JPH06327190A - Actuator for electrically driven brake - Google Patents

Abstract

PURPOSE:To enhance the reliability of an apparatus at low costs by properly keeping the interval between a brake pad and a brake disk irrespective of the wear of the pad. CONSTITUTION:The title actuator is provided with a screw part 140 and a one-way clutch 160 in such a way that they are coupled to the output side of a gear part 130 which decelerates and transmits the rotation of a torque- controlled motor part 110 turned forward and reversely by a motor current, that they advance a screw shaft 142 by the forward and reverse rotation of a screw nut 141 and that they bring a brake pad into pressure contact with a disk brake at a wheel by a pressurization member 147 so as to be braked or that the pressurization member 147 is retreated so as to release its braking. Then, the title actuator is provided with a spline part 150 in such a way that, when the screw nut 141 is turned to the pressurization direction, that the rotation of the screw shaft 142 is locked, that the screw nut 141 is turned to the reverse direction and that, when the frictional force between a friction member 147 and the brake pad is lowered to an idly turned extent, that the screw shaft 142 is made free.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric brake actuator that is mounted behind a wheel brake pad in a vehicle and electrically brakes under pressure.

[0002]

2. Description of the Related Art A hydraulic brake device is generally used in a vehicle. This hydraulic brake device 600
When the brake pedal 601 is depressed as shown in FIG. 6, the stepping force is increased by the booster 602 using the engine negative pressure.
The brake fluid pressure 607 in the master cylinder 603 and the brake fluid pressure 607 is increased by the caliper 6
To the wheel cylinder 604 configured in 08.
Also, the wheel cylinder 604 has a piston 605,
Piston seal 606 fixed to caliper 608
Is movably inserted in a sealed state so as to prevent leakage of the brake fluid 607, the piston 605 is moved by the brake fluid pressure 607, and the brake pad 609 is pressed against the brake disc 610, It is configured to brake the connected wheels 611.

Here, the piston seal 606 of the wheel cylinder 604 is deformed as shown in FIG. 7 when the piston 605 moves in the wheel cylinder 604, and also functions as a return spring as well as a hydraulic seal to release the brake. At this time, the piston seal 606 functions to return the piston 605 by a certain amount from the position where the brake pad 609 hits the brake disc 610.
Therefore, even if the brake pad 609 wears and the piston position changes, the brake disc 6 is not braked.
The distance between 10 and the brake pad 609 is properly maintained.

By the way, in the hydraulic brake device,
It requires a negative pressure source such as an engine. Therefore, for example, in a vehicle such as an electric vehicle that does not have a negative pressure source, it is required to generate negative pressure or hydraulic pressure by an electric pump to double the pressure. Here, if an electric pump is used, it is more efficient to apply the braking action directly by electric power. Therefore, in recent years, an electric brake device has been proposed as a vehicle brake device.

Conventionally, with respect to the above electric brake device,
For example, there is a "electric brake device for a vehicle" disclosed in Japanese Patent Application Laid-Open No. 3-57755. In this prior art, an electric actuator is connected to the brake pad, and the brake pad is provided with a brake pad position detector and a brake pad load detector. Then, the actuator control device processes a signal corresponding to a brake operation and a signal from the detector, outputs a control signal to the electric actuator, and electrically presses or releases the brake pad against the brake disc. Is disclosed.

[0006]

However, in the above-mentioned prior art, only the outline of the mounting of the electric actuator and the control of the actuator are shown.
No specific configuration of the actuator is disclosed.
Also, since the pressurization and return of the electric actuator are controlled based on the signal of the brake pad position and the brake pad load, a stroke sensor or the like is required,
There is a problem that the cost of the device itself becomes high. Further, if the sensor fails, the brake may be dragged due to insufficient clearance between the brake pad and the brake disc, or conversely, the rising of the braking force may deteriorate due to the excessive clearance between the brake pad and the brake disc, resulting in reliability of the device. However, there is a problem that it causes deterioration of sex.

The present invention has been made in view of the above, and constitutes an electric brake actuator that appropriately pressurizes or releases a brake pad by driving a motor,
Another object of the present invention is to improve the reliability of the device at a low cost by maintaining an appropriate gap between the brake pad and the brake disc regardless of wear of the brake pad even without a stroke sensor.

