JPH07269616A - Automatic clearance adjusting device for drum brake - Google Patents

Abstract

PURPOSE:To obtain a clearance automatic adjusting device for a drum brake, capable of preventing a dragging phenomenon according to over adjust from being generated. CONSTITUTION:A one-way stopper 21 for restraining the turning movement of a guide gear 13 in the adjust direction A and allowing the turning movement in the opposite adjust direction D after being engaged with the guide gear 13 is provided. When turning force in the opposite adjust direction D is applied to an adjust lever 12 by the contraction after a drum 1 is thermally expanded and then contracted, the adjust lever 12 is turned in the opposite adjust direction D since the turning movement of the guide gear 13 is allowed in relation to the opposite adjust direction. Therefore, the position of a brake shoe 3 can be returned to an original position where a gap is automatically adjusted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for automatically adjusting a clearance of a drum brake used in a vehicle.

[0002]

2. Description of the Related Art An example of a conventional automatic drum brake clearance adjusting device is shown in FIGS.
In the figure, a drum 1 that rotates together with wheels (not shown)
A pair of brake shoes 2 and 3 are provided so as to face each other on the inner circumference of the. The pair of brake shoes 2 and 3 are rotatably supported by an anchor 4 provided on the base end side. A wheel cylinder 5 is interposed between the tip ends of the pair of brake shoes 2 and 3.

When the brake pedal is depressed, hydraulic pressure is applied to the piston in the wheel cylinder 5 to expand the pair of brake shoes 2 and 3, and the lining 6 attached to the pair of brake shoes 2 and 3 is a drum. Sliding to 1 generates braking force. In the figure, reference numeral 7 is a return spring which urges the pair of brake shoes 2 and 3 toward the inner peripheral side of the drum 1. Between the pair of brake shoes 2 and 3, an automatic adjuster mechanism 8 which is activated by the abrasion of the lining 6 attached to the pair of brake shoes 2 and 3 is interposed.

The automatic adjuster mechanism 8 includes a plate 9
, The shaft 10, the shaft spring 11, and the adjusting lever 12
And a guide gear 13. The plate 9 is arranged such that the base end is in contact with one brake shoe 2 and the tip side is extended to the other brake shoe 3.
A plate elongated hole 14 extending in the longitudinal direction is formed on the tip side of the plate 9. The shaft 10 is movably inserted into the plate elongated hole 14. An adjust lever 12 is attached to the shaft 10.

A shaft spring 11 is provided between the shaft 10 and the one brake shoe 2, and biases the shaft 10 and thus the adjust lever 12 toward the one brake shoe 2 side. The web 15 of the other brake shoe 3 is formed with a web elongated hole 16 along the forming direction of the plate elongated hole 14. A guide gear 13 is held on the plate 9. The adjusting lever 12 is provided with adjusting lever side teeth 18 that mesh with the claw portions 17 inserted into the web elongated holes 16 and the guide gears 13.

In this automatic device for adjusting the clearance of the drum brake, when the lining 6 is not worn, as shown in FIG. Hole first wall portion 19
Say. ) And the claw portion 17 has a gap a (the length is a), the gap between the lining 6 and the drum 1 (hereinafter referred to as shoe clearance) b (the length is b) is shorter (a>).
b). The portion of the web elongated hole 16 that faces the web elongated hole first wall portion 19 is hereinafter referred to as a 20 web elongated hole second wall portion 20 for convenience.

When the brake operation is performed, FIG.
As shown in FIG. 7, when the pair of brake shoes 2 and 3 are expanded and the pair of brake shoes 2 and 3 is displaced by the length b with respect to the drum 1, the lining 6 slides on the drum 1 to generate a braking force. At this stage, the gap a is left between the first web elongated wall portion 19 and the claw portion 17, and the adjusting lever 12 does not receive the force from the other brake shoe 3 and does not rotate.

When the lining 6 is worn more and more, and the shoe clearance b is longer than the clearance a as shown in FIG. 18 and the shoe clearance b is longer than the clearance a (a <b), the braking operation is shown in FIG. So that the pair of brake shoes 2,
Due to the expansion of 3, the pair of brake shoes 2 and 3 is moved to the drum 1.
On the other hand, when the length a is displaced, the claw portion 17 is pushed by the web long hole first wall portion 19. And the adjust lever 12 is
By being displaced toward the drum 1 side against the shaft spring 11, the adjust lever side teeth 18 are released from the guide gear 13 and unlocked, and the claw portion 17 is pressed against the web elongated hole first wall portion 19. As a result, the adjusting lever 12 rotates clockwise A in FIG. 19 (hereinafter referred to as the adjusting direction) A.

