JPH0214672Y2 - - Google Patents

Description

[Detailed Description of the Invention] Technical Field The present invention relates to improvements in an automatic shoe operating gap adjustment device used to automatically adjust the gap between the brake shoe and the rotating drum of a drum brake (shoe operating gap). It is something.

Prior Art In drum brakes, braking is generally performed by a brake shoe that is provided so as to be reciprocally movable and is pushed outward by a piston of a wheel cylinder and pressed against the inner circumferential surface of a rotating drum. As the brake shoe wears, the distance between the brake shoe and the rotating drum increases. Therefore, an automatic shoe operation distance adjustment device is provided to automatically adjust the shoe operation distance. is being established. During this shoe operation, a type of automatic adjustment device includes a movable member that moves together with the brake shoe, and a rotatable member that is rotatably provided on the outer circumferential surface of the wheel cylinder and is allowed to rotate in only one direction. an adjustment member that is rotated in one direction by a member and that regulates the return side position of the moving member, the moving amount of the moving member that moves together with the brake shoe in the pressing direction of the piston is predetermined. When a certain amount is exceeded, there is a type that automatically adjusts the shu operation interval by changing the return side position of the movable member in the direction of decreasing the shu operation interval using the adjustment member. For example, this is described in Japanese Utility Model Application Publication No. 107643/1983, which was previously filed and published by the present applicant.

In this shoe operation gap automatic adjustment device, when brake fluid pressure is supplied to the wheel cylinder, the moving member is moved in the pressing direction together with the brake shoe as the piston protrudes, causing the outer peripheral surface of the brake shoe to rotate. The moving member is prevented from moving in the pressing direction almost at the same time as it comes into contact with the inner circumferential surface of the drum.

Problems to be Solved by the Invention However, when a relatively excessive brake fluid pressure is applied to the wheel cylinder, the brake shoe and rotating drum are stiffer than the piston due to the stiffness of the brake shoe and rotating drum. The movable member may be elastically deformed due to an excessive pressing force, and the movable member may be further moved in the pressing direction. In such a case, the return side position of the movable member may be changed in the direction of decreasing the shu operation gap even though the shu operation gap does not exceed a predetermined amount. There was a problem that proper adjustment was impaired.

Means for Solving the Problems The present invention has been made against the background of the above-mentioned circumstances, and its gist is to provide an automatic shoe operation gap adjustment device as described above, in which the piston is pushed. A pressing force transmission path from the piston of the wheel cylinder to the brake shoe is provided with an elastic member that suppresses movement of the moving member by elastically deforming when the pressure exceeds a predetermined constant value. be.

Operation and Effect of the Invention With this structure, the elastic member that suppresses the movement of the movable member by elastically deforming when the pressing force of the piston exceeds a predetermined value is the piston of the wheel cylinder. Since the pressure transmission path from the piston to the brake shoe is provided, even if a relatively excessive piston pressure is applied to the brake shoe and the rotating drum, the pressure remains at a predetermined constant level. The elastic member is elastically deformed and the brake shoe and rotating drum are prevented from being elastically deformed when the value of Subsequent movement of the movable member in the pressing direction is suppressed, and the return side position of the movable member is prevented from being unnecessarily changed in the decreasing direction during the shoe operation. As a result, the adjustment member provided on the outer peripheral surface of the wheel cylinder is rotated in one direction by the movable member that moves together with the brake shoe when the wheel cylinder is operated, so that the return side position of the movable member is changed between the shoe operation. Shutdown time is automatically adjusted by changing to a decreasing direction.
In the automatic adjustment device, the shift interval is always properly adjusted to prevent over-adjustment.

Embodiment Hereinafter, an embodiment of the present invention will be described in detail based on the drawings.

FIG. 10 is a diagram showing the main parts of a two-leading type drum brake to which the present invention is applied.
8 so that it can be expanded. Both ends of the brake shoes 12 and 14 are connected to a pair of wheel cylinders 2 fixed on the bucking plate 10.
0 and 22, respectively. The brake shoes 12 and 14 are spread apart by the wheel cylinders 20 and 22, and their outer peripheral surfaces are pressed against the inner peripheral surface of the rotating rotating drum 23, so that rotation of the rotating drum 23 is suppressed. It's getting old. Also, a pair of return springs 2 are provided between the brake seats 12 and 14 to constantly bias them toward each other.
4 and 26 are stretched. Note that since the wheel cylinders 20 and 22 are configured in the same way, the following explanation will be given only for the wheel cylinder 20.

