JPH0716040U - Drum brake with automatic shoe clearance adjustment - Google Patents

Abstract

(57) [Summary] [Purpose] To provide a drum brake in which an automatic shoe clearance adjusting mechanism reliably operates even when a wheel cylinder is operating. The strut 34 includes a first support member 38 that engages with the shoe web 20 and the parking lever 32 of the brake shoe 12, a second support member 40 that engages with the shoe web 20 of the brake shoe 14, and a first support member. Member 3
8 and the second support member 40, and an adjusting bolt 42, and a wavy leaf spring 46 fitted in one end 44 of the adjusting bolt 42 in a preloaded state at a position between the adjusting bolt 42 and the first supporting member. It is configured. The adjusting bolt 42 is provided with a star wheel 36 at an intermediate portion, is fitted into the fitting hole 48 of the first supporting member 38 at the one end portion 44 so as to be relatively rotatable, and has a predetermined play, and the other end portion 50 is provided with the second supporting member. It is screwed into the screw hole 52 of the member 40.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a drum brake having an automatic shoe clearance adjusting mechanism.

[0002]

[Prior art]

 A pair of brake shoes, each having a plate-shaped shoe web, are provided on the backing plate so as to be able to expand each other, a wheel cylinder for mutually expanding the pair of brake shoes, and a star wheel at an intermediate portion. The adjusting bolt is fitted into the first supporting member at one end and is screwed into the second supporting member at the other end, and is bridged between the pair of brake shoes to provide the first supporting member and the second supporting member. Both brake shoes are supported from the inside by a support member, and a strut that extends with the rotation of the star wheel and one shoe web of the brake shoe are attached to one surface of the brake web so as to be rotatable about an axis, and to be parked. A par that pushes one end of the strut toward the other end when it is rotated by an operating force. Ring lever and a claw portion that engages with the outer peripheral teeth of the star wheel. On the side opposite to the shoe web side of the parking lever, it is possible to rotate about the same axis as the rotation axis of the parking lever. An adjusting member that is attached to the shoe web and that is rotated with the rotation of the parking lever, and the claw portion of the adjusting member passes over the outer peripheral teeth of the star wheel and returns the adjusting member. There is known a drum brake provided with a shoe clearance automatic adjusting mechanism of a type in which a star wheel thereof is rotated in a direction in which the strut is extended during movement. The above-mentioned adjusting bolt is normally pressed by the first supporting member by transmitting the biasing force of the return spring for returning the pair of expanded brake shoes through the shoe web, and thereby the predetermined rotation resistance is exerted. When it is necessary to adjust the shoe clearance, the adjusting member is rotated along with the rotation of the parking lever by the parking operation, and the claw portion of the adjusting member causes the outer periphery of the star wheel to rotate. The strut is extended by rotating the star wheel by the pawl when the adjusting member returns and turns over the teeth.

[0003]

[Issues to be solved by the device]

 By the way, the parking operation is often performed in a state where the main brake is operated and the wheel cylinders are operating. Especially, in an automatic vehicle, such an operation is further performed in order to prevent a creep phenomenon. More opportunities. However, when the wheel cylinder is operating as described above, the pair of brake shoes are expanded against the biasing force of the return spring. Due to the gap, the biasing force of the return spring is not transmitted to the first support member and the second support member, and the rotation resistance of the thrust bolt is not given from the return spring. Therefore, the adjusting bolt and the claws of the adjusting member do not rotate together when the adjusting member rotates, and the claws of the adjusting member do not ride over the outer peripheral teeth of the star wheel, and the wheel cylinder is operating. In this state, there was a problem that the automatic shoe clearance adjustment mechanism would not work.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a drum brake in which an automatic shoe clearance adjusting mechanism reliably operates even when a wheel cylinder is operating. is there.

[0005]

[Means for Solving the Problems]

 In order to achieve such an object, the gist of the present invention is a drum brake provided with the shoe clearance automatic adjusting mechanism as described above, wherein the drum brake is provided between the first supporting member and the adjusting bolt. Even if the pair of brake shoes are expanded, an elastic pressing member that presses the adjusting bolt to provide a rotational resistance is provided.