When the brake operation is stopped, the pair of brake shoes 2 and 3 receive the spring force of the return spring 7 so that the pair of brake shoes 2 and 3 are moved to the drum 1.
When the adjusting lever 12 is displaced by receiving the force of the shaft spring 11, the adjusting lever side teeth 18 mesh with the guide gear 13. At this time, the position of the adjust lever side teeth 18 meshing with the guide gear 13 changes due to the adjust lever 12 rotating by a predetermined amount, and the shoe clearance b is shorter than the gap a (a> b). It is returned to the state. As described above, in the automatic device for adjusting the clearance of the drum brake, when the wear of the lining 6 is increased by the auto adjuster mechanism 8 by a reference value or more, the shoe clearance b is adjusted so as to be kept within a certain range, and thus the brake pedal feeling is improved. It works to keep constant.

A device of the same type as the above-described automatic device for adjusting the clearance of the drum brake is disclosed in Japanese Utility Model Laid-Open No. 3-41235.

[0011]

By the way, in the above-described automatic device for adjusting the clearance of the drum brake, the drum 1 thermally expands and the shoe clearance b reaches the reference value (a <b.
Therefore, even if the lining 6 is not worn out, the auto adjuster mechanism 8 may operate, that is, so-called over-adjustment may occur. In the over-adjusted state, when the temperature of the drum 1 decreases and the expanded drum 1 contracts to its original size, the brake shoe slides in contact with the drum 1, so-called dragging occurs, which is very rare. Dimensional control of parts becomes difficult.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an automatic clearance adjusting device for a drum brake capable of preventing the occurrence of a dragging phenomenon due to overadjustment.

[0013]

In order to achieve the above object, the invention as set forth in claim 1 is provided with a pair of brake shoes opposed to each other on the inner circumference of a drum, and between the pair of brake shoes. In an automatic gap adjusting device for a drum brake, which is provided with an automatic adjuster mechanism that operates by abrasion of the lining attached to the brake shoe, and maintains the gap between the lining and the drum within a certain range by the automatic adjuster mechanism, A plate in which an auto-adjuster mechanism is arranged such that the base end is in contact with one brake shoe and the tip side is extended to the other brake shoe, and a plate elongated hole extending in the longitudinal direction is formed on the tip side; A shaft to be inserted into the long hole, a shaft spring for urging the shaft toward one of the brake shoes, and a plate spring along the forming direction of the plate long hole. Of the other brake shoe, a web elongated hole formed in the web, an adjust lever attached to the shaft having a claw portion inserted into the web elongated hole, and a plate rotatably provided in the adjust lever. A guide gear that meshes with the adjusting lever side teeth, and a one-way stopper that engages with the guide gear to prevent rotation of the guide gear in the adjusting direction and allows rotation in the anti-adjusting direction. To do.

In order to achieve the above object, the one-way stopper has stopper pawls which are biased by a spring and engages with the guide gear, and the guide gear and the stopper pawl have an adjusting direction. It is characterized in that the meshing portion during rotation is formed in a plane and the meshing portion during rotation in the anti-adjustment direction is formed in a curved surface.

In order to achieve the above-mentioned object, a third aspect of the present invention is to provide a pair of brake shoes facing each other on the inner circumference of the drum, and affix the brake shoes between the pair of brake shoes. An automatic adjuster mechanism is provided as a base in an automatic gap adjuster for a drum brake in which an automatic adjuster mechanism that operates due to wear of the lining is interposed, and the automatic adjuster mechanism keeps the clearance between the lining and the drum within a certain range. A plate having an end abutting one brake shoe and a tip side extending to the other brake shoe and having a plate elongated hole extending in the longitudinal direction on the tip side, and a shaft inserted into the plate elongated hole A shaft spring for urging the shaft toward one of the brake shoes, and the other brake system along the forming direction of the plate elongated hole. Of the adjustment lever side teeth formed on the adjustment lever and the adjustment lever attached to the shaft, which has a long slot formed in the web of the web and a claw portion to be inserted into the long slot of the web. The guide gear includes a guide gear for inserting a shaft portion into a guide gear elongated hole formed to extend to the meshing portion side, and a guide gear spring for urging the guide gear toward the meshing portion side of the adjust lever side teeth. It is characterized by

