JP6596292B2 - Brake device for vehicle - Google Patents

Description

The present invention enables the first and second brake shoes arranged in the inner space of the back plate to be able to slide in contact with the inner periphery of the brake drum that rotates together with the wheels, and allows one end portions of these brake shoes to rotate. An anchor block provided on the back plate to be supported, and first and second pistons that individually contact the other ends of the first and second brake shoes, and the first and second brake shoes are expanded. The present invention relates to a vehicular brake device in which an electric actuator that exerts power for generating parking brake force is attached to a drum brake that includes a wheel cylinder that can drive and generate thrust for generating service brake force.

  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 described above, the number of parts of the mechanism for rotating the parking lever to obtain the parking brake force increases, and the brake cable is routed and interferes with the suspension parts. In view of the above, it is difficult to say that the drum brake is easily mounted on a vehicle.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a vehicle brake device in which the number of parts is reduced and the mounting performance of a drum brake on a vehicle is improved.

In order to achieve the above object, the present invention provides first and second brake shoes arranged in an inner space of a back plate so as to be slidable in contact with an inner periphery of a brake drum that rotates together with wheels, and the brake shoes. An anchor block provided on the back plate so as to rotatably support one end of the first and second pistons individually abutting against the other ends of the first and second brake shoes and a first piston And a drum brake having a wheel cylinder capable of exerting a thrust to generate a service brake force by expanding and driving the second brake shoe, and an electric actuator that exerts a power for generating a parking brake force. In the brake device for a vehicle, the cylinder body of the wheel cylinder includes first and Two pistons are slidably fitted and fixed to the inner surface of the back plate, and the electric actuator is attached to the outer surface of the back plate at a portion corresponding to the cylinder body. A parking brake mechanism that drives the first and second pistons in the axial direction to generate a parking brake force is housed in the cylinder body, and the first piston and a hydraulic chamber that generates hydraulic pressure during service braking are provided in the first chamber. An intermediate piston formed between the first piston and the intermediate piston is liquid-tightly and slidably fitted to the cylinder body, and the second piston connected to and connected to the intermediate piston is connected to the intermediate piston. An operating chamber is formed in the cylinder body so that rotation around the axis is impossible, and the cylinder body is slidably fitted to the motor body. The output shaft of the actuator has an axis along a plane orthogonal to the axis of the cylinder body, penetrates the back plate and the cylinder body, and enters the working chamber, and the parking brake mechanism includes the first piston. A rod arranged coaxially with the cylinder body so that the other end is coaxially screwed to the second piston, and a worm wheel provided on the output shaft, It is composed of a cylindrical worm so as to mesh with the worm wheel is provided in a relatively non-rotatable manner in the axial direction intermediate portion of the rod to the first aspect of Rukoto.

According to the present invention, in addition to the configuration of the first feature, a shaft portion that is coaxially liquid-tightly and slidably fitted to the intermediate piston is fixed to the first piston, and one end portion of the rod is A second feature is that the shaft can be coaxially contacted.

Furthermore, the present invention enables the first and second brake shoes arranged in the inner space of the back plate to be able to slide in contact with the inner periphery of the brake drum that rotates together with the wheels, and one end of the brake shoes to be rotated. An anchor block provided on the back plate so as to support the first and second brake shoes, and first and second pistons individually contacting the other ends of the first and second brake shoes, and the first and second brake shoes are expanded. In the vehicle brake device, an electric actuator for demonstrating power for generating parking brake force is attached to a drum brake having a wheel cylinder capable of exerting thrust to generate service brake force by being driven open. The cylinder body of the cylinder slides on the first and second pistons. And the electric actuator is mounted on the outer surface of the back plate at a portion corresponding to the cylinder body, and the first and second pistons are moved according to the operation of the electric actuator. A parking brake mechanism that generates a parking brake force by driving in an axial direction is housed in the cylinder body, and a hydraulic chamber that generates a hydraulic pressure during service brake is provided between the first piston and the first piston. The second piston, which is formed but cannot rotate around the axis, is fluid-tightly and slidably fitted to the cylinder body, and the output shaft of the electric actuator is orthogonal to the axis of the cylinder body The cylinder body is liquid-tightly penetrated while passing through the back plate with an axis along a plane. The parking brake mechanism is inserted into the pressure chamber, and the parking brake mechanism is arranged coaxially with the cylinder body so that one end can be brought into contact with the first piston and the other end is screwed coaxially with the second piston. that rod and a worm wheel provided on said output shaft, a third feature that it is constituted by a cylindrical worm provided relatively unrotatably to the axially intermediate portion of the rod so as to mesh with the worm wheel And

