JPS5811952Y2 - Piston device for vehicle drum brakes - Google Patents

Description

[Detailed description of the invention] The present invention relates to a piston device for a drum brake for a vehicle. In particular, in order to prevent noise (commonly referred to as squeal) that occurs during braking, the present invention is designed to transmit force from the piston to the brake shoes. In a piston device that uses a piston insert mainly made of vibration damping material, even if the vibration damping material is crushed, the crushed pieces will not escape to the outside of the piston, and the piston insert and piston To provide a piston device in which the squeal prevention effect does not deteriorate due to mud being clogged in the gap between the pistons.

Focusing on the fact that the cause of brake squeal is the vibration of brake component members, as shown in FIG. There are known methods to attenuate noise and prevent squealing.

A circular hole 1a with a bottom is provided in the axial direction from the outer end surface of the piston 1 fitted in the wheel cylinder 10,
A piston insert 2 is loosely fitted into this circular hole 1a, and this piston insert 2 fixes a metal disk body 2b and a vibration damping material 2a that contacts the bottom surface 1b of the circular hole 1a with this outside. It is a unified whole.

The vibration damping material 2a is a roughly cylindrical member made of synthetic resin, rubber, soft metal, etc., and the end surface of the vibration damping material 2a in contact with the bottom surface 1b of the circular hole 1a has a protruding conical surface 2C in the center. The bottom surface 1b also forms a conical recess of the same shape.

The outer end surface of the metal disc body 2b is in contact with the brake shoe 3, and the piston insert 2 is inserted between the piston 1 and the brake shoe 3 in a sandwiched state.

The piston device having such a configuration has an extremely excellent squeal prevention performance, and the inner end surface of the vibration damping material 2a (
It has been recognized that forming 2C) into a conical shape is effective in improving the squeal prevention performance.

The reason for this is not completely clear, but if mud gets stuck between the piston 1 and the piston insert 2, the noise prevention effect will be significantly reduced, and the effect will be restored after cleaning. The presence of a gap between the two is effective in preventing noise, and by making the inner end surface (2C) of the vibration damping material and the circular hole bottom surface 1b a conical surface, the piston insert 2 is located at the center of the circular hole 1a. It is assumed that one of the reasons for this is that the piston insert 2 is held at a constant temperature so that a gap is reliably formed around the entire circumference of the piston insert 2.

By the way, the driving force of the brake is generated by the wheel cylinder 10.
When transmitted from the piston 1 to the brake shoe 3,
Since the vibration passes through the piston insert 2, which has a relatively small cross-sectional area, there is a risk that the vibration damping material 2a may become fatigued due to vibration absorption or severe repeated loads, and may fracture when subjected to severe loads such as during sudden braking. There is.

If the piston insert 2, which was interposed between the piston 1 and the brake shoe 3 and played the role of load transmission, is crushed and scattered outside the piston 1, a large gap will be created between the piston 1 and the brake shoe 3. Therefore, unless the piston 1 is pushed out from the wheel cylinder 10 by that much amount, the brake shoe 3 will not be able to come into sliding contact with the brake drum, which causes the inconvenience that the brake pedal stroke will suddenly become larger than before the piston insert was broken. arise.

Further, this piston device also had a problem in that the gap between the piston insert 2 and the piston 1 was clogged with mud, reducing the squeal prevention effect.

This invention was made against the background of the above circumstances,
The gist is that a sealing ring made of an elastic material such as an O-ring or a packing is provided between a bottomed circular hole provided in the piston shaft center and a piston insert that loosely fits into the circular hole. The purpose is to prevent fragments of the crushed vibration damping material from escaping and to prevent mud from entering the gap between the circular hole and the piston insert.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

FIG. 2 shows the first embodiment of the present invention.
Components similar to those of the conventional device shown in the figure are given the same reference numerals to indicate the correspondence therebetween, and detailed description thereof will be omitted.

