JPH0240334Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a drum brake that includes an arcuate brake shoe and a brake drum, and a wheel cylinder is provided at one end in the length direction of the brake shoe.

(Prior art) Generally, this type of drum brake has a pair of arc-shaped brake shoes on the inner surface of a back plate surrounded by a brake drum, as shown in, for example, Japanese Utility Model Application Publication No. 59-34128. Place it and
A wheel cylinder is provided at one lengthwise end of the brake shoe, and the other lengthwise end of the brake shoe is supported by an anchor fixed to the back plate, and when the wheel cylinder operates,
Braking is achieved by swinging the brake shoe in the direction of diameter expansion using the anchor as a fulcrum and bringing it into pressure contact with the inner circumferential surface of the brake drum.

(Problem to be Solved by the Invention) In the case of the drum brake described above, the change in braking force with respect to the input to the brake shoe is, as shown in FIG. Therefore, when braking, for example, when the brake pedal is depressed, the brakes may be applied more forcefully than expected by the driver.

This invention was developed in view of the above circumstances.
It is an object of the present invention to provide a drum brake in which the change in braking force generated by the input to the brake shoe can be made non-linear.

That is, in this type of drum brake, there are various factors that determine the braking force, one of which is the distance between the center point of the brake drum and the support point of the brake shoe relative to the anchor.
The present invention focuses on the principle that as this distance becomes shorter, the braking force generated during braking increases.

(Means for Solving the Problems) In order to achieve the above object, the present invention is provided with an arc-shaped brake shoe and a brake drum, and a drum having a wheel cylinder provided at one end in the length direction of the brake shoe. In the brake, at least one first anchor is provided at an intermediate portion in the length direction of the brake shoe, and a second anchor is provided at the other end side in the length direction of the brake shoe, and the first anchor is connected to the a gap between the second anchor and the brake shoe that allows the brake shoe to swing about the first anchor while supporting the brake shoe so as to be elastically displaceable at a detached position apart from the brake shoe; was established.

(Function) According to the present invention, when the input to the brake shoe is low, the brake shoe
Since it swings using the anchor as a fulcrum, the change in braking force in response to the input is large, and from the time the input to the brake shoe exceeds a set value, it swings using the second anchor as a fulcrum. The change in the braking force with respect to the input becomes smaller than the previous trend.

(Embodiment) An embodiment of the drum brake according to the present invention will be described below based on the drawings.

In the figure, 1 is a back plate fixed to the axle,
Reference numeral 2 denotes a brake drum disposed so as to rotate freely relative to the back plate 1, and a wheel cylinder 3 is attached to the upper part of the inner surface of the back plate 1 surrounded by the brake drum 2. A brake shoe 4 having an arc shape and a T-shaped cross section is arranged in the brake shoe 4.
One lengthwise end of the wheel cylinder 3 is brought into contact with the operating portion of the wheel cylinder 3.

Further, a first anchor 5 is provided at a longitudinally intermediate portion of each brake shoe 4, and the first anchor 5 is supported so as to be elastically displaceable to a detached position with respect to the brake shoe 4.

Specifically, while a rectangular through hole 41 is formed in the longitudinally intermediate portion of the brake shoe 4,
The inner surface of the back plate 1 and the through hole 4
A pair of opposing support plates 1 at positions opposite to 1.
1 and 11 are provided at a predetermined interval, and the support plate 1
The first anchor 5 is swingably supported on a pivot shaft 12 installed between 1 and 11, and one end of the first anchor 5 projects into the through hole 41.

Further, a lock ball 50 is attached to the first anchor 5.
Forms a fitting groove 51 into which the fitting groove 51 can be fitted.
A spring 52 is interposed between the lock ball 50 that fits into the back plate 1 and the back plate 1 to urge the lock ball 50 toward the first anchor 5 and restrict the swinging of the first anchor 5. If the input from the wheel cylinder 3 to the brake shoe 4 is less than a predetermined value,
The spring force of the spring 52 overcomes the input, so that the brake shoe 4
While swinging with the first anchor 5 as a fulcrum, when the input from the wheel cylinder 3 to the brake shoe 4 exceeds a predetermined value, the spring 52 is compressed by the input, and the first As shown in FIG. 4, one anchor 5 is configured to swing and bias the brake shoe 4 in the disengagement direction (clockwise in FIG. 4).

