WO2019225456A1

WO2019225456A1 - Actuator for electric parking brake

Info

Publication number: WO2019225456A1
Application number: PCT/JP2019/019444
Authority: WO
Inventors: 卓志松任; 川合　正浩; 慎太朗石川
Original assignee: Ntn株式会社
Priority date: 2018-05-21
Filing date: 2019-05-16
Publication date: 2019-11-28
Also published as: JP2019203518A

Abstract

Provided is an actuator for an electric parking brake, which is provided with an electric motor 21, a speed reduction mechanism 30, and a rectilinear motion mechanism 40, and which converts, by means of the rectilinear motion mechanism 40, the rotational motion of the electric motor 21, the speed of which has been reduced by the speed reduction mechanism 30, into rectilinear motion, thereby pressing brake pads 3, 4 against a brake disc 2 to generate braking force on a wheel. The actuator is provided with a first sprocket 22 which is disposed coaxially with the electric motor 21, a second sprocket 23 which is disposed parallel to the axis of the first sprocket 22, and a chain 24 which transmits rotational motion between the first sprocket 22 and the second sprocket 23. The speed reduction mechanism 30 is formed as an eccentric type speed reduction mechanism which has an eccentric section 32 moved eccentrically by rotational motion transmitted from the electric motor 21, the speed reduction mechanism 30 reducing the speed of the rotational motion applied to the eccentric section 32 and transmitting the rotational motion.

Description

Electric parking brake actuator

The present invention relates to an actuator used for pressing a brake pad of an electric parking brake device against a brake disc.

In electric parking brake actuators mounted on automobiles and the like, small electric motors tend to be used in response to demands for space saving and weight reduction. On the other hand, since a small electric motor has a small output, generally, a reduction mechanism is used to decelerate and transmit the rotational motion of the electric motor so that a sufficient output can be obtained.

For example, the following Patent Document 1 discloses a speed reduction mechanism using a plurality of spur gears as a speed reduction mechanism provided in an actuator for an electric parking brake.

Japanese Patent No. 6013016

By the way, when an actuator having a speed reduction mechanism is arranged in a wheel of a wheel, the actuator can be accommodated in a limited space while avoiding interference with peripheral members such as a knuckle, a damper and a steering tie rod that support the wheel. Therefore, further downsizing of the actuator is an important issue.

However, in the configuration using the speed reduction mechanism composed of a plurality of spur gears as shown in Patent Document 1 above, in order to obtain a sufficient output (high reduction ratio), a plurality of spur gears are arranged in parallel (three or more stages). Since it must be arranged, there is a problem that the actuator becomes large. In addition, if the gear is downsized to eliminate the increase in size of the actuator, it is difficult to ensure the strength of the gear, resulting in an increase in manufacturing cost. As described above, the conventional configuration using the multi-stage spur gear is not suitable for downsizing the actuator that requires a high reduction ratio.

Therefore, an object of the present invention is to provide an electric parking brake actuator that can obtain a high reduction ratio and can be downsized.

In order to solve the above problems, the present invention includes an electric motor, a speed reduction mechanism, and a linear motion mechanism, and converts the rotational motion of the electric motor decelerated by the speed reduction mechanism into linear motion by the linear motion mechanism. An electric parking brake actuator that presses a brake pad against a brake disc to generate a braking force on a wheel. The first sprocket is arranged coaxially with the electric motor, and is arranged in parallel to the axis of the first sprocket. The second sprocket and a chain that transmits rotational motion between the first sprocket and the second sprocket, and the speed reduction mechanism has an eccentric portion that moves eccentrically by the rotational motion from the electric motor. The present invention is characterized in that it is an eccentric type deceleration mechanism that decelerates and transmits the applied rotational motion.

Thus, by adopting a configuration in which the first sprocket and the second sprocket arranged in parallel with each other are connected by a chain, the actuator can be miniaturized. That is, when power is transmitted between two shafts using only two gears meshing with each other, the gear diameter needs to be increased according to the distance between the two shafts, but in a configuration in which two sprockets are connected by a chain. Since the power can be transmitted using a small-diameter sprocket regardless of the distance between the two axes, the actuator can be miniaturized. Furthermore, by adopting an eccentric speed reduction mechanism as the speed reduction mechanism, it is possible to provide an electric parking brake actuator that is small and can secure a high speed reduction ratio and that is small and that can provide high output.

