JPS6314110Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to an automatic brake shoe gap adjustment device that prevents over-adjustment.

As shown in FIG. 1, the internal expansion type brake has semicircular brake shoes 2 facing each other in an arc shape along the inner surface of a back plate 1, and a return spring with support pieces 3 and hydraulic expanders 4 sandwiched at both ends. It is loaded with 5. The brake shoe 2 is expanded by the operation of the expander 4, and the lining 6 is brought into pressure contact with the brake drum 7 to brake it. In this internal expansion type brake, the gap between the lining 6 and the brake drum 7 is set appropriately in order to stabilize the control operation of the brake pedal, etc., and the above-mentioned appropriate value is always maintained as the lining 6 wears. is equipped with an automatic gap adjustment device.

FIG. 2 shows a conventional brake shoe gap automatic adjustment device. It is a so-called friction type auto adjuster, and the brake shoe 2
A long hole 9 is provided in the web 8, a bolt 11 is inserted with a flat washer 10 on both sides of the hole, and is tightened with a nut 13 via the web washer 12. The flat washer 10 is elastically installed on both sides of the web 8 so as to apply an appropriate frictional force to the web. A locking pin 14 extends from the tip of the bolt 11, and loosely fits into a locking hole 16 of a buckle 15 fixed to the back plate 1. Locking hole 1
The dimensional difference T between the inner diameter of the locking pin 6 and the outer diameter of the locking pin 14 becomes the regulation dimension of the gap t between the lining 6 and the brake drum 7.

That is, when the brake shoe 2 expands from the state shown in the figure, the locking pin 14 moves integrally by a dimension T and stops on the opposite side of the locking hole 16. If the gap t is larger than that, the flat washer 10 and the web 8 will slip and the lining 6 will come into contact with the brake drum 7. When the brake is released and the brake shoe 2 is returned by the return spring 5, it returns by a dimension T together with the locking pin 14.
= A gap of t opens. The force of the return spring 5 is set to be smaller than the frictional force between the flat washer 10 and the web 8, and the gap t is maintained at the dimension T.

However, high fluid pressure acts on expander 4,
When the brake drum 7 elastically deforms and expands, an overadjustment occurs in which the brake shoe gap is adjusted accordingly, and the gap t when it returns to its original state becomes smaller by that amount. Therefore, it is necessary to set a large gap in advance, which causes the problem that the stroke of a normal braking operation becomes large and the feeling deteriorates.

In order to solve the above-mentioned problem, this invention prevents over-adjustment by moving the button together with the brake shoe when a high enough hydraulic pressure is applied to change the elasticity of the brake drum. An object of the present invention is to provide an automatic brake shoe clearance adjustment device that prevents brake shock.

A preferred embodiment of this invention will be described below.

FIG. 3 shows the main parts of the automatic brake shoe gap adjustment device of this invention, and the parts that are the same as those of the conventional type shown in FIGS. 1 and 2 are designated by the same reference numerals and their explanation will be omitted.

In this invention, the buckle 17 provided with the locking hole 16 for loosely fitting the locking pin 14 is in the form of a lever that is pivotably supported by a shaft pin 18 implanted in the back plate 1, and is in contact with the inner edge. A stopper 19 is placed and strongly elastically contacted with the stopper 19 by an overload spring 20. The functions of the bat 17 and the locking hole 16 which are kept stationary in this state are completely the same as those of the conventional one shown in the second figure.

Next, a bell crank 21 is pivotally supported on the back surface of the brake shoe web 8, and one end 21a of the bell crank 21 is brought into light contact with the inside of the tip of the batch 17 by the force of a torsion spring 22. On the other hand, a gear 24 is pivotally supported in contact with the tip end surface of the piston 23 of the expander 4, and the tip of this support shaft 25 is expanded with a stepped portion. The tip of the portion 26 is in contact with the brake shoe 2. When the piston 23 is pushed out to push the brake shoe 2 open, the gear 24 is clamped between the tip end surface of the piston and the stepped portion of the enlarged portion 26. Other end 2 of bell crank 21
1b engages with the teeth at the lower part of the kia 24.

The above configuration works as follows.

When the brake is operated with normal low hydraulic pressure, the gear 24 is clamped by the force and a braking force is applied.
On the other hand, due to the expansion of the brake shoe 2, the bell crank 21 pivotally supported thereon is about to rotate relative to the counterclockwise direction in FIG.
pushes the button 17 outward. However, since the overload spring 20 acts strongly inward on the batch 17, the bell crank 21 is swung in the direction of the arrow, and the force exceeds the braking force, causing the other end 21b to rotate the gear 24. make it move. That is, the batch 17 remains stationary, and the gap is automatically adjusted as before. When the braking operation is completed, the braking force of gear 24 also disappears,
The bell crank 21 is returned to its original position by a torsion spring 22.

If high hydraulic pressure acts on the expander 4 and the brake drum 7 is elastically deformed to further expand the brake shoe 2 even after the lining 6 contacts the brake drum 7, the braking force of the gear 24 will also act strongly. , prevents the bell crank 21 from swinging in the direction of the arrow, so that the one end 21a allows the batch 17 to swing outward against the force of the overload spring 20.
This allows the locking pin 14 to freely move outward, preventing slippage between the flat washer 10 and the web 8, and preventing over-adjustment.

The one in FIG. 4 shows the support shaft 28 of the bell crank 27.
is placed on the line of action of the piston 23, one end 27a is brought into contact with the batch 17, the other end 27b is shaped into a segment centered on the support shaft 28 and brought into contact with the tip end surface of the piston 23, and a braking force is applied between them. Eggplant. As a result, when high hydraulic pressure is applied, the bell crank 27 is strongly braked and the batch 17 is swung against the force of the overload spring 20, thereby preventing over-adjustment as described above.

As described above, the brake shoe gap automatic adjustment device according to this invention is provided with swingable butts used in a friction adjuster and held in a fixed position by elastic force, and when high hydraulic pressure is applied, the brake shoe gap is adjusted. This system uses a bell crank that is pivotally supported on the brake shoe to prevent overadjustment by responding to the movement of the brake shoe.It has the same effect as before during normal braking and the same effect during high hydraulic pressure. The over-adjustment prevention effect is automatically switched and the adjustment function is improved. Therefore, there is no variation in the gap due to hydraulic pressure, so the set gap size can be made small, the petal feeling is improved, and the play stroke can be made small, so there are effects such as good responsiveness and increased reliability during emergency braking.

[Brief explanation of the drawing]

Figure 1 is a front view of an internal expansion type brake equipped with a conventional brake shoe clearance automatic adjustment device, Figure 2 is an enlarged cross-sectional view taken along arrow A-A in Figure 1, and Figure 3 is a front view of an inwardly expanding brake equipped with a conventional brake shoe clearance automatic adjustment device. FIG. 4 is a front view of the main parts showing one embodiment of the automatic brake shoe gap adjustment device, and FIG. 4 is a front view of the main parts showing another embodiment of the same. 1... Back plate, 2... Brake shoe, 4... Expander, 7... Brake drum, 8... Web, 10... Flat washer, 14...
...Latching pin, 16...Latching hole, 17...Batch,
19...stopper, 20...overload spring, 21, 27...bell crank, 23...
piston.

Claims (1)

[Scope of utility model registration request] A flat washer is in elastic contact with both sides of the brake shoe web so that it can slide with a predetermined frictional force, and the tip of the locking pin inserted through the flat washer is inserted into the locking hole of the bat fixed to the back plate with a predetermined gap. In the automatic brake shoe gap adjustment device that is fitted,
The bat is made into a lever shape, and a stopper is provided oppositely to support it on a back plate so that it can only swing outward, and the bat is held in a fixed position by being brought into elastic contact with the stopper by an overload spring. Further, a bell crank is pivotally supported on the brake shoe web, one end of which is brought into contact with the inside of the tip of the bat by a light spring, and an expander is provided at the other end of the bell crank to push the brake shoe. The expanding force is configured to apply a frictional braking force that restrains the rotation of the bellcrank about its support shaft, and the button pressing force of the bellcrank due to the action of the frictional braking force is the spring force of the overload spring. 2. An automatic brake shoe clearance adjustment device, characterized in that, when the brake shoe overcomes the force of the overload spring, the bell crank moves together with the brake shoe against the spring force of an overload spring.