In order to achieve the above-mentioned object, the invention according to claim 4 is provided with a pair of brake shoes facing each other on the inner circumference of the drum, and the pair of brake shoes are attached to the brake shoes. An automatic adjuster mechanism is provided as a base in an automatic gap adjuster for a drum brake in which an automatic adjuster mechanism that operates due to wear of the lining is interposed, and the automatic adjuster mechanism keeps the clearance between the lining and the drum within a certain range. A plate having an end abutting one brake shoe and a tip side extending to the other brake shoe and having a plate elongated hole extending in the longitudinal direction on the tip side, and a shaft inserted into the plate elongated hole A shaft spring for urging the shaft toward one of the brake shoes, and the other brake system along the forming direction of the plate elongated hole. Adjustment lever attached to the shaft having a web elongated hole formed in the web, a claw portion to be inserted into the web elongated hole, and an adjustment lever engaging with adjustment lever side teeth formed on the adjustment lever. And a one-way stopper that inhibits rotation in the adjusting direction and allows rotation in the anti-adjusting direction.

[0017]

According to the structure of the invention described in claim 1, when the drum thermally expands and then contracts, and the contracting force acts on the adjusting lever in the direction opposite to the adjuster direction, the guide gear of the guide gear moves in the same direction. Because rotation is allowed,
The adjust lever is pushed back.

According to the second aspect of the present invention, the guide gear and the stopper claw are formed with curved engagement portions during rotation in the anti-adjusting direction, so that the guide gear is anti-adjusted via the adjusting lever. When a force in the direction is received, a component force in the counter-urging direction of the spring acts on the stopper claw, and the engagement between the stopper claw and the guide gear is released.

According to the third aspect of the invention, when the drum thermally expands and then contracts, and the contracting force acts on the adjusting lever in the direction opposite to the adjuster direction, the guide gear becomes rotatable. Accordingly, the guide gear rotates while being displaced along the guide gear long hole against the spring force of the shaft spring and the guide gear spring, so that the adjust lever rotates in the direction opposite to the adjuster direction.

According to the fourth aspect of the invention, the drum is thermally expanded and then contracted, and when the contraction force acts on the adjust lever in the direction opposite to the adjuster, the stopper rotates in the same direction. By allowing it, the adjust lever rotates in the direction opposite to the adjuster without being restrained by the stopper.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An automatic drum brake clearance adjusting device according to a first embodiment of the present invention will now be described with reference to FIGS.
2, with reference to FIGS. 15 and 16. In the figure, a pair of brake shoes 2 and 3 are provided facing each other on the inner periphery of a drum 1 that rotates together with wheels (not shown). The pair of brake shoes 2 and 3 are rotatably supported by an anchor 4 provided on the base end side. A wheel cylinder 5 is provided on the front end side of the pair of brake shoes 2 and 3. By depressing the brake pedal, hydraulic pressure acts on the piston in the wheel cylinder 5 to expand the pair of brake shoes 2 and 3, and the lining 6 provided on the pair of brake shoes 2 and 3 slides on the drum 1. Then, the braking force is generated.

A return spring 7 is stretched around the tip ends of the pair of brake shoes 2 and 3 to urge the pair of brake shoes 2 and 3 toward the inner peripheral side of the drum 1. Between the pair of brake shoes 2 and 3, an automatic adjuster mechanism 8 which is activated by the abrasion of the lining 6 attached to the pair of brake shoes 2 and 3 is interposed.

The automatic adjuster mechanism 8 includes a plate 9
, The shaft 10, the shaft spring 11, and the adjusting lever 12
The guide gear 13 and the one-way stopper 21 are included. The plate 9 has its base end abutted on one brake shoe 2 and its tip end on the other brake shoe 3
It is extended and arranged. A plate elongated hole 14 extending in the longitudinal direction is formed on the tip side of the plate 9. The shaft 10 is movably inserted into the plate elongated hole 14.

An adjust lever 12 is attached to the shaft 10. A shaft spring 11 is provided between the shaft 10 and the one brake shoe 2, and biases the shaft 10 and thus the adjust lever 12 toward the one brake shoe 2 side. The web 15 of the other brake shoe 3 is formed with a web elongated hole 16 along the forming direction of the plate elongated hole 14. A guide gear 13 is rotatably supported by the plate 9.

