JPH0710112Y2 - Drum brake - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a drum brake incorporating a parking brake.

(Prior Art) Some of the drum brakes have a built-in parking brake used during parking, and as this type of drum brake, there is a conventional one having a structure as shown in FIG. 4 to FIG. .

This is a leading / trailing type drum brake, and a back plate 3 with a pair of brake shoes (leading side brake shoe 1 and trailing side brake shoe 2) is fixed to a non-rotating part (not shown) of the vehicle. Has been done. Each brake shoe 1, 2 has a lining material 4, 5 on the outer circumference.
Are affixed respectively, and webs 1a and 2a are projected inside. Anchor 8 is fixed to rivet 7 on anchor mounting portion 6 protruding from the front side of back plate 3, and anchor 8 is composed of anchor body 8a and anchor plate 8b fixed to anchor body 8a. On the other hand, one end of each brake shoe 1, 2 is in sliding contact with the anchor body 8a.
The other ends of the brake shoes 1 and 2 are engaged with respective piston rods 11 and 12 of a wheel cylinder 10 having two pistons (one of which is not shown) 9. In addition, each brake shoe
Two return springs 13,1 that urge the brake shoes 1,2 in the direction of contracting (non-braking side) near both ends of 1,2.
4 is mounted. With this configuration, when hydraulic pressure is supplied to the wheel cylinders 10, the brake shoes 1 and 2 expand with the anchor 8 as a fulcrum. In addition, in the figure 15,16
Is a shoe hold spring, which is supported by shoe hold pins 17 and 18 erected on the back plate 3 to bias the brake shoes 1 and 2 toward the back plate 3.

A vehicle rotary shaft S such as an axle shaft penetrates through the center of the back plate 3, and a brake drum 19 is rotatably mounted around the shaft S together with wheels (wheels, not shown). The inner surface of the brake drum 19 has brake shoes 1,
Since the brake shoes 1 and 2 are located outside with a predetermined clearance, the brake shoes 1 and 2 are brought into pressure contact with the inner peripheral surface of the brake drum 19 to generate a braking force.

Next, the structure of the parking brake section will be described.
Struts 20 having an automatic adjusting mechanism for adjusting the clearance between the brake drums 1, 2 and 19 are suspended. One end of a parking lever 21 is rotatably attached to the other end of the trailing brake shoe 2, and the parking lever 21 is engaged with the strut 20. The other end of the parking lever 21 is connected to a parking brake lever in a vehicle compartment (not shown) via a cable 23 guided by a guide member 22. Parking lever
Between the 21 and the guide member 22, for returning the parking lever 21 to the original position, a return spring member 24 composed of a coil spring is inserted by inserting the cable 23,
When the parking lever 21 returns,
Positioning is performed by a protrusion 21a formed integrally with the 21.

With this configuration, when the parking brake lever is operated, the parking lever 21 rotates via the cable 23 and presses the strut 20 toward the leading side brake shoe 1 side to bring the leading side brake shoe 1 into pressure contact with the brake drum 19. The trailing brake shoe 2 is pressed against the brake drum 19 by the reaction force.

The automatic clearance adjustment mechanism, as shown in FIG.
Adjust screw on one rod 25 of strut 20
25a is provided, and the other rod 26 is provided with an adjusting gear 26a that meshes with the adjusting screw 25a so that the strut 20 can be extended by rotating the adjusting gear 26a.
An adjusting lever 28, which moves when the brake shoes 1 and 2 are expanded by 27 (shown in FIG. 7) and engages with the adjusting teeth formed on the outer periphery of the adjusting gear 26a to rotate, is provided. It is a thing.

(Problems to be solved by the invention) However, in a conventional drum brake incorporating a parking brake, a member (protrusion 21a in the above-mentioned conventional example) for restricting the return position of the parking lever 21 is provided. No member for restricting the maximum rotation position of the parking lever 21 is provided. Therefore, when the parking brake lever is pulled too hard, there is a risk that the parking lever 21 will rotate and hit the rotating shaft S as a shaft that penetrates through the center of the back plate 3, thus damaging the rotating shaft S. There was a problem that rust was generated and the parking lever 21 was bent, resulting in malfunction.

The present invention has been made in view of the above problems, and its purpose is to prevent damage to the shaft penetrating the center of the back plate and the parking lever by regulating the maximum rotation position of the parking lever. It is to regulate the drum brake.

(Means for Solving the Problems) A drum brake according to the present invention includes a back plate attached to a non-rotating portion of a vehicle, a pair of brake shoes attached to the back plate so as to be capable of expanding, and the back plate penetrating therethrough. A brake drum that is rotatably provided around the axis of the vehicle and that generates a braking force by expanding and pressing the brake shoe and the brake shoe via a cable by operating the parking brake lever. In a drum brake comprising a parking lever for expanding, a engaging portion provided at an end of the cable is engaged with the parking lever to form a connecting portion for connecting the cable to the parking lever. , The end of the connecting portion is extended to the side opposite to the direction in which the parking lever is pulled by the cable and rotates, and the tip is bent to the back plate side. In order to form a positioning portion, the back plate is provided with a stopper portion capable of slidingly contacting the parking lever at the time of rotation, and contacting the positioning portion to restrict the maximum rotation position. It is a feature.

