JPS587145Y2 - Drum brake air gap automatic adjustment device - Google Patents

Description

[Detailed description of the invention] The present invention is an automatic gap adjustment device for drum brakes that automatically adjusts the gap (gap) between the drum and brake lining of drum brakes used in vehicles such as automobiles. Regarding.

Drum brakes have brake shoes that are pivoted on the inside of a drum that rotates with the wheels, one end of which is pivotally connected to a back plate, and the other end of which faces a cam or hydraulic cylinder mechanism. Many brake shoes are provided with a spring biased in the direction (direction), and when the brake shoes are expanded, the frictional force generated by contact with the inner circumference of the drum generates braking force on the wheels via the drum. It is used.

In fact, II also has a pressure contact member called a brake lining attached to the part of the brake shoe that faces the inner periphery of the drum to obtain an appropriate amount of frictional force between it and the brake drum and to prevent the drum from wearing out. is normal.

When the brake lining wears out during use, the position of the brake shoe is moved toward the drum in small increments to adjust the gap between the brake lining and the inner circumference of the drum. When this happens, you will need to replace the brake lining with a new one.

In this case, the above-mentioned gap is automatically adjusted using a hydraulic drum brake that expands the brake shoes using hydraulic pressure, so that a constant gap size can always be obtained until the brake lining wears out to the point that it needs to be replaced. Various devices have been proposed, but to date, very few mechanical drum brakes have been proposed, which have a relatively simple structure and use a cam to widen one end of the brake shoe. there were.

The present invention has been devised in view of this point, and is intended to provide an automatic air gap adjustment device for a mechanical drum brake that operates reliably with a simple configuration.

The basic structure of the present invention is that a brake shoe is placed opposite to the inside of a drum that rotates with the wheels, with one end pivotally connected to the back plate and the other end facing a cam that rotates in conjunction with the brake lever. In a drum brake which is provided with a spring bias in a direction close to each other and obtains braking force by coming into contact with the inner circumference of the drum when the brake shoes are expanded, the brake shoes facing the brake shoes of the cam are provided. The edge part is formed flat, and the part of the brake shoe facing the cam is screwed with a bolt whose head is flat and has many serrated teeth on its outer circumference. The above-mentioned claw plate is brought into contact with the cam, and near the cam (approximately at the center of the claw plate, which has a claw on one east end that elastically contacts the teeth of the bolt head and has an engaging portion on the other end). In the upright part that stands up from the back plate in a direction parallel to the axle,
The bolt is rotatably supported in a direction perpendicular to the bolt, and an engaging part provided on the other end of the claw plate and an engaging part provided on the camshaft have an engaging hole in one of them and an engaging hole in the other. By providing a protruding piece narrower than the engagement hole and engaging the retaining hole with the protruding piece, the pawl plate is coupled to the camshaft with a slight play in the rotating direction of the camshaft, A drum brake gap characterized in that when the play is absorbed, the rotation of the camshaft operates the pawl plate such that the pawl of the pawl plate rotates the bolt. It is an automatic adjustment device.

Hereinafter, one embodiment of the present invention will be described. In FIG. 1, reference numeral 1 denotes a drum, which rotates together with a wheel (not shown) attached to an axle 2.

3 is a back plate, which is a member on the two vehicle body side and does not rotate.

Brake shoes 4 and 5 are half-moon shaped and are disposed facing each other with their backs facing the inner circumference of the drum 1.

Brake lining 6 is on the back side of brake shoe 4°5.
．． 7 is attached so that a slight gap is formed between it and the inner peripheral portion of the drum 1.

An anchor pin 8 is installed in the back plate 3 in parallel with the axle 2, and the lower ends of the brake shoes 4, 5 are pivotally connected to the anchor pin 8.

This allows the brake shoes 4 and 5 to rotate around the anchor pin 8 as a fulcrum.

Return springs 9 and 10 are stretched between the opposing brake shoes 4 and 5, and these brake shoes 4 and
5 are biased toward each other.

11 is a cam.

As shown in FIG. 2, the cam 11 is formed at the upper end of the camshaft 12, and has a flat plate shape on both sides.

The camshaft 12 is provided with a large diameter section 13.14, and the above-mentioned back plate 3 is connected to the large diameter section 13.14.
It penetrates through and is rotatably supported (see Fig. 4).

