JP2008281179A - Drum brake provided with automatic shoe clearance adjusting mechanism - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a brake provided with an automatic shoe clearance adjusting mechanism wherein friction generated during braking between first and second strut members can be reduced. <P>SOLUTION: The drum brake includes a coil spring (elastic member) 62 which is provided in a receiving hole 58a for urging a first strut member 56 and a second strut member 58 in the direction for separating from each other. The spring 62 is provided in the receiving hole 58a which is made on the axis C between the first and second strut members 56, 58 respectively; under application of a drum brake 10, the first and second strut members 56, 58 are urged nearly parallel in the direction of the axis C. Thus, the friction between the screw part 56a of the first strut member 56 and the inner peripheral surface of the receiving hole 58a of the second strut member 58 is reduced greatly. <P>COPYRIGHT: (C)2009,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 improving the performance of a drum brake by changing the structure of an automatic shoe clearance adjustment mechanism.

  For example, as shown in Patent Document 1, for example, (a) a first strut member that includes a screw portion at one end and engages one end of a pair of brake shoes, as shown in Patent Document 1, for example, The first strut includes a second strut member having a receiving hole opened at one end for receiving the screw portion of the first strut member and the other end engaging the other of the pair of brake shoes, and a star wheel. An adjustment nut that engages with the screw portion of the member, and a strut that defines the distance between the pair of brake shoes during non-braking, and (b) an engagement portion that is engaged with the star wheel at the tip portion In addition, the star wheel is rotated in one direction in conjunction with the relative movement in the axial direction between the first strut member and the second strut member during braking. There is one and a Sutoreba.

In general, the shoe gap automatic adjustment mechanism as described above is stretched between one of the pair of brake shoes and the first strut member and between the other of the pair of brake shoes and the second strut member. A pair of return springs are provided, and the first strut member and the second strut member are urged by the biasing force of the pair of return springs during braking so that the first strut member and the second strut member correspond to the amount of expansion of the pair of brake shoes. The first strut member and the second strut member move relative to each other in the axial direction.
JP 58-77931 A

  However, in the conventional shoe gap automatic adjustment mechanism as described above, the pair of return springs urge the first strut member and the second strut member in parallel with high precision in the axial direction. Since an eccentric load is applied to the first strut member and the second strut member by the urging force of the pair of return springs, the screw portion of the first strut member and the inner periphery of the receiving hole of the second strut member during braking There is a possibility that a relatively large friction is generated between the surfaces and the first strut member and the second strut member cannot be smoothly moved relative to each other, and the operation of the shoe gap automatic adjusting mechanism cannot be obtained smoothly.

  The present invention has been made against the background of the above circumstances, and its object is to provide a shoe gap that can reduce friction generated between the first strut member and the second strut member during braking. It is to provide a drum brake having an automatic adjustment mechanism.

  To achieve this object, the gist of the invention according to claim 1 is that: (a) a first strut member having a screw portion at one end and engaging the other end with one of a pair of brake shoes; A first strut member having a receiving hole that opens at one end for receiving a screw portion of the first strut member, the other end engaging with the other of the pair of brake shoes, and a star wheel; An adjusting nut that engages with the threaded portion of the screw strut, and a strut that defines the distance between the pair of brake shoes during non-braking, and (b) an engaging portion that is engaged with the star wheel at the distal end. The base end portion is attached to the second strut member, and the star is interlocked with the relative movement in the axial direction between the first strut member and the second strut member during braking. In a drum brake having an automatic shoe clearance adjustment mechanism having an adjustment lever for rotating the reel in one direction, (c) elasticity for urging the first strut member and the second strut member in a separating direction A member is provided in the receiving hole.

  The gist of the invention according to claim 2 is that, in the invention according to claim 1, (a) an insertion hole into which the screw portion is inserted is provided, and the gap between the adjustment nut and the second strut member is provided. A lever member having a first lever portion sandwiched between and a second lever portion bent at a predetermined angle greater than a right angle with respect to the first lever member; and (b) the first lever portion includes: The tip end portion of the first lever portion on the adjustment nut side is notched, and (c) when not braked, the first lever portion of the lever member is clamped between the second strut member and the adjustment nut. The second lever portion is configured to push and bend the adjusting lever against a biasing force in a direction in which the engaging portion moves away from the star wheel, and (d) at the time of braking, the second strut member and the adjustment According to the separation from the nut, the second lever portion is brought close to the second strut member according to the urging force of the adjustment lever, and the engaging portion of the adjustment lever rotates the star wheel in one direction.

  The gist of the invention according to claim 3 is that, in the invention according to claim 1 or 2, the first strut member is engaged with the adjustment nut at the front end portion of the adjustment lever, and the second strut member is engaged with the adjustment nut. A stopper portion for preventing the member from falling off is provided.

  According to a fourth aspect of the present invention, there is provided a gist of the invention according to any one of the first to third aspects, wherein the end of the adjusting lever is opposite to the engaging portion with the star wheel interposed therebetween. Is provided with a sliding contact portion which is located at the center and is brought into sliding contact with the outer peripheral teeth of the star wheel.

  Further, the gist of the invention according to claim 5 is that, in the invention according to any one of claims 1 to 4, the base end portion of the adjustment lever is the second so as to grip the second strut member. It exists in being fitted to the strut member.

  Further, the gist of the invention according to claim 6 is that, in the invention according to any one of claims 1 to 5, the fitting for fitting the base end portion into the predetermined position of the second strut member. The groove is provided.

  According to the drum brake having the shoe gap automatic adjusting mechanism of the invention according to claim 1, an elastic member for urging the first strut member and the second strut member in the direction of separating is provided in the receiving hole. Therefore, the first strut member and the second strut member are arranged between the first strut member and the second strut member, and the first strut member and the second strut member are arranged at the time of braking by the elastic member disposed in the receiving hole. Since it is biased in a direction away from the axial center with high accuracy, the friction between the first strut member and the second strut member can be greatly reduced. Therefore, the operation of the shoe clearance automatic adjusting mechanism can be obtained smoothly.

  According to the drum brake having the shoe gap automatic adjusting mechanism according to the second aspect of the present invention, (a) the insertion portion into which the screw portion is inserted has an insertion hole between the adjustment nut and the second strut member. A lever member having a first lever portion sandwiched between and a second lever portion bent at a predetermined angle greater than a right angle with respect to the first lever member; and (b) the first lever portion includes: The tip end portion of the first lever portion on the adjustment nut side is notched, and (c) when not braked, the first lever portion of the lever member is clamped between the second strut member and the adjustment nut. The second lever portion pushes and bends the adjust lever against the urging force in a direction in which the engaging portion moves away from the star wheel. (D) During braking, the second strut member and the The second lever portion is brought close to the second strut member according to the biasing force of the adjusting lever according to the separation from the adjusting nut, and the engaging portion of the adjusting lever rotates the star wheel in one direction. The lever member has an axial center direction between the first strut member and the second strut member at the time of braking by a notch cut out at a tip portion of the first lever portion on the adjustment lever side. The amount by which the second lever portion approaches the second strut member can be increased in conjunction with the relative movement, and the notch is used to increase the relative axial relation between the first strut member and the second strut member. The amount of movement of the engaging portion of the adjusting lever that is linked to the movement can be increased. Therefore, by providing the notch in the lever member, it is possible to easily adjust the amount of movement of the engaging portion of the adjusting lever during braking.

  According to the drum brake having the shoe gap automatic adjusting mechanism of the invention according to claim 3, the first strut member is engaged with the adjustment nut at the tip end portion of the adjustment lever from the second strut member. Since the stopper portion is provided to prevent it from falling off, the first strut member and the second strut member are separated by the elastic member when the shoe gap automatic adjusting mechanism is assembled to the drum brake. Thus, the first strut member is prevented from falling off from the second strut member, so that the assembly process of the drum brake can be facilitated.

  According to the drum brake having the shoe gap automatic adjusting mechanism of the invention according to claim 4, the leading end portion of the adjusting lever is located on the opposite side of the engaging portion with the star wheel interposed therebetween. Since the sliding contact portion that is brought into sliding contact with the outer peripheral teeth of the wheel is provided, the star wheel is engaged even when the engaging portion of the adjusting lever moves on the outer peripheral teeth of the star wheel during braking or non-braking. Is in a state of being sandwiched between the sliding contact portion and the engagement portion, so that the star wheel is prevented from rotating due to the repetitive movement of the adjusting lever during braking and during non-braking.

  According to the drum brake having the shoe gap automatic adjusting mechanism of the invention according to claim 5, the base end portion of the adjustment lever is fitted to the second strut member so as to grip the second strut member. Therefore, since the adjustment lever can be assembled to the second strut member by the base end of the adjustment lever, it is possible to omit the assembly parts and the assembly process that were conventionally required when installing the adjustment lever. The cost for manufacturing the drum brake can be reduced.

  According to the drum brake having the shoe gap automatic adjusting mechanism of the invention according to claim 6, a fitting groove for fitting the base end portion is provided at a predetermined position of the second strut member. Therefore, the adjustment lever can be assembled to the second strut member simply by moving the base end portion of the adjustment lever to the fitting groove, so that the assembly process of the adjustment lever can be simplified. .

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In the following embodiments, the drawings are simplified, and the dimensions and the like of each part are not necessarily drawn accurately.

  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 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 it, a coiled return spring 24 stretched between its one end portions and a non-braking state spanned between one end portions of the pair of brake shoes 18 and 20 An automatic shoe gap adjusting mechanism for automatically adjusting the shoe gap between the pair of brake shoes 18 and 20 and the brake drum 12. 6 and the other end of the pair of brake shoes 18 and 20, that is, between the lower end of FIG. 1, the anchor 28 fixed to the backing plate 16 and the lower end of the pair of brake shoes 18 and 20. And a spring 30 that is provided so that the lower ends thereof 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 adjusting mechanism 26 is spanned between one end portions of the pair of brake shoes 18, 20, and the distance between the pair of brake shoes 18, 20 when not braked, that is, the pair of brake shoes 18. , 20 and the inner peripheral surface 14 of the brake drum 12, a strut 52 that defines a gap, and an adjustment lever 54 provided in the strut 52.

  As shown in FIG. 2, the strut 52 includes a screw portion 56 a having an outer peripheral surface threaded at one end, and a first strut member 56 that engages the shoe web 32 of the brake shoe 18 at the other end, and the first strut member 56. In order to receive the screw portion 56a of the strut member 56, the first strut member 58 is provided with a receiving hole 58a opened at one end and the other end engaged with the shoe web 34 of the brake shoe 20, and a star wheel 60a. In order to bias the adjusting nut 60 screwed into the threaded portion 56a of the strut member 56, and the first strut member 56 and the second strut member 58 in a separating direction, the threaded portion 56a of the first strut member 56 and the second strut A coiled spring (elastic member) 62 disposed in a compressed state between the bottom surface 58b in the receiving hole 58a of the member 58; Eteiru. 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.

  The coiled spring 62 urges the first strut member 56 and the second strut member 58 in a direction to separate the first strut member 56 and the second strut member 58 with a force smaller than the urging force of the return spring 24. The first strut member 56 and the second strut member 58 cannot be separated from each other by the urging force, that is, the pair of brake shoes 18 and 20 cannot be expanded. However, when the drum brake 10 is braked, the pair of brake shoes 18 and 20 are expanded by the wheel cylinder 22, so that the first strut member 56 and the second strut member 58 are braked by the urging force of the spring 62. It is moved in a direction away from each other so as to fill a gap between the shoe 18 and the first strut member 56 and between the brake shoe 20 and the second strut member 58. Therefore, the amount of expansion of the pair of brake shoes 18 and 20 is substantially the same as the amount of relative movement of the first strut member 56 and the second strut member 58 in the direction of the axis C, that is, the distance between them.

  The coiled spring 62 is formed between the screw portion 56 a of the first strut member 56 and the bottom surface 58 b of the receiving hole 58 a of the second strut member 58 and the axial center of the first strut member 56 and the second strut member 58. Since the spring 62 is disposed in the receiving hole 58a concentrically with C, the direction in which the spring 62 urges the first strut member 56 and the second strut member 58 and the first strut member 56 and the second strut member 58 are The direction of the axis C substantially coincides with accuracy. Therefore, when the drum brake 10 is braked, an eccentric load is hardly applied to the first strut member 56 and the second strut member 58 by the urging force of the spring 62, and the screw portion 56a and the second strut member of the first strut member 56 are applied. The first strut member 56 and the second strut member 58 are smoothly moved relative to each other, that is, separated from each other, with little friction occurring between the inner peripheral surface of the receiving hole 58a.

  As shown in FIGS. 2 and 3, the adjustment lever 54 is made of, for example, a spring plate material, and a base end portion 54 a for attaching the adjustment lever 54 to the second strut member 58, and the brake shoe 20 from the base end portion 54 a. An engaging protrusion 54b that extends to the side and engages with the second strut member 58, an engaging portion 54c that is provided at the tip of the adjusting lever 54 and engages with the star wheel 60a of the adjusting nut 60, and the adjusting lever 54 Slidably engaging part 54d that is located on the opposite side of the engaging part 54c across the star wheel 60a and is slidably contacted with the outer peripheral teeth of the star wheel 60a, and the tip of the slidable engaging part 54d The stopper part 54e extended from the part to the engaging part 54c side is provided. The adjusting lever 54, the base end portion 54a, the engaging protrusion 54b, the engaging portion 54c, the sliding contact engaging portion 54d, and the stopper portion 54e are integrally formed from a single metal plate by pressing. .

  As shown in FIG. 4, the base end portion 54a is provided with a pair of fitting portions 54f formed opposite to each other so as to embrace the second strut member 58 from both sides thereof. Since the portion 54f is fitted to the second strut member 58 so as to hold the second strut member 58, the adjust lever 54 is fixed to the second lever member 58 via the pair of fitting portions 54f. ing. For this reason, it is possible to omit the assembly parts and the assembly process thereof, such as the rivet caulking rivet and the rivet caulking process, which have been conventionally required when the adjust lever is assembled. In addition, the second strut member 58 is fitted with a portion slightly larger than the fitting portion 54f in the longitudinal direction in order to fit the pair of fitting portions 54f of the base end portion 54a as shown in FIG. A groove 58e is provided in the circumferential direction, and the adjustment lever 54 is restrained from moving in the axial center C direction of the second strut 58 by fitting the pair of fitting portions 54f into the fitting groove 58e. The In other words, the adjusting lever 54 is fixed to the second strut member 58 via the pair of fitting portions 54f of the base end portion 54a by the engaging protrusion 54b and the fitting groove 58e. Further, the assembly process of the adjusting lever 54 is simple because it only moves the pair of fitting portions 54f of the base end portion 54 from one end of the second strut member 58 into the fitting groove 58e.

  As shown in FIGS. 2 and 3, the engagement protrusions 54 b are arranged at the base ends at intervals slightly larger than the thickness of the end portions of the second strut members 58 so as to sandwich both side surfaces 58 d of the end portions of the second strut members 58. A pair of protrusions extending from the portion 54a to the brake shoe 20 side. Therefore, when the adjustment lever 54 tries to rotate around the axis C of the second strut member 58 due to vibration or the like during traveling of the vehicle, the pair of protrusions that are the engaging protrusions 54b are not connected to the second strut member 58. Since it contacts the both side surfaces 58d, the adjustment lever 54 is prevented from rotating.