According to the first feature of the present invention, since the parking brake mechanism for obtaining the parking brake force by the operation of the electric actuator is accommodated in the cylinder body, the parking lever and the brake cable are not required, and the number of parts is reduced. In addition, it is not necessary to pay attention to the wiring of the brake cable and the interference with the suspension parts, so that the vehicle mountability can be improved. In addition, a working chamber is formed between the intermediate piston that forms a hydraulic pressure chamber with the first piston and a second piston that is linked and connected to the intermediate piston, and the output shaft of the electric actuator is formed in the working chamber. The cylindrical worm that meshes with the worm wheel provided on the rod is provided in the middle portion of the rod whose one end is in contact with the first piston so as not to rotate relatively, and the other end of the rod cannot rotate in the cylinder body. Since it is screwed coaxially with the second piston, at the time of service braking, the first piston and the intermediate piston operate in directions away from each other when the hydraulic pressure is applied to the hydraulic chamber, and the first brake shoe is moved by the first piston. While being pressed, the service brake force is obtained by pressing the second brake shoe with the second piston interlocked and connected to the intermediate piston. On the other hand, at the time of parking brake, the rod rotates through the worm wheel and the cylindrical worm by the operation of the electric actuator, and the rod is screwed to the second piston which cannot be rotated in the cylinder body. Is driven in the axial direction to press the second brake shoe, and the reaction force from the second brake shoe side acts on the first piston via the rod, so that the first piston also presses the first brake shoe. Therefore, the parking brake force can be obtained. In addition, most of the parking brake mechanism is accommodated in the working chamber, and the parking brake mechanism is not affected by the brake fluid.

According to the second feature of the present invention, the shaft portion fixed to the first piston is coaxially liquid-tightly and slidably fitted to the intermediate piston, and one end portion of the rod is coaxially connected to the shaft portion. Since the contact is possible, one end of the rod can be brought into contact with the first piston with a simple structure with a reduced number of parts.

Furthermore, according to the third feature of the present invention, the cylindrical worm meshing with the worm wheel provided on the output shaft of the electric actuator in the hydraulic chamber formed between the first piston and the second piston has one end. Since the other end of the rod is coaxially screwed to the second piston which cannot be rotated in the cylinder body, it is provided at the middle portion of the rod abutted against the first piston. When the hydraulic pressure is applied to the hydraulic chamber, the first piston and the second piston operate in directions away from each other, the first piston presses the first brake shoe, and the second piston presses the second brake shoe. Service brake power is obtained. On the other hand, at the time of parking brake, the rod rotates through the worm wheel and the cylindrical worm by the operation of the electric actuator, and the rod is screwed to the second piston which cannot be rotated in the cylinder body. Is driven in the axial direction to press the second brake shoe, and the reaction force from the second brake shoe side acts on the first piston via the rod, so that the first piston also presses the first brake shoe. Therefore, the parking brake force can be obtained. Moreover, the parking brake mechanism is accommodated in the hydraulic chamber, and the parking brake mechanism can be accommodated in the cylinder body without increasing the size of the cylinder body.

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. 1 for illustrating the configuration of the wheel cylinder and the parking brake mechanism. FIG. 4 is a cross-sectional view taken along line 4-4 of FIG. FIG. 5 is a sectional view taken along line 5-5 of FIG. It is sectional drawing which shows the operating state (a) at the time of the service brake of a wheel cylinder and a parking brake mechanism, and the operating state (b) at the time of a parking brake. It is sectional drawing corresponding to FIG. 3 of 2nd Embodiment. It is sectional drawing which shows the operating state (a) at the time of the service brake of a wheel cylinder and a parking brake mechanism, and the operating state (b) at the time of a parking brake.

