JPH0141856B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a slippage prevention device for an automatic gap adjustment mechanism.

[Prior Art] Conventionally, as an automatic gap adjustment mechanism for drum brakes, a strut placed between a pair of brake shoes is expanded as the lining of the brake shoes wears to limit the return position of the brake shoes. , one that reduces the braking gap has been proposed.
The strut consists of an adjustment nut into which one end of an adjustment bolt having a ratchet in the center is screwed, and a socket member into which the other end shaft of the adjustment bolt is rotatably fitted. If the frictional resistance of the threaded part between the adjustment nut and adjustment bolt is small, even if the strut is extended when the brake is applied, the adjustment lever that engages with the ratchet wheel integrated with the adjustment bolt will be returned by the force of the return spring when the brake is released. , the adjustment bolt may become tangled and the braking clearance may no longer be adjusted.

[Problems to be Solved by the Invention] The purpose of the present invention is to solve the above-mentioned problems.
Increasing the frictional resistance at the threaded joint between the adjustment nut and adjustment bolt that connect the strut so that it can extend,
To provide a slipback prevention device for an automatic gap adjustment mechanism in which a ratchet wheel of an adjustment bolt that engages with an adjustment lever is rotated only in the direction of extending the strut, and is not rotated in the opposite direction.

[Means for solving the problems] In order to achieve the above object, the present invention has the following configurations:
A strut, which is engaged between the webs of the pair of brake shoes so as not to be movable in the longitudinal direction of the webs, is connected to an adjustment nut that screws one end of an adjustment bolt with a ratchet in the center, and a shaft of the other end of the adjustment bolt. and a socket member rotatably fitted into the strut, in which the adjustment bolt is screwed out from the adjustment nut by rotation of an adjustment lever that engages with the ratchet wheel, and a spring that extends from the end of the adjustment nut in a direction intersecting the axis of the strut. is engaged with the web of the brake shoe that engages with the adjustment nut or the brake lever, thereby increasing the frictional resistance at the threaded portion between the adjustment nut and the adjustment bolt.

[Function] When the brake is released, when the adjustment lever 16 passes over the pawl of the ratchet wheel 18, the adjustment bolt 19 is also subjected to a force that reverses the ratchet wheel 18 (returning force). This is canceled out by the frictional resistance of the threaded portion between the adjusting nut 26 and the adjusting bolt 19, and the adjusting bolt 19 is not rotated.

The spring 23 uses the engaging portion between the adjusting nut 26 and the web 3 of the right brake shoe as a fulcrum, and exerts a force to push up the left end side of the adjusting nut 26, so as to push up the left end side of the adjusting nut 26 relative to the threaded portion between the adjusting nut 26 and the adjusting bolt 19. It has the effect of preventing spiral movement.

[Embodiment of the Invention] As shown in FIG. 1, a drum brake includes a back plate 14 that is fixed to a non-rotating part of a vehicle and closes the open end of the brake drum, a pair of brake shoes 6, and The hydraulic cylinder device 1 is configured to use one end of the brake shoe 6 as a fulcrum, push out the other end of the brake shoe 6, and press it against the inner circumferential surface of the brake drum.

The back plate 14 is provided with a hole 22 in the center through which the axle passes, the hydraulic cylinder device 1 is fixedly supported in the upper part, and the anchor member 11 is fixed by a rivet 10 in the lower part.

The brake shoe 6 is formed by bonding a lining 5 to the outer surface of a rim 4 made of a band plate curved into an arc shape, and by welding a web 3 made of a crescent-shaped plate to the inner surface. The central part of the web 3 is supported by the back plate 14 by the guide device 8, the upper end is engaged with the end groove of the piston 2 of the hydraulic cylinder device 1, and the lower end is engaged with the end groove of the anchor member 11. be done. In order to obtain such an engaged state, the return spring 2 is attached to the upper part of the web 3 of the pair of brake shoes.
5, and a spring 12 is stretched across the lower part thereof.