The deceleration mechanism is preferably arranged on the output side of the power transmission mechanism including the first sprocket, the second sprocket, and a chain (hereinafter sometimes abbreviated as “first sprocket etc.”).

As described above, when the speed reduction mechanism is disposed on the output side of the power transmission mechanism including the first sprocket or the like, the low-torque rotational motion before being decelerated by the speed reduction mechanism is transmitted to each sprocket or chain. It will be. In this case, on the contrary, the load on each sprocket and chain is reduced compared to the case where the speed reduction mechanism is arranged on the input side of the power transmission mechanism including the first sprocket or the like, so that these damages can be suppressed. It becomes like this. Further, with such an arrangement, each sprocket and chain can be made of a resin material.

As the speed reduction mechanism, an input shaft having an eccentric portion, a revolving member that is rotatably held on the outer periphery of the eccentric portion via a rolling bearing, and performs a revolving motion around the rotation shaft as the input shaft rotates. In addition, it is possible to employ a mechanism provided with a motion conversion mechanism that converts the rotational motion generated in the revolving member during the revolving motion into the rotational motion of the output shaft.

Further, as a speed reduction mechanism, an input shaft having an eccentric portion, an external gear having a plurality of teeth provided on the outer peripheral surface as a revolving member, an internal gear having a plurality of teeth provided on the inner peripheral surface, and an output The external gear engages with the internal gear while revolving around the rotation axis of the input shaft as the input shaft rotates, and is provided on the external gear. Adopts a function that functions as a motion conversion mechanism that converts the rotational motion generated in the external gear during revolving motion into the rotational motion of the output shaft by abutting the pin on the inner wall surface of the pin hole provided in the output shaft it can.

According to the present invention, it becomes possible to provide an actuator for an electric parking brake that is small in size and can provide a high output, so that it is easy or possible to mount the actuator in the wheel of an existing vehicle.

It is the figure which looked at the state by which the electric parking brake device was assembled | attached to the vehicle body from the width direction inner side of the wheel. FIG. 2 is a longitudinal sectional view taken along the line AA in FIG. It is a longitudinal cross-sectional view of the electric parking brake apparatus shown in FIG. It is a disassembled perspective view of the electric parking brake apparatus shown in FIG.

FIG. 1 is a view of a state in which the electric parking brake device is assembled to the vehicle body as viewed from the inner side in the width direction of the wheel, and FIG. 2 is a longitudinal sectional view taken along line AA in FIG. 3 is a longitudinal sectional view of the electric parking brake device shown in FIG. 1, and FIG. 4 is an exploded perspective view of the electric parking brake device shown in FIG.

Hereinafter, the configuration of the electric parking brake device according to the embodiment of the present invention will be described with reference to FIGS. In the following description, the inner side in the vehicle body width direction (left side in FIGS. 2 to 4) when the electric parking brake device is assembled to the vehicle body is referred to as the inner side, and the outer side in the vehicle body width direction (FIGS. 2 to 5). 4) will be referred to as the outer side.

As shown in FIGS. 3 and 4, the electric parking brake device 1 includes a brake disc (disc rotor) 2 that rotates together with the wheels, and a pair of brake pads that are disposed on the inner side and the outer side with the brake disc 2 interposed therebetween. 3, 4, a mounting bracket 5 that supports the pair of

brake pads

3, 4, a caliper housing 6 that is slidably supported with respect to the mounting bracket 5, a piston 7 that is accommodated in the caliper housing 6, and a piston The actuator 20 for linearly moving the actuator 7 is mainly configured.