  Embodiments of the present invention will be described with reference to the accompanying drawings.

  The first embodiment of the present invention will be described with reference to FIGS. 1 to 6. First, in FIGS. 1 and 2, a drum brake 11A is provided on the left rear wheel of a four-wheel vehicle, for example. The drum brake 11A is capable of slidingly contacting 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 and 15, and the wheel cylinder 16 </ b> A fixed to the upper portion of the back plate 12 so that the first and second brake shoes 14 and 15 exert an expanding operation force. 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 16A is actuated by the output hydraulic pressure of a master cylinder (not shown) operated by a brake pedal, and opens the first and second brake shoes 14, 15 with the anchor block 19 as a fulcrum. The outer end portions of the first and second pistons 21A and 22A included in the wheel cylinder 16A are opposed to the other end portions of the first and second brake shoes 14 and 15, respectively. Are arranged as follows.

  Referring also to FIG. 3, a cylinder body 23A of the wheel cylinder 16A is fixed to the inner surface of the back plate 12 by slidably fitting first and second pistons 21A and 22A. An electric actuator 24 that exhibits power for generating a parking brake force is attached to the outer surface of the back plate 12 at a portion corresponding to the body 23A, and the first and second pistons are operated according to the operation of the electric actuator 24. A parking brake mechanism 25A that drives the shafts 21A and 22A in the axial direction to generate a parking brake force is housed in the cylinder body 23A.

  The cylinder body 23A slides between the first piston 21A and an intermediate piston 27 that forms a fluid pressure chamber 26 that generates fluid pressure during service braking with the first piston 21A. The second piston 22A, which is freely fitted and interlocked with and connected to the intermediate piston 27, forms a working chamber 28 between the intermediate piston 27 and disables rotation around the axis line to the cylinder body 23A. It is slidably fitted.

  An annular seal member 29 that elastically slides into contact with the inner surface of the cylinder body 23A is attached to the outer periphery of the first piston 21A, and the outer periphery of the intermediate piston 27 is elastically applied to the inner surface of the cylinder body 23A. An annular seal member 30 that is slidably contacted is mounted, and the hydraulic pressure chamber 26 has an annular seal member 29 between the first piston 21A and the cylinder body 23A, the intermediate piston 27, Sealed with an annular seal member 30 between the cylinder bodies 23A. The cylinder body 23A is connected to a hydraulic pressure introducing pipe 31 that penetrates the back plate 12 so as to communicate with the hydraulic pressure chamber 26. A brake pedal is connected to the outer end of the hydraulic pressure introducing pipe 31. A brake hose (not shown) connected to the master cylinder to be operated is connected.

  In FIG. 4, the second piston 22A is slidably fitted, and, for example, a plurality of locations on the inner surface of the cylinder body 23A are provided with axially extending grooves 32, and the second piston 22A. For example, protrusions 33 protruding from a plurality of locations on the outer periphery of the slidably fit into the groove 32. By fitting the protrusion 33 into the groove 32, the second piston 22A is slidably fitted to the cylinder body 23A while allowing axial movement and disabling rotation around the axis.

  The electric actuator 24 includes an electric motor 35, and an output shaft 36 of the electric actuator 24 has an axis along a plane PL (see FIGS. 1 and 3) orthogonal to the axis of the cylinder body 23A. Thus, it penetrates through the back plate 12 and the cylinder body 23A and enters the working chamber 28, and the tip of the output shaft 36 is rotatably supported by the side wall of the cylinder body 23A.

  Referring also to FIG. 5, the parking brake mechanism 25A is configured such that the other end is coaxially screwed to the second piston 22A while allowing one end to contact the first piston 21A. A rod 38A disposed coaxially with the cylinder body 23A, a worm wheel 39 provided on the output shaft 36, and an axially intermediate portion of the rod 38A provided so as not to rotate relative to the worm wheel 39. In this embodiment, the cylindrical worm 40 is provided integrally with the rod 38A so that it cannot rotate relative to the rod 38A and cannot move relative to the axial direction.

