JPH03239827A - Drum brake - Google Patents

Abstract

PURPOSE:To securely accomplish a returning and rotating operation by performing an engagement releasing operation of a wheel of an adjustment lever and reverse rotation of an adjustment wheel at the same time by means of a pushing-in operation adjustment returning member. CONSTITUTION:In case of returning and rotating an automatic adjustment mechanism, a cam 20b formed integrally with an adjustment returning rotor 20 as an operating member performs an engagement releasing operation. Since this is an operation with respect to an exclusive tool pressing portion 20a formed in the adjustment returning rotor 20, the operation can be performed without visual observation through an operating hole 1a having a size only enough to pass one driver, and further, ratchet teeth of rotor teeth 12b cannot be damaged. Therefore, the returning and rotating operation can be securely accomplished.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a drum brake having an auto-adjust mechanism.

(Prior Art) Conventionally, when the lining has reached its wear limit or when repairing a drum brake, the auto-adjust mechanism is rotated back.
1. This is done by pushing up the adjustment lever with a screwdriver to release the adjustment wheel, and using another screwdriver to reverse the adjustment wheel.

That is, the work requires inserting two screwdrivers through a small window provided in the back plate, which is extremely difficult.

Therefore, in order to solve the above problem, Japanese Utility Model Application Publication No. 60-24951 proposes an auto-adjust mechanism equipped with an adjustment lever that allows the adjustment wheel to be easily reversed using only one tool such as a screwdriver. .

(Problem to be Solved by the Invention) However, in such a conventional auto-adjust mechanism, a straight portion is formed in the return spring, and a riding guide portion is formed at a position opposite to the feed pawl portion of the adjustment lever. .

When performing the unrotating operation, the adjustment wheel is rotated in the opposite direction using a single tool.By reversing the adjustment wheel, the adjustment lever is pushed and moved, and the guide part of the lever is moved against the return spring. It rides on the straight section, and this ride causes the feed pawl to rise, allowing it to ride over the tip of the teeth of the adjustment wheel and turn the adjustment wheel one tooth at a time without requiring the adjustment lever to be pushed up and released. Since it is possible to restore the data, there are problems listed below.

■ Due to variations in product and installation of return springs, the straight part tends to be misaligned with respect to the riding guide part, and the return spring is also prone to bending and deforming due to the contact force of the riding guide part.In such cases, the feed claw part It is not possible to achieve the lifting effect, and two tools are required to unscrew it as in the past.

■ Reverse rotation of the adjustment wheel is performed by pressing a tool against the teeth of the adjustment wheel, so the work must be done while visually checking the teeth of the adjustment wheel.
Additionally, the teeth of the adjustment wheel may be damaged by the tool.

On the other hand, an increasing number of vehicles are currently adopting multi-link suspensions, making it difficult to visually restore the auto-adjust mechanism due to interference with the axle.

The present invention has been made in view of the above-mentioned problem, and when performing a return operation on a drum brake having an auto-adjust mechanism, only a single tool is used to repeatedly press and release, and visual inspection is required. To provide an auto-adjust mechanism that can reliably carry out return work without damaging teeth.

(Means for Solving the Problems) In order to solve the above problems, the drum brake of the present invention simultaneously releases the wheel engagement of the adjustment lever and reversely rotates the adjustment wheel by pushing the tool with a single tool. The means includes an adjusting return member that automatically returns to its original position upon release.

That is, a pair of brake shoes, one end of which is in contact with an anchor provided on the back plate and an expanding means is provided at the other end, and the pair of brake shoes are rotated in the forward direction by the operation of an adjustment lever accompanying braking. A drum brake having an auto-adjust mechanism that automatically adjusts the gap between the brake shoes and the brake drum by extending a first adjustment socket and a second adjustment socket provided between the brake shoes of the drum brake, wherein the adjustment wheel and the adjustment socket are extended. Interposed between the lever and the
An adjuster that includes a tool pushing part that receives an external pressing force and a cam part that rotates the wheel in the opposite direction and releases the engagement between the adjustment lever and the wheel when a predetermined operating force is applied to the tool pushing part. a return member; a one-way clutch that is provided on a rotating support portion that supports the adjustment return member on the adjustment wheel and transmits a force applied to the adjustment return member to the adjustment wheel only in a reverse rotational direction; and a one-way clutch connected to the adjustment return member; The present invention is characterized in that it includes a return spring that applies a return biasing force in the forward rotation direction to the adjustment return member and also determines the return position of the adjustment return member.

