JP6013017B2 - Drum brake with shoe clearance automatic adjustment mechanism - Google Patents

Description

  The present invention relates to a drum brake having a shoe gap automatic adjusting mechanism, and more particularly to a technique for improving the reliability of a shoe gap automatic adjusting function in the shoe gap automatic adjusting mechanism.

  In general, a drum brake includes (a) a first strut member that engages with one end of a pair of expandable brake shoes, and a first strut member that engages with the other end of the pair of brake shoes. Two strut members and an adjusting wheel disposed between the first strut member and the second strut member and extending the distance between the first strut member and the second strut member by being rotated. A strut that defines a standby position of the pair of brake shoes during non-braking, and (b) a lever portion that engages with the adjusting wheel, and is rotatable to one of the pair of brake shoes. The adjusting wheel is provided by the lever portion in relation to the separation operation between the first strut member and one of the brake shoes. (C) the adjusting wheel is rotated by the adjusting lever to automatically adjust the shoe clearance between the pair of brake shoes and the rotating drum during non-braking. Some have a shoe gap automatic adjustment mechanism that adjusts automatically.

  In the drum brake having the shoe gap automatic adjusting mechanism as described above, the temperature of the rotating drum rises due to frictional heat between the pair of brake shoes and the rotating drum when the drum brake is braked. The inner diameter may increase. When the shoe gap is adjusted by the shoe gap automatic adjustment mechanism when the inner diameter of the rotating drum is expanded by this frictional heat, over adjustment occurs where the shoe gap becomes too small when the temperature returns to room temperature. For example, in the drum brakes disclosed in Patent Documents 1 to 3, in order to automatically suppress the over-adjustment, a feeling of being constituted by a bimetal that is deformed by a temperature rise due to frictional heat and suppresses the operation of the shoe gap automatic adjustment mechanism. A temperature deformation member is provided.

JP 2003-21180 A JP 2002-115733 A JP 2002-48172 A

  However, in the drum brake having the shoe gap automatic adjusting mechanism including the temperature-sensitive deforming member as described above, the temperature-sensitive deforming member is deformed when the temperature rises to a predetermined temperature, that is, an operation start temperature or more due to frictional heat. Suppresses the operation of the automatic gap adjustment mechanism, but may also be deformed by changes in environmental temperature such as seasonal changes. For example, if the operation start temperature of the temperature-sensitive deformation member is set to 40 ° C., in the summer in a high temperature region, the temperature-sensitive deformation member is deformed even when the drum brake does not generate heat due to braking, and the shoe clearance automatic is always automatic. There is a problem that the operation of the adjusting mechanism is suppressed. In addition, when a temperature-sensitive deformation member having a relatively high operation start temperature is used, in the winter in a cold region, even if high-load braking is performed many times, the operation start temperature of the temperature-sensitive deformation member is not reached and the shoe gap The operation of the automatic adjustment mechanism cannot be suppressed. For this reason, there is a possibility that dragging occurs between the pair of brake shoes and the rotary drum due to over-adjustment by the shoe gap automatic adjusting mechanism.

  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 is not easily affected by changes in environmental temperature.

To achieve this object, the gist of the present invention is that: (a) a first strut member that engages with one end portion of a pair of expandable brake shoes, and the other of the pair of brake shoes. A second strut member that engages one end, and a distance between the first strut member and the second strut member that is disposed between the first strut member and the second strut member and rotated. A strut that defines a standby position of the pair of brake shoes during non-braking, and (b) the first strut member or the second strut member and one of the brake shoes. An adjusting member for rotating the adjusting wheel in one direction in relation to the separation operation between the adjusting wheel and (c) the adjusting member by the adjusting member. A drum brake having a shoe gap automatic adjusting mechanism that automatically adjusts a shoe gap between the pair of brake shoes and the rotating drum when the braking wheel is rotated, when the braking wheel is rotated, and (d) The strut includes a first temperature-sensitive deformation member that suppresses the separation of the first strut member or the second strut member from one of the brake shoes due to deformation accompanying a rise in temperature, and a first temperature sense due to temperature rise. A second temperature-sensitive deformable member that deforms to a side that suppresses deformation of the deformable member, and (e) the first temperature-sensitive deformable member is closer to the first strut member side than the second temperature-sensitive deformable member or The first strut member or the second strut member is provided on the second strut member side, and ( f ) the first temperature-sensitive deformation member and the second strut member . The separation of the first strut member or the second strut member from one of the brake shoes is suppressed based on the temperature difference with the temperature-sensitive deformation member.

According to the drum brake provided with the shoe gap automatic adjusting mechanism of the present invention, the strut is restrained from being separated from one of the brake shoes by the deformation of the first strut member or the second strut member due to a temperature rise. A first temperature-sensitive deformable member, and a second temperature-sensitive deformable member that deforms to a side that suppresses deformation of the first temperature-sensitive deformable member due to a temperature rise . 2 provided on the first strut member or the second strut member so as to be closer to the first strut member or the second strut member than the temperature-sensitive deformable member, The separation of the first strut member or the second strut member from one of the brake shoes is suppressed based on the temperature difference with the second temperature-sensitive deformation member. For this reason, if the first temperature-sensitive deformable member is deformed by the environmental temperature, the second temperature-sensitive deformable member is deformed by the environmental temperature so as to suppress the deformation of the first temperature-sensitive deformable member. 1 Deformation of the temperature sensitive deformation member is suppressed. Further, the first temperature-sensitive deformable member is disposed on the first strut member or the second strut member so that the first temperature-sensitive deformable member is closer to the first strut member side or the second strut member side than the second temperature-sensitive deformable member. Therefore, the amount of frictional heat transmitted during braking from the first strut member or the second strut member to the second temperature-sensitive deformable member is smaller than that of the first temperature-sensitive deformable member. Thus, the temperature of the second temperature-sensitive deformable member is lower than that of the first temperature-sensitive deformable member. For this reason, when a transient temperature difference occurs between the first temperature-sensitive deformable member and the second temperature-sensitive deformable member due to frictional heat during braking, the first temperature-sensitive deformable member is moved to the second temperature-sensitive deformable member. The first strut member or the second strut member is deformed against the deformable member, and the separation of the first strut member or the second strut member from one of the brake shoes is suppressed. As a result, the shoe gap automatic adjustment mechanism is not easily affected by changes in the environmental temperature, and over-adjustment is suitably prevented by the temperature rise due to the frictional heat.

  Here, preferably, the second temperature-sensitive deformable member is provided on the first strut member or the second strut member via a low heat conductive member having a lower thermal conductivity than the strut. For this reason, when frictional heat is transmitted to the first temperature-sensitive deformable member and the second temperature-sensitive deformable member, a temperature is transiently generated between the first temperature-sensitive deformable member and the second temperature-sensitive deformable member. The difference is preferably large, and over-adjustment is prevented.

  Preferably, the second temperature-sensitive deformable member has a contact area reduction that relatively reduces the contact area with the first strut member or the second strut member to which the second temperature-sensitive deformable member is attached. The part is formed. For this reason, when frictional heat is transmitted to the first temperature-sensitive deformable member and the second temperature-sensitive deformable member, a temperature is transiently generated between the first temperature-sensitive deformable member and the second temperature-sensitive deformable member. The difference is preferably large, and over-adjustment is prevented.

  Preferably, the adjustment member has a lever portion that engages with the adjusting wheel and is rotatably provided on one of the pair of brake shoes. The same effect as that of the first aspect of the invention can be obtained even with such an automatic shoe clearance adjusting mechanism having the adjusting member.

  Preferably, the adjusting member has a lever portion that engages with the adjusting wheel, and the strut is provided in a state in which the lever portion is urged toward the adjusting wheel. The same effect as that of the first aspect of the invention can be obtained even with such an automatic shoe clearance adjusting mechanism having the adjusting member.

