JPH0515624Y2 - - Google Patents

Description

[Detailed explanation of the invention] A. Purpose of the invention (1) Industrial application field The present invention moves the vehicle brake, especially the parking lever, further backward than the backward position when the brake is not activated. This relates to an improvement in which the diameter of the brake shoe is reduced.

(2) Conventional technology In internally expanding drum brake systems, the inner circumferential surface of the brake drum that rubs against the brake shoe wears out due to long-term use, forming a step. The diameter is constantly adjusted to increase in order to compensate for wear, so when the brake drum is removed in the axial direction to replace the brake shoe, for example, the stepped portion and the peripheral edge of the friction lining interfere with each other, causing the brake drum's axis to Therefore, especially in brake shoes equipped with an automatic brake gap adjustment device, which makes it difficult to reduce the diameter of the brake shoe to its original state once the diameter has been expanded, it is even more difficult to perform the above-mentioned detachment work. This is a difficult situation.

Therefore, in order to facilitate the above-mentioned detachment work, the small diameter part of the stop pin is slidably inserted into the through hole of the brake shoe etc. It is known that the parking lever is regulated by contacting the small diameter portion, and the backward movement of the parking lever is allowed by the parking lever being brought into contact with the small diameter portion (see Japanese Utility Model Publication No. 56-60830).

(3) Problems to be solved by the invention However, when the stop pin is constructed as a sliding type, the parking lever is moved from the large diameter part of the stop pin due to the tensile force of the strong return spring that urges both brake shoes in the direction of diameter reduction. Since it is pressed against
The stop pin tilts due to the clearance between the small diameter part of the stop pin and the through hole, and as a result, when the stop pin is slid, galling occurs between the small diameter part and the through hole, making the stop pin not move smoothly. There is a problem.

An object of the present invention is to provide a drum brake that can solve the above problems, is low cost, and has good assembly workability.

B. Structure of the invention (1) Means for solving the problem In order to achieve the above object, the present invention moves the parking lever further backward than the backward position when the brake is not activated, thereby reversing the pair of brake levers. In the vehicle drum brake in which the diameter of the brake shoe is reduced, the parking lever has a base portion of the stop lever that has an engaging portion at the tip that can come into contact with the back surface of one of the brake shoes. The engaging part is rotated between a restriction position in which the engaging part is brought into contact with the back surface to restrict the backward movement of the parking lever, and a restriction release position in which the engaging part is separated from the back surface and the backward movement of the parking lever is permitted. A spring is provided between the stop lever and the parking lever to bias the stop lever in a direction from the restriction release position toward the restriction position. The parking lever is characterized in that the parking lever is provided with a stopper that comes into contact with the stop lever so that the stop lever is held at the restriction position.

(2) Effect With the structure described above, even if pressure force due to the tensile force of the return spring acts between the stop lever and the support shaft, since the stop lever is rotatable, the contact between it and the support shaft will be reduced. There is no galling in between, and as a result, the movement of the stop lever becomes smooth.

In particular, the above-mentioned stop lever is pivotally supported by the parking lever, and can be assembled to the parking lever side independently from the brake shoe, together with a spring for biasing the stop lever to the regulation position. Not only does it not require any special modifications to the brake shoe side, but even if the brake shoe is replaced due to wear, the existing stop lever and spring can continue to be used effectively without the need for special position adjustments. .

(3) Embodiment In FIG. 1, reference numeral 1 denotes a brake panel fixed to a stationary portion of a vehicle body, and a pair of left and right arcuate brake shoes 2 ₁ and 2 ₂ are disposed inside the brake panel. Each brake shoe 2 ₁ , 2 ₂ has a web 3 1 , 3 ₂ existing in a plane parallel to the brake panel ₁ and a web 3 ₁ , 3 _{2 .}
Back plates 4 ₁ , 4 ₂ fixed to the outer peripheral surfaces of , and back plates 4 1 , 4 ₂ ,
Friction lining 5 ₁ , 5 joined to the outer peripheral surface of 4 _2
2 and more. Both friction linings 5 ₁ and 5 ₂ are adapted to rub against the inner peripheral surface of a brake drum (not shown) surrounding them and rotating together with the wheel.