The adjusting lever 12 has a web elongated hole 1
Adjusting lever side teeth 18 that mesh with the claw portion 17 and the guide gear 13 to be inserted into the gear 6 are formed. When the lining 6 is not worn, the web elongated hole first wall portion 19
The shoe clearance b (length b) is short (a> b) with respect to the clearance a (length a) of the claw portion 17.

The adjusting lever 12 is separated from the guide gear 13 at the time of adjusting (see FIG. 2).
By rotating in the clockwise direction A, the shoe clearance b has a smaller value than the clearance a.
When the adjusting lever side teeth 18 and the guide gear 13 are engaged, the adjusting lever 12 moves in the adjusting direction A
When the guide gear 13 is turned to, the guide gear 13 receives a force in the counterclockwise direction B in FIG. 2 (hereinafter referred to as the adjusting direction of the guide gear 13) B.

The one-way stopper 21 has a bottomed cylindrical guard 22 fixed to the plate 9, a stopper claw 23 housed in the guard 22, and an interposition between the stopper claw 23 and the bottom of the guard 22. The stopper spring 24 and the stopper spring 24
The stopper claw 23 is engaged with the guide gear 13 by the urging force.

The guide gear 13 and the stopper claw 23 are formed such that the meshing portion 25 when the adjusting direction B rotates and the meshing portion 26 when the anti-adjusting direction E rotates are curved. In addition, the adjust lever side teeth 18 have a curved surface and a flat surface corresponding to the curved surface and the flat surface of the guide gear 13, respectively.

In this drum brake automatic clearance adjusting device, a brake operation is performed and a pair of brake shoes 2,
When the pair of brake shoes 2 and 3 are displaced by the length b with respect to the drum 1, the lining 6 slides on the drum 1 to generate a braking force. At this stage, the gap a is left between the first web elongated wall portion 19 and the claw portion 17, and the adjusting lever 12 does not receive the force from the other brake shoe 3 and does not rotate.

When the lining 6 is worn more than the reference value and the shoe clearance b is longer than the clearance a (a <b), the brake operation is performed and the pair of brake shoes 2 and 3 are expanded. A pair of brake shoes 2,
When 3 is displaced with respect to the drum 1 by the length a, the claw portion 17 is pushed by the web long hole first wall portion 19. Then, the adjusting lever 12 is displaced toward the drum 1 side against the shaft spring 11, so that the adjusting lever side teeth 18 are guided by the guide gear 1.
3 is released from the lock, and the claw 1
The adjusting lever 12 rotates in the adjusting direction A when 7 is pushed by the web elongated hole first wall portion 19.

When the brake operation is stopped, the spring force of the return spring 7 is received and the pair of brake shoes 2 and 3 is moved to the drum 1.
When the adjusting lever 12 is displaced by receiving the force of the shaft spring 11, the adjusting lever side teeth 18 mesh with the guide gear 13. At this time, the position of the adjust lever side teeth 18 meshing with the guide gear 13 is changed due to the adjust lever 12 rotating by a predetermined amount, and the shoe clearance b is shorter than the gap a (a> b). Will be returned. In this way, the lining 6
If the wear of the shoe exceeds the reference value, the shoe clearance b
Is adjusted so that it is kept within a certain range, and thus the brake pedal feeling is always kept constant.

The adjusting lever side teeth 18 are provided on the guide gear 13.
In the state in which the guide gear 13 is engaged with the adjust lever 12, even if a force in the adjuster direction is applied to the adjust lever 12, the flat surface of the guide gear 13 engages with the flat surface of the stopper claw 23 and the rotation of the guide gear 13 in the adjust direction B is restricted. By this, the rotation of the adjusting lever 12 is suppressed, and the adjusting lever 12 is held at an appropriate rotating position.

As described above, when the lining 6 is worn by the auto adjuster mechanism 8 beyond the reference value, the shoe clearance b is adjusted so as to be kept within a certain range, and the brake pedal feeling is constantly kept constant. is doing.