It is a front view showing the whole drum brake composition provided with the shoe gap automatic adjustment mechanism of one example of the present invention. FIG. 2 is a cross-sectional view taken along the line II-II in FIG. 1, illustrating a configuration of a shoe gap automatic adjusting mechanism in FIG. 1. It is a perspective view which shows the 1st temperature-sensitive deformation member and 2nd temperature-sensitive deformation member of the III arrow view of FIG. FIG. 3 is a cross-sectional view showing a state of the first temperature-sensitive deformable member and the second temperature-sensitive deformable member when the drum brake of FIG. 1 is used at a relatively low environmental temperature such as winter in a cold region. FIG. 3 is a cross-sectional view showing a state of the first temperature-sensitive deformation member and the second temperature-sensitive deformation member when the drum brake of FIG. 1 is used at a relatively high environmental temperature such as summer in a high-temperature region. It is a figure explaining the drum brake of the other Example of this invention. FIG. 7 is a VII-VII view of FIG. 6. FIG. 7 is a cross-sectional view showing a state of the first temperature-sensitive deformation member and the second temperature-sensitive deformation member when the drum brake of FIG. 6 is used at a relatively low environmental temperature such as winter in a cold region, for example. It is a figure corresponding to. FIG. 7 is a cross-sectional view showing a state of the first temperature-sensitive deformable member and the second temperature-sensitive deformable member when the drum brake of FIG. 6 is used at a relatively high environmental temperature such as summer in a high temperature region, for example. It is a figure corresponding to. It is a figure explaining the drum brake of the other Example of this invention. It is XI-XI sectional view taken on the line of FIG. It is a figure explaining the drum brake of the other Example of this invention. It is the enlarged view to which the 2nd temperature sensitive deformation member with which the drum brake of FIG. 12 was equipped was expanded. It is a XIV-XIV view of FIG. It is a figure explaining the drum brake of the other Example of this invention. FIG. 16 is a sectional view taken along line XVI-XVI in FIG. 15. It is the XVII-XVII sectional view taken on the line of FIG. It is a figure explaining the drum brake of the other Example of this invention. It is a figure which shows the fixing | fixed part of the 2nd temperature sensitive deformation member of XIX arrow of FIG. It is a figure explaining the fixing | fixed part of the 2nd temperature sensitive deformation member of the other Example of this invention. It is a XXI-XXI view of FIG.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In the following embodiments, the drawings are appropriately simplified or modified for easy understanding, and the dimensional ratios, shapes, and the like of the respective parts 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 (rotary drum) 12. FIG. 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.

  As shown in FIG. 1, the drum brake 10 has a substantially disk shape, and is, for example, a backing integrally fixed to a vehicle body side member, that is, a non-rotating member such as an axle tube, an axle housing, and a suspension device (not shown). A plate 16 is provided.

  As shown in FIG. 1, the drum brake 10 has 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 where the convex side is on the outer side of the backing plate 16. 1 and the one end of the pair of brake shoes 18 and 20, that is, the wheel cylinder 22 fixed to the backing plate 16 between the upper ends of FIG. 1 and the one end of the pair of brake shoes 18 and 20 approach each other. In order to always urge in the direction of the movement, a coiled return spring 24 stretched between the one ends, and one end of the pair of brake shoes 18 and 20 so as to pass through the inside of the coiled return spring 24 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 in contact with the anchor 28.

  Each of the pair of brake shoes 18 and 20 has a flat plate shape substantially parallel to the flat plate portion 16a of the backing plate 16, and the shoe web is punched into a shape curved in an arc shape in the front view shown in FIG. 32 and 34, band plate-like shoe rims 36 and 38 integrally fixed so that a cross-section thereof is substantially T-shaped along an outer peripheral side edge forming an arc shape thereof, and the shoe rims 36 and 38 And linings 40 and 42 made of a friction material that are integrally fixed to the outer peripheral surface of each of them with an adhesive or the like.

  The pair of brake shoes 18 and 20 are pressed toward the backing plate 16 by shoe hold-down devices 44 and 46 disposed on the shoe web 32 and the shoe web 34, respectively. It is held relative to each other. As shown in FIG. 1, a base end portion 48 a of a longitudinal 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 parking brake lever 48 has a leading end 48b formed with a protruding portion 48c that protrudes integrally from the leading end 48b in a direction approaching the inner peripheral surface of the shoe rim 36 and contacts the inner peripheral surface of the shoe rim 36.

  As shown in FIG. 2, the shoe gap automatic adjustment mechanism 26 is spanned between one end portions of the pair of brake shoes 18 and 20, and approaches the pair of brake shoes 18 and 20 when the drum brake 10 is not braked. And a strut 52 for defining the standby position thereof, and an adjustment lever (adjusting member) 54 provided in the strut 52 is provided.

  As shown in FIG. 2, the strut 52 includes a longitudinal first strut member 56 having a first engaging portion 56 a that engages with one end portion of the shoe web 34, one end portion of the shoe web 32, and a parking brake lever 48. A second strut member 58 having a second engaging portion 58a that engages with the base end portion 48a, and the second strut member 58 and the first strut member 56 disposed between the second strut member 58 and the first strut member 56. The adjustment shaft 60 having a longitudinal shape to be combined, and the first engagement portion 56a of the first strut member 56 of the adjustment shaft 60 and the second engagement portion 58a of the second strut member 58 are fixed to the adjustment shaft. And a substantially disc-shaped adjusting wheel 60 a having a larger diameter than the diameter of 60.

  As shown in FIG. 2, the second engaging portion 58a of the second strut member 58 is cut out in a rectangular shape so that one end of the shoe web 32 and the base end 48a of the parking brake lever 48 are fitted therein. A notch 58b is formed.

  In the strut 52, a part of the inner peripheral side end surface 48 d in the base end portion 48 a of the parking brake lever 48 is formed by the notch 58 b in the second engaging portion 58 a of the second strut member 58 due to the urging force of the return spring 24. A pair of brake shoes when the drum brake 10 is not braked is brought into contact with the contact surface 58 c and one end portion of the shoe web 34 is contacted with the first engagement portion 56 a of the first strut member 56. 18 and 20 standby positions are defined.

  As shown in FIG. 2, the adjusting shaft 60 includes a fitting shaft portion 60 b that protrudes in a substantially cylindrical shape from the center portion of the substantially disc-shaped adjusting wheel 60 a toward the brake shoe 20, and a substantially disc shape. And a screw shaft portion 60d having a male thread portion 60c threaded on the outer peripheral surface thereof, which protrudes from the center portion of the adjusting wheel 60a in a substantially cylindrical shape in the opposite direction to the fitting shaft portion 60b. Yes. In the adjustment shaft 60, the screw shaft portion 60 d is screwed into a female screw hole 58 d formed in the second strut member 58, and the fitting shaft portion 60 b is a substantially cylindrical fitting hole 56 b formed in the first strut member 56. Are fitted in such a manner that they can rotate relative to each other.

  Therefore, when the adjusting wheel 60a is rotated by the adjusting lever 54 in a predetermined direction, for example, when the screw shaft portion 60d of the adjustment shaft 60 is a right-hand screw, the strut 52 is rotated in the counterclockwise direction. The second strut member 58 is moved away from the first strut member 56 by the action of the male screw formed at 60d and the female screw formed at the inner periphery of the female screw hole 58d of the second strut member 58. Thus, the distance between the first engaging portion 56a of the first strut member 56 and the second engaging portion 58a of the second strut member 58, that is, the distance in the longitudinal direction of the strut 52 is extended.

  The adjusting lever 54 is formed by pressing from a steel plate, for example. As shown in FIG. 1, the adjustment lever 54 is a substantially cylindrical shaft that protrudes from the shoe web 34 in a direction approaching the backing plate 16 in a through hole 54 b that penetrates the base end portion 54 a of the adjustment lever 54. The member 62 is fitted so as to be relatively rotatable. For this reason, the adjusting lever 54 is disposed on the shoe web 34 of the brake shoe 20 so as to be rotatable around the axis of the shaft member 62.