A spline groove 15, 16 is cut into the lower end of the camshaft 12, and a spline groove 15, 16 is cut into the lower end of the camshaft 12.
7 (see Figure 1).

Parts of brake shoes 4 and 5 facing cam 11 (upper end)
A bolt 20, 21 having a flat eastern head and a large number of serrated teeth 18, 19 on its outer periphery is screwed into the bolt 20, 21, and its head abuts against the cam 11.

With this structure, when the cam 11 rotates, the bolt 20,
21, the upper ends of the brake shoes 4, 5 are pushed apart from each other, rotate about the anchor pin 8, and press the brake lining 6.7 against the inner circumference of the drum 1.

As shown in FIGS. 1 and 4, the back plate 3 is provided with an upright portion 22 extending parallel to the axle 2, and a pawl plate 23 is rotatably supported here by screws 24. .

Thereby, the screw 24 becomes the pivot of the claw plate 23.

Reference numeral 25 shown in FIG. 3 is a hole for screw insertion.

A coil spring 26 is provided between the claw plate 23 and the upright portion 22.
is interposed so as to press the claw plate 23 toward the cam 11 side.

With this structure, the pawl plate 23 is rotatably supported around the screw 24 in a direction perpendicular to the bolts 20 and 21, and is always pressed toward the cam 11.

As shown in FIGS. 1, 3 and 4, the claw plate 23 has claws 27.2 facing the teeth 18.19 of the head of the nail plate 20.21.
8 is provided.

These pawls 27 and 28 come into elastic contact with the teeth 18 and 19, respectively, because the pawl plate 23 is pressed in the direction of the cam 11 by the coil spring 26, as described above.

Therefore, when the cam plate 23 rotates by a certain angle or more about the screw 24, the teeth 18.19 are rotated by the pawl 27.28.
The pawls 20, 21 are rotated, and the pawls 27, 2B of the pawl plate 23, which protrude from the inside of the brake shoes 4, 5, are moved by the teeth 18, 19 (see Fig. 5). As a means for making elastic contact, instead of using the coil spring 26,
The claw plate 23 itself may be constructed of a leaf spring, and its elastic force may be utilized.

The pawl plate 23 and the camshaft 12 are connected with a slight clearance provided by the following structure.

That is, in this embodiment, a protruding piece 29 having a width W1 is provided on the camshaft 12 side, and a protruding piece 29 having a width W1 provided on the claw plate 23 is provided.
2 (slightly wider than the width Wt) of the engagement hole 30.

In this case, when the cam 11 does not rotate and is not braking, the protrusion 2
9 is set to be located at the center of the engagement hole 30.

With this structure, when the camshaft 12 rotates over a certain angle,
The protruding piece 29 touches one edge of the engagement hole 30, and the claw plate 23 is secured to the screw 2.
It will rotate around 4.

Note that the difference between the widths Wl and W2 corresponds to the initial setting value of the gap width between the drum 1 and the brake lining 6.7.

Next, the operation of this device configured as described above will be explained.

When lever 17 is rotated counterclockwise in FIG. 1 by operating a brake pedal or a brake lever (none of which are shown), camshaft 12 connected to this lever 11 is rotated in the same direction. And the cam 1 that is integrated with this
1 in the counterclockwise direction in FIG. 1 (in the direction of the arrow in FIG. 2).

As a result, the bolts 2Q, 21 whose heads are in contact with the cam 11 are pushed left and right, so the brake shoes 4,
5 is pushed open to the left and right using the anchor pin /8 as a fulcrum, and the brake lining 6.7 comes into pressure contact with the inner peripheral portion of the drum 1 to perform a braking action.

When the brake is released, the brake shoes 4 and 5 are returned to their original positions by the return springs 9 and 10.

When the brake lining becomes worn as a result of long-term use, the amount of movement of the brake shoes 4 and 5 becomes large (
Become.

That is, the gap width between the drum 1 and the brake lining 6.7 becomes larger than the initial setting value.

In this case, since the camshaft 12 rotates by more than a certain angle in the direction of the arrow in FIG. The cam plate 23 is rotated counterclockwise in FIG. 3 using the screw 24 as a fulcrum.

This causes the pawl 27 to slide over the teeth 18 and the pawl 28 to slide over the teeth 19.

When this amount of sliding exceeds a certain value, the pawls 27 and 28 advance by one tooth of the teeth 18 and 19 and engage with the next tooth 18 and 19.

