JP4335375B2 - Actuator for motor-driven drum brake - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an actuator for a motor-driven drum brake formed at low cost with easy structure capable of performing easy assembly, being compact with requiring small mounting space, and allowing to perform parking brake. SOLUTION: A rotating slide member 32 provided so as to be movable in an axial direction and rotatable around an axial center is rotated with accompanied by rotation of an electric motor for braking through a worm gear pair 50, resulting in respective movement of a pair of projecting members 38, 40 in a projecting direction from the rotating slide member 32 through a pair of screw mechanisms 34, 36 having contrary twists to each other, and a pair of brake shoes 16, 18 are opened to be pressed against a brake drum 24. Since power is transmitted from the electric motor to the rotating slide member 32 through the worm gear pair 50, power transmission in the reverse direction is prevented and a braking condition can be maintained only by stopping operation of the electric motor.

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a motor-driven drum brake, and more particularly to an actuator that expands a pair of brake shoes based on braking rotation of an electric motor.
[0002]
[Prior art]
A motor-driven drum brake that spreads a pair of brake shoes to both sides by an electric motor and presses against a brake drum that rotates with a wheel to generate a braking force is known as a brake for vehicles such as automobiles and trains. The device described in Japanese Examined Patent Publication No. 6-100239 is an example, and by rotating the screw shaft by an electric motor and moving the nut member linearly, the lever connected to the nut member is rotated, A pair of brake shoes engaged with the lever are separated from each other and pressed against the brake drum. Further, when the electric motor is stopped, the electric motor is reversely rotated by the urging force of the return spring to release the brake, and at the time of parking brake, the brake maintaining device having the parking brake actuator is used to prevent reverse rotation of the electric motor. It has become.
[0003]
[Problems to be solved by the invention]
However, since such a conventional motor-driven drum brake operates the brake by converting the linear movement of the nut member into the rotation of the lever, the structure is complicated, the number of parts is large, and a large installation space is required. In addition, it is necessary to assemble the screw shaft and lever separately to the backing plate, resulting in an increase in manufacturing cost. Further, during parking brake, the brake maintenance device having a parking brake actuator prevents reverse rotation of the electric motor, so that the above problem is further conspicuous, such as a complicated structure and a large number of parts. Become.
[0004]
The present invention has been made against the background of the above circumstances. The object of the present invention is to provide a motor-driven drum capable of parking brake, which is simple and inexpensive in construction and has a small mounting space. It is to provide an actuator for a brake.
[0005]
[Means for Solving the Problems]
In order to achieve this object, the first invention is a leading / trailing motor drive in which a pair of brake shoes are expanded to both sides by an electric motor and pressed against a brake drum that rotates together with wheels to generate a braking force. In the drum brake, an actuator for expanding the pair of brake shoes based on the rotation of the electric motor for braking, (a) the axis is aligned with a straight line in the direction of expanding the pair of brake shoes A rotating slide member that is arranged to be movable in the straight line direction in a posture that coincides with the straight line, and is rotated around the straight line as the electric motor rotates, and (b) the straight line of the rotating slide member at both ends of the direction is fitted relatively rotatably around its straight, the with the rotary slide member Together is interposed between the pair of brake shoes, a pair of protruding members which rotation of the straight surrounding is prevented, the line around with rotation for (c) the rotary slide member of the electric motor brake by being rotated, it causes symmetrically relative movement by the action of the screw associated with the relative rotation between the pair of projecting members in the direction projecting the pair of projecting members from the rotary slide member, the reverse rotation of the electric motor Accordingly, the twists provided at the fitting portions of the pair of projecting members and the rotating slide member are opposite to each other and the leads and the radial dimensions are equal so that the pair of projecting members are symmetrically moved relative to each other in the pulling direction. A pair of screw mechanisms; (d) on the outer peripheral surface of the rotary slide member, and capable of relative movement in the axial direction via a locking key or a spline and around the axis A worm wheel disposed so as not to rotate relative to the worm wheel and a worm that is meshed with the worm wheel and attached to the motor shaft of the electric motor. The rotation of the electric motor is decelerated and transmitted to the rotating slide member. In addition, when the electric motor is stopped, the rotating slide member is prevented from rotating backward, while the worm wheel is prevented from moving in the axial direction, and the worm wheel is engaged with the worm regardless of the axial movement of the rotating slide member. And a worm gear that maintains the above.
