JPH07291120A - Electrically operated brake device - Google Patents

Abstract

PURPOSE:To prevent any excessive return of a piston by the inertia of a motor torque at the time of brake release and keep a clearance between a disc pad and a disc always constant and raise the responsiveness of a brake control by installing a clutch between a reversible screw shaft and a motor. CONSTITUTION:When a motor M is driven by an order from ECU 3, its revolution is transmitted to a reversible screw shaft 10 through an output shaft 17 and first/second clutch wheels 15, 14 and thereby a nut 13 and a piston 8 are moved left integrally. The piston 8 push-presses a disc pad 5 to a disc 6 so as to apply a brake. Then, when a push-pressing force to the disc 6 by the disc pad 5 is raised to a prescribed value, the operation of a motor M is stopped by a signal from an electronic control device 3 and a braking state is maintained. When a brake is loosened, the motor M is reversed in its rotation and the nut 13 is moved right through the reversible screw shaft 10 and the brake is released.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrically operated brake device, and more specifically, when the brake is released and the motor is reversely rotated to return the piston, the piston is driven by a rotational force due to inertia of the motor or the like. The present invention relates to a small and light electric brake device that can prevent the pad clearance from becoming too wide due to excessive return.

[0002]

2. Description of the Related Art In recent years, in addition to a hydraulic brake actuation circuit, an electrically actuated brake device (so-called by-wire system) for actuating a brake by an electric signal has been developed. This electrically operated braking device converts the pedal force of the brake pedal into an electric signal and operates the braking device by a signal from an electronic control unit. Therefore, compared to the conventional hydraulic circuit type brake device, it is characterized in that the entire system can be made lighter and smaller, and further various controls of the brake device (anti-skid control, traction control,
There is an advantage that the system can be easily constructed to execute automatic brake control etc.).

As an example of such an electric brake device, an electric motor is used as a drive source to bring a friction member into pressure contact with a member to be braked to obtain a braking force (Japanese Patent Laid-Open No. 63-63).
No. 266228) has been proposed. In the brake device described in the above-mentioned Japanese Patent Laid-Open No. 63-266228, the rotational torque of an ultrasonic motor that drives the rotor to rotate by elastic traveling waves generated by the piezoelectric vibrator on the stator side is controlled by the torque conversion means. The pressure contact force of the friction member with respect to the braking member is converted and transmitted to the friction material. The brake device described in the above publication,
Since the braking force is changed by the ultrasonic motor to perform the braking control, the braking force is small and lightweight, and the required and sufficient braking force can be obtained with a small power consumption. The effect that it can be realized can be expected.

[0004]

However, in the above device, when the brake is released, the so-called pad clearance between the brake disc and the brake pad due to the excessive return of the motor is not controlled.
The gap is not constant, which causes inconvenience such as a decrease in responsiveness at the time of brake operation. Furthermore, in the torque conversion means for converting the rotational torque into the pressure contact force of the friction member with respect to the braked member. There are various problems such as excessive force acting due to excessive return. Therefore, the present invention is
Clutch means is provided between the piston for pressing the brake pad against the brake disc and the motor for driving the shaft for moving the piston, and when the motor excessively rotates when the brake is released, this clutch is Cut
It is an object of the present invention to propose a new electrically operated brake device which can keep the clearance between the brake pad and the brake disc constant by preventing the rotational force due to the inertial force of the motor from being transmitted to the brake pad. In addition, the disengagement of the clutch prevents excessive force from acting on the shaft that drives the piston, and prevents damage to the parts.

[0005]

Therefore, the first technical solution adopted by the present invention is a cylinder 7 formed in the caliper 4 of the brake device, and a slidable piston arranged in the cylinder 7. 8 and a reversible screw shaft 10 for reciprocating the piston 8 toward the disk 6,
A motor 24 for operating the reversible screw shaft, a clutch arranged between the reversible screw shaft and an output shaft of the motor, and an electronic control unit 3 for controlling the motor,
The clutch is characterized in that the rotational force due to the inertia of the motor when the brake is released cannot be transmitted to the piston. The second technical solution means is a cylinder formed in the caliper 4 of the brake device. 7, a slidable piston 8 arranged in the cylinder 7, and a nut 1 pressed against the end surface of the piston 8 with a spring 26.
3, a one-way bearing 23 that holds the nut 13 in the piston so that the nut 13 cannot rotate in the brake operating direction and is rotatable when the brake is opened, and the nut 13 is screwed to the nut 13.
It comprises a reversible screw shaft 10 for reciprocating the piston 8 toward the disk 6, a motor M for operating the reversible screw shaft, and an electronic control unit 3 for controlling the motor. Means that when the brake is applied, the piston moves to the same position when the brake is released, and after the piston returns to the specified position, only the nut moves in the direction away from the piston due to the inertial rotation force of the motor, and the nut rotates together with the screw shaft. The third technical solution is a combination of the one-way bearing 23 and the detent sleeve 24 in the second technical solution. Instead, the cone clutch 33 is used, and after the piston returns to the predetermined position when the brake is released, the cone clutch is rotated by the inertial torque of the motor. Chi is away from the piston, the nut held in the cone clutch is characterized in that can rotate integrally with the screw shaft, it is an unit of the problem solution.