(Function) When the lining has reached its wear limit or when a drum brake is being repaired, the auto-adjust mechanism must be returned to its original position using one tool as described below.

First, the adjusting return member is pressed against the tool pushing portion and is rotated backward by a predetermined amount from the outside.

By this reverse rotation operation, the cam part of the adjustment return member pushes up the adjustment lever, and the wheel engagement of the adjustment lever is released.At the same time, the force applied to the adjustment return member by the one-way clutch is transmitted to the adjustment wheel, and the adjustment wheel is moved to the desired position. Only the fixed amount is rotated in the opposite direction.

Next, the tool pressed against the tool pushing portion is released from the adjustment return member.

By this release operation, the urging force of the return spring acts on the adjustment return member, returning the adjustment return member in the forward rotation direction, causing the adjustment lever to engage with the adjustment wheel again, and automatically returning the tool pushing part of the adjustment return member. Return to position. At this time, only the adjustment return member is returned to the forward rotation direction by the one-way clutch, and the adjustment wheel remains rotated in the reverse direction by one tooth or several teeth.

As described above, by repeating the pushing and releasing operations with one tool, the amount of reverse rotation of the adjustment wheel increases, the length of the first adjustment socket and the second adjustment socket is shortened, and the distance between the brake shoe and the brake drum increases. The gap is enlarged and the return operation of the auto-adjust mechanism is completed.

(Example) Embodiments of the present invention will be described below based on the drawings.

First, the configuration will be explained.

Fig. 1 shows a drum brake according to an embodiment having an auto-adjust mechanism. 1 is a back plate fixed to the vehicle body, an anchor 2 is fixed at the lower position in the figure, and a wheel cylinder 3 (expanded) is at the upper position. means) are fixed.

A pair of brake shoes 4, 4 are disposed within the back plate 1, one end of which is in contact with the anchor 2, and the other end of which is in contact with the wheel cylinder 3. It is provided.

The brake shoe 4 is composed of a shoe web 4a, a shoe rim 4b, and a lining 4c, and is operated by hydraulic pressure of the wheel cylinder 3 or parking lever 5.
When the brake shoes 4.4 are operated, the brake shoes 4.4 are expanded and come into sliding contact with the inner surface 6 of the brake drum provided on the wheel side, and are separated from the inner surface 6 of the brake drum by the hydraulic drain of the wheel cylinder 3 or the return operation of the parking lever 5. That's what I do.

Incidentally, when the brake is released, a return force by the shoe return spring 7 acts on both brake shoes 4, 4. Further, the contact of both brake shoes 4° 4 with the anchor 2 is maintained by a spring 8.

The auto-adjust mechanism that automatically adjusts the gap t between the brake shoes 4 and the brake drum 6 during braking includes a first adjustment socket 10, a second adjustment socket 11, an adjuster wheel 12, and an adjuster lever, as shown in FIG. 13.

The first adjustment socket 10 and the second adjustment socket 11 are engaged with upper portions of the pair of brake shoes 4° 4 in parallel to the wheel cylinder 3.

The adjuster toy wheel 12 should be able to expand and contract its entire length using both adjustment sockets 10.11, that is,
A wheel threaded portion 12a which is a member provided to make the shoe interval variable and is screwed into the first adjustment socket 10.
The wheel tooth section 12b has a ratchet tooth formed on the outer periphery and has a contact surface that meshes in the forward rotation direction, and a wheel insertion section 12c that is inserted into the second adjustment socket 11.

The adjustment lever 13 is connected to the wheel tooth portion 12b.
A tooth contact pawl 13a is formed at a position opposite to the ratchet teeth of the lever, and rotates about the lever support pin 14 in the direction of arrow A in FIG. , when the rotation angle is larger than one ratchet tooth, the tooth contact pawl 13a and the ratchet tooth of the wheel tooth portion 12b remain in mesh with each other, and due to the biasing force of the shoe return spring 7 as the brake is released, the rotation angle moves as shown by the arrow in FIG. The adjustment wheel 12 is rotated in the B direction, and the adjustment wheel 12 is rotated in the forward rotation direction C by an angle corresponding to one ratchet tooth of the wheel tooth portion 12b by the engagement of the tooth contact pawl 13a.

