JPH10159877A - Shoe return structure of drum brake for inward expansion type vehicle - Google Patents

Abstract

(57) [Summary] [Object] To surely hold a parking lever in a non-braking state at a predetermined position, and effectively prevent occurrence of a tapping sound due to contact between a brake shoe and a parking lever. A web 5a is provided with a mounting hole 5d.
An engagement portion 20a and a stopper portion 20
b, lever restraining portion 20c and elastic legs 20d, 20d
And a lever guide portion 20e. Engagement part 20a
A locking piece 20f for locking the tip to the back plate surface of the web 5a, and a side piece 20g for making the locking side contact the outer surface of the back plate of the mounting hole 5d. A stopper 20i for supporting the projection 7a of the parking lever 7, a stopper 20i and a side piece 20g are provided on the stopper 20b.
Is provided. Elastic legs 20d, 20d are provided on the connecting piece 20h, and the ends of the elastic legs 20d, 20d are elastically contacted with the side surface of the back plate of the web 5a. A lever restraining portion 20c is connected to the stopper piece 20i, and the lever restraining portion 20c supports the side surface of the protrusion 7a of the parking lever 7 opposite to the back plate, and a gap C3 is set between the web 5a and the parking lever 7. I do.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inwardly expanding drum brake with an automatic brake clearance adjusting device used for a running vehicle such as an automobile or a motorcycle, and more particularly to a method for removing the drum brake from a vehicle body for maintenance or the like. The present invention also relates to a shoe return structure in which the diameter of a brake shoe that bites into a wear groove on the inner peripheral surface of a brake drum is reduced to release biting of the brake shoe.

[0002]

2. Description of the Related Art In an in-expandable vehicle drum brake used in a four-wheeled vehicle or the like, when the lining of a brake shoe wears due to repeated braking, the lining and the inner peripheral surface of the brake drum are damaged. Since the braking gap between them may expand beyond a predetermined amount, the initial braking may be delayed or the operation feeling may be impaired. By restricting the diameter-reduced position of the opened brake shoe to an outside position before the expansion, the increased braking clearance is automatically filled so that a constant braking clearance can always be obtained.

In such a configuration, by repeating the braking operation for a long period of time, a wear groove formed by sliding contact with the lining is formed on the inner peripheral surface of the brake drum. The lining of the brake shoe, which gradually restricts the reduced diameter position to the outside, cuts in.When the brake drum is removed for replacement or maintenance of the brake shoe, the wear groove of the brake drum interferes with the lining, In some cases, it is difficult to remove the parking lever. For example, as shown in Japanese Utility Model Publication No. 60-37469 or Japanese Utility Model Publication No. 61-45382, a parking lever provided between a back plate and a web of one brake shoe is used. There has been proposed a shoe return structure in which the lining bite is released.

In the former shoe return structure, a retraction restricting member composed of a combination of a stop pin and a compression coil spring is interposed between a web of one brake shoe and a parking lever. The large diameter head of the stop pin provided on one of the web and the parking lever is brought into contact with the other to regulate the diameter reduction position of the brake shoe and the retreat limit of the parking lever.

In the latter shoe return structure, a shoe clamp pin and a shoe clamp spring or a cap washer which resiliently holds the web of one of the brake shoes to the back plate are connected to a shoe clamp pin or a shoe washer. A portion is provided as a retraction restricting member, and the parking lever is brought into contact with the retraction restricting member to restrict the reduced diameter position of the brake shoe and the retreat limit of the parking lever.

[0006] In any of the drum brakes, when the brake drum is removed from the vehicle body by replacing the brake shoe or the like, a release tool such as a driver is inserted through a tool hole opened in the back plate, and the retraction restricting member is used by the release tool. By pushing the stop pin and the connecting part of the brake lever in the direction opposite to the back plate to release the engagement with the brake shoe and the parking lever, the parking lever is retracted farther to the outside of the back plate than usual, and at the same time, the brake shoe Is moved inwardly of the back plate to reduce the diameter to be smaller than the inner peripheral surface of the brake drum.

[0007]

However, in any of the shoe return structures, the parking lever is backlashed in the axial direction of the back plate due to the traveling vibration of the vehicle, and in particular, the leading end of the parking lever to which the wire cable is connected has one end. Heavy hitting of the brake shoe web may produce a tapping sound.

