JPS5824025Y2 - Vehicle drum brake squeal prevention device - Google Patents

Description

[Detailed description of the invention] The present invention relates to a device for preventing noise (generally referred to as squeal) that occurs during braking in vehicle drum brakes, and is particularly applicable to a type of drum brake in which a shoe clearance adjustment mechanism is provided in the wheel cylinder. The present invention provides a device for preventing squeal in drum brakes.

It is widely known that the cause of brake squeal is the vibration of the brake component parts. Therefore, it is possible to dampen the vibration by interposing a vibration damping material made of rubber, synthetic resin, etc. between the brake component parts. It is not difficult to imagine that it is effective in prevention.

However, as a practical matter, it is not enough to just insert the vibration damping material anywhere, but the important issue is where to select the vibration damping material.

For example, the present invention aims to prevent the squeal of drum brakes that have a shoe clearance adjustment mechanism.
According to experiments conducted by the inventors of the present invention, a type of drum brake that has a shoe clearance adjustment mechanism on the anchor side and a type of drum brake that has a shoe clearance adjustment mechanism on the wheel cylinder side:
It was found that there was a noticeable difference in the squeal prevention effect when a similar vibration damping material was inserted into the shoe clearance adjustment mechanism, and the latter was far superior.

Furthermore, the noise prevention effect changes depending on the shape and installation of the vibration damping material, and it is difficult to use the vibration damping material in a manner that satisfies all aspects such as safety, durability, and productivity in the practical stage, apart from the laboratory stage. Intervention is not always easy.

Particularly in those having a shoe clearance adjustment mechanism on the wheel cylinder side, the space is extremely limited, making it even more difficult to attach the vibration damping material.

In other words, the outer diameter of the piston is determined by the required braking force, the amount of regulating fluid that can be supplied, the pressure, etc., and cannot be made arbitrarily large. Adjusting bolts and the like are also members that transmit the brake operating force, so they need to be larger than the chamber for strength reasons.
Therefore, it is not easy to interpose a vibration damping material between them.

Therefore, the inventors of the present invention took a last-ditch measure and did not intervene between the outer peripheral surface of the adjusting nut and the inner peripheral surface of the bottomed hole of the piston, but only between the end surface of the adjusting nut and the bottom surface of the bottomed hole of the piston. When we experimented with a prototype insert with this shape, we found that, contrary to expectations, even an insert with this shape could provide a sufficient squeal prevention effect.

At the same time, it is most desirable for the insert to be made of synthetic resin such as phenolic resin in terms of anti-squeal effects, but it is also preferable to make the inserts from metal, especially aluminum, aluminum alloys, sintered alloys, etc., as well. It has also been found that it is desirable to leave a gap between the outer circumferential surface of the insert and the inner circumferential surface of the bottomed hole of the piston in order to prevent squealing.

In other words, inserts of the same shape are made of phenolic resin,
Experiments were conducted using aluminum, aluminum alloy, sintered alloy, etc., and in all cases the noise was less likely to occur compared to the case without an insert. Phenol resin has the greatest noise prevention effect, but aluminum and its It has become clear that alloys, sintered alloys, etc. can also have a considerable anti-squeal effect, and the anti-squeal performance can be improved by filling the gap between the outer circumferential surface of the insert and the inner circumferential surface of the bottomed hole of the piston. The anti-squeal performance was significantly reduced and recovered after cleaning, indicating that in addition to the vibration damping effect inside the insert, the ability of the insert to move slightly in the diametrical direction within the bottomed hole of the piston is also effective in preventing squeal. It was confirmed.

