes from the rotary slide member during braking (the direction in which the total length of both members increases), the pair of friction members are separated from each other. The pair of friction members is engaged with the pair of friction members via the lever, and the output member is linearly moved in a direction in which the output member is pulled into the rotating slide member (the direction in which the total lengths of both members are shortened) during braking. The members may be configured to be separated from each other. The same applies to the case where output members are provided at both ends of the rotary slide member.

The screw mechanism comprises, for example, a screw hole (female screw) provided in the axis of the rotary slide member and a screw shaft (male screw) provided upright on the output member. The output member may be provided with a female screw. The output member is, for example, a friction member,
Although rotation around a straight line is prevented by engagement with a lever or the like engaged with the friction member, rotation around the straight line is prevented by engagement with another member such as a housing or a backing plate (vehicle-side member). It may be so.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows an example in which the present invention is applied to a leading / trailing type motor-driven drum brake 10.
FIG. 2 is a front view showing an upper end portion where 2 is assembled.
FIG. 2 is a sectional view taken along the line II-II in FIG. The motor-driven drum brake 10 includes a backing plate 14 fixedly mounted on a vehicle body-side member that rotatably supports wheels, and a pair of brake shoes 16, 18 disposed substantially symmetrically on the backing plate 14. And the actuator 12 disposed between the upper ends of the pair of brake shoes 16 and 18 at a fixed position on the backing plate 14 or the vehicle body-side member, and the backing plate 14 between the lower ends of the pair of brake shoes 16 and 18. An anchor (not shown) arranged at a fixed position and a pair of brake shoes 1
A return spring (tensile coil spring) 2 which is arranged straddling 6, 18 and biases in a direction approaching each other.
0, and a strut 22 for defining an approach position of the pair of brake shoes 16 and 18. The pair of brake shoes 16, 18 are always driven by struts 22, as shown in FIG.
Is held at an approaching position (non-brake state) where the brake shoes 1
When the upper ends of the wheels 6 and 18 are expanded to the left and right sides, they are pressed by a brake drum 24 disposed on the wheel side to generate a braking force. The brake shoes 16 and 18 correspond to friction members, the return spring 20 corresponds to a return elastic member, the strut 22 corresponds to a standby position defining member, and the brake drum 24 corresponds to a brake rotating body. The backing plate 14 can be regarded as a vehicle body-side member.

The struts 22 are made of a friction material (lining).
Automatic adjustment of the gap between the brake shoes 16, 18 according to the wear of the friction material so that the shoe gap between the brake shoes 16, 18 and the brake drum 24 is substantially constant irrespective of the wear of the shoe. A mechanism 26 is provided. That is, the strut 22 is always held in a state of being engaged with one of the brake shoes 18 by a spring or the like (not shown), and if the amount of relative movement with the other brake shoe 16 increases during braking due to wear of the friction material, not shown. When the star wheel 26f is rotated by the adjustment lever, the overall length is increased by the rotation of the screw shaft provided integrally with the star wheel 26f, and the standby positions of the brake shoes 16, 18 during non-braking are separated. As a result, the shoe gap (the total size of the shoe gaps on both sides) is maintained substantially constant.

The actuator 12 includes a holding case 3
0, a cylindrical rotary slide member 32 held axially movable and rotatable about an axis via a pair of bearings and splines, and screw mechanisms 34 at both ends of the rotary slide member 32, respectively. , 36 and a pair of output members 38 and 40 which are screwed so as to be relatively rotatable about the same axis.
Is a straight line direction in which the axis of the rotary slide member 32 is the approach and separation directions of the pair of brake shoes 16 and 18 (FIG. 1).
(Horizontal direction), and is integrally fixed to the backing plate 14 or the vehicle body side member. The screw mechanisms 34 and 36 include screw holes (female screws) 32R and 32L provided on the axis of the rotary slide member 32, and screw shafts (male screws) 38 provided integrally with the output members 38 and 40.
s, 40s, but the screw mechanisms 34, 36 have opposite twists, ie, one is a right-hand thread and the other is a left-hand thread, and other specifications such as lead and diameter are the same. When the rotary slide member 32 is rotated relative to the rotary slide member 32 in the same direction, the rotary slide member 32 symmetrically protrudes or retracts from the rotary slide member 32. Further, the pair of output members 38 and 40 respectively protrude outside from the left and right openings of the holding case 30 and have heads 38 h and 40.
h is engaged with the shoe webs of the brake shoes 16 and 18 so that rotation about the axis is prevented and the heads of the output members 38 and 40 are formed. Dust boots 42 and 44 prevent dust between 38 h and 40 h and the holding case 30. In FIG. 2, the dust boots 42 and 44 are omitted.