[0008]

In order to achieve the above object, the present invention relates to a motor which is normally and reversely rotated by a motor current and which is torque controlled, a gear means for decelerating and transmitting the rotation of the motor, and the gear. A screw nut connected to the output side of the means, a screw shaft screw-fitted to the screw nut, and a pressure member connected to the end of the screw shaft, and the screw shaft is moved forward and backward by the screw nut. , The brake pad is pressed and brought into contact with the brake disc of the wheel by the pressurizing member for braking, or the pressurizing member is retracted to release the braking, and the spline is movable to the screw shaft of the screw means. With a spline nut to be fitted and a one-way clutch attached to the spline nut, the screw nut rotates in the pressurizing direction. And a spline means for locking the rotation of the screw shaft, rotating the screw nut in the opposite direction, and freeing the screw shaft when the frictional force of the pressure member decreases to the extent of idling. Is provided.

In the screw nut, the screw shaft is integrally connected to the output side of the gear means, the screw nut is screw-fitted to the screw shaft, and a spline shaft is connected to the screw nut, and the spline shaft is connected to the spline shaft. The spline means is mounted, and the pressing member is connected to the end portion of the spline shaft.

[0010]

According to the above construction, when the brake is operated, the motor is driven by the motor current and the rotation of the motor is reduced by the gear means and transmitted to the screw nut of the screw means. In this case, the one-way clutch is operated by the rotating direction of the screw nut. Lock the rotation of the screw shaft. Therefore, the screw shaft moves forward by the forward rotation of the screw nut, and the pressure pad presses the brake pad against the brake disc of the wheel to brake. When the brake operation is released, the motor rotates in the reverse direction. At this time, a large frictional force is generated between the pressure member and the brake pad, and when the frictional force suppresses the rotation of the screw shaft, the reverse rotation of the screw nut occurs. As a result, the screw shaft retracts, and the braking force becomes zero with the deformation of the brake pad and the like canceled. Further, when the frictional force of the pressure member decreases to such an extent that it spins, the one-way clutch frees the screw shaft at this point, and the pressure member is always stopped and held right behind the brake pad.
Therefore, when the brake pad wears and becomes thinner, the stop position of the pressing member also moves accordingly. Thus, the gap between the brake disc and the brake pad is properly maintained regardless of the wear of the brake pad.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic configuration of an electric brake actuator. Electric brake actuator 100
Has a cylindrical case 101 whose both ends are substantially closed, a motor section 110 is arranged substantially in the inside of the case 101, a gear section 130 and a screw section 140 are arranged on the left side of the motor section 110, and a right side is arranged. The spline section 150 is arranged in the.

The motor unit 110 has a DC inside the case 101.
The motor 111 is attached. The motor 111 includes a permanent magnet 112 fixed to the case side, a hollow rotor 114 rotatably disposed on the center of the case with a bearing 113 on one side, and a winding 115 wound around the rotor 114. The winding 115 is electrically connected to the commutator 116 attached to the rotor 114. The commutator 116 has a brush 1
17 is held by the brush case 118 on the case 101 side and slidably contacted by a constant pressing force of the spring 119, and the brush 117 is connected to the control device side by a conducting wire 120. Then, by supplying a motor current to the winding 115 by the brush 117 and the commutator 116, the rotor 114 of the motor 111 is rotated normally and reversely, and the rotational torque is controlled.

The gear portion 130 is a planetary gear, and has a sun gear 131 formed on one end of the rotor 114 and a ring gear 13 formed on the case 101.
2, a pinion 133 that meshes with the sun gear 131 and the ring gear 132, and a carrier 135 that supports the pinion 133 with a bearing 134. And the rotor 114
Thus, when the sun gear 131 rotates, the pinion 133 revolves around its own axis to rotate the carrier 135 in the same direction as the rotor 114 at a predetermined gear ratio.

The screw portion 140 is provided with a screw nut 141 which is integral with the carrier 135 of the gear portion 130, and a screw shaft 142 which is installed by being inserted through the inside of the rotor 114 at the center of the case 101. The screw nut 141 is supported by a bearing 143 on the case 101 side so as to rotate smoothly and not move in the axial direction, and a screw groove 145 is formed in a central hole 144. A thread groove 146 is formed in a predetermined range on the outer circumference of the screw shaft 142, and one end of the screw shaft 142 projects to the outside of the case 101 and a pressure member 147 is attached. The pressing member 147 is provided with a friction member 147a. Here, in order to reduce the sliding resistance of the screw nut 141 and the screw groove engaging portion of the screw shaft 142,
5, 146 are configured to mesh with each other via balls 148. When the screw nut 141 is rotated forward and backward integrally with the carrier 135 of the gear unit 130, and the screw shaft 142 is axially movable and rotationally locked at this time,
The screw shaft 142 is moved forward or backward. Further, when the screw shaft 142 becomes free, the screw nut 141 and the screw shaft 142 integrally rotate idly.