Accordingly, the present invention provides an inwardly expanding type which can securely prevent the occurrence of a hitting sound due to the contact between the brake shoe and the parking lever by securely holding the parking lever at the time of non-braking. An object of the present invention is to provide a shoe return structure for a vehicle drum brake.

[0009]

SUMMARY OF THE INVENTION In accordance with the above-mentioned object, the present invention has a pair of brake shoes arranged on a back plate fixed to a vehicle body so as to be able to expand and contract, and an expanding operation is provided between webs of both brake shoes. The brake gap automatic adjustment device that regulates the reduced diameter position of the brake shoe released from outside to the outside before the expansion and keeps the brake gap between the lining of both brake shoes and the inner peripheral surface of the brake drum constant Interposed,
Between the back plate and one of the webs,
A parking lever which is pulled inward by a wire cable in the back plate is disposed in parallel, and a rotation base end side of the parking lever is pivotally supported on one of the webs. Engage the retraction restriction member that regulates the retraction limit and one end of the braking gap automatic adjustment device,
By releasing the engagement between the retraction restricting member and the parking lever with a release tool inserted from a tool hole formed in the back plate to retract the brake shoes more than usual, both brake shoes can be used. In a shoe return structure of an in-expandable vehicle drum brake configured to have a diameter smaller than an inner peripheral surface of the brake drum, a mounting hole is formed in the one web, and the one web is provided in the retraction restricting member. An engagement portion that engages the anti-back plate side surface and the mounting hole to support the retraction restricting member on one web movably in the anti-back plate direction, and between the back plate and the one web, A stopper portion that supports the outer surface of the back plate of the parking lever and regulates a retreat limit of the parking lever; and a stopper portion opposite the back plate to the stopper portion. Then, a step portion or a bent portion that supports the parking lever, whose retraction limit is restricted by the stopper portion, on the side opposite to the back plate and holds the parking lever with a predetermined gap between the parking lever and the one web. And a pair of elastic legs that project from the back plate side of the stopper in the direction opposite to the back plate and protrude, and abut against the back plate side surface of one of the webs with elastic force across the mounting hole. Are provided.

[0010] With this configuration, the parking lever during non-braking is restricted in its retreat limit by contact with the stopper portion of the retraction restricting member engaged with the web of one of the brake shoes. Is regulated. Since the parking lever at the retreat limit position is supported with a predetermined gap between it and one of the webs by the lever restraining portion of the retraction restricting member, the parking lever can be moved in the axial direction of the back plate even during running vibration of the vehicle. No rattling occurs, and the generation of a tapping sound due to interference between the barking lever and the web of the brake shoe is prevented.

When the brake drum is to be removed from the vehicle body for replacement or maintenance of the brake shoes, a release tool such as a screwdriver is inserted through a tool hole opened in the back plate, and the retraction restricting member is moved by the release tool. When pushed in the plate direction, the pair of elastic legs open while sliding on the back put side surface of the web of one brake shoe, and the entire retraction control member moves in the direction opposite to the back plate, and the parking lever and the retraction control member The contact with the stopper is released. As a result, the parking lever retreats farther outward in the back plate than the normal retreat position restricted by the stopper portion of the retraction restricting member, and at the same time, the brake shoe moves inward in the back plate, and the inner periphery of the brake drum moves. Reduce diameter smaller than the surface.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 5 show a first embodiment of the present invention, in which a drum brake 1 is provided on a brake drum 2 which rotates integrally with wheels (not shown) in the direction of arrow A.
The brake shoe 4 on the leading side and the brake shoe 5 on the trailing side that are opposed to each other in the back plate 3 fixed to the vehicle body are expanded around the anchor 8 as a fulcrum by expanding the wheel cylinder 6 or the parking lever 7. The leading and trailing type inner-expansion type drum brake has brake shoes 4 and 5 in which the intermediate portions of the webs 4a and 5a are elastically held by the back plate 3 by shoe hold pins 9 and shoe clamp springs 10, respectively. One end and the other end of each of the webs 4a and 5a are supported by the wheel cylinder 6 and the anchor 8, respectively.