An input gear 48 is attached to the outer peripheral surface of the rotary slide member 32 so as to be relatively movable in the axial direction and not to be rotated relative to the axis by a detent key 46.
The input gear 48 is one element of a reduction gear mechanism 52 provided in the gear case 50 and is driven to rotate by an electric motor 54. In this embodiment, a spur gear is used as each gear of the gear mechanism 52. Electric motor 54 and gear mechanism 5
2, an electromagnetic clutch 56 that can continuously change the transmission torque by controlling the frictional force with an electromagnetic force is provided as a clutch device.
6, the power transmission to and from the gear mechanism 52 is connected and cut off, and at the time of connection, the transmission torque is controlled by an ABS (anti-skid brake system) control as needed, so that the braking force is controlled. I have.

The holding case 30 and the gear case 50 are
The gear case 50 is formed of a pair of case members 62 and 64, and the gear case 50 is
Backing plate 1 with a fixing means such as welding, caulking, rivets, etc.
The electric motor 54 is integrally fixed to the gear case 50. Further, the input gear 48 includes a pair of case members 6.
2 and 64, the axial movement is prevented by the case members 62 and 64, and the meshing state with the gear 66 of the gear mechanism 52 regardless of the axial movement of the rotary slide member 32. Is well maintained. More specifically, the movement toward the output member 38 (to the right in FIG. 2) is performed by a bearing 68 that is disposed on the case member 64 and supports the rotary slide member 32 together with the input gear 48 so as to be rotatable around the axis. The movement to the output member 40 side (left direction in FIG. 2) is prevented, and the reference surface 62f of the case member 62
Is to be prevented by. The housing is constituted by the holding case 30 and the gear case 50, and is fixed to the vehicle body side member via the backing plate 14, or is directly fixed to the vehicle body side member rotatably supporting the wheel. .

A shim 70 made of a hard stainless steel plate having a smaller coefficient of friction than the case member 62 is provided on the reference surface 62f. Shim 70 is
As shown in FIG. 3, the first disk portion 70 a having a large diameter and located between the input gear 48 and the case member 62, A small-diameter second disk portion 70b located therebetween is integrally provided in one plane. 1st disk part 70a and 2nd disk part 70b
Are formed in accordance with the diameters of the input gear 48 and the gear 66 so as to correspond to the inner diameters of the gear receiving holes provided in the case member 62, and are positioned in a fixed posture by being disposed in the case member 62. You. A first circular hole 70c that allows the rotation of the rotary slide member 32 including the detent key 46 is formed in the first disk portion 70a, and a gear 66 is formed in the second disk portion 70b. Support shaft 7
2 is provided with a second circular hole 70d that allows insertion of the second circular hole.

Such a motor-driven drum brake 10
When the electric motor 54 is operated in accordance with the brake operation of the driver, and the rotation for braking is transmitted from the connected electromagnetic clutch 56 to the rotary slide member 32 via the gear mechanism 52 and the input gear 48, the shaft The pair of output members 38 and 40, whose rotation around the center is prevented, are moved in the direction protruding from the rotary slide member 32 by the action of the screws of the screw mechanisms 34 and 36, whereby the pair of brake shoes 16 and 18 are moved. Spread to both sides (separate)
It is pressed by the brake drum 24. In this case, since the rotary slide member 32 is disposed so as to be movable in the axial direction (in a straight line), the brake shoes 16 and 18 are uniformly pressed against the brake drum 24 regardless of dimensional errors and wear. At the same time, there is no possibility that an excessive force is generated in the holding case 30 or the like holding the rotating slide member 32. Further, when the transmission torque of the electromagnetic clutch 56 is controlled by the ABS control as required, the braking force is very finely controlled with high responsiveness by the transmission torque control and the urging force of the return spring 20.