  In FIG. 3 again, the intermediate piston 27 is provided with a through hole 41 coaxially, and a shaft portion 42 fixed to the first piston 21A is fitted in the through hole 41 in a liquid-tight and slidable manner. Combined. In this embodiment, the shaft portion 42 is provided integrally with the first piston 21A. However, a shaft portion that is a member different from the first piston 21A may be coaxially fixed to the first piston 21A. An annular seal member 43 that is elastically slidably brought into sliding contact with the inner surface of the through hole 41 is mounted on the outer periphery of the shaft portion 42, and the rod 38 </ b> A is disposed at the end of the shaft portion 42 on the working chamber 28 side. A receiving recess 44 is formed for fitting and abutting one end of each. Further, a coiled spring 47 is interposed between the first piston 21A and the intermediate piston 27 so as to surround a part of the shaft portion 42. The spring 47 is connected to the hydraulic chamber 26. The first piston 21A and the intermediate piston 27 are urged toward the side where the volume is increased, thereby preventing the first piston 21A from returning due to vibration.

  By the way, the rod 38A rotates in response to the operation of the electric actuator 24. Therefore, the shaft portion 42 with which one end portion of the rod 38A abuts, and the first piston 21A integrated with the shaft portion 42 are connected to the rod 38A. In order to prevent rotation with 38A, one or more axially extending grooves 45 are formed in a portion of the through hole 41 near the working chamber 28, and an outer periphery of the shaft portion 42 is formed. One or a plurality of protrusions 46 are slidably fitted into the groove 45.

  A male screw 48 is engraved on the outer periphery of the other end of the rod 38A, and a bottomed screw hole 49 for screwing the male screw 48 is opened to the working chamber 28 side, so The piston 22A is provided coaxially.

  Further, a plurality of, for example, two connecting rods 52 are provided between the intermediate piston 27 and the second piston 22 </ b> A, and the second piston 22 </ b> A is interlocked with the intermediate piston 27 via the connecting rod 52. , Will be connected.

  Next, the operation of the first embodiment will be described. The cylinder body 23A of the wheel cylinder 16A is slidably fitted to the first and second pistons 21A and 22A and fixed to the inner surface of the back plate 12. The electric actuator 24 is attached to the outer surface of the back plate 12 at a portion corresponding to the cylinder body 23A, and the first and second pistons 21A and 22A are driven in the axial direction in accordance with the operation of the electric actuator 24, and the parking brake force Since the parking brake mechanism 25A that generates the engine is housed in the cylinder body 23A, a parking lever and a brake cable are unnecessary, the number of parts can be reduced, and the brake cable can be routed and interfered with the suspension parts. This eliminates the need for consideration for the It is possible.

  Also, the first piston 21A and an intermediate piston 27 that forms a hydraulic chamber 26 that generates hydraulic pressure during service braking between the first piston 21A and the cylinder body 23A are fluid-tight and slidably fitted. The second piston 22A linked to and coupled to the intermediate piston 27 is slidably fitted to the cylinder body 23A while forming the working chamber 28 with the intermediate piston 27 and disabling rotation around the axis. The output shaft 36 of the electric actuator 24 has an axis along a plane PL orthogonal to the axis of the cylinder body 23A, passes through the back plate 12 and the cylinder body 23A, and enters the working chamber 28, thereby entering the parking brake mechanism 25A. However, the other end is coaxially screwed to the second piston 22A while allowing one end to contact the first piston 21A. A rod 38A disposed coaxially with the Linda body 23A, a worm wheel 39 provided on the output shaft 36, and a cylinder provided on the intermediate portion in the axial direction of the rod 38A so as not to rotate relative to the worm wheel 39. In this embodiment, the cylindrical worm 40 is provided integrally with the rod 38A.

