JPH0874902A - Automatic clearance adjusting device for drum brake - Google Patents

Abstract

PURPOSE: To reduce number of part items and facilitate assembling work by increasing rigidity of an intermediate part of a adjusting link made of a spring plate and also allowing a connecting part with an anchor turning with the anchor but inhibiting movement in longitudinal direction of the adjusting link. CONSTITUTION: An anchor 4 and an anchor side end part 17b of an adjusting lever 17 are connected to each other with an adjusting link 18 made of a spring plate. The connection increases rigidity of an intermediate part 18a of the adjusting link 18 and also allows a connecting part 18b with the anchor 4 to be turned with the anchor 4 but inhibits it moving to longitudinal direction of the adjusting link 18. A spring part 18d elastically holding an anchor side end part 17b of the adjusting lever 17 while allowing elastic deformation of the holding part is formed in the connecting part 18c of the adjusting lever 17. Whereby, number of part items is reduced and assembling workability can be improved. Dislocation of the adjusting link 18 from the adjusting lever 17 can be prevented assuredly.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drum brake automatic gap adjusting device for automatically adjusting a gap between a brake drum and a brake shoe in a drum brake.

[0002]

2. Description of the Related Art As a conventional device of this type, for example, there is an automatic shoe clearance adjusting device for a drum brake disclosed in Japanese Utility Model Publication No. 2-17225. This device includes the other end 12c of the adjust lever 12 and a fixing member (anchor).
5 and the link 13 interposed between the adjusting lever 1 and
The other end 12c of 2 and the fixing member 5 are respectively hooked and stretched, and an adjusting spring 18 for urging the link 13 against the fixing member 5 is provided.

[0003]

The above-mentioned conventional device has a problem that the number of parts is large and the assembling and dismounting work becomes complicated, and the engaging of the adjusting lever 12, the link 13 and the adjusting spring 18 is difficult. It is unstable and may come off due to operation or vibration.
There is a problem that the engagement is easily disengaged with respect to the acting force in the direction orthogonal to the axial direction of.

[0004]

In order to solve the above-mentioned problems, in the present invention, the upper ends of a pair of brake shoes abut on an anchor fixed to a back plate,
One end of the adjusting lever is rotatably attached to one of a pair of brake shoes whose lower ends are connected via an adjuster so as to pivotally support an intermediate portion of a substantially V-shaped adjusting lever. By engaging the toothed wheel and rotating the adjusting lever in response to the movement of the brake shoe, the toothed wheel of the adjuster is rotated to extend the adjuster and adjust the clearance between the drum and the brake shoe. In the automatic gap adjusting device described above, the rigidity of the intermediate portion of the adjustment link made of a spring plate that connects the anchor and the anchor-side end portion of the adjustment lever is increased, and the connection portion with the anchor is connected to the anchor. Allows rotation but does not move in the longitudinal direction of the adjustment link, elastically grips the adjustment lever at the connection with the adjustment lever, and allows elastic deformation of the grip. Forming a spring portion constituting a clearance automatic adjustment device of the drum brake.

[0005]

Since the present invention is constructed as described above, instead of the link 13 and the adjusting spring 18 of the conventional device,
One adjustment link is enough. Therefore, according to the present invention, the number of parts is reduced and the assembling workability is also improved. Further, in the present invention, since the adjusting lever is elastically gripped at the connecting portion of the adjusting link with the adjusting lever, and the spring portion that allows the elastic deformation of the gripping portion is formed,
It is possible to reliably prevent the adjustment link from coming off the adjustment lever.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In the figure, 1 is a back plate mounted on a stationary portion of a vehicle, 2 and 3 are a pair of brake shoes, 4 is an anchor projecting from the back plate 1 between the upper ends of the brake shoes 2 and 3, and 5 is a brake shoe. A wheel cylinder provided inside the anchor 4 between the upper ends of 2, 3 is a strut similarly provided inside the wheel cylinder 5 between the upper ends of the brake shoes 2, 3, and 7 is a brake shoe 2 and the anchor 4. A shoe return spring stretched between the brake shoe 3 and the anchor 4 is provided between the brake shoe 3 and the anchor 4.