The adjusting nut is fitted into the bottomed hole of the piston and appears to be unable to move in the diametrical direction, but the fitting clearance between the two is usually 0.04 to 0.15 m.
m, whereas the width of the vibration of the shoe web when a squeal occurs at 2000 to 5000 Hz is 0.005 mm.
It is normal for the adjusting nut to be as follows, so it can be considered that the adjusting nut can move sufficiently in the diametrical direction in response to vibrations that occur when noise occurs. Therefore, the outer peripheral surface of the insert and the inner peripheral surface of the bottomed hole of the piston If a gap is left between them, the insert will also vibrate in the diametrical direction when squealing occurs, causing slippage somewhere on the contact surface with the piston and adjusting nut, which converts kinetic energy into heat and reduces the vibration. This is thought to have the effect of attenuating the

The present invention was completed based on the above facts and considerations, and its features are (a) a circular cylinder fitted into the wheel cylinder and drilled in the axial direction from the outer end surface; A piston having a bottom hole; 0) a female threaded hole rotatably fitted into the bottomed hole of the piston and passing through the center in the axial direction; and a star wheel fixed to the outer end. and (c) an adjusting bolt that is screwed into a female threaded hole of the adjusting nut and engages with the brake shoe web at its head, the inner side of the adjusting nut. An insert made of a material selected from synthetic resin, aluminum, aluminum alloy, and sintered alloy is placed between the end face and the bottom of the bottom hole of the piston, and the outer peripheral surface of the insert and the inner peripheral surface of the bottom hole are connected to each other. The actuating force of the piston is transmitted to the brake via two actuating force transmitting surfaces, each of which is a combination of both end surfaces of the insert, the bottom surface of the bottom hole, and the inner end surface of the adjusting nut. The operating force is transmitted to the shoe web, and at least one of the operating force transmitting surfaces is a conical surface concentric with the bottomed hole.

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

FIG. 1 shows a first embodiment of the present invention, in which a circular bottomed hole 1a extends in the axial direction from the outer end surface of a piston 1 fitted in a wheel cylinder 10, which projects from the wheel cylinder.
An adjusting nut 2 is rotatably fitted into the bottomed hole 1a.

The adjusting nut 2 has a star wheel 2a fixed to the outer end protruding from the piston 1, and a female threaded hole 2b passing through the center in the axial direction. A sting bolt 3 is screwed together.

The adjusting bolt 3 has a notch 3a in its head, which engages with the shoe web 4 and prevents it from rotating. Therefore, when the star wheel 2a is rotated, the adjusting nut 2 and Relative displacement occurs in the axial direction between the adjusting bolt 3 and the shoe clearance is adjusted.

An aluminum alloy insert 5 is inserted between the piston 1 and the adjusting nut 2.

The insert 5 is a member having a circular cross-sectional shape, and one end surface thereof has a conical surface 5a with a protruding central portion.
A circular recess 5c is provided in the center of the other end surface 5b.

On the other hand, a conical recess 1b concentric with the bottomed hole 1a is provided in the center of the bottom of the bottomed hole 1a bored in the piston 1, and the insert 5 has a conical surface 5a in this recess 1b. At the same time, the other end surface 5b abuts the inner end surface of the adjusting nut 2, and is inserted between the piston 1 and the adjusting nut 2 in a sandwiched state.

As a result, the actuation force of the piston 1 is applied to the conical surface 5a and the recess 1.
the inner surface of b, and the end surface 5b and the adjusting nut 2
The motion is transmitted to the shoe web 4 through two motion transmission surfaces formed by each combination of the inner end surfaces.

In this embodiment, the adjusting nut 2 is in direct contact with the piston 1 on its outer peripheral surface.

In order to prevent the adjusting nut 2 and the piston 1 from coming into direct contact, a vibration damping material should be interposed not only between their end faces (between the surfaces perpendicular to the axis) but also between their circumferential surfaces. However, as mentioned above, it is quite difficult to do this within the extremely limited space as a practical matter.

Therefore, as a last resort, we made a prototype insert 5 like the one in this example and investigated its squeal prevention effect, but contrary to expectations, we found that
It has been found that not only does the squeal prevention effect not deteriorate even when the circumferential surfaces of the piston 1 and the adjusting nut 2 come into direct contact, but also that the insert 5 of this example has extremely excellent squeal prevention performance. .

Further, subsequent experiments have revealed that it is effective to make at least one end surface of the insert 5 into a conical shape in order to improve the squeal prevention performance.