[0006]

[Action]

[First Invention] When the brake pedal is stepped on, the electronic control unit drives the motor M in response to a signal from the pedaling force sensor,
Rotational force is transmitted to the reversible screw shaft via the clutch means. When the reversible screw shaft rotates, the nut and piston move together to the left, pushing the piston while deforming the elastic body, pressing the disc pad against the disc, and applying the brake. When the pressing force applied to the disk 6 by the disk pad 5 reaches a predetermined value, the electronic control unit 3 stops the operation of the motor M based on the signal from the pressing force sensor 20 and maintains the braked state.

When the brake is released, the motor M is reversely operated by the pedaling force signal, and the reversible screw shaft 10 is reversely rotated through the clutch means. The reverse rotation of the reversible screw shaft 10 and the biasing force of the deformed elastic body 12 combine to move the nut 13 and the piston 8 to the right in the drawing, and the braking force is weakened. After that, the reaction force of the disk pad 5 disappears,
Further, when the deformation of the elastic body 12 is restored, the piston 8 stops. At this time, when the motor or the like further rotates due to inertia, the piston 8 is held by the sliding resistance of the elastic body, so the reversible screw shaft 10 and the second clutch wheel resist the urging force of the spring 18 and are left in the figure. The clutch 8 is slightly moved toward the side, whereby the clutch is disengaged and the rotational force from the motor side is disengaged to prevent the piston 8 from returning too much.

[Second Invention] When the brake pedal 1 is stepped on, the electronic control unit 3 drives the motor M in response to a signal from the pedaling force sensor 2, and the rotation of the motor M causes the output shaft 1 of the motor to rotate.
7 is transmitted to the reversible screw shaft 10. At this time, since the one-way bearing 23 does not rotate the nut 13, the nut 13 does not rotate and the nut 13 and the piston 8 move integrally against the urging force of the return spring 22 to move the disk pad 5 Press the disc 6 to apply the brake. Then, when the pressing force of the disk pad 5 on the disk 6 reaches a predetermined value, the pressing force sensor 20 detects this value and outputs it to the electronic control unit 3 to stop the motor and maintain the braking force.

When the brake is released, the pedal force signal causes the motor M to rotate in the reverse direction, the reversible screw shaft 10 rotates in the reverse direction, and the urging force of the return spring 22 moves the piston 8 and the nut 13 to weaken the braking force. further,
When the reversible screw shaft 10 continues to rotate in the reverse direction, the reaction force of the disk pad 5 disappears, and when the return spring 22 returns to its original position, the piston 8 stops. At this time, when the motor further rotates due to inertia, the end surface 1 of the nut 13
Since 3a and the surface 8a of the piston are separated (the clutch means is disengaged), the reversible screw shaft 10 and the nut 13 are integrally rotated by the action of the one-way bearing, and the nut 13 and the reversible screw shaft 10 are separated from each other. Since relative rotation is eliminated, the piston 8 can be prevented from returning too much.

[Third Invention] When the driver steps on the brake pedal, the pedaling force at this time is detected by the pedaling force sensor and is input to the electronic control unit. The motor M is an electronic control unit (E
When controlled and driven by a command from CU), the rotation of the motor M is transmitted to the cone clutch 33 integrated with the output shaft 17 → reversible screw shaft 10 → nut 13 → nut from the motor. At this time, since the cone clutch 33 does not rotate the nut 13, the nut 13 does not rotate and the nut 13,
The piston 8 integrally moves against the urging force of the return spring 22 to the left in the drawing, pushes the piston 8 to the left in the drawing, presses the disk pad against the disk, and brakes. When the pressing force applied to the disk by the disk pad reaches a predetermined value, the pressing force sensor 20 detects this value and outputs it to the electronic control unit to control the braking force such as stopping the motor.