As shown in FIGS. 1 and 2, the wheel cylinder 20 includes a cylinder body 28 and a piston 30.
and a mounting portion 3 of the cylinder body 28.
2, it is fixed to the backing plate 10. One end of one brake shoe 12 is engaged with one end of the cylinder body 28 . A cylinder bore 34 is formed inside the cylinder body 28 and opens toward the other end of the cylinder body 28.
A piston 30 is fitted to the cylinder body 4 so as to be slidable in the axial direction of the cylinder body 28. piston 3
0 consists of a piston main body 36 and an engaging member 40 that is slidably fitted into a fitting hole 38 of the piston main body 36. The engaging member 40 has a shaft portion 42 and a head portion 4 in which a groove 44 is formed.
6, and one end of the other brake shoe 14 is engaged with the groove 44. and,
When brake fluid pressure is supplied to the fluid chamber 48 of the cylinder body 28, the piston 30 is pushed out to the right in the figure, and the brake shaft 1
4 is pressed against the rotating drum 23 with a predetermined pressing force.

The cylinder body 28 is formed with protrusions 50 and 52 that protrude radially outward from a portion of its outer periphery. A latching member 56 having a plurality of latching teeth 54 on the outer periphery of the protrusion 50 is fixed by a pin 58 so as not to rotate about the pin 58 . on the other hand,
An adjustment member 60 is rotatably attached to the protrusion 52 by a pin 62. The adjusting member 60 includes a fan-shaped engaging portion 64 and an acting portion 66, and the peripheral edge of the engaging portion 64 extends approximately along an arc centered on the pin 62, more precisely, downward in FIG. It is formed in a curved shape whose radius of curvature increases as it advances. A plurality of engagement teeth 68 are formed on the peripheral edge. Further, a pin 70 is fixed to the engaging portion 64 of the adjusting member 60 at the end opposite to the engaging tooth 68 with the pin 62 in between, and the pin 70 is stretched between the pin 58 and the pin 70. The engaging tooth 68 is normally engaged with the latch tooth 54 by the biasing force of the spring 72 . The acting portion 66 is formed in a state extending from the pin 70 side of the engaging portion 64 in a direction substantially perpendicular to the engaging portion 64 in the same plane as the engaging portion 64, and the acting portion 66 extends from the pin 70 side of the engaging portion 64 in a direction substantially perpendicular to the engaging portion 64. It is fitted into an engagement hole 88 formed in the arm portion 82 of the mating plate 78. The acting portion 66 has both side surfaces substantially opposite to both wall surfaces of the engagement hole 88 in a direction parallel to the axis of the piston 30 (both wall surfaces in the left-right direction in FIG. 2) formed into a curved shape, and the adjusting member 60 When the engaging hole 88 is rotated, the total gap between both wall surfaces of the engagement hole 88 and both side surfaces of the acting portion 66 facing these two wall surfaces is kept unchanged. In addition,
An elongated hole 74 is formed in the adjustment member 60 in a direction substantially parallel to the axis of the piston 30.
The pin 62 is fitted inside with a predetermined play. Reference numeral 76 denotes a rotation stopper for preventing the adjustment member 60 from rotating beyond a certain amount.

An engagement plate 78 that constitutes a moving member is attached to the piston 30. The engagement plate 78 includes a disk-shaped attachment portion 80 and an arm that protrudes in the radial direction from a part of the outer peripheral edge of the attachment portion 80 and whose tip portion extends in a direction substantially parallel to the axis of the attachment portion 80. 82. The engagement plate 78 is fitted into the shaft portion 42 of the engagement member 40 in a hole 84 formed in the attachment portion 80, and is sandwiched between the head portion 46 of the engagement member 40 and the piston body 30. installed in condition. A protrusion 86 is formed on the peripheral edge of the hole 84 of the attachment part 80, and the protrusion 86 protrudes toward the piston body 36 when the attachment part 80 is attached.
An engagement hole 88 is formed at the tip of the arm portion 82 . In this embodiment, the protrusion 86 constitutes an elastic member, and the protrusion 86 is compressed with a predetermined pressing force by the urging force of the return springs 24 and 26.