  As shown in FIGS. 1 and 2, the adjusting lever 54 has a lever portion 54c extending in a longitudinal direction from the base end portion 54a in a direction approaching the adjusting wheel 60a, and a substantially circular shape from the distal end portion of the lever portion 54c. A plate-shaped adjusting wheel 60a that extends to one of a plurality of engaging teeth provided on the outer peripheral surface of the adjusting wheel 60a and engages with the engaging teeth when the drum brake 10 is braked by operating a brake pedal (not shown). The engagement plate 54d and a contact that extends from the intermediate portion of the lever portion 54c in a direction approaching the first engagement portion 56a of the first strut member 56 and contacts the first engagement portion 56a of the first strut member 56 The unit 54e is integrally provided. As shown in FIG. 1, the adjustment lever 54 is always urged so as to rotate in the direction of the arrow F around the axis of the shaft member 62, and the intermediate portion of the lever portion 54c and the brake shoe are provided. A coiled spring 64 is provided between the other end of the coil 20. For this reason, the contact portion 54e of the adjustment lever 54 constantly urges the first strut member 56, that is, the strut 52 toward the brake shoes 18 of the pair of brake shoes 18 and 20 by the urging force of the coiled spring 64. Yes. The biasing force of the coiled spring 64 is smaller than the biasing force of the return spring 24.

  As shown in FIGS. 2 to 5, at the end of the strut 52 on the brake shoe 18 side, a first temperature-sensitive deformation member that suppresses the separation of the first strut member 56 from the brake shoe 20 due to deformation accompanying a rise in temperature. 66, and a second temperature-sensitive deformation member 68 that is deformed to a side that suppresses deformation of the first temperature-sensitive deformation member 66 due to a temperature rise.

  As shown in FIGS. 3 to 5, the first temperature-sensitive deformation member 66 includes a flat plate-like fixing portion 66 a fixed to the second engaging portion 58 a of the second strut member 58, and a parking brake lever at the tip portion. A long flat plate-shaped engaging portion 66b that engages with a part of the inner peripheral side end surface 48d of the base end portion 48a of the 48, and a connection that is bent in an arc shape that connects the engaging portion 66b and the fixing portion 66a. The portion 66c is integrally provided. As shown in FIG. 3, the engaging portion 66 b of the first temperature-sensitive deformation member 66 has the tip end portion of the engaging portion 66 b branched into two on both sides of the second engaging portion 58 a of the second strut member 58. The distal end of each engaging portion 66b is engaged with a part of the inner peripheral side end surface 48d of the base end portion 48a of the brake lever 48.

  As shown in FIGS. 3 to 5, the second temperature-sensitive deformation member 68 has a flat plate-shaped fixing portion 68 a fixed to a fixing portion 66 a of the first temperature-sensitive deformation member 66 via a low heat conduction member 70 described later. And a long flat plate-shaped engaging portion 68b that engages with a part of the engaging portion 66b of the first temperature-sensitive deformable member, and a circular arc shape that connects the engaging portion 68b and the fixing portion 68a. The formed connecting portion 68c is integrally provided. As shown in FIG. 3, the engaging portion 68 b of the second temperature-sensitive deformable member 68 has a distal end portion of the engaging portion 68 b branched into two on both sides of the second engaging portion 58 a of the second strut member 58. The tip of each engaging portion 68b is engaged with a part of the engaging portion 66b of the first temperature-sensitive deformation member 66. Further, an insertion hole 68d is formed in the connecting portion 68c of the second temperature-sensitive deformable member 68 so as to pass through the connecting portion 66c of the first temperature-sensitive deformable member 66.

  As shown in FIGS. 3 to 5, the second temperature-sensitive deformation member 68 includes a flat plate-shaped low heat conductive member 70 having a lower thermal conductivity than the strut 52, that is, the second strut member 58 and the first temperature-sensitive deformation member 66. The first temperature-sensitive deformation member 66 is provided on the fixing portion 66 a, that is, the second engaging portion 58 a of the second strut portion 58. Further, the fixing portion 66a of the first temperature-sensitive deformation member 66, the fixing portion 68a of the second temperature-sensitive deformation member 68, and the low heat conduction member 70 protrude from the second engaging portion 58a of the second strut member 58, respectively. Insertion holes 66d, 68e, and 70a through which the protrusions 58e are inserted are formed, and the tip portions of the protrusions 58e are caulked and deformed, whereby the fixing portions 66a and the second temperature sensitive members of the first temperature-sensitive deformation members 66 are formed. The fixed portion 68a of the deformable member 68 and the low heat conductive member 70 are fixed to the second engaging portion 58a of the second strut member.

  The first temperature-sensitive deformable member 66 and the second temperature-sensitive deformable member 68 are so-called bimetals joined together by high pressure by rolling or the like in a state where two thin plates having different thermal expansion coefficients are combined. In this embodiment, a member having a relatively high coefficient of thermal expansion is used for the outer peripheral portion A of the first temperature-sensitive deformable member 66, and a coefficient of thermal expansion is relatively set for the inner peripheral portion B of the first temperature-sensitive deformable member 66. Low parts are used. For this reason, in the first temperature-sensitive deformation member 66, when the temperature rises, the distal end portion of the engaging portion 66b of the temperature-sensitive deformation member 66 is in the direction in which the strut 52 is separated from the inner peripheral side end surface 48d of the parking brake lever 48. 3 is bent in the direction of arrow F1. That is, the first temperature-sensitive deformation member 66 is deformed so as to separate the second engagement portion 58 a of the second strut member 58 and the base end portion 48 a of the parking brake lever 48. Further, a member having a relatively low coefficient of thermal expansion is used for the outer peripheral portion C of the second temperature-sensitive deformable member 68, and a member having a relatively high coefficient of thermal expansion is used for the inner peripheral portion D of the second temperature-sensitive deformable member 68. I am using it. Therefore, the second temperature-sensitive deformation member 68 is bent in the direction opposite to the arrow F1, that is, the arrow F2 direction shown in FIG. It is done. That is, the second temperature-sensitive deformation member 68 is deformed to the side that suppresses the deformation of the first temperature-sensitive deformation member 66 due to the temperature rise.

  If the first temperature-sensitive deformation member 66 and the second temperature-sensitive deformation member 68 have the same temperature, the force that presses the engaging portion 68b in the direction of the arrow F1 and the engaging portion 66b in the direction of the arrow F2 The power to do is the same. Further, when the temperature of the second temperature-sensitive deformation member 68 becomes relatively lower than the temperature of the first temperature-sensitive deformation member 66, the temperature difference between the first temperature-sensitive deformation member 66 and the second temperature-sensitive deformation member 68 is caused. As shown in the right diagram of FIG. 4 and the right diagram of FIG. 5, the force that presses the parking brake lever 48 and the brake shoe 18 to the outer peripheral side of the backing plate 16 by the engaging portion 66 b of the first temperature-sensitive deformation member 66, The force which presses the strut 52 to the brake shoe 20 side of a pair of brake shoes 18 and 20 becomes large.

  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 the wheel cylinder 22 in accordance with a brake pedal operation (not shown). Then, in a state where the linings 40 and 42 are worn and the shoe gap is increased, the pair of brake shoes 18 and 20 are expanded from the standby position by the wheel cylinder 22, and the strut 52 is brought into contact with the contact portion 54e of the adjustment lever 54. When the pair of brake shoes 18 and 20 are moved to the brake shoe 18 side, the adjusting wheel 54d is formed by the engagement plate 54d formed at the tip of the lever portion 54c according to the distance between the first strut member 56 and the brake shoe 20. If 60a is a predetermined direction, for example, if the screw shaft portion 60d of the adjustment shaft 60 is a right-hand thread, the adjustment shaft 60 is rotated counterclockwise. Thereby, the strut 52 is extended and the shoe gap is adjusted.

