JPH0449389Y2 - - Google Patents

Description

[Detailed explanation of the invention] A. Purpose of the invention (1) Industrial application field The present invention is a drum brake for a vehicle, in particular, a return spring is installed between a pair of brake shoes, and the wear of both brake shoes is prevented. A brake shoe diameter reduction position regulating strut whose effective length is accordingly increased and corrected is interposed, one end of the parking lever is rotatably supported on the one brake shoe, and the other end of the parking lever A regulating member is provided between the brake shoe and the one brake shoe, and the regulating member engages the parking lever with the strut when the brake is not activated to regulate the backward position of the parking lever. The present invention relates to an improvement in which a space is provided between the brake shoe and the strut to allow the diameters of both brake shoes to be reduced by the backward movement of the parking lever as the restriction of the restriction member is released.

(2) Conventional technology In internally expanding drum brake devices, the inner peripheral surface of the brake drum that comes into sliding contact with the brake shoe wears out due to long-term use, forming a step. For example, when the brake drum is removed in the axial direction to replace the brake shoe, the stepped portion and the peripheral edge of the friction lining interfere with each other and Therefore, the above-mentioned detachment work is even more difficult, especially in the case of a brake shoe 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. This is accompanied by

Therefore, in order to facilitate the above-mentioned detachment work, the small diameter part of the pin-shaped regulating member is slidably inserted into the through hole of the brake shoe, etc., and the parking lever is moved to the retracted position of the regulating member. It is known that the parking lever is regulated by coming into contact with the large diameter part, and the backward movement of the parking lever is allowed by making the parking lever come into contact with the small diameter part (Utility Model Application No. 56-60830). (see official bulletin).

(3) Problems to be solved by the invention However, if the regulating member is configured to slide within the through hole, parking will occur due to the tensile force of the strong return spring that biases both brake shoes in the radial direction. Since the lever is pressed against the large diameter part of the regulation member, the regulation member will tilt due to the clearance between the small diameter part of the regulation member and the through hole, and as a result, when the regulation member is slid, the small diameter part and There is a problem that galling occurs between the regulating member and the through hole, and the movement of the regulating member is not smooth.

An object of the present invention is to provide the drum brake that can solve the above problems.

B. Structure of the invention (1) Means for solving the problem The present invention provides a method for attaching the regulating member to the parking lever via a support shaft so that it can reciprocate in a direction perpendicular to the parking lever rotation plane. The regulating member has a contact portion that contacts the one brake shoe, and the regulating member is configured to engage and disengage from the parking lever in order to engage with the parking lever and regulate the backward position of the parking lever. The regulating member includes a freely movable engaging portion and an elongated hole through which the support shaft is inserted to allow the backward movement of the parking lever when the engaging portion is disengaged from the parking lever. The parking lever is characterized by being connected to a spring that urges the parking lever toward the parking lever.

(2) Effect With the above configuration, even if a pressure contact force due to the tensile force of the return spring acts between the engaging parts,
If the engaging part is pushed against the biasing force of the spring, the engaging part is simply engaged with the parking lever, so there is no galling between the engaging part and the parking lever, and the engaging part is moved away from the parking lever. Leave easily. Therefore, the movement of the regulating member is smooth.

(3) Example In Fig. 1, 1 is a brake panel fixed to a stationary part of a vehicle body, and a pair of left and right bow-shaped brake shoes ₂₁ , ₂₂ are arranged inside the brake panel. Each brake shoe ₂₁ , ₂₂ is made up of webs ₃₁ , ₃₂ that exist on a plane parallel to the brake panel ₁ , and
A back plate 4 _{1 , 4 2} is fixed to the outer peripheral surface of the back plate 4 ₁ , 4 ₂ , and a friction lining 5 is joined to the outer peripheral surface of the back plate 4 ₁ , 4 ₂ .
The friction linings 5 _{1 and 5 2 are}
The brake pads are adapted to slide against the inner peripheral surface of a brake drum (not shown) which surrounds them and rotates together with the wheel.

In the right brake shoe 2 ₁ , a flat 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 rotated via a spindle 7 near the upper end of the web 3 ₁ . Supported for free movement.

A well-known wheel cylinder 8 for expanding the diameter of both brake shoes 2 ₁ and 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 and 9 ₂ that slide inside the 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 brake shoe diameter reduction position regulating strut 13 is interposed between the brake shoes 2 ₁ and 2 ₂ . The strut 13 is screwed into a first cylindrical body 14 ₁ having a left-handed thread on its inner circumferential surface, a second cylindrical body 14 ₂ having a right-handed thread on its inner circumferential surface, and both cylindrical bodies 14 ₁ and 14 ₂ . Screw shaft 16 with ratchet 15 in the middle
It becomes more.

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 portion 18 connected to one opening edge of the U-shaped notch 17 and the inner circumferential surface of the right side web ₃₁ facing the stepped portion 18.

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 stepped 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
is a short cylindrical engaging body 28 that is loosely inserted into the coiled spring 26 and the U-shaped bent portion 6a at the lower end of the parking lever 6, and is fixed to one end of the operating wire 27.
engages with the outer peripheral surface of the bent portion 6a.

As clearly shown in FIGS. 4 to 6, a protruding part 29 is provided on the outer surface of the tip of the bent part 6a, and a part of the outer peripheral surface of the engaging body 28 is always located below the protruding part 29. The movement of the engaging body 28 toward the opening side of the bent portion 6a is restricted, so that the bent portion 6a
The operating wire 27 is prevented from being removed from the opening.

A regulating member 30 is provided near the bent portion 6a of the parking lever 6 to regulate the backward position of the parking lever 6 when the brake is not activated. Regulation member 3
0 has an elongated main plate 31, and a long hole 32 is formed in the main plate 31 along its longitudinal direction. Main plate 31
The flat surface of faces the back of the parking lever 6,
The proximal male threaded portion 3 of the support shaft 33 inserted into the elongated hole 32
3a is screwed into the female screw hole 34 of the parking lever 6. Enlarged head 33 at the tip of the main plate 31 and support shaft 33
A coiled spring 35 is compressed between the coil spring 35 and the spring 35, and the regulating member 30 is always urged toward the parking lever 6 side by the elastic force of the spring 35. can be moved to the brake panel 1 side. Therefore, the regulating member 30
can reciprocate in a direction perpendicular to the rotation plane of the parking lever 6.

The regulating member 30 has a rotation stopper plate 36 connected to one end of the main plate 31 and an engaging part 37 protruding from the middle part of the main plate 31. When engaged, the tip of the engaging portion 37 engages with the outer surface of the parking lever 6, and this engaged state is maintained by the elastic force of the spring 35. At this time, the regulating member 30 is in a regulating position that regulates the backward position of the parking lever 6, and therefore, when the brake is not activated, the abutment portion 31a having an arcuate end surface on the other end of the main plate 31 is connected to the right brake shaft. The back plate 4 of 2 ₁ comes into contact with the inner peripheral surface of ₁ , and the parking lever 6 engages with the strut 13,
The backward movement of the parking lever 6 is restricted.

When the parking lever 6 is in the retracted position, the support shaft 33 is located at the inner end of the elongated hole 32, and the tool is inserted into the web ₃₁ of the right brake shoe 21 so as to face the engaging portion 37 of the regulating member ₃₀ . A window 38 is formed. Although not shown in the diagram, there is a window 3 on the brake drum.
8 is formed. Thereby, by pressing the engaging portion 37 toward the brake panel 1 through the opening and the window 38, the regulating member 30 can be disengaged from the parking lever 6.

A U-shaped groove 39 that opens toward the brake panel 1 is formed at the tip of the anti-rotation plate 36, and by inserting and holding the operating wire 27 into the groove 39, the operating wire 27 can be inserted from the bent portion 6a of the parking lever 6. is prevented from coming off. Also, one end of the spring 26 into which the operating wire 27 is loosely inserted is connected to a rotation prevention plate 36.
abuts against the inner surface of the body with a predetermined elastic force.

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
The detent arms 23 are connected to the struts 13.
It is pushed back, rotates counterclockwise in Figure 1, and returns to its original position.

When the brake is not activated, the regulating member 30 is in the regulating position, and the contact portion 31a of the regulating member 30 is moved to the right brake shoe 2 ₁ by the strong tensile force of the return spring 11 via the parking lever 6.
The parking lever 6 is in the retreat position and comes into contact with the inner circumferential surface of the back plate ₄₁ .

In this state, the rotation of the regulating member 30 is prevented by the engaging portion 37 and the rotation stopper plate 36 engaging with the parking lever 6, so that the parking lever 6 is reliably held in the retreated 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 regulating member 30 rotates together with the parking lever 6 and moves away from the back plate 4 ₁ , but rotation of the regulating member 30 itself is prevented by the engaging portion 37 and the rotation stopper plate 36 . Therefore, the position of the restriction member 30 with respect to the parking lever 6 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 , use a tool such as a screwdriver to remove the engaging portion 37 of the regulating member 30 from the window 38 of the right brake shoe 2 ₁ . When pressed, the regulating member 30 moves toward the brake panel 1 against the biasing force of the spring 35, thereby causing the engaging portion 37 to disengage from the outer surface of the parking lever 6. In this case, even if a pressure contact force due to the tensile force of the return spring 11 is applied to the engaging portion 37, the engaging portion 37 is simply engaged with the parking lever 6, so it is not engaged with the parking lever 6. There is no occurrence of galling between the regulating member 30 and the joint portion 37, and therefore the movement of the regulating member 30 is smooth.

When the engaging portion 37 is disengaged from the outer surface of the parking lever 6, the parking lever 6 moves further backward than the retracted position as shown in FIGS. 7 and 8 due to the tensile force of the return spring 11. Accordingly, both brake shoes 2 _{1 and 2 2} are reduced in diameter due to the distance d between the web 3 ₁ and _the strut 13 in the right brake shoe 2 ₁ . At this time, the engaging portion 37 of the regulating member 30 comes into contact with the back surface of the parking lever 6,
Further, the support shaft 33 is located at the outer end of the elongated hole 32.

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.

When both brake shoes 2 ₁ and 2 ₂ are reduced in diameter,
The restriction member 30 is prevented from rotating by holding the operating wire 27 in the U-shaped groove 39 and by inserting the support shaft 33 into the elongated hole 32 .

After replacing the brake shoes 2 ₁ and 2 ₂ , if the parking brake is activated by pulling the operating wire 27 , the regulating member 30 is prevented from moving by the elastic force of the spring 26 , so the parking lever 6
By rotating clockwise in FIG. 1, the engaging portion 37 and the rotation stopper plate 36 engage with the outer and inner surfaces of the parking lever 6, respectively, and the regulating member 30 is automatically moved to the regulating position. Return.

C. Effects of the invention According to the invention, the engaging part of the regulating member that regulates the backward position of the parking lever is configured to simply engage the parking lever, so that the regulating member can move when replacing the brake shoe, etc. This makes it possible to easily remove the brake drum.

[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, 4, and 5 are enlarged cross-sectional views taken along the lines of FIG. , FIG. 6 is an exploded perspective view of a portion where the regulating member is attached, FIG. 7 is a side view of the main part for explaining the operation, and FIG. 8 is a sectional view taken along the line of FIG. 7. d... Distance, 2 ₁ , 2 ₂ ... Brake shoe, 6
... Parking lever, 11 ... Return spring, 13
...Strut, 30...Regulation member, 31a...
Contact portion, 32... Long hole, 33... Support shaft, 35...
Spring.

Claims (1)

[Scope of utility model registration request] A return spring is tensioned between the pair of brake shoes, and a brake shoe diameter reduction position regulating strut is interposed to increase the effective length as both brake shoes wear out. One end of the parking lever is rotatably supported on the lever, and the parking lever is engaged with the strut between the other end of the parking lever and the one brake shoe when the brake is not activated. A regulating member for regulating the backward position of the parking lever is provided between the one brake shoe and the strut, and the rearward movement of the parking lever as the regulating member releases the regulation causes the movement of both brake shoes. In a vehicle drum brake having an interval that allows diameter reduction, the regulating member is attached to the parking lever via a support shaft so as to be able to reciprocate in a direction perpendicular to the parking lever rotation plane, and The regulating member includes an abutting portion that abuts the one brake shoe, and a removably engaged member that engages with the parking lever to regulate the backward position of the parking lever. and an elongated hole through which the support shaft is inserted to allow the backward movement of the parking lever when the engaging portion is disengaged from the parking lever, and the regulating member is provided with an elongated hole through which the support shaft is inserted. A vehicle drum brake characterized by connecting a spring that biases the vehicle side.