  According to the wheel cylinder 16A provided with such a parking brake mechanism 25A, during service braking, the first piston 21A and the intermediate piston 27 can interact with each other during the hydraulic action on the hydraulic chamber 26 as shown in FIG. The first brake shoe 14 is pressed by the first piston 21A, and the second brake shoe 15 is pressed by the second piston 22A that is linked and connected to the intermediate piston 27. Service brake force can be obtained. At this time, the rod 38A of the parking brake mechanism 25A operates in the axial direction together with the cylindrical worm 40 and the second piston 22A, and one end of the rod 38A is separated from the shaft 42 of the first piston 21A.

  On the other hand, at the time of parking brake, as shown in FIG. 6B, the rod 38A is rotated through the worm wheel 39 and the cylindrical worm 40 by the operation of the electric actuator 24, and the rotation in the cylinder body 23A is disabled. Since the rod 38A is screwed to the two piston 22A, the second piston 22A is driven in the axial direction so as to press the second brake shoe 15, and the reaction force from the second brake shoe 15 side is passed through the rod 38A. By acting on the first piston 21A, the first piston 21A also moves in the axial direction so as to press the first brake shoe 14, and a parking brake force is obtained.

  Moreover, the parking brake mechanism 25A is housed in the working chamber 28, and the parking brake mechanism 25A is not affected by the brake fluid.

  A shaft portion 42 that is coaxially liquid-tight and slidably fitted to the intermediate piston 27 is fixed to the first piston 21A, and one end portion of the rod 38A can be coaxially abutted on the shaft portion 42. Therefore, the end of the rod 38A can be brought into contact with the first piston 21A with a simple structure with a reduced number of parts.

  A second embodiment of the present invention will be described with reference to FIG. 7 and FIG. 8, but the parts corresponding to the first embodiment are indicated by the same reference numerals and shown in detail. The detailed explanation is omitted.

  First, in FIG. 7, the cylinder body 23B of the wheel cylinder 16B of the drum brake 11B is fixed to the inner surface of the back plate 12 by slidably fitting the first and second pistons 21B and 22B. An electric actuator 24 that exhibits power for generating a parking brake force is attached to the outer surface of the back plate 12 at a portion corresponding to 23B, and the first and second pistons 21B according to the operation of the electric actuator 24. , 22B are driven in the axial direction and a parking brake mechanism 25B for generating a parking brake force is accommodated in the cylinder body 23B.

  In the cylinder body 23B, the second piston 21B and the second pressure chamber 53 that generates a hydraulic pressure during service braking are formed between the first piston 21B and the second piston is disabled from rotating around its axis. The piston 22B is fitted fluid-tightly and slidably.

  An annular seal member 54 that elastically slides into contact with the inner surface of the cylinder body 23B is mounted on the outer periphery of the first piston 21B, and the outer surface of the second piston 22B is elastically applied to the inner surface of the cylinder body 23B. An annular seal member 55 that comes into sliding contact is mounted.

  The cylinder body 23B is connected to a hydraulic pressure introducing pipe 31 that penetrates the back plate 12 so as to communicate with the hydraulic pressure chamber 53.

  Grooves 56 extending in the axial direction are provided at, for example, a plurality of locations on the inner surface of the cylinder body 23B outside the seal member 55 mounted on the outer periphery of the second piston 22B. For example, protrusions 57 protruding from a plurality of locations on the outer periphery of 22B are slidably fitted into the grooves 56. By fitting the protrusions 57 into the grooves 56, the second piston 22B is slidably fitted to the cylinder body 23B while being able to move in the axial direction and being unable to rotate around the axis.

  The output shaft 36 of the electric actuator 24 has an axis along a plane PL orthogonal to the axis of the cylinder body 23B, and penetrates the back plate 12 and liquid-tightly penetrates the cylinder body 23B. An annular seal member 58 is interposed between the cylinder body 23 </ b> B and the output shaft 36. The tip end of the output shaft 36 is rotatably supported by the side wall of the cylinder body 23B.

  The parking brake mechanism 25B is disposed coaxially with the cylinder body 23B such that one end can be brought into contact with the first piston 21B and the other end is coaxially screwed with the second piston 22B. A rod 38B, a worm wheel 39 provided on the output shaft 38B, and a cylindrical worm provided in the axially intermediate portion of the rod 38B so as not to rotate relative to the shaft 38B and capable of relative movement in the axial direction so as to mesh with the worm wheel 39 In this embodiment, the cylindrical worm 40 is integrally provided on the rod 38B.