  The operation of the automatic shoe clearance adjustment mechanism 26 when the drum brake 10 is used at a relatively low ambient temperature such as in a cold region or at a relatively high ambient temperature such as in a high temperature region is illustrated. 4 and FIG. FIG. 4 is a diagram showing a state of the first temperature-sensitive deformation member 66 and the second temperature-sensitive deformation member 68 when the drum brake 10 is used at a relatively low environmental temperature such as winter in a cold region. is there. 4 shows a case where the temperature increase of the brake shoes 18 and 20 due to the brake operation is small while the vehicle is traveling, and the right diagram of FIG. 4 shows the brake accompanying the brake operation while the vehicle is traveling. This shows a case where the temperature rise of the shoes 18 and 20 is large. FIG. 5 is a diagram showing a state of the first temperature-sensitive deformation member 66 and the second temperature-sensitive deformation member 68 when the drum brake 10 is used at a relatively high environmental temperature such as summer in a high temperature region. is there. 5 shows a case where the temperature rise of the brake shoes 18 and 20 due to the brake operation is small while the vehicle is traveling, and the right diagram of FIG. 5 shows the brake accompanying the brake operation while the vehicle is traveling. This shows a case where the temperature rise of the shoes 18 and 20 is large.

  As shown in the left diagram of FIG. 4 and the left diagram of FIG. 5, the drum brake 10 is used at a relatively low environmental temperature such as winter in a cold region and a relatively high environmental temperature such as summer in a high temperature region. However, when the temperature increase of the brake shoes 18 and 20 due to the brake operation is small during traveling of the vehicle, the amount of frictional heat transmitted to the first temperature-sensitive deformation member 66 and the second temperature-sensitive deformation member 68 is small. For this reason, the temperature of the first temperature-sensitive deformation member 66 and the second temperature-sensitive deformation member 68 is substantially the same as the relatively low temperature or relatively high temperature environment temperature, that is, the temperature of the outside air (air). The first temperature-sensitive deformation member 66 tries to push the parking brake lever 48 in the direction of arrow F1, but the force that the second temperature-sensitive deformation member 68 tries to push in the direction of arrow F1 in the direction of arrow F2 due to the environmental temperature. Therefore, the displacement of the engaging portion 66b of the first temperature-sensitive deformation member 66 in the direction of arrow F1, that is, the deformation is suppressed. For this reason, the strut 52 is not biased to the brake shoe 20 side of the pair of brake shoes 18 and 20 by the engaging portion 66b of the first temperature-sensitive deformation member 66 during braking. 26 is activated to adjust the shoe clearance as described above.

  As shown in the right figure of FIG. 4 and the right figure of FIG. 5, the brake operation is performed while the vehicle is running at a relatively low environmental temperature such as winter in a cold region and a relatively high environmental temperature such as summer in a high temperature region. When the amount of frictional heat is relatively large, the amount of frictional heat that is transiently transmitted to the second temperature-sensitive deformation member 68 is compared with that of the first temperature-sensitive deformation member 66 by the low heat conductive member 70. Therefore, the temperature of the second temperature-sensitive deformation member 68 is lower than the temperature of the first temperature-sensitive deformation member 66. The first temperature sensing deformation member 66 pushes the parking brake lever 48 and the brake shoe 18 in the direction of arrow F1 and exceeds the force pushing the second temperature sensing deformation member 68 in the direction of arrow F2. The difference between the pushing force of the engaging portion 66b of 66 and the pushing force of the engaging portion 68b of the second temperature-sensitive deformation member 68 becomes the force that pushes the parking brake lever 48 in the direction of arrow F1. For this reason, when the engaging portion 66b of the first temperature-sensitive deformable member 66 is deformed against the engaging portion 68b of the second temperature-sensitive deformable member 68, the strut 52 becomes the brake shoe 20 side of the pair of brake shoes 18 and 20. Since the first strut member 56 and the brake shoe 20 are brought into contact with each other, the separation of the first strut member 56 from the brake shoe 20 is suppressed during overheating. As a result, when the temperature of the brake drum 12 rises due to frictional heat and the inner diameter of the brake drum 12 increases, the adjustment lever 54 does not rotate, so the shoe gap of the shoe gap automatic adjustment mechanism 26 is automatically adjusted. Regulation is suppressed.

  According to the drum brake 10 provided with the shoe gap automatic adjusting mechanism 26 of the present embodiment, the first strut member 56 is prevented from being separated from the brake shoe 20 at the end portion of the strut 52 by deformation caused by temperature rise. A first temperature-sensitive deformation member 66, and a second temperature-sensitive deformation member 68 that is deformed to a side that suppresses deformation of the first temperature-sensitive deformation member 66 due to a temperature rise. The separation of the first strut member 56 from the brake shoe 20 is suppressed based on the temperature difference with the second temperature-sensitive deformation member 68. For this reason, for example, if the first temperature-sensitive deformation member 66 is deformed by an environmental temperature such as winter in a cold region or summer in a high-temperature region, the second temperature-sensitive deformation member 68 deforms the first temperature-sensitive deformation member 66. Since it deform | transforms into the suppression side, a deformation | transformation of the 1st temperature sensitive deformation member 66 is suppressed. However, if a temperature difference occurs transiently between the first temperature-sensitive deformable member 66 and the second temperature-sensitive deformable member 68 due to frictional heat during braking, the first temperature-sensitive deformable member 66 becomes the second temperature-sensitive deformable member. The first strut member 56 is deformed against 68 and the separation of the first strut member 56 from the brake shoe 20 is suppressed. As a result, the shoe gap automatic adjustment mechanism 26 is not easily affected by changes in the environmental temperature, and over-adjustment is suitably prevented by the temperature rise due to the frictional heat.

  Further, according to the drum brake 10 provided with the shoe gap automatic adjusting mechanism 26 of the present embodiment, the second temperature-sensitive deformation member 68 has a low thermal conductivity lower than that of the strut 52 and the first temperature-sensitive deformation member 66. A second engaging portion 58 a of the second strut member 58 is provided via the member 70. For this reason, when frictional heat is transmitted to the first temperature-sensitive deformation member 66 and the second temperature-sensitive deformation member 68, the temperature between the first temperature-sensitive deformation member 66 and the second temperature-sensitive deformation member 68 is transitively. The difference is preferably large, and over-adjustment is prevented.

  Further, according to the drum brake 10 having the shoe gap automatic adjusting mechanism 26 of the present embodiment, the adjusting lever 54 has a lever portion 54c that engages with the adjusting wheel 60a and is provided rotatably on the brake shoe 20. It has been.

  Next, another preferred embodiment of the present invention will be described in detail with reference to the drawings. In the following description, parts common to the embodiments are denoted by the same reference numerals and description thereof is omitted.

  As shown in FIG. 6, the drum brake having the shoe gap automatic adjusting mechanism of the present embodiment is not provided with the low heat conductive member 70 of the first embodiment, and the second temperature-sensitive deformation member 72 is fixed. The shape of the part 72a is different from that of the fixing part 68a of the second temperature-sensitive deformation member 68 of the first embodiment described above, and is otherwise configured in substantially the same manner.

  As shown in FIG. 6, the second temperature-sensitive deformable member 72 is deformed to the side that suppresses the deformation of the first temperature-sensitive deformable member 66 due to a temperature rise, as in the first embodiment. The second temperature-sensitive deformation member 72 includes a flat plate-shaped fixing portion (contact area reducing portion) 72a that is directly fixed to the fixing portion 66a of the first temperature-sensitive deformation member 66, and the engaging portion 68b of the first embodiment. The same engaging portion 72b, a connecting portion 72c similar to the connecting portion 68c of the first embodiment, and an insertion hole 72d similar to the insertion hole 68d of the first embodiment are integrally provided.