The spline part 150 is disposed on the opposite side of the screw part 140 of the motor part 110, and is mounted between the spline nut 152 and the case 101 and the spline nut 152, which is rotatably supported by a bearing 151 on the case side. The one-way clutch 160 is provided. The hole 153 at the center of the spline nut 152 has an axial groove 154.
Are formed, and axial grooves 155 are formed in a predetermined range on the outer periphery of the screw shaft 142. These axial grooves 154, 15
5 meshes with the ball 156 while reducing the sliding resistance. Also, the spline nut 152 and the screw shaft 1
42 moves relatively in the axial direction and is integrated in the rotating direction.

The one-way clutch 160 is, as shown in FIG. 2, an inner ring 201 fixed to the spline nut 152, an outer ring 202 fixed to the case 101, and a rotation provided so as to be inclined between the rings 201, 202. A control member 203 is provided. When the screw shaft 142 rotates as shown by the arrow in FIG. 2, the rotation control member 203 tilts and becomes free. When the screw shaft 142 rotates in the opposite direction, the rotation control member 203 stands up. The fixed outer ring 202 locks the rotation of the screw shaft 142.

The mounting state of the actuator 100 will be described with reference to FIG. The brake disc 301 of the wheel 300 has a brake pad 303 of a caliper 302.
Are arranged close to each other so as to apply pressure. Therefore, the actuator 100 is placed in the inner chamber 304 of the caliper 302 while the friction member 147a of the pressing member 147 is in close proximity to and behind the brake pad 303.
It is fixed by 5. The control system of the electric brake device will be described with reference to FIG. In the electric brake device, the brake pedal 401 is provided with a sensor 402 for detecting a pedaling force and a stroke, and the sensor signal is input to the control circuit 403. Further, signals from the vehicle speed sensor 404 and the wheel speed sensor 405 (405a to 405d) are also input to the control circuit 403, respectively. The control circuit 403 inputs and processes signals of the pedal depression force, the vehicle speed, and the wheel speed, and calculates the braking force required for the four wheels when the brake is operated under various traveling conditions. When the DC motor 111 is used, a torque proportional to the motor current is generated. Therefore, the motor current can directly control the motor torque and the brake pad pressure, that is, the braking force. Therefore, the motor current required to generate a predetermined braking force is calculated for each wheel. Then, the motor currents are supplied to the actuators 100 (100a to 100d) mounted on the four wheels FL, FR, RL, and RR, respectively. In this case, the brake feeling can be freely changed by arbitrarily setting the relationship between the pedal depression force and the braking force.

Next, the operation will be described. When the driver depresses the brake pedal 401, an appropriate motor current is calculated by the control circuit 403 based on the pedal depression force, vehicle speed, and wheel speed information in this case, and the motor current flows to the motor 111. Therefore, the motor 11
1, the rotor 114 rotates, for example, as shown by the arrow in FIG. 1, and this rotation is reduced to the screw nut 141 of the screw portion 140 via the sun gear 131 of the gear portion 130, the pinion 133, and the carrier 135. It is transmitted as rotation in the same direction. The rotation of the screw nut 141 is further transmitted to the screw shaft 142 and tries to rotate in the same direction. In the spline portion 150, the rotation of the screw shaft 142 is transmitted to a spline nut 152 that is integral with the screw shaft 142 in the rotation direction, and the spline nut 152 tries to rotate in the direction opposite to the arrow shown in FIG. Therefore, the one-way clutch 160 automatically locks the rotation of the screw shaft 142 together with the spline nut 152. Therefore, in the screw portion 140, the screw shaft 142 is axially movable by the spline portion 150, but is supported in a rotationally locked state. Therefore, as the screw nut 141 rotates, the balls 148 and the screw grooves 145, 146 are rotated. The screw shaft 142 smoothly moves to the left due to the meshing of. The pressure member 147 attached to the tip of the screw shaft 142
Friction member 147a of the brake pad 303
Is pressed against the brake disc 301 of the wheel 300 to apply a braking force. In this way, the wheels 300 are braked.

