JP2018004045A - Drum brake for vehicle - Google Patents

Abstract

An object of the present invention is to provide a vehicle drum brake in which the point of contact between an anchor fixed to a backing plate and a shoe web is less likely to shift. An anchor (28) integrally fixed to a backing plate (16) has a contact surface (28f) against which a part of one end of a pair of brake shoes (20, 22) abuts. are formed with grooves 28h. Since a part of one end of the pair of brake shoes 20, 22 is fitted into the groove 28h, the pair of brake shoes 20, 22 can be held stably. Therefore, it is possible to suppress the occurrence of displacement of the position where the anchor 28 and a part of the one end portion of the pair of brake shoes 20, 22 abut against each other. It is suppressed, and the buckling strength as initially set (designed) is obtained. [Selection drawing] Fig. 1

Description

  The present invention relates to a vehicular drum brake, and more particularly to a vehicular drum brake including an anchor with which a brake shoe abuts when a parking brake is operated.

  An anchor fixed integrally with the backing plate is provided, and the anchor is provided between one end portions of a pair of brake shoes disposed on the backing plate so as to be expandable, and one end of the pair of brake shoes when the parking brake is operated. Each of the pair of brake shoes has a strength that buckles and deforms prior to the plastic deformation of the anchor with respect to excessive accompanying torque. It has been known. For example, the drum brake for vehicles of patent documents 1 and 2 is it.

JP 2014-163441 A Japanese Utility Model Publication No. 5-50174

  The vehicle drum brakes of Patent Documents 1 and 2 include an anchor that is integrally fixed to a backing plate, and the anchor is disposed between one end portions of a pair of brake shoes that are arranged to be expandable on the backing plate. The one end part of a pair of brake shoes is made to contact | abut at the time of parking brake operation. In the above Patent Documents 1 and 2, a pair of brake shoes is formed with an engagement portion that engages with one end of each pair of brake shoes. The movement of the brake shoe is regulated.

  However, in a vehicle drum brake, when an emergency brake while a vehicle is running, a so-called parking brake, is dynamically activated, a so-called torque that causes the tire to rotate is excessively increased by an anchor via a brake shoe. The buckling deformation of the brake shoe caused by being received becomes a new problem. In vehicle drum brakes, in consideration of parts replacement and maintenance, a pair of brake shoes are used to prevent the backing plate or anchor against the excessive torque that is input when the parking brake is dynamically operated. Since it is configured with a strength that causes buckling deformation prior to plastic deformation, it can be dealt with only by replacing the brake shoe. Specifically, in the vehicle drum brake described in Patent Documents 1 and 2, when the parking brake is dynamically operated and one end of the brake shoe is brought into contact with the anchor, The surface direction, that is, the surface direction of the shoe web and the input direction of the accompanying torque input to the anchor via the brake shoe are not the same direction, but are inclined. As a result, a shift occurs at a position where the anchor and the shoe web are brought into contact with each other, and since the shift is increased, the brake shoe is likely to buckle and the buckling strength is reduced.

  The present invention has been made against the background of the above circumstances, and an object of the present invention is to provide a vehicular drum brake in which the contact point between the anchor fixed on the backing plate and the shoe web is difficult to shift. It is in.

  The gist of the present invention is that: (a) an anchor provided integrally with a backing plate is provided, and the anchor is disposed between one end portions of a pair of brake shoes arranged to be expandable on the backing plate. And the anchors have contact surfaces with which one end portions of the pair of brake shoes abut when the parking brake is operated, and the pair of brake shoes against the excessive accompanying torque. And (b) grooves that extend in the surface direction of the backing plate are formed in the contact surface, respectively. (C) When the one end portions of the pair of brake shoes are brought into contact with the contact surfaces, a part of the one end portion of the pair of brake shoes is fitted into the groove. In that it is urchin formed.

  According to the present invention, the anchor integrally fixed to the backing plate has a contact surface with which one end portions of the pair of brake shoes are contacted when the parking brake is operated, and the contact surface Are formed with grooves in the surface direction of the backing plate. The groove is formed so that a part of one end of the pair of brake shoes is fitted therein. Thereby, since a part of one end part of the pair of brake shoes is fitted into the groove, the pair of brake shoes can be stably held. Therefore, when the parkin brake is dynamically actuated and excessive accompanying torque is received by the anchor via the pair of brake shoes, the anchor and a part of one end of the pair of brake shoes are Since it is possible to suppress the displacement of the abutting positions, a decrease in the buckling strength of the pair of brake shoes is suppressed, and the buckling strength as originally set (designed) can be obtained.

It is a front view showing a drum brake for vehicles provided with an anchor of one example to which the present invention is applied. It is a figure which expands and shows the anchor shown in FIG. 1, and shows the top view of an anchor. It is a figure which expands and shows the anchor shown in FIG. 1, and shows the side view of an anchor. FIG. 3 is a diagram illustrating a positional relationship between an anchor and a pair of brake shoes in a vehicle drum brake according to an embodiment to which the present invention is applied. FIG. 6 is a diagram showing the behavior of a pair of brake shoes when a parking brake is dynamically actuated in a vehicle drum brake according to an embodiment to which the present invention is applied. In the conventional vehicle drum brake, it is a figure which shows the positional relationship of an anchor and a pair of brake shoes. In the conventional drum brake for vehicles, it is a figure showing a behavior of a pair of brake shoes when a parking brake is actuated dynamically.

  An embodiment of the present invention will be described below with reference to the drawings. In the following embodiments, the drawings are appropriately simplified or modified, and the dimensional ratios, shapes, and the like of the respective parts are not necessarily drawn accurately.

  FIG. 1 is a front view showing a duo servo type vehicle drum brake 10 according to an embodiment of the present invention, and shows a state in which a hat type disc and a caliper of a duo servo type drum-in disc brake 12 are removed. . The hat type disk is composed of a disc-shaped outer peripheral portion and a bottomed cylindrical central portion (not shown), and the disc-shaped outer peripheral portion functions as a friction plate of the disc brake, and the bottomed cylindrical central portion Functions as a brake drum. A circle indicated by a one-dot chain line in FIG. 1 indicates the inner peripheral surface 14 of the bottomed cylindrical central portion. The vehicle drum brake 10 includes a disc-shaped backing plate 16 that is integrally fixed to a vehicle body side member such as an axle tube, an axle housing, and a suspension device (not shown), that is, a non-rotating member. A disk cover 18 is secured to the outer periphery of the backing plate 16 to protect the disk-shaped outer periphery of the hat type disk. Further, the vehicle drum brake 10 is arranged substantially in contrast to the center line C1 of the backing plate 16 so as to be able to approach and separate from each other with the arcuate convex side facing outward on the left and right outer peripheral portions of the backing plate 16. A pair of brake shoes 20, 22 are provided, which are provided on the backing plate 16 so as to be expandable. The vehicular drum brake 10 has a pair of brake shoes 20, 22 at one end, that is, a spreader 24 provided at a fixed position between the upper ends of FIG. A coiled return spring 26 for energizing and abutting against the expansion device 24 and an anchor 28 fixed between these upper ends are provided. Further, the vehicle drum brake 10 is interposed between the other ends of the pair of brake shoes 20, 22, that is, the lower end of FIG. A gap adjusting device 32 that adjusts the gap, and an intermediate portion that is stretched between the lower end portions and constantly urges the lower end portions in a direction approaching each other to clamp the gap adjusting device 32 in the longitudinal direction are coiled. The spring 34 is provided. The center line C1 is a line passing through the center in the longitudinal direction of the gap adjusting device 32, the center in the longitudinal direction of the anchor 28, and the center of the backing plate 16 in the front view of FIG. An arrow F shown in FIG. 1 indicates the direction of rotation of a wheel (tire) (not shown) provided with the vehicle drum brake 10 during forward travel, that is, the direction of generation of accompanying torque when the parking brake is operated.

  Each of the pair of brake shoes 20 and 22 has a flat plate shape substantially parallel to the plate surface of the backing plate 16, and shoe webs 36 and 38 that are entirely curved in an arc shape in the front view shown in FIG. Arc-shaped shoe rims 40, 42 integrally fixed so that the cross-sections of the pair of brake shoes 20, 22 form a substantially T-shape along the outer peripheral side end portions of the shoe webs 36, 38 having the arc shape. And linings 44 and 46 made of a friction material integrally fixed to the outer peripheral surfaces of the shoe rims 40 and 42 with an adhesive or the like. In the present embodiment, one end portions of the pair of brake shoes 20 and 22 are in contact with the contact surfaces 28f of the anchors 28, which will be described later, respectively. Further, the tip ends of one end portions of the pair of brake shoes 20 and 22 are formed so that the shoe webs 36 and 38 protrude in the circumferential direction from the shoe rims 40 and 42, respectively. This portion is fitted into a groove 28h of the anchor 28 described later.

  The pair of brake shoes 20 and 22 are pressed toward the backing plate 16 by shoe hold-down devices 48 and 50 disposed near the center in the longitudinal direction of the shoe webs 36 and 38 so that the backing can be expanded. It is disposed on the plate 16.