In such an automatic drum brake shu operation gap adjustment device, when the brake is not activated, the lower limit value of the appropriate shu operation gap is set between the left side surface of the operating portion 66 in the figure and the left wall surface of the engagement hole 88 in the figure. A gap C is formed. During brake operation, if the brake shoe 14 is not worn out, the piston 30 is pushed out and the brake shoe 14 is pressed against the rotating drum 23, and the gap C disappears at approximately the same time; 14, the engagement plate 78 is further moved in the pressing direction after the gap C disappears,
The adjustment member 60 is rotated in the direction of decreasing the shoe operating gap (clockwise in FIG. 2). When the amount of movement of the engagement plate 78 in the pressing direction exceeds a predetermined amount, that is, when the shoe operation gap exceeds the upper limit of the appropriate range, the engagement teeth 68 of the adjustment member 60 are engaged. After passing over the latch teeth 54 of the member 56, the return side position of the engagement plate 78 is changed in the direction of decreasing the shoe operation gap. At this time, the adjustment member 60 is moved by the elongated hole 74 against the biasing force of the spring 72 in the direction of disengagement with the latch teeth 54 of the latch member 56, so that its rotation is permitted.

Next, in the drum brake equipped with the automatic shoe operation gap adjustment device as described above, the piston 3
The operation of the engagement plate 78 and the protrusion 86 corresponding to a pressing force of 0 will be explained based on FIGS. 3 to 5. In these figures, the arm portion 82 of the engagement plate 78 and the action portion 66 of the adjustment member 60 are shown approximately in the longitudinal direction of the arm portion 82 for convenience.
Shown rotated 90 degrees. When the brake is not activated, as shown in FIG. 3, the gap C is formed between the left side surface of the action portion 66 in the drawing and the left wall surface of the engagement hole 88 in the drawing. At this time, the pressing force applied to the protrusion 86 of the engagement plate 78 is only the biasing force of the return springs 24 and 26, and the protrusion 86 is hardly elastically deformed or is slightly elastically deformed. It is in a pre-compressed state.

When a relatively small pressing force of the piston 30 is applied to an extent that does not cause elastic deformation of the brake shoe 14 and the rotating drum 23 during normal brake operation, the piston 30 engages with the piston body 36 as shown in FIG. The plate 78 and the engaging member 40 are pushed out against the biasing forces of the return springs 24 and 26, and the brake shoe 14 is pressed against the rotating drum 23, and the gap C disappears, causing the left side surface of the acting portion 66 to The adjustment member 60 is brought into contact with the left wall surface of the engagement hole 88, and is rotated by a predetermined amount in the direction of decreasing the shoe gap in accordance with the amount of wear of the brake shoe 14. Even in this case, the protruding portion 86 hardly undergoes elastic deformation, and the piston body 36 is prevented from protruding almost at the same time as the brake shoe 14 comes into contact with the inner circumferential surface of the rotating drum 23.

Next, the brake shoe 14 and the rotating drum 2
When the pressing force of the piston 30 is excessively applied to the extent that almost the elastic deformation of 3 occurs, the shaft portion 42 of the engaging member 40 is pushed into the fitting hole 38, as shown in FIG.
The engagement plate 78
The protrusion 86 is elastically deformed in the axial direction of the piston 30. At this time, the amount of movement of the piston 30 due to the excessive pressing force is consumed by the elastic deformation of the protrusion 86, and after the brake shoe 14 comes into contact with the inner peripheral surface of the rotating drum 23, the brake shoe 14 , the rotating drum 23, the arm portion 82 of the engagement plate 78, etc. are almost completely prevented from being moved in the direction in which the piston 30 is pressed. Further, the elastic force of the protrusion 86 of the engagement plate 78 causes elastic deformation of the brake shoe 14 and the rotating drum 23 when the pressing force of the piston 30 exceeds a predetermined constant value, for example, as described above. The material and shape of the piston 30 are taken into consideration so that it can be elastically deformed when an excessive pressing force is applied to the piston 30 to the extent that almost 100% of the pressure is applied to the piston 30, and there is almost no elastic deformation when the brake is activated by the normal pressing force of the piston 30. Therefore, it has almost no effect on pedal stroke, etc.