In this case, when the motor torque is TM, the gear ratio of the gear portion 130 is G, and the lead of the screw portion 140 is R, the pressing force F is expressed by the following equation. That is, F = TM · G · 2π / R. Therefore, for example, the maximum torque of the motor 111 is 1
When 0 (kgf-cm), the gear ratio of the gear portion 130 is 5, and the lead of the screw portion 140 is 2, a pressing force of 1571 (kgf) is generated. Therefore, it is possible to sufficiently cover the normal range in the case of the hydraulic brake device.

Further, when the brake is released, the braking force theoretically becomes zero by making the motor current zero, but it is necessary to cancel the deformation of the brake pad 303 and the caliper 302. Therefore, the control circuit 403 causes the motor current to flow in the opposite direction to rotate the motor 111 in the reverse direction. As a result, this reverse rotation is transmitted to the spline portion 150 via the gear portion 130, the screw portion 140 and the screw shaft 142, and tries to free the one-way clutch 160. By the way, the friction member 147a of the pressure member 147
Is in contact with the brake pad 303, the rotation of the screw shaft 142 is suppressed by the frictional force between the friction member 147a and the brake pad 303. Therefore, the screw shaft 142 moves to the right due to the reverse rotation of the motor 111, the pressure member 147 (and the friction member 147a) retracts, and the pressure applied to the brake pad 303 decreases.

When the frictional force of the friction member 147a decreases to the extent that the screw shaft 142 idles, the screw shaft 142 becomes free by the one-way clutch 160 at this point. Therefore, the screw nut 141 and the screw shaft 142 rotate integrally, and the pressurizing member 147 does not retract further, and stops immediately behind the brake pad 303. In this way, the pressing member 147 is retracted to the extent of idling, so that the deformation of the brake pad 303 and the caliper 302 is eliminated and the braking force becomes substantially zero. At this time, even if the motor reverse current flows for a relatively long time, the one-way clutch 160 causes the pressurizing member 147 to move to the brake pad 30.
It is held in a stopped state immediately after 3. Further, when the brake pad 303 gradually wears and becomes thinner, the stop position of the pressure member 147 during non-braking also gradually moves forward, thus the pressure member position is automatically corrected, and the brake pad The distance between the brake disc and the brake disc is always maintained properly. Therefore, during non-braking, the drag of the brake is reliably prevented. Further, at the time of the next braking operation, the pressure member 147 does not need to make unnecessary stroke movement, and the friction member 147a of the pressure member 147 immediately presses the brake pad 303 to brake properly.

Another embodiment of the actuator according to the present invention will be described with reference to FIG. In this embodiment, the motor unit 110 is arranged at the rearmost inside the case 101 of the actuator 100.
The gear portion 130, the screw portion 140, and the spline portion 150 are sequentially arranged on the pressure member side. The motor unit 110 and the gear unit 130 are configured in the same manner as in FIG. On the other hand, screw part 1
In FIG. 40, the screw shaft 142 is integrally formed with the carrier 135 of the gear unit 130, and the screw shaft 142 is provided with screw grooves 145, 146 and balls 148.
41 mesh with each other, and the spline shaft 50 is attached to the screw nut 141.
1 are connected in series, and the screw nut 141 and the spline shaft 501 are axially moved by the rotation of the screw shaft 142.

Further, a spline nut 152 is mounted on the spline shaft 501 via axial grooves 154, 155 and balls 156 of the spline portion 150, a one-way clutch 160 etc. is mounted on the spline nut 152, and the spline shaft 501 is a case. And is connected to the pressing member 147. The same parts as those in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted.

Next, the operation of the above embodiment will be described. When the motor 111 of the motor unit 110 is driven during brake operation, the rotation of the motor 111 is decelerated by the gear unit 130, input to the screw shaft 142 of the screw unit 140, and transmitted from the screw shaft 142 to the screw nut 141 and the spline shaft 501. Further, in the case of normal rotation of the screw shaft 142, the one-way clutch 160 locks the rotation of the spline shaft 501 together with the spline nut 152. Therefore, the rotation of the screw shaft 142 moves the spline shaft 501 to the left. The braking member 147a of the pressure member 147 presses the brake pad 303 to execute the braking operation. When the motor 111 rotates in the reverse direction when the brake is released, the friction member 1 of the pressure member 147 is also rotated.
In a state in which 47a is in contact with the brake pad 303 and is rotationally locked, the spline shaft 501 and the pressure member 147 are retracted by the reverse rotation of the screw shaft 142. After that, when the friction force of the friction member 147a of the pressure member 147 decreases to the extent of idling, the one-way clutch 160 frees the spline nut 152 and the spline shaft 501, and the pressure member 147 is stopped and held at a position immediately after the brake pad 303. To be done.