The brake shoes 4, 5 are provided with the above-mentioned webs 4a, 5a arranged in parallel with the back plate 3, and a rim 4 fixed to the outer edges of the webs 4a, 5a in a direction perpendicular to the webs.
b, 5b and linings 4c, 5c fixed to the outer peripheral surfaces of the rims 4b, 5b. Web 4a, 5
a, shoe return springs 11 and 12 are stretched inside the wheel cylinder 6 and outside the anchor 8, respectively.
Both brake shoes 4 and 5 are constantly urged in the diameter reducing direction. Further, an automatic braking clearance adjusting device 13 is disposed at a position inside the shoe return spring 11 on the wheel cylinder side. The braking gap C1 between the brake drum 5c and the inner peripheral surface of the brake drum 2 is always kept constant.

The wheel cylinder 6 includes the cylinder body 1
A pair of pistons 15, 15 are inserted into a cylinder hole 14 a formed through the cylinder body 4, and a hydraulic chamber 16 is defined between the pistons 15, 15, and a cylinder body 1 is formed.
One ends of webs 4a, 5a are supported on outer ends of pistons 15, 15 protruding from both ends of 4, respectively. The hydraulic chamber 16 of the wheel cylinder 6 is connected to a known hydraulic master cylinder separately provided via a brake hose (both not shown), and is generated in the hydraulic master cylinder by a braking operation of the driver. When the hydraulic pressure is supplied to the hydraulic chamber 16,
The pistons 15, 15 are pushed out of the cylinder hole 14a to both ends, and both brake shoes 4, 5
At the fulcrum, and the outer linings 4a and 5a are brought into sliding contact with the inner peripheral surface of the brake drum 2 to perform a braking action.

Between the back plate 3 and the web 5a of the brake shoe 5 on the trailing side, the above-mentioned parking lever 7 has its base end pivotally supported on one end of the web 5a by a support shaft 17, and 3 and the web 5a. One end of a wire cable 18 is connected to the distal end of the parking lever 7, and the protrusion 7
a is formed. A lever return spring 19 is wound around the wire cable 18 with one end elastically contacting the tip of the parking lever 7, and the parking lever 7 is always attached to the outside of the back plate by the elastic force of the lever return spring 19. The trailing limit of the trailing brake shoe 5 is restricted by the contact of the trailing limit member 20 with the web 5a of the trailing brake shoe 5.

The other end of the wire cable 18 is connected to a service brake operator such as a service lever or a service pedal in the driver's seat, and when the driver operates the service brake operator, the wire cable 18 is moved to a lever return spring. 19 is compressed and pulled to the left in FIG.
When the parking lever 7 pivots inward of the back plate (clockwise in FIG. 2) about the support shaft 17 and the operation of the service brake operator is released, the parking lever 7
However, while the wire cable 18 is pulled rightward in FIG. 2 by the restoring force of the lever return spring 19, the wire cable 18 pivots about the support shaft 17 in the outward direction of the back plate (counterclockwise in FIG. 2), thereby restricting retraction. It returns to the predetermined retreat limit position by contact with the member 20.

The braking gap automatic adjusting device 13 includes an operating arm 21
a is engaged with the web 4a of the brake shoe 4 on the leading side, and one end of the quadrant 21 is meshed with the quadrant 21. The web 5a and the parking lever 7 are overlapped and accommodated, and the plate-shaped strut 22 provided with the inner edge of the parking lever 7 abutting the slot 22a, the quadrant 21 and the strut 22 are engaged with each other. And a return spring 24 that pulls the strut 22 and the brake shoe 5 on the trailing side inward from each other.

The return spring 23 on the quadrant 21 side is
The set load is set lower than that of the return spring 24 on the brake shoe 5 side, and when the brake shoes 4, 5 are greatly expanded and the interval between the webs 4a, 5a is expanded more than usual, the quadrant 21 and the The strut 22 is separated from the return spring 23 while pulling the return spring 23, and the quadrant 21 rotates about the operation arm 21a as a fulcrum, and the quadrant 2
1 is engaged with the strut 22 again, so that the working arm 21a of the quadrant 21 and the slot 22 of the strut 22 are engaged with each other.
The interval between the brake drum 2 and the inner peripheral surface of the brake drum 2 is automatically reset.

The leading end of the brake shoe 4 is restricted in retreat by engagement of the web 4a with the working arm 21a of the quadrant 21, and the trailing end of the brake shoe 5 is formed by struts 22 on the inner edge. The parking lever 7 which is in contact with the slit 22 a is regulated via the support shaft 17. Between the bottom of the slit 22 a of the strut 22 and the inner edge of the web 5 a of the brake shoe 5, A gap C2 for reducing the diameter of the brake shoes 4, 5 is set in advance. The web 5a of the brake shoe 5 on the trailing side has a rectangular mounting hole 5
d is formed by piercing the long sides of the inner and outer surfaces of the back plate in the tangential direction of a circle with the center of the back plate 3 as a fulcrum, and the above-described retraction restricting member 20 is engaged with the mounting hole 5d. A grommet 25 is attached to the tool hole 3a of the back plate 3 provided substantially opposite to the retraction restricting member 20.

The retraction restricting member 20 is connected to one of the webs 5.
a into the mounting hole 5d and the side opposite to the back plate,
An engagement portion 20a for supporting the retraction restricting member 20 on one of the webs 5a so as to be movable in a direction opposite to the back plate; and a stopper portion 20b for restricting a retreat limit of the parking lever 7 between the back plate 3 and the web 5a. , Stopper part 20
b, the rear end of the parking lever 7 whose rearward limit is restricted by the stopper portion 20b is supported on the opposite side of the back plate, and the parking lever 7 is connected to the web 5a.
A lever restraining portion 20c that holds a predetermined gap C3 between the lever, a pair of elastic legs 20d, 20d protruding from the connecting piece 20h of the stopper portion 20b, and a parking lever 7 at the time of releasing the operation. Part 20b and lever restraining part 2
0c for guiding to a predetermined retreat position.

The engagement portion 20a of the retraction restricting member 20 includes a locking piece 20f longer than the short side of the mounting hole 5d and a locking piece 2f.
0e and a side piece 20g bent at a right angle. The stopper portion 20b is bent from the side piece 20g of the engagement portion 20a in parallel with the locking piece 20f, and the locking piece 20f is formed.
A connecting piece 20h extending approximately half the length of the side piece 20g, bent from the connecting piece 20h in parallel with the side piece 20g, and
And a stopper piece 20i extending approximately half as long as 0 g.

The lever restraining portion 20c includes a stopper portion 20b
And a short piece protruding from the stopper piece 20i of the engaging part 20a in parallel with the locking piece 20f.
e is tapered and protrudes toward the distal end side of the locking piece 20f. Engaging part 20a excluding elastic legs 20d, 20d
The stopper portion 20b, the lever suppressing portion 20c, and the lever guide portion 20e are formed to have substantially the same length as the inside and outside surfaces of the mounting plate 5d and the elastic legs 20d, 2d.
Reference numeral 0d protrudes from both ends of the connecting piece 20h in the shape of a C in the direction of the locking piece 20f.

The retraction restricting member 20 constructed as described above
The cover 5f of the engaging portion 20a covers the entirety of the mounting hole 5d on the side opposite to the back plate, while the tip of the locking piece 20f is located on the inner side of the web 5a behind the mounting hole 5d.
Of the side plate 20g
The elastic leg portion that makes the 0f side abut against the outer surface of the back plate of the mounting hole 5d, makes the connecting side of the side piece 20g protrude toward the back plate from the mounting hole 5d, and opens from the connecting piece 20h in a C-shape. The elastic legs 20d, 20d are bent back into an arc shape while sandwiching the mounting hole 5d.
The abutment of the member 5 makes contact with the side surface of the back plate of the web 5a with an appropriate elastic force, so that the retraction restricting member 20 is attached to the web 5a.

With this attachment, the stopper piece 20i, which is parallel to the side piece 20g, is disposed between the web 5a and the back plate 3 so as to face the center of the back plate 3, and the lever restraining portion 20c is connected to the web 5d. A gap C3 is provided between the back guide and the side surface of the back plate, and the end of the lever guide portion 20e protrudes into the mounting hole 5d.

The parking lever 7 at the time of non-braking, which is resiliently pushed by the return spring 19 of the wire cable 18, is restricted in its retreat limit by the contact between the projection 7a and the stopper piece 20i of the retreat restricting member 20, and at the same time the brake shoe. The diameter reduction positions of 4 and 5 are regulated. The parking lever 7 in the retreat limit position is
The side surface of the projection 7a opposite to the back plate is supported by the lever restraining portion 20c of the retraction restricting member 20, and a predetermined gap C3 is set between the web 5a of the brake shoe 5 and the parking lever 7.