On the other hand, with the pair of brake shoes 16 and 18 expanded to both sides, the operation of the brake rotation of the electric motor 54 is stopped, and the electric motor 54 and the rotary slide member 32 are connected by the electromagnetic clutch 56. When power transmission between the two is interrupted, the return spring 2
The output members 38 and 40 are pushed back in the direction opposite to the direction of movement during braking while rotating the rotary slide member 32 in the reverse direction with the urging force of 0, and the pair of brake shoes 16 and 18
2 is brought close to the standby position where it comes into contact. The specifications such as the lead angles of the screws of the screw mechanisms 34 and 36 and the urging force of the return spring 20 are such that when the electromagnetic clutch 56 cuts off the electric motor 54 and the rotary slide member 32, the return spring It is determined that the rotating slide member 32 can be reversely rotated by the biasing force of 20. For this reason, the lead angle is set to be relatively large. However, in order to obtain a practically sufficient braking force by the motor torque of the electric motor 54, the lead is formed with a multi-thread screw having a pitch twice or more the pitch. It is configured. 1 and 2, the heads 38 of the pair of output members 38 and 40 are shown.
h and 40h are both in contact with the ends of the rotary slide member 32, but in actual use conditions, the brake shoes 16, 1
The standby position 8 is defined by the strut 22, and the heads 38 h and 40 h do not abut on the holding case 30.

As described above, the motor-driven drum brake 10 of the present embodiment rotates the rotary slide member 32 by the electric motor 54 so that the pair of output members 3 is driven.
8, 40 are pushed out from the rotary slide member 32 to press the pair of brake shoes 16, 18 against the brake drum 24 to generate a braking force. An effect similar to that of a conventional hydraulic wheel cylinder that expands the pair of brake shoes 16 and 18 is obtained. Instead of the hydraulic wheel cylinder, a brake operation can be detected by an electric signal and used as a regular brake. it can. The driver's brake request amount can be detected based on the operation position and operation force of a brake operation member such as a brake pedal,
The braking force may be controlled by torque control of the electric motor 54 or transmission torque control of the electromagnetic clutch 56.

In the present embodiment, the rotary slide member 3
Since the screw mechanisms 34 and 36 are provided at both ends of the pair 2 so that the pair of output members 38 and 40 respectively protrude, the movement of the rotary slide member 32 in each axial direction (linear direction) for each brake is small, Operation is stable and durability is improved.

The rotation of the brake is transmitted to the rotary slide member 32 via the input gear 48. The input gear 48 and the rotary slide member 32 are allowed to move relative to each other in the axial direction. The movement of the gear 48 itself in the axial direction is prevented by the holding case 30, so that the gear mechanism 52 from the electric motor 54 to the input gear 48 does not move in the axial direction relative to the gear 48. There is no danger that durability will be impaired.

When the brake rotation of the electric motor 54 is stopped and the power transmission between the electric motor 54 and the rotary slide member 32 is interrupted by the electromagnetic clutch 56, the urging force of the return spring 20 is released. Since the rotary slide member 32 rotates in the reverse direction to allow the pair of brake shoes 16 and 18 to approach each other, it is not necessary to reversely drive the electric motor 54 to release the brake. Further, the screw mechanisms 34, 3
The lead angle of the screw No. 6 is relatively large, but since it is composed of multi-start screws, the screw mechanisms 34, 36 during braking
, A sufficient amount of braking force can be generated.

An electromagnetic clutch 56 which can continuously change the transmission torque by controlling the frictional force with the electromagnetic force.
Is used as a clutch device, so that the transmission torque control and the urging force of the return spring 20 cause AB
According to the S control, the braking force can be controlled very finely with high responsiveness.