  FIG. 2 is an enlarged view of the anchor 28 shown in FIG. 1, and shows a plan view of the anchor 28. FIG. 3 is an enlarged view of the anchor 28 shown in FIG. 1, and shows a side view of the anchor 28. The anchor 28 is obtained by bending an inexpensive metal plate such as a rolled steel plate at a substantially right angle, and the cross section of the anchor 28 is formed in a substantially L shape. The anchor 28 is provided with a fixed portion 28b having a flat fixed surface 28a that is fixed to the backing plate 16 by being substantially brought into surface contact with the entire surface. The anchor 28 is provided with a cable insertion hole 28c and an anchoring hole 28d that have an opening in the anchoring surface 28a and penetrate the anchoring portion 28b. A parking brake cable (not shown) is inserted into the cable insertion hole 28c, and a fixing bolt (not shown) for fixing the anchor 28 is inserted into the fixing hole 28d. Further, a flat seat surface 28e is formed on the side opposite to the fixed surface 28a, for example, by coining at the periphery of the fixed hole 28d.

  Further, the anchor 28 is provided with a contact portion 28g that has a pair of contact surfaces 28f that are raised substantially at right angles to the fixed surface 28a and that contact one end portions of the pair of brake shoes 20 and 22, respectively. ing. Specifically, the shoe rims 40 and 42 are in contact with the pair of contact surfaces 28f, respectively. A groove 28h extending in the surface direction of the backing plate 16, that is, a groove 28h extending substantially parallel to the fixed surface 28a is formed on the contact surface 28f. The groove 28h is a height of the contact surface 28f where a part of one end of the pair of brake shoes, specifically, the shoe webs 36 and 38 are fitted, respectively, in a state where the groove 28h is assembled to the vehicle drum brake 10. It is formed in the position. The groove 28h has a groove width larger than the thickness dimension of the shoe webs 36, 38 so that the shoe webs 36, 38 can be stably fitted, and the grooves 28h can be fitted sufficiently. Has depth. Therefore, the groove 28h has a pair of brake shoes 20, when an operating force is applied to a parking lever (not shown) via a parking brake cable, for example, by operating a parking brake lever (not shown), that is, when the parking brake is activated. When one end portion of 22, that is, the shoe rims 40, 42 are brought into contact with the contact surface 28 f, a part of one end portion of the pair of brake shoes 20, 22, that is, the shoe webs 36, 38 is fitted.

  FIG. 4 is a diagram showing a positional relationship between the anchor 28 and the pair of brake shoes 20 and 22 in the vehicle drum brake 10 according to one embodiment to which the present invention is applied. FIG. 5 shows a pair of brake shoes 20 and 22 in the case where an emergency brake, for example, a so-called parking brake is dynamically operated while the vehicle is running in the vehicle drum brake 10 to which the present invention is applied. It is a figure which shows a behavior. When the parking brake is operated, if the accompanying torque due to the friction between the pair of brake shoes 20 and 22 is generated in the direction of the force in which the tire is to rotate, for example, in the direction of the arrow F as shown in FIG. The turning torque is applied in the direction of the arrow shown in FIG. 5 so that the brake shoe 20 is brought into contact with the anchor 28. In particular, when the parking brake is dynamically operated, an excessive follower torque is received by the anchor 28 via the brake shoe 20 as compared with a normal parking brake operation, for example, a parking brake operation while the vehicle is stopped. Will be.

  As shown in FIG. 5, when the parking brake is operated, a part of one end of the brake shoe 20, that is, the shoe web 36 is fitted into the groove 28 h formed in the anchor. The anchor 28 is provided with a groove 28h, and the shoe web 36 is fitted into the groove 28h, so that when the parking brake is operated, the pair of brake shoes 20 is stably held by the anchor 28. Become. That is, by providing the anchor 28 with the groove 28h, when the parking brake is operated, for example, the pair of brake shoes 20 are in an unstable state such that the pair of brake shoes 20 moves up and down in the height direction of the contact portion 28g. It is suppressed from being brought into contact with. As a result, for example, when the parking brake is dynamically operated, the brake shoe 20 is brought into contact with the anchor 28, and an excessive accompanying torque exceeding the design value is received by the anchor 28 via the brake shoe 20. However, the buckling deformation of the brake shoe 20, that is, the decrease in the buckling strength is suppressed, and the buckling strength as originally set (designed) can be obtained. In addition, the brake shoe 20 has a thickness and material of the brake shoes 20 and 22 that are strong enough to buckle and deform before the plastic deformation of the backing plate 16 and the anchor 28 with respect to the excessive accompanying torque. Since it is configured by being selected, the plastic deformation of the anchor 28 is also suppressed. Here, for example, when the parking brake is operated, if the force that the tire tries to rotate, that is, the accompanying torque occurs in the reverse direction to the direction of the arrow F shown in FIG. It will be received by the anchor 28 via the shoe 22.