Further, 9 is a shoe holding pin fixed to the back plate 1 for holding the brake shoes 2 and 3 so as to be freely movable in a certain range, 10 is a shoe holding spring, and 11 is interposed between the lower ends of the brake shoes 2 and 3. The adjuster inserted, 12 is a toothed wheel thereof, 13 is a shoe return spring stretched between the lower ends of the brake shoes 2 and 3, 14 is a brake lever whose upper end is pivotally supported on the brake shoe 2 by a pin 15, and 16 is its Cable connected to the lower end of the brake lever 14, 1
Reference numeral 7 is a substantially V-shaped adjusting lever having an intermediate portion pivotally supported by a shoe holding pin 9, the lower end 17a of which is engaged with the toothed wheel 12 of the adjuster 11.

In this embodiment, the anchor 4 and the anchor side end 17b of the adjusting lever 17 are connected by an adjusting link 18 made of a spring plate. The connection method is such that the rigidity of the intermediate portion 18a of the adjustment link 18 is increased and the connection portion 18b with the anchor 4 is allowed to rotate with the anchor 4 but is not moved in the longitudinal direction of the adjustment link 18 for adjustment. The connecting portion 18c with the lever 17 is provided with a spring portion 18d that elastically grips the anchor-side end portion 17b of the adjusting lever 17 and allows elastic deformation of the grip portion.

More specifically with reference to FIGS. 2 and 3, the adjusting link 18 is formed of a spring plate as a material into a substantially rectangular shape, and a ridge 18e is provided at an intermediate portion 18a thereof, and the rigidity of the intermediate portion 18a is provided. By increasing, the adjustment link 18 can achieve the function of a stopper that regulates the distance between both connecting portions. Also, the connecting portion 1 with the anchor 4
8b is a head 4 of the anchor 4 adjacent to the ridge 18e.
A hole 18f into which a can be inserted is provided, and both side edge portions 18g are recessed by an amount corresponding to the thickness of the head portion 4a of the anchor 4, as shown in FIG.

A slot 1 having a width that allows the lower neck portion 4b of the anchor 4 to be fitted from the hole 18f toward the connecting portion 18b.
8h is provided, and when the anchor 4 is located at the outer end of the groove hole 18h, a spring piece 18j having a locking piece 18i that engages with the outer peripheral surface of the head 4a of the anchor 4 is provided between the hole 18f and the groove hole 18h. It is installed by extending it to the center.

The connecting portion 17b of the adjusting lever 17 with the adjusting link 18 is bent at a right angle to the main body of the adjusting lever 17, and as shown in FIG.
Recessed portions 17c are provided on both sides of the connecting portion with. A long hole 18k is provided in the connecting portion 18c of the adjusting link 18 with the adjusting lever 17, and both side edges of the long hole 18k are bent into a continuous waveform to form a spring portion 18d.

In order to attach the adjustment link 18 formed as described above, first, as shown by the chain double-dashed line in FIG. 3, the head 4a of the anchor 4 is inserted into the hole 18f, and then the adjustment link 18 is inserted into the hole shown in FIG. If the anchor 4 reaches the position shown by the solid line and the locking piece 18i engages with the outer peripheral surface of the head 4a of the anchor 4 by pushing it downward in the direction of arrow A in FIG. On the other hand, the adjustment link 18 can rotate, but cannot move in the longitudinal direction of the adjustment link 18.

To connect the adjusting link 18 to the adjusting lever 17, the spring portion 18d is extended and the elongated hole 18k is formed.
Is hooked on the connecting portion 17b of the adjusting lever 17. In this way, the spring portion 18d contracts, and both ends of the elongated hole 18k come into pressure contact with the recessed portions 17c on both sides of the connecting portion 17b of the adjusting lever 17, respectively, so that the adjusting link 18 moves.
While elastically gripping the connecting portion 17b of No. 7, the spring portion 18d of the adjusting link 18 allows elastic deformation of the gripping portion.

Next, the automatic gap adjusting operation of the apparatus of the present invention constructed as described above will be explained. First, when a brake pedal (not shown) is depressed, hydraulic pressure is generated in the wheel cylinder 5, the brake shoes 2 and 3 are opened, and the respective linings are pressed against a brake drum (not shown). At that time, when the brake drum is rotating in the direction of arrow B in FIG. 1, the upper end of the brake shoe 3 hits the anchor 4 to generate a braking force, and at the same time, the adjusting link 18 and the adjusting lever 1
Since 7 and the brake shoe 3 and the adjuster 11 rotate almost integrally with the anchor 4, the relative position between the toothed wheel 12 of the adjuster 11 and the lower end 17a of the adjusting lever 17 does not substantially change and the adjuster 11 extends. No adjustment is made.