When the drum 1 thermally expands and the shoe clearance b reaches the reference value (the relationship of a <b) while the wear of the lining 6 is not advanced, the automatic adjuster mechanism 8 operates in the same manner as described above. It will operate, so-called over-adjustment. Then, in the over-adjusted state, when the temperature of the drum 1 decreases and the expanded drum 1 contracts to the original size, the drum 1 pushes the other brake shoe 3 and the web long hole second wall portion 20 causes the claw portion 17 to move. Then, the adjusting lever 12 receives a force in a direction (counter-adjusting direction) D opposite to the adjusting direction A.

Then, the guide gear 13 meshing with the adjusting lever side teeth 18 receives a force in the direction (counter-adjusting direction) E opposite to the adjusting direction B. At this time, the stopper claw 2
The curved surface of the guide gear 13 is engaged with the curved surface of the guide gear 13. When the guide gear 13 exerts a force in the anti-adjustment direction E on the stopper pawl 23, the stopper pawl 23 is pushed below the guard 22 to guide the guide gear 13. 13 is rotated without being restricted by the one-way stopper 21, and accordingly, the adjusting lever 12 is pushed back in the anti-adjustment direction D, and the position of the other brake shoe 3 is returned to the original position adjusted by the adjustment. You can

Next, a second embodiment of the present invention will be described with reference to FIGS.
It will be described based on. In the second embodiment, the one-way stopper 21 is omitted as compared with the first embodiment. In the figure, the plate 9 has a guide gear elongated hole 28 into which the shaft portion 27 of the guide gear 13 is inserted.
It is formed so as to extend in the meshing direction between the adjusting lever 12 and the adjusting gear 12, and the shaft portion 27 of the guide gear 13 and by extension the guide gear 13 is formed.
Are able to move. Shaft part 2 of guide gear 13
A guide gear spring 29 is stretched between the plate 7 and the plate 9, and the guide gear 13 and the adjust lever side teeth 1 are provided.
The guide gear 13 is biased toward the meshing portion side of 8. Further, the shapes of the adjusting lever side teeth 18 and the guide gear 13 are different from those of the first embodiment, and the adjusting direction A of the adjusting lever side teeth 18 has a flat surface and a curved surface on the front side and the rear side, respectively. The front side and the rear side are curved and flat, respectively.

In this automatic device for adjusting the clearance of the drum brake, during adjustment, the adjusting lever 12 moves rightward in FIG. 6 against the shaft spring 11 and the guide gear 13 and the adjusting lever side teeth 18 are disengaged. When the adjusting lever 12 rotates in the adjusting direction to change the position of the adjusting lever side teeth 18 meshing with the guide gear 13 and the wear of the lining 6 advances beyond the reference value, the shoe clearance b is kept within a certain range. Adjust to keep. The guide gear 13 is biased by the guide gear spring 29 toward the meshing portion side of the adjust lever side teeth 18, but the shaft portion 27 of the guide gear 13 is locked to the wall portion of the guide gear elongated hole 28. Therefore, at the time of adjusting, the guide gear 13 and the adjusting lever side teeth 18 are disengaged from each other.

After the over-adjustment, the drum 1 contracts so that the drum 1 is engaged with the other brake shoe 3 through the claw portion 1.
7 and push the adjusting lever 12 to the opposite direction D
Is applied to the guide gear 13,
The guide gear 13 moves in the direction away from the adjust lever 12 against the guide gear spring 29, and the engagement with the adjust lever side teeth 18 is released. Along with this, the adjusting lever 12 is rotated in the anti-adjustment direction D, and the position of the other brake shoe 3 is returned to the original position where the adjustment is adjusted (over-adjustment is eliminated).
It will be.

Next, a third embodiment of the present invention will be described with reference to FIGS. In the third embodiment, the guide gear 13 is omitted as compared with the first embodiment. In the figure, the one-way stopper 21 has a guard 22 formed with a lid 30 for restricting the displacement of the stopper claw 23. A stopper claw 23 of a one-way stopper 21 is directly meshed with the adjust lever side tooth 18. In this case, the shapes of the adjusting lever side teeth 18 and the stopper claws 23 are different from those of the first embodiment, and the adjusting lever side teeth 1 are different from each other.
The front and rear sides of the adjusting direction A in FIG. 8 are flat and curved, and the stopper claw 23 is a flat and curved portion of the adjust lever side teeth 18, respectively.
It is on a flat surface.

