JP6460852B2 - Drum brake for vehicles - Google Patents

Description

  The present invention relates to an inward-expanding vehicle drum brake used in vehicles such as automobiles and motorcycles, and more specifically, a pair of brake shoes that are pulled by a pulling means such as a brake cable and arranged on the inner side of a back plate. It is related with the structure of the parking lever which expands.

  2. Description of the Related Art Conventionally, in a vehicle drum brake, a pair of brake shoes are opposed to each other on the inner side of a back plate fixed to a vehicle body, with a base end portion being a rotation center and a distal end side being expandable. There is a type in which the tip side of the front end of the parking lever and one end of the parking lever are rotatably connected by a support shaft, and a traction means is connected to the other end of the parking lever. In some cases, a pair of brake shoes are expanded and the brake shoe lining is slidably brought into contact with the brake drum for braking (see, for example, Patent Documents 1 and 2).

JP 2011-12763 A JP 2006-46385 A

  However, the parking levers disclosed in Patent Documents 1 and 2 described above are formed in a substantially arc shape along the arc of the brake shoe, and when operated, tensile stress is applied to the outer peripheral side and compressive stress is applied to the inner peripheral side. In order not to interfere with other parts during operation, the outer peripheral side is provided with a concave portion, so that there are places where stress is concentrated. For this reason, it is desired to increase the strength of the parking lever. However, if the plate thickness is increased in order to increase the section modulus of the parking lever, the weight increases and the manufacturing cost may increase.

  Accordingly, an object of the present invention is to provide a vehicular drum brake that can disperse the stress concentrated on a specific portion of the parking lever and increase the strength without increasing the thickness of the parking lever.

  In order to achieve the above object, a vehicular drum brake according to the present invention includes a pair of first brakes on the inner side of a back plate fixed to a vehicle body in a state in which a front end side can be expanded with a base end portion as a rotation center. The shoe and the second brake shoe are arranged opposite to each other, the tip widening side of the first brake shoe and one end of the parking lever are connected to each other so as to be rotatable on a support shaft, and the traction means is connected to the other end of the parking lever. In the vehicle drum brake, the parking lever includes a reinforcing rib that is formed in an arc shape that protrudes from the inner peripheral side end surface of the back plate toward the outer peripheral side of the back plate. The rib is provided with a stress concentration portion where stress is concentrated during operation.

  The first brake shoe and the second brake shoe are respectively held by the back plate by a shoe hold pin and a shoe hold spring, and the parking lever is provided to avoid interference with the shoe hold spring. It is preferable that the concave portion has the stress concentration portion. Furthermore, a suspension member is disposed between the traction means coupling side of the parking lever with respect to the support shaft and the tip widening side of the second brake shoe, and the reinforcing rib is formed by the parking lever of the suspension member. A first imaginary line orthogonal to the longitudinal center line connecting the first contact point that contacts the second brake point and the second contact point that contacts the second brake shoe, and passing through the first contact point; It is preferable to form an arc having a center at an intersection with a second imaginary line passing through the stress concentration portion and orthogonal to the imaginary line.

  According to the vehicle drum brake of the present invention, the stress concentration portion where stress is concentrated when the parking lever is operated and the section modulus of the peripheral portion of the stress concentration portion are increased to disperse the stress, thereby increasing the thickness of the parking lever. The strength can be increased.

  Further, the pair of brake shoes are respectively held by the back plate by a shoe hold pin and a shoe hold spring, and the parking lever has a stress concentration portion in a recess provided to avoid interference with the shoe hold spring. As a result, it is possible to improve the strength of the parking lever without increasing the plate thickness by distributing the stress while maintaining the operation of the parking brake satisfactorily.

  Further, a suspension member is disposed between the traction means coupling side of the parking lever support shaft and the distal end widening side of the second brake shoe, and the reinforcing rib is in contact with the parking lever of the suspension member. The first imaginary line passing through the first contact point, the first imaginary line passing through the first contact point, the first imaginary line, and the stress are perpendicular to the longitudinal center line connecting the contact point and the second contact point contacting the second brake shoe. By being formed in an arc shape centering on the intersection with the second imaginary line passing through the concentrated portion, the section modulus of the peripheral portion of the stress concentrated portion can be gently changed, and the stress can be dispersed well. And the strength of the parking lever can be increased.

It is a front view of the drum brake for vehicles which shows one example of the present invention. It is II-II sectional drawing of FIG. It is a front view of the parking lever which shows one example of the present invention. It is IV-IV sectional drawing of FIG.