  When the first strut member 56 and the second strut member 58 are separated by a predetermined amount or more by the biasing force of the coiled spring 62, the stopper portion 54e is an adjustment nut that is screwed into the screw portion 56a of the first strut member 56. 60 is extended from the front end of the sliding contact portion 54d so as to be in contact with the engagement portion 54c. When the shoe gap automatic adjustment mechanism 26 is assembled to the drum brake 10, the biasing force of the coiled spring 62 is applied. Thus, the operator can handle the shoe gap adjusting mechanism 26 while holding the shoe gap adjusting mechanism 26 so that the first strut member 56 and the second strut member 58 are not separated from each other and the first strut member 56 is not detached from the second strut member 58. This eliminates the drum brake assembly process.

  As shown in FIGS. 2, 3, and 5, an insertion hole 64 a into which the screw portion 56 a of the first strut member 56 is inserted is provided between the adjustment nut 60 and the second strut member 58. A substantially cylindrical first lever portion 64b sandwiched between the second strut member 58 and a plate-like second member bent at a predetermined angle larger than a right angle with respect to the first lever portion 64b, for example, about 100 °. A lever member 64 constituted by a lever portion 64c is provided, and the tip end portion of the second lever portion 64c abuts against the central portion of the adjusting lever 54 and is urged in the direction of arrow F shown in FIG. .

  According to FIG. 5A showing the state of the drum brake 10 when it is not braked, the first lever portion 64b of the lever member 64 is urged by the adjustment lever 54, whereby the second strut member 58 and the adjustment nut are urged. 60, that is, the first strut member 56 is biased so as to be separated. However, since the first lever portion 64 b of the lever member 64 is clamped between the second strut member 58 and the adjustment nut 60 by the urging force of the return spring 24, the second lever portion 64 c of the lever member 64 is connected to the adjustment lever 54. The adjustment lever 54 is pushed and bent in a direction away from the first strut member 56 against the biasing force. The combined force of the urging force of the adjusting lever 54 and the urging force of the coiled spring (elastic member) 62 is smaller than the urging force of the return spring 24.

  According to FIG. 5 (b) showing the state of the brake of the drum brake 10, the first lever portion 64 b of the lever member 64 is formed between the second strut 58 and the adjustment nut 60 by the urging force of the coiled spring 62. The tip end portion of the second lever portion 64c is tilted by the urging force of the adjusting lever 54 according to the amount of separation, and the adjusting lever 54 is moved in the direction of arrow F.

  Returning to FIG. 1, the parking brake lever 48 is provided with a parking brake cable 66 connected to the tip of the parking brake lever 48, and the tip of the parking brake lever 48 is operated via the parking brake cable 66 by operating a parking lever (not shown). Is rotated toward the center side of the backing plate 16, the brake shoe 20 is pushed by the strut 52 and moved to the outer circumferential side, and the brake shoe 18 is pushed by the pin 50 and moved to the outer circumferential side. The brake shoes 18 and 20 are expanded to generate a braking force.

  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, 20 are expanded, the first strut member 56 and the second strut member 58 cause the first strut member 56 and the second strut member 58 to be moved by the biasing force of the coiled spring 62. The adjustment lever 54 is moved in the direction of arrow F via the lever member 64 according to the distance and the amount of separation.

  As shown in FIG. 6, when the adjustment lever 54 is moved in the direction of arrow F, the engagement portion 54c provided at the tip of the adjustment lever 54 is in the state of being in contact with the outer peripheral teeth of the star wheel 60a. It is moved in the F direction. At this time, the engaging portion 54c applies rotational torque to the star wheel 60a. The star wheel 60a is substantially parallel to the engaging portion 54c shown in FIG. 6 and is in sliding contact with the star wheel 60a. Since it is pinched by 54d and the engaging part 54c, it cannot rotate. Further, when the braking state of the drum brake 10 is released and the engaging portion 54c is in contact with the outer peripheral teeth of the star wheel 60a, the drum brake 10 is moved in the opposite direction to the arrow F direction, and rotational torque is applied to the star wheel 60a. However, since the star wheel 60a is sandwiched between the sliding contact engaging portion 54d and the engaging portion 54c, the star wheel 60a cannot rotate. That is, even if the rotational torque is generated in the star wheel 60a by the sliding contact engaging portion 54d and the engaging portion 54c due to the reciprocating movement of the engaging portion 54c of the adjusting lever 54 when the drum brake 10 is braked or not braked. The star wheel 60a is prevented from rotating together with the engaging portion 54c.