When the wire cable 18 is pulled by the operation of the parking brake operator and the parking lever 7 pivots about the support shaft 17 in the back plate direction (clockwise direction in FIG. 2), the protrusion 7a moves backward. Control member 20
Away from the stopper piece 20i and the lever restraining portion 20c,
The parking lever 7 moves to the left in FIG. 1 to open both brake shoes 4 and 5 to bring the linings 4 a and 5 a into sliding contact with the inner peripheral surface of the brake drum 2.

Further, since the parking lever 7 after releasing the braking by releasing the pulling of the wire cable 18 by the parking brake operator is free to move in the axial direction of the back plate, as shown in the imaginary line in FIG. There is a case where the parking shoe 7 tries to return the brake shoe 5 closer to the web 5a than the gap C3 with the web 5a in the retreat limit direction (the right direction in FIG. 1) outside the back plate.
a of the a on the side opposite to the back plate comes into contact with the tapered lever guide portion 20e provided on the retraction restricting member 20, and is gradually translated in the back plate direction by the guide of the lever guide portion 20e; It returns to the normal retreat limit position (solid line state in FIG. 1) supported by the stopper piece 20i and the lever restraining portion 20c.

The reduced diameter position of the brake shoes 4, 5 is gradually adjusted to the outside of the back plate by the braking gap automatic adjusting device 13 with the wear of the linings 4c, 5c. When the brake drum 2 is to be removed for replacement or maintenance of the brake shoes 4 and 5 from a state in which it has bitten into the wear groove formed on the inner peripheral surface of the rim, a release tool such as a screwdriver is inserted into the tool hole 3a from which the grommet 25 is removed. When the connecting piece 20h of the retraction restricting member 20 is pushed in the direction opposite to the back plate with the tip of the release tool, a pair of elastic legs 20d,
20d is opened while sliding on the side of the back put of the web 5a of the brake shoe 5 on the trailing side, so that the entire retraction restricting member 20 moves in the direction opposite to the back plate.

When the elastic legs 20d, 20d are compressed to be smaller than the gap C3 between the web 5a of the brake shoe 5 and the parking lever 7, the stopper piece 20i of the stopper 20b is pushed by the protrusion of the parking lever 7. 7a, the parking lever 7
Is retracted farther outward in the back plate than the normal retreat position regulated by the stopper piece 20i (the state shown in FIG. 3), and at the same time, the brake shoe 5 on the trailing side is in contact with the bottom of the slit 22a of the strut 22. The gap C between
The brake shoes 4 and 5 are moved toward the inside of the back plate while filling them, and the diameter of the brake shoes 4 and 5 is reduced to be smaller than the inner peripheral surface of the brake drum 2, and the brake drum 2 can be removed.

When the stopper piece 20i of the stopper portion 20b supports the protrusion 7a of the parking lever 7 and regulates the retreat limit of the parking lever 7, the retraction regulating member 20 of this embodiment is used. The lever restraining portion 20c
Since the predetermined gap C3 is maintained between the web 5a of the brake shoe 5 and the parking lever 7 by supporting the side surface of the projection 7a opposite to the back plate, the parking lever 7 plays back in the direction of the web 5a due to the running vibration of the vehicle. It does not stick, and it is possible to effectively prevent the generation of a tapping sound due to the interference between the parking lever 7 and the web 5a.

The parking lever 7 after braking is released
However, when it is attempted to return closer to the web 5a than the gap C3 with the web 5a, the lever restraining portion 20c and the lever guide portion 20e inclined in the direction of the stopper piece 20i cause the parking lever 7 to move outward from the back plate. The parking lever 7 is gradually guided in the direction of the back plate with the retreat, and the parking lever 7 can be reliably returned to the normal retreat limit supported by the stopper piece 20i and the lever restraining portion 20c.