The mounting bracket 5 is fixed with a bolt to a knuckle 60 (see FIGS. 1 and 2) which is a non-rotating portion that supports the wheel. As shown in FIG. 4, the mounting bracket 5 is disposed on the outer side and an inner pad support portion 8 that supports the brake pad 3 disposed on the inner side so as to be movable toward and away from the brake disk 2. An outer pad support portion 9 that supports the brake pad 4 so as to be movable toward and away from the brake disc 2, and a connecting portion 10 that connects the inner pad support portion 8 and the outer pad support portion 9.

The connecting portion 10 is provided at two locations on the inlet side and the outlet side in the rotation direction of the brake disk with respect to the caliper housing 6. Each connecting portion 10 has a pin hole 12 into which a pair of slide pins 11 fixed to the caliper housing 6 are slidably inserted. As each slide pin 11 slides within the pin hole 12, the caliper housing 6 is supported so as to be movable with respect to the mounting bracket 5 via these slide pins 11.

The piston 7 in the caliper housing 6 is accommodated so as to be movable in the direction in which the inner brake pad 3 is pressed against the brake disc 2 and in the opposite direction. When the piston 7 is advanced toward the brake disk 2 by the pressing of the actuator 20, the inner brake pad 3 is pressed against the brake disk 2 by the piston 7. In addition, when the inner brake pad 3 is pressed against the brake disc 2, the caliper housing 6 is moved against the mounting bracket 5 by the reaction force (force in the direction away from the brake disc 2) that the piston 7 receives from the brake disc 2. Move the slide. At this time, the caliper housing 6 pushes the outer brake pad 4 in a direction to approach the brake disc 2 so that the outer brake pad 4 is pressed against the brake disc 2. As described above, the outer brake pad 4 and the inner brake pad 3 are pressed against the brake disc 2, whereby braking force is generated on the brake disc 2.

On the other hand, when releasing the braking force of the brake disc 2, the pressure of the piston 7 by the actuator 20 is released, and the piston 7 can be retracted in the opposite direction (the direction away from the brake disc 2). 2, the pressing force (braking force) of the inner brake pad 3 and the outer brake pad 4 with respect to 2 is released.

Subsequently, the configuration of the actuator 20 will be described.

As shown in FIGS. 3 and 4, the actuator 20 includes an electric motor 21, a speed reduction mechanism 30 that reduces and transmits the rotational motion of the electric motor 21, a linear motion mechanism 40 that converts the rotational motion into a linear motion, Rotating between the first sprocket 22 arranged coaxially with the electric motor 21, the second sprocket 23 arranged parallel to the axis of the first sprocket 22, and the first sprocket 22 and the second sprocket 23 A chain 24 for transmitting motion, an actuator case 50 and the like are provided.

The actuator case 50 includes a first case 51 provided with an electric motor housing portion 51a in which the electric motor 21 is housed, a speed reduction mechanism housing portion 51b in which the speed reduction mechanism 30 is housed, the chain 24, and the

sprockets

22, 23. And the like, and a lid member 53 attached to the electric motor accommodating portion 51a of the first case 51. The electric motor accommodating portion 51 a is formed in a cylindrical shape, and an opening on the outer side is closed by a lid member 53. The speed reduction mechanism housing 51b is formed in a thin cylindrical shape that is shorter in the axial direction than the electric motor housing 51a, and is formed integrally with the electric motor housing 51a. The second case 52 is a lid-like case formed in the same thickness as the speed reduction mechanism accommodating portion 51b, and is fixed to the first case 51 with a bolt or the like so as to close the inner opening. Yes. The actuator case 50 and the caliper housing 6 are fixed with bolts or the like so that the outer opening of the reduction mechanism housing 51b and the inner opening of the caliper housing 6 abut each other.

The first sprocket 22 is attached to the rotating shaft 21a of the electric motor 21 so as to rotate integrally. On the other hand, the second sprocket 23 is attached so as to rotate integrally with the input shaft 31 of the speed reduction mechanism 30 disposed in parallel with the rotating shaft 21 a of the electric motor 21. The chain 24 is stretched over the first sprocket 22 and the second sprocket 23, and when the rotating shaft 21 a of the electric motor 21 rotates, the rotational motion is transferred from the first sprocket 22 through the chain 24 to the second sprocket 23. Is transmitted to. Further, in the present embodiment, the number of teeth of the second sprocket 23 is formed to be larger than the number of teeth of the first sprocket 22, and is transmitted from the first sprocket 22 to the second sprocket 23 via the chain 24. Rotational motion is decelerated.

