JPS5962731A - Leading/trailing type drum brake - Google Patents

Abstract

PURPOSE:To aim at effectively use a lining material of a trailing shoe to prolong the usable time thereof, and to simplify the manufacture thereof, by making a leading shoe in a floating type and as well by making the trailing shoe in a pivot type. CONSTITUTION:In a leading shoe 3, a lining 3a is wore due to its self-servo action maximumly in the vicinity of the position B. The end face of a shoe web 4b is abutted against an arcuate section 10a which is a contact surface of an anchor block 10 with respect to a trailing shoe 4, having a radius (r) of curvature. In this arrangement, by making the radius of curvature of the end face of the web 4b slightly less than the radius (r) of curvature of the anchor block 10, smooth rotation may be obtained. The shoe 4 is made in a pivot shape which allows the shoe 4 to rotate substantially about the center point P, as its pivot point, of the radius (r) of curvature of the anchor block 10, and the lining 4c is wore maximaly in the direction D which is orthogonal to the line C connected between the center point O of the brake and the center point P of the radius (r) of curvature so that the life of the shoe against abrasion may be prolonged.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in leading-trailing type drum brakes.

In the case of this type of drum brake, the leading shoe has a self-servo effect, but the trailing shoe does not have a self-servo effect. Therefore, in conventional brakes where both the leading shoe and the trailing shoe are floating shoes, even if the product accuracy is somewhat low, it will not have a fatal negative effect on the brake function, but the lining of the trailing shoe Only the shoe operating side of the lining wears significantly, so-called uneven wear in the circumferential direction of the lining, which is undesirable from the standpoint of resource conservation.

In addition, there are other shoe types in which both the leading shoe and the trailing shoe are pivot-type shoes, which improves the maximum wear position of the lining, but in this type of shoe type, product accuracy is improved. Because it is necessary, its production is extremely troublesome. In particular, if the circumferential direction and end surface of the lining of the leading shoe, which has a self-servo action, is in constant contact with the drum, the shoe will be pulled by the drum and the brake will be activated, leading to early wear of the lining due to dragging and peeling of the lining due to abnormal heat generation. This resulted in problems such as deterioration of rubber parts.

The present invention solves the above-mentioned problems of the shoes by making the lead-in bushing a floating shoe and the trailing shoe a pivot shoe.

This will be explained below with reference to the drawings. FIG. 1 shows an example of a conventional leading-trailing type drum brake commonly used in vehicles, and both the leading shoe and trailing shoe are floating type shoes. 1 is a rotatable drum, 2 is a back plate fixed to the stationary part, 3 and 4 are a pair of opposing brake shoes, which are formed into a T-shaped cross section by shoe rims 3a, 4a and shoe webs 8b, 4b; Linings 8'c and 4c are attached to the outer peripheries of shoe rims 8a and 4a.
.

Shoes 8, 4 indicated by dashed lines are a diagram of the initial state of the lining 8C14c, and shoes 8°4 indicated by a solid line are a diagram of the state when the linings 8c, 4c are worn out. 5 is a double-opening type wheel cylinder fixed to the back plate 2, and its pair of pistons 5a, 5b are connected to shoe webs a, b, 4. , b are lightly abutted on the upper opposite ends of each. Reference numeral 6 denotes an adjuster installed between a pair of shoes 8.4 adjacent to the wheel cylinder 5, and is composed of a bolt 7, a nut 8 and a tube member 9. The left side of the bolt 7 is crushed into a fork shape, and this fork-shaped portion 7a fits into the notch groove 3 of the shoe web 8b.
It is engaged so as to intersect with d. Further, a nut 8 having uneven teeth on the outer periphery is attached to the intermediate portion of the right screw shaft portion 7b, and the screw shaft portion 7b protruding from the nut 8 floats into the inner water on the left side of the tube member 9. When the nut 8 is fitted, the right end surface of the nut 8 abuts the left end surface of the tube member 9, and the adjuster 6
The length of is now determined. The right side of the tube member 9 is crushed into a fork shape, and this fork-shaped portion 9a engages in a crosswise manner with the notch groove 4d of the shoe web 4b. 10 is Shoeweb, llb, 4b
The anchor block is installed between the lower opposite ends of the back plate 2 and is fixed to the back plate 2 by rivets lla and llb. 12a and 12b are springs that urge the shoes 3 and 4 toward each other, and 18a and 18b are shoe hold devices that lightly press the shoes 8.4 against the back plate 2.

Next, we will explain the brake operation of the brake device mentioned above.

Tomorrow.

When pressure fluid is supplied to the boil cylinder 5, the piston 5
a, 5b advance to the left and right, shoes 3, 4 spring 12a,
12b and expand using the point of contact with the anchor block JO as a fulcrum. As a result, the linings 8c, 4c frictionally engage the rotating drum 1, thereby braking it.

Then, when the supply of pressure fluid is cut off, the shoes 3 and 4 release the spring Ila.
, 12b, the state is almost returned to the state before the brake operation.

