JPH0218836Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a wheel cylinder for pressing the brake shoe of a drum brake against a brake drum. The present invention relates to a wheel cylinder equipped with a boot, which is characterized by a stopper means that defines the limit of pushing of the piston into the cylinder body.

BACKGROUND TECHNOLOGY Generally, in a drum brake wheel cylinder, a piston, which is brought into contact with one end of the brake shoe, is fitted into the cylinder body so as to be able to protrude from an opening in the cylinder body. This plays the role of pressing the brake shoe against the brake drum, but in order to prevent muddy water, dirt, etc. from entering the cylinder body, dust is placed between the protruding end of the piston and the opening of the cylinder body. Boots are usually worn. In addition, in order to prevent the piston from penetrating deeply into the cylinder body when the piston is assembled into the cylinder body, a stopper means is often provided to define the pushing limit of the piston.

Conventionally, in such wheel cylinders, as the stopper means, an annular stopper plate is located within the dust cover and between the dust cover and the open end of the cylinder body to prevent the piston from protruding. It was fixed at the end of the cylinder, and when the piston was pushed into the cylinder body for assembly etc., it came into contact with the open end of the cylinder body to define the pushing limit of the piston, but the dust boot Because one end of the brake shoe is brought into close contact with the protruding end of the piston, when the piston, cylinder body, and brake shoe are assembled, one end of the brake shoe comes into contact with the dust boot and dust is removed. There was a risk of damaging the boots.

Therefore, by attaching a substantially disc-shaped stopper plate having an outer diameter larger than the inner diameter of the opening of the cylinder body to the protruding end of the piston on the outside of the dust boot, the piston can be pushed into the cylinder body. It is contemplated to define limits and prevent one end of the brake shoe from interfering with the dust boot.

Problems to be Solved by the Invention However, there are still problems to be solved in the wheel cylinder equipped with the stopper plate as described above. In other words, in such a wheel cylinder, one end of the brake shoe is usually connected to the protruding end of the piston in order to restrict the relative movement of the end of the brake shoe toward and away from the bucking plate with respect to the protruding end of the piston. It is designed to be inserted into an engagement groove formed on the end face, but since this engagement groove is usually formed by cutting, it takes a relatively long time to process the engagement groove. This was one of the factors that hindered cost reduction of wheel cylinders.

The present invention was developed against the background of the above circumstances, and its purpose is to provide a wheel cylinder equipped with a stopper plate at a lower cost by eliminating the need for an engagement groove on the protruding end surface of the piston. be.

Means for Solving the Problems In order to achieve the above object, the present invention includes a cylinder body fixed to a bucking plate, a cylinder body fitted into the cylinder body so as to be able to protrude from an opening thereof, A piston with which one end of the brake shoe provided on the plate is brought into contact with the protruding end; a dust boot installed between the protruding end of the piston and the opening of the cylinder body; and the cylinder body. a substantially disk-shaped metal member having an outer diameter larger than the inner diameter of the opening of the piston, which is located between the dust boot and the brake shoe and extends from the piston in a state perpendicular to the axis of the piston. A stopper plate that is attached to the end of the cylinder body and determines the push limit of the piston into the cylinder body based on contact with the open end of the cylinder body, and also prevents one end of the brake shoe from interfering with the dust boot. A pair of regulating portions for regulating relative movement of one end of the brake shoe toward and away from the bucking plate with respect to the protruding end of the piston. , characterized in that the stopper plate is formed by press working.

Operation and Effect of the Invention By doing this, the pair of regulating parts formed by press working on the stopper plate can move the brake plate toward and away from the protruding end of the piston at one end of the brake shoe. Since the movement is restricted, there is no need to form an engagement groove by cutting on the protruding end surface of the piston as in the conventional case, and the cost of the wheel cylinder equipped with the stopper plate can be further reduced.

Embodiment Hereinafter, an embodiment of the present invention will be described in detail based on the drawings.