  FIG. 1 to FIG. 4 are views showing one embodiment of the vehicle drum brake of the present invention. In this vehicle drum brake 1, a pair of first brake shoes 3 and a second brake shoe 4 on the bow side are arranged on the inner surface of a back plate 2 fixed to the vehicle body, and one ends of both brake shoes 3 and 4 are arranged. The other end of the piston of the wheel cylinder 5 is brought into contact with the anchor 6.

  In the vehicle drum brake 1, the first brake shoe 3 and the second brake shoe 4 are expanded outward in the radial direction of the back plate 2, and the outer linings 3a and 4a are slid on the brake drum for braking. In the leading / trading type, the first brake shoe 3 has one end of a parking lever 7 pivotally supported by a support shaft 8, and the other end of the parking lever 7 has a brake cable 9 for pulling the parking lever 7. Are connected.

  The first brake shoe 3 and the second brake shoe 4 are respectively webs 3b, 4b arranged in parallel with the back plate 2, and rims 3c, 4c fixed to the outer edges of the webs 3b, 4b in the crossing direction, The rims 3c and 4c are composed of the linings 3a and 4a attached to the outer peripheral surfaces of the rims 3c and 4c. Further, in the first brake shoe 3 and the second brake shoe 4, substantially intermediate portions of the webs 3 b and 4 b are respectively held by the back plate 2 by shoe hold pins 10 and shoe hold springs 11. Further, between the webs 3b and 4b, shoe return springs 12 and 13 are stretched between the inside of the wheel cylinder 5 and the outside of the anchor 6, and both brake shoes 3 and 4 are always in the direction of diameter reduction. Further, an automatic braking gap adjusting device 14 is disposed on the center side of the back plate of the shoe return spring 12 on the wheel cylinder side.

  The automatic brake clearance adjusting device 14 has a well-known structure, and includes an adjustment lever 16 that is pivotally supported by the second brake shoe 4 by a support shaft 15, and the adjustment lever 16 and the web 4b. One end is fitted to the adjustment spring 17 provided on the end side, the web 3b of the first brake shoe 3 and the parking lever 7, and the other is disposed on the web 4b of the second brake shoe 4 and the base end side of the adjustment lever 16. The connecting rod 18 (the suspension member of the present invention) is fitted to the end. The connecting rod 18 is provided with an adjusting gear 18a at an intermediate portion, and is configured such that a claw piece of the adjusting lever 16 is engaged with the adjusting gear 18a. When the braking gap is expanded by a predetermined amount or more, the connecting rod 18 rotates. By the movement, the adjusting gear 18a is rotated in one direction with a claw piece to extend the connecting rod 18, and the diameter-reduced positions of the first brake shoe 3 and the second brake shoe 4 that are expanded outward in the radial direction of the back plate 2 are set. By restricting to the outside, the braking gap is automatically adjusted.

  The anchor 6 is formed by fixing a rectangular parallelepiped anchor block 6a with rivets 19 and 19 to an anchor portion formed by projecting the back plate 2 inward. A cable guide 20 for guiding the brake cable 9 is provided on the center side of the back plate of the anchor block 6a.

  The parking lever 7 is disposed along the web 3b on the back plate side of the web 3b, and an insertion hole 7a of the support shaft 8 is formed on one end side, and a connecting portion 7b of the brake cable 9 is formed on the other end side. . The parking lever 7 is formed by punching with a press, and one end side is formed along the curve of the web 3b, and a contact portion P1 with the connecting rod 18 is provided on the inner peripheral side of the back plate on one end side. Is provided. Further, a concave portion 7c is formed on the outer peripheral side of the back plate at an intermediate position of the parking lever 7 in order to avoid interference with the shoe hold spring 11, and a stress concentration portion P2 where stress is concentrated during operation is provided in the concave portion 7c. It is done.

  In addition, a reinforcing rib 7d formed in an arc shape that protrudes toward the back plate outer peripheral side from the inner peripheral side end surface of the back plate is formed at the intermediate portion of the parking lever 7, The stress concentration portion P2 is provided in the reinforcing rib 7d. The reinforcing rib 7d is formed by pressing at the same time as the parking lever 7 is punched. The reinforcing rib 7d contacts the first contact point P1 of the connecting rod 18 that contacts the parking lever 7 and the second brake shoe 4. A first imaginary line L1 passing through the first abutting point P1 perpendicular to the longitudinal center line CL1 connecting the second abutting point P3, and perpendicular to the first imaginary line L1, and a stress concentration portion P2. Is formed in an arc shape centering on the intersection P4 with the second imaginary line L2.

  When the brake cable 9 is pulled, the vehicle drum brake 1 of the present embodiment formed as described above slides while the brake cable 9 is guided by the cable guide 20 and pulls the parking lever 7. The parking lever 7 pivots about the support shaft 8 to push the connecting rod 18 toward the second brake shoe 4 side, expands the second brake shoe 4 with the anchor 6 as a fulcrum, and the lining 4a to the brake drum. Slid into contact. Further, when the brake cable 9 is pulled, the parking lever 7 is rotated by changing the rotation fulcrum to the first contact point P1 with the connecting rod 18 by the reaction, and the first brake shoe 3 is expanded using the anchor 6 as a fulcrum. The lining 3a is brought into sliding contact with the brake drum for braking.

  At this time, a tensile stress is applied to the outer peripheral side of the parking lever 7 and a compressive stress is applied to the inner peripheral side, and the stress is concentrated on the stress concentration portion P2 provided in the concave portion 7c, but the stress concentration portion P2 is in the reinforcing rib 7d. Therefore, the stress can be dispersed by increasing the sectional modulus of the stress concentration portion P2 and the peripheral portion of the stress concentration portion P2. Thereby, the strength can be increased without increasing the thickness of the parking lever 7.

  Further, the reinforcing rib 7d is orthogonal to the longitudinal center line CL1 that connects the first contact point P1 that contacts the parking lever 7 of the connecting rod 18 and the second contact point P3 that contacts the second brake shoe 4, and The first imaginary line L1 passing through the first contact point P1 and the second imaginary line L2 orthogonal to the first imaginary line L1 and passing through the stress concentration portion P2 are formed in an arc shape centered on the intersection P4. By doing so, the section modulus of the peripheral part of the stress concentration part P2 can be changed gently, and the stress can be dispersed well.

  The present invention is not limited to the above-described embodiment. A strut is provided as a suspension member between the parking lever and the first brake shoe expansion side without providing an automatic braking gap adjusting device. But you can. Further, the present invention can be applied to any type of drum brake having a parking lever, such as a duo servo type and a cam type drum brake, as well as a leading / trading type drum brake.

DESCRIPTION OF SYMBOLS 1 ... Vehicle drum brake, 2 ... Back plate, 3 ... 1st brake shoe, 4 ... 2nd brake shoe, 3a, 4a ... Lining, 3b, 4b ... Web, 3c, 4c ... Rim, 5 ... Wheel cylinder, 6 DESCRIPTION OF SYMBOLS ... Anchor, 7 ... Parking lever, 7a ... Insertion hole, 7b ... Connection part, 7c ... Recess, 7d ... Reinforcement rib, 8 ... Support shaft, 8a ... Center axis, 9 ... Brake cable, 10 ... Shoe hold pin, 11 ... Shoe hold springs 12, 13 ... Shoe return springs, 14 ... Automatic brake clearance adjusting device, 15 ... Support shaft, 16 ... Adjust lever, 17 ... Adjust spring, 18 ... Connecting rod, 19 ... Rivet, 20 ... Cable guide, P1 ... 1st contact point, P2 ... Stress concentration part, P3 ... 2nd contact point, P4 ... Intersection point

Claims (3)

A pair of first brake shoes and a second brake shoe are disposed opposite to each other on the inner side of a back plate fixed to the vehicle body, with the base end portion being the center of rotation and the front end side being expandable. In the vehicular drum brake in which the front end widening side and one end of the parking lever are rotatably connected by a support shaft, and the traction means is connected to the other end of the parking lever.
The parking lever includes a reinforcing rib formed in an arc shape that protrudes toward the back plate side and protrudes from the end surface on the inner peripheral side of the back plate toward the outer peripheral side of the back plate. A drum brake for a vehicle, characterized in that a stress concentrating part for concentrating the water is provided.   The first brake shoe and the second brake shoe are respectively held by the back plate by a shoe hold pin and a shoe hold spring, and the parking lever is a recess provided to avoid interference with the shoe hold spring. The vehicle drum brake according to claim 1, further comprising the stress concentration portion.   A suspension member is disposed between the traction means connecting side of the parking lever with respect to the support shaft and the tip widening side of the second brake shoe, and the reinforcing rib contacts the parking lever of the suspension member. A first imaginary line orthogonal to a longitudinal center line connecting the first abutting point in contact with the second abutting point abutting on the second brake shoe and passing through the first abutting point; and the first imaginary line The vehicle drum brake according to claim 1, wherein the vehicular drum brake is formed in an arc shape centering on an intersection with a second imaginary line passing through the stress concentration portion.

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