JP2018009617A - Vehicular brake device - Google Patents

Abstract

[Problem] In a vehicle brake device in which an electric actuator for parking brake is attached to a drum brake, the change in effectiveness between service braking and parking braking is suppressed, the number of parts is reduced, and the drum brake can be easily mounted on a vehicle. [Solution] A first piston 24 that abuts against a first brake shoe and a second piston 25 that forms a hydraulic chamber 27 between the first piston 24 are slidably fitted into a cylinder body 23, a pressing member 26 having one end that can abut against the second piston 25 and the other end that abuts against the second brake shoe is arranged coaxially with the second piston 25 so as to be pressed by the second piston 25 during service braking to apply a thrust to the second brake shoe, and a parking brake mechanism 28 that drives the pressing member 26 in the axial direction in response to the operation of an electric actuator 21 to generate a parking brake force is housed in the cylinder body 23. [Selected Figure] Figure 3

Description

  The present invention relates to first and second brake shoes that can slide in contact with the inner periphery of a brake drum that rotates with a wheel, and thrust that generates a service brake force by driving the first and second brake shoes to expand. The present invention relates to a vehicular brake device in which an electric actuator that exerts power for generating a parking brake force is attached to a back plate of a drum brake that includes a wheel cylinder capable of exhibiting the following.

  In addition to the wheel cylinder that generates the service brake force, it has a parking lever that is connected to the brake cable that is pulled by the power that the electric actuator exerts, and the parking brake by pulling the brake cable to rotate the parking lever A drum brake is known from Japanese Patent Application Laid-Open No. H10-228707.

JP 2014-126146 A

  However, in the one disclosed in Patent Document 1, the action point of the hydraulic force applied to the brake shoe at the time of service brake by hydraulic pressure is different from the action point of the electric force applied to the brake shoe at the time of parking brake by the electric actuator. If the hydraulic pressure is released after the simultaneous operation, the efficacy may change due to the change of the action point. In addition, the number of parts of the mechanism for rotating the parking lever to obtain the parking brake force increases, and considering the wiring of the brake cable and interference with the suspension parts, mounting the drum brake on the vehicle It is hard to say that it is excellent.

  The present invention has been made in view of such circumstances, and it is possible to improve the ease of mounting a drum brake on a vehicle while preventing changes in effectiveness during service braking and parking braking and reducing the number of parts. An object of the present invention is to provide a vehicle brake device.

  In order to achieve the above object, the present invention drives the first and second brake shoes and the first and second brake shoes so as to be in sliding contact with the inner periphery of the brake drum that rotates together with the wheels. In the vehicular brake device, an electric actuator for demonstrating power for generating parking brake force is attached to a back plate of a drum brake having a wheel cylinder capable of generating thrust for generating service brake force. A cylinder body of the wheel cylinder is fixed to the inner surface of the plate, and a second piston is formed between the first piston that contacts the first brake shoe and a fluid pressure chamber that generates fluid pressure during service braking. Is slidably fitted to the cylinder body, and the side opposite to the hydraulic chamber is A pressing member having one end abutting on the two pistons and having the other end abutting on the second brake shoe enables separation from the second piston and at the second piston during the service brake. The electric actuator is disposed coaxially with the second piston so as to apply a thrust to the second brake shoe and is attached to the outer surface of the back plate at a portion corresponding to the pressing member. A first feature is that a parking brake mechanism that generates a parking brake force by driving the pressing member in the axial direction in response to the operation of the cylinder is housed in the cylinder body.

  According to the present invention, in addition to the configuration of the first feature, the output shaft of the electric actuator can rotate around an axis along a plane orthogonal to the axis of the cylinder body, and the back plate and the cylinder The parking brake mechanism has a screw hole that engages with a worm screw provided on the output shaft and a male screw engraved on the outer periphery of the pressing member. An adjusting nut in which a plurality of grooves meshing with the worm screw are formed on the outer periphery; a plurality of rods capable of transmitting reaction force acting on the pressing member from the second brake shoe to the first piston; The rods having an axis parallel to the axis of the cylinder body and outside the hydraulic chamber. The plurality of grooves on the outer periphery of the adjusting nut are slidably fitted to the body and slidably fitted to the pressing member so as to prevent rotation of the pressing member. A second feature is that the second electrode is formed so as to extend parallel to the axis.

