JPH0636348Y2 - Duo servo type drum brake - Google Patents

Description

TECHNICAL FIELD The present invention relates to a duo-servo type drum brake.

2. Description of the Related Art A pair of brake shoes arranged so as to be capable of expanding on a backing plate in a state where respective one ends facing each other are connected, and a pair of brake shoes fixed on the backing plate, and the other ends of the brake shoes are A pair of shoe return springs each having an anchor member to be brought into contact with each other, a coil portion and a pair of hook portions extending from both ends in the axial direction of the coil portion, and tensioned between the anchor member and the brake shoe, respectively. A duo-servo type drum brake equipped with is known.

In such a duo-servo type drum brake, a plate-shaped member larger than the outer peripheral shape of the portion of the anchor member with which the brake shoe abuts is usually provided at a position separated from the backing plate of the anchor member by a predetermined distance. The plate-shaped member prevents the other end of the brake shoe from floating in a direction away from the backing plate due to vibration, impact, or the like when the vehicle is traveling. Further, as described in, for example, Japanese Utility Model Laid-Open No. 57-98333, it is fixed on the backing plate at a position close to the other end of the brake shoe without separately providing the above-mentioned plate member. The wheel cylinder is provided with a protruding portion, and the protruding portion prevents the brake shoe from rising.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, in such a duo-servo type drum brake, the other end of the brake shoe and a part to which the anchor member of the backing plate is fixed or a part to which the wheel cylinder of the backing plate is fixed are Since the distance between the brake shoes is usually inevitable, a relatively large gap is formed between the other end of the brake shoe and the protruding portion of the plate-shaped member or the wheel cylinder. When the floating of the end portion occurs, if the rotating drum is located closer to the backing plate due to its variation, the brake shoe may come into axial contact with the rotating drum, causing drag and uneven wear of the brake. In some cases, it could not be reliably prevented.

Means for Solving Problems The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a distance between a flange portion or a protrusion and the other end of the brake shoe. It is an object of the present invention to provide a duo-servo type drum brake that prevents the brake shoe from being lifted and thereby abutting the rotating drum in the axial direction to cause dragging and uneven wear due to the variation of To do.

In order to achieve such an object, the present invention provides a pair of brake shoes, which are arranged on a backing plate so as to be able to open each other in a state where respective opposite ends are connected to each other, and are fixed on the backing plate. , An anchor member having an anchor portion with which the other end portion of the brake shoe is brought into contact and a hooked portion positioned on the opposite side of the backing plate from the anchor portion, a coil portion and both ends in the axial direction thereof. A pair of hooking portions extending from the anchor member, and a pair of shoe return springs tensioned between the anchor member and the brake shoe, and a hook of the anchor member. While providing a flange-shaped portion projecting outwardly from the anchor portion between the stopper portion and the anchor portion, the pair of shoe return springs The hooking portion on the side hooked on the anchor member is formed in a state of being inclined at a predetermined angle with respect to the axis of the coil portion in a direction away from the brake shoe, and the coil portion is brought into contact with the brake shoe. In order to press it toward the backing plate side, the hooking part is hooked to the hooked part of the anchor member in a state of being preloaded to the backing plate side.

With this configuration, one of the shoe return springs is hooked to the anchor member while being preloaded to the backing plate, so that the brake shoe is coiled by the shoe return spring. Since it is pressed to the backing plate side with a predetermined pressing force, lifting of the other end of the brake shoe in a direction away from the backing plate is effectively suppressed. As a result, even if a relatively large gap is formed between the other end of the brake shoe and the flange-shaped portion, the other end of the brake shoe is prevented from being lifted up more reliably. This eliminates dragging and uneven wear of the brake shoes.

Further, since the hooking portion of the shoe return spring is not extended, it is sufficient to incline the hooking portion at a predetermined angle in the direction away from the brake shoe with respect to the axis of the coil portion, which reduces the manufacturing cost. It does not increase.