[0006]

[Effect of action and device]

 With this arrangement, the elastic pressing member always applies rotational resistance to the adjusting bolt, even though the pair of brake shoes are expanded, so that the wheel cylinder operates to urge the return spring. Is prevented from being transmitted to the first support member and the second support member and the rotation resistance of the adjusting bolt is not given from the return spring, the co-rotation between the adjusting member claw and the adjusting bolt is prevented. . Therefore, even when the wheel cylinder is operating, the shoe gap automatic adjustment mechanism operates reliably as needed to maintain an appropriate shoe gap.

[0007]

【Example】

 An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, a pair of arcuate brake shoes 12 and 14 are provided on a backing plate 10 so as to be able to expand each other by shoe hold down devices 16 and 18. The brake shoes 12, 14 are fixed to the outer peripheral surface of the shoe rim 22, the shoe web 20 positioned substantially parallel to the plate surface of the backing plate 10, the shoe rim 22 fixed to the outer peripheral side end surface of the shoe web 20, and the outer peripheral surface of the shoe rim 22. And a lining 24, respectively. One ends of the brake shoes 12 and 14 are engaged with both ends of a wheel cylinder 26 fixed on the backing plate 10, respectively, and in the vicinity of the wheel cylinder 26 and inside the backing plate 10. At the position on the circumferential side, the return springs 28 spanned between the brake shoes 12 and 14 are urged toward each other, and the other ends of the brake shoes 12 and 14 are fixed on the backing plate 10. The anchors 30 are brought into contact with each other.

A parking lever 32 is provided on a surface of the one brake shoe 12 on the backing plate 10 side of the shoe web 20 so as to be rotatable about a single axis at a portion located on the wheel cylinder 26 side. Struts 34 are bridged between the shoe web 20 and the parking lever 32 of the brake shoe 12 and the shoe web 20 of the brake shoe 14, and the brake shoes 12 and 14 are supported from the inside by the strut 34. . The strut 34 has a star wheel 36 at an intermediate portion in the longitudinal direction thereof, and is configured to be extended as the star wheel 36 rotates in one direction.

The strut 34 described above, as shown in detail in FIG. 2, engages with the first support member 38 that engages the shoe web 20 of the brake shoe 12 and the parking lever 32, and the shoe web 20 of the brake shoe 14. The second supporting member 40, the adjusting bolt 42 connecting the first supporting member 38 and the second supporting member 40, and one end 44 of the adjusting bolt 42 at a position between the adjusting bolt 42 and the first supporting member. And a corrugated leaf spring 46 fitted in. The adjust bolt 42 includes the star wheel 36 at an intermediate portion, and is fitted into the fitting hole 48 of the first support member 38 at the one end portion 44 so as to be relatively rotatable with a predetermined play. It is screwed into the screw hole 52 of the second supporting member 40 at the other end portion 50 on the opposite side with 36 in between. Therefore, in a state where the brake shoes 12 and 14 are not expanded by the wheel cylinder 26, the biasing force of the return spring 28 is transmitted to the first support member and the second support member by the pair of shoe webs 20, and the first support member and the second support member are transmitted. The support member 38 is pressed by the adjusting bolt 42, and a predetermined rotation resistance is given to the adjusting bolt 42. Further, a right-hand thread is formed on the other end portion 50, and by being rotated in the direction of the arrow in FIG. 3, the strut 34 is extended out of the second support member 40.

The corrugated leaf spring 46 is, for example, formed by pressing a carbon steel strip for a spring, and as shown in detail in FIG. 4, an annular concave portion 54, a convex portion 56, and a fitting hole 5 are formed. 8 is formed into a disc shape and is fitted into the one end portion 44 of the adjusting bolt 42 in the fitting hole 58. The convex portion 56 is formed so as to axially protrude by a predetermined dimension A from one surface of the central portion of the wavy leaf spring 46 in which the fitting hole 58 is formed, and the strut 34 is attached in the mounted state in FIGS. 1 and 2. When the urging force of the return spring 28 is transmitted to, the first support member 38 and the star wheel 36 are pressed into a preloaded state, and the right end surface of the convex portion 56 in FIG. 4 (b) is wavy. It is located substantially on the same plane as the right end surface of the central portion of the leaf spring 46. It should be noted that the diameter of the fitting hole 58 is such that a slight gap is generated when the fitting hole 58 is fitted into the one end portion 44, and the diameter is substantially equal to or larger than the inner diameter of the fitting hole 48 and the first supporting member 38. The outer diameter of the open end of the star wheel 36 is smaller than the outer diameter of the star wheel 36, so that the pressing state is generated as described above. Further, the recess 54 has a diameter larger than the outer diameter of the opening end of the first support member 38, so that the elastic deformation range is increased.