As the speed reduction mechanism 30, a cycloid speed reduction mechanism that is one of the eccentric speed reduction mechanisms that reduce and transmit the rotational motion applied to the eccentric portion is employed. The speed reduction mechanism 30 is rotatably held on the outer periphery of the eccentric portion 32 via the input shaft 31 having the eccentric portion 32 on the outer periphery and the rolling bearing 36, and the rotation shaft is centered with the rotation of the input shaft 31. An external gear 33 as a revolving member that performs a revolving motion, an internal gear 34 that is arranged so as not to rotate on the outer periphery of the external gear 33, and an output shaft 35 are provided.

The input shaft 31 is rotatably supported by a rolling bearing 13 provided in the actuator case 50 (second case 52). The eccentric portion 32 has an outer peripheral surface (eccentric surface) centered on an axis that is eccentric with respect to the rotation axis of the input shaft 31. On the outer periphery of the eccentric portion 32, an annular external gear 33 having a plurality of teeth provided on the outer peripheral surface via a rolling bearing 36 is provided. An annular internal gear 34 having a plurality of teeth provided on the inner peripheral surface is disposed on the outer periphery of the external gear 33 so that the internal gear 34 does not rotate to the actuator case 50 (first case 51). It is fixed. The internal gear 34 is arranged coaxially with the rotation shaft of the input shaft 31 and has a larger number of teeth than the external gear 33. The output shaft 35 is supported by a rolling bearing 14 provided in the caliper housing 6 so as to be rotatable coaxially with the rotation shaft of the input shaft 31. The output shaft 35 is provided with a plurality of pin holes 35a. A plurality of pins 33a protruding in the axial direction from the external gear 33 are inserted into each pin hole 35a.

When the input shaft 31 rotates and the eccentric portion 32 starts an eccentric motion, the external gear 33 starts a revolving motion around the rotation shaft of the input shaft 31. At this time, a part of the teeth of the external gear 33 are engaged with the teeth of the internal gear 34, so that the external gear 33 revolves while rotating. As the external gear 33 rotates, the pin 33 a provided on the external gear 33 contacts the inner wall surface of the pin hole 35 a of the output shaft 35. Here, since the inner diameter of the pin hole 35a is sufficiently larger than the outer diameter of the pin 33a, the revolution movement of the external gear 33 is not transmitted to the output shaft 35 via the pin 33a, and the external gear 33 Only the rotational motion of is transmitted to the output shaft 35 via the pin 33a. That is, the pin 33 a and the pin hole 35 a function as a motion conversion mechanism that converts the rotation motion generated in the external gear 33 (revolution member) during the rotation motion into the rotation motion of the output shaft 35. Further, the rotation of the external gear 33 occurs when the engagement position of the external gear 33 with respect to the internal gear 34 shifts by one tooth along with the revolution movement when the input shaft 31 rotates once. Therefore, if the number of teeth of the internal gear 34 is z, the external gear 33 only rotates 1 / z of one tooth every time the input shaft 31 rotates, and therefore the output shaft 35 is relative to the input shaft 31. The motor is decelerated at the reduction ratio z and rotates.

The linear motion mechanism 40 is accommodated in the caliper housing 6. In the present embodiment, the linear motion mechanism 40 includes a screw shaft 41 having a thread groove formed on the outer peripheral surface, and a cylindrical nut 42 having a screw groove screwed to the screw shaft 41 on the inner peripheral surface. The slide screw mechanism is used. It is also possible to adopt a ball screw mechanism instead of the sliding screw mechanism.

