JP2002213504A - Electric brake device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive electric brake device capable of extending the rated fatigue life of a ball and enhancing reliability without requiring any substantial improvement and using any special lubricant in a ball screw mechanism. SOLUTION: In the electric brake device equipped with an electric actuator to drive the brake pad of a disc brake or to drive the brake shoe of a drum brake, the electric actuator 5 is provided with a ball screw mechanism 7 composed of a screw shaft 14 to convert the rotational movement of an electric motor 6 to linear movement, a ball 15 and a nut 12, and an elastic member 20 of synthetic rubber for instance is interposed between the screw shaft end part of the ball screw mechanism and the brake pad or the brake shoe.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brake device used for a vehicle or an industrial machine, for example, and relates to an electric brake device provided with an electric actuator for driving a brake pad of a disc brake or a brake shoe of a drum brake.

[0002]

2. Description of the Related Art From the viewpoint of so-called energy saving and environmental consideration, an internal combustion engine such as a vehicle, particularly an automobile, has been equipped with an internal combustion engine called a hybrid vehicle and an electric motor, instead of those that have consumed oil as fuel. There is a tendency to shift to so-called EV vehicles, which can be properly used according to driving conditions, or use only an electric motor as a drive source.

[0003] Brake devices used in vehicles and the like are broadly classified into disc brakes and drum brakes.
For the drive of the brake pads in the disc brake and the drive of the brake shoes in the drum brake, an electric brake device provided with an electric actuator tends to be devised instead of the conventional hydraulic type.

For example, Japanese Patent Application Laid-Open No. Hei 8-284980 discloses the technology of an electric disk brake device, and Japanese Patent Application Laid-Open No. 11-99934 discloses the technology of an electric disk brake device and an electric drum brake device. ing.

In any of the brake devices, a rotating body having a friction surface and rotating with the wheel, a rotating member having a friction material pressed against the friction surface of the rotating body to brake the rotation of the rotating body, and a brake pedal The electric motor is driven by electric power based on an operation of an operation member such as an electric motor, and a force transmitting member for transmitting a driving force of the electric motor to the rotating member.

For example, in an electric disk brake device, a brake pad (rotating member) to which a pad (friction material) is adhered is used as a force transmitting member for pressing a disk rotor (rotating member) to linearly rotate the electric motor rotating shaft. A ball screw mechanism that converts to motion is used.

In this ball screw mechanism, transmission and amplification can be performed with high efficiency without losing the output of the electric motor, a large braking force can be obtained, and driving with a small output electric motor is possible. The overall size can be reduced.

[0008]

The gap between the brake pad and the rotor in the case of the disc brake device and the gap between the brake shoe and the drum in the case of the drum brake device are all very small. Should be set to.

[0009] Accordingly, one of the characteristics is that the relative displacement between the screw shaft connected to the rotary shaft of the electric motor and the nut screwed to the screw shaft in the ball screw mechanism is extremely small. Has become one.

On the other hand, in a ball screw mechanism, special ball screw specifications are often required in order to make the actuator itself as small as possible. As one of them, a small lead (small pitch) ball screw mechanism is configured to extract a large braking force while reducing the motor output by reducing the size of the electric motor.

According to the small lead ball screw mechanism, the diameter of the ball becomes extremely small, and a large surface pressure is generated on the ball. Also, an extremely large number of balls must be inserted and filled in the ball circulation path formed between the nut and the screw shaft.

When the ball screw mechanism having such specifications is used under the condition of the above-mentioned slight relative displacement between the screw shaft and the nut, the ball in the ball circulation path can be operated even during the braking operation. Movement amount is small.

Therefore, the change in the contact position of the ball with the screw shaft and the nut is negligible, the grease as a lubricant is not efficiently stirred, and uneven wear tends to occur on a specific ball, and the rated fatigue life is shortened. It will be short.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a ball screw mechanism used as a force transmission mechanism, which does not require a significant improvement and requires a special lubricant. It is an object of the present invention to provide an inexpensive, electrically-operated brake device that can increase the rated fatigue life of a ball without using it, and that can improve reliability.