FIG. 2 is a schematic front view of a leading-trailing type drum brake including a wheel cylinder 10 according to an embodiment of the present invention, with the brake drum 12 rotating together with the wheel removed. The wheel cylinder 10 is fixed to a bucking plate 14 fixed to a non-rotating member, and a pair of brake shoes 16, 16 are attached to the bucking plate 14 so as to be expandable with an anchor 18 as a fulcrum. It is constantly biased in the diameter reduction direction by two return springs 20. The brake shoes 16, 16 are pushed apart by the operation of the wheel cylinder 10 and are pressed against the brake drum 12, thereby achieving a braking action.

The wheel cylinder 10 has two pistons 24 slidably fitted into a cylinder body 22 with a common hydraulic chamber in between.
One end of the brake shoe 16 is brought into contact with each of the pistons 24, and both pistons 24 are protruded from the openings at both ends of the cylinder body 10 due to the supply of hydraulic fluid to the hydraulic pressure chamber, thereby applying the brake. Push out the shoes 16, 16.

Since both of the two pistons 24 have the same structure, the one on the right side (portion A) in FIG. 2 will be described, and the description of the piston 24 on the opposite side will be omitted.

An enlarged sectional view of part A is shown in FIG. As is clear from this figure, the piston 24
The piston body 26 includes a piston body 26 that is slidably fitted into the cylinder body 22, and a head portion 28 that is integrated with the end surface of the piston body 26 on the side protruding from the cylinder body 22 by press fitting. . The head portion 28 is a short shaft-shaped member having a smaller diameter than the piston body 26, and holds the inner circumferential edge of the dust boot 32 between the head portion 28 and the piston body 26. The outer peripheral edge of this dust boot 32 is connected to the cylinder body 22.
By being attached to the outer peripheral surface of the opening, it covers the opening and protects the cylinder body 22 and piston body 2.
This prevents muddy water, dirt, etc. from entering the sliding part with 6.

A disk-shaped stopper plate 34 is provided at the tip of the piston head 28, that is, at the protruding end of the piston 24. This stopper plate 34 has a center hole 37 as shown in FIG. 4 by bending a metal plate 36 punched into the external shape shown in FIG. It is a plate member curved into a disk shape, and its outer diameter: D is a certain dimension larger than the inner diameter: d of the opening of the cylinder body 22, and is approximately equal to the outer diameter of the opening. There is.

The stopper plate 34 also includes a pair of guide plate portions 38, 38 that stand up vertically from the center of one plate surface, and these guide plate portions 38
is formed by bending the tabs 40, 40 on both sides of the developed metal plate 36 shown in FIG.
They are opposed to each other in parallel with an interval wider than the plate thickness of 6. The center hole 37 has a size that allows it to fit into the piston head portion 28, and shallow rectangular notches 44, 44 are provided at the bent base of each guide plate portion 38, and are connected to the center hole 37.
are formed, and the longer edge surfaces of these notches 44 define the amount by which the stopper plate 34 fits into the piston head portion 28.

And, such a stopper plate 34,
As is clear from FIG. 1, the dust boot 3
2 and one end of the brake shoe 16, the position is perpendicular to and concentric with the axis of the piston 24, and the guide plate portion 38 faces in the forward direction of the piston 24 and is parallel to the brake shoe 16. It is fixed to the protruding end of the piston 24 in such a posture. That is, as a result of being fitted into the tip of the piston head 28 in the center hole 37 and bringing the end surface of the piston head into contact with the edge surface of the notch 44,
The tip of the head portion 28 slightly protrudes from the plate surface of the stopper plate 34, and the outer peripheral edge portions of the protruding portion located on both sides of the guide plate portion 38 are caulked, thereby causing the stopper plate 34 to is integrated with the piston head portion 28. Reference numeral 46 in FIG. 5 indicates the caulking portion.

As a result, the stopper plate 34 protrudes from the outer circumferential surface of the piston head portion 28 in the shape of a radially outward circular flange, and is spaced a certain distance from the outside of the dust boot 32 to the end surface of the opening of the cylinder body 22. As a result, when the piston 24 is pushed into the cylinder body 22 for assembly etc., the stopper plate 34 is inserted into the opening of the cylinder body 22 via the dust boot 32. By coming into contact with the end surface of the brake shoe 16, the push limit of the piston 24 into the cylinder body 22 is determined, and when the wheel cylinder 10 and the brake shoe 16 are assembled to each other, the brake shoe 16 is
The stopper plate 34 prevents the dust boot 32 from being damaged by one end of the dust boot 32 .