When the brake pedal or brake lever is released in this state, the brake shoes 4 and 5 are moved by the return spring 9.
The claws 27 and 28 of the claw plate 23 return to the direction where they are close to each other with a force of °·10, but at this time the claws 27 and 28 of the claw plate 23 return with the teeth that were engaged when the claw plate 23 rotated, and the bolt 20.2
1 is rotated by a certain amount to make it protrude from the brake shoes 4 and 5, and the gap between the inner peripheral part of the drum 1 and the brake lining 6.7 is maintained at a constant value.

Thereafter, each time the wear degree of the brake lining 6°7 exceeds a certain value (each time the protrusion 29 rotates the pawl plate 23)
, the gap is automatically adjusted.

FIG. 6 shows another embodiment of the present invention.

In this case, in order to connect the pawl plate 23 and the camshaft 12 with some play, a ring 3γ having a circumferential elongated hole 36 formed in a part of the camshaft 12 is fitted. A projecting piece 38 having a width W6 smaller than the width W5 of the elongated hole 360 provided at one end of the claw plate 23 is loosely fitted into the elongated hole 36 of the ring 3T.

This embodiment remains the same in operation, but is easier to assemble.

FIG. 7 shows yet another embodiment of the present invention.

In this case, bolts 20°2 are attached to the brake shoes 4 and 5.
Leaf springs 39 and 40 for preventing reverse rotation are provided, and their tips are brought into contact with the teeth 18 and 19 of the bolts 20 and 21.

This prevents the bolts 20, 21 from reversing when the pawls 27.28 ride over the teeth 18.19.

Since the present invention is constructed as described above, although it has an extremely simple construction, it is effective in operating reliably and adjusting the gap between the drum and the brake lining when the brake lining wears out. be.

[Brief explanation of the drawing]

Fig. 1 is a front view of an embodiment of the present invention, Fig. 2 is a perspective view of the camshaft portion in Fig. 1, Fig. 3 is a perspective view of the main part of Fig. 1, and Fig. 4 is a perspective view of the main part of Fig. 1. FIG. 1 is a cross-sectional view taken along line IV-N in FIG. 1, FIG. 5 is an enlarged view explaining the action of the claws and teeth, FIG. FIG. 7 is a plan view of a main part of still another embodiment. 1...Drum, 2...Axle, 3...
... Back plate, 4,5... Brake shoe, 6.7... Brake lining, 8...
...Anchor pin, 9゜10...Return spring, 11...Cam, 12...
Camshaft, 17... Lever, 18, 19...
...Teeth, 20, 21...Bolt, 22...
... Standing part, 23 ... Nail plate, 24 ...
Screw, 25...-TL, 26...Coil spring, 27, 28...Claw, 29°38.
...Protruding piece, 30...Engagement hole, 36...
...Long hole, 37...Ring.

Claims (1)

[Scope of utility model registration request] On the inside of the drum that rotates with the wheels, there are brake shoes with one end pivoted to the back plate and the other end facing the cam that rotates in conjunction with the brake lever, with springs attached in the direction of approaching each other. In the drum brake, the part of the cam facing the brake shoe is formed flat in the drum brake, which is provided so as to obtain braking force by contacting the inner peripheral part of the drum when the brake shoe is expanded. At the same time, a bolt with a flat head and a large number of serrated teeth on the outer periphery is screwed into the part of the brake shoe facing the cam, and the bolt is brought into contact with the cam.
On the other hand, in the vicinity of the cam, there is a pawl plate (having a pawl at one end that comes into elastic contact with the teeth of the bolt head and a retaining portion at the other end), and the axle is connected to the axle from the back plate at approximately the center of the pawl plate. These bolts are supported rotatably in a direction perpendicular to the bolt on an upright part that stands up in a parallel direction, and are attached to a retaining part provided at the other end of the claw plate and an engaging part provided to the camshaft. By providing an engagement hole on one side and a protrusion narrower than the hole on the other, and engaging the engagement hole and the protrusion, the pawl plate can be attached to the camshaft in the rotational direction of the camshaft. are engaged with each other with some play, and when the play is absorbed, the rotation of the camshaft operates the pawl plate, and the pawl of the pawl plate rotates the bolt. This is an automatic air gap adjustment device for drum brakes.