[0015]

In order to satisfy the above object, an electric brake apparatus according to the first aspect of the present invention comprises an electric actuator having an electric actuator for driving a brake pad of a disk brake or driving a brake shoe of a drum brake. In the brake device, the electric actuator includes a screw shaft that converts a rotational motion of the electric motor into a linear motion, a ball screw mechanism including a ball and a nut, and a screw shaft end of the ball screw mechanism and the brake pad or the brake shoe. And an elastic member interposed therebetween.

By adopting the means for solving the above problems, the ball screw mechanism used as the force transmission mechanism does not require a significant improvement and does not use a special lubricant, and can reduce the rated fatigue life of the ball. It is possible to prolong the time and to improve reliability at low cost.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. FIGS. 1 to 3 are schematic cross-sectional views of an electric disc brake device mounted on, for example, an automobile, showing different states.

In FIG. 1, reference numeral 1 denotes a caliper housing in which an inner pad 2 and an outer pad 3 are accommodated. The inner pad 2 and the outer pad 3 are provided to face a disk rotor 4 that rotates together with wheels (not shown). The inner pad 2 held by a suitable means is located on the inner side of the vehicle, and the caliper housing 1 is provided.
The outer pad 3 is attached and fixed to the inner surface side.

An electric actuator 5 is arranged adjacent to the caliper housing 1. The electric actuator 5 includes an electric motor 6 and a ball screw mechanism 7 driven by the electric motor 6.

The electric motor 6 has a motor cover 8 connected to the caliper housing 1 via a caliper housing moving mechanism (not shown), and a stator 9 is fitted and fixed to the inner peripheral surface of the motor cover 8. Is done.

Bearings 10, 10 are provided on the inner peripheral portion of the motor cover 8 at predetermined intervals from both end surfaces of the stator 9, and the nuts constituting the ball screw mechanism 7 are rotatably supported by the bearings 10. Is done.

As shown in FIG. 4, a part of the peripheral surface of the nut 11 at a predetermined interval is cut into a flat shape, and a circulating member 12 called a top is attached. In this circulating member 12, a tube may be used instead of a top.

In any case, the flat portion of the nut 11 is provided with a pair of through holes communicating with the screw grooves provided on the inner peripheral surface of the nut, and these through holes are provided in the ball guide grooves 13 provided in the circulation member 12. To both ends of the

A screw shaft 14 having a thread groove formed on the outer peripheral surface is inserted into the thread groove of the nut 11.
And the screw shaft 14 are combined via a ball 15. The ball 15 is filled from the ball guide groove 13 of the circulation member 12 into a thread groove facing the through hole through a pair of through holes provided in the nut 11.

Therefore, when the nut 11 and the screw shaft 14 rotate more than a predetermined number of rotations and are relatively displaced, the ball 15 coming out of one of the through holes rolls along the thread groove of the nut 11 and the screw shaft 14. Then, it is guided out of the other through-hole into the ball guide groove 13 of the circulation member 12, and circulates along the ball circulation path to return to the one through-hole.

A rotor 16 constituting the electric motor 6 is fitted on the outer peripheral surface of the nut 11 and is integrally fixed to each other. The rotor 16 is located at a position facing the stator 9 fitted on the inner peripheral surface of the motor cover 8, and is attached with a narrow gap between the peripheral surfaces.

An elastic member 20, which will be described later, is attached to one end surface of the screw shaft 14, and the elastic member 20 is in contact with the inner pad 2. The other end surface of the screw shaft 14 is provided with a pivot hole 17.
A pivot pin 18 attached to the closed surface of the motor cover 8 is inserted into the motor cover 8. Therefore, the nut 11 and the screw shaft 1
4 is rotatably supported by a pair of bearings 10 and a pivot pin 18.

The elastic member 20 has a certain degree of rigidity, for example, a synthetic rubber material, and also has elasticity with a predetermined spring constant. When it receives a compressive force of a predetermined amount or more, it temporarily contracts and deforms. After that, an elastic repulsive force acts and attempts to return to the original state.

In the electric disk brake device constructed as described above, the electric motor 6 does not operate in a state where the brake operation is not performed. Therefore, as shown in FIG. As is the case, a gap is formed between the inner pad 2 and the outer pad 3 and the disk rotor 4, and the disk rotor 4 is freely restrained and freely rotates with the wheel.

When a brake pedal (not shown) is depressed, the electric motor 6 is energized. When a predetermined voltage is applied to the electric motor 6, the stator 9 is excited and the rotor 16 is driven to rotate.

The nut 12 integral with the rotor 16 is rotated, and the torque of the nut 12 is transmitted to the screw shaft 14 via the ball 15. Accordingly, the screw shaft 14 is displaced along the axial direction, here, leftward in the figure.

Depending on the selection conditions of the spring constant of the elastic member 20 with respect to the weight of the inner pad 2, the displacement of the screw shaft 14 does not appear as the displacement of the elastic member 20 as it is.

For example, as shown by a solid line in FIG. 2, the displacement of the screw shaft 14 is absorbed by the elastic member 20 and is compressed and deformed, thereby reducing the thickness of itself. After such a one-cushion is placed, as shown by the two-dot chain line in FIG.
An elastic repulsive force acts on the wall to return to the original thickness.

The inner pads 2 are pressed by the elastic member 20 and come into contact with the disk rotor 4 to be in sliding contact with each other. The screw shaft 14 receives the elastic repulsive force of the elastic member 20 and the rotation speed decreases, and the rate of change of the movement amount decreases.

On the other hand, the caliper housing 1 is displaced rightward in the figure from the motor cover 8 via the caliper housing moving mechanism, and the outer pad 3 attached here is displaced.
Presses against the disk rotor 4.

As shown in FIG. 3, when the electric motor 6 is stopped in a timely manner and the screw shaft 14 stops moving, an elastic repulsive force corresponding to the spring constant of the elastic member 20 is applied to the inner pad 2. Works.

Accordingly, the inner pad 2 comes into pressure contact with the disk rotor 4 to generate a frictional force between the outer pad 3 and the left and right surfaces of the disk rotor 4. A braking torque is generated for the disk rotor 4, and the rotation of wheels integral with the disk rotor 4 is restricted, and the brake operation is performed.

That is, when the brake pedal is depressed as necessary, the inner pad 2 and the outer pad 3 are moved from the state of FIG. 1 to the state of FIG. 2 as shown in FIG.
Thus, the disk rotor 4 is pressed against the disk rotor 4 to obtain a braking force.

At this time, the elastic repulsive force of the elastic member 20 acts not only on the inner pad 2 but also on the screw shaft 14 which has stopped rotating, and urges the screw shaft 14 in the opposite direction. The screw shaft 14 stops rotating after moving to some extent in the opposite direction.

Originally, in the braking operation of depressing the foot brake pedal, the amount of displacement of the inner pad 2 is extremely small, so that the amount of rotation of the screw shaft 14 is very small, and the amount of rotation of the ball 15 constituting the ball screw mechanism 7 is small. Positional fluctuations in the ball circuit are negligible.

However, since the elastic member 20 is interposed between the screw shaft 14 constituting the ball screw mechanism 7 and the inner pad 2, even if the inner pad 2 contacts the disk rotor 4, the screw shaft is still The elastic member 20 is compressed and deformed by rotating the screw shaft 14 in a predetermined direction and continuing the movement of the screw shaft 14.

Thereafter, when the electric motor 6 is stopped in a timely manner, the inner pad 2 presses the disk rotor 4 by the action of the elastic member 20 and rotates the screw shaft 14 in the opposite direction.

As described above, the amount of rotation of the screw shaft 14 is extremely large as compared with the amount of displacement of the inner pad 2.
Ball 1 in ball circulation path with rotation of screw shaft 14
The movement amount of No. 5 becomes large.

In addition, since the screw shaft 14 is rotated not only in the predetermined direction but also in the opposite direction, the position of the ball 15 in the ball circulation path fluctuates greatly every braking operation. For this reason, even if the ball 15 reenters the load receiving area sandwiched between the screw shaft 14 and the nut 11, the ball 15 always contacts the load receiving area on an unspecified surface.

Eventually, uneven wear of the ball 15 can be prevented, and agitation of the lubricant (grease) can be promoted. As a result, the rated fatigue life of the ball 15 can be extended and reliability can be improved.

FIG. 5 shows an electric disk brake device, in which the same components as those described above are denoted by the same reference numerals, and a new description will be omitted. Here, a disc spring 20A is used as an elastic member interposed between the screw shaft 14 constituting the ball screw mechanism 7 and the inner pad 2. The disc spring 20A is supported by a cap holder 21.
Receives the elastic force of the disc spring 20A and presses the inner pad 2.

By using the disc spring 20A, the screw shaft 14 at the time of the braking operation is in exactly the same state as described above. Therefore, even if the ball 15 reenters the load receiving area sandwiched between the screw shaft 14 and the nut 11, the ball 15 always contacts the load receiving area on an unspecified surface.

As a result, uneven wear of the ball 15 can be prevented, and agitation of the lubricant (grease) can be promoted. As a result, the rated fatigue life of the ball 15 can be extended and reliability can be improved.

The above description has been made by applying, for example, the synthetic rubber material 20 or the disc spring 20A as the elastic member. However, the present invention is not limited to this, and another type of elastic member may be interposed at a predetermined portion. The same operation and effect can be obtained.

Although the above embodiment has been described as an electric disc brake device, the present invention is not limited to this, and may be applied to a ball screw mechanism in an electric drum brake device.

That is, a friction material is adhered to the inner peripheral surface of the drum that rotates together with the wheels, and a pair of brake shoes with the friction material adhered to the inner peripheral surface of the drum are rotatably supported. When the brake pedal is depressed, the electric motor is driven, and the ball screw mechanism connected thereto is actuated to pull and urge the brake cable.

The brake shoe is connected to the brake cable, the brake shoe is rotated with the anchor as a fulcrum, and the friction material adhered thereto slides on the friction material of the drum to reduce the braking torque on the drum. Give.

As described above, the relative displacement (stroke) between the screw shaft and the nut is increased at a predetermined timing during the non-braking operation without changing the specifications required for the ball screw mechanism and the system of the entire brake device. Take.

However, also in this electric drum brake device, it is desirable as a brake characteristic that the gap between the brake shoe and the drum is small. Therefore, the screw shaft and the nut in the ball screw mechanism are kept in a positional relationship of a slight relative displacement (stroke).

By depressing the brake pedal,
The screw shaft is displaced in a direction in which the brake shoe contacts the drum. The amount of displacement of the screw shaft is the amount by which the ball filled in the ball circulation path circulates through the circulation path at least once. Therefore, even when the ball reenters the load receiving area sandwiched between the screw shaft and the nut, the ball always contacts the load receiving area on an unspecified surface.

This prevents uneven wear of the ball and promotes agitation of the lubricant (grease).
As a result, the rated fatigue life of the ball is extended, and the reliability is improved.

Although the above-described electric brake device has been described as a disc brake or a drum brake for an automobile, the present invention is not limited to this. For example, a brake device in a device as a so-called industrial machine, such as a conveyor, may be used. Can be used.

[0058]

As described above, according to the present invention, the ball screw mechanism used as the force transmission mechanism does not require a significant improvement, does not use a special lubricant, and has a rated fatigue life of the ball. The effect of the present invention is that it is possible to prolong the length of the device, to obtain an inexpensive and improved reliability.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an embodiment of the present invention in a non-braking operation state of an electric disc brake device.

FIG. 2 is a schematic cross-sectional view showing the same embodiment in a brake operating state of the electric disk brake device.

FIG. 3 is a schematic cross-sectional view showing the embodiment, in a state different from FIG. 2;

FIG. 4 is an enlarged sectional view of a part of the ball screw mechanism of the embodiment.

FIG. 5 is a schematic cross-sectional view of another embodiment of the electric disc brake device in a non-braking operation state.

[Explanation of symbols]

 5: Electric actuator, 6: Electric motor, 14: Screw shaft, 15: Ball, 14: Nut, 7: Ball screw mechanism. 20 ... elastic member.

Claims (1)

[Claims] 1. An electric brake device comprising an electric actuator for driving a brake pad of a disc brake or driving a brake shoe of a drum brake, wherein the electric actuator converts a rotary motion of the electric motor into a linear motion. And a ball screw mechanism comprising a ball and a nut, wherein an elastic member is interposed between a screw shaft end of the ball screw mechanism and the brake pad or the brake shoe.