One end portion of the brake shoe 16 formed in an arc shape is inserted between a pair of mutually opposing guide plate portions 38 and comes into contact with an abutting surface 48 formed by the end surface of the head portion 28. are brought into contact with
As a result, the movement of one end of the brake shoe 16 in the plate thickness direction (the direction of approaching and separating from the bucking plate 14) is regulated by the pair of guide plate portions 38. Therefore, the pair of guide plate portions 38 constitute the pair of restriction portions of this embodiment.

As described above, according to this embodiment, the stopper plate 34 fixed to the head portion 28 of the piston 24
A pair of guide plate portions 3 formed by press working on the
8, the backing plate 1 is attached to the piston head 28 at one end of the brake shoe 16.
Since the relative movement in the direction toward and away from the piston head 4 is restricted, there is no need to form an engagement groove on the tip end surface of the piston head 28 by cutting as in the conventional case.
This defines the limit to which the piston 24 can be pushed into the cylinder body 22 and also defines the limit for pushing the piston 24 into the cylinder body 22.
The cost of the wheel cylinder 10 equipped with the stopper plate 34 having the function of preventing damage to the dust boot 32 by one end of the dust boot 32 can be further reduced compared to the conventional one.

Note that the present invention can be implemented in other forms as well.

For example, as shown in FIG. 6, a hat-shaped stopper plate 5 is provided at the tip of the piston head 28.
0 so that one end of the brake shoe 16 is brought into contact with the central plate surface of the stopper plate 50, and the portions of the stopper plate 50 located on both sides of one end of the brake shoe 16 are The brake shoe 16 is formed by a pair of guide plate portions 38 formed by cutting and bending with a press.
The relative movement of one end of the piston head 28 with respect to the piston head 28 may be restricted. In this case, the outer peripheral edge of the stopper plate 50 may be extended to form a cylindrical shape so as to cover the side wall of the dust boot 32.

It goes without saying that the present invention can be implemented with various modifications and improvements based on the knowledge of those skilled in the art.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a main part of a wheel cylinder according to an embodiment of the present invention, and is an enlarged sectional view of a portion A in FIG. FIG. 2 is a schematic front view of the drum brake to which the wheel cylinder is assembled. FIG. 3 is a plan view of a metal plate punched out to obtain the stopper plate shown in FIG. 1, in other words, a developed plan view of the stopper plate. 4 is a perspective view of a stopper plate obtained by bending the metal plate material of FIG. 3, and FIG. 5 is a perspective view of the stopper plate obtained by bending the metal plate material of FIG.
FIG. FIG. 6 is a sectional view of a main part showing another embodiment of the present invention. 10...Wheel cylinder, 12...Brake drum, 16...Brake shoe, 22...Cylinder body, 24...Piston, 26...Piston body, 28...Head part, 34, 50...Stopper plate , 38... Information board section (regulation section).

Claims (1)

[Claims for Utility Model Registration] A cylinder body fixed to a bucking plate, and one end of a brake shoe fitted into the cylinder body so as to be able to protrude from an opening thereof, and provided on the bucking plate. a piston whose part is brought into contact with the protruding end; a dust boot installed between the protruding end of the piston and the opening of the cylinder body; and an outer diameter dimension larger than the inner diameter of the opening of the cylinder body. a substantially disc-shaped metal member having a substantially disc-shaped metal member located between the dust boot and the brake shoe and mounted on the protruding end of the piston in a state perpendicular to the axis of the piston; A stopper plate that defines a pushing limit of the piston into the cylinder body based on contact with the open end of the body and prevents one end of the brake shoe from interfering with the dust boot. In the drum brake wheel cylinder of the above type, a pair of regulating portions for regulating relative movement of one end of the brake shoe toward and away from the bucking plate with respect to the protruding end of the piston are provided in the stopper. A wheel cylinder for drum brakes characterized by being formed by press working on a pump plate.