RU2118725C1 - Device for automatic adjustment of clearance of drum brake and parking brake drive - Google Patents

Abstract

FIELD: mechanical engineering; automobile service brake and parking brake system. SUBSTANCE: device has threaded pusher hinge-secured on one of shoes for axial displacement. Adjusting bushing is turned onto pusher. Body is free to move in bushing. Conical surface of adjusting bushing, pressing to mated conical surface made on body, precludes rotation of adjusting bushing on pusher. Body, thrusting against driven lever, can be additionally pressed to the lever by spring. To reduce summary clearance between brake shoes and drum, adjusting bushing interlocking device is provided which is made in form of bimetallic plate or other member made of memorized shape effect material secured on body for engagement with teeth made on adjusting bushing. EFFECT: provision of stepless adjustment of clearance, increased reliability owing to use of thread with large helix angle. 3 cl, 3 dwg

Description

 The invention relates to the design of drum brakes of vehicles with a device for automatic adjustment of the working and parking brake systems.

 Drum brakes are known in which automatic clearance adjustment is carried out using various types of gear joints.

For example, the device according to the USSR patent N 1240369 A3, class F 16 D 65/52, 1981, contains an automatic drum brake adjusting device consisting of brake pads placed under the wheel cylinder between two spring-loaded and located with a gap relative to the drum with a stop in them node adjustments in the form of a spring element with respect to one of the blocks and a spacer element pivotally mounted on it with the possibility of changing the length and a stop element made on the spacer element
The disadvantage of these devices is the presence of step adjustment, which requires an increased clearance between the pads and the drum, and insufficient reliability of the design.

 The objective of the present invention is to provide a device for stepless adjustment of the gap due to easily-twisted threads with a large angle of elevation of the coil while increasing the reliability of the device.

 This goal is achieved by the fact that the spacer element contains a pusher spring-loaded and pivotally mounted on one of the pads with the possibility of axial movement by an amount that provides the necessary clearance between the pads and the drum, with an easily made thread and an adjustment sleeve screwed onto it, in which mounted with the possibility of movement and with emphasis in the drive lever, the housing, the spring, one end pressed against the protrusion of the brake pads, and the other end, through the thrust bearing, pressed to the shoulder of the adjusting sleeve with the possibility of turning it on the thread, a locking element that excludes the possibility of rotation of the adjusting sleeve, consisting of spring-loaded conical surfaces made on the housing and the adjusting sleeve.

 In addition, the housing can additionally be pressed against the drive lever by a spring fixed at one end to a brake shoe.

 Reducing the gap of automatic adjustment is ensured by the fact that the device contains teeth made on the adjusting sleeve, and a bimetallic plate or other locking element made of a material with a memory effect, temperature-sensitive, which ensures the rotation of the adjusting sleeve upon reaching high temperatures.

 In FIG. 1 shows a general view of a brake with an automatic clearance adjustment device; in FIG. 2 is a section AA in FIG. one; in FIG. 3 - locking device at high temperatures.

 The automatic adjustment device comprises a pusher 1 with an easily twisted thread pivotally mounted on the brake pad 2. An adjusting sleeve 3 is inserted into the pusher, into which the housing 4 is inserted. The conical surface B of the housing is pressed against the mating surface A of the sleeve by a spring 5 through a washer 6 and a thrust bearing 7. At its other end, the spring is installed abutting against the surface C of the brake shoe. The housing is mounted with emphasis on the surface D of the drive arm 8 and can additionally be pressed against it by a spring 9. The pusher has the possibility of axial movement relative to the shoe by an amount E, providing a constant total clearance between the shoes and the brake drum (not shown).

 The locking device at high temperatures consists of a bimetallic plate 10 mounted on the housing 4 and the teeth 11, made on the adjusting sleeve 3.

 The principle of operation of the proposed device is as follows.

 When creating pressure in the wheel cylinder 12, its pistons, moving, remove the pads within the clearance E, creating braking force. In the event of further movement of the pistons as a result of wear of the brake linings and the drum, a gap equivalent to wear is formed between surfaces A and B. In this case, the spring 5, acting on the adjusting sleeve 3 through the thrust bearing 7, rotates it on the thread until it touches surfaces A and B, increasing the length of the expansion link. After the cessation of braking, the pads under the action of the tension spring 13 move away from the brake drum by a total value corresponding to the axial clearance E, since the reverse rotation of the adjusting sleeve is prevented by friction between surfaces A and B.

 During emergency braking, accompanied by the release of a large amount of heat, the bimetallic plate 10 engages with the teeth 11 of the adjusting sleeve 3, preventing it from turning when a gap is formed between surfaces A and B.

 When the temperature decreases, the plate disengages from the teeth of the adjusting sleeve and its rotation when the gap between surfaces A and B is formed resumes.

 When the parking brake is activated, the drive lever 8, turning on the axis, acts through the expansion link on the block, pressing it to the brake drum and thereby creating braking force. The opposite shoe is also pressed against the brake drum by moving the upper end of the drive lever.

 Conducted preliminary tests of prototypes confirmed the performance of the design with a significant reduction in the free travels of the working and parking brake systems.

Claims (3)

 1. A device for automatically adjusting the clearance of the drum brake and the parking brake actuator, comprising an adjustment unit in the form of a brake pad located under the wheel cylinder between two spring-loaded and positioned brake-gap brake pads in the form of a spring-loaded relative to one of the pads and a spacer element pivotally mounted thereon with the possibility of changing the length and the locking element made on the spacer element, characterized in that the spacer element contains a pusher, support fixed and pivotally mounted on one of the blocks with the possibility of axial movement by an amount that provides the necessary clearance between the blocks and the drum with an easily twisted thread and with an adjustment sleeve screwed onto it, in which the housing is mounted with the possibility of movement and with emphasis in the drive lever, spring, one end pressed against the brake shoe, and the other end, through the thrust bearing, pressed against the shoulder of the adjusting sleeve with the possibility of turning it on the thread, locking element, suit The possibility of rotation of the adjusting sleeve, consisting of spring-loaded conical surfaces made on the housing and the adjusting sleeve.  2. The device according to claim 1, characterized in that the housing is additionally pressed against the drive lever by a spring fixed at one end to a brake shoe.  3. The device according to claim 1 or 2, characterized in that to reduce the gap of automatic adjustment contains teeth made on the adjusting sleeve, and a bimetal plate or other locking element made of a material with a memory effect, temperature-sensitive, ensuring rotation of the adjusting sleeve according to reaching high temperatures.

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