In other words, inserting a disk-shaped insert with flat end surfaces between the piston 1 and the adjusting nut 2 can provide a certain degree of noise prevention effect, but as in this embodiment, the insert 5 If one end surface is made into a conical surface 5a and the abutment metal is fitted into the conical recess 1b provided in the piston 1, the squeal prevention performance is further improved, and the frequency of squeal occurrence is reduced by about 1 compared to when the insert 5 is not used. It was confirmed that the value decreased to /2.

The reason for this is not yet completely clear, but the insert 5 is reliably held in the center of the bottomed hole 1a, and there is uniform play between the outer circumferential surface and the inner circumferential surface of the piston 1 over the entire circumference. It is assumed that one of the reasons is that gaps are formed.

Next, in order to concretely demonstrate the effectiveness of the insert of this example, some of the experiments conducted in the process of arriving at the present invention will be shown.

This experiment was conducted on drum brakes in practical use that are particularly prone to squealing, but even so, squealing does not always occur when used in the market, so we An experiment was conducted using a drum brake in which the radius of curvature of the lining surface was made slightly larger than the radius of curvature of the inner peripheral surface of the drum, so that both ends of the shoe were in strong contact with the drum, making it particularly likely to generate squeal. went.

Inserts used in the experiment were made of aluminum alloy as in the above example, as well as inserts made of phenol resin and iron-based sintered alloy.

Figure 3 shows the results of an experiment to investigate the anti-squeak effects of phenolic resin inserts and aluminum alloy inserts.

The experiment was conducted by attaching an insert to a drum brake equipped on an actual vehicle, and varying the combinations of initial braking speed and mask cylinder hydraulic pressure as shown in Figure 4.
At the same time, we also changed the lining temperature before braking to investigate the effect of the lining temperature.

In FIG. 3, marks placed at the intersections of vertical lines and horizontal lines indicate the type and level of the squealing sound, as shown in FIG. 5.

The type and level of the squealing sound was determined by the experimenter's ears, and where no mark was placed at the intersection of the vertical line and the horizontal line, there was no squealing that could be heard by the ear. That's where it was.

Furthermore, a portion where two marks are attached to one intersection point means that two types of squealing sounds are generated.

As is clear from Figure 3, without the insert, noise occurs at most combinations of mask cylinder fluid pressure and initial braking speed, and even at a "small" level, whereas with the insert, When worn, the occurrence rate of squeals is significantly reduced, and "small" level squeals no longer occur.

Furthermore, although the insert is made of phenolic resin, it is clear that the metal, aluminum alloy, can also have a considerable squeal-preventing effect.

Next, the results of an experiment conducted to confirm the effect of selecting the insert shape and mounting position as in the present invention will be shown.

In Fig. 6, the phenolic resin plate is a phenolic resin disc having a hole in the center, and this disc 11 is attached to the adjusting nut 2 as shown in Fig. 7.
It was installed between the star wheel 2a and the piston 1.

As is clear from FIG. 6, even if such a plate 11 is installed, the squeal is less likely to occur than when the star wheel 2a, which is shown as "without plate", is brought into direct contact with the piston 1. There is almost no difference.

In the experiment shown in Fig. 3, the phenolic resin insert had an excellent anti-squeal effect, whereas the plate 11 in the experiment shown in Fig. 6, which was made of the same material, had almost no anti-squeal effect. This clearly shows that installing the insert in the form of the present invention is effective in preventing squealing.

The difference between the experiment shown in Figure 3 and the experiment shown in Figure 6 in the occurrence of squeal under the conditions of "no insert" and "no plate" is due to the drum brake used in the experiment. This is because although they are of the same type, the car models equipped with drum brakes are different.

Figure 8 shows the results of an experiment investigating the anti-squeal effect of an insert made of iron-based sintered alloy.

This experimental result shows that the sintered alloy insert can also provide a certain degree of noise prevention effect.

A second embodiment of the invention is shown in FIG.

Since this embodiment differs from the previous embodiment mainly in the shape of the insert 6, similar parts are given the same reference numerals and explanations will be omitted.

The insert 6 has a hollow ring shape, and one end surface 6
a is a flat surface and comes into contact with the bottom surface of the bottomed hole of the piston 1, which is also a flat surface, and the other end surface is a conical surface 6b and comes into contact with the inner end surface of the adjusting nut 2, which is also a conical surface. There is.