Further, the retraction restricting member 20 of this embodiment locks the distal end of the locking piece 20f of the engaging portion 20a to the back plate surface of the web 5a inside the back plate with respect to the mounting hole 5d. While the side piece 20g of the joint 20a is in contact with the outer surface of the back plate of the mounting hole 5d, the distal ends of the elastic legs 20d, 20d are brought into contact with the side surface of the back plate of the web 5a with an appropriate elastic force. 5a, the stopper piece 20i of the stopper portion 20b
Even if the elastic force of the return spring 19 is applied as a rotational moment through the parking lever 7, the mounted state of the retraction restricting member 20 can be reliably maintained.

FIGS. 6 and 7 show the second and third embodiments of the present invention using a retraction restricting member different from the first embodiment. The retraction restricting member 30 of the second embodiment shown in FIG. 6 includes an engaging portion 31a including a locking piece 31f, a side piece 31g, and a locking portion 31j, and a stopper portion 31b including a connecting piece 31h and a stopper piece 31i. , A lever restraining portion 31c, a pair of elastic legs 31d, 31d, and a lever guide portion 31e.
In this embodiment, the locking piece 31f of the engaging portion 31a is moved from the side piece 31g to the connecting piece 3 of the stopper portion 31b.
1h, a short piece protruding in the opposite direction to the lever guide part 3
This is different from the first embodiment in that a short piece hooking portion 31j is provided at the tip of 1e in parallel with the side piece 31g.

The retraction restricting member 30 locks the locking piece 31f to the back plate surface of the web 5a outside the back plate with respect to the mounting hole 5d, and connects the opposing side piece 31g and the locking portion 31j to the mounting hole. The retraction restricting member 3 is brought into contact with the inner and outer surfaces of the back plate 5d with an elastic force, and the distal ends of the elastic legs 31d, 31d respectively contact the side surfaces of the back plate of the web 5a with an appropriate elastic force.
0 is attached to the web 5a.

The retraction restricting member 40 of the third embodiment shown in FIG.
The locking piece 31f of the locking portion 31a protrudes from the locking piece 31j in the direction opposite to the side piece 31b, and the lever restraining portion 31c provided on the retraction control member 30 of the second embodiment is omitted. The second embodiment differs from the second embodiment in that the tapered lever guide portion 31e is directly connected to the stopper piece 31i.
The retraction restricting member 40 is attached to the web 5a in the same manner as the retraction restricting member 30 of the second embodiment, except that the f is locked on the anti-backplate surface of the web 5a inside the backplate with respect to the mounting hole 5d.

In the retraction restricting member 40 of this embodiment, the lever guide portion 31e also serves as the lever restraining portions 20c, 31c of the first and second embodiments, and is located between the stopper piece 31i of the stopper portion 31b. A predetermined gap C3 is maintained between the web 5a of the brake shoe 5 and the parking lever 7 by supporting the side edge of the projection 7a of the parking lever 7 opposite the back plate at the inner angle θ. 2nd, 3rd
Although the retraction restricting members 30 and 40 of the embodiment have a different configuration from the retraction restricting member 20 of the first embodiment, the same effects as those of the first embodiment described above can be obtained.

In the present invention, if a predetermined gap can be set between the parking lever and the web of one of the brake shoes on the side to which the parking lever is attached by the lever restraining portion of the retraction restricting member, the lever restraining portion is circular. And other shapes such as arcs and waveforms, and the lever restraining portion does not necessarily have to be parallel to the parking lever. Further, the protrusion of the parking lever and the lever guide of the retraction restricting member shown in the embodiment are useful in practicing the present invention. Can be achieved.

[0038]

According to the present invention, in the shoe return structure for a drum brake for an inwardly expanding vehicle, a mounting hole is formed in one of the webs on the side where the parking lever is mounted, and the retraction control is performed on the one web. An engaging portion that engages the member on the side opposite to the back plate of the one web and the mounting hole, and supports the retraction restricting member on the one web movably in the direction opposite to the back plate; And a stopper portion that supports the outer surface of the back plate of the parking lever and regulates the retreat limit of the parking lever, and the retreat limit is regulated by the stopper portion continuously to the back plate side of the stopper portion. A lever restraining portion that supports the parking lever opposite to the back plate and holds the parking lever with a predetermined gap between the parking lever and the one web; By providing a pair of elastic legs that project from the back plate side of the lid portion while expanding in the direction opposite to the back plate, and abut against the back plate side surface of one of the webs with elastic force with the mounting hole interposed therebetween. Since the parking lever at the time of non-braking is held with a predetermined gap between the parking lever and the web of one brake shoe, the parking lever does not rattle in the web direction due to the running vibration of the vehicle, and the parking lever and the one brake shoe are not moved. Hitting due to interference with the web can be effectively prevented.