Moreover, since the hooking portions of the pair of shoe return springs are inclined at a predetermined angle with respect to the axis of the coil portion, the other end of the brake shoe is prevented from being lifted up in any rotation direction of the rotating drum. Therefore, it is possible to effectively prevent the abrasion and uneven wear of the brake shoes.

Embodiment Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

In FIG. 2, a pair of brake shoes 12 and 14 are supported on the backing plate 10 by shoe hold down devices 16 and 18 so as to be able to expand each other. Brake shoe 1
The reference numerals 2, 14 have arc-shaped and strip-shaped shoe rims 20, 22, and shoe webs 24, 26 projecting from the inner peripheral sides of the shoe rims 20, 22 and positioned substantially parallel to the backing plate 10. The shoe rims 20, 22 are supported on the backing plate 10 in a state in which one side portion in the width direction of the shoe rims 20 and 22 is in contact with a plurality of ledge portions 28 (see FIG. 1) integrally provided on the backing plate 10. Has been done. Shoe web 24,2
The opposite ends of 6 are engaged with both ends of the adjuster 29 whose axial length is variable, and are urged toward each other by springs (not shown). Thus, the adjuster 29 connects the respective one ends of the brake shoes 12 and 14. On the other hand, the other ends of the shoe webs 24, 26 are adapted to be brought into contact with the anchor members 30 fixed on the backing plate 10, respectively, and the anchor members 30 and both brake shoes 12, 14 are provided. The shoe return springs 32 and 34 respectively stretched between the two are constantly urged in directions toward each other. One brake shoe
A parking brake lever 36 having a parking cable (not shown) connected to one end thereof is rotatably attached to the other end side (anchor member 30 side) of the other 12 side, and those brakes are also provided. Struts 38 are bridged between the shoe 12 and the parking brake lever 36 and the other brake shoe 14. Since the operation of the duo servo type drum brake is not always necessary for understanding the present invention and is well known, its detailed description will be omitted.

The anchor member 30 has a fixing portion 40 as shown in FIG.
And an anchor portion 42 protruding from the fixing portion 40 and forming a columnar shape as a whole.
Is fixed on the backing plate 10, and the other end portions of the shoe webs 24 and 26 are brought into contact with the outer peripheral surface of the anchor portion 42, respectively. At the tip of the anchor portion 42, a plate-shaped portion 46 is inserted into the male screw member.
The plate-shaped member 46 and the shoe webs 24, 26 are fastened together by means of 48, and a relatively large gap L is formed between the plate-shaped member 46 and the shoe webs 24, 26 due to variations in the protruding dimension of the ledge portion 28 from the backing plate 10. Are formed. As a result of the plate member 46 being fixed to the anchor member 30 by the male screw member 48 as described above, the anchor member 30 has the anchor portion 42 against which the shoe webs 24, 26 are brought into contact and the head portion of the male screw member 48. A flange portion that is configured to include a hooked portion 54 to be described later that is hooked, and the plate member 46, and that projects between the anchor portion 42 and the hooked portion to the outer peripheral side of the anchor portion 42. And are provided.