[0006]
The second invention provides a motor driving the drum actuator brake of the first invention, before Symbol electric motor, on the back side of the backing plate in a posture that the rotation axis is substantially perpendicular to the backing plate of the motor driving the drum brakes It is arranged, and the tip of the motor shaft protrudes to the front side of the backing plate, and the worm is attached .
[0007]
3rd invention is the actuator for motor drive drum brakes of 1st invention or 2nd invention , (a) The said rotation slide member is hold | maintained at the holding | maintenance case so that the movement to an axial direction and the rotation of an axial center are possible. In addition, the pair of protruding members screwed to both ends of the rotating slide member protrude from the opening formed in the holding case to both sides, respectively, and the rotating slide member and the protruding member are held by the holding member. through the case and adapted to be assembled to the backing plate of the motor driving the drum brake, (b) the worm wheel, wherein the axial movement is prevented by the holding case.
[0008]
According to a fourth aspect of the present invention, in the motor-driven drum brake actuator according to any one of the first to third aspects of the present invention, the motor shaft of the electric motor is provided with a tool locking portion having an irregular cross section.
[0009]
【The invention's effect】
In the motor driving the drum actuator brake of the first invention, when the rotary slide member in accordance with the rotation brake of the electric motor is driven to rotate, the pair of projecting members disposed at both ends of the rotary slide member A brake force is generated by protruding from the rotary slide member by the action of the screw of the screw mechanism, and the pair of brake shoes are expanded and pressed against the brake drum. In this case, since the rotary slide member is arranged so as to be movable in a straight line direction, the pair of brake shoes are reliably pressed against the brake drum regardless of dimensional errors or wear, and the rotary slide member is held. There is no fear that an excessive force is generated in the holding case or the like, which is suitable for a leading / trailing drum brake . In particular, a pair of screw mechanisms with opposite leads and equal diameters and diameters are provided at both ends of the rotating slide member, and the pair of projecting members protrude symmetrically. In this case, movement of the rotating slide member in the axial direction (straight line direction) for each brake is reduced, and the operation is stabilized and the durability is improved.
[0010]
In addition, it has a worm gear that decelerates and transmits the rotation of the electric motor to the rotating slide member and prevents reverse rotation of the rotating slide member when the electric motor is stopped, so that the brake state is maintained even when the electric motor is stopped. Can be used as a parking brake without providing a brake maintaining device that prevents reverse rotation, and when the brake is released, the electric motor can be reversely rotated to retract the protruding member into the rotating slide member.
[0011]
Thus, by the present invention are rotary slide member is driven to rotate, a pair of projecting members fitted at both ends protrudes from the rotating slide member, so as to spread apart the pair of brake shoes In addition, since the reverse rotation of the electric motor is prevented by the action of the worm gear and it can be used as a parking brake, the motor-driven drum brake actuator capable of parking braking is simple in structure and constructed at low cost as a whole. At the same time, it is compact and requires a small installation space, thus increasing the degree of design freedom.
[0012]
In addition, it can be used in place of the hydraulic wheel cylinder because it has the same effect as a conventional hydraulic wheel cylinder that expands a pair of brake shoes by projecting a pair of pistons to both sides by hydraulic pressure. It is possible to Furthermore, it is possible to reduce the load of the return spring, as compared with the case where the brake is released by reversely rotating the rotary slide member with the return spring when the electric motor is stopped, thereby reducing the output of the electric motor. In addition, there is no restriction on the screw lead of the screw mechanism between the rotating slide member and the protruding member.
[0013]
In the second invention, the electric motor is disposed on the back side of the backing plate in a posture substantially perpendicular to the backing plate, and the worm of the worm gear is attached to the tip of the motor shaft protruding to the front side of the backing plate. Since the rotary slide member is engaged with a worm wheel disposed so as to be relatively movable in the axial direction and not to be rotatable around the shaft center, the device is configured more compactly.
[0014]
In the third aspect of the invention, the rotating slide member and the pair of projecting members are held by the holding case and are assembled to the backing plate via the holding case, so that handling and assembling work are further facilitated.
[0015]
In the fourth invention, since the tool locking portion is provided on the motor shaft of the electric motor, the brake can be released by manually rotating the motor shaft at the time of failure.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Motor driving the drum actuator brake of the present invention is suitably applied to leading trailing type drum brake, it may be used in place of conventional hydraulic wheel cylinder. The present invention is preferably applied to a brake device having both functions of a service brake and a parking brake, or a brake device for a parking brake, but does not exclude application to a brake device for a service brake. .