Next, when the brake is operated while the brake drum is rotating in the direction of arrow C in FIG. 1, the brake shoe 3 and the adjusting lever 17 move in a direction away from the anchor 4, and the upper end of the brake shoe 2 is moved to the anchor 4. Generates braking force by hitting. At that time, since the substantial connection length of the adjustment link 18 does not change, the adjustment lever 17 is elastically connected to the adjustment link 18, and the shoe holding pin 9
It rotates counterclockwise in FIG. Therefore, the amount of movement of the lower end 17a of the adjusting lever 17 depends on the tooth wheel 12
If it is larger than the pitch, the lower end 17a of the brake release adjustment lever 17 engages with a new tooth of the toothed wheel 12. However, at the time of the next brake operation, new teeth are rotated, and the adjuster 11 is extended by the amount corresponding to the rotation to close the gap between the brake drum and the linings of the brake shoes 2 and 3.

Further, the frictional force of the brake shoe 3 is transmitted to the brake shoe 2 via the adjuster 11, and both shoes 2 and 3 come into contact with the brake drum to cause the adjuster 11 to move.
When the thrust force of the adjuster 11 increases, the surface pressure of the screw part increases and the torque for rotating the screw part of the adjuster 11 rapidly increases. At this time, the connecting part between the adjusting lever 17 and the adjusting link 18 is increased. The spring portion 18d of the adjusting lever 17 bends and the anchor side end portion 17b of the adjusting lever 17 and the connecting portion 18c of the adjusting link 18 are separated from each other, and the adjusting lever 17 and the adjusting link 1
Since it absorbs the differential between 8 and 8, it does not damage the self-adjusting parts.

[0017]

Since the present invention is constructed as described above, one adjusting link 18 is sufficient instead of the link and adjusting spring of the conventional device. Therefore, according to the present invention, the number of parts is reduced and the assembling workability is also improved. Further, in the present invention, since the adjusting lever 17 is elastically gripped at the connecting portion 18c of the adjusting link 18 with the adjusting lever 17, and the spring portion 18d for allowing the elastic deformation of the gripping portion is formed, the adjusting link The effect that it is possible to surely prevent 18 from coming off from the adjusting lever 17 is obtained.

[Brief description of drawings]

FIG. 1 is a front view of a drum brake equipped with the device of the present invention.

FIG. 2 is a front view of an adjustment link of the device of the present invention.

FIG. 3 is a bottom view of FIG.

[Explanation of symbols]

 1 Back Plate 2,3 Brake Shoe 4 Anchor 4a Head 4b Lower Neck 5 Wheel Cylinder 6 Strut 7,8 Shoe Return Spring 9 Shoe Holding Pin 10 Shoe Holding Spring 11 Adjuster 12 Teeth 13 Shoe Return Spring 14 Brake Lever 15 Pin 16 Cable 17 Adjusting lever 17a Lower end 17b Anchor side end 18 Adjusting link 18a Intermediate part 18b Connecting part 18c Connecting part 18d Spring part 18e Projection 18f hole 18g Both side edges 18h Groove hole 18i Locking piece 18j Spring piece 18k Long hole

Claims (1)

[Claims] 1. A pair of brake shoes, each upper end of which is in contact with an anchor fixed to a back plate, and one of a pair of brake shoes whose lower ends are connected to each other through an adjuster. By pivotally supporting the intermediate part of the adjusting lever of, the one end of the adjusting lever is engaged with the toothed wheel of the adjuster, and the adjusting lever rotates in response to the movement of the brake shoe. In an automatic clearance adjusting device that adjusts a clearance between a drum and a brake shoe by rotating a toothed wheel of the adjuster to extend the adjuster, the anchor is connected to an anchor side end portion of the adjustment lever. Increase the rigidity of the intermediate part of the spring plate adjustment link, and allow rotation of the connection part with the anchor with the anchor but do not move in the longitudinal direction of the adjustment link. An automatic gap adjusting device for a drum brake, characterized in that a spring portion which elastically grips the adjusting lever and allows elastic deformation of the gripping portion is formed at a connecting portion with the adjusting lever.