Further, a second anchor 6 is provided on the inner surface of the back plate 1 at a position facing the other end of the brake shoe 4 in the length direction, and a second anchor 6 is provided at the other end of the brake shoe 4 in the length direction. A gap S is provided between the brake shoe 4 to allow the brake shoe 4 to swing around the first anchor 5, and when the input from the wheel cylinder 3 to the brake shoe 4 exceeds a predetermined value. , said first
As shown in FIG. 4, from the moment when the anchor 5 swings and urges the brake shoe 4 in the detachment direction, the brake shoe 4 is rocked using the second anchor 6 as a fulcrum. ing.

Note that 7 in the figure indicates a lining attached to the outer peripheral surface of the brake shoe 4.

Next, the operation of the brake drum constructed as described above will be explained.

As the brake shoe 4 swings in the diametrically expanding direction in response to the input from the wheel cylinder 3, the lining 7 of the brake shoe 4 comes into pressure contact with the inner circumferential surface of the brake drum 2, thereby performing braking. When the input from the wheel cylinder 3 is below a predetermined value, the spring force of the spring 52 is greater than the input, so the brake shoe 4 1 anchor 5 as a fulcrum and swings in the direction of diameter expansion.

When the input from the wheel cylinder 3 reaches a predetermined value or more, the first anchor 5
However, as shown in FIG. 4, it swings in the direction of detachment from the brake shoe 4 while resisting the spring 52, and at the same time, the swinging around the first anchor 5 as a fulcrum is released. By moving the brake shoe 4 toward the second anchor 6, the gap S between the second anchor 6 and the brake shoe 4 is closed, and the other end of the brake shoe 4 in the length direction is closed. is received by the second anchor 6, and thereafter the brake shoe 4 is received by the second anchor 6.
Using this as a fulcrum, it further swings in the direction of diameter expansion and performs braking.

Therefore, in the above braking operation, the distance between the center point of the brake drum 2 and the brake shoe 4 is longer than the distance L1 between the center point of the brake drum 2 and the support point of the brake shoe 4 with respect to the second anchor 6. Since the distance L2 between the support point and the first anchor 5 is shorter, as shown in FIG. Changes in the generated braking force (area shown in Figure 5 B)
However, the first anchor 5 of the brake shoe 4
This is smaller than the change in braking force that occurs as the brake force swings in the direction of diameter expansion with This increases the effectiveness of the brakes and prevents them from becoming too effective in high deceleration areas.

(Effects of the Invention) As described above, the present invention provides a drum brake that includes an arcuate brake shoe and a brake drum, and in which a wheel cylinder is provided at one end in the length direction of the brake shoe. At least one first anchor is provided at an intermediate portion in the longitudinal direction, and a second anchor is provided at the other end in the length direction of the brake shoe, and the first anchor is placed in a detached position away from the brake shoe. A gap is provided between the second anchor and the brake shoe to allow the brake shoe to swing with the first anchor as a fulcrum. In a range where the input is lower than a predetermined value and the brake shoe swings about the first anchor,
While the change in braking force with respect to the input to the brake shoe is large, in the range where the input to the brake shoe exceeds a set value and swings around the second anchor as a fulcrum, the change in braking force with respect to the input is large. The change in the braking force is smaller than the previous trend, and therefore, during braking, it is possible to increase the effectiveness of the brake in the low speed range and prevent the brake from being too effective in the high deceleration range. This led to this.

[Brief explanation of the drawing]

Fig. 1 is a front view with some parts omitted of a drum brake according to the present invention, Fig. 2 is an enlarged sectional view taken along the line of Fig. 1, and Figs. Fig. 5 is an explanatory diagram showing the characteristics of the braking force generated when braking the drum brake according to the present invention, and Fig. 6 is an explanatory diagram showing the characteristics of the braking force generated when braking the conventional drum brake. be. 2... Brake drum, 3... Wheel cylinder, 4... Brake shoe, 5... First anchor, 6... Second anchor, S... Gap.

Claims (1)

[Scope of utility model registration request] A drum brake comprising an arc-shaped brake shoe and a brake drum, and a wheel cylinder provided at one end in the length direction of the brake shoe,
At least one first anchor is provided at an intermediate portion in the length direction of the brake shoe, and a second anchor is provided at the other end of the brake shoe in the length direction, so that the first anchor is attached to the brake shoe. A gap is provided between the second anchor and the brake shoe to allow the brake shoe to swing about the first anchor as a fulcrum. Drum brakes are characterized by: