JP2008045724A - Drum brake equipped with shoe clearance automatic adjusting mechanism - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a drum brake equipped with a shoe clearance automatic adjusting mechanism reducing cost of a first strut member. <P>SOLUTION: (a) A fitting hole 60c is formed in the end face 60b on the first strut member 56 side of an adjusting shaft 60. (b) The first strut member 56 is provided with a shaft part 56a fitted in a relatively rotatable manner into the fitting hole 60c of the adjusting shaft 60. (c) The first strut member 56 is formed by press working. The fitting hole heretofore provided in the first strut member is formed in the adjusting shaft 60, and the first strut member 56 is formed in comparatively uniform plate thickness without needing a locally thickened part of plate thickness to provide the fitting hole. Forging and cutting heretofore required to form the first strut member can thereby be changed to press working comparatively low in the forming cost to reduce the forming cost of the first strut member 56. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a drum brake having an automatic shoe clearance adjustment mechanism, and more particularly to a technique for reducing the manufacturing cost of a drum brake by changing the structure of an automatic shoe clearance adjustment mechanism.

  As one type of drum brake shoe gap automatic adjustment mechanism, for example, as shown in Patent Document 1, (a) a first strut member that engages one of a pair of expandable brake shoes, and a pair of brake shoes A second strut member engaged with the other, and an adjustment shaft provided with an adjustment wheel and disposed between the first strut member and the second strut member and screwed into at least one strut member; A strut that defines a standby position of the pair of brake shoes during non-braking; and (b) an adjustment lever that rotates the adjustment wheel in one direction in accordance with the amount of expansion of the pair of brake shoes during braking. (C) When the adjusting wheel is rotated by the adjusting lever, the strut is extended and is not braked. It is intended to automatically adjust the shoe clearance between the rotating drum and the pair of brake shoes in.

In the conventional shoe gap automatic adjusting mechanism of the type described above, the first strut member and the adjusting shaft are connected to each other so as to be relatively rotatable. Is provided with a fitting hole for fitting in a relatively rotatable manner.
JP 2002-147506 A

  However, the first strut member has a complicated shape in which the plate thickness of the first strut member is locally increased in order to provide the fitting hole, and forging and cutting with a relatively high molding cost for the molding. Therefore, there is a problem that the first strut member, that is, the drum brake cannot be manufactured at a low cost.

  The present invention has been made against the background of the above circumstances, and an object of the present invention is to provide a drum brake having an automatic shoe clearance adjusting mechanism that reduces the molding cost of the first strut member. It is in.

  The gist of the invention according to claim 1 for achieving this object is as follows: (a) a first strut member that engages one of a pair of expandable brake shoes, and the other of the pair of brake shoes. A second strut member engaged with the first strut member, and an adjustment shaft disposed between the first strut member and the second strut member, the adjustment shaft being screwed to at least one of the strut members. A strut that defines the standby position of the pair of brake shoes during braking; and (b) an adjustment lever that rotates the adjustment wheel in one direction in accordance with the amount of expansion of the pair of brake shoes during braking. (C) When the adjusting wheel is rotated by the adjusting lever, the strut is extended, and the pair of brakes when not braked are In a drum brake having an automatic shoe gap adjusting mechanism for automatically adjusting a shoe gap between a kisshu and a rotating drum, (d) a fitting hole is formed in an end surface of the adjusting shaft on the first strut member side. (E) the first strut member is provided with a shaft portion that fits in the fitting hole of the adjustment shaft so as to be relatively rotatable, and (f) the first strut member is formed by press working. It is to be a thing.

  The gist of the invention according to claim 2 is that the shaft portion of the first strut member is integrally formed by press working.

  Further, the gist of the invention according to claim 3 is that the adjusting shaft is screwed with the second strut member at one end thereof and is relatively rotatable with the shaft portion of the first strut member at the other end. And the adjusting wheel is provided between one end and the other end.

  The gist of the invention according to claim 4 is that the second strut member is formed by press working.