As described above, according to the automatic shoe operation gap adjustment device of this embodiment, the protrusion suppresses the movement of the engagement plate 78 by elastically deforming when the pressing force of the piston 30 exceeds a predetermined constant value. Since the portion 86 is provided between the piston body 36 and the engaging member 40, even if the brake shoe 1
2 and 14 are pressed against the rotating drum 23 by the piston 30 with an excessive pressing force, when the pressing force exceeds a predetermined constant value, the protrusion 86 is elastically deformed and the brake shoe is 1
2, 14 and the rotating drum 23 are prevented from being elastically deformed, thereby preventing the engagement plate 78 from being pressed after the outer circumferential surface of the brake shoes 12, 14 comes into contact with the inner circumferential surface of the rotating drum 23. The movement in the direction is suppressed, and the return side position of the engagement plate 78 (moving member) is prevented from being unnecessarily changed in the direction of decrease during the shu operation. As a result, the adjustment member provided on the outer peripheral surface of the wheel cylinder is rotated in one direction by the movable member that moves together with the brake shoe when the wheel cylinder is operated, so that the return side position of the movable member is changed between the shoe operation. In an automatic shoe operation adjustment device of the type in which the shoe operation time is automatically adjusted by changing it in the decreasing direction, the shoe operation time is always properly adjusted to prevent over-adjustment.

In the above-described embodiment, the elastic member (protrusion 86) is formed integrally with the engagement plate 78 as a moving member, but it does not necessarily have to be configured in this way. For example, as shown in FIG. ,
The portion of the engagement plate 90 to be fitted with the engagement member 40 is formed into a flat plate shape, and a disc spring 9 is provided between the engagement plate 90 and the piston body 36.
An elastic member made of 2 or the like may be inserted.

Furthermore, in the above embodiment, the engagement plate 78
As shown in FIG. 7, an engagement plate 97 may be integrally formed from a separately molded disc-shaped mounting member 94 made of spring steel and an action member 96 made of steel.

In addition, when the elastic member and the movable member are configured as separate members, the elastic member made of a disc spring or the like is connected to the tip of the shaft portion 42 of the engagement member 40 and the fitting hole 38.
The movable member is inserted between the head 46 of the engaging member 40 or the bottom of the brake shoe 1.
Alternatively, the movable member may be fixed to the brake shoes 12, 14 and a predetermined elastic member may be fixed to the engaging member 40 and the brake shoes 12, 14.
It is also possible to insert it between 14 and 14. In short, the elastic member only needs to be provided in the pressing force transmission path from the piston body 36 to the brake shoes 12, 14.

In the above-described embodiment, in order to prevent the protrusion 86 from being deformed beyond its elastic limit due to excessive pressing force of the piston 30, the piston body 36 is deformed as shown in FIG. Fitting hole 3
A stopper made of a shim 98 or the like may be provided at the bottom of the engaging member 40, or a stopper made of a shim 100 or a predetermined protrusion may be provided at the base periphery of the shaft portion 42 of the engaging member 40, as shown in FIG. It's okay.

Further, in the above-mentioned embodiments, the case where the present invention is applied to a two-leading type drum brake has been described, but the present invention can also be applied to other types of drum brakes such as a uni-servo type drum brake.

In addition, various changes may be made to the present invention without departing from the spirit thereof.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway plan view of a wheel cylinder equipped with an automatic shoe operation gap adjustment device to which the present invention is applied. FIG. 2 is a front view of FIG. 1. FIGS. 3 to 5 are schematic diagrams for explaining the operation of the engagement plate 78 in response to the pressing force of the piston. FIGS. 6 to 9 are views showing other embodiments of the present invention, and correspond to FIG. 3. FIG. 10 is a front view showing the main parts of a drum brake equipped with an automatic shoe operation gap adjustment device to which the present invention is applied. 12, 14: Brake shoe, 20, 22: Wheel cylinder, 23: Rotating drum, 30: Piston, 60: Adjustment member, 78, 90, 97: Engagement plate (moving member), [86: Projection, 92 : Disc spring, 94: Mounting member] (elastic member).

Claims (1)

[Claims for Utility Model Registration] In a drum brake in which a reciprocally movable brake shoe is pressed against a rotating drum by a piston of a wheel cylinder, a movable member that moves together with the brake shoe and the outer periphery of the wheel cylinder an adjustment member rotatably provided on the surface to allow rotation in only one direction, rotated in the one direction by the movable member, and regulating the return side position of the movable member; When the amount of movement of the movable member that moves together with the brake shoe in the pressing direction of the piston exceeds a predetermined certain amount, the adjustment member changes the return side position of the movable member to a direction that decreases during the shoe operation. An automatic shoe operation adjustment device of the type that automatically adjusts the shoe operation time by An automatic adjustment device for a drum brake during shoe operation, characterized in that an elastic member for suppressing movement of the member is provided in a pressing force transmission path from the piston of the wheel cylinder to the brake shoe.