That is, in this embodiment, the operating force transmission surface formed by the combination of the inner end surface of the adjusting nut 2 and the end surface of the insert 6 that abuts thereon is a conical surface concentric with the bottomed hole 1a. As a result, also in this embodiment, the outer circumferential surface of the insert 6 and the inner circumferential surface of the bottomed hole of the piston 1 are separated over the entire circumference.

This example has almost the same noise prevention effect as the previous example, is simple in shape, uses less aluminum alloy, and is therefore inexpensive, and also has a through hole 6C in the center that prevents interference with the adjusting bolt 3. It also has a unique effect that makes it easy to avoid.

In other words, the threaded length between the adjusting nut 2 and the adjusting bolt 3 needs to be greater than a certain value in order to prevent the adjusting bolt 3 from wobbling. 3 can be made to protrude from the adjusting nut 2, so that as the shoe lining wears out, the threaded length between the two will decrease even when the adjusting bolt 3 is retracted. Therefore, it is possible to make the length of the female threaded hole 2b of the adjusting nut 2 the same as the required minimum screwing length, and the adjusting mechanism can be constructed compactly.

As detailed above, the present invention is made of phenolic resin, aluminum and aluminum alloy or sintered alloy,
This is an extremely simple method in which an insert with at least one end surface having a conical surface is inserted with a certain radial clearance between the bottom surface of a bottomed hole drilled in the piston and the inner end surface of the adjusting nut. However, it is effective in effectively preventing drum brake squeal.

Furthermore, since there is no need to interpose the insert between the outer circumferential surface of the adjusting nut and the inner circumferential surface of the bottomed hole drilled in the piston, the piston may be made larger to prevent squealing, and the adjusting nut may be made larger to prevent squealing. There is no need to downsize the nut or adjusting bolt, and the design of a wheel cylinder with a shoe clearance adjustment mechanism does not become more difficult than before.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a main part showing one embodiment of the present invention, and FIG. 2 is a sectional view of a main part showing another embodiment. FIG. 3 is a diagram showing the results of an experiment conducted to confirm the effects of the present invention. FIG. 4 is a diagram showing the experimental conditions in FIG. 3. FIG. 5 is a diagram showing the meanings of marks used in FIG. 3 and FIGS. 6 and 8, which will be described later. FIG. 6 is a diagram showing the results of another experiment conducted to confirm the effects of the present invention. FIG. 7 is a front sectional view of the wheel cylinder used in the experiment shown in FIG. FIG. 8 is a diagram showing the results of an experiment conducted to confirm the effects of the present invention. 1...Piston, 1a...Bottomed hole, 1
b... Concave conical recess, 2... Bent adjusting nut, 2a... Star wheel, 2b... Open threaded hole, 3... Adjusting bolt, 3a...
Song/cutout, 4... Shoe web, 5...
・Insert, 5a... Conical surface, 6...
・Insert, 6b...Conical surface.

Claims (1)

[Scope of Claim for Utility Model Registration] A piston that is fitted into a wheel cylinder and has a circular bottomed hole that is bored in the axial direction from the outer end surface, and that is rotatably fitted into the bottomed hole of the piston. an adjusting nut which is screwed into the female screw hole of the adjusting nut and has a female threaded hole passing through the central part in the axial direction and a star wheel fixed to the outer end; an adjusting bolt that engages with a brake shoe web at a portion of the drum brake, wherein synthetic resin, aluminum, aluminum alloy, An insert made of a material selected from sintered alloys is disposed with a gap between the outer peripheral surface of the insert and the inner peripheral surface of the bottomed hole, and the operating force of the piston is applied to the insert. The actuating force is transmitted to the brake shoe web through two actuating force transmitting surfaces, each of which is a combination of both end surfaces, the bottom surface of the bottomed hole, and the inner end surface of the adjusting nut, and at least one of the actuating force transmitting surfaces. A squeal prevention device for a drum brake for a vehicle, characterized in that a conical surface is concentric with the bottomed hole.