As shown in FIGS. 1 and 2, the shoe return springs 32 and 34 are each configured to have a coil portion 50 and a pair of hook portions 52 and 54 extending from both ends in the axial direction thereof. One of the hook portions 52 is hooked together with the tip of the male screw member 48, and the other hook portion 52 is
54 are hooked in through holes 56, 58 provided in the shoe webs 24, 26, respectively. In the state before being hooked to the male screw member 48, the one hooking portion 52 is in a direction away from the backing plate 10 with respect to the axial center of the coil portion 50, as shown by the alternate long and short dash line in FIG. Is inclined by a predetermined angle, and the tip of the hook portion 52 is located in a direction away from the backing plate 10 by a predetermined distance from the tip of the male screw member 48. As a result, when the retaining portion 52 shown by the alternate long and short dash line is retained on the male screw member 48 while pressing the retaining portion 52 toward the backing plate 10, the retaining portion 52 is in a state of being preloaded on the backing plate 10 side. Coil part 50
As shown by the arrow in FIG. 1, a predetermined pressing force for pressing the shoe web 26 toward the backing plate 10 side is generated at the end of the hooking portion 52 side. The same applies to the shoe web 24. The predetermined pressing force is based on the preload of the hooking portion 52 so that the anchor shoe 30 side ends of the brake shoes 12 and 14 can be effectively suppressed from floating in the direction away from the backing plate 10. That is, the length dimension of the hooking portion 52, the inclination angle of the hooking portion 52 before hooking, the shoe return springs 32, 3
It is determined in advance based on the material, wire diameter, etc. of 4.

As described above, according to the present embodiment, the hooking portions 52 of the shoe return springs 32 and 34 are hooked to the male screw member 48 of the anchor member 30 in a state of being preloaded to the backing plate 10 side, respectively, and The brake shoes 12 and 14 are pressed by the portion 50 toward the backing plate 10 with the predetermined pressing force, and the lifting of the end portions of the brake shoes 12 and 14 on the side of the anchor member 30 from the backing plate 10 is effective. Suppressed to. Accordingly, even if the gap L is formed between the end portions of the shoe webs 24 and 26 on the anchor member 30 side and the plate-like member 46, the end portions of the brake shoes 12 and 14 on the anchor member 30 side are formed. Lifting is prevented more reliably than in the past, and along with that, brake drag due to the lifting of the brake shoes 12 and 14 and uneven wear of the linings of the brake shoes 12 and 14 are effective. To be prevented. Moreover, such an effect can be obtained without increasing the number of parts at all.

In addition, in the above-mentioned embodiment, the case where the present invention is applied to the duo servo type drum brake having only the parking brake mechanism has been described, but the anchor member is provided between the respective other ends of the both brake shoes with the backing plate. If it is a duo-servo type drum brake of the type that is fixed above and the shoe return springs are stretched between the anchor members and both brake shoes, even if it is equipped with a predetermined service brake mechanism. Of course, the present invention can be applied.

In addition, the present invention can be variously modified without departing from the spirit thereof.

[Brief description of drawings]

FIG. 1 is an enlarged view showing a main part of a cross section taken along the line II of FIG. FIG. 2 is a front view showing a main part of a duo servo type drum brake to which the present invention is applied. 10: Backing plate 12, 14: Brake shoe 30: Anchor member 32, 34: Shoe return spring 50: Coil part 52, 54: Hook part

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hiromi Kato 1 Toyota-cho, Toyota-shi, Aichi Toyota Motor Co., Ltd. (56) Bibliographic references Sho 47-2272 (JP, Y1)

Claims (1)

[Scope of utility model registration request] 1. A pair of brake shoes, which are arranged on the backing plate so as to be capable of expanding with respect to each other, in a state where respective one ends facing each other are connected, and each of the brake shoes fixed to the backing plate. An anchor member having an anchor portion with which the end portion abuts and a hooked portion positioned on the opposite side of the backing plate from the anchor portion, and a pair of hooks extending from the coil portion and both ends in the axial direction thereof. A pair of shoe return springs that are respectively stretched between the anchor member and the brake shoe, and a pair of shoe return springs are provided between the anchor member and the brake shoe. While providing a flange-shaped portion protruding toward the outer peripheral side from the anchor portion,
The hook portions of the pair of shoe return springs that are hooked on the anchor member are formed in a state of being inclined at a predetermined angle in a direction away from the brake shoe with respect to the axis of the coil portion, and the coil portion is formed. So that it abuts on the brake shoe and presses it toward the backing plate side, it is hooked on the hooked portion of the anchor member in a state in which the hooking portion is preloaded to the backing plate side. Duo servo type drum brake.