The screw shaft 41 is arranged coaxially with respect to the output shaft 35 of the speed reduction mechanism 30 and is coupled to be rotatable integrally therewith. Accordingly, when the screw shaft 41 rotates with the rotation of the output shaft 35 of the speed reduction mechanism 30, the nut 42 moves forward or backward in the axial direction. When the nut 42 moves forward, the inner brake pad 3 is pressed against the brake disc 2 by pressing the piston 7 by the nut 42. At this time, the brake pad 4 on the outer side is also pressed against the brake disc 2 by the above-described action, so that a braking force is generated on the brake disc 2. On the contrary, when the nut 42 moves backward, the piston 7 moves away from the brake disc 2, so that the braking force by the inner brake pad 3 and the outer brake pad 4 on the brake disc 2 is released.

The configuration and operation of the actuator 20 according to the present embodiment are as described above. Hereinafter, regarding the actuator 20 according to the present embodiment, components suitable for miniaturization while ensuring a high reduction ratio will be described.

In the actuator 20 according to the present embodiment, as shown in FIG. 3, the speed reduction mechanism 30 and the linear motion mechanism 40 are arranged in parallel to the electric motor 21, compared to a configuration in which these are arranged coaxially. The size of the entire actuator 20 in the axial direction is reduced. Thereby, as shown in FIG. 2, the protrusion amount of the actuator 20 from the wheel 61 to the inner side is suppressed, and space saving is achieved. However, in such a configuration, power transmission means between two parallel axes from the electric motor 21 to the speed reduction mechanism 30 is required.

Here, as a power transmission means between two parallel shafts, for example, if a configuration consisting of only two gears meshing with each other is adopted, the diameter of the gears must be increased according to the distance between the two shafts. It is not preferable from the viewpoint of downsizing. On the other hand, as in this embodiment, the two

sprockets

22 and 23 and the chain 24 are used as power transmission means, and the

sprockets

22 and 23 are connected by the chain 24 so that the small-

diameter sprockets

22 and 23 are connected. Even if it is used, power transmission between two parallel axes becomes possible. As a result, the actuator can be further reduced in size, and it becomes easier to mount the actuator in the wheel of an existing vehicle while avoiding interference with peripheral members arranged on the wheel inner side.

As described above, in the actuator according to the present embodiment, the two

sprockets

22 and 23 and the chain 24 connecting them are used as power transmission means between two parallel shafts, so that the actuator can be downsized. . However, it is generally difficult to obtain a large reduction ratio only by the speed reduction means based on the difference in the number of teeth between the

sprockets

22 and 23. Furthermore, from the viewpoint of miniaturization, it is difficult to employ two sprockets having a large difference in the number of teeth. Therefore, it is not expected to secure a large reduction ratio between the sprockets.

Therefore, in the actuator according to the present embodiment, a cycloid reduction mechanism that can obtain a high reduction ratio is used as a separate reduction mechanism in order to compensate for a situation where it is difficult to ensure a high reduction ratio between the

sprockets

22 and 23. . As described above, in the cycloid reduction mechanism, the number corresponding to the number of teeth z of the internal gear 34 can be secured as the reduction ratio. For example, when the internal gear 34 having 60 teeth is employed, The reduction ratio is 60, and a high reduction ratio can be ensured while being small.

As described above, the actuator according to the present embodiment employs a mechanism composed of two sprockets and a chain as power transmission means between two parallel axes, and further adopts a cycloid reduction mechanism as a reduction mechanism. The actuator can be downsized and high output can be secured. As a result, it is possible to provide an electric parking brake actuator that is small in size and can provide a high output, and it is easy or possible to mount the actuator in the wheel of an existing vehicle.

The actuator for an electric parking brake according to the present invention is not limited to the above-described embodiment, and can of course be implemented in various forms without departing from the gist of the present invention. .

In the above-described embodiment, a mechanism that rotates by the revolving external gear 33 engaging the internal gear 34 is employed as the eccentric reduction mechanism. A mechanism that provides a curved plate (revolving member) provided with a plurality of curves consisting of trochoidal curves, and rotates by engaging the curved pins of the revolving curved plate with a plurality of pins fixed at equal intervals in the circumferential direction. There may be. Further, instead of the external gear 33, it is also possible to employ a roller type eccentric speed reduction mechanism including a cage that holds a plurality of rollers provided at equal intervals in the circumferential direction.