When the brake is released, the motor M is operated in reverse by a pedaling force signal. Then, the reversible screw shaft 10 is reversed, and the urging force of the return spring 22 moves the piston 8 and the nut 13 to the right in the drawing to weaken the braking force. Further, when the reversible screw shaft 10 continues to rotate in the reverse direction, the reaction force of the disc pad 5 disappears, and when the return spring 22 returns to its original position, the piston 8 stops. At this time, when the motor or the like further rotates due to inertia, the cone clutch 33 and the piston 8 are disengaged (clutch means is disengaged).
The nut 13 and the nut 13 rotate as a unit, the relative rotation between the nut and the reversible screw shaft is eliminated, and excessive return of the piston 8 can be prevented.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view of an electrically operated brake device according to a first embodiment of the present invention incorporated in a caliper. In the figure, 1 is a brake pedal, 2 is a pedaling force sensor, 3 is an electronic control unit (ECU), 4 is a brake caliper, 5 is two disc pads, and 6 is a disc arranged between the disc pads. A well-known configuration is used, and a detailed description of those configurations is omitted.

A cylinder 7 is formed in the caliper 4, and a piston 8 is slidably arranged in the cylinder 7. The piston 8 is formed in a cylindrical shape with one end closed, one of the disc pads 5 is attached to the outer surface of the one end, and the piston is provided between the disc pad 5 and the piston 8. The rotation stopping means 9 and the pressing force sensor 20 are provided. A concave groove 11 is formed on the inner peripheral surface of the cylinder 7, and a surface 11 a of the concave groove 11 on the disk pad 5 side is formed in an open tapered shape. An elastic body 12 that also serves as a seal member between the piston 8 and the cylinder 7 is provided in the groove 11. This elastic body 12 is deformed along the inclined surface when the piston 8 moves to the disk pad 5 side during brake operation, and by this deformation, an urging force for returning the piston 8 can be applied. There is.

A nut 13 is fixed to the center of the piston 8, and a reversible screw shaft 10 arranged in line with the axis of the piston 8 is screwed to the nut 13. A second clutch wheel 14 is fixed to the end of the reversible screw shaft 10 opposite to the disc pad 5. A first clutch wheel 15 is arranged so as to face the second clutch wheel 14, and the first clutch wheel 15 is pivotally supported by the caliper 4 via a first thrust bearing 16. The clutch wheels 14 and 15 constitute so-called clutch means.

The first clutch wheel 15 has a motor M.
The output shaft 17 is attached to the caliper 4 while the spring 18 and the second thrust bearing 19 are arranged between the second clutch wheel 14 and the caliper 4. The second thrust bearing 19 is provided so that the second clutch wheel 14 can smoothly rotate without being affected by the biasing force of the spring 18. Therefore, instead of the spring seat, the spring seat can be directly constituted by the caliper, or another modification in which the second thrust bearing is omitted can be adopted if necessary. The second clutch wheel 14 is normally connected to the first clutch wheel 15 by the biasing force of the spring 18, and as a result, the rotational force of the motor M can be transmitted to the reversible screw shaft 10. ing. The holding force R of the elastic body 12 is larger than the axial force f that gives the reversible screw shaft 10 a rotational force, and the load F of the spring 18 is large.
Is set larger than (R>F> f). The output shaft 17 of the motor M, the shafts of the clutch wheels, and the shaft of the reversible screw shaft 10 are coaxially arranged.

The motor M is controlled and driven by a command from the electronic control unit (ECU) 3, and the rotation of the motor M is controlled by the output shaft 17 through the speed reducer of the motor → the first clutch wheel 15 →
When the second clutch wheel 14 is transmitted to the reversible screw shaft 10 and the reversible screw shaft 10 rotates, the nut 13 and the piston 8 move integrally to the left in the drawing,
The piston 8 is pushed to the left in the figure, and the disc pad 5 is pressed against the disc 6 to apply the brake. When the pressing force of the disk pad 5 on the disk 6 reaches a predetermined value, the motor M stops its operation in response to a signal from the electronic control unit 3 and maintains the braked state.