  As shown in FIG. 7, the fixing portion 72a of the second temperature-sensitive deformation member 72 has a contact area with the fixing portion 66a of the first temperature-sensitive deformation member 66 to which the second temperature-sensitive deformation member 72 is attached. Compared to the fixed portion 66a of the second temperature-sensitive deformation member 68, it is reduced.

  Here, when the drum brake equipped with the shoe gap automatic adjustment mechanism of the present embodiment is used at a relatively low environmental temperature such as winter in a cold region or a relatively high temperature such as summer in a high temperature region. The operating state of the shoe clearance automatic adjusting mechanism 26 when used at ambient temperature will be described with reference to FIGS.

  As shown in the left figure of FIG. 8 and the left figure of FIG. 9, even if the drum brake of this embodiment is used at a relatively low environmental temperature such as a cold region or a relatively high environmental temperature such as a high temperature region. When the temperature of the brake shoes 18 and 20 accompanying the brake operation is small during vehicle travel, the amount of frictional heat transmitted to the first temperature-sensitive deformation member 66 and the second temperature-sensitive deformation member 72 is small. For this reason, the temperature of the first temperature-sensitive deformation member 66 and the second temperature-sensitive deformation member 68 is substantially the same as the relatively low temperature or relatively high temperature environment temperature, that is, the temperature of the outside air (air). The first temperature-sensitive deformation member 66 tries to push the parking brake lever 48 in the direction of arrow F1, but the force that the second temperature-sensitive deformation member 68 tries to push in the direction of arrow F1 in the direction of arrow F2 due to the environmental temperature. Therefore, the displacement of the engaging portion 66b of the first temperature-sensitive deformation member 66 in the direction of the arrow F1 is suppressed. For this reason, the strut 52 is not biased to the brake shoe 20 side of the pair of brake shoes 18 and 20 by the engaging portion 66b of the first temperature-sensitive deformation member 66 during braking. 26 is activated to adjust the shoe clearance as described above.

  As shown in the right diagram of FIG. 8 and the right diagram of FIG. 9, the brake operation is performed while the vehicle is running at a relatively low environmental temperature such as winter in a cold region and a relatively high environmental temperature such as summer in a high temperature region. When the amount of frictional heat is relatively large, the amount of frictional heat transmitted to the second temperature-sensitive deformation member 72 is transiently small in contact area with the first temperature-sensitive deformation member 66. The fixing portion 72a of the second temperature-sensitive deformation member 72, which is a contact area decreasing portion, is smaller than the first temperature-sensitive deformation member 66, and the temperature of the second temperature-sensitive deformation member 72 is lower than that of the first temperature-sensitive deformation member 66. Lower than temperature. The first temperature-sensitive deformation member 66 pushes the parking brake lever 48 and the brake shoe 18 in the direction of the arrow F1 and exceeds the force of the second temperature-sensitive deformation member 72 in the direction of the arrow F2. The difference between the pushing force of the engaging portion 66b and the pushing force of the engaging portion 72b of the second temperature-sensitive deformation member 72 is the force that pushes the parking brake lever 48 in the direction of the arrow F1. For this reason, when the engaging portion 66b of the first temperature-sensitive deformable member 66 is deformed against the engaging portion 72b of the second temperature-sensitive deformable member 72, the strut 52 becomes the brake shoe 20 side of the pair of brake shoes 18 and 20. Since the first strut member 56 and the brake shoe 20 are brought into contact with each other, the separation of the first strut member 56 from the brake shoe 20 is suppressed during overheating. As a result, when the temperature of the brake drum 12 rises due to frictional heat and the inner diameter of the brake drum 12 increases, the adjustment lever 54 does not rotate, so the shoe gap of the shoe gap automatic adjustment mechanism 26 is automatically adjusted. Adjustment is suppressed.

  According to the drum brake having the shoe gap automatic adjusting mechanism of the present embodiment, the second temperature sensitive deformable member 72 is fixed to the second strut member 58 to which the second temperature sensitive deformable member 72 is attached. A fixing portion 72a, which is a contact area reducing portion that reduces the contact area of the temperature-sensitive deformation member 66 with the fixing portion 66a as compared with the fixing portion 66a of the second temperature-sensitive deformation member 68 of the first embodiment, is formed. ing. For this reason, when frictional heat is transmitted to the first temperature-sensitive deformation member 66 and the second temperature-sensitive deformation member 72, the temperature is transitively between the first temperature-sensitive deformation member 66 and the second temperature-sensitive deformation member 72. The difference is preferably large, and over-adjustment is prevented.

  As shown in FIGS. 10 and 11, the drum brake 76 having the shoe gap automatic adjusting mechanism 74 of the present embodiment has a shoe gap automatic adjusting mechanism 74 different from the shoe gap automatic adjusting mechanism 26 of the first embodiment. It differs in the point provided, and other than that is comprised substantially the same.

  As shown in FIGS. 10 and 11, the shoe gap automatic adjustment mechanism 74 is spanned between one end portions of the pair of brake shoes 18 and 20, and the pair of brake shoes 18 and the brake shoe 18 when the drum brake 76 is not braked. There are provided struts 78 that prevent the approach of 20 and define their standby positions, and an adjustment lever (adjusting member) 80 provided on the struts 78.

  As shown in FIGS. 10 and 11, the strut 78 includes a longitudinal first strut member 82 having a first engaging portion 82 a that engages with one end of the brake shoe 20, one end of the shoe web 32, and A longitudinal second strut member 84 having a second engaging portion 84 a that engages with a base end portion 48 a of the parking brake lever 48, and the second engaging portion 84 a and the first strut member 82 of the second strut 84. An adjusting wheel 86 is provided between the first engaging portion 82a and is rotated to extend the distance between the first engaging portion 82a and the second engaging portion 84a. ing.

  The first strut member 82 includes a screw shaft portion 82c having a substantially cylindrical shape protruding from the first engagement portion 82a in a direction approaching the brake shoe 18 and having a male screw portion 82b threaded on the outer peripheral surface thereof. It has been. Further, an adjusting wheel 86 is screwed onto the screw shaft portion 82c of the first strut member 82, and the tip end portion of the screw shaft portion 82c is fitted in a substantially cylindrical shape provided on the second strut member 84. The holes 84b are fitted into the struts 78 so as to be relatively movable in the longitudinal direction.

  Therefore, when the adjusting wheel 86 is rotated in a predetermined direction by the adjusting lever 80, the strut 78 moves the adjusting wheel 86 toward the brake shoe 18 side of the pair of brake shoes 18 and 20, and will be described later. The second strut member 84 is moved away from the first strut member 82 via the first temperature-sensitive deformable member 90, the second temperature-sensitive deformable member 92, and the pair of low heat conductive members 94 and 96, and the first strut member The distance between the first engaging portion 82a of 82 and the second engaging portion 84a of the second strut member 84, that is, the longitudinal distance of the strut 78 is extended.

  As shown in FIGS. 10 and 11, the adjusting lever 80 includes a lever portion 80 a that engages with the adjusting wheel 86, and a coiled spring 88 that is stretched between the lever portion 80 a and the brake shoe 20. And a contact portion 80b that constantly abuts the strut 78 toward the brake shoe 18 side of the pair of brake shoes 18 and 20 by abutting against the first engaging portion 82a of the first strut member 82 by the urging force. . The adjusting lever 80 has a substantially columnar shaft member 81 projecting in a direction away from the backing plate 16 from the shoe web 34 in a through hole 80d penetrating the base end 80c of the adjusting lever 80. It is fitted as possible. Further, the urging force of the coiled spring 88 is smaller than the urging force of the return spring 24.

