JPS6154971B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a drum brake device installed in an automobile or the like.

In general, there are two types of automobile brake systems: drum brake systems and disc brake systems. Disc brake systems are good brake systems because they have good feeling and do not require clearance adjustment due to wear like drum brake systems do. . However, the disc brake device has a disadvantage in that it suffers from severe wear because the load per braking area is large. In addition, drum brake devices not only have poor feeling, but also require adjustment of the gap between the braking surface and the brake shoe, or the installation of an automatic gap adjustment device, as well as heat dissipation. It had the disadvantage of having poor performance and overheating.

In order to eliminate these drawbacks, an X-shaped cross section is formed around the brake disc, and a pair of wedge-shaped brake shoes are disposed in a pair of axially facing V-shaped grooves. A brake device having a braking friction surface of a V-shaped groove in which cooling fins are formed on opposing wall surfaces of the V-shaped groove has been proposed (for example, US Pat. No. 3,237,732).

However, in such a brake device, it is difficult for the cylinder surface that presses the brake lining to press the entire surface of the brake lining uniformly.
Therefore, when the brake lining is pressed into the V-shaped groove, the edge of the brake lining vibrates, causing a so-called brake squeal phenomenon.

In addition, in cold regions where there is a lot of snow, snow-melting agents are sprayed to melt snow on roads. Such snow-melting agents act on the brakes, causing rust on the brake friction surfaces, causing problems such as vibrations and reduced braking force when the brakes are used.

This invention is a drum brake device made in view of the above, which generates a large braking force, does not require gap adjustment, suppresses brake squeal phenomenon, and has less rust on the braking friction surface. The purpose is to provide

The gist of the invention is to fit an end face of a brake drum and a braking member in the axial direction with an annular V-shaped uneven surface, and to attach the annular braking member to an annular wheel cylinder formed concentrically with the braking member. The V-shaped angle is formed so that the braking member naturally separates from the brake drum when the pressure in the wheel cylinder is released.

The structure of the present invention will be explained below with reference to the illustrated embodiments. In FIGS. 1 and 2, 1 is a wheel disk, 2 is a brake drum, and 3 is an axle shaft, which are integrally connected by bolts and nuts as shown. Cooling fins 4 are formed on the shoulder portion of the brake drum 2, and a V-shaped groove 5 is formed in an annular shape on the end surface of the cylindrical portion. It is formed in an annular shape opposite to the V-shaped groove 5 so as to be in close contact with the V-shaped groove 5,
A brake member 6 having a V-shaped cross section is attached, and the brake member 6 is made of a material having a high coefficient of friction, such as asbestos. The V-shaped groove 5 is formed so that 1/2 of the V-shaped angle is a predetermined angle larger than the friction angle corresponding to the friction coefficient between the V-shaped groove 5 and the braking member. This friction angle α is the friction angle formed between the pressing direction of the braking member 6 and the friction surface, and there is a relationship of α=tan ⁻¹ μ, where μ is the friction coefficient of the friction surface. In the case of asbestos, the friction coefficient μ is, for example, 0.35, so α≒19°.

Therefore, 1/2 of the V-shaped angle of the V-shaped groove 5 is larger than the friction angle 19°=α corresponding to the friction coefficient between the V-shaped groove 5 and the braking member 6, that is, 30° in the embodiment.
They are formed at the same time, and are formed so that when the force pressing the braking member 6 against the V-shaped groove 5 is released, the two are naturally released from the close contact. Braking member 6
is fixed to an annular brake ring 7 over its entire circumference (vertical surface in FIG. 1), and the brake ring 7 has an opening 7a that communicates the inside of the brake drum 2 with the outside air, is slidably fitted in the housing 9 in the axial direction via spline means 8, the housing 9 is fixed to an axle housing 10, the axle housing 10 is connected to the vehicle body via an elastic body (not shown), and the axle shaft 3 is pivotally supported by a bearing mounted on the housing 9. An annular piston 11 is concentrically integrally formed on the boss portion of the brake ring 7 on the opposite side to the braking member 6, and this piston 11 is connected to an annular cylinder 1 fixed to the housing 9.
2, and seal members 13 and 14 are fitted on both the inner and outer sides of the opening of the annular cylinder 12, and the piston 11, cylinder 12, and seal members 13 and 14 are arranged concentrically with the braking member 6. An annular wheel cylinder 15 is constructed, and is connected by a conduit P to a master cylinder (not shown). Reference numeral 16 denotes a parking brake lever, which is formed into a bifurcated shape, is erected in the radial direction at a symmetrical position with respect to the axle shaft 3, and is supported by support shafts 17, 17 fixed to the housing 9;
The forked tips each face the brake ring 7,
A connecting rod 18 is pivotally attached to the base end, and when the rod 18 is pulled to the left in FIG.
When the lever 8 is loosened, the parking brake lever 16 is returned to its original position by the force of a spring (not shown). Note that numerals 19 and 20 are the same flexible seal members, numerals 21 and 22 are dust prevention covers, and numeral 23 is a retaining ring.

Next, the operation of the device of this invention will be explained.
When the brake pedal (not shown) is depressed and the oil pressure of the master cylinder described above acts on the wheel cylinder 15, the piston 11 is pressed, and the braking member 6 is pressed against the V-shaped groove 5 via the brake ring 7. Then, due to the wedge principle, the V-shaped groove 5 and the braking member 6
A large amount of pressure is generated on the friction surface, which generates a large braking force. When the brake pedal is released, the oil pressure in the wheel cylinder 15 disappears, and the piston 11 returns slightly together with the brake cylinder 7 under the retraction action of the seal members 13 and 14. Therefore, the brake member 6 also returns and leaves the V-shaped groove 5. In this case, since 1/2 of the V-shaped angle of the V-shaped groove is larger than the friction angle corresponding to the friction coefficient between the V-shaped groove and the braking member, the braking member 6 quickly
Move away from the groove. When the braking member 6 or the V-shaped groove 5 wears out, the brake ring 7 correspondingly
Since it moves to the right in the figure, there is no need to adjust the gap like in a normal drum brake device.

Further, the annular braking member 6 that presses against the V-shaped groove is
The entire back surface is fixed to the annular brake ring 7 and is evenly pressed against the annular wheel cylinder 15, and since all braking-related members are annular in this way, brake squeal is suppressed.

Furthermore, since the annular braking member 6 is disposed oppositely so as to be in close contact with the entire surface of the V-shaped groove 5, which is the braking friction surface, the V-shaped groove 5 is less susceptible to the influence of snow melting agents and the like. There is little rust on the 5 groove surfaces.

According to this invention, as described above, the annular braking member having the V-shaped groove and the V-shaped cross section of the brake drum is fitted in the axial direction, and the V-shaped angle quickly separates when no pressing force is applied between them. The braking area is large, so the load per area is small, so the degree of wear is low.The cylindrical part of the brake drum is short, and the shoulder part is provided with cooling fins. Since outside air flows into the brake drum 2 through the Since it occurs on the cylindrical end surface rather than the circumferential surface, it has a good feeling like a disc brake device. Brake squeal is suppressed by the annular braking member and the annular wheel cylinder, and since the structure is not easily affected by snow melting agents, stable braking force can be obtained with extremely little rust on the V-shaped groove surface. In addition, in the present invention, the brake member side can be formed with a V-shaped groove, and the end surface of the cylindrical portion of the brake drum can be formed with a V-shaped convex portion that fits into the V-shaped groove.

[Brief explanation of the drawing]

The figures show an embodiment of the invention, with FIG. 1 being a longitudinal sectional view and FIG. 2 being a partially sectional front view. 2... Brake drum, 5... V-shaped groove, 6...
Braking member, 7...Brake ring, 15...Wheel cylinder.

Claims (1)

[Claims] 1 One side of the cylindrical end surface of the brake drum and a braking member formed in an annular shape facing the cylindrical end surface in the axial direction has a V-shaped groove, and the other side has a shape that fits into the V-shaped groove. such that 1/2 of the V-shaped angle of the V-shaped groove is a predetermined angle larger than the friction angle corresponding to the friction coefficient between the V-shaped groove and the member fitted thereto. A drum brake device characterized in that the braking member is configured to be connected to an annular wheel cylinder mounted concentrically with the braking member.