  According to the drum brake having the shoe gap automatic adjusting mechanism according to the first aspect of the present invention, (a) a fitting hole is formed in the end surface of the adjusting shaft on the first strut member side, and (b) the first The strut member includes a shaft portion that fits in the fitting hole of the adjustment shaft so as to be relatively rotatable, and (c) the first strut member is formed by press working. Conventionally, the fitting hole provided in the first strut member is formed in the adjusting shaft, and the first strut member does not require a portion where the plate thickness is locally increased in order to provide the fitting hole. It is configured to have a relatively uniform plate thickness. Thereby, it is possible to change from forging and cutting, which have been conventionally required for forming the first strut member, to press processing having a relatively low forming cost, and the forming cost of the first strut member is reduced.

  According to the drum brake having the shoe gap automatic adjusting mechanism according to the second aspect of the present invention, the shaft portion of the first strut member is integrally formed by pressing, so the first strut member The number of parts can be reduced, and the molding cost of the first strut member can be further reduced.

  According to the drum brake having the shoe gap automatic adjusting mechanism according to the third aspect of the present invention, the adjusting shaft is screwed with the second strut member at one end and the first strut at the other end. Since it is fitted to the shaft portion of the member so as to be relatively rotatable and the adjustment wheel is provided between one end portion and the other end portion thereof, the adjustment wheel from the adjustment wheel to the shaft end on the other end side is provided. The distance can be set short.

  According to the drum brake having the shoe gap automatic adjusting mechanism of the invention according to claim 4, since the second strut member is formed by press working, the second strut member is forged and cut. Compared to molding from the above, the molding cost is lower and the manufacturing cost of the drum brake can be further reduced.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a leading / trailing type vehicle drum brake (hereinafter referred to as a drum brake) 10 which is a drum brake with a shoe clearance automatic adjustment mechanism having a parking lock function according to an embodiment of the present invention. It is a front view which removes and shows the drum (rotary drum) 12. FIG. Further, the brake drum 12 is represented by two concentric circles indicated by a one-dot chain line in FIG. 1, and the circle on the center side of the two circles indicates the inner peripheral surface 14 of the brake drum 12.

  The drum brake 10 has a substantially disc shape, and includes a backing plate 16 that is integrally fixed to a vehicle body side member such as an axle tube, an axle housing, and a suspension device (not shown), that is, a non-rotating member. .

  The drum brake 10 includes a pair of arc-shaped brake shoes 18 and 20 disposed substantially symmetrically so as to be able to approach and separate from each other in a posture in which the convex side is on the outer side of the backing plate 16, and the pair of brake shoes 18 and 20. A wheel cylinder 22 provided in a fixed position on the backing plate 16 between one end of the brake shoes 18 and 20, that is, the upper end of FIG. 1, and one end of the pair of brake shoes 18 and 20 are always attached in a direction approaching each other. In order to urge the wheel cylinder 22 into contact with the wheel cylinder 22, a coiled return spring 24 stretched between one end portions thereof and a pair of brake shoes 18 so as to be inserted through the inside of the coiled return spring 24, 20 between the pair of brake shoes 18 and 20 and the brake drum 12 when not braked. That is, a shoe gap automatic adjusting mechanism 26 that automatically adjusts the shoe gap, an anchor 28 provided in a fixed position between the other ends of the pair of brake shoes 18 and 20, that is, the lower ends of FIG. A spring 30 is provided between the lower ends of the brake shoes 18 and 20 so that the lower ends are always brought into contact with the anchor 28.

  Each of the pair of brake shoes 18 and 20 has a flat shape substantially parallel to the plate surface of the backing plate 16 and the shoe webs 32 and 34 that are curved in an arc shape in the front view shown in FIG. The belt-like shoe rims 36 and 38 are integrally fixed so that the cross-section is substantially T-shaped along the outer peripheral side edge of the circular arc shape, and an adhesive is attached to the outer peripheral surfaces of the shoe rims 36 and 38. And linings 40 and 42 made of a friction material fixed integrally with each other. The pair of brake shoes 18 and 20 are pressed against the backing plate 16 by being pressed toward the backing plate 16 by shoe hold-down devices 44 and 46 respectively disposed on the shoe web 32 and the shoe web 34. It is held so that it can move in the relative direction. A base end portion of a flat parking brake lever 48 is connected to one end portion of the brake shoe 18 by a pin 50 so as to be relatively rotatable. The backing plate 16, the shoe webs 32 and 34, and the shoe rims 36 and 38 are all pressed parts that are punched from a steel plate and subjected to predetermined bending.

  As shown in FIG. 1, the shoe gap automatic adjustment mechanism 26 is stretched between one end portions of a pair of brake shoes 18 and 20, and a strut 52 that defines a standby position of the pair of brake shoes 18 and 20 during non-braking. And an adjusting lever 54 provided in the strut 52.

  As shown in FIG. 2, the strut 52 includes a first strut member 56 that engages the shoe web 34, a second strut member 58 that engages the shoe web 32 and the parking brake lever 48, and an adjustment wheel 60a. The adjusting shaft 60 is disposed between the first strut member 56 and the second strut member 58 and is screwed with the second strut member 58. The adjusting lever 54 extends the strut 52 by rotating the adjusting wheel 60a in one direction and moving the second strut member 58 to the brake shoe 18 side by the action of the screw of the adjusting shaft 60, thereby extending the pair of brake shoes 18, 20 The shoe gap is adjusted by separating them. The brake shoes 18 and 20 are formed with support protrusions 18a and 20a, respectively, protruding toward the other side in order to support the first strut member 56 and the second strut member 58, that is, the strut 52.

  As shown in FIG. 3, a fitting hole 60 c is formed in the end surface 60 b on the first strut member 56 side of the adjustment shaft 60, and the first strut member 56 has a fitting hole 60 c in the adjustment shaft 60. Is provided with a shaft portion 56a fitted to be relatively rotatable.

  As shown in FIG. 4, the first strut member 56 and the shaft portion 56 a provided on the first strut member 56 are formed in a plate shape having a uniform thickness, and a single steel plate having a uniform plate thickness is subjected to press working. This is formed integrally. That is, after the first strut member 56 is punched from the plate material by punching, the shaft portion 56a of the first strut member 56 is put into a molding die and compressed in order to remove the corner formed by the punching processing. The cross section 56b of the shaft portion 56a is compressed and deformed into a circular shape having a diameter equivalent to the thickness of the first strut member 56. In this way, by removing the corner from the shaft portion 56a, the shaft portion 56a can be smoothly and relatively rotated within the fitting hole 60c, or the shaft portion 56a can be rotated within the fitting hole 60c. Even if the shaft portion 56a and the inner peripheral surface of the fitting hole 60c are slidably contacted with each other, the shaft portion 56 is not easily worn in the fitting hole 60c. It becomes difficult.

  As shown in FIGS. 2 and 5, the adjustment lever 54 is made of, for example, a spring plate material. The adjustment lever 54 includes a stopper portion 54 a extending from one end portion toward the adjustment shaft 60, and the other end. Spring receiving portions 54b projecting from the side opposite to the backing plate 16 side, and a pair of parallel parallel members attached to the first strut member 56 extending from both side edges of the intermediate portion to the side opposite to the backing plate 16 side. Mounting portions 54c, 54d, a sliding contact portion 54e extended from a part of the mounting portion 54c to the brake shoe 18 side, a wheel engaging portion 54f extended from a part of the mounting portion 54d to the brake shoe 18 side, A shoe engaging portion 54g extending from a part of the attaching portion 54d to the side opposite to the backing plate 16 side is further provided. Further, the pair of attachment portions 54c and 54d are provided with a pair of fitting holes 54h for fitting the connecting pins 61 for connecting the first strut member 56 and the adjusting lever 54 so as to be relatively rotatable. The first strut member 56 is provided with a fitting hole 56c for fitting the connecting pin 61 so as to be relatively rotatable. Further, the adjustment lever 54, the stopper portion 54a, the spring receiving portion 54b, the pair of attachment portions 54c and 54d, the sliding contact portion 54e, the wheel engagement portion 54f, the shoe engagement portion 54g, and the pair of fitting holes 54h are formed by pressing. It is integrally formed from a single metal plate.

  A coiled spring 62 compressed as shown in FIG. 2 is attached between the spring receiving portion 54 b and the first strut member 56, and the spring receiving portion 54 b is connected by the urging force of the spring 62. The pin 61 is rotated around the backing plate 16 side. That is, the adjustment lever 54 is always urged around the connecting pin 61 in the direction of arrow F by the urging force of the spring 62. As shown in FIGS. 2 and 3, the first strut member 56 is provided with a protruding portion 56d protruding toward the spring receiving portion 54b of the adjusting lever 54, as shown in FIGS. The coiled spring 62 is supported by the spring receiving portion 54b so as not to drop off.

  The stopper portion 54a is disposed so as to come into contact with the adjusting shaft 60 when the adjusting lever 54 is rotated by a predetermined amount or more around the connecting pin 61 by the biasing force of the coiled spring 62. The adjusting lever 54 is allowed to rotate by a predetermined amount or more so as not to impair the assembling workability with respect to the pair of brake shoes 18 and 20 while allowing the adjusting lever 54 to rotate during adjustment. Stop.

  The parking brake lever 48 is provided with a parking brake cable 64 connected to the tip of the parking brake lever 48, and the tip of the parking brake lever 48 is attached to the backing plate 16 via the parking brake cable 64 by operating a parking lever (not shown). When the brake shoe 20 is rotated to the center side, the brake shoe 20 is pushed by the strut 52 and moved to the outer peripheral side, and the brake shoe 18 is pushed by the pin 50 and moved to the outer peripheral side. 20 is expanded so that a braking force is generated.

  The drum brake 10 configured as described above is expanded in a direction in which one end portions of the pair of brake shoes 18 and 20 are separated from each other by a piston of the wheel cylinder 22 protruding in accordance with a brake pedal operation (not shown). A braking force is generated. As the pair of brake shoes 18 and 20 expand, the shoe engaging portion 54g of the adjustment lever 54 expands the pair of brake shoes 18 and 20 in the direction of arrow F around the connecting pin 61 by the urging force of the spring 62. Accordingly, the wheel engaging portion 54f of the adjusting lever 54 is also moved in the direction of arrow F while being in contact with the adjusting wheel 60a. At this time, the wheel engagement portion 54f applies rotational torque to the adjustment wheel 60a. The adjustment wheel 60a is parallel to the wheel engagement portion 54f shown in FIGS. 6 and 7, and is in sliding contact with the adjustment wheel 60a. Since it is pinched by the part 54e and the wheel engaging part 54f, it cannot rotate. Further, the alternate long and short dash line in FIG. 6 shows a state in which the wheel engaging portion 54f has moved in the arrow F direction in a state where the wheel engaging portion 54f is in contact with the adjustment wheel 60a.

  Each time the drum brake 10 is actuated, the adjustment wheel 60a is rotated without meshing between the wheel engagement portion 54f and the adjustment wheel 60a unless the moving position of the wheel engagement portion 54f exceeds one tooth of the adjustment wheel 60a. However, when the moving position of the wheel engaging portion 54f gets over one tooth of the adjusting wheel 60a and meshes with the adjusting wheel 60a, the wheel engaging portion 54f moves in the direction of arrow F by the return of the adjusting lever 54 when the braking force is released. The adjusting wheel 60a is rotated in the opposite direction. As a result, when the amount of expansion of the pair of brake shoes 18, 20 exceeds a predetermined value due to wear of the pair of brake shoes 18, 20, the adjustment wheel 60 a is rotated to move the linings 40, 42 and the brake drum 12. The gap with the peripheral surface 14 is automatically adjusted.

  According to the drum brake 10 provided with the shoe gap automatic adjusting mechanism 26 of this embodiment, (a) the fitting hole 60c is formed in the end surface 60b on the first strut member 56 side of the adjusting shaft 60, and (b) the second. The one strut member 56 is provided with a shaft portion 56a that fits in the fitting hole 60c of the adjustment shaft 60 so as to be relatively rotatable, and (c) the first strut member 56 is formed by press working. Conventionally, the fitting hole provided in the first strut member is formed in the adjustment shaft 60, and the first strut member 56 does not require a portion where the plate thickness is locally increased to provide the fitting hole. Thus, a relatively uniform plate thickness is formed. Thereby, it is possible to change from forging and cutting which have been conventionally required for forming the first strut member to press processing which is relatively inexpensive in forming cost, and the forming cost of the first strut member 56 is reduced.