In the above-described embodiment, the speed reduction mechanism 30 is disposed on the output side (downstream of the power transmission path) than the power transmission mechanism including the first sprocket 22, the second sprocket 23, and the chain 24. In addition, the speed reduction mechanism 30 can be disposed on the input side (upstream side of the power transmission path) of the power transmission mechanism including the first sprocket 22 and the like. However, when the speed reduction mechanism 30 is disposed on the input side of the power transmission mechanism including the first sprocket 22 and the like, the high torque driving force decelerated by the speed reduction mechanism 30 is transmitted to the

sprockets

22, 23 and the chain 24. Therefore, the load on these becomes large. Therefore, from the viewpoint of reducing the load on each of the

sprockets

22 and 23 and the chain 24, the speed reduction mechanism 30 can be disposed on the output side of the power transmission mechanism including the first sprocket 22 and the like as in the above-described embodiment. preferable. Also, with such an arrangement, the load on each of the

sprockets

22, 23 and the chain 24 is reduced and the possibility of breakage is also reduced. Therefore, the

sprockets

22, 23 and the chain 24 are made of resin material {eg, polyacetal ( POM), nylon (PA66, etc.), polybutylene terephthalate (PBT)}.

The actuator for an electric parking brake according to the present invention is not limited to an electric parking brake device mounted on a vehicle such as an automobile, but can also be applied to an electric parking brake device for a motorcycle.

DESCRIPTION OF SYMBOLS 1 Electric parking brake apparatus 2 Brake disk 3 Inner side brake pad 4 Outer side brake pad 20 Actuator 21 Electric motor 22 First sprocket 23 Second sprocket 24 Chain 30 Deceleration mechanism 31 Input shaft 32 Eccentric part 33 External gear (revolution member)
33a pin (motion conversion mechanism)
34 Internal gear 35 Output shaft 35a Pin hole (motion conversion mechanism)
36 Rolling bearing 40 Linear motion mechanism 41 Screw shaft 42 Nut 50 Actuator case

Claims

An electric motor, a speed reduction mechanism, and a linear motion mechanism are provided, and the rotational movement of the electric motor decelerated by the speed reduction mechanism is converted into a linear motion by the linear motion mechanism so that the brake pad is pressed against the brake disc. An electric parking brake actuator for generating braking force on a wheel,
A first sprocket disposed coaxially with the electric motor, a second sprocket disposed parallel to the axis of the first sprocket, and a rotational motion between the first sprocket and the second sprocket. With a chain to transmit,
An electric parking system characterized in that the deceleration mechanism has an eccentric part that eccentrically moves by rotational movement from the electric motor, and is an eccentric type deceleration mechanism that decelerates and transmits the rotational movement applied to the eccentric part. Brake actuator.
2. The electric parking brake actuator according to claim 1, wherein the speed reduction mechanism is disposed on an output side of a power transmission mechanism including the first sprocket, the second sprocket, and the chain.
The electric parking brake actuator according to claim 2, wherein the first sprocket, the second sprocket, and the chain are made of a resin material.
The speed reduction mechanism is rotatably held on an outer periphery of the eccentric portion via an input shaft having a eccentric portion and a rolling bearing, and performs a revolving motion around the rotation shaft as the input shaft rotates. The actuator for an electric parking brake according to any one of claims 1 to 3, further comprising: a member and a motion conversion mechanism that converts a rotational motion generated in the revolving member during the revolving motion into a rotational motion of an output shaft.
The speed reduction mechanism includes an input shaft having an eccentric portion, an external gear provided with a plurality of teeth on the outer peripheral surface as the revolving member, an internal gear provided with a plurality of teeth on the inner peripheral surface, and an output With a shaft,
Along with the rotation of the input shaft, the external gear engages with the internal gear while revolving around the rotation shaft of the input shaft to rotate, and is provided on the external gear. When the pin is in contact with the inner wall surface of the pin hole provided in the output shaft, it functions as a motion conversion mechanism that converts the rotational motion generated in the external gear during the revolving motion into the rotational motion of the output shaft. The actuator for electric parking brakes according to claim 4.