In the right brake shoe 2 ₁ , a parking lever 6 is disposed close to the back surface of the web 3 ₁ , and the upper end of the parking lever 6 is rotatable via a spindle 7 near the upper end of the web 3 ₁ . Supported by

A known wheel cylinder 8 for expanding the diameter of both brake shoes 2 ₁ , 2 ₂ is provided at the inner upper part of the brake panel 1, and a pair of left and right operating pistons 9 ₁ , 9 ₂ sliding inside the wheel cylinder 8 are installed on both webs. Opposed to the upper ends of the brake shoes 3 ₁ and 3 ₂ , and at the inner lower part of the brake panel 1, supports the lower ends of the webs 3 ₁ and 3 ₂ , and serves as a fulcrum when expanding and contracting the diameter of both brake shoes 2 ₁ and 2 ₂ . An anchor block 10 is fixedly installed. A strong coiled return spring 11 is stretched between the upper portions of both brake shoes 2 ₁ and 2 ₂ to constantly bias them in the direction of diameter reduction. Further, a contact spring 12 is provided between the lower ends of both brake shoes 2 ₁ and 2 ₂ to bring them into contact with the anchor block 10 . The wheel cylinders 8 are actuated, as is conventional, by the output hydraulic pressure of a master cylinder operated by a brake pedal.

Adjacent to the wheel cylinder 8, a turnbuckle type diameter reduction position regulating strut 13 is interposed between the brake shoes 2 ₁ and 2 ₂ . The strut 13 has a first cylindrical body 14 having a left-handed thread on its inner peripheral surface.
₁ , a second cylindrical body 14 ₂ having a right-handed thread on its inner peripheral surface,
It consists of a threaded shaft 16 which is screwed onto both cylindrical bodies 14 ₁ and 14 ₂ and has a ratchet 15 in the middle.

As shown in FIG. 2, a U-shaped notch 17 at the right end engages with the inner edge of the parking lever 6 to make the first cylinder 14 ₁ non-rotatable. Further, a predetermined distance d is formed between the stepped surface 18 connected to one opening edge of the U-shaped notch 17 and the inner circumferential surface of the right web ₃₁ facing thereto.

As shown in FIG. 3, the U-shaped notch 19 at the left end of the second cylinder 14 ₂ is engaged with the inner edge of the left web 3 ₂ so that the second cylinder 14 2 is also non-rotatable.

An adjustment lever 20 for interlocking the left web ₃₂ with the ratchet 15 is rotatably supported via a support shaft 21. In the adjustment lever 20, a feed pawl 22a formed at the tip of the operating arm 22 engages with the ratchet 15, and a side edge of the tip of the detent arm 23 engages with the second cylindrical body 14 as clearly shown in FIG. ₂ Engage with the step surface 24 on the left end.
A coiled spring 25 is stretched between the base end of the actuation arm 22 and the lower part of the left web ₃₂ , and the tensile force of the spring 25 causes the adjustment lever 20 to strut and extend the ratchet 15 using the feed pawl 22a. A rotational moment about the support shaft 21 is applied to rotate in the direction.

Operation wire 27 for operating the parking lever 6
inside the coiled spring 26 and the parking lever 6
An engaging body 28 loosely inserted into the U-shaped bent portion 6a at the lower end and fixed to one end of the operating wire 27 engages with the outer surface of the bent portion 6a.

As clearly shown in FIGS. 4 and 5, a support shaft 29 is installed near the bent portion 6a of the parking lever 6.
The base 30a of the stop lever 30 is rotatably supported, and the engaging portion 30b formed at the tip of the stop lever 30 engages the right brake shoe 2 ₁
The back plate 4 ₁ faces the inner circumferential surface of the back plate 4 so as to be able to come into contact with and separate from it. Support shaft 2
9, the coil portion 3 of the torsion spring 31 as a spring.
1a is loosely fitted, and one end 31 of the torsion spring 31
b is attached to the inner edge of the parking lever 6, and the other end 3
1c are respectively engaged with the upper edges of the engaging portions 30b of the stop lever 30.

The stop lever 30 is biased clockwise in FIGS. 1 and 5 by the elastic force of the torsion spring 31 (that is, in the direction from the release position to the restriction position, which will be described later), and the rotation limit of the stop lever 30 is determined by the The engaged piece 32 is moved to a protrusion 33 as a stopper formed on the outer edge of the parking lever 6.
It is regulated by engaging with. Under this condition, the stop lever 30 is
The vehicle is in a regulating position that regulates the backward position of the vehicle.