On the shoe web 20 of the brake shoe 12, an adjusting member 60 is rotatable about the same axis as the rotation center of the parking lever 32 at a portion of the parking lever 32 located on the side opposite to the shoe web 20 side. It is provided in. The adjusting member 60 has a substantially L shape, and a claw portion 62 formed on one end side thereof is engaged with an outer peripheral tooth 64 of the star wheel 36 and an engaging hole formed in an intermediate portion. A protrusion 68 formed at one end of the first support member 38 is fitted in the member 66 with a predetermined play. A spring 70 is stretched between the portion of the adjusting member 60 located on the other end side and the brake shoe 12 in a slightly offset state. As a result, the adjusting member 60 is rotated clockwise in FIG. Direction and the direction of engagement with the outer peripheral teeth 64 of the star wheel 36 (that is, the upward direction in FIG. 3). At this time, the contact between the engagement hole 66 and the projection 68 of the first support member 38 on the right side surface of the projection 68 in FIG. 2 causes a gap between the inner peripheral side surface of the parking lever 32 and the adjustment member 60. A slight gap is maintained, and the first support member 38 is also pressed by the spring 70 in the leftward direction in FIG. 1, that is, in the direction of the shoe web 20 of the brake shoe 12. In FIG. 1, a parking cable 72 is connected to one end of the parking lever 32 and its position is fixed by holding portions 74, 76, 78 formed on the anchor 30.

In the drum brake having the automatic shoe clearance adjusting mechanism configured as described above, when the parking cable 72 is pulled in and the parking lever 32 is rotated counterclockwise in FIG. When the strut 34 is moved to the right in the figure, the brake shoe 14 is pushed out to the outer peripheral side, is pressed against the inner peripheral surface of the rotating drum 80, and the brake shoe 12 is rotated via the rotating shaft of the parking lever 32. When the strut 34 is pushed to the outer peripheral side and pressed against the rotating drum 80, the adjusting member 60 is also rotated counterclockwise in the figure together with the parking lever 32 via the protrusion 68 of the strut 34 as the strut 34 moves to the right. Be moved. Then, the lining 24 of the brake shoes 12, 14 wears to increase the gap (shoe gap) between the brake shoes 12, 14 and the rotating drum 80, and the amount of rotation of the adjusting member 60 is fixed to a predetermined value. When the value of is exceeded, the claw portion 62 of the adjusting member 60 rides over one outer peripheral tooth 64 of the star wheel 36, and then, when the adjusting member 60 is turned back when the parking brake is released, the adjusting member 60 is rotated. The claws 62 rotate the star wheel 36 in the one direction to extend the struts 34, so that the shoe gap increased due to wear of the brake shoes 12 and 14 is automatically adjusted.

The above-described operation has been described with respect to the case where the parking operation is performed in a state where the brake shoes 12 and 14 are not expanded by the wheel cylinder 26, but in the drum brake including the wheel cylinder 26, The parking operation may be performed while the main brake is operated and the rotation of the rotary drum 80 is stopped by the operation of the wheel cylinder 26. Especially in automatic vehicles, there is a greater chance that such an operation will be performed in order to prevent the creep phenomenon. The case where the parking operation is performed while the wheel cylinder 26 is operating will be described below.