[0017]
The screw mechanism is constituted by, for example, a screw hole (female screw) provided in the shaft center of the rotating slide member and a screw shaft (male screw) provided upright on the protruding member. The protruding member is provided with a male screw on the rotating slide member. You may make it provide a female screw in. The projecting member is prevented from rotating around a straight line, for example, by engagement with a brake shoe, but may be prevented from rotating around a straight line by engaging with another member such as a holding case or a backing plate. good.
[0020]
In the third invention, the rotating slide member and the pair of projecting members are arranged in the holding case. However, they can be directly assembled to the backing plate of the drum brake. In the holding case of the third invention, an opening is provided and the protruding member protrudes. If this opening is sized so that the rotating slide member can pass through, the assembly and replacement of the rotating slide member can be performed. It can be done easily and quickly.
[0021]
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is an example of a case where the present invention is applied to a leading / trailing motor-driven drum brake 10, and is a front view showing an essential part thereof, that is, an upper end portion where an actuator 12 is assembled. FIG. 2 is a view corresponding to a II-II cross section in FIG. 1. The motor-driven drum brake 10 includes a backing plate 14 fixed to a vehicle body, a pair of brake shoes 16 and 18 disposed substantially symmetrically on the backing plate 14, and a pair of brake shoes 16 and 18. Between the upper end portions, the actuator 12 is fixedly positioned on the backing plate 14, between the lower ends of the pair of brake shoes 16, 18, an anchor (not shown) is fixedly positioned on the backing plate 14, and a pair of brakes. A return spring 20 that is disposed across the shoes 16 and 18 and urges them toward each other and a strut 22 that defines an approach position of the pair of brake shoes 16 and 18 are provided. The pair of brake shoes 16 and 18 are always held in an approach position (non-brake state) in contact with the strut 22 as shown in FIG. 1 according to the urging force of the return spring 20. When the upper end portions of 16 and 18 are expanded to the left and right sides, the brake drum 24 disposed on the wheel side is pressed to generate a braking force.
[0022]
The actuator 12 includes a cylindrical rotary slide member 32 held in a holding case 30 through a pair of bearings, splines, and the like so as to be movable in the axial direction and rotatable around an axis, and the rotary slide member 32. A pair of projecting members 38 and 40 that are screwed so as to be relatively rotatable about the same axis via screw mechanisms 34 and 36 are provided at both ends, and the holding case 30 has a pair of axial centers of the rotary slide member 32. 1 in a posture (substantially parallel to the backing plate 14) that coincides with a straight line direction (the left-right direction in FIG. 1), which is the expanding direction of the brake shoes 16, 18, on the backing plate 14 by fixing means such as welding, caulking, or rivets. It is fixed integrally. The screw mechanisms 34 and 36 are formed by screw holes (female screws) 32R and 32L provided on the shaft center of the rotary slide member 32, and screw shafts (male screws) 38s and 40s provided integrally with the projecting members 38 and 40, respectively. The screw mechanisms of these screw mechanisms 34 and 36 are opposite to each other, that is, one is a right-hand screw and the other is a left-hand screw, and other specifications such as lead and diameter are the same. When the member 32 is rotated relative to the member 32 in the same direction, it is protruded or drawn from the rotating slide member 32 symmetrically.
[0023]
The pair of projecting members 38 and 40 project outward from openings provided on the left and right sides of the holding case 30, respectively, and notch grooves 38 a and 40 a formed in the head portions 38 h and 40 h include brake shoes 16 and 18. By engaging with the shoe web, the rotation around the axis is prevented, and the dust boots 42, 44 are provided between the heads 38h, 40h of the projecting members 38, 40 and the holding case 30. Is dustproof. The opening of both ends of the holding case 30 is smaller in diameter than the rotary slide member 32, but the hold case 30 is composed of a plurality of members so that a bearing, the rotary slide member 32, etc. can be assembled therein. Yes. In FIG. 2, the holding case 30 is omitted.
[0024]
The rotary slide member 32 is rotationally driven by the electric motor 48 via the worm gear 50 in both forward and reverse directions around the straight line. As apparent from FIG. 2, the electric motor 48 is integrally fixed to the back side of the backing plate 14 in a posture in which the rotational axis is substantially perpendicular to the backing plate 14, and the tip of the motor shaft 48s is While projecting to the front side of the backing plate 14, a tool locking portion 52 having an irregular cross section (rectangular or square in the embodiment) is integrally provided at the rear end of the motor shaft 48s so as to project rearward from the motor body. Yes.