In the regulating position of the stop lever 30, the bulging portion 30c of the stop lever 30 is located within the bent portion 6a of the parking lever 6, and the bulging portion 30c is located within the bent portion 6a of the parking lever 6.
c prevents the operating wire 27 from coming out from the bent portion 6a when the parking brake is not activated, and therefore when the operating wire is not being pulled.

When the brake is not activated, the parking lever 6 is rotated counterclockwise in FIG.
b engages with the inner circumferential surface of the back plate 4 ₁ of the right brake shoe 2 ₁ , but the engagement point a between the engaging portion 30 b and the back plate 4 ₁ is at the center O ₁ of the brake panel 1 and the support shaft. 2
The parking lever 6 is located closer to the bent portion 6a of the parking lever ₆ than the straight line XX passing through the axis O2 of the parking lever 9.

As a result, the engaging portion 30b of the stop lever 30 is pressed against the inner circumferential surface of the back plate ₄₁ by the tensile force of the return spring 1, and no force is applied to the stop lever 30 to rotate it counterclockwise in FIG. 1. The torsion force of the torsion spring 31 may be small, so that an inexpensive torsion spring 31 can be used.

As described above, the engaging portion 30 of the stop lever 30
b is engaged with the inner peripheral surface of the back plate ₄₁ , the parking lever 6 is in the retracted position when the brake is not activated, and in this state, the engaging portion 3 of the parking lever 6
A window 34 is formed in the web ₃₁ so as to face the lower edge near 0b, and a tool insertion opening 3 for a screwdriver etc. is formed between the lower edge of the window 34 and the lower edge of the stop lever 30.
5 is defined. Although not shown in the figure, an opening that can fit into the window 34 is formed in the brake drum.

Therefore, if the tool T is inserted into the tool insertion port 35 through the opening of the brake drum as shown in FIG. The stop lever 30 rotates clockwise to reach the restriction release position where the engaging portion 30b is disengaged from the engaging point a on the inner peripheral surface of the back plate ₄₁ , and the stop lever 30 prevents the parking lever 6 from moving further backward than the backward position. Allow.

Next, the operation of this embodiment will be explained.

When pressure oil is supplied to the wheel cylinder 8 by operating a brake pedal (not shown), the left and right actuating pistons 9 ₁ and 9 ₂ are actuated outward by the oil pressure to return both brake shoes 2 ₁ and 2 ₂ . Each of the friction linings 5 ₁ and 5 2 expands in diameter against the tensile force of the spring 11, and the friction linings 5 1 and 5 ₂ are brought into pressure contact with the brake drum, thereby applying a brake to the wheel.

In the above brake operation process, both brake shoes 2 ₁ , 5 ₂ are worn due to friction linings 5 1 , 5 ₂
When the diameter of the left brake shoe 2 ₂ increases due to relative movement beyond a certain value, the adjustment lever 20 follows the diameter expansion of the left brake shoe 2 ₂ and its detent arm 23 separates from the strut 13. The tension force of the spring 25 causes the adjustment lever 20 to rotate clockwise in FIG. Ru.

Next, the wheel cylinder 8 is deenergized and returned to both brake shoes 2 ₁ , 2 ₂ by the tensile force of the spring 11.
When the diameters of the struts 13 are reduced, their diameter reduction positions are regulated by the struts 13 whose effective lengths have been corrected as described above, and each friction lining 5 ₁ , 5 ₂ has an extension amount of the struts 13 that is greater than before the brake is applied. one half of
This displacement becomes a compensation amount for the wear of both friction linings 5 ₁ and 5 ₂ due to brake operation.

When the brake is released, the adjustment lever 20
connects the detent arm 23 of it to the strut 13.
It is pushed back, rotates counterclockwise in Figure 1, and returns to its original position.

When the brake is not activated, the engaging portion 30b of the stop lever 30 engages with the inner peripheral surface of the back plate ₄₁ of the right brake shoe ₂₁ via the parking lever 6 due to the strong tensile force of the return spring 11. , the parking lever 6 is in the reverse position.

In this state, the engagement point a between the stop lever 30 and the back plate ₄₁ is located closer to the rear end of the parking lever 6 than the straight line 30b is pressed against the back plate ₄₁ , and the stop lever 3
0, no force acts on it to rotate it counterclockwise in Figure 1. Therefore, the parking lever 6 is reliably held in the backward position.