  Each time the drum brake 10 is actuated, if the moving position of the engaging portion 54c does not exceed one tooth of the star wheel 60a, the star wheel 60a can be rotated without meshing the engaging portion 54c and the star wheel 60a. Absent. However, when the moving position of the engaging portion 54c passes over one tooth of the star wheel 60a and meshes with the star wheel 60a, the engaging portion 54c is moved in the direction of the arrow F by the return of the adjusting lever 54 when the braking force of the drum brake 10 is released. The star wheel 60a is rotated in the opposite direction and the strut 52 is extended by the action of the screw of the adjusting nut 60 to adjust the shoe gap. As a result, when the spread amount of the pair of brake shoes 18, 20 exceeds a predetermined value due to wear of the pair of brake shoes 18, 20, the star wheel 60 a is rotated, and the inside of the linings 40, 42 and the brake drum 12 The gap with the peripheral surface 14 is automatically adjusted.

  As shown in FIG. 7 which shows the lever member 64 shown in FIG. 5 in an enlarged manner, the first lever portion 64b of the lever member 64 has a stepped end portion on the adjustment nut 60 side of the first lever portion 64b. A cutout 68 is provided. Due to the notches 68, the first lever portion 64b of the lever member 64 has a distance A in the direction of the axis C between the first strut member 56 and the second strut member 58 when the drum brake 10 is braked. Since the first lever portion 64b having the notch 68 is shorter than the distance B of the first lever portion 64b, the distance D that is the difference between the first lever portion 64b and the first lever portion 64b having the notch 68 is set to the second distance D. The distal end portion of the lever portion 64c is further moved closer to the second strut member 58 and increased. Therefore, if the lever member 64 increases the width E of the notch 68 by the notch 68, the relative movement in the direction of the axis C between the first strut member 56 and the second strut member 58 when the drum brake 10 is braked. The amount by which the tip of the second lever portion 64c approaches the second strut member 58 with respect to the amount can be increased. That is, by adjusting the width E of the notch 68, the engaging portion 54c of the adjusting lever 54 moves in the direction of arrow F with respect to the distance between the first strut member 56 and the second strut member when the drum brake 10 is braked. The amount can be adjusted. A one-dot chain line shown in FIG. 7 shows a state of the lever member 64 when the drum brake 10 is braked.

  As shown in FIG. 8, the first lever portion 64b of the lever member 64 is brought into point contact with the second strut member 58 at the point (1) in the surface 64d on the second strut 58 side by the biasing force of the adjusting lever 54. Then, a line connecting the point (2) and the point (3) in the surface 64e on the adjustment nut 60 side, that is, the edge of the notch 68 is in line contact with the adjustment nut 60. Therefore, the lever member 64 is sandwiched between the second strut member 58 and the adjusting nut 60 via the point (1) and the line connecting the point (2) and the point (3). Rotation around the axis C due to vibration of the shaft is prevented.

  According to the drum brake 10 having the shoe gap automatic adjusting mechanism 26 of the present embodiment, the coiled spring (elastic member) 62 that urges the first strut member 56 and the second strut member 58 in the direction of separating them is provided. The drum brake 10 is provided by a spring 62 provided in the receiving hole 58a and disposed in the receiving hole 58a between the first strut member 56 and the second strut member 58 and on the axis C thereof. During braking, the first strut member 56 and the second strut member 58 are biased in a direction that is separated from the axial center C in a direction that is accurately parallel to each other. Friction with the inner peripheral surface of the receiving hole 58a of the strut member 58 can be greatly reduced.

  Further, according to the drum brake 10 having the shoe gap automatic adjusting mechanism 26 of the present embodiment, the pair of fitting members 54f of the base end portion 54a of the adjusting lever 54 is arranged so as to grip the second strut member 58. Since the adjustment lever 54 is fitted to the second strut member 58 and can be assembled to the second strut member 58 by the pair of fitting members 54f of the base end portion 54a of the adjustment lever 54, the conventional adjustment lever assembly Assembling parts and an assembling process required at the time of attaching can be omitted, and the cost for manufacturing the drum brake 10 can be reduced.