[0025]
The worm gear 50 is a worm 54 that is integrally fixed to the tip of the motor shaft 48s, and is relatively movable in the axial direction on the outer peripheral surface of the rotary slide member 32 via a rotation key 56, and is relative to the periphery of the shaft center. The worm wheel 58 is disposed so as to be non-rotatable and meshed with the worm 54. The rotation of the electric motor 48 is decelerated and transmitted to the rotary slide member 32. When the electric motor 48 is stopped, the return is performed. According to the urging force of the spring 20, the rotation of the rotary slide member 32 is prevented by the action of the screws of the screw mechanisms 34 and 36. The worm wheel 58 is prevented from moving in the axial direction by the holding case 30, and the meshed state with the worm 54 is well maintained regardless of the axial movement of the rotary slide member 32.
[0026]
When a brake operation device such as a brake pedal or a parking brake operation device such as a parking brake lever is operated by a driver, this is detected by a sensor, and a motor corresponding to the operation amount or operation force is detected. When the electric motor 48 is actuated by torque and the brake rotation is transmitted to the rotary slide member 32 via the worm gear 50, the pair of projecting members 38, 40 whose rotation about the axis is blocked are respectively screwed. The mechanism 34, 36 is moved in the direction of protruding from the rotary slide member 32 by the action of the screws, whereby the pair of brake shoes 16, 18 are expanded to both sides and pressed against the brake drum 24. In this case, since the rotary slide member 32 is disposed so as to be movable in the axial direction (linear direction), both brake shoes 16 and 18 are evenly pressed against the brake drum 24 regardless of dimensional errors and wear. At the same time, there is no possibility that an excessive force is generated in the holding case 30 or the like holding the rotary slide member 32.
[0027]
Further, even when the operation of the electric motor 48 is stopped in a state where the pair of brake shoes 16 and 18 are expanded to both sides in this way, the screw mechanisms 34 and 36 are screwed according to the urging force of the return spring 20. Due to the action, the reverse rotation of the rotary slide member 32 is mechanically prevented by the action of the worm gear 50, so that the brake state in which the pair of brake shoes 16, 18 are expanded is maintained. That is, it can be used as a parking brake, and when the driver operates the parking brake operation device, the operation of the electric motor 48 may be stopped in the brake state.
[0028]
On the other hand, when the parking brake operating device or the service brake operating device is released by the driver, the electric motor 48 is rotated in the reverse direction to the rotation for braking, and accordingly, the rotary slide member 32 is rotated in the reverse direction. As a result, the pair of projecting members 38 and 40 are pulled into the rotary slide member 32 by the action of the screws of the screw mechanisms 34 and 36, respectively. As the projecting members 38 and 40 are retracted, the pair of brake shoes 16 and 18 are brought closer to each other according to the urging force of the return spring 20 and returned to the approach position where they abut against the struts 22. It should be noted that the shoe gap between the brake shoes 16 and 18 and the brake drum 24 can be automatically adjusted by controlling the rotation speed (rotation amount) of the electric motor 48 when releasing the brake to a predetermined rotation speed. The strut 22 can be omitted.
[0029]
Thus, in the present embodiment, when the rotary slide member 32 is rotationally driven, the pair of projecting members 38 and 40 protrude from the rotary slide member 32 to expand the pair of brake shoes 16 and 18, and the worm gear. Since the reverse rotation of the electric motor 48 is prevented by the action 50 and can be used as a parking brake, the motor-driven drum brake actuator 12 capable of parking braking has a simple structure and is inexpensive as a whole. As it is constructed, it is compact and requires a small installation space, thus increasing the degree of design freedom.
[0030]
Further, since the same action as that of the conventional hydraulic wheel cylinder in which the pair of pistons is protruded to both sides by hydraulic pressure and the pair of brake shoes 16 and 18 are expanded, a brake operation can be performed instead of the hydraulic wheel cylinder. Can be detected as an electric signal and used as a service brake.
[0031]
Further, when the electric motor 48 is stopped, the load of the return spring 20 can be reduced as compared with the case where the brake is released by reversely rotating the rotary slide member 32 by the return spring 20. The output of 48 can be reduced, and there is no restriction on the lead of the screw of the screw mechanism 34, 36 between the rotary slide member 32 and the protruding members 38, 40.