Next, when parking the vehicle, the operating wire 27
1, the parking lever 6 rotates clockwise about the support shaft 7, moves the strut 13 to the left, expands the diameter of the left brake shoe ₂₂ , and Press the friction lining 5 ₂ against the brake drum. As the operating wire 27 is subsequently pulled, the parking lever 6 rotates about the engagement portion with the strut 13 as a _fulcrum.
expands in diameter and presses its friction lining ₅₁ against the inner surface of the brake drum to apply brakes to the wheel.

When the parking brake is activated, the stop lever 30 rotates together with the parking lever 6 and moves away from the back plate ₄₁ , but the rotation of the stop lever 30 itself is prevented by the engagement between the engagement piece 32 and the protrusion 33. Parking lever 6
The position of the stop lever 30 relative to the brake is the same as when the brake is not activated, and therefore the stop lever 30 is held at the restriction position.

For example, when removing the brake drum in the axial direction to replace the brake shoes 2 ₁ and 2 ₂ , insert a tool T such as a screwdriver into the tool insertion port 35 of the right brake shoe 2 ₁ . When the stop lever 30 is twisted counterclockwise in FIGS. 1 and 5 against the biasing force of the torsion spring 31, the engaging portion 30b is disengaged from the engaging point a with the inner peripheral surface of the back plate ₄₁ .
In this case, even if a pressure contact force due to the tensile force of the return spring 11 acts between the stop lever 30 and the support shaft 29, the stop lever 30 is rotatable, so the stop lever 30 and the support shaft 29, and the urging force of the torsion spring 31 is weak, so the movement of the stop lever 30 is smooth.

The engagement portion 30b of the stop lever 30 is at the engagement point a.
When the parking lever 6 is released from the rearward position, the tensile force of the return spring 11 causes the parking lever ₆ to move further backward than the backward position as shown by the chain line in _FIG . Due to the distance d between the struts 13, both brake shoes 2 ₁ , 2 ₂ are reduced in diameter.

As a result, a larger gap is formed between the inner circumferential surface of the brake drum and the friction linings 5 ₁ , 5 ₂ than when the brake is not activated, and even if a step is formed on the inner circumferential surface of the brake drum due to wear. Since there is no interference between the stepped portion and the friction linings 5 ₁ and 5 ₂ , the brake drum can be easily removed.

After replacing the brake shoes 2 ₁ and 2 ₂ , if the parking brake is activated by pulling the operation wire 27 , the stop lever 30 will release the torsion spring 31 .
It automatically returns to the regulation position by the urging force of.

C. Effects of the invention According to the invention, the stop lever that regulates the backward position of the parking lever is configured to be rotatable, so that the movement of the stop lever is smooth when replacing the brake shoe, and the work of detaching the brake drum is facilitated. It can be done easily.

In particular, the above-mentioned stop lever is pivotally supported by the parking lever, and can be assembled to the parking lever side independently from the brake shoe, together with a spring for biasing the stop lever to the regulation position. Not only does it not require any special modifications to the brake shoe side, but even if the brake shoe is replaced due to wear, the existing stop lever and spring can continue to be used effectively without the need for special position adjustments. This can contribute to cost savings and improved assembly workability.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention, and FIG. 1 is an overall side view, and FIGS. 2, 3, and 4 are views of FIGS.
FIG. 5 is an enlarged cross-sectional view taken along the line, - line, - line, and FIG. 5 is a cross-sectional view taken along the line - FIG. 2 ₁ , 2 ₂ ... Brake shoe, 6 ... Parking lever, 29 ... Support shaft, 30 ... Stop lever, 30b ... Engagement part, 33 ... Projection as stopper, 31 ... Spring Torsion spring.

Claims (1)

[Scope of utility model registration request] In the drum brake for a vehicle, the diameter of the pair of brake shoes 2 ₁ and 2 ₂ is reduced by moving the parking lever 6 further backward than the backward position when the brake is not activated. , the base of the stop lever 30, which has an engaging portion 30b at the tip that can come into contact with the back surface of one brake shoe ₂₁ , is attached to the stop lever 30.
0 is a regulating position in which the engaging portion 30b is brought into contact with the back surface to restrict the backward position of the parking lever 6, and a regulating position in which the engaging portion 30b is separated from the back surface to allow the backward movement of the parking lever 6. A spring is provided between the stop lever 30 and the parking lever 6 to bias the stop lever 30 in a direction from the restriction release position toward the restriction position. 31, and the parking lever 6 is provided with a stopper 33 that abuts the stop lever 30 so that the stop lever 30 is held at the restriction position under the biasing force of the spring 31.