  FIG. 6 is a diagram showing a positional relationship between the anchor 100 and the pair of brake shoes 102 and 104 in the conventional vehicle drum brake 10. FIG. 7 is a diagram showing the behavior of the pair of brake shoes 102 and 104 when the parking brake is dynamically operated in the conventional vehicle drum brake 10. As in FIG. 4, shoe webs 106, 108 are formed in part of one end of the pair of brake shoes 102, 104 so as to protrude in the circumferential direction from the shoe rims 110, 112. When the parking brake is operated, for example, when a follow-up torque is applied in the direction of the arrow shown in FIG. 7, the brake shoe 102 is brought into contact with the anchor 100. Here, in the conventional anchor 100, since a groove is not formed in the contact surface 100a with which one end portions of the pair of brake shoes 102 and 104 abut, for example, the parking brake is dynamically operated and an excessively large engagement is caused. When the turning torque is received by the anchor 100 via the brake shoe 102, the buckling strength of the brake shoe 102 is lowered as shown in FIG. Specifically, since the groove for fitting the shoe web 106 is not formed on the contact surface 100a of the anchor 100, the position of the shoe web 106 is not stable. Deviation occurs in the direction of rotation torque input. If an excessive accompanying torque is applied, the deviation reduces the buckling strength of the brake shoe 102, so that the brake shoe 102 is likely to buckle and the backing plate 16 and the brake shoe 102 Will be transformed. Here, as shown in FIG. 7, the brake shoe 102 has a bending direction upward in the height direction of the anchor 100 and causes buckling deformation. However, depending on the component accuracy of the brake shoe 102 or the anchor 100, For example, the anchor 100 may have a bending direction downward in the height direction to cause buckling deformation. Further, depending on the component accuracy of the brake shoe 102 or the anchor 100, the brake shoe 102 may have a bending direction toward the outer peripheral direction of the brake shoe 102 or the inner peripheral direction of the brake shoe 102 and cause buckling deformation. is there.

  The groove 28h stably holds the brake shoe 20, so that no deviation occurs between the surface direction of the shoe web 36 and the input direction of the accompanying torque, and this deviation occurs when an excessive accompanying torque is applied. The buckling deformation of the brake shoe 20 due to is difficult to occur. Thus, for example, when the parking brake is dynamically operated, even if the brake shoe 20 is brought into contact with the anchor 28 and excessive accompanying torque is received by the anchor 28 via the brake shoe 20, the brake shoe 20 The buckling deformation of 20 is suppressed and the breakage of the brake shoe 20 is suppressed. According to an experiment by the present inventor, the pair of brake shoes 20 and 22 has a strength of 15% compared to the conventional pair of brake shoes 102 and 104 in which the groove 28h is not formed by forming the groove 28h. It has risen by 20%. Further, since the buckling deformation can be suppressed by forming the groove 28h, for example, it is not necessary to perform induction hardening on the shoe webs 36 and 38 that are in contact with the anchor 28 in order to measure the strength of the pair of brake shoes 20 and 22. Therefore, the cost can be reduced.

  Thus, according to this embodiment, the anchor 28 integrally fixed to the backing plate 16 is in contact with a part of one end of the pair of brake shoes 20 and 22 when the parking brake is operated. A groove 28h extending in the surface direction of the backing plate 16 is formed on the contact surface 28f. The groove 28h is formed so that a part of one end of the pair of brake shoes 20 and 22 is fitted. Thereby, since a part of one end part of a pair of brake shoes 20 and 22 is each fitted by the groove | channel 28h, a pair of brake shoes 20 and 22 can be hold | maintained stably. Therefore, when the parkin brake is dynamically actuated and excessive carry torque is received by the anchor 28 via the pair of brake shoes 20, 22, the anchor 28 and one end of the pair of brake shoes 20, 22 are Since it is possible to suppress the displacement of the position where a part of the brake shoes 20 abuts, a decrease in the buckling strength of the pair of brake shoes 20 and 22 is suppressed, and the buckling strength as originally set (design) is obtained. It is done.

  It should be noted that the above description is merely an embodiment, and other examples are not illustrated. However, the present invention is implemented in variously modified and improved modes based on the knowledge of those skilled in the art without departing from the spirit of the present invention. Can do.

10: Drum brake for vehicle 16: Backing plate 20, 22: Brake shoe 28: Anchor 28f: Contact surface 28g: Groove 36, 38: Shoe web

Claims (1)

An anchor fixed integrally to the backing plate, and the anchor is provided between one end portions of a pair of brake shoes arranged to be expandable on the backing plate, and the anchor is operated when the parking brake is operated. Each of the pair of brake shoes has an abutment surface against which one end of the pair of brake shoes abuts, and the pair of brake shoes has a strength to buckle deform before the anchor plastic deformation with respect to an excessive accompanying torque. A drum brake for a vehicle comprising:
Grooves extending in the surface direction of the backing plate are formed on the contact surfaces,
The vehicular drum, wherein one end of each of the pair of brake shoes is fitted into the groove when the one end of the pair of brake shoes is brought into contact with the contact surface. brake.

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