[Brief description of the drawings]

FIG. 1 is a sectional view taken along line II of FIG. 2 showing a first embodiment of the present invention;

FIG. 2 is a front view of a drum brake showing a first embodiment of the present invention.

FIG. 3 is a sectional view of a main part during a shoe return operation showing the first embodiment of the present invention.

FIG. 4 is a sectional view taken along the line IV-IV of FIG. 1, showing a first embodiment of the present invention;

FIG. 5 is a perspective view of a retraction restricting member showing a first embodiment of the present invention.

FIG. 6 is a sectional view of a main part showing a second embodiment of the present invention.

FIG. 7 is a sectional view of a main part showing a third embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Inner drum brake 1 2 ... Brake drum 3 ... Back plate 3a ... Tool hole 4 ... Brake shoe on the leading side 5 ... Brake shoe on the trailing side 7 ... Parking lever 4a, 5a ... Web 4b, 5b ... Rim 4c, 5c: lining 5d: mounting hole formed in the web 5a of the trailing side brake shoe 13: automatic adjustment device for braking gap 17: support shaft of the parking lever 7 18: wire cable connected to the tip of the parking lever 7 Reference numeral 19: lever return spring wound around the wire cable 18 20: retraction restricting member 21: quadrant of the automatic braking gap adjusting device 13 25: grommet 20a: engaging portion 20b: stopper portion 20c: lever suppressing portion 20d: elastic leg portion 20e: Lever guide section 20f: Locking piece 20g: Side piece 20h ... Connection piece 20i Stopper piece 30, 40 Retraction restricting member 31a Engagement part 31b Stopper part 31c Lever suppression part 31d Elastic leg 31e Lever guide part 31f Lock piece 31g Side piece 31h Connection piece 31i Stopper piece 31j Latch A A Rotation direction of brake drum C1 Brake gap set between linings 4c and 5c and inner peripheral surface of brake drum 2 C2 Reduce diameter of brake shoes 4 and 5 C3: gap between parking lever 7 and web 5a of trailing side brake shoe 5 θ: inner angle between lever guide portion 31e and stopper piece 31i of stopper portion 31b

Claims (1)

[Claims] 1. A pair of brake shoes are disposed on a back plate fixed to a vehicle body so as to be able to expand and contract, and the reduced diameter position of the brake shoes whose expansion operation has been canceled is set between webs of both brake shoes before the expansion. A brake clearance automatic adjusting device for maintaining a constant brake clearance between the lining of both brake shoes and the inner peripheral surface of the brake drum, and interposing the back plate and one of the webs. A parking lever pulled inward by a wire cable in the back plate is disposed in parallel, and the base end of the parking lever is pivotally supported on one of the webs. A retraction restricting member for restricting the retraction limit when not in operation is engaged with one end of the braking gap automatic adjusting device, and a release tool inserted from a tool hole opened in the back plate is provided. By disengaging the retraction restricting member and the parking lever and retracting the brake shoe more than usual, the diameter of both brake shoes is reduced from the inner peripheral surface of the brake drum. In the shoe return structure for an extended vehicle drum brake, a mounting hole is formed in the one web, and the retraction restricting member is engaged with the side opposite to the back plate of the one web and the mounting hole, and retreated. An engaging portion for supporting the regulating member on one of the webs so as to be movable in a direction opposite to the back plate, and an outer surface of the back plate of the parking lever supported between the back plate and the one web; A stopper portion for restricting the retraction limit, and a reverse lever of the parking lever, the retraction limit being restricted by the stopper portion, being continuous with the back plate side of the stopper portion. A lever restraining portion that supports the parking plate side and holds the parking lever with a predetermined gap between the web and the one web, and while expanding the stopper in the direction opposite to the back plate from the back plate side of the stopper portion. A shoe return structure for a drum brake for an in-expandable vehicle, comprising a pair of elastic legs protruding and abutting on a side surface of a back plate of one of the webs with an elastic force across the mounting hole.