Further, a back plate attached to a non-rotating portion of the vehicle, a pair of brake shoes attached to the back plate so as to be capable of expanding, and rotatably provided with a wheel around an axis passing through the back plate, A brake drum that generates a braking force by expanding and press-contacting the brake shoe, and a strut interposed between the pair of brake shoes,
With the parking lever pivotally supported on one of the brake shoes,
A drum brake comprising: a parking brake section that expands a brake shoe to generate a braking force by rotating the parking lever via a cable by operating a parking brake lever; A positioning portion is formed on the brake drum side of the brake shoe, and a stopper portion that abuts the parking lever to restrict the maximum rotation position of the parking lever is formed on the back plate. It is characterized in that it is arranged so as to be located between the parking lever and the back plate when not operating.

(Operation) With the positioning portion provided at the connection portion of the parking lever with the cable, when the parking lever is rotated, the positioning portion formed at the connection portion of the parking lever becomes the stopper portion provided on the back plate. Since the maximum rotation position of the parking lever is regulated by making contact with the parking lever, the parking lever does not rotate too much and hit the shaft penetrating the center of the back plate.

Further, in this case, the parking lever is pulled by the cable at a position farthest from the shaft-attached position, and therefore the parking lever may come close to the back plate side due to looseness of the shaft-attached portion or bending of the parking lever itself. By the sliding contact of the stopper portion, it is possible to prevent the parking lever from moving toward the back plate side, and it is possible to prevent the side portion of the parking lever from hitting the stopper portion before the positioning portion.

Further, since the positioning portion provided at the connection portion with the cable is brought into contact with the stopper portion to regulate the position, the reaction force applied from the stopper portion is greater than that in the case where other portions of the parking lever are brought into contact with the stopper portion to regulate the position. I need less power,
It is possible to prevent deformation of the parking lever.

In the case where the positioning portion is provided on the brake drum side of one brake shoe of the parking lever that is pivotally supported by the one brake shoe, when the parking lever is rotated, the connecting portion of the parking lever is similar to the operation of the above configuration. Since the positioning portion formed on the back plate comes into contact with the stopper portion provided on the back plate to limit the maximum rotation position of the parking lever, the parking lever may rotate too much and hit the shaft penetrating the center of the back plate. Disappear.

Further, since the contact surface of the stopper portion is always located between the parking lever and the back plate, the parking lever is guided between one of the brake shoes and the stopper portion, so that the parking lever does not bend when rotating. Even if the above occurs, the parking brake can be reliably operated.

Next, an embodiment of the present invention will be described with reference to the drawings. In this embodiment, the same or corresponding members as those of the conventional drum brake shown in FIGS. 4 to 6 are designated by the same reference numerals and detailed description thereof will be omitted.

A connecting portion 29 provided at the end of the cable 23 engages with the tip of the parking lever 21 on the side opposite to the side where the brake shoe 2 is attached to the shaft, and is bent in a U shape for connecting the cable 23. The connected portion 21b is formed. Connection 2
A positioning portion 21c is formed at the end of 1b. The parking lever 21 extends in the direction opposite to the direction in which the parking lever 21 is pulled by the cable 23, and the front end is bent to extend to the back plate 3 side.

On the other hand, when the parking lever 21 rotates, the back plate 3 comes into contact with the positioning portion 21c before hitting the rotation axis S as a shaft passing through the center of the back plate 3, and the rotation of the parking lever 21 is stopped. Further, when the parking lever 21 rotates, the stopper portion 30 is attached to a position where the flat surface of the parking lever 21 on the side of the back plate 3 can always slide. This is the positioning part of the parking lever 21.
By extending 21c to the side opposite to the rotation direction, a predetermined rotation stroke can be secured while the parking lever 21 is always in slidable contact with the stopper portion 30.

The stopper portion 30 has a structure in which the block is fixed to the back plate 3 by welding, but even in the structure in which the block is fixed by a screw or the like, the hexagonal portion of the nut or bolt is used as the stopper portion 30.
The structure may be Or the back plate 3 by squeezing
It is also possible to have a structure in which they are integrally provided.

With the above configuration, even if the parking brake lever is pulled too much, the positioning portion 21c formed on the connection portion 21b of the parking lever 21 comes into contact with the stopper portion 30 provided on the back plate 3 to restrict the rotation of the parking lever 21. Therefore, it does not hit the rotation axis S as an axis passing through the center of the back plate 3,
The rotating shaft S is not damaged, and the parking lever 21 is not bent, so that malfunction does not occur.