  A receiving recess 60 for inserting and abutting one end of the rod 38B is formed at the center of the surface of the first piston 21B facing the hydraulic chamber 53. A coiled spring 59 is interposed between the rod 38B and the first piston 21B. The spring 59 is contracted between the inner end blocking surface of the receiving recess 60 and a flange 61 provided on the rod 38B on the first piston 21B side with respect to the cylindrical worm 40. It works to prevent the return of one piston 21B.

  By the way, the rod 38B rotates in response to the operation of the electric actuator 24. Therefore, in order to prevent the first piston 21B with which one end of the rod 38B comes into contact with the rod 38B, the seal member A plurality of axially extending grooves 62 are provided at, for example, a plurality of locations on the inner surface of the cylinder body 23B at the axially outer side than 54, and projecting portions projecting at, for example, a plurality of locations on the outer periphery of the first piston 21B. 63 is slidably fitted into the groove 62. The fitting of the protrusion 63 to the groove 62 prevents the second piston 22B from rotating with the rod 38B.

  According to the second embodiment, during service braking, as shown in FIG. 8A, the first piston 21B and the second piston 22B are separated from each other when the hydraulic pressure is applied to the hydraulic chamber 53. The first brake 21 (see the first embodiment) is pressed by the first piston 21B, and the second brake shoe 15 (see the first embodiment) is pressed by the second piston 22B. Service brake power is obtained. At this time, the rod 38B of the parking brake mechanism 25B operates in the axial direction together with the cylindrical worm 40 and the second piston 22B, and one end of the rod 38B is separated from the first piston 21B.

  On the other hand, at the time of parking brake, as shown in FIG. 8 (b), the rod 38B rotates through the worm wheel 39 and the cylindrical worm 40 by the operation of the electric actuator 24, and the rotation in the cylinder body 23B is disabled. Since the rod 38B is screwed to the two piston 22B, the second piston 22B is driven in the axial direction so as to press the second brake shoe 15, and the reaction force from the second brake shoe 15 side is transmitted via the rod 38B. By acting on the first piston 21B, the first piston 21B also moves in the axial direction so as to press the first brake shoe 14, and a parking brake force is obtained.

  Moreover, the parking brake mechanism 25B is accommodated in the hydraulic chamber 53, and the parking brake mechanism 25B can be accommodated in the cylinder body 23B without increasing the size of the cylinder body 23B.

  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.

  For example, in the above-described embodiment, the cylindrical worm 40 is provided integrally with the rods 38A and 38B, but the cylindrical worm 40 may be provided on the rods 38A and 38B so as not to be rotatable relative to the rod 38A and 38B. .

11A, 11B ... drum brake 12 ... back plate 13 ... brake drum 14 ... first brake shoe 15 ... second brake shoe 16A, 16B ... wheel cylinder 19 ... anchor block 21A, 21B ... 1st piston 22A, 22B ... 2nd piston 23A, 23B ... Cylinder body 24 ... Electric actuator 25A, 25B ... Parking brake mechanism 26, 53 ... Hydraulic pressure chamber 27 ... Intermediate piston 28 ... Working chamber 36 ... Output shafts 38A, 38B ... Rod 39 ... Worm wheel 40 ... Cylindrical worm 42 ... Shaft PL ... Plane

Claims (3)