  According to the first aspect of the present invention, the pressing member that is pressed during service braking is separated from the second piston by the second piston that forms a hydraulic pressure chamber with the first piston that contacts the first brake shoe. And a parking brake mechanism which is arranged coaxially with the second piston so as to apply thrust to the second brake shoe and which drives the pressing member in the axial direction by the operation of the electric actuator to obtain the parking brake force. Since it is housed in the body, there is no need for a parking lever or brake cable, and the number of parts can be reduced. In addition, there is no need to consider brake cable routing or interference with undercarriage parts. Can be increased. Further, since the thrust at the time of the service brake and the thrust at the time of the parking brake act on the same axis, it is possible to suppress a change in the effectiveness at the time of the service brake and the parking brake.

  According to the second feature of the present invention, the hydraulic pressure exerted by the hydraulic chamber acts on the first and second pistons during service braking, and thrust acts on the first brake shoe from the first piston. A thrust is applied to the second brake shoe from the pressing member pushed by the piston, whereby the first and second brake shoes are expanded to obtain a service brake force. At this time, the adjusting nut as well as the pressing member operates in the axial direction. However, since the groove on the outer periphery of the adjusting nut engaged with the worm screw extends in the axial direction, the adjusting nut is allowed to operate in the axial direction. Further, when the worm screw is rotated by the electric actuator during parking brake, the adjusting nut is rotated, and the pressing member that is screwed into the adjusting nut and prevented from rotating is operated in the axial direction to thrust from the pressing member to the second brake shoe. When the reaction force acting on the pressing member from the second brake shoe is transmitted to the first piston via the rod, the thrust also acts on the first brake shoe, and the first and second brakes The shoe expands and parking brake force is obtained. The axial movement of the adjusting nut during the reaction force transmission at this time is also allowed. In this way, the parking brake mechanism is accommodated in the cylinder body so that the thrust during the service brake and the thrust during the parking brake act on the same axis, but the parking brake mechanism is disposed outside the hydraulic chamber. Therefore, the arrangement of the parking brake mechanism does not affect the shape of the hydraulic chamber.

It is a front view of a drum brake. FIG. 2 is a view taken in the direction of arrow 2 in FIG. 1. FIG. 3 is a simplified cross-sectional view taken along line 3-3 in FIG. 2. FIG. 4 is a simplified cross-sectional view taken along line 4-4 of FIG. It is sectional drawing corresponding to FIG. 4 in the operation state at the time of a service brake. It is sectional drawing corresponding to FIG. 4 in the operation | movement initial state at the time of a parking brake. It is sectional drawing corresponding to FIG. 4 in the operation state at the time of a parking brake.

  The embodiment of the present invention will be described with reference to FIGS. 1 to 7 attached herewith. First, in FIGS. 1 and 2, a drum brake 11 is provided on, for example, a left rear wheel of a four-wheel vehicle. The drum brake 11 is configured to be slidably contacted with the fixed back plate 12 and the inner periphery of the brake drum 13 that rotates together with the left rear wheel. 15, between the first and second brake shoes 14, 15, and the wheel cylinder 16 fixed to the upper portion of the back plate 12 so as to exert a force for expanding the first and second brake shoes 14, 15. And a return spring 17 provided on the front side.

  An anchor block 19 that rotatably supports one end portions of the first and second brake shoes 14, 15 is fixed to the lower portion of the back plate 12, and the first and second brake shoes 14, 15 are fixed. Between the one end portions, a coil spring 20 for urging one end portions of the brake shoes 14 and 15 toward the anchor block 19 is provided. The return spring 17 is provided between the other end portions of the first and second brake shoes 14 and 15 to bias the brake shoes 14 and 15 in the contracting direction.

  The wheel cylinder 16 is actuated by the output hydraulic pressure of a master cylinder (not shown) operated by a brake pedal during service braking, and the first and second brake shoes 14 and 15 are expanded with the anchor block 19 as a fulcrum. It is possible to obtain a service brake force by exerting a driving force to the opening side, and at the time of parking brake, the anchor block 19 is used as a fulcrum by the power exerted by the electric actuator 21 attached to the back plate 12. It is possible to obtain the parking brake force by driving the first and second brake shoes 14 and 15 to the side of expanding.

  3 and 4 together, the cylinder body 23 of the wheel cylinder 16 is fixed to the inner surface of the back plate 12 and is in contact with the first brake shoe 14, and during service braking. A second piston 25, which forms a hydraulic pressure chamber 27 for generating hydraulic pressure with the first piston 24, is slidably fitted to the cylinder body 23, on the opposite side of the hydraulic pressure chamber 27. A pressing member 26 whose one end can be brought into contact with the second piston 25 and whose other end is brought into contact with the second brake shoe 15 allows separation from the second piston 25 and the service brake. It is sometimes arranged coaxially with the second piston 25 so as to be pushed by the second piston 25 to give a thrust to the second brake shoe 15.