  As shown in FIGS. 10 and 11, the first feeling between the adjusting wheel 86 and the second strut member 84 is that the first strut member 82 is prevented from being separated from the brake shoe 20 due to the deformation caused by the temperature rise. A temperature-deformable member 90 and a second temperature-sensitive deformable member 92 that deforms to a side that suppresses deformation of the first temperature-sensitive deformable member 90 due to a temperature rise are provided.

  As shown in FIGS. 10 and 11, the first temperature-sensitive deformation member 90 includes flat plates facing each other and disposed between the adjusting wheel 86 and the end of the second strut member 84 on the brake shoe 20 side. A pair of side wall portions 90a and 90b having a shape and a connecting portion 90c bent in an arc shape that connects the end portions of the pair of side wall portions 90a and 90b on the backing plate 16 side are integrally provided. As shown in FIG. 11, the pair of side wall portions 90a and 90b have fitting holes 90d for fitting the screw shaft portions 82c of the first strut members 82 so as to be movable in the axial direction of the screw shaft portions 82b. Is formed. Further, the side wall portion 90 b is engaged with the adjusting wheel 86. As shown in FIG. 10, the side wall 90a is formed with a detent 90e integrally extending from a part of the side wall 90a toward the second strut member 84, and the detent 90e. Is fitted in a notch 84c formed at the end of the second strut member 84 on the brake shoe 20 side.

  As shown in FIGS. 10 and 11, the second temperature-sensitive deformation member 92 is attached between the side wall portion 90a of the first temperature-sensitive deformation member 90 and the end portion of the second strut member 84 on the brake shoe 20 side. The flat plate-shaped attachment portion 92a, the long flat plate-shaped engagement portion 92b whose front end portion engages with a part of the side wall portion 90b of the first temperature-sensitive deformation member 90, the engagement portion 92b, and the attachment portion 92a. Are integrally provided with a connecting portion 92c bent in an arc shape. As shown in FIG. 10, the engaging portion 92 b of the second temperature-sensitive deformation member 92 is such that the tip of the engaging portion 92 b branches into two on both sides of the adjusting wheel 86. The tip of the part 92 b is engaged with a part of the side wall part 90 b of the first temperature-sensitive deformation member 90. Further, a fitting hole 92d for fitting the screw shaft portion 82b of the first strut member 82 so as to be movable in the axial direction of the screw shaft portion 82b is formed in the attachment portion 92a of the second temperature-sensitive deformation member 92. Yes. Further, an insertion hole 92e is formed in the connection portion 92c of the second temperature-sensitive deformation member 92 so as to pass through the connection portion 90c of the first temperature-sensitive deformation member 90.

  As shown in FIGS. 10 and 11, the mounting portion 92 a of the second temperature-sensitive deformable member 92 has a flat plate shape having a thermal conductivity lower than that of the strut 78, that is, the second strut member 84 and the first temperature-sensitive deformable member 90. A pair of low thermal conductive members 94 and 96 are provided. The low heat conductive member 94 is disposed between the mounting portion 92a of the second temperature sensitive deformable member 92 and the end of the second strut member 84 on the brake shoe 20 side. It is disposed between the attachment portion 92 a of the temperature deformation member 92 and the side wall portion 90 a of the first temperature-sensitive deformation member 90. The pair of low heat conductive members 94 and 96 are formed with fitting holes 94a and 96a for fitting the screw shaft portion 82b of the first strut member 82 so as to be movable in the axial direction of the screw shaft portion 82b. . Further, as shown in FIG. 10, a notch 92f through which the rotation preventing portion 90e of the first temperature-sensitive deformation member 90 is inserted into the attachment portion 92a of the second temperature-sensitive deformation member 92 and the pair of low heat conduction members 94 and 96, respectively. , 94b, 96b are formed.

  The first temperature-sensitive deformable member 90 and the second temperature-sensitive deformable member 92 are so-called bimetals joined together by high pressure by rolling or the like in a state where two thin plates having different thermal expansion coefficients are combined. In the present embodiment, a member having a relatively low coefficient of thermal expansion is used for the outer peripheral portion of the first temperature-sensitive deformable member 90, and a member having a relatively high coefficient of thermal expansion is used for the inner peripheral portion of the first temperature-sensitive deformable member 90. Is used. For this reason, the first temperature-sensitive deformation member 90 is deformed in a direction in which the tip portions of the pair of side wall portions 90a and 90b of the first temperature-sensitive deformation member 90 are separated from each other as the temperature rises. That is, as shown in FIG. 11, the tip of the side wall 90a is deformed so as to move in the direction of arrow F3 and the tip of the side wall 90b is deformed so as to move in the direction of arrow F4 as the temperature rises. In addition, a member having a relatively high thermal expansion coefficient is used for the outer peripheral portion of the second temperature-sensitive deformation member 92, and a member having a relatively low thermal expansion coefficient is used for the inner peripheral portion of the second temperature-sensitive deformation member 92. ing. For this reason, the second temperature-sensitive deformable member 92 is deformed in a direction in which the mounting portion 92a and the engaging portion 92b of the second temperature-sensitive deformable member 92 approach each other as the temperature rises. That is, as shown in FIG. 11, due to the temperature rise, the engaging portion 92b of the second temperature-sensitive deformable member 92 is deformed so as to move in the arrow F5 direction, and the mounting portion 92a of the second temperature-sensitive deformable member 92 is moved to the arrow. Deforms to move in the F6 direction.

  If the first temperature-sensitive deformation member 90 and the second temperature-sensitive deformation member 92 are at the same temperature, the pair of side wall portions 90a and 90b are deformed and the attachment portion 92a and the engagement portion 92b are moved to the arrow F3, The force pressing in the F4 direction is the same as the force pressing the pair of side wall portions 90a and 90b in the directions of arrows F5 and F6 due to the deformation of the mounting portion 92a and the engaging portion 92b. Further, when the temperature of the second temperature-sensitive deformable member 92 becomes relatively lower than the temperature of the first temperature-sensitive deformable member 90, the temperature difference between the first temperature-sensitive deformable member 90 and the second temperature-sensitive deformable member 92 is caused. The pair of side wall portions 90a and 90b of the first temperature-sensitive deformation member 90 are deformed in a direction away from each other against the second temperature-sensitive deformation member 92, and the first engagement portion 82a of the first strut member 82 and The second strut member 84 is pressed in the direction of separating the second engaging portion 84a.

  In the drum brake 76 configured as described above, the pair of brake shoes 18 and 20 are expanded from the standby position by the wheel cylinder 22 in a state where the linings 40 and 42 are worn and the shoe gap is increased, so that the struts When 78 is moved to the brake shoe 18 side of the pair of brake shoes 18 and 20 by the contact portion 80b of the adjustment lever 80, the lever portion 80a adjusts the adjustment according to the separation distance between the first strut member 82 and the brake shoe 20. The sting wheel 86 is rotated in a predetermined direction. Thereby, the strut 78 is extended and the shoe gap is adjusted.

  The drum brake 76 having the shoe gap automatic adjusting mechanism 74 of the present embodiment is used at a relatively low environmental temperature such as a cold region or at a relatively high environmental temperature such as a high temperature region. The operation of the shoe gap automatic adjusting mechanism 74 at the time of the above will be described.