[0032]
In addition, the electric motor 48 is disposed on the back side of the backing plate 14 so as to be substantially perpendicular to the backing plate 14, and the worm gear 50 has a worm at the tip of the motor shaft 48 s protruding to the front side of the backing plate 14. 54 is attached, and the rotating slide member 32 is engaged with a worm wheel 58 disposed so as to be relatively movable in the axial direction and not to be rotatable around the shaft center.
[0033]
Further, in the present embodiment, screw mechanisms 34 and 36 are provided at both ends of the rotary slide member 32 so that the pair of projecting members 38 and 40 protrude, so that the axis of the rotary slide member 32 for each brake is provided. The movement in the direction (straight line direction) is small, the operation is stabilized and the durability is improved. Further, since the rotary slide member 32 and the pair of projecting members 38 and 40 are held by the holding case 30 and are assembled to the backing plate 14 via the holding case 30, handling and assembling work can be performed. It becomes easier.
[0034]
Further, since the tool locking portion 52 is provided on the motor shaft 48s of the electric motor 48, the brake can be released by manually rotating the motor shaft 48s at the time of failure.
[0035]
As mentioned above, although the Example of this invention was described in detail based on drawing, these are one embodiment to the last, and this invention is implemented in the aspect which added the various change and improvement based on the knowledge of those skilled in the art. be able to.
[Brief description of the drawings]
FIG. 1 is a view showing a main part of a motor-driven drum brake to which the present invention is applied, and is a front view with a part cut away.
FIG. 2 is a view corresponding to the II-II cross section in FIG. 1;
[Explanation of symbols]
10: Motor-driven drum brake 12: Actuator 14: Backing plate 16, 18: Brake shoe 30: Holding case 32: Rotating slide member 34, 36: Screw mechanism 38, 40: Protruding member 48: Electric motor 50: Worm gear 52: Tool Locking part 54: Worm 58: Worm wheel

Claims (4)

In a leading / trailing-type motor-driven drum brake in which a pair of brake shoes are expanded to both sides by an electric motor and pressed against a brake drum that rotates with a wheel to generate a braking force, based on the brake rotation of the electric motor An actuator for expanding the pair of brake shoes,
On the straight line in the direction in which the pair of brake shoes are expanded, the shaft center is arranged to be movable in the straight line direction so as to coincide with the straight line, and around the straight line as the electric motor rotates. A rotating slide member that is rotationally driven;
The rotary slide member and the straight line direction to both ends fitted relatively rotatably around the line of, along with are interposed between the pair of brake shoes with the rotary slide member, rotation around the line is blocked A pair of protruding members,
The rotary slide member by is driven to rotate in the line around with the rotation brake of the electric motor, the pair of projecting members of the rotary slide action of the screw associated with the relative rotation between the pair of projecting members causes symmetrically relative movement in a direction protruding from member, said along with the reverse rotation of the electric motor so as to symmetrically relative movement in the direction of pulling the pair of projecting members, the rotary slide member and the pair of projecting members A pair of screw mechanisms with opposite leads and equal diameters provided in the mating portion with
A worm wheel disposed on the outer peripheral surface of the rotating slide member via an anti-rotation key or a spline so as to be relatively movable in the axial direction and not to be rotatable around the shaft center. A worm attached to the motor shaft of the motor, and the rotation of the electric motor is decelerated and transmitted to the rotary slide member, and the reverse rotation of the rotary slide member is prevented when the electric motor is stopped , A worm gear in which movement of the worm wheel in the axial direction is prevented and the meshing state with the worm is maintained regardless of movement of the rotating slide member in the axial direction ;
A motor-driven drum brake actuator characterized by comprising: The electric motor, the rotation axis relative to the backing plate of the motor driving the drum brake is disposed on the back side of the backing plate in a posture to be substantially vertical, the tip of the motor shaft protrudes to the front side of the backing plate The motor-driven drum brake actuator according to claim 1, wherein the worm is attached . The rotating slide member is held in a holding case so as to be movable in the axial direction and rotatable about an axis, and the pair of projecting members screwed to both ends of the rotating slide member are held in the holding case. Projecting from the opening formed in the case to both sides, the rotating slide member and the projecting member are assembled to the backing plate of the motor-driven drum brake via the holding case,
3. The motor-driven drum brake actuator according to claim 1 , wherein the worm wheel is prevented from moving in an axial direction by the holding case. 4. The motor-driven drum brake actuator according to any one of claims 1 to 3, wherein the motor shaft of the electric motor is provided with a tool locking portion having an irregular cross section.

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