  The cylinder body 23 is integrally provided with an inward projecting portion 23a projecting radially inward at the longitudinal intermediate portion thereof, and the first piston 24 is partially in the inward projecting portion 23a. A piston main portion 24a that is slidably fitted, and a flange portion 24b that protrudes radially outward from an end portion of the piston main portion 24a on the first brake shoe 14 side with respect to the inward projection 23a, It is formed so as to integrally have a contact protrusion 24c that protrudes coaxially from the center of the end of the piston main portion 24a on the first brake shoe 14 side with respect to the inward protrusion 23a and contacts the first brake shoe 14. The second piston 25 is slidably fitted into the inward projection 23a. The hydraulic chamber 27 is formed between the piston main portion 24a of the first piston 24 and the second piston 25 so that the outer periphery is defined by the inward projection 23a.

  On the outer periphery of the piston main portion 24 a of the first piston 24, an annular seal member 29 that elastically slides on the inner surface of the inward projection 23 a of the cylinder body 23 is mounted. Further, an annular seal member 30 that is elastically slidably in contact with the inner surface of the inward projecting portion 23a is attached to the outer periphery of the second piston 25, and the hydraulic chambers 27 are arranged on both sides in the axial direction. Sealing is performed by an annular seal member 29 between the piston main portion 24a and the inward projection 23a and an annular seal member 30 between the second piston 25 and the inward projection 23a.

  The cylinder body 23 is provided with a hydraulic pressure passage 31 that penetrates the back plate 12 so as to communicate with the hydraulic pressure chamber 27, and this hydraulic pressure passage 31 has a master cylinder operated by a brake pedal. A continuous brake hose (not shown) is connected. A return spring 32 provided between the first piston 24 and the second piston 25 is accommodated in the hydraulic pressure chamber 27.

  The electric actuator 21 is attached to the outer surface of the back plate 12 at a portion corresponding to the pressing member 26, and the parking force is generated by driving the pressing member 26 in the axial direction according to the operation of the electric actuator 21. A parking brake mechanism 28 is accommodated in the cylinder body 23.

  The electric actuator 21 includes an electric motor 34 (see FIG. 2), and an output shaft 35 of the electric actuator 21 is a plane PL (FIGS. 1, 3, and 4) orthogonal to the axis of the cylinder body 23. (See FIG. 4), while being able to rotate around an axis line along the reference line), the back plate 12 and the cylinder body 23 are penetrated into the cylinder body 23, and the tip end portion of the output shaft 35 is inserted into the cylinder body. 23 is rotatably supported on the side wall.

  The parking brake mechanism 28 includes a worm screw 36 provided on the output shaft 35, and a screw hole 40 that engages with a male screw 39 engraved on the outer periphery of the pressing member 26, and a plurality of meshing meshes with the worm screw 36. An adjusting nut 37 engraved on the outer periphery of the groove 41, and a plurality of rods 38 capable of transmitting a reaction force acting on the pressing member 26 from the second brake shoe 15 to the first piston 24; Is provided.

  The pressing member 26 projects outward in the radial direction from a pressing member main portion 26a having an external thread 39 threadedly engaged with the screw hole 40 and an end of the pressing member main portion 26a on the second piston 25 side. A flange 26b and a contact protrusion 26c that is coaxially protruded from the center of the end of the pressing member main part 26a on the opposite side of the second piston 25 are integrally formed, and the contact protrusion 26 c contacts the second brake shoe 15.

  The plurality of grooves 41 on the outer periphery of the adjusting nut 37 are arranged so that the adjusting nut 37 can move in the axial direction of the cylinder body 23 with respect to the worm screw 36. It is formed to extend in parallel.

  The rod 38 has an axis parallel to the axis of the cylinder body 23 and is slidably fitted to the cylinder body 23 outside the hydraulic chamber 27. The rod 38 is slidably fitted in sliding holes 42 provided at a plurality of, for example, four locations spaced in the circumferential direction of the facing projection 23a and extending in the axial direction of the cylinder bore 23. The flange portion 26b of the pressing member 26 is also provided with a slide hole 43 corresponding to the slide hole 42 individually, and the rod 38 can also slide in the slide hole 43 of the flange portion 26b. Fitted. As a result, the pressing member 26 is prevented from rotating in the cylinder body 23, and rotational force is applied from the worm screw 36 to the adjustment nut 37 as the output shaft 35 of the electric actuator 21 rotates. When transmitted, the pressing member 26 screwed into the adjusting nut 37 moves in the axial direction of the cylinder body 23.

