JPS633475Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a wheel cylinder for a vehicle drum brake equipped with an automatic braking gap adjustment device.

[Prior art]

In a drum brake that expands the brake shoe using a foil cylinder equipped with an automatic braking gap adjustment device, the drum is removed from the brake shoe when the brake shoe gets stuck in the shoe groove caused by wear on the drum braking surface. Conventionally, the manual brake cable that passes through the back plate is removed from the cable cap attached to the back plate, the cable is loosened, and the brake shoe is slightly reduced by the biasing force of the return spring. The work involves removing the set-in or, in cases where a retainer is interposed between the shoe web and the piston of the wheel cylinder, removing the retainer using a tool to reduce the gap between the brake shoes and removing the set-in. It was tedious and time consuming.

[Purpose of invention]

The present invention has been made in view of the above points, and it is an object of the present invention to provide a foil cylinder for a drum brake for a vehicle, which allows the brake shoe to be easily removed even if the brake shoe is wedged into the drum braking surface.

[Structure of the idea]

In order to achieve the above object, the present invention includes an adjusting nut and an adjusting bolt screwed together with a multi-thread screw in a hydraulic pressure chamber defined by a piston slidably inserted into a cylinder and its opposing part. , and the clutch surface of the adjusting bolt is brought into contact with the clutch surface of the opposing part, while the adjusting nut is held on the piston, and when a braking gap of more than a predetermined value is generated, the adjusting bolt is screwed. In a wheel cylinder of a drum brake for a vehicle equipped with an automatic braking gap adjustment device in a hydraulically operated brake that advances a piston, a gear portion is provided extending from the rear end of the adjustment bolt, and the gear portion is connected to the opposing portion. It is characterized in that it is disposed in an atmospheric pressure chamber formed at the back of the clutch surface, and that an insertion hole for a tool that engages with the gear portion is bored in the atmospheric pressure chamber.

〔Example〕

An embodiment in which the present invention is applied to a two-leading drum brake will be described in detail with reference to the drawings.

On the inner surface of the back plate 1 fixed to the vehicle body, a pair of upper and lower wheel cylinders 2 (the lower part is not shown) and a pair of left and right brake shoes 3 are arranged symmetrically around the center of the back plate 1. .

The wheel cylinder 2 is composed of a cylinder body 4 having a cylinder hole 4a with only one end open, and a piston 5 that slides into the cylinder hole 4a to define a hydraulic chamber 4b.The cylinder body 4 has a back plate. Fixed to 1. Cylinder body 4
The outer end of the piston 5 is engaged with the brake shoe 3, and relative rotation between the cylinder body 4 and the piston 5 is prevented.

The piston 5 has a collar portion 7 at the tip of the small diameter portion 6, and a cup groove 8 formed in the small diameter portion 6.
A piston cup 9 is fitted into the. Three circular counterbore holes 10 are formed at the tip of the piston 5, and by forming these holes 10, a crescent-shaped communication hole 11 is formed in the collar 7, and the inside of the hydraulic chamber 4b is formed. It is designed to supply pressurized fluid to the The adjustment nut 12 is arranged so as to be in contact with the contact surface 13 of the piston 5 so as to be able to separate from it. ing. The piston 5, adjuster nut 12, spring retainer 14, and spring 15 are assembled as follows. First, the collar 7 of the piston 5
Next, the notch 16 formed in the collar 12a of the adjuster nut 12 is brought into contact with the communication hole 11 so as to align with the same. Next, the spring 15 is interposed between the adjuster nut 12 and the spring retainer 14, and the leg portion 14 of the spring retainer 14 is inserted.
a into the notch 16 of the adjusting nut 12, and the locking pawl 14b is inserted into the communication hole 1 of the piston 5.
Lock at 1. As a result, the spring 15 is compressed between the collar portion 12a of the adjuster nut 12 and the spring seat portion 14c of the spring retainer 14.

An adjustment bolt 17 is screwed into the shaft portion of the adjustment nut 12 via a multi-start thread portion 17a so as to pass through the center thereof. The threaded portion between the adjusting nut 12 and the adjusting bolt 17 has an appropriate braking gap for each brake shoe 3;
That is, an axial backlash is set that corresponds to an appropriate gap between each brake shoe 3 and a brake drum (not shown).

A clutch portion 1 is attached to the end of the adjuster bolt 17.
7b is formed, and this clutch portion 17b
is rotatably fitted into a cylinder small diameter section 18 provided on the inner end wall of the cylinder body 4, and faces a conical clutch surface 19 formed on the back wall of the cylinder small diameter section 18. And adjust bolt 1
A seal member 20 is fitted into the seal groove 17c of No. 7 to prevent the hydraulic pressure in the hydraulic pressure chamber 4b from acting on the clutch surface 19.