  Further, according to the drum brake 10 having the shoe gap automatic adjusting mechanism 26 of the present embodiment, the fitting for fitting the pair of fitting members 54f of the base end portion 54a to the predetermined positions of the second strut member 58. A fitting groove 58e is provided, and the adjustment lever 54 can be assembled to the second strut member 58 simply by moving the pair of fitting members 54f of the base end portion 54a of the adjustment lever 54 to the fitting groove 58e. The assembly process of the adjustment lever 54 can be simplified.

  Further, according to the drum brake 10 having the shoe gap automatic adjusting mechanism 26 of the present embodiment, (a) the insertion portion 64a into which the screw portion 56a is inserted, and the adjustment nut 60 and the second strut member 58 are provided. And (b) further including a lever member 64 having a first lever portion 64b sandwiched between and a second lever portion 64c bent at, for example, about 100 ° larger than a right angle with respect to the first lever portion 64b. The first lever portion 64b is cut off at the tip end portion of the first lever portion 64b on the adjustment nut 60 side. (C) When the drum brake 10 is not braked, the first lever portion 64b of the lever member 64 is provided with a second strut. The second lever portion 64c is clamped between the member 58 and the adjusting nut 60, and the second lever portion 64c is adjusted in the direction in which the engaging portion 54c is separated from the star wheel 60a (the direction opposite to the arrow F direction). (D) when the drum brake 10 is braked, the second lever according to the biasing force of the adjusting lever 54 according to the separation between the second strut member 58 and the adjusting nut 60. The tip of the portion 64c is brought close to the second strut member 58, and the engaging portion 54c of the adjusting lever 54 rotates the star wheel 60a in one direction. As a result, the lever member 64 has the first strut member 56 and the second strut member at the time of braking of the drum brake 10 by the notch 68 notched at the tip of the first lever portion 64b on the adjustment nut 60 side. The amount by which the tip of the second lever portion 64 c approaches the second strut member 58 can be increased in conjunction with the relative movement in the direction of the axis C between the first notch 68 and the width E of the notch 68. The amount of movement of the engaging portion 54c of the adjusting lever 54 that is interlocked with the relative movement in the direction of the axis C between the strut member 56 and the second strut member 58 can be increased. Therefore, by providing the notch 68 in the lever member 64, the amount of movement of the engaging portion 54c of the adjusting lever 54 during braking of the drum brake 10 can be easily adjusted.

  Further, according to the drum brake 10 having the shoe gap automatic adjusting mechanism 26 of the present embodiment, the first strut member 56 is engaged with the adjustment nut 60 at the tip end portion of the adjustment lever 54 and the second strut member 58 is engaged. Since the stopper portion 54e is provided to prevent the shoe gap from falling off, when the shoe gap automatic adjusting mechanism 26 is assembled to the drum brake 10 by the stopper portion 54e, the first strut is formed by the coiled spring (elastic member) 62. Since the member 56 and the second strut member 58 are separated from each other and the first strut member 56 is prevented from dropping from the second strut member 58, the assembly process of the drum brake 10 can be facilitated.

  Further, according to the drum brake 10 provided with the shoe gap automatic adjusting mechanism 26 of the present embodiment, the star wheel is located at the tip of the adjusting lever 54 on the opposite side of the engaging portion 54c with the star wheel 60a interposed therebetween. A sliding contact engaging portion 54d that is brought into sliding contact with the outer peripheral teeth of 60a is provided, and the engaging portion 54c of the adjusting lever 54 moves on the outer peripheral teeth of the star wheel 60a when the drum brake 10 is braked and not braked. However, since the star wheel 60a is sandwiched between the sliding contact portion 54d and the engagement portion 54c, the star wheel 60a rotates together with the movement of the adjusting lever 54 when the drum brake 10 is braked or not. It is prevented.