  One end of the rod 38 can contact the flange 24b of the first piston 24. A thrust bearing 44 is interposed between the flange portion 26 b of the pressing member 26 and the adjustment nut 37, and the other end portion of the rod 38 contacts the thrust bearing 44 from the side opposite to the adjustment nut 37. It is possible to contact.

  Further, a boot 45 is provided between the outer periphery of the contact protrusion 24 c of the first piston 24 and the outer periphery of one end of the cylinder body 23, and the outer periphery of the contact protrusion 26 c of the pressing member 26 and the cylinder body. A boot 46 is provided between the outer circumferences of the other end portions of 23.

  According to the wheel cylinder 16 having such a parking brake mechanism 28, the first piston 24 and the second piston 25 are separated from each other at the time of service brake, as shown in FIG. The first brake 24 is pressed by the first piston 24, and the second brake shoe 15 is pressed by the pressing member 26 pressed by the second piston 25, so that service brake force is obtained. It is done. At this time, the adjusting nut 37 of the parking brake mechanism 28 moves in the axial direction of the cylinder body 23 together with the pressing member 26.

  On the other hand, when the electric actuator 21 is actuated during parking brake, as shown in FIG. 6, the adjustment nut 37 is rotated by the engagement of the worm screw 36 with the groove 41 on the outer periphery of the adjustment nut 37, and the rotation within the cylinder body 23 is performed. Since the disabled pressing member 26 is screwed into the adjustment nut 37, the pressing member 26 is driven in the axial direction so as to press the second brake shoe 15, and as shown in FIG. When the reaction force from the side acts on the first piston 24 via the rod 38, the first piston 24 also moves in the axial direction so as to press the first brake shoe 14, and a parking brake force is obtained. It will be.

  Next, the operation of this embodiment will be described. The cylinder body 23 of the wheel cylinder 16 is fixed to the inner surface of the back plate 12 in the drum brake 11, and the first piston 24 that abuts the first brake shoe 14, and during service braking. A second piston 25 that forms a hydraulic pressure chamber 27 that generates a hydraulic pressure with the first piston 24 is slidably fitted to the cylinder body 23, and is opposite to the hydraulic pressure chamber 27. A pressing member 26 having one end abuttable against the second piston 25 and the other end abutting against the second brake shoe 15 enables separation from the second piston 25 and at the time of service braking. The second piston 25 is arranged coaxially with the second piston 25 so as to apply thrust to the second brake shoe 15 by being pushed by the second piston 25. An electric actuator 21 is attached to the outer surface of the back plate 12 at a portion corresponding to the pressing member 26, and a parking brake that generates a parking brake force by driving the pressing member 26 in the axial direction according to the operation of the electric actuator 21. Since the mechanism 28 is accommodated in the cylinder body 23, a parking lever and a brake cable are not necessary, and the number of parts can be reduced, and consideration is given to wiring of the brake cable and interference with underbody parts. Is not required, and the vehicle mountability can be improved. Moreover, since the thrust at the time of service braking and the thrust at the time of parking brake act on the same axis, it is possible to suppress a change in effectiveness at the time of service braking and parking brake.

  In addition, the output shaft 35 of the electric actuator 21 can rotate around an axis along a plane PL orthogonal to the axis of the cylinder body 23 while penetrating the back plate 12 and the cylinder body 23 and the cylinder body. 23, the parking brake mechanism 28 has a worm screw 36 provided on the output shaft 35 and a screw hole 40 that is screwed into a male screw 39 engraved on the outer periphery of the pressing member 26 and the worm. It is possible to transmit to the first piston 24 a reaction force acting on the pressing member 26 from the second brake shoe 15 and an adjusting nut 37 in which a plurality of grooves 41 meshing with the screw 36 are formed on the outer periphery. A plurality of rods 38, and these rods 38 are provided on the cylinder body 23. It has an axis parallel to the line and is slidably fitted to the cylinder body 23 outside the hydraulic chamber 27 and slidable to the pressing member 26 so as to prevent the pressing member 26 from rotating. Thus, the plurality of grooves 41 on the outer periphery of the adjustment nut 37 are formed so as to extend in parallel to the axis of the cylinder body 23.

  Therefore, the adjustment nut 37 is also operated in the axial direction together with the pressing member 26 at the time of service braking, but the outer peripheral groove 41 of the adjustment nut 37 engaged with the worm screw 36 extends in the axial direction. Directional operation is allowed. When the worm screw 36 is rotated by the electric actuator 21 at the time of parking brake, the adjusting nut 37 is rotated, and the pressing member 26 that is screwed into the adjusting nut 37 and is prevented from rotating is operated in the axial direction from the pressing member 26. A thrust acts on the second brake shoe 15, and a reaction force acting on the pressing member 26 from the second brake shoe 15 is transmitted to the first piston 24 via the rod 38, so that the thrust is also exerted on the first brake shoe 14. As a result, the first and second brake shoes 14 and 15 are expanded to obtain a parking brake force. The axial operation of the adjusting nut 37 during the reaction force transmission at this time is also allowed. Thus, the parking brake mechanism 28 is accommodated in the cylinder body 23 so that the thrust at the time of service brake and the thrust at the time of parking brake act on the same axis, but the parking brake mechanism is provided outside the hydraulic pressure chamber 27. 28 is arranged, the arrangement of the parking brake mechanism 28 does not affect the shape of the hydraulic chamber 27 and the like.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various design changes can be made without departing from the present invention described in the claims. Is possible.

DESCRIPTION OF SYMBOLS 11 ... Drum brake 12 ... Back plate 13 ... Brake drum 14 ... 1st brake shoe 15 ... 2nd brake shoe 16 ... Wheel cylinder 21 ... Electric actuator 23 ... Cylinder body 24 ... first piston 25 ... second piston 26 ... pressing member 27 ... hydraulic pressure chamber 28 ... parking brake mechanism 35 ... output shaft 36 ... worm screw 37 ..Adjust nut 38 ... Rod 39 ... Male screw 40 ... Screw hole 41 ... Groove PL ... Flat surface

Claims (2)

  The first and second brake shoes (14, 15) and the first and second brake shoes (14, 15), which can be brought into sliding contact with the inner periphery of the brake drum (13) rotating with the wheels, are driven to expand. And an electric actuator (21) that exerts power for generating a parking brake force on a back plate (12) of a drum brake (11) including a wheel cylinder (16) that can generate a thrust force that generates a service brake force. ) Is attached to the inner surface of the back plate (12), the cylinder body (23) of the wheel cylinder (16) is fixed, and the first piston (14) is in contact with the first brake shoe (14). 24) and a hydraulic chamber (27) for generating hydraulic pressure at the time of service braking is formed between the first piston (24). The second piston (25) is slidably fitted to the cylinder body (23), and one end abuts against the second piston (25) on the side opposite to the hydraulic chamber (27). The pressing member (26) having the other end abutted against the second brake shoe (15) enables separation from the second piston (25) and the second piston during the service brake. The back plate is disposed at a portion corresponding to the pressing member (26), which is arranged coaxially with the second piston (25) so as to be thrust at the second brake shoe (15) by being pushed at (25). The electric actuator (21) is attached to the outer surface of (12), and the pressing member (26) is driven in the axial direction according to the operation of the electric actuator (21) to generate a parking brake force. Parking brake mechanism (28) The vehicular brake system characterized in that it is housed in the cylinder body (23).   The back plate (12) and the cylinder while allowing the output shaft (35) of the electric actuator (21) to rotate about an axis along a plane (PL) orthogonal to the axis of the cylinder body (23). The parking brake mechanism (28) passes through the body (23) and enters the cylinder body (23). The parking brake mechanism (28) includes a worm screw (36) provided on the output shaft (35) and the pressing member (26). An adjustment nut (37) having a screw hole (40) that engages with a male screw (39) engraved on the outer periphery of the screw and a plurality of grooves (41) engaged with the worm screw (36). A reaction force acting on the pressing member (26) from the second brake shoe (15) to the first piston (24). Rods (38), the rods (38) having an axis parallel to the axis of the cylinder body (23) and outside the hydraulic chamber (27), the cylinder body (23). Slidably fitted to the pressing member (26) and slidably fitted to the pressing member (26) so as to prevent rotation of the pressing member (26). The vehicle brake device according to claim 1, wherein the groove (41) is formed to extend in parallel with an axis of the cylinder body (23).

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