Clutch portion 17b of the adjusting bolt 17
A gear portion 21 having a worm wheel or bevel gear is integrally formed at the rear end portion, and this gear portion 21 is connected to the clutch surface 19 of the cylinder small diameter portion 18.
It is placed in an atmospheric pressure chamber 22 formed at the back of the.

In addition, a tool insertion hole 23 that communicates the atmospheric pressure chamber with the outside is bored in the cylinder body 4 from the back plate 1 side, and is usually plugged with a grommet 24. A recess 23a is provided in which a protrusion 25a at the tip of a tool 25, which will be described later, engages to center the tool shaft. The tool 25 has, for example, a protrusion 25a at its tip, a gear 25b such as a worm or bevel gear near the protrusion, and a handle 25c at its rear end.

Next, the operation of this embodiment will be explained. When the shoe lining (not shown) of the brake shoe 3 gets stuck in the groove created by the abrasion of the drum braking surface, the tool 25 is inserted into the tool insertion hole 23. Then, the tip convex portion 25a is engaged with the recess 23a located at the back of the tool insertion hole 23, and the gear portion 21 formed at the tip of the clutch portion 17b of the adjusting bolt 17 is engaged.
The gear 25b of the tool 25 is engaged with the tool 25.
By rotating the adjuster bolt 17, the adjuster bolt 17 is rotated. This rotation causes the adjustment bolt 17 to
The adjuster nut 12 that is screwed into the piston 5 moves back, and the piston 5 also moves back. When the piston 5 retreats, the brake shoe 3 is activated by a return spring (not shown).
The brake drum shrinks due to the restoring force, and the shoe lining comes off from the wear groove on the drum braking surface, allowing the brake drum to be removed.

In addition, the clutch portion 17b of the adjuster bolt 17
If the gear is set in a direction away from the clutch surface 19 of the cylinder small diameter portion 18, the adjustment bolt 17 can be returned smoothly without damaging the clutch surface 19 when rotated in the anti-adjustment direction during this removal work. can.

[Effect of idea]

As mentioned above, in this invention, the gear of the tool is engaged with the gear part formed at the rear end of the clutch part of the adjusting bolt, and the adjusting bolt is reversed. If the brake shoe is wedged in the piston, the adjustment bolt can be reversed to move the piston back and reduce the brake shoe, making it easy to remove the brake drum and replace the brake shoe. Become.

In addition, when assembling the adjusting bolt, the gap between the clutch part of the adjusting bolt and the clutch surface of the cylinder is sealed and airtight, but air can be removed from the insertion hole of the tool, making it easy to insert the adjusting bolt. This makes it possible to improve workability and operability.

[Brief explanation of the drawing]

The drawings show a wheel cylinder for a vehicle drum brake according to the present invention, in which FIG. 1 is a sectional front view of the main part, FIG.
The figure is a - sectional view of FIG. 1 is the back plate, 2 is the foil cylinder, 3
is the brake shoe, 4 is the cylinder body, 4a is the cylinder hole, 4b is the hydraulic chamber, 5 is the piston, 6 is the small diameter part, 7 is the collar part, 8 is the cup groove, 9 is the piston cup, 10 is the counterbore hole part , 11 is a communication hole, 12
13 is an adjustment nut, 13 is a contact surface, 14 is a spring retainer, 15 is a spring, 16 is a notch, 17 is an adjustment bolt, 17a is a multi-thread thread, 17b is a clutch, 18 is a cylinder small diameter portion, 19 is Clutch surface, 20 is a sealing member, 21
22 is a gear portion, 22 is an atmospheric pressure chamber, 23 is a tool insertion hole, 23a is a recess, 24 is a grommet, 25 is a tool, 25a is a protrusion at the tip of the tool, and 25b is a gear.

Claims (1)

[Scope of utility model registration request] An adjustment nut and an adjustment bolt screwed together with a multi-thread screw are arranged in a hydraulic pressure chamber defined by a piston slidably inserted into a cylinder and its opposing part, and the clutch surface of the adjustment bolt is A braking gap in a hydraulically actuated brake that abuts against the clutch surface of the opposing portion, while holding the adjusting nut on the piston, and when a braking gap of more than a predetermined value occurs, the adjusting bolt is screwed to advance the piston. In the wheel cylinder of a vehicle drum brake equipped with an automatic adjustment device,
a gear portion extending from the rear end of the adjustment bolt;
A drum brake for a vehicle, characterized in that the gear part is disposed in an atmospheric pressure chamber formed at the back of the clutch surface of the opposing part, and an insertion hole for a tool that engages with the gear part is bored in the atmospheric pressure chamber. foil cylinder.