The guide device 8 is constructed by passing the tip of a pin vertically disposed on the back plate 14 through an elongated hole in the web 3, and inserting a coil spring between the web 3 and a seat plate that is engaged with the tip of the pin. Due to the force, one side edge of the rim 4 is pressed against the back plate 14.
It is slidably and lightly pressed against the plate surface.

The automatic gap adjustment mechanism according to the present invention consists of an extendable strut 20 disposed between a pair of brake shoes and an adjustment lever 16 for extending the strut 20. The strut 20 consists of an adjustment nut 26, an adjustment bolt 19, and a socket member 17. The right end of the adjustment bolt 19 in FIG. The shaft portion on the left end side of the ratchet wheel 18 is rotatably fitted into the shaft hole of the socket member 17. An adjustment lever 16 for rotating the ratchet wheel 18 is engaged with the ratchet wheel 18 and is connected to the support shaft 24.
is supported by the web 3 of the left brake shoe 6. The adjustment lever 16 is formed from a plate material, and has an arm that extends downward so that the arm 16a that extends upward abuts against the left end portion of the socket member 17. A spring 15 is stretched between the web 3 and the web 16b. An arm 16c extending rightward from the adjustment lever 16 is engaged with the ratchet wheel 18.

A plate-shaped brake lever 9 is superimposed on the back side of the web 3 of the right brake shoe 6, the upper end of which is rotatably supported by the web 3 by a support shaft 7, and the central part is connected to the adjustment nut 26 of the strut 20. The protruding piece 9a at the lower end is pressed against the inner surface of the rim 4, and the brake lever 9 cannot rotate counterclockwise about the support shaft 7 any more.

As can be seen from the above structure, the left end of the strut 20 is bifurcated by the split groove, and is engaged with the left brake shoe web 3 and the adjustment lever 16 so as to hold them from both sides. Ru. The right end of the strut 20 is also bifurcated and is engaged with the web 3 of the right brake shoe and the brake lever 9 so as to hold them from both sides. Each web 3 is also provided with a notch, which is engaged with the end groove of the strut 20,
Therefore, the struts 20 cannot be moved in the longitudinal direction of the web 3.

An important feature of the invention is that between the end of the adjusting nut 26 of the strut 20 and the brake lever 9,
The spring 2
3 is passed over. The spring 23 tilts the adjusting nut 26 about the engagement portion with the web 3 as a fulcrum, thereby increasing the frictional resistance of the threaded engagement portion with the screw shaft 19.

Next, the operation of the device of the present invention will be explained. When the brake is applied, when pressure fluid is supplied to the inside of the hydraulic cylinder device 1, the pair of pistons 2 protrude outward, and the pair of brake shoes 6 are pushed apart at their upper ends with their lower ends as fulcrums, and the brake drum is pressed against the inner circumferential surface of the brake to generate braking force. The adjustment lever 16 is rotated clockwise about the support shaft 24 by the force of the spring 15, and the arm 16a pushes the strut 20 to the right, so that it follows the brake shoe 6 on the right side. As the adjustment lever 16 rotates, the ratchet wheel 1
8 is rotated, the strut 20 is extended, the return position of the brake shoe is limited, and the braking gap is reduced.

When the brake action is released, the pair of brake shoes 6 are returned inward by the force of the return spring 25.
The strut 20 stops when its left end collides with the web 3 of the left brake shoe. At this time,
The adjustment lever 16 is rotated counterclockwise about the support shaft 24, passes over the pawl of the ratchet wheel 18, and falls between the pawl and the next pawl.

When the adjustment lever 16 passes over the pawl of the ratchet wheel 18, the adjustment bolt 19 is also subjected to a force that reverses the ratchet wheel 18 (a reversing force). This is canceled out by the frictional resistance of the threaded part with the adjustment bolt 1.
9 is not rotated. In other words, the spring 23 uses the engaging portion between the adjusting nut 26 and the web 3 of the right brake shoe as a fulcrum to exert a force to push up the left end side of the adjusting nut 26, and the spring 23 exerts a force to push up the left end side of the adjusting nut 26, and the screwing portion between the adjusting nut 26 and the adjusting bolt 19 exerts the effect of hindering relative spiral movement.

In addition, when the brake is applied and released, if the braking gap is at an appropriate value, the adjustment lever 16
The amount of rotation about the support shaft 24 is small, and the arm 16c only moves freely between the same pawls of the ratchet wheel 18, and does not perform any braking gap adjustment action.

Next, when applying the parking brake, when the lower end of the brake lever 9 is pulled to the left, the left brake shoe 6 is pushed out by the middle part of the brake lever 9 via the strut 20, and the inner periphery of the brake drum is expanded. pressed against the surface. When the brake lever 9 is further pulled, the upper end of the brake lever 9 moves to the right using the engagement part with the right end of the strut 20 as a fulcrum, and the right brake shoe 6 is moved to the brake drum via the support shaft 7. It is pressed against the inner peripheral surface and generates braking force. In this case, the adjustment lever 16
does not rotate and does not perform braking gap adjustment action.

In addition, in the embodiment of the present invention, the spring 23 is hung between the adjustment nut 26 and the brake lever 9, but
A spring 23 may be applied between the adjusting nut 26 and the right brake shoe 6.

[Effects of the Invention] As described above, in the present invention, the strut, which is engaged between the webs of a pair of brake shoes so as not to be movable in the longitudinal direction of the webs, controls one end of the adjustment bolt having a ratchet in the center. The adjustment nut is composed of an adjustment nut that is screwed together and a socket member that rotatably fits the other end shaft of the adjustment bolt, and the adjustment bolt is screwed out from the adjustment nut by rotation of an adjustment lever that engages with a ratchet wheel. A spring extending from the end of the strut in a direction intersecting the axis of the strut is engaged with the web of the brake shoe or brake lever that engages with the adjustment nut, thereby increasing the frictional resistance at the threaded portion between the adjustment nut and adjustment bolt. Because of this, the adjusting bolt will not be dragged back by the return movement of the adjusting lever that engages with the ratchet wheel of the adjusting bolt and rotates the adjusting bolt.

In other words, the adjustment bolt rotates in a direction that extends the strut in response to rotation of the adjustment lever, and does not rotate in response to return rotation of the adjustment lever. Therefore, the braking gap once adjusted will not be reset, and even if the lining is worn, a proper braking gap will always be maintained.

[Brief explanation of drawings]

FIG. 1 is a front view of a drum brake equipped with a sagging prevention device of an automatic gap adjustment mechanism according to the present invention. 1: Hydraulic cylinder device, 6: Brake shoe,
7: Support shaft, 9: Brake lever, 11: Anchor member, 14: Back plate, 15: Spring, 16: Adjustment lever, 17: Socket member, 18: Ratchet wheel, 19: Adjustment bolt, 20: Strut, 23: spring, 2
4: Support shaft, 25: Return spring, 26: Adjustment nut.

Claims (1)

[Claims] 1. A strut that is engaged between the webs of a pair of brake shoes so as not to be movable in the longitudinal direction of the webs is connected to an adjustment nut that screws one end of an adjustment bolt that has a ratchet in the center, and the other end of the adjustment bolt. A socket member that rotatably fits the shaft part, and in which the adjustment bolt is screwed out from the adjustment nut by rotation of the adjustment lever that engages with the ratchet wheel, from the end of the adjustment nut in a direction that intersects with the axis of the strut. An automatic gap adjustment mechanism characterized in that an extending spring is locked to a web of a brake shoe that engages with an adjustment nut or to a brake lever to increase frictional resistance at a threaded portion between the adjustment nut and adjustment bolt. Anti-return device.