An annular groove 1C is provided on the inner surface of the circular hole 1a facing the metal disc body 2b, into which an O-ring 4 is fitted.

Therefore, even if the piston insert 2 is crushed, the crushed pieces will be prevented from escaping outside the piston 1.
The sinking of the piston insert 2 into the circular hole 1a is minimized, and the increase in brake pedal stroke can be suppressed to a small amount that does not pose a problem in practice.

That is, since a gap is formed between the piston insert 2 and the piston 1 as described above, if the vibration damping material 2a is crushed, the crushed pieces and powder will fill this gap, and the The metal disk body 2b will sink into the circular hole 1a, but since the gap between the piston insert 2 and the piston is usually 0.2 to Q on one side, a small amount of 3 mm is sufficient, so that crushed pieces etc. The amount of sinking of the metal disc body 2b that occurs to fill this gap is also small.

In addition, the O-ring 4 has the role of preventing crushed pieces inside the piston 1 from dissipating to the outside as described above, and at the same time preventing muddy water etc. from entering into the gap between the piston 1 and the piston insert 2. As a result, the crevice will not be clogged with mud and the anti-squeal effect will not deteriorate, and the good anti-squeal effect can be maintained for a long time.

A second embodiment of the invention is shown in FIG.

A unique feature of this embodiment is that an annular groove 2d is provided on the outer periphery of the metal disc body 2b, and an O-ring 4 is fitted into the annular groove 2d.

This embodiment has unique effects such as preventing the scattering of crushed pieces and mud intrusion, as well as the ease of machining the groove 2d and the easy and inexpensive replacement of the O-ring 4.

A third embodiment of the present invention is shown in FIG.

The peculiar point of this embodiment is that the annular groove IC, 2d is the circular hole 1a.
The O-ring 4 is provided on the inner surface and the outer circumferential surface of the metal disc body facing the inner surface, and is fitted into both grooves IC, 2d while being held therein.

Note that the means for preventing the dispersion of crushed pieces is not limited to the O-ring, and can prevent the dispersion of crushed pieces of the vibration damping material and the intrusion of mud without preventing the radial movement of the metal disk body. Any sealing ring made of elastic material is sufficient.

As described in detail above, the present invention is capable of preventing mud from escaping to the outside of the piston and from entering the inside of the piston when the vibration damping material is crushed by installing an extremely simple sealing ring. Therefore, it is possible to prevent the gap between the piston and the brake shoe from being varied and the brake pedal stroke to increase significantly, and it is also possible to prevent mud from clogging up the gap between the piston insert and the piston and reducing the anti-squeal effect. This has the effect of preventing

[Brief explanation of the drawing]

FIG. 1 is a sectional front view of a main part of a conventional device. FIG. 2 is a sectional view of the main part showing one embodiment of the present invention, FIG. 3 is a sectional view of the main part showing the second embodiment, and FIG.
The figure is also a sectional view of a main part showing the third embodiment. 1: Piston, 1a: Circular hole, 1b: Bottom surface, 1C: Annular groove, 2: Piston insert, 2a: Vibration damping material, 2b
: Metal disc body, 2C: Conical surface, 2d: Annular groove, 4:
0' J-ring (sealing ring made of elastic material), 10: Wheel cylinder.

Claims (1)

[Scope of utility model registration claim] Fitted into the wheel cylinder of a vehicle drum brake,
and a piston having a bottomed circular hole bored in the axial direction from the outer end surface, a cylindrical vibration damping material and a metal disc body fixed to one end face of the piston, the metal disc body a piston insert that is loosely fitted into the circular hole of the piston with the vibration damping member on the outside and abuts the bottom surface of the fixed hole at the other end surface of the vibration damping material, and the transmission of force from the piston to the brake shoe is carried out by the piston. A drum brake for a vehicle, in which a piston device is installed via an insert, characterized in that a sealing ring made of an elastic material such as an O-ring is provided between the inner surface of the circular hole of the piston and the outer circumferential surface of the disk body facing the piston. piston device.