  Even if the drum brake 76 is used at a relatively low environmental temperature such as winter in a cold region and a relatively high environmental temperature such as summer in a high temperature region, the brake shoes 18 and 20 accompanying the brake operation while the vehicle is running are used. When the temperature rise is small, the amount of frictional heat transmitted to the first temperature-sensitive deformation member 90 and the second temperature-sensitive deformation member 92 is small. For this reason, the temperature of the first temperature-sensitive deformation member 90 and the second temperature-sensitive deformation member 92 is substantially the same as the relatively low temperature or relatively high temperature environment temperature, that is, the temperature of the outside air (air). As a result, the pair of side wall portions 90a and 90b are deformed so that the first temperature-sensitive deformation member 90 separates the first engagement portion 82a of the first strut member 82 from the second engagement portion 84a of the second strut member 84. However, the second temperature-sensitive deformation member 92 suppresses the deformation of the pair of side wall portions 90a and 90b. For this reason, the first engagement portion 82a of the first strut member 82 and the second engagement portion 84a of the second strut member 84 are separated by the pair of side wall portions 90a and 90b of the first temperature-sensitive deformation member 90 during braking. Therefore, when the shoe gap becomes large, the shoe gap automatic adjusting mechanism 26 operates to adjust the shoe gap as described above.

  In addition, when the amount of frictional heat caused by brake operation is relatively large while the vehicle is running at a relatively low environmental temperature such as winter in a cold region or a relatively high environmental temperature such as summer in a hot region. The amount of frictional heat that is transiently transmitted to the second temperature-sensitive deformable member 72 is smaller than that of the first temperature-sensitive deformable member 90 by the pair of low heat conducting members 94 and 96, and the second temperature-sensitive deformable member 72 The temperature of the member 92 is lower than the temperature of the first temperature-sensitive deformation member 90. The first strut member 82 is obtained when the force in the directions of arrows F3 and F4 of the pair of side wall portions 90a and 90b of the first temperature-sensitive deformation member 90 exceeds the force of the second temperature-sensitive deformation member 92 in the directions of arrows F5 and F6. And the brake shoe 20 are brought into contact with each other, so that the first strut member 82 is prevented from being separated from the brake shoe 20 at the time of overheating. Therefore, the temperature of the brake drum 12 rises due to frictional heat, and the inner diameter of the brake drum 12 increases. When the diameter is increased, the adjustment lever 80 does not rotate, so that the automatic adjustment of the shoe gap of the shoe gap automatic adjustment mechanism 74 is suppressed.

  As shown in FIGS. 12 to 14, the drum brake 100 including the shoe gap automatic adjusting mechanism 98 of the present embodiment is not provided with the pair of low heat conduction members 94 and 96 of the above-described third embodiment. The shape of the second temperature-sensitive deformable member 102 is different from that of the second temperature-sensitive deformable member 92 of Example 3 described above, and the other configurations are substantially the same.

  As shown in FIG. 12, the second temperature-sensitive deformable member 102 is deformed to the side that suppresses the deformation of the first temperature-sensitive deformable member 90 due to a temperature rise, as in the third embodiment. The second temperature-sensitive deformation member 102 has a flat plate-shaped attachment portion 102a attached between the side wall portion 90a of the first temperature-sensitive deformation member 90 and the end portion of the second strut member 84 on the brake shoe 20 side, An engaging portion 102b similar to the engaging portion 92b of the third embodiment, a connecting portion 102c similar to the connecting portion 92c of the third embodiment, a fitting hole 102d similar to the fitting hole 92d of the third embodiment, and an implementation. An insertion hole 102e similar to the insertion hole 92e of Example 3 and a notch 102f similar to the notch 92f of Example 3 are integrally provided.

  As shown in FIGS. 13 and 14, the attachment portion 102a of the second temperature-sensitive deformation member 102 has a plurality of protrusions protruding toward the first temperature-sensitive deformation member 90 side and the second strut member 84 side in the thickness direction of the attachment portion 102a. A protrusion (contact area decreasing portion) 102g is formed. The mounting portion 102a of the second temperature-sensitive deformation member 102 is sandwiched between the end portion of the second strut member 84 on the brake shoe 20 side and the side wall portion 90a of the first temperature-sensitive deformation member 90. The tip portions of the plurality of protrusions 102g formed on the attachment portion 102a are in contact with the end portion of the second strut member 84 on the brake shoe 20 side and the side wall portion 90a of the first temperature-sensitive deformation member 90.

  In other words, the attachment area 102a of the second temperature-sensitive deformation member 102 has the contact area between the second strut member 84 to which the attachment part 102a is attached and the side wall part 90a of the first temperature-sensitive deformation member 90 as described in the third embodiment. A plurality of protrusions 102g that are smaller than the attachment portion 92a of the second temperature-sensitive deformation member 92 are formed. For this reason, when the frictional heat at the time of braking is transmitted to the first temperature-sensitive deformation member 90 and the second temperature-sensitive deformation member 102, the first temperature-sensitive deformation member 90 and the second temperature-sensitive deformation member 102 are transiently transmitted. A temperature difference is preferably large between them, and over-adjustment by the shoe gap automatic adjusting mechanism 98 is prevented. Further, in the drum brake 100 having the shoe gap automatic adjusting mechanism 98 of the present embodiment, when the frictional heat at the time of braking is transmitted to the first temperature-sensitive deformation member 90 and the second temperature-sensitive deformation member 102, the above-described implementation is performed. The temperature of the second temperature-sensitive deformable member 102 is changed to the first temperature-sensitive deformable member 102 by the plurality of protrusions 102g provided on the second temperature-sensitive deformable member 102 without using the pair of low heat conductive members 94 and 96 of Example 3. The difference from the drum brake 76 having the shoe gap automatic adjusting mechanism 74 of the third embodiment is that the temperature is lower than 90. For this reason, the drum brake 100 provided with the shoe gap automatic adjusting mechanism 98 of this embodiment has the same effect as the drum brake 76 provided with the shoe gap automatic adjusting mechanism 74 of the third embodiment.

  As shown in FIGS. 15 to 17, the drum brake 106 including the shoe gap automatic adjusting mechanism 104 according to the present embodiment includes a shoe gap automatic adjusting mechanism 104 different from the shoe gap automatic adjusting mechanism 74 according to the third embodiment. In other respects, the configuration is substantially the same.

  As shown in FIG. 15, the shoe gap automatic adjusting mechanism 104 is provided with an adjusting lever (adjusting member) 108 provided in the second engaging portion 84 a of the second strut member 84. The adjustment lever 108 is made of an elastically deformable plate-like member, for example, a spring plate material. A base end portion 108a for fixing the adjustment lever 108 to the second engagement portion 84a of the second strut member 84, and a base thereof. A lever portion 108b extending from the end portion 108a toward the brake shoe 20 side of the pair of brake shoes 18 and 20, and an adjusting portion for engaging with an adjusting wheel from the tip end portion of the lever portion 108b when the drum brake 10 is braked. A plate-like engagement portion 108c extended to the wheel 86 side is integrally provided.

  As shown in FIG. 15, an insertion hole 110 a for inserting the screw shaft portion 82 c of the first strut member 82 is provided between the adjusting wheel 86 and the end of the second strut member 84 on the brake shoe 20 side. A flat plate-shaped first lever portion 110b sandwiched between the adjusting wheel 86 and the end of the second strut member 84 on the brake shoe 20 side, and a predetermined angle greater than a right angle with respect to the first lever portion 64b, for example, A lever member 110 configured by a plate-like second lever portion 110c bent at about 100 ° is provided. The adjusting lever 108 is fixed to the second engaging portion 84a of the second strut member 84 in a state where the engaging portion 108c, which is the tip portion of the lever portion 108b, is urged toward the adjusting wheel 86. . The distal end portion of the second lever portion 110c abuts on the lever portion 108b of the adjusting lever 108 and is urged in the direction of arrow F7 by the elastic return force of the adjusting lever 108. Further, the biasing force that separates the first strut member 82 and the second strut member 84 by biasing the lever member 110 in the direction of arrow F7 by the elastic return force of the adjusting lever 108 is smaller than the biasing force of the return spring 24. Is.