The operation of the electrically operated brake device having the above structure will be described. Since there is no command from the electronic control unit 3 before the brake is actuated, this brake unit is shown in FIG.
It is in the state of. When the driver steps on the brake pedal 1, the tread force at this time is detected by the tread force sensor 2 and is input to the electronic control unit 3. In the electronic control unit 3, the motor M is driven according to the input signal, and the output shaft 1 from the motor is output.
7 → first clutch wheel 15 → second clutch wheel 14 → transmitted to the reversible screw shaft 10, and when the reversible screw shaft 10 rotates, the nut 13 and the piston 8 move integrally to the left in the figure, and While deforming the body 12, the piston 8 is pushed to the left in the figure, the disc pad 5 is pushed against the disc 6, and the brake is applied. At this time, since the braking force becomes stronger and the connecting force of the clutch means increases, the first and second clutch wheels 15 and 14 do not slip. Since the elastic body 12 is deformed along the inclined surface 11a of the concave groove 11, the piston 8
Is given a biasing force to the right in the figure. When the pressing force of the disk pad 5 on the disk 6 reaches a predetermined value, the pressing force sensor 20 detects this value and outputs it to the electronic control unit 3. The electronic control unit 3 stops the operation of the motor M based on the signal from the pressing force sensor 20 and maintains the braked state.

When the brake is released, the motor M is operated in reverse by a pedaling force signal. Then, the reversible screw shaft 10 is reversely rotated through the clutch means, and when the reversible screw shaft 10 is reversely rotated, the nut 13 and the piston 8 are moved rightward in the figure together with the deformed urging force of the elastic body 12. Braking force is weakened. Further, when the reversible screw shaft 10 continues to rotate in the reverse direction, the reaction force of the disk pad 5 disappears, and further, when the deformation of the elastic body 12 returns to the original state, the piston 8 stops. At this time, when the motor or the like further rotates due to inertia, the piston 8 is held by the sliding resistance of the elastic body, so the reversible screw shaft 10 and the second clutch wheel resist the urging force of the spring 18 and are left in the figure. The clutch 8 is slightly moved toward the side, whereby the clutch is disengaged and the rotational force from the motor side is disengaged to prevent the piston 8 from returning too much. Although the second clutch wheel is temporarily separated from the first clutch wheel, the reversible screw shaft 10 is rotated by the urging force of the spring 18 to return to the original position, and the clutch wheels are brought into the connected state again to return to the initial state. Return.

Next, an electrically operated brake device according to a second embodiment of the present invention will be described with reference to FIG. The second embodiment is different from the first embodiment only in the clutch mechanism incorporated in the caliper, and the other configurations are the same, so the description of the common configuration functions will be omitted. In the figure, a cylinder 7 is formed in the caliper 4, and a piston 8 is slidably arranged in the cylinder 7. The piston 8 is formed in a cylindrical shape with one end closed, one of the disc pads 5 is attached to the outer surface of the one end, and the piston is provided between the disc pad 5 and the piston 8. Rotation stopping means 9 and pressing force sensor 20
Is provided. A spring accommodating groove 27 is formed in the inner peripheral surface of the cylinder 7, and a return spring 22 is provided in the spring accommodating groove 27 via a sliding ring 21 with the piston 8.

A nut 13 is arranged in the center of the piston 8, and the nut 13 is not rotated in the pressurizing direction via a rotation preventing sleeve 24 between the nut 13 and the inner surface of the piston 8. The one-way bearing 23 that allows the nut 13 to rotate only in the return direction is arranged.
Further, the end surface 13a of the nut 13 and the surface 8a formed on the piston form a clutch means which is constantly pressed by the spring 26 as shown in the figure. A reversible screw shaft 10 arranged so as to match the axis of the piston 8 is screwed to the nut 13, and an end portion of the reversible screw shaft 10 opposite to the disc pad 5 is provided with a first thrust bearing 16 It is pivotally supported by the caliper 4 via. The end of the reversible screw shaft 10 is attached to the output shaft 17 from the motor M. The reversible screw shaft 10 is restricted from moving in the axial direction by a stop ring 25 provided on the caliper.

The operation of the electrically operated brake device having the above structure will be described. Since there is no command from the electronic control unit 3 before the brake is actuated, this brake unit is shown in FIG.
It is in the state of. When the driver steps on the brake pedal 1, the tread force at this time is detected by the tread force sensor 2 and is input to the electronic control unit 3. When the motor M is controlled and driven by a command from an electronic control unit (ECU), the rotation of the motor M rotates from the output shaft 17 from the motor to the reversible screw shaft 10.
→ Transmitted to the nut 13. At this time, one-way bearing 2
3 does not rotate the nut 13, so that the nut 13 does not rotate and the nut 13 and the piston 8 integrally move against the urging force of the return spring 22 to the left in the drawing to move the piston 8 to the left. Push it to the left in the middle, press the disc pad 5 against the disc 6, and apply the brake. When the pressing force of the disk pad 5 on the disk 6 reaches a predetermined value, the pressing force sensor 20 detects this value and outputs it to the electronic control unit 3 to control the braking force such as stopping the motor.