When the main brake is operated, the wheel cylinders 26 push the brake shoes 12 and 14 in a direction in which they are separated from each other, that is, toward the outer peripheral side, and are pressed against the rotary drum 80. Since it spreads, the biasing force of the return spring 28 is not transmitted to the strut 34. At this time, since the parking lever 32 and the adjusting member 60 are attached to the shoe web 20 so that the one end side of the shoe web 20 of the brake shoe 12 is the rotation center, the parking lever 32 and the adjusting member 60 are not moved to the outer peripheral side of the brake shoe 12. Along with the movement, the first support member 38 is moved toward the outer peripheral side, and is pressed against the shoe web 20 of the brake shoe 12 based on the engagement between the engagement hole 66 of the adjustment member 60 and the protrusion 68. , Can be moved together. On the other hand, since the second support member 40 is in the non-pressed state, the first support member 38 is not pressed by the adjustment bolt 42, and the corrugated leaf spring 46 presses the adjustment bolt 42 toward the second support member side according to the restoring force. As a result, the distance between the star wheel 36 and the open end of the first supporting member 38 is widened, and the second supporting member 40 is pressed against the shoe web 20. Therefore, the adjusting bolt 42 is given a predetermined rotation resistance, and the automatic shoe clearance adjusting mechanism works reliably. The protruding dimension A of the convex portion 56 of the wavy leaf spring 46 is a size by which the second support member 40 is reliably pressed against the shoe web 20 during the above-described operation, that is, the shoe web 20 of the brake shoe 14 by the main braking operation. It is set to be sufficiently larger than the gap between the second support member 40 and the second support member 40.

The corrugated leaf spring 46 is provided between the first support member 38 and the adjustment bolt 42, the relative position of which does not change when the strut 34 is extended based on the operation of the shoe gap automatic adjustment mechanism. Therefore, the wavy leaf spring 46 is maintained in the same pre-loaded state even after the shoe clearance is adjusted, and the automatic shoe clearance adjustment mechanism operates reliably.

On the other hand, in the conventional strut in which the wavy leaf spring 46 is not used, the second support member 40 is not pressed by the shoe web 20 during the operation of the wheel cylinder 26 as described above, and thus the adjustment bolt 42 Rotational resistance is no longer applied to. When the parking operation is performed in such a state, the parking cable 72 is pulled in, and the parking lever 32 is rotated counterclockwise in FIG. 1, the strut 34 moves rightward. Until the second support member 40 abuts on the shoe web 20 on the side of the brake shoe 14, the adjustment bolt 42 is maintained in the non-pressed state and does not provide sufficient rotation resistance, so that the parking lever 32 cannot rotate. Accordingly, when the adjusting member 60 rotates, the star wheel 36 rotates together, and the automatic shoe clearance adjusting mechanism does not work.

Further, in the present embodiment, the corrugated leaf spring 46 which can be easily manufactured by the press working is used, and the one end portion 44 of the adjust bolt 42 is fitted into the first support member 38 in the assembling process of the strut 34. Since only a simple operation of fitting the corrugated leaf spring 46 into the one end portion 44 is required, the automatic automatic clearance adjustment mechanism can be reliably operated at a very low cost.

The shape of the elastic pressing member is not limited to the corrugated leaf spring 46 shown in FIG. 4, and may be a corrugated leaf spring 82 with legs shown in FIG. The corrugated leaf spring 82 with legs is provided with a plurality of leg portions 86 which are cut in the radial direction of the disc having the fitting holes 84, and each leg portion 86 is shown in FIG. 5 (b). As shown in the cross section, a concave portion 88 similar to the concave portion 54 of the wavy leaf spring 46 is provided, and the outer peripheral edge portion 90 has the same function as the convex portion 56. That is, the diameter of the outer peripheral edge portion 90 and the axially protruding dimension A from the one surface of the central portion of the wavy leaf spring with leg 82 in which the fitting hole 84 is formed are the same as those of the wavy leaf spring 46 described above. The inner diameter of the fitting hole 84 and the diameter of the recess 88 are set in the same manner so that the star wheel 36 is pressed. In the wavy leaf spring with leg 82, the leg portion 86 that biases the adjust bolt 42 is not constrained in the circumferential direction, and therefore has a relatively linear elastic characteristic in the elastic deformation range. . As shown in FIG. 5 (c), the leg portion 86 has the burrs at the tip of the outer peripheral edge portion 90 formed during molding removed by processing the tip into an R shape, resulting in a wavy shape with a leg. The leaf spring 82 can press the star wheel 36 substantially uniformly over the entire circumference thereof. Further, in the leg portion 86, the outer peripheral edge portion 90 is bent toward the concave portion 88 side instead of forming the above-mentioned tip portion into the R shape, and a convex portion similar to the convex portion 56 of the wavy leaf spring 46 is formed. Even if the star wheel 36 is configured to be pressed by the convex portion, the influence of the burr can be avoided.