  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 having the shoe gap automatic adjusting mechanism 26 of the present invention, the coil-shaped spring 62 is provided in the receiving hole 58a of the second strut member 58, but the receiving hole 58a is provided with the coiled spring 62. It is not limited to a spring, and any elastic member that separates the first strut member 56 and the second strut 58, such as a leaf spring, may be used.

  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. FIG. 3 is an enlarged view seen from the direction of arrow A in FIG. 2 for explaining an adjusting lever of a shoe gap automatic adjusting mechanism. FIG. 4 is a sectional view taken along line IV-IV in FIG. 2. It is a figure for demonstrating the state at the time of drum brake braking of the lever member by the urging | biasing force of an adjusting lever, and the time of non-braking. FIG. 6 is a sectional view taken along line VI-VI in FIG. 2. It is an enlarged view of the lever member of FIG. It is VIII-VIII sectional view taken on the line of (b) of FIG.

Explanation of symbols

10: Drum brakes 18, 20: A pair of brake shoes 26: Automatic shoe clearance adjustment mechanism 52: Strut 54: Adjustment lever 54a: Base end portion 54c: Engaging portion 54d: Sliding contact engaging portion 54e: Stopper portion 56: First 1 strut member 56a: screw portion 58: second strut member 58a: receiving hole 58e: fitting groove 60: adjusting nut 60a: star wheel 62: coiled spring (elastic member)
64: Lever member 64a: Insertion hole 64b: First lever portion 64c: Second lever portion 68: Notch

Claims (6)

A first strut member having a screw portion at one end and the other end engaging with one of the pair of brake shoes, a receiving hole opening at one end for receiving the screw portion of the first strut member, and the other end A pair of brake shoes that is engaged with the other of the pair of brake shoes, and an adjustment nut that includes a star wheel and that engages with a screw portion of the first strut member. Struts that define the spacing of
An engagement portion that is engaged with the star wheel is provided at a distal end portion, a proximal end portion is attached to the second strut member, and an axis between the first strut member and the second strut member at the time of braking. In a drum brake having a shoe gap automatic adjusting mechanism having an adjustment lever for rotating the star wheel in one direction in conjunction with relative movement in a direction,
A drum brake provided with an automatic shoe clearance adjustment mechanism, wherein an elastic member for urging the first strut member and the second strut member in a separating direction is provided in the receiving hole. A first lever portion that has an insertion hole into which the screw portion is inserted, and is sandwiched between the adjustment nut and the second strut member; and is bent at a predetermined angle greater than a right angle with respect to the first lever member. A lever member having a second lever portion;
The first lever portion is cut out at a tip portion of the first lever portion on the adjustment nut side,
At the time of non-braking, the first lever portion of the lever member is clamped between the second strut member and the adjustment nut, and the second lever portion moves the engagement portion away from the star wheel. The adjustment lever is pushed and bent against its biasing force,
At the time of braking, the second lever portion is brought close to the second strut member according to the biasing force of the adjustment lever according to the separation between the second strut member and the adjustment nut, and the engaging portion of the adjustment lever is set to the star lever. 2. A drum brake having an automatic shoe clearance adjusting mechanism according to claim 1, wherein the wheel is rotated in one direction.   3. A stopper portion that engages with the adjustment nut and prevents the first strut member from dropping off from the second strut member is provided at a tip portion of the adjustment lever. Drum brake with automatic shoe clearance adjustment mechanism.   The tip of the adjusting lever is provided with a sliding contact portion that is located on the opposite side to the engaging portion with the star wheel interposed therebetween and that is in sliding contact with the outer peripheral teeth of the star wheel. A drum brake comprising the shoe gap automatic adjusting mechanism according to any one of claims 1 to 3.   5. The shoe gap automatic adjusting mechanism according to claim 1, wherein a base end portion of the adjustment lever is fitted to the second strut member so as to hold the second strut member. Drum brake provided.   6. The shoe gap automatic adjusting mechanism according to claim 1, further comprising a fitting groove for fitting the base end portion at a predetermined position of the second strut member. Drum brake.

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