JPH0151703B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an automatic braking gap adjustment device disposed within a wheel cylinder of a hydraulically operated brake.

[Conventional technology]

As shown in FIG. 3, this type of braking gap automatic adjustment device is constructed by fitting pistons 2 and 3 facing each other through openings at both ends of a wheel cylinder 1 in a fluid-tight and movable manner, and between pistons 2 and 3. A hydraulic pressure chamber 4 is defined in the hydraulic pressure chamber 4, and an adjusting bolt 5 and an adjusting nut 6 which are screwed together with a multi-thread screw are arranged in the hydraulic pressure chamber 4, and the clutch portion 5a of the adjusting bolt 5 is formed into a piston. On the other hand, rotation is regulated by the adjusting nut 6 and a spring 7 whose one end is fixed to the piston 3, and the end surface of the adjusting nut 6 is brought into contact with the opening 3b of the adjusting bolt insertion hole 3a formed in the piston 3. , when a braking gap of more than a predetermined value occurs, the adjuster bolt 5 is screwed to move the pistons 2 and 3 forward respectively, thereby ensuring that the braking gap is always constant and also reducing the hydraulic pressure of more than a predetermined value. When this occurs, there is a system in which the piston 3 and the adjusting nut 6 are separated from each other to prevent excessive adjustment.

[Problem that the invention seeks to solve]

However, in the above configuration, the adjustment bolt is assembled into the adjustment bolt insertion hole formed in the piston via the adjustment nut that is screwed onto the adjustment bolt and comes into contact with the opening of the insertion hole. It took a long time to bleed the air.

Therefore, it is an object of the present invention to quickly bleed air from the adjuster mechanism.

[Means for solving problems]

In order to achieve the above object, the present invention disposes an adjusting mechanism in a hydraulic chamber defined by a piston fluid-tightly and movably fitted into a wheel cylinder and an opposing portion of the piston, and In an automatic braking gap adjustment device for a hydraulically operated brake, in which a piston is advanced by an adjusting mechanism when a braking gap of It is externally fitted on the shaft extending from the head so that it can slide in the axial direction and rotate integrally,
The clutch is characterized in that it is comprised of a bolt portion that is threaded into a female threaded portion formed in the axial direction of the piston, and a resilient means that brings the bolt portion and the clutch head into contact with each other.

[Effect]

With this configuration, a flow path is formed between the bottom of the internal thread of the piston into which the bolt part of the adjustment bolt is screwed and the hydraulic pressure chamber, and the residual air at the bottom is quickly exhausted from the hydraulic pressure chamber to the outside. be able to.

〔Example〕

An embodiment in which the present invention is applied to a reading training type drum brake will be described with reference to FIG.

Back plate fixed to the vehicle body (not shown)
In the wheel cylinder 10 disposed in the cylinder body 11 , pistons 13 and 14 are fitted into a cylinder hole 12 formed through the cylinder body 11 so as to be movable in a fluid-tight manner through openings at both ends thereof. A hydraulic chamber 15 is defined between both pistons 13 and 14, and communicates with a master cylinder (not shown) via a liquid supply port 16.

The outer ends of the pistons 13, 14 located outside the cylinder holes 12 are fitted with boots 17, 17, one end of which is fitted onto the outer periphery of the cylinder body 11, and the other end edges of the boots 17, 17 are fitted into the outer ends of the pistons 13, 14, respectively. Contact portions 19 and 20 of the brake shoe 18 are formed,
An adjusting bolt 21 is provided between the piston 13 and the piston 14.

A small-diameter stepped portion 22 for mounting a piston cup is provided on the body portion of the piston 13 on the hydraulic pressure chamber side in the cylinder hole 12;
From this, a medium-diameter step portion 23 with a larger diameter than the step portion 22 and a flange portion 24 are formed at the innermost end on the inner edge, and a piston cup 25 is externally fitted onto the small-diameter step portion 22 for piston cup mounting to form a cylinder. The cup chamber 2 is fitted into the hole 12, and the cylinder hole 12 and the medium-diameter stepped portion 23 form the cup chamber 2.
6.

Furthermore, the piston 1 is located at the axial center of the piston 13.
A medium diameter hole 27 defining a hydraulic chamber 15 between the piston 13 and the piston 13 is bored from the inner end to the outer end of the piston 13. A tapered clutch surface 29 is formed at the back of the adjusting bolt mounting hole 28, which is drilled toward the outer end side, and the medium diameter stepped portion 23 communicates the hydraulic pressure chamber 15 and the cup chamber 26. A communication hole 30 is provided.