Although one embodiment of the present invention has been described in detail above, the present invention can be implemented in still another mode.

For example, in the above-mentioned embodiment, an example in which the present invention is applied to a so-called LT type drum brake has been shown, but the present invention has an automatic shoe clearance adjusting mechanism similar to that of the above-mentioned embodiment. If applicable, it can be applied to other types of drum brakes, such as two-leading type drum brakes and duo-servo type drum brakes.

Further, in the above-described embodiment, the wavy leaf spring 46 is fitted in the one end portion 44 with a slight gap, but it is fitted in the open end side end portion of the first support member 38. It may be fixed by a method such as fixing. When such a fixing method is adopted, it is necessary to securely fix the wavy plate spring 46 so as not to be displaced due to the biasing force thereof.

Further, the mounting direction of the parking lever 32 and the adjusting member 60 is not limited to between the shoe web 20 and the backing plate 10, but is mounted on the surface of the shoe web 20 opposite to the backing plate 10. May be.

Although not illustrated one by one, the present invention can be variously modified without departing from the gist thereof.

[Brief description of drawings]

FIG. 1 is a view showing a main part of a drum brake including an automatic shoe clearance adjusting mechanism according to an embodiment of the present invention.

FIG. 2 is a view showing a main part of a shoe clearance automatic adjusting mechanism in a II-II section in FIG.

FIG. 3 is a cross-sectional view taken along the line III-III in FIG. 2, showing the positional relationship between the star wheel and the adjusting member.

4A and 4B are views showing an elastic pressing member applied to the shoe clearance automatic adjusting mechanism of FIG. 2, in which FIG. 4A is a plan view and FIG.
It is a figure which shows the bb cross section in (a) figure.

FIG. 5 is a view showing another example of the elastic pressing member applied to the shoe gap automatic adjusting mechanism of FIG. 2, which is (a) and (b).
4A and 4B are views corresponding to FIGS. 4A and 4B, and FIG. 4C is a view of the leg viewed from the direction c in FIG. 4A.

[Explanation of symbols]

 12, 14: Brake shoe 20: Shoe web 32: Parking lever 34: Strut 36: Star wheel 38: First support member 40: Second support member 42: Adjust bolt 44: One end portion (of the adjust bolt 42) 46: Wavy Leaf spring (elastic pressing member) 48: Fitting hole 50: Other end portion (of adjusting bolt 42) 52: Screw hole

Claims (1)

[Scope of utility model registration request] 1. A pair of brake shoes each having a plate-shaped shoe web and provided on a backing plate so as to be mutually expandable, a wheel cylinder for mutually expanding the pair of brake shoes, and an intermediate portion. A star wheel is provided to fit between the first support member at one end and the adjustment bolt is screwed to the second support member at the other end and is bridged between the pair of brake shoes. A strut that supports both brake shoes from the inside by a support member and a second support member and that extends along with the rotation of the star wheel, and one of the shoe webs of the brake shoe that is rotatable about one axis When installed, the parking lever pushes out one end of the strut toward the other end when rotated by the parking operation force. A bar and a claw portion that engages with the outer peripheral teeth of the star wheel, and is rotatable about the same axis as the rotation axis of the parking lever on the side opposite to the shoe web side of the parking lever. An adjusting member that is attached to the shoe web and that is rotated in accordance with the rotation of the parking lever, and a claw portion of the adjusting member rides over outer peripheral teeth of the star wheel and is rotated when the adjusting member returns and rotates. A drum brake including a shoe gap automatic adjusting mechanism of rotating the star wheel in a direction of extending the strut, wherein the pair of brake shoes are expanded between the first supporting member and the adjusting bolt. The shoe clearance automatic adjustment is characterized in that it is provided with an elastic pressing member that presses the adjusting bolt to provide a rotational resistance regardless of the opened state. Drum brake with mechanism