Further, since the parking lever 21 is pulled by the cable 23 at the position farthest from the shaft mounting position, when the loosening of the shaft mounting part or the bending of the parking lever 21 itself occurs, the parking lever 21 is backed by the web 2a of the brake shoe 2. Since the deformation on the side away from the plate 3 is suppressed, it may come close to the back plate 3 side, but even if the parking lever 21 approaches the back plate 3 side during rotation, it is pressed by sliding contact with the stopper portion 30, Therefore, it is possible to prevent the side portion 21d of the parking lever 21 from hitting the stopper portion 30 before the positioning portion 21c and limiting the rotation stroke, which prevents the parking brake from functioning.

In the present embodiment, the present invention is applied to the drum brake in which the pair of brake shoes 1 and 2 are mounted so as to be expandable and contractable by the fixed anchor 8. However, the present invention is not limited to this. Instead, any type of drum brake can be applied as long as the drum brake incorporates a parking brake that operates a parking lever by a cable.

(Effects of the Invention) As described in detail above, the positioning portion is formed in the connection portion for connecting the cable of the parking lever of the present invention, and the back plate is provided with the stopper portion capable of sliding contact with the parking lever. The maximum rotation position of the parking lever can be regulated by contacting the stopper part with the stopper part, and the parking lever hits the rotation shaft as a shaft that penetrates through the center of the back plate to damage the rotation shaft or bend the parking lever. It is possible to prevent a malfunction from occurring due to a failure.

Further, when the parking lever is rotated, it is possible to prevent the parking lever from being closer to the back plate side, so that the parking lever can move smoothly and malfunction of the parking brake can be prevented.

Further, since the positioning portion provided at the connecting portion with the cable is brought into contact with the stopper portion provided on the back plate to regulate the maximum rotation position, other portions of the parking lever are brought into contact with the stopper portion to be regulated. The force applied from the stopper portion is smaller than that in the case where the parking lever is deformed and the parking lever can be prevented from being deformed or damaged.

A positioning portion is provided on the brake drum side of one brake shoe of one of the parking levers pivotally supported by one brake shoe, and the contact surface with the parking lever is positioned between the parking lever and the back plate when the back plate is not operating. In the case where the stopper portion is provided in the same manner as above, the maximum rotation position of the parking lever can be regulated by the positioning portion coming into contact with the stopper portion, and the rotation of the parking lever as a shaft passing through the center of the back plate. It is possible to prevent the rotary shaft from being damaged by hitting the shaft, and to prevent the parking lever from bending and causing malfunction, and at the same time, the parking lever is always guided between one brake shoe and the stopper part. Therefore, the operation of the parking lever becomes reliable, and the reliability of the parking brake can be improved. That.

[Brief description of drawings]

FIG. 1 is a front view showing an embodiment of the drum brake of the present invention, FIG. 2 is a sectional view taken along line II-II of FIG. 1, and FIG. 3 is (a), (b), (c). ) Is a diagram showing the parking lever shown in Fig. 1, Fig. 3 (a) is a front view of the parking lever, Fig. 3 (b) is a right side view of Fig. 3 (a), FIG. 3 (c) shows II of FIG. 3 (a).
4 is a sectional view of a conventional drum brake (IV in FIG. 5).
-IV line sectional view), FIG. 5 is a front view of the conventional drum brake shown in FIG. 4, and FIG. 6 is a VI-VI line sectional view of FIG. 1,2 …… Brake shoe 3 …… Back plate 21 …… Parking lever 21b …… Connecting part 21c …… Positioning part 23 …… Cable 30 …… Stopper part

Claims (2)

[Scope of utility model registration request] 1. A back plate attached to a non-rotating portion of a vehicle, a pair of brake shoes mounted to the back plate so as to be capable of expanding, and rotatable with a wheel around an axis passing through the back plate. A brake drum that is provided and that generates a braking force by expanding and pressing the brake shoe; and a parking lever that expands the brake shoe via a cable by operating a parking brake lever. In the drum brake, at the connection portion of the parking lever with the cable, a positioning portion is provided that extends to the side opposite to the direction in which the parking lever is pulled by the cable and rotates, and has the tip bent to extend to the back plate side. The parking lever is slidably contactable with the back plate during rotation, and the positioning portion is in contact with the back plate to regulate the maximum rotation position of the parking lever. Drum brake characterized in that a stopper portion of the order. 2. A back plate attached to a non-rotating portion of a vehicle, a pair of brake shoes mounted to the back plate so as to be capable of expanding, and rotatable with a wheel around an axis passing through the back plate. A brake drum that is provided to generate a braking force by expanding and pressing the brake shoe, and a strut interposed between the pair of brake shoes,
With the parking lever pivotally supported on one of the brake shoes,
A drum brake comprising: a parking brake section that expands a brake shoe to generate a braking force by rotating the parking lever via a cable by operating a parking brake lever; A positioning portion is formed on the brake drum side of the brake shoe, and a stopper portion that abuts the parking lever to restrict the maximum rotation position of the parking lever is formed on the back plate. A drum brake characterized by being arranged so as to be located between the parking lever and the back plate when not operating.