When the brake is released, the motor M is reversely operated by the pedaling force signal. Then, the reversible screw shaft 10 is reversed, and the urging force of the return spring 22 moves the piston 8 and the nut 13 to the right in the drawing to weaken the braking force. Further, when the reversible screw shaft 10 continues to rotate in the reverse direction, the reaction force of the disc pad 5 disappears, and when the return spring 22 returns to its original position, the piston 8 stops. At this time, when the motor or the like further rotates due to inertia, the piston is held by the sliding resistance of the sliding ring 21, so that the end surface 13a of the nut 13 and the surface 8a of the piston are separated (the clutch means is disengaged). By the action of the one-way bearing, the reversible screw shaft 10 and the nut 13 rotate integrally, and the relative rotation between the nut and the reversible screw shaft is eliminated, and the piston 8 can be prevented from returning too much.

Further, an electrically operated brake device according to a third embodiment of the present invention will be described with reference to FIG. A third embodiment is the one-way bearing 23 in the second embodiment,
A cone clutch 33 is adopted instead of the combination with the rotation preventing sleeve 24, and after the piston returns to a predetermined position when the brake is released, the cone clutch 33 separates from the piston 8 by the inertial rotational force of the motor, and the cone clutch 33 The held nut can rotate together with the screw shaft, and other configurations are the same as those in the second embodiment. In the figure, 19 'is the cone clutch 3
3 is a thrust bearing provided between the spring 3 and the spring 26.

The operation of the electrically operated brake device according to the above configuration will be described. When the driver steps on the brake pedal, the pedaling force at this time is detected by the pedaling force sensor and input to the electronic control unit. The motor M is an electronic control unit (EC
When controlled and driven by a command from U), the rotation of the motor M is transmitted to the cone clutch 33 integrated with the output shaft 17 → reversible screw shaft 10 → nut 13 → nut from the motor. At this time, since the cone clutch 33 does not rotate the nut 13, the nut 13 does not rotate and the nut 13 and the piston 8 integrally move to the left in the figure against the biasing force of the return spring 22, Push the piston 8 to the left in the figure,
Apply the brake by pressing the disc pad against the disc. When the pressing force applied to the disk by the disk pad reaches a predetermined value, the pressing force sensor 20 detects this value and outputs it to the electronic control unit to control the braking force such as stopping the motor.

When the brake is released, the motor M is reversely operated by the pedaling force signal. Then, the reversible screw shaft 10 is reversed, and the urging force of the return spring 22 moves the piston 8 and the nut 13 to the right in the drawing to weaken the braking force. Further, when the reversible screw shaft 10 continues to rotate in the reverse direction, the reaction force of the disc pad 5 disappears, and when the return spring 22 returns to its original position, the piston 8 stops. At this time, when the motor or the like further rotates due to inertia, the cone clutch 33 and the piston 8 are disengaged (clutch means is disengaged).
The nut 13 and the nut 13 rotate as a unit, the relative rotation between the nut and the reversible screw shaft is eliminated, and excessive return of the piston 8 can be prevented.

As described above, in the present invention, the piston and
Clutch means is provided between the piston and a motor for driving the piston, and the clutch means can prevent excessive return of the piston due to overrun of reverse rotation of the motor that occurs when the brake is loosened, and excessive force acts on the reversible screw shaft. Can be prevented. Further, in the present invention,
Pressurization of braking force by control signal from electronic control unit,
Since it is possible to hold and reduce the pressure, it is possible to execute anti-skid control and traction control. In addition,
In the embodiment, the pedaling force sensor may be provided anywhere, and the elastic body 12 in the first embodiment may be the spring 22 and the sliding ring 21 in the second embodiment, or the second,
The spring 22 and the sliding ring 21 in the third embodiment may be the elastic body 12 as in the first embodiment. Further, signals from the pressing force sensor 20 and the brake pedal pedal force sensor 2 are transmitted to the electronic control unit 3, and the electronic control unit 3 controls the motor 24 based on these signals. Further, without using the pressing force sensor 20, the pressing force applied to the disk 6 by the disk pad 5 is detected from the load applied to the motor,
The motor can also be controlled as described above. Further, the present invention is not limited to the above embodiment, and any mechanism can be applied as long as it has a similar function.