In this automatic device for adjusting the clearance of the drum brake, during adjustment, the adjusting lever 12 moves rightward in FIG. 9 against the shaft spring 11 to disengage the stopper claw 23 and the adjusting lever side tooth 18. When the adjusting lever 12 rotates in the adjusting direction to change the position of the adjusting lever side teeth 18 meshing with the stopper claw 23 and the wear of the lining 6 advances beyond the reference value, the shoe clearance b falls within a certain range. Adjust to keep. Although the stopper spring 24 urges the stopper claw 23 toward the meshing portion side of the adjust lever side teeth 18, the displacement of the stopper claw 23 is restricted by the lid portion 30 of the guard 22, so that at the time of adjustment. The engagement between the stopper claw 23 and the adjust lever side tooth 18 is released.

After the over-adjustment, the drum 1 contracts so that the drum 1 is engaged with the other brake shoe 3 through the pawl portion 1.
7 and push the adjusting lever 12 to the opposite direction D
Is applied to the stopper claw 23, the stopper claw 23 is resisted against the stopper spring 24.
Moves in a direction away from the adjust lever 12,
The engagement with the adjust lever side teeth 18 is released. Along with this, the adjusting lever 12 is pushed back in the anti-adjustment direction D, and the position of the other brake shoe 3 is returned to the original position where the adjustment was adjusted (over-adjustment is eliminated).

[0042]

According to the invention described in claim 1, when the drum is thermally expanded and then contracted, and the contracting force acts on the adjusting lever in the direction opposite to the adjuster direction, the guide gear rotates in the same direction. Since the adjustment lever is rotated in the direction opposite to the adjuster direction, the position of the brake shoe can be returned to the original position where the clearance is automatically adjusted.

According to the second aspect of the present invention, the guide gear and the stopper pawl each have a meshing portion formed when the anti-adjusting direction is rotated, so that the guide gear applies a force in the anti-adjusting direction via the adjusting lever. When received, the component force in the counter-biasing direction of the spring acts on the stopper claw to release the engagement between the stopper claw and the guide gear, so that the adjust lever rotates in the counter-adjustment direction,
The position of the brake shoe can be easily returned to the original position where the clearance is automatically adjusted.

According to a third aspect of the present invention, the guide gear is rotatable when the drum thermally expands and then contracts, and when the contraction force acts on the adjusting lever in the direction opposite to the adjuster direction. Since the guide gear rotates while being displaced along the guide gear elongated hole against the spring force of the shaft spring and the guide gear spring, the adjusting lever rotates in the anti-adjusting direction and the position of the brake shoe. Can be returned to the original position where the clearance is automatically adjusted.

According to a fourth aspect of the present invention, the one-way stopper allows the drum to rotate in the same direction when the drum is thermally expanded and then contracted, and the contraction causes a rotational force in the direction opposite to the adjuster to act on the adjust lever. As a result, the adjusting lever is rotated in the anti-adjusting direction without being restrained by the one-way stopper, so that the position of the brake shoe can be returned to the original position where the clearance is automatically adjusted.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a first embodiment of the present invention.

FIG. 2 is a diagram schematically showing a meshing state of an adjust lever, a guide gear and a one-way stopper of the first embodiment.

FIG. 3 is a diagram schematically showing the one-way stopper.

FIG. 4 is a diagram showing an operation of the first embodiment.

FIG. 5 is a diagram schematically showing a meshing state of the guide gear and the one-way stopper of the first embodiment.

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

FIG. 7 is a diagram showing a meshing state of an adjusting lever and a guide gear according to the second embodiment.

FIG. 8 is a diagram showing an operation of the second embodiment.

FIG. 9 is a sectional view showing a third embodiment of the present invention.

FIG. 10 is a diagram schematically showing a one-way stopper according to the third embodiment.

FIG. 11 is a diagram showing an operation of the third embodiment.

FIG. 12 is a front sectional view showing an example of a conventional automatic gap adjusting device for a drum brake.

FIG. 13 is a front view showing an auto-adjuster mechanism of the same device.

FIG. 14 is a bottom view showing the auto adjuster mechanism.

FIG. 15 is a plan view showing the auto adjuster mechanism.

FIG. 16 is a diagram showing a state before the brake operation of the device.

FIG. 17 is a diagram showing a state of the device when a brake is operated.

FIG. 18 is a view showing a state before the brake operation of the device when the lining is worn over a reference value.

FIG. 19 is a diagram showing a state when the lining is worn by a reference value or more when the brake is operated by the device.

FIG. 20 is a diagram showing a state after a brake operation of the device when the lining is worn over a reference value.

[Explanation of symbols]

 1 Drum 2 One brake shoe 3 The other brake shoe 6 Lining 8 Auto adjusting mechanism 9 Plate 10 Shaft 11 Shaft spring 12 Adjust lever 13 Guide gear 14 Plate long hole 15 Web 16 Web long hole 17 Claw 18 Adjust lever side teeth 21 One-way stopper

Claims (4)

[Claims] 1. A pair of brake shoes are provided so as to face each other on an inner circumference of a drum, and an auto-adjuster mechanism that operates by abrasion of a lining attached to the brake shoes is interposed between the pair of brake shoes. In an automatic device for adjusting the clearance of a drum brake in which the clearance between the lining and the drum is kept within a certain range by an auto adjuster mechanism, the auto adjuster mechanism is configured such that the base end is brought into contact with one brake shoe and the tip end side is adjusted to the other end. A plate which is arranged to extend to the brake shoe and has a plate elongated hole extending in the longitudinal direction at the tip end side thereof, a shaft which is inserted into the plate elongated hole, and a shaft which urges the shaft toward one brake shoe side. Spring, a web elongated hole formed in the web of the other brake shoe along the forming direction of the plate elongated hole, and the web length. An adjusting lever having a claw portion to be inserted into the hole and attached to the shaft, a guide gear rotatably provided on the plate and meshing with adjusting lever side teeth formed on the adjusting lever, and an engaging guide gear. A device for automatically adjusting the clearance of a drum brake, which comprises a one-way stopper that prevents the guide gear from rotating in the adjusting direction and allows rotation in the anti-adjusting direction. 2. The one-way stopper has a stopper claw that is biased by a spring and engages with the guide gear. When the guide gear and the stopper claw are engaged with each other, the meshing portions of the guide gear and the stopper claw during rotation in the adjusting direction are flat, and when rotating in the anti-adjusting direction. 2. The automatic clearance adjusting device for a drum brake according to claim 1, wherein the meshing portions of each are formed into curved surfaces. 3. A pair of brake shoes are provided on the inner periphery of the drum so as to face each other, and an auto-adjuster mechanism that operates by wear of a lining attached to the brake shoes is interposed between the pair of brake shoes, and In an automatic device for adjusting the clearance of a drum brake in which the clearance between the lining and the drum is kept within a certain range by an auto adjuster mechanism, the auto adjuster mechanism is configured such that the base end is brought into contact with one brake shoe and the tip end side is adjusted to the other A plate which is arranged to extend to the brake shoe and has a plate elongated hole extending in the longitudinal direction at the tip end side thereof, a shaft which is inserted into the plate elongated hole, and a shaft which urges the shaft toward one brake shoe side. Spring, a web elongated hole formed in the web of the other brake shoe along the forming direction of the plate elongated hole, and the web length. An elongated hole for a guide gear formed by engaging an adjusting lever having a claw portion to be inserted into the hole and attached to the shaft, and adjusting lever side teeth formed on the adjusting lever, and extending to the engaging portion side in the plate. An automatic gap adjusting device for a drum brake, comprising: a guide gear into which a shaft portion is inserted; and a guide gear spring that urges the guide gear toward the meshing portion side of the adjusting lever side teeth. 4. A pair of brake shoes are provided on the inner periphery of the drum so as to face each other, and an auto-adjuster mechanism that operates by abrasion of a lining attached to the brake shoes is interposed between the pair of brake shoes, and In an automatic device for adjusting the clearance of a drum brake in which the clearance between the lining and the drum is kept within a certain range by an auto adjuster mechanism, the auto adjuster mechanism is configured such that the base end is brought into contact with one brake shoe and the tip end side is adjusted to the other end. A plate which is arranged to extend to the brake shoe and has a plate elongated hole extending in the longitudinal direction at the tip end side thereof, a shaft which is inserted into the plate elongated hole, and a shaft which urges the shaft toward one brake shoe side. Spring, a web elongated hole formed in the web of the other brake shoe along the forming direction of the plate elongated hole, and the web length. Rotate the adjust lever that has a claw that is inserted into the hole and that is attached to the shaft, and the adjust lever side teeth that are formed on the adjust lever to prevent the adjust lever from rotating in the adjust direction and rotate in the anti-adjust direction. A device for automatically adjusting the clearance of a drum brake, which comprises a one-way stopper that allows