Further, since the input gear 48 is disposed at one end side from the axial center position of the holding case 30, that is, at a position shifted toward the output member 40, the input gear 48 is attached to the gear case 50 so as to extend to the other end side. The overall length of the apparatus including the electric motor 54 in the axial direction (the dimension in the left-right direction in FIG. 2) is reduced, and the apparatus is compact.

On the other hand, in this embodiment, a hard shim 70 having a small coefficient of friction is disposed on the reference surface 62f of the case member 62, that is, a portion in contact with the input gear 48, and the rotary slide member 32 is arranged in a straight line. On the other hand, specifically, when moving to the output member 40 side, the input gear 48 is pressed by the shim 70, so that the rotational resistance due to the friction is small and the decrease in the energy efficiency is suppressed. The wear and damage of the input gear 70 and the input gear 48 are suppressed, and the durability is improved. Also, since it is only necessary to dispose the shim 70 on the case member 62, the reference surface 62f
The apparatus is configured at a lower cost as compared with the case where a surface hardening treatment is performed on the device.

Since the shim 70 of the present embodiment has the first disk portion 70a and the second disk portion 70b, the gear provided on the case member 62 according to the diameter of the input gear 48 and the gear 66. Positioning the shim 70 in the accommodation hole only positions it in a fixed position, and does not require a claw or an engagement concave portion for positioning the position. This makes the device simple and inexpensive. Easy.

The embodiments of the present invention have been described in detail with reference to the drawings. However, these are merely examples, and the present invention is based on the knowledge of those skilled in the art. Can be implemented.

[Brief description of the drawings]

FIG. 1 is a front view, partially cut away, showing a main part of a motor-driven drum brake to which the present invention is applied.

FIG. 2 is a sectional view taken along line II-II in FIG.

FIG. 3 is a front view of a shim provided in the apparatus of FIG.

[Description of Signs] 10: Motor-driven drum brake (motor-driven brake) 12: Actuator 14: Backing plate (body-side member) 16, 18: Brake shoe (friction member) 24: Brake drum (brake rotating body) 30: Holding Case (housing) 32: rotary slide member 34, 36: screw mechanism 38, 40:
Output member 48: Input gear 50: Gear case (housing) 52: Gear mechanism 54: Electric motor
70: Shim 70a: 1st disk part 70b: 2nd
Disk part

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3J058 AA03 AA07 AA13 AA17 AA24 AA29 AA33 AA37 BA46 BA78 CC15 CC62 CC77 CD24 CD33 FA01 FA11 FA21

Claims (2)

[Claims] An actuator for a motor-driven brake that generates a braking force by pressing a pair of friction members against a brake rotating body by an electric motor, the housing being fixed to a vehicle body-side member, A rotating slide member disposed in the housing so as to be movable in the direction and rotatable around the straight line, and driven to rotate around the straight line with the rotation of the electric motor for braking; At least one of both ends in the straight line direction is fitted to be rotatable relative to the straight line,
An output member mechanically interposed across the pair of friction members together with the rotary slide member and prevented from rotating around the straight line; and a fitting portion between the output member and the rotary slide member The rotation slide member is rotated around the straight line with the rotation of the electric motor for braking, so that the output member is rotated by the action of a screw associated with relative rotation with the output member. A screw that relatively moves in the linear direction with respect to the member to expand and contract the entire length thereof, and that presses the pair of friction members substantially uniformly to the brake rotor based on the expansion and contraction and the movement of the rotary slide member in the linear direction. And a mechanism, which is disposed on the outer peripheral surface of the rotating slide member so as to be relatively movable in the axial direction and relatively unrotatable about the axis,
An input gear that is prevented from moving in the axial direction by the housing, a gear mechanism that transmits the rotation of the electric motor for braking to the rotary slide member via the input gear, An actuator for a motor-driven brake, comprising: a thin shim provided in a portion in contact with a gear and having a smaller coefficient of friction than the housing. 2. The input gear is a cylindrical gear, and the shim is a first gear located between the input gear and the housing.
The disk portion, and a second disk portion located between the housing and a gear meshing with the input gear are integrally provided in one plane. Motor-driven brake actuator.