[0027]

As described above in detail, according to the present invention, by providing the clutch between the reversible screw shaft and the motor, the piston does not return too much due to the inertia of the motor rotating force when the brake is released, and the disc is prevented. The gap between the pad and the disc can always be kept constant. As a result, the responsiveness of the brake control is improved. Further, since it is possible to prevent an excessive force from being applied to the screw portion due to the rotational force of the motor, it is possible to prevent the device from being damaged. Further, the device can be manufactured in a small size and at low cost. Furthermore, anti-skid control, traction control, etc. can be easily realized by the control by the electronic control unit. It is possible to achieve excellent operational effects such as.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of an electrically operated brake device as a first embodiment according to the present invention.

FIG. 2 is a schematic sectional view of an electrically operated brake device as a second embodiment according to the present invention.

FIG. 3 is an explanatory diagram of unidirectional bearing.

FIG. 4 is a schematic sectional view of an electrically operated brake device as a third embodiment according to the present invention.

[Explanation of symbols]

 1 brake pedal 2 pedal force sensor 3 electronic control device 4 caliper 5 disc pad 6 disc 7 cylinder 8 piston 9 detent means 10 reversible screw shaft 11 recessed groove 12 elastic body 13 nut 14, 15 second, first clutch wheel 17 reducer Output shaft of (motor) 18 Spring 19 Thrust bearing 20 Pressure sensor

Claims (6)

[Claims] 1. A cylinder 7 formed in a caliper 4 of a brake device, a slidable piston 8 arranged in the cylinder 7, and a reversible screw for reciprocating the piston 8 toward a disk 6. A shaft 10, a motor M for operating the reversible screw shaft 10, and clutches 14, 1 arranged between the reversible screw shaft 10 and an output shaft 17 from the motor.
5 and an electronic control unit 3 for controlling the motor, wherein the clutches 14 and 15 are arranged so that the rotational force of the motor after the brake is released cannot be transmitted to the reversible screw shaft 10. Brake device. 2. A cylinder 7 formed in a caliper 4 of a brake device, a slidable piston 8 arranged in the cylinder 7, and a reversible screw for reciprocating the piston 8 toward a disk 6. It includes a shaft 10, a motor M that operates the reversible screw shaft 10, a nut 13 that engages with the reversible screw shaft 10, a bearing 23 that supports the nut, and an electronic control unit 3 that controls the motor. The bearing 23 has a one-way clutch that supports the nut 13 non-rotatably when the reversible screw shaft 10 rotates in the braking direction and allows the nut 13 to rotate when the reversible screw shaft 10 rotates in the opposite direction. When the reversible screw shaft 10 rotates in the brake releasing direction after releasing the brake, the face 8a of the piston and the face 23a of the nut are separated from each other. And the reversible screw shaft 10 and the electrically operated braking device is characterized in that the manner to rotate integrally. 3. A cylinder 7 formed in a caliper 4 of a brake device, a slidable piston 8 arranged in the cylinder 7, and a reversible screw for reciprocating the piston 8 toward a disk 6. A shaft 10, a motor M that operates the reversible screw shaft 10, a nut 13 that engages with the reversible screw shaft 10, a cone clutch 33 integrated with the nut, and an electronic control unit 3 that controls the motor. The cone clutch 33 separates from the face 8a of the piston for rotation of the reversible screw shaft 10 in the brake releasing direction after releasing the brake, and the nut 13 and the reversible screw shaft 10 are integrated. An electrically operated braking device characterized in that it is adapted to rotate. 4. The clutch means has a first clutch wheel 15 provided on the output shaft side of the motor and a second clutch wheel 14 provided on the reversible screw shaft side, and the second clutch wheel 14 is First clutch wheel 1
The electrically operated brake device according to claim 1, wherein the electrically operated brake device is pressed toward the spring 5 and its load is set to be lower than the sliding resistance between the friction ring 12 and the piston 8. 5. The bearing 23 includes a detent sleeve 24.
Is supported on the piston 8 by the detent sleeve 24.
It is slidably and non-rotatably engaged with and is pressed toward the pad by the spring 26, and its load is set to be lower than the sliding resistance between the friction ring 21 and the piston 8. The electrically operated braking device according to claim 2. 6. The cone clutch 33 holding the nut 13 is pressed against a cone surface formed on the piston 8 by a spring 26, and the load thereof causes a sliding resistance between the friction ring 21 and the piston 8. The electrically operated brake device according to claim 3, wherein the electrically operated brake device is set lower than the above.