  Further, according to the drum brake 10 having the shoe gap automatic adjusting mechanism 26 of the present embodiment, the shaft portion 56a of the first strut member 56 is integrally formed by press working, so that the first strut member The number of parts 56 can be reduced and the molding cost of the first strut member 56 can be further reduced.

  Further, according to the drum brake 10 having the shoe gap automatic adjusting mechanism 26 of the present embodiment, the adjusting shaft 60 is screwed with the second strut member 58 at one end and the first strut member 56 at the other end. Since the adjustment wheel 60a is provided between the one end and the other end of the adjustment shaft 60a, the adjustment shaft 60 is connected to the shaft end on the other end side. The distance can be set short.

  Another embodiment of the present invention will be described. In the following other embodiments, portions common to the above-described embodiments are denoted by the same reference numerals and description thereof is omitted.

  The drum brake of this embodiment is the same as the drum brake 10 except that a shoe gap automatic adjustment mechanism 66 different from the above-described embodiment is provided, and FIG. 8 shows the shoe gap automatic adjustment mechanism 66 of the other embodiments. It is a figure to explain and corresponds to FIG.

  As shown in FIG. 8, the shoe gap automatic adjusting mechanism 66 is stretched between one end portions of a pair of brake shoes 18 and 20, and a strut 68 that defines a standby position of the pair of brake shoes 18 and 20 during non-braking. And an adjusting lever 54 provided in the strut 68.

  As shown in FIG. 8, the strut 68 includes a first strut member 56 that engages the shoe web 34, a second strut member 70 that engages the shoe web 32 and the parking brake lever 48, and an adjustment wheel 72a. An adjusting shaft 72 is provided between the first strut member 56 and the second strut member 70 and is screwed with the second strut member 70. The adjustment lever 54 extends the strut 68 by rotating the adjustment wheel 72a in one direction and moving the second strut member 70 to the brake shoe 18 side by the action of the screw of the adjustment shaft 72, and the pair of brake shoes 18, 20 The shoe gap is adjusted by separating them.

  As shown in FIG. 9, a female screw 72 c that opens to the end surface 72 b is formed on the adjustment shaft 72 on the second strut member 70 side, and the second strut member 70 is screwed to the female screw 72 c of the adjustment shaft 72. A male screw 70a is provided. A fitting hole 72e is formed in the end surface 72d of the adjustment shaft 72 on the first strut member 56 side, and the fitting hole 72e is the same as the fitting hole 60c in the above-described embodiment.

  As shown in FIG. 10, the second strut member 70 and the male screw 70 a provided on the second strut member 70 are formed in a plate shape having a uniform thickness, and a single steel plate having a uniform plate thickness is subjected to press working. It is formed integrally by. That is, after the second strut member 70 is punched from the plate material by punching, the male screw 70a of the second strut member 70 is first put into a molding die in order to remove corners formed by the punching. The cross section 70f is compressed and deformed into a circular shape having a diameter equivalent to the thickness of the second strut member 70 to be formed into a cylindrical member, and then the cylindrical member is screw-rolled. A male screw that is screwed into the female screw 72c is rolled by a die.

  According to the drum brake having the shoe gap automatic adjusting mechanism 66 of the present embodiment, the second strut member 70 is formed by press working, and therefore the second strut member 70 is formed by forging and cutting. Compared to this, the molding cost is low, and the manufacturing cost of the drum brake can be further reduced.

  As mentioned above, although the Example of this invention was described based on drawing, this invention is applied also in another aspect.

  For example, in the drum brake 10 provided with the shoe gap automatic adjusting mechanism 26 of the present invention, the adjusting shaft 60 is screwed at one end thereof to the second strut member 58 and has a fitting hole 60c on the end surface 60b at the other end. Although formed, a female screw and a male screw are formed in the fitting hole 60c of the other end portion of the adjustment shaft 60 and the shaft portion 60a of the first strut member 56, and they are screwed together so that one end portion of the adjusting shaft 60 is formed. A fitting hole may be formed in the end face, and the shaft portion protruding from the second strut member 58 may be fitted into the fitting hole so as to be relatively rotatable. In such a case, the wheel engaging portion 54f of the adjusting lever 54 is adjusted so that the adjusting wheel 60a is rotated and the adjusting wheel 60a and the adjusting lever 54 are separated, whereby the wheel engaging portion 54f of the adjusting lever 54 is adjusted. The one extended sufficiently to the brake shoe 18 side so as not to be detached from the wheel 60a is applied. In such a case, similarly to the first strut member 56, the second strut member 58 can be formed of a press-formed product.

