Drum brake

Abstract

Faces of a rim portion 20b of a brake shoe 20 of a drum brake brought into contact with a backing plate 18 on a side of a wheel cylinder and on a side of an anchor are brought into contact with and supported by first ledge portions “b”, “c” formed at an upper face of the backing plate, and a face of the rim portion 20b of the brake shoe 20 formed substantially at a center position thereof and brought into contact with the backing plate 18 is brought into contact with and supported by a second ledge portion “a” formed at a lower face of a cut-to-rise portion 18a of the backing plate 18.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view of a drum brake according to Embodiment 1 of the invention.

FIGS. 2A and 2B illustrate schematic views for explaining a relationship of attaching a return spring and a brake shoe, FIG. 2A shows a relationship of attaching a return spring on a side of a wheel cylinder and a brake shoe, and FIG. 2B shows a relationship of attaching a return spring on a side of an anchor and a brake shoe.

FIGS. 3A to 3C illustrate sectional views of a drum brake according to Embodiment 1 of the invention, FIG. 3A is a sectional view taken along a line A-A of FIG. 1 showing a relationship of bringing substantially a center position of a rim portion and a backing plate into contact with each other, FIG. 3B is a sectional view taken along a line B-B of FIG. 1 showing a relationship of bringing a position of a rim portion at a vicinity of a side of a wheel cylinder and a backing plate into contact with each other, and FIG. 3C is a sectional view taken along a line C-C of FIG. 1 showing a relationship of bringing a position of a rim portion at a vicinity of a side of an anchor and a backing plate into contact with each other.

FIG. 4 is a front view of a drum brake according to Embodiment 2 of the invention.

FIGS. 5A to 5C illustrate sectional views of the drum brake according to Embodiment 2, FIG. 5A is a sectional view taken along a line D-D of FIG. 4 showing a relationship of bringing substantially a center position of a rim portion and a backing plate into contact with each other, FIG. 5B is a sectional view taken along a line E-E of FIG. 4 showing a relationship of bringing a position of a rim portion at a vicinity of a side of a wheel cylinder and a backing plate into contact with each other, and FIG. 5C is a sectional view taken along a line F-F of FIG. 4 showing a relationship of bringing a position of a rim portion at a vicinity of a side of an anchor and a backing plate into contact with each other.

FIG. 6 is a partial sectional view of a shoe hold-down mechanism comprising a coil spring and a shoe hold-down pin of a background art.

Claims

1. A drum brake comprising: a backing plate;a brake shoe slidably supported on the backing plate;a return spring, wherein a spring force of the return spring acts to the brake shoe at a position of being offset from a center in a width direction of a rim portion of the brake shoe in a direction of being remote from the backing plate to an upper side;first ledge portions formed at an upper face of the backing plate, wherein faces of the rim portion of the brake shoe brought into contact with the backing plate on a side of a wheel cylinder and on a side of an anchor are brought into contact with and supported by the first ledge portions; anda second ledge portion formed at a lower face of a cut-to-rise portion of the backing plate, wherein a face of the rim portion of the brake shoe brought into contact with the backing plate formed substantially at a center position is brought into contact with and supported by the second ledge portion.

2. The drum brake according to claim 1, further comprising: a struck-out nib formed on the face of the rim portion brought into contact with the backing plate, and projected to a side of a web of the brake shoe.

3. The drum brake according to claim 1, further comprising: a fold-to-bend piece formed on the face of the rim portion brought into contact with the backing plate, and constituted by being folded to bend to a side of a web of the brake shoe.