As shown in FIGS. 2 and 3, the mechanism for rotating the adjustment wheel 12 of the auto-adjust mechanism in the opposite rotation direction includes an adjustment return rotor 2.
0 (adjustment return member) and one-way ratchet 21
(one-way clutch) and an adjust return spring 22 (return spring).

The adjustment return rotor 20 is interposed between the adjustment wheel 12 and the adjustment lever 13, and includes a tool pusher grS20a that performs a predetermined amount of reverse rotation from the outside;
It has a force ram part 20b that is formed at a position facing the cam contact part 13b formed on the adjustment lever 13 and releases the wheel engagement of the adjustment lever 13 by a predetermined amount of reverse rotation.

The one-way ratchet 21 is provided on a rotation support part that supports the adjustment return rotor 20 on the adjustment wheel 12, and transmits the force applied to the adjustment return rotor 20 to the adjustment wheel 12 only in the reverse rotation direction.

The adjust return spring 22 has one end connected to the adjust return rotor 20 and the other end connected to the brake shoe 4, and applies a return urging force in the forward rotation direction C to the adjust return rotor 20, and also Perform return positioning.

In addition, the back plate 1 corresponding to the tool pushing part 20a
A working hole 1a is formed at the position shown in FIG.

Next, the effect will be explained.

(a) Auto-adjustment function When applying the foot brake by depressing the brake pedal or applying the parking brake by pulling the parking brake lever, both brake shoes 4.4 expand, and the linings 4c, 4c of both brake shoes 4.4 expand. Braking force is applied to the wheels that are in sliding contact with the inner surface 6 of the brake drum and are provided with the brake drum.

During this braking, the adjustment lever 13 rotates in the direction of arrow A in FIG. 1 about the lever support pin 14 as one brake shoe 4 expands. The wider the gap t between the wheel and the brake drum 6, the larger the rotation angle becomes.If the rotation angle becomes larger than one tooth of the ratchet tooth of the wheel tooth portion 12b due to wear of the lining 4c, the adjustment The tooth contact claw 13a of the lever 13 meshes with the ratchet teeth, and as the brake is released while the teeth are still engaged, the biasing force of the shoe return spring 7 acts, and the arrow B in FIG.
Rotate the adjustment wheel 12 in the direction.

In this way, when the adjustment wheel 12 is rotated in the forward rotational direction C by the angle of one ratchet tooth of the wheel tooth portion 12b through engagement with the tooth contact pawl 13a, the first adjustment socket 10 screwed into the wheel threaded portion 12a is rotated. Second
Moving to the left in the figure, the total length of both sockets 10.11 is lengthened, and the space 11it between the lining 4c of both brake shoes 4, 4 and the brake drum 6 is narrowed.

Thereafter, when the rotation angle of the adjustment lever 13 becomes larger than one ratchet tooth again due to wear of the lining 4c, the above operation of narrowing the gap t between the lining 4C and the brake drum 6 is performed.

By repeating the above operations, a pair of brake shoes 4,
The first adjustment socket 10 and the second adjustment socket 11 provided between the brake shoes 4 and the brake drum 6 are expanded according to the wear of the reinige 4c, and the gap t between the brake shoe 4 and the brake drum 6 is automatically adjusted in a direction to keep it constant. An auto-adjustment action is performed.

Incidentally, during auto-adjustment, the adjustment return rotor 20 is fixed at the fixed position shown in FIG. 3 by an adjustment return spring 22, and the adjustment wheel 12
The one-way ratchet 21 is free in the forward rotational direction and does not interfere with the auto-adjustment action.

(b) Returning work When performing the returning work of the auto-adjust mechanism when the lining 4c has reached its wear limit or when repairing a drum brake, etc., use a screwdriver as a tool and perform the following work. It will be done.

First, insert a screwdriver through the working hole 1a, press the tip against the tool pushing part 20a of the adjustment return rotor 20,
As shown in FIG. 4, the push-in operation of the driver causes the wheel tooth portion 12b to be reversely rotated from the outside by a predetermined amount approximately equivalent to one ratchet tooth.

By this reverse rotation operation, the cam portion 20b of the adjustment return rotor 20 pushes up the adjustment lever 13, and the wheel engagement of the adjustment lever 13 is released.At the same time, the force applied to the adjustment return rotor 20 by the one-way ratchet 21 is applied to the adjustment wheel 12. The adjustment wheel 12 is rotated in the opposite direction by the same predetermined amount as the adjustment return rotor 20.

Next, the tool pressed against the tool pushing portion 20a is released from the adjustment return rotor 20.

By this release operation, the biasing force of the adjustment return spring 22 acts on the adjustment return rotor 20, the adjustment return rotor 20 is returned to the forward rotation direction C, the adjustment lever 13 is engaged again with the ratchet teeth of the wheel tooth portion 12b, and the adjustment is performed. The tool pushing portion 20a of the return rotor 20 is automatically returned to the original position shown in FIG.

At this time, only the adjustment return rotor 20 is returned to the forward rotation direction C by the one-way ratchet 21, and the adjustment wheel 12 remains rotated in the reverse direction by an angle equivalent to approximately one ratchet tooth.

By repeating the pushing and releasing operations using one screwdriver as described above, the amount of reverse rotation of the adjustment wheel 12 increases, the first adjustment socket 10 and the second adjustment socket 11 are shortened, and the brake shoe 4 and The gap t between the brake drum and the inner surface 6 is enlarged, and the return operation of the auto-adjust mechanism is completed.

As explained above, in the drum brake of the embodiment, the features listed below are also achieved.

■ When performing the return operation of the auto-adjust mechanism, the cam part 20b integrally formed with the adjustment return rotor 20, which is the operating member, is used to engage and release the mechanism, so that it can be returned reliably by simply repeating pushing and releasing operations with a single screwdriver. Able to perform rotation work. .

■ When performing return work on the auto-adjust mechanism, the operation is performed on a dedicated tool push part 20a formed on the adjust return rotor 20, so visual inspection is required through the work hole 1a, which is large enough for one screwdriver to pass through. The work can be carried out without any problems, and the ratchet teeth of the rotor tooth portion 12b are not damaged as in the conventional case.

Although the embodiment has been described above based on the drawings, the specific configuration is not limited to this embodiment, and even if there is a design change within the scope of the gist of the present invention, it is included in the present invention. .

For example, the specific shapes and configurations of the adjustment return member, one-way clutch, return spring, etc. are not limited to the illustrated embodiments.

(Effects of the Invention) As explained above, in the present invention, in the drum brake having an auto-adjustment mechanism, the tool 1
The push-operated adjustment return member allows the adjustment lever to release the wheel engagement and rotate the adjustment wheel in the opposite direction at the same time, and the adjustment return member automatically returns to the original position when the tool is released. When performing the return operation, it is possible to reliably perform the return operation by simply repeating pushing and releasing operations using a single tool, without requiring visual inspection or damaging the teeth.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a drum brake according to an embodiment of the present invention, and FIG.
The figure shows the auto-adjust mechanism portion of the drum brake according to the embodiment, FIG. 3 is a cross-sectional view of the second figure, and FIG. 4 is an explanatory diagram of the operation of the auto-adjust mechanism in its return operation. 1...-Back plate 1a...Work hole 2...-Anchor 3...-Wheel cylinder (expansion means) 4...-Flake shell 6...Brake drum 10...-First adjustment socket 11... -Second adjustment socket 12...-Adjust wheel 13...Adjust lever 20...Adjust return rotor (adjust return member) 20a--Tool push part 20b--Cam part 21...One-way ratchet (one-way clutch) 22...-Adjust return spring (return spring)

Claims (1)

[Claims] A pair of brake shoes, one end of which is in contact with an anchor provided on the back plate, and the other end of which is provided with an expanding means, and the adjustment wheel is rotated in the forward direction by the operation of the adjustment lever accompanying braking. In the drum brake having an auto-adjust mechanism that automatically adjusts the gap between the brake shoes and the brake drum by extending the first adjustment socket and the second adjustment socket provided between the pair of brake shoes, A tool pushing part is interposed between the adjustment wheel and the adjustment lever and receives a pressing operation force from the outside. When a predetermined operating force is applied to this tool pushing part, the wheel rotates in the opposite direction and the adjustment lever and wheel are connected. An adjustment return member is provided with a cam portion for disengaging the mesh, and a rotary support portion that supports the adjustment return member on the adjustment wheel is provided, and the force applied to the adjustment return member is applied to the adjustment wheel only in the reverse rotation direction. A drum brake comprising: a one-way clutch that transmits the transmission; and a return spring that is connected to the adjustment return member and applies a return biasing force in the forward rotation direction to the adjustment return member and positions the adjustment return member in a return position. .