The piston 14 has a small-diameter stepped portion 31 for mounting a piston cup on the body portion on the hydraulic pressure chamber side in the cylinder hole 12;
As a result, a medium diameter step part 32 and a flange part 33 having a larger diameter than the step part 31 are formed on the inner end side, and the innermost end of the piston 14 is provided with the medium diameter hole 2 of the piston 13.
A small diameter portion 34 defining a hydraulic chamber 15 is formed opposite to the piston cup 7, and a piston cup 35 is externally fitted to the small diameter portion 31 for piston cup mounting, and is inserted into the cylinder hole 12. A cup chamber 36 is defined by the stepped portion 32 .

Furthermore, an axial adjustment bolt insertion hole 37 is bored in the axial center of the piston 14 from the inner end toward the outer end.
A multi-thread female thread 38 is provided at the inlet portion of the hole 7 to be screwed into the adjustment bolt 21, and a communication hole 39 is provided in the medium diameter stepped portion 32 to communicate the cup chamber 36 and the adjustment bolt insertion hole 37. ing.

The adjustment bolt 21 has a clutch head 42 which has a tapered clutch surface 40 that comes into contact with a clutch surface 29 formed on the piston 13, and a cup seal mounting portion 41 adjacent to this clutch surface 40.
and a shaft portion 43 extending from the clutch head 42;
A bolt portion 44 that is fitted onto the shaft portion 43, a retaining ring 45 that is locked to the tip of the shaft portion 41, and the bolt portion 4
4 and a spring 46 which brings the bolt part 44 and the clutch head 42 into contact with each other. The shaft portion 43 has a cylindrical cross section with flat upper and lower surfaces, and the bolt portion 44 has an insertion hole 44a with a slightly larger diameter than the shaft portion 43 inside, and a multi-thread male thread 47 on the outer periphery. and the shaft portion 43
It is fitted onto the outside of the clutch so that it can slide in the axial direction and rotate integrally with the shaft part 43, and defines a hydraulic fluid flow path 48 between the shaft part 43 and the insertion hole 44a, and a hydraulic fluid flow path 48 between the shaft part 43 and the insertion hole 44a. A flow path 49 is formed in the hydraulic fluid flow path 48 and the hydraulic pressure chamber 15 to communicate with each other.

The bolt part 44 of the adjustment bolt 21 is screwed into the female thread 38 of the adjustment bolt insertion hole 37 of the piston 14, and the cup seal 50 is attached to the cup seal attachment part 41 of the clutch head 42, and the adjustment bolt of the piston 13 is attached. It is installed in the hole 28, and the clutch surface 40 of the adjusting bolt 21 and the clutch surface 29 formed on the piston 13 are brought into contact.

With this configuration, the piston 14
The bottom of the adjustment bolt insertion hole 37 and the hydraulic pressure chamber 1
5, the remaining air at the bottom of the insertion hole 37 can be quickly discharged.

The operation of the automatic braking gap adjustment device configured as follows will be explained.

The pistons 13 and 14 are moved in the braking direction by the pressure fluid introduced into the hydraulic chamber 15 of the wheel cylinder 10, and the brake shoes 18 and 18 are expanded, and the brake lining 18a of the brake shoes 18 and 18 is opened. , 18a are brought into pressure contact with the inner peripheral surface of a rotating brake drum (not shown), and the braking action is performed by the frictional force thereof, provided that the braking gap between the brake drum and the brake linings 18a, 18a is within an appropriate range. In this case, the moving distance of piston 13 and piston 14 is
However, if the wear of the brake lining progresses and the braking gap becomes wider than the appropriate range, the distance traveled by the pistons 13 and 14 during braking will be within the amount of backlash caused by the multi-thread screw engagement of the piston 14. The amount of backlash becomes larger than the amount of backlash caused by the hydraulic pressure, and as the adjusting bolt 21 tries to move together with the piston 14, the contact between the clutch surface 40 of the adjusting bolt 21 and the clutch surface 29 of the piston 13 becomes loose, and the adjusting bolt 21 is moved by the action of hydraulic pressure. The clutch surface 40 is screwed out until it comes into contact with the clutch surface 29 of the piston 13 again, and the return positions of the pistons 13 and 14 are automatically adjusted to move in the braking direction to maintain a proper braking gap.