Although the embodiment of the present invention has been described above, the present invention is not limited to this. For example, the motor only needs to be capable of torque control, and an AC motor can also be used. The screw part and spline part may be slip type without using balls. Further, the spline portion may have a structure using balls.

[0026]

As described above, according to the actuator for an electric brake of the present invention, a motor which is normally / reversely rotated by the motor current and whose torque is controlled, and a gear means for decelerating and transmitting the rotation of the motor, A screw nut connected to the output side of the gear means, a screw shaft screw-fitted into the screw nut, and a pressurizing member connected to the end of the screw shaft, and the screw shaft is rotated by the forward and reverse rotation of the screw nut. It is possible to move to the screw means that moves forward and presses the brake pad against the brake disc of the wheel by the pressing member to brake, or moves the pressing member backward and releases the braking and the screw shaft of the screw means. A spline nut fitted to the spline, and a one-way clutch attached to the spline nut. And the screw shaft rotates in the opposite direction, the screw nut rotates in the opposite direction, and when the frictional force of the pressure member decreases to the degree of idling, the spline means for freeing the screw shaft is provided. Also, the screw nut is integrally connected to the output side of the gear means, the screw nut is screw-fitted to the screw shaft, and the spline shaft is continuously provided to the screw nut. Since the spline means is mounted on the shaft and the pressure member is connected to the end of the spline shaft, an electric brake actuator that appropriately pressurizes or releases the brake pad by a motor drive is constructed, and the stroke is further increased. Between the appropriate brake pad and brake disc regardless of wear of the brake pad even without sensors etc. It can be inexpensively improved to the reliability of the device held in the.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a schematic configuration of an electric brake actuator according to the present invention.

FIG. 2 is an explanatory diagram showing a schematic configuration of a one-way clutch.

FIG. 3 is an explanatory diagram showing a mounted state of the actuator.

FIG. 4 is an explanatory diagram showing a control system of the electric brake device.

FIG. 5 is an explanatory view showing another embodiment of the electric brake actuator according to the present invention.

FIG. 6 is an explanatory diagram showing a schematic configuration of a conventional hydraulic brake device.

FIG. 7 is an explanatory view showing the operation of the piston seal shown in FIG.

[Explanation of symbols]

 100 electric brake actuator 110 motor part 130 gear part 140 screw part 147 pressurizing member 147a friction member 150 spline part 152 spline nut 160 one-way clutch 300 wheels 301 brake disc 303 brake pad 401 brake pedal 402 sensor 404 vehicle speed sensor 405 wheel speed sensor 501 spline shaft

Claims (2)

[Claims] 1. A motor which is normally / reversely rotated by a motor current and whose torque is controlled, gear means for decelerating and transmitting rotation of the motor, a screw nut connected to an output side of the gear means, and a screw fitting to the screw nut. A screw shaft to be fitted, and a pressurizing member connected to an end of the screw shaft, the screw shaft is moved forward by the forward and reverse rotation of the screw nut, and the brake pad is pressed against the brake disc of the wheel by the pressurizing member. A screw means for releasing the braking by bringing them into contact with each other or braking the pressure member, a spline nut movably spline-fitted to a screw shaft of the screw means, and a one-way clutch attached to the spline nut. When the screw nut rotates in the pressurizing direction, the rotation of the screw shaft is locked, and the screw nut is rotated. And a spline means for freeing the screw shaft when the friction force of the pressurizing member is reduced to an extent such that the pressing force rotates in the opposite direction. 2. The screw nut, wherein the screw shaft is integrally coupled to an output side of the gear means, the screw nut is screw-fitted to the screw shaft, and a spline shaft is connected to the screw nut, and the spline shaft is connected to the spline shaft. The actuator for an electric brake according to claim 1, wherein the spline means is mounted, and the pressing member is connected to an end portion of the spline shaft.