First and second brake shoes (14, 15) arranged in the inner space of the back plate (12) so as to be able to slide in contact with the inner periphery of the brake drum (13) rotating with the wheels, and the brake shoes ( 14, 15) at one end of the first and second brake shoes (14, 15) and the anchor block (19) provided on the back plate (12) so as to rotatably support one end thereof. It has first and second pistons (21A, 22A; 21B, 22B) that abut against each other and exerts thrust to generate service brake force by driving the first and second brake shoes (14, 15) to expand. A drum brake (11A, 11B) having a wheel cylinder (16A, 16B) to obtain power for generating a parking brake force The vehicle brake system electric actuator (24) is attached to volatilization,
The cylinder bodies (23A, 23B) of the wheel cylinders (16A, 16B) are slidably fitted to the first and second pistons (21A, 22A; 21B, 22B), so that the back plate (12) The electric actuator (24) is attached to the outer surface of the back plate (12) at a portion corresponding to the cylinder body (23A, 23B) and fixed to the inner surface, and the first according to the operation of the electric actuator (24). And a parking brake mechanism (25A, 25B) for generating a parking brake force by driving the second piston (21A, 22A; 21B, 22B) in the axial direction is housed in the cylinder body (23A, 23B) ,
The first piston (21A) and an intermediate piston (27) that forms a hydraulic pressure chamber (26) that generates hydraulic pressure during service braking with the first piston (21A) include the cylinder body (23A). ) Is fluid-tightly and slidably fitted to the intermediate piston (27), and the second piston (22A) coupled to and coupled to the intermediate piston (27) is in the working chamber (28). The output shaft (36) of the electric actuator (24) is orthogonal to the axis of the cylinder body (23A). The parking brake has an axis along a plane (PL) that passes through the back plate (12) and the cylinder body (23A) and enters the working chamber (28). The structure (25A) allows the one end part to come into contact with the first piston (21A) and the other end part is coaxially screwed with the second piston (22A). A rod (38A) arranged coaxially, a worm wheel (39) provided on the output shaft (36), and an axially intermediate portion of the rod (38A) so as to mesh with the worm wheel (39) brake system according to claim Rukoto consists out with relatively unrotatably provided are cylindrical worm (40). A shaft portion (42), which is coaxially liquid-tight and slidably fitted to the intermediate piston (27), is fixed to the first piston (21A), and one end portion of the rod (38A) is the shaft portion. The vehicular brake device according to claim 1 , wherein the vehicular brake device can be abutted coaxially with (42). First and second brake shoes (14, 15) arranged in the inner space of the back plate (12) so as to be able to slide in contact with the inner periphery of the brake drum (13) rotating with the wheels, and the brake shoes ( 14, 15) at one end of the first and second brake shoes (14, 15) and the anchor block (19) provided on the back plate (12) so as to rotatably support one end thereof. It has first and second pistons (21A, 22A; 21B, 22B) that abut against each other and exerts thrust to generate service brake force by driving the first and second brake shoes (14, 15) to expand. A drum brake (11A, 11B) having a wheel cylinder (16A, 16B) to obtain power for generating a parking brake force The vehicle brake system electric actuator (24) is attached to volatilization,
The cylinder bodies (23A, 23B) of the wheel cylinders (16A, 16B) are slidably fitted to the first and second pistons (21A, 22A; 21B, 22B), so that the back plate (12) The electric actuator (24) is attached to the outer surface of the back plate (12) at a portion corresponding to the cylinder body (23A, 23B) and fixed to the inner surface, and the first according to the operation of the electric actuator (24). And a parking brake mechanism (25A, 25B) for generating a parking brake force by driving the second piston (21A, 22A; 21B, 22B) in the axial direction is housed in the cylinder body (23A, 23B),
The second piston, which is formed between the first piston (21B) and a hydraulic chamber (53) for generating a hydraulic pressure during service braking, and cannot rotate around the axis. (22B) is fluid-tightly and slidably fitted to the cylinder body (23B), and the output shaft (36) of the electric actuator (24) is orthogonal to the axis of the cylinder body (23B). The parking brake mechanism is inserted into the hydraulic chamber (53) through the cylinder body (23B) in a fluid-tight manner while passing through the back plate (12) and having an axis along the plane (PL). (25B) allows the one end to come into contact with the first piston (21B) and the other end of the second piston (22B) is coaxially screwed with the cylinder body (23B). A rod (38B) disposed on the shaft, a worm wheel (39) provided on the output shaft (38B), and an axially intermediate portion of the rod (38B) so as to mesh with the worm wheel (39) car dual brake system you characterized by being constituted out with relatively unrotatably provided are cylindrical worm (40).

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