When the hydraulic pressure exceeds a predetermined value, the bolt portion 44 of the adjusting bolt 21 moves in the axial direction against the biasing force of the spring 46 to maintain contact with the clutch head 40. I try not to make too many adjustments.

FIG. 2 shows another embodiment of the present invention, in which an adjusting bolt 60 has a bifurcated shaft portion 64 extending from a clutch head 63 having a clutch face 61 and a cap seal mounting portion 62. A hollow bolt part 65 is fitted onto this forked shaft part 64, one end is hooked to a retainer 66 at the outer end of the bolt part 65 within the hollow part 65a of the bolt part 65, and the other end is attached to the forked shaft part 65. 64
A spring 69 is disposed to engage a pin 68 inserted through a pin hole 67, so that the clutch head 63 and bolt portion 65 are brought into contact with each other.

The pin 68 has one end protruding from the shaft part 64 and engages with the notch part 65b of the bolt part 65, so that the bolt part 6
5, and between the notch 65b and the clutch head 63 there is a hollow part 65b and a hydraulic chamber 1.
5 is formed.

With this configuration, the air in the adjustment bolt insertion hole 37 can be quickly vented as in the embodiment described above, the braking gap can be automatically adjusted, and the length of the cylinder can be made shorter than in the embodiment described above. Can be done.

In both of the above embodiments, the cup seal 50 of the adjusting bolt is disposed at the inner peripheral position or toward the outer end of the piston cup 25 of the piston 13, so that the cup seal 50 is formed inside the piston cup mounting portion 22 of the piston 13. Pressure fluid can be introduced into the adjusting bolt insertion hole 28, and the hydraulic pressure of the hydraulic fluid applied to the piston cup mounting portion 22 is the same on the inside and outside, reducing the wall thickness of the piston cup mounting portion 22. be able to.

Further, although the above embodiments have been described using a leading/trailing type drum brake, the present invention can of course be applied to a two-leading type or a dual-servo type drum brake.

〔Effect of the invention〕

As described above, the present invention disposes an adjusting mechanism in a hydraulic pressure chamber defined by a piston fluid-tightly and movably fitted into a wheel cylinder and an opposing portion of the piston, and provides a braking gap greater than a predetermined value. In an automatic braking gap adjustment device for a hydraulically operated brake in which a piston is advanced by an adjust mechanism when a clutch occurs, the adjust mechanism includes a clutch head that comes into contact with a clutch surface formed on the opposing portion, and a A bolt portion is fitted onto the extending shaft portion so as to be able to slide in the axial direction and rotate integrally with the piston, and is screwed into a female screw portion formed in the axial direction of the piston, and the bolt portion and the clutch head are connected to each other. Since it is composed of a firing means that brings it into contact,
Residual air in the threaded portion between the piston and adjustment bolt can be quickly discharged to the outside.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional front view showing one embodiment of the present invention;
FIG. 2 is a sectional front view showing another embodiment, and FIG. 3 is a sectional front view showing an example of a conventional braking gap automatic adjustment device. 10... Wheel cylinder, 13, 14... Piston, 15... Hydraulic pressure chamber, 21... Adjustment bolt, 2
9...Clutch surface, 37...Adjustment bolt insertion hole, 38...Multi-thread female thread, 42...Clutch head, 4
3...shaft part, 44...bolt part, 46...spring,
47...Multi-start male thread, 48, 49...Hydraulic fluid flow path.

Claims (1)

[Claims] 1. An adjusting mechanism is disposed in a hydraulic pressure chamber defined by a piston that is fluid-tightly and movably inserted into a wheel cylinder and an opposing portion of the piston, and when a braking gap of a predetermined value or more is generated, the adjusting mechanism is activated. In an automatic braking gap adjustment device for a hydraulically operated brake that advances a piston, the adjusting mechanism includes a clutch head that abuts a clutch surface formed on the opposing portion, and a shaft that extends from the clutch head. a bolt portion which is fitted onto the outside so as to be slidable and integrally rotatable in the direction of the piston and screwed into a female threaded portion formed in the axial direction of the piston; and an elastic means for bringing the bolt portion and the clutch head into contact with each other. An automatic braking gap adjustment device for a hydraulically operated brake, characterized by comprising: