JPH0638189Y2 - 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 on a backing plate so as to be capable of expanding each other, a connecting mechanism for connecting opposite end portions of the brake shoes, and a brake mechanism fixed on the backing plate. An anchor member that receives the braking torque transmitted to the brake shoes when the other ends are brought into contact with each other, a linear portion, a curving portion that curls at the tip of the linear portion, and an extension from the tip of the curving portion. Has a substantially U-shaped hook composed of an opposed portion facing the linear portion at one end, and the hook is hooked on a plate-shaped hooking member provided on the backing plate to thereby form the hooking member and the hooking member. A tension coil spring that is stretched between one brake shoe and urges one brake shoe toward the other brake shoe. A duo-servo type drum brake having a ring is known. Such a duo-servo type drum brake is a rotary drum having a bottomed cylindrical shape with its inner peripheral surface facing the outer peripheral surfaces of both brake shoes with a small gap therebetween and in a state of being rotatable relative to these brake shoes. Is provided, and the dragging of the brake is effective because the one coil shoe (secondary shoe) is biased toward the other brake shoe (primary shoe) by the tension coil spring in the rotating drum. It is supposed to be prevented.

The hook member is usually provided with a notch whose plate surface is positioned substantially parallel to the straight portion of the hook and which opens toward the other brake shoe side. The hook is designed to be hooked.

Problems to be solved by the invention However, in the state of the drum brake assembly before the rotary drum of such a duoservo type drum brake is assembled, both brake shoes can be moved relatively large together with the coupling mechanism using the anchor member as a fulcrum. There are cases. In such a case, as the one brake shoe is moved to the other brake shoe side, the tension coil spring is relatively moved to the other brake shoe side so that the tip of the facing portion of the hook is moved. There is a case where the bent portion of the hook protrudes from the opening of the notch and the hook comes out of the notch although the notch has not yet crossed the notch bottom of the hooking member.

Means for Solving the Problems The present invention has been made in view of the above circumstances, and an object thereof is to effectively disengage the hook of the tension coil spring from the hooking member. It is to provide a duo-servo type drum brake which can be prevented. In order to achieve such an object, the present invention, in the duo servo type drum brake as described above, has an engaging hole penetrating in the plate thickness direction where the hook is hooked, and a portion provided with the engaging hole. The engaging member is provided with an engaging portion whose plate surface is positioned in a direction intersecting the longitudinal direction of the spring, and the spring is applied so that the straight portion of the hook is positioned on the engaging hole side. It is characterized by being hooked on a stop member.

With this configuration, the engaging portion of the latching member is positioned such that the plate surface of the portion provided with the engaging hole intersects the longitudinal direction of the spring, and Since the spring is hooked so that the straight part of the hook is located on the engagement hole side, the tension coil spring moves to the other brake shoe side as one brake shoe moves to the other brake shoe side. The hook is effectively prevented from being disengaged from the engaging hole even when the hook is rotated relatively largely.

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 the shoe hold down devices 16 and 18 so as to be able to expand each other while being pressed toward the backing plate 10 with a predetermined pressing force. ing. The opposite ends of the brake shoes 12 and 14 are adjusted by the adjuster 20.
Are engaged with both end portions of each and are biased toward each other by a spring (not shown). The adjuster 20 connects the respective one ends of the brake shoes 12 and 14 in a state where the axial length thereof is variable, and constitutes the connecting mechanism in the present embodiment. On the other hand, the other end of each of the brake shoes 12 and 14 is adapted to be brought into contact with the side surface of the anchor pin 22 fixed on the backing plate 10, and the anchor pin 22 and both brake shoes 12 and 14 are connected to each other. The return springs 24 and 26 respectively stretched between the two are constantly urged in the directions toward each other. This anchor pin 22
Constitute the anchor member in this embodiment. On the other end side (anchor pin 22 side) of one brake shoe 12,
A parking brake lever 28, to one end of which a parking cable (not shown) is connected, is rotatably attached at the other end, and between one brake shoe 12 and the parking brake lever 28 and the other brake shoe 14. Struts 32 are suspended.

As shown in FIGS. 1 and 2, a tension coil is provided between the through hole 34 formed in the one brake shoe 12 and the latching member 36 protruding from the inner peripheral portion of the backing plate 10. A spring 38 is stretched, and the tension coil spring 38 urges one brake shoe 12 (secondary shoe) toward the other brake shoe 14 (primary shoe). The tension coil spring 38 integrally includes a coil portion 40 and a pair of hooks 42 and 43 provided on both sides of the coil portion 40 in the axial direction, and the hook 42 as a whole is substantially U-shaped.
A straight portion 44 which is formed in a letter shape and protrudes from one end of the coil portion 40 in a direction parallel to the axis of the coil portion 40, a curved portion 46 which is curved at its tip, and a predetermined portion from the tip of the curved portion 46 It is composed of a straight portion 44 and a facing portion 48 that face each other and extend a distance. This predetermined distance is a distance that can prevent the tip of the facing portion 48 from being disengaged from the engagement hole 52, and is predetermined based on the inner diameter of the engagement hole 52 and the like.

The latch member 36, as shown in FIGS. 1 and 3,
The fixing portion 50 and the plate surface are formed so as to integrally project from the fixing portion 50 in a state in which the plate surface is substantially perpendicular to the backing plate 10 and is located in a direction intersecting the straight portion 44 of the hook 42 and the plate thickness direction. And a plate-like engaging portion 54 having an engaging hole 52 penetrating therethrough, the fixing portion 50 is fixed to the backing plate 10 by welding or the like, and the linear portion 44 of the hook 42 is engaged. The hook 42 is hooked so as to be located on the side of the fitting hole 52.

The drum brake assembly configured as described above is fixed to the non-rotating member of the vehicle at the inner peripheral portion of the backing plate 10, and the rotating drum (not shown) having a bottomed cylindrical shape has the inner peripheral surface thereof. Has brake shoes 1
By being rotatably provided on the non-rotating member in a state of facing the outer peripheral surfaces of 2, 14 with a slight gap, the duo servo type drum brake is assembled.
In FIG. 2, A indicates the direction of rotation of the rotary drum when the vehicle is moving forward. Further, since the operation of the duo servo type drum brake is not always necessary for understanding the present invention and is well known,
Detailed description thereof will be omitted.

Here, FIG. 6 is a view showing a main part of a conventional duo-servo type drum brake. In the following description, the same parts as those in the above-described embodiment are designated by the same reference numerals, and detailed description will be omitted. In the figure, the plate surface of the engaging portion 62 of the hooking member 60 is positioned substantially at right angles to the backing plate 10 and substantially parallel to the linear portion 44 of the hook 42, and the engaging portion 62 is Is formed with a notch 64 having a predetermined depth, which is opened in a direction away from the brake shoe 12 and on which the hook 42 is hooked. As a result, in the drum brake assembly before the rotary drum is assembled, the brake shoes 12 and 14 are moved together with the adjuster 20 toward the outer peripheral side of the brake shoe 14 with the anchor pin 22 as a substantially fulcrum, and the tension coil spring 38 causes the brake shoe 14 to move. When relatively moved to the side,
Although the tip of the facing portion 48 of the hook 42 has not yet passed the bottom of the notch 64, the bent portion 46 of the hook 42 has the notch 64.
In some cases, the hook 42 would stick out of the opening of the and the hook 42 would come off the notch 64.

On the other hand, according to the present embodiment, the engaging portion 54 of the locking member 36
Is provided with an engaging hole 52, the plate surface of the engaging portion 54 is positioned in a direction intersecting the linear portion 44 of the hook 42, and the linear portion 44 of the hook 42 is engaged with the engaging hole. Since the hook 42 is hooked so as to be positioned on the 52 side, even if the tension coil spring 38 moves along with the movement of the brake shoe 12 to the brake shoe 14 side,
Even if the hook 42 is moved relatively largely to the side, the hook 42 is effectively prevented from coming off the engaging hole 52.

Although the plate surface of the engaging portion 54 is positioned substantially at a right angle to the backing plate 10 in the above-described embodiment, this is not always necessary, and the engaging portion 54 is not necessarily at a right angle to the backing plate 10. If the plate surface is located in a direction intersecting the straight portion 44 of the hook 42, the same effect as that of the above-described embodiment can be obtained.

Also, in the above-described embodiment, the plate surface of the engaging portion 54 is a hook.
It is located in a direction intersecting with the straight portion of 42, but it is not always necessary, and the plate surface of the engaging portion 54 is hooked.
Even when the linear portion 44 of 42 is provided at a right angle or inclined by a predetermined angle, the coil portion of the tension coil spring 38 of the engaging portion 54, as shown in FIGS. 4 and 5, for example. Engagement hole 52 from the plate surface visible from the 40 side
By hooking the hook 42 on the hook 42, even if the hook 42 is relatively moved to the brake shoe 14 side, the hook 42 is prevented from coming off the engaging hole 52.

Also, in the above-described embodiment, the tension coil spring
38 is provided so as to urge the brake shoe 12 toward the brake shoe 14, but when the brake shoe 12 is the primary shoe and the brake shoe 14 is the secondary shoe, the brake shoe 14 is used. It will be provided so as to urge toward 12.

Further, in the above-described embodiment, the case where the present invention is applied to the duo servo type drum brake provided with only the parking brake mechanism has been described, but it is not always necessary, and only the service brake mechanism or both brake mechanisms is used. It goes without saying that the present invention can be applied to a duo servo type drum brake equipped with.

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 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. FIG. 3 is a front view showing the latch member of the present invention. 4 to 5 are views showing other examples of the present invention, respectively, showing essential parts. FIG. 6 is a diagram showing a main part of a conventional duo-servo type drum brake and is a diagram corresponding to FIG. 1. 10: Backing plate 12, 14: Brake shoe 20: Adjuster (coupling mechanism) 22: Anchor pin (anchor member) 36: Hook member 38: Tension coil spring 42: Hook 44: Straight part 46: Curved part 48: Opposed part 52: Engagement hole 54: Engagement part

Claims (1)

[Scope of utility model registration request] 1. A pair of brake shoes arranged on a backing plate so as to be capable of expanding each other, a connecting mechanism for connecting opposite ends of the brake shoes, and a fixing mechanism fixed on the backing plate, An anchor member that receives the braking torque transmitted to the brake shoe when the other end of the brake shoe is abutted, a straight portion, a curving portion that curls at its tip, and a tip of the curving portion. The hook has a substantially U-shaped hook that extends and faces the straight portion and that faces the hook, and the hook is hooked by a plate-shaped hook member provided on the backing plate. And a tension coil spring that is stretched between one of the brake shoes and urges the one brake shoe toward the other brake shoe. In the servo type drum brake, there is an engaging hole penetrating in the plate thickness direction where the hook is hooked, and the plate surface of the portion where the engaging hole is provided is positioned in a direction intersecting the longitudinal direction of the spring. The duo-servo type drum brake, wherein the engaging member is provided with the engaged member, and the spring is hooked on the engaging member so that the direct portion of the hook is located on the engaging hole side. .