  Further, if the adjusting wheel is rotated in one direction and the strut extends, there is no problem even if both ends of the adjusting shaft 60 are screwed into the first strut member 56 and the second strut member 58.

  Further, in the drum brake 10 provided with the shoe gap automatic adjusting mechanism 26 of the present invention, the shaft portion 56a of the first strut member 56 is compressed so that the cross section 56b is circular, but it is not necessarily circular. Any shape can be used as long as the shaft portion 56a can be relatively rotated in the fitting hole 60c, for example, the shaft portion 56a of the first strut member 56 is formed by only punching. It may remain in shape.

  Although not illustrated one by one, the present invention can be implemented in variously modified and improved modes based on the knowledge of those skilled in the art.

1 is a front view showing a leading trailing drum brake according to an embodiment of the present invention. It is the II-II sectional view taken on the line of FIG. It is an enlarged view for demonstrating the 1st strut member and adjustment shaft with which the drum brake of the Example of FIG. 1 was equipped. FIG. 4 is a sectional view taken along line IV-IV in FIG. 3. It is an enlarged view for demonstrating the structure of an adjustment lever. FIG. 6 is a sectional view taken along line VI-VI in FIG. 2. FIG. 7 is a VII-VII view of FIG. 2. It is a figure which shows the shoe gap automatic adjustment mechanism of the other Example of this invention, and respond | corresponds to FIG. It is an enlarged view for demonstrating the 2nd strut member with which the drum brake of the other Example of FIG. 8 was equipped, and the adjustment shaft. FIG. 10 is a sectional view taken along line XX in FIG. 9.

Explanation of symbols

10: Drum brake 12: Brake drum (rotating drum)
18, 20: A pair of brake shoes 26, 66: Automatic shoe clearance adjustment mechanisms 52, 68: Struts 54: Adjusting lever 56: First strut member 56a: Shaft 58, 70: Second strut members 60a, 72a: Adjusting wheel 60b: End surfaces 60c, 72e: Fitting holes 60, 72: Adjustment shaft

Claims (4)

A first strut member that engages with one of the pair of brake shoes that can be expanded, a second strut member that engages with the other of the pair of brake shoes, and an adjustment wheel, the first strut member and the second strut member. A strut having an adjustment shaft disposed between the strut members and screwed into at least one strut member, and defining a standby position of the pair of brake shoes during non-braking;
An adjustment lever that rotates the adjustment wheel in one direction in accordance with the amount of expansion of the pair of brake shoes during braking,
An automatic shoe clearance adjustment mechanism that automatically adjusts the shoe clearance between the pair of brake shoes and the rotating drum when the brake is not braked when the adjustment wheel is rotated by the adjustment lever and the strut extends. In the provided drum brake,
A fitting hole is formed in the end surface of the adjustment shaft on the first strut member side,
The first strut member includes a shaft portion that fits in the fitting hole of the adjustment shaft so as to be relatively rotatable,
The drum brake provided with a shoe gap automatic adjusting mechanism, wherein the first strut member is formed by press working.   2. The drum brake having an automatic shoe clearance adjusting mechanism according to claim 1, wherein the shaft portion of the first strut member is integrally formed by pressing.   The adjustment shaft is threadedly engaged with the second strut member at one end thereof, and is fitted to the shaft portion of the first strut member at the other end so as to be relatively rotatable, and between the one end and the other end. The drum brake provided with the shoe gap automatic adjusting mechanism according to claim 1 or 2, wherein the adjusting wheel is provided with the adjusting wheel.   The drum brake provided with the shoe gap automatic adjusting mechanism according to any one of claims 1 to 3, wherein the second strut member is formed by press working.

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