゛Also, if the linings 3c, 4c are worn and the gap between the drum 1 and the linings 8c, 4c becomes larger than a predetermined amount, turn the nut 8 in the direction to pull out the bolt 7 from the tube member 9. By rotating it, the entire length of the adjuster 6 can be extended, so the drum l and lining 8. c, 4
Now you can correct the gap between drum 1 and c.
is rotating in the direction of arrow X, the shoe 8 on the piston 5a side that acts in the same direction as the rotation direction of the drum 10 is the leading shoe, and the shoe 8 on the piston 5a side that acts in the opposite direction
Shoe 4 on the b side is the trailing shoe.

+)-Since self-servo action is applied to D7 and GSH8 by the acting force of the piston 5a and the torque generated between the drum 1 and the lining 3C, the wear of the lining 8C is greater than the horizontal MA that crosses the center of the brake in this figure. The position slightly closer to the anchor block 10 (the position in the brake radial direction indicated by line B in the figure) has the largest number of brakes. On the other hand, in the case of the trailing shoe 4, when the acting force of the piston 5b is applied, the torque generated between the drum l and the lining 4C tries to move the shoe 4 toward the wheel cylinder 5, so that a self-servo action is activated. Therefore, the wear of the lining 4c is greatest near the end on the wheel cylinder 5 side.

As is clear from the above explanation, lining 3C.

As the lining 4C wears, the shoes 8 and 4 move in the brake radial direction where the most wear occurs, so especially in the trailing shoe 4, as shown by the solid line in FIG. 1, the anchor block 10 side of the lining 4C does not wear at all. This resulted in extremely large waste of lining 4C.

In the present invention, in order to improve the wear condition of the above-mentioned trailing shoe during the second innings, the shoe is made into a pivot type shoe. Therefore, the components of the brake are the same as the components of a conventional brake and are designated by the same reference numerals. Furthermore, the linings in the first to third actual hTg examples all show a worn state.

That is, FIG. 2 shows a first embodiment of the present invention, in which the contact surface with -4 is arcuate with a radius of curvature indicated by r.

and the arc-shaped portion]0. If the radius of curvature of the abutting end surface of the shoe web 4b is made slightly smaller than the radius of curvature r of the anchor block 100, desirable smooth rotation of the shoe 4 can be obtained. Thus, the trailing shoe 4 becomes a pivot-shaped shoe that rotates about the center point P of the radius of curvature r of the anchor block 100 as a fulcrum, and the lining 4c of the shoe 4 connects the brake center 0 and the center P of the radius of curvature r. The brake radial direction perpendicular to the dead line C engages the drum 1 first. Therefore, the wear of the lining 4c in this linear direction is greatest, and the wear life of the lining 4c is extended compared to the conventional one.

FIG. 3 shows the main part of a second embodiment according to the present invention. This embodiment is obtained by removing the arcuate portion of the anchor block 10 on the brake center side in the first embodiment described above, and similarly to the first embodiment of the present invention, the trailing shoe 4 is located at the center of the radius of curvature r. Since it rotates with P as the fulcrum, the same effect can be obtained.

FIG. 4 shows an eighth embodiment of the present invention, in which the center point Q of the radius of curvature R of the arcuate portion 10b of the anchor block 100 that the trailing shoe 4 abuts is set to a vertical line passing through the center of the brake in FIG. This is set on line E. If you do this, the lining 4c of the trailing shoe 4
Since the horizontal line entering direction, which is perpendicular to the vertical line E and passing through the center of the brake, engages the drum l first, the lining 4c wears the most in this direction. In addition, in this embodiment, a desired angle σ) is provided on the contact surface of the anchor block 10 that the leading shoe 3 contacts, and the line B (shown in FIG. 240) of the conventional example that moves in the brake radial direction of the shoe 3 is set. The direction is made to approach the above-mentioned horizontal mA, so that the linings 8C and 4C of both the leading shoe 3 and the trailing shoe 4 can be heated once per hour.

According to the present invention, as is clear from the above description, the leading shoe, which has self-servo properties and tends to cause drag, is made into a floating type shoe, and the trailing shoe, which does not have self-servo properties, is made into a pivot type shoe. In addition to making effective use of the lining material of the trailing shoe, the shoe can be used for a long time, and it is easy to manufacture. The invention is not limited to the embodiments described above; for example, a portion of the anchor of the trailing shoe may be rotatably supported by a pin.

[Brief explanation of drawings]

FIG. 1 is a front view showing one embodiment of a conventional leading-trailing type drum brake, and FIG.
FIG. 8 is a front view of a part of the anchor showing a second embodiment of the invention, and FIG. 4 is a front view of a third embodiment of the invention. 1...Drum, 3...Leading shoe, 4...
・Trailing shoe, 5...Wheel cylinder, 6
...Adjuster, 10...Anchor block, 1
0a, 10b... Arc-shaped parts.

Claims (1)

[Claims] L A leading/trailing type drum brake characterized in that the leading shoe is a floating type shoe and the trailing shoe is a pivot type shoe.