  As shown in FIG. 15, at the end of the strut 78 on the brake shoe 18 side, a first temperature-sensitive deformation member 112 that suppresses the separation of the second strut member 84 from the brake shoe 20 due to deformation accompanying a rise in temperature, A second temperature-sensitive deformation member 114 that is deformed to a side that suppresses deformation of the first temperature-sensitive deformation member 112 due to a temperature rise is provided.

  The first temperature-sensitive deformation member 112 has a flat plate-shaped fixing portion 112a fixed to the second engaging portion 84a of the second strut member 84, and a distal end portion extending from the fixing portion 112a to the brake shoe 20 side. 16 and FIG. 17, a lever 112b having a long plate shape that passes through a through-hole 110d that penetrates the first lever 110b of the lever member 110 shown in FIG. 17, and the width of the lever 112b formed at the tip of the lever 112b. And a flat plate-shaped engaging portion 112c having a width dimension b larger than the dimension a. Further, as shown in FIGS. 16 and 17, the through hole 110d of the first lever member 110b includes a first hole 110e having a width dimension c larger than the width dimension b of the engaging part 112c, and the first hole part. 110e is formed by a second hole portion 110f having a width dimension d smaller than the width dimension b formed on the end side of the first lever portion 110b and larger than the width dimension a. For example, when the engaging portion 112c of the first temperature-sensitive deformation member 112 is at the position of the solid line in FIG. 17, the direction in which the end portion of the first lever portion 110b of the lever member 110 approaches the brake shoe 20, that is, When attempting to move in the direction of arrow F8 in FIGS. 15 and 16, the first temperature-sensitive deformable member 112 abuts on the engaging portion 112c and is prevented from moving in the direction of arrow F8. Further, for example, when the engaging portion 112c of the first temperature-sensitive deformation member 112 is at the position of the one-dot chain line in FIG. 17, the end portion of the first lever portion 110b of the lever member 110 tries to move in the direction of arrow F8. Then, the engaging part 112c of the first temperature-sensitive deformable member 112 is inserted through the first hole part 110e of the through hole 110d and is allowed to move in the arrow F8 direction.

  The second temperature-sensitive deformable member 114 has a flat plate-shaped fixed portion 114a fixed to the fixed portion 112a of the first temperature-sensitive deformable member 112 via a low heat conductive member 116, which will be described later, and a tip portion of the first temperature-sensitive deformable member 114. An engaging portion 114b that engages with a part of the lever portion 112b of the member 112 and a long flat plate-like connecting portion 114c that connects the engaging portion 114b and the fixing portion 114a are integrally provided.

  The second temperature-sensitive deformable member 114 is formed of the first temperature-sensitive deformable member 112 via the strut 78, that is, the second strut member 84 or the flat plate-shaped low heat conductive member 116 having a lower thermal conductivity than the first temperature-sensitive deformable member 112. The fixing portion 112a is provided. Further, the fixing portion 112a of the first temperature-sensitive deformation member 112, the fixing portion 114a of the second temperature-sensitive deformation member 114, and the low heat conduction member 116 respectively protrude from the second engagement portion 84a of the second strut member 84. Insertion holes 112d, 114d, and 116a through which the pair of protrusions 84e are inserted are formed, and the tip portions of the pair of protrusions 84e are caulked and deformed, whereby the fixing portions 112a of the first temperature-sensitive deformation members 112, The fixing part 114 a of the second temperature-sensitive deformation member 114 and the low heat conduction member 116 are fixed to the second engaging part 84 a of the second strut member 84.

  The first temperature-sensitive deformable member 112 and the second temperature-sensitive deformable member 114 are so-called bimetals joined together at high pressure by rolling or the like in a state where two thin plates having different thermal expansion coefficients are combined. In the present embodiment, a member having a relatively high coefficient of thermal expansion is used on the strut 78 side in the thickness direction of the first temperature-sensitive deformable member 112 of the first temperature-sensitive deformable member 112. A member having a relatively low coefficient of thermal expansion is used on the side opposite to the strut 78 side in the thickness direction. For this reason, the first temperature-sensitive deformation member 66 is deformed so that the engagement portion 112c of the temperature-sensitive deformation member 112 moves away from the adjusting wheel 86, that is, the arrow F9 direction shown in FIG. To do. That is, the first temperature-sensitive deformation member 112 is deformed so that the lever portion 112b is positioned in the second hole portion 110f shown in FIG. When the first temperature-sensitive deformation member 112 is not deformed, the lever portion 112b is located in the first hole portion 110e shown in FIG. In addition, a member having a relatively low coefficient of thermal expansion is used on the strut 78 side in the thickness direction of the second temperature-sensitive deformable member 114 of the second temperature-sensitive deformable member 114, and the second temperature-sensitive deformable member 114 has its second A member having a relatively high coefficient of thermal expansion is used on the side opposite to the strut 78 side in the thickness direction of the temperature-sensitive deformation member 114. For this reason, the second temperature-sensitive deformable member 114 moves in a direction opposite to the arrow F9 direction, that is, the arrow F10 direction shown in FIG. 15, as the temperature rises, the engagement portion 114b of the second temperature-sensitive deformable member 114 moves. Deform to That is, the second temperature-sensitive deformable member 114 is deformed to a side that suppresses deformation of the first temperature-sensitive deformable member 112 due to a temperature rise.

  The first temperature-sensitive deformable member 112 and the second temperature-sensitive deformable member 114 are engaged with a force that deforms the engaging portion 112c and presses the engaging portion 114b in the direction of arrow F9 if they are the same temperature. The portion 114b is deformed to have the same force as pressing the engaging portion 112c in the direction of the arrow F10, and the deformation of the first temperature-sensitive deformation member 112 is suppressed. Further, when the temperature of the second temperature-sensitive deformable member 114 becomes relatively lower than the temperature of the first temperature-sensitive deformable member 112, the temperature difference between the first temperature-sensitive deformable member 112 and the second temperature-sensitive deformable member 114 is caused. The engaging portion 112c of the first temperature-sensitive deformation member 112 is deformed in the direction of the arrow F9 against the second temperature-sensitive deformation member 114.

  In the drum brake 106 configured as described above, the pair of brake shoes 18 and 20 are expanded from the standby position by the wheel cylinder 22 in a state where the linings 40 and 42 are worn and the shoe gap is increased, and the adjustment is performed. The second lever portion 110c of the lever member 110 is pushed in the direction of arrow F7 by the elastic return force of the lever 108, and the first lever portion 110b is pushed in the direction of arrow F8. As a result, the first engaging portion 82a of the first lever member 82 and the second engaging portion 84a of the second lever member 84 move away from each other, and the second strut member 84 and the brake shoe 20 are moved. The adjusting wheel 86 is rotated in a predetermined direction by the lever portion 108b according to the separation distance. Thereby, the strut 78 is extended and the shoe gap is adjusted.

  The drum brake 106 having the shoe gap automatic adjusting mechanism 104 of the present embodiment is used at a relatively low environmental temperature such as a cold region or at a relatively high environmental temperature such as a high temperature region. The operation of the shoe gap automatic adjusting mechanism 104 at the time will be described.

  Even if the drum brake 106 is used at a relatively low environmental temperature such as winter in a cold region and a relatively high environmental temperature such as summer in a high temperature region, the brake shoes 18 and 20 accompanying the brake operation while the vehicle is running. When the temperature rise is small, the amount of frictional heat transmitted to the first temperature-sensitive deformation member 112 and the second temperature-sensitive deformation member 114 is small. For this reason, the temperature of the first temperature-sensitive deformation member 112 and the second temperature-sensitive deformation member 114 is substantially the same as the relatively low temperature or relatively high temperature, that is, the temperature of the outside air (air). Thus, the first temperature-sensitive deformable member 112 tends to deform in the direction of the arrow F9, but the second temperature-sensitive deformable member 114 suppresses the deformation. For this reason, the movement of the first lever member 110b of the lever member 110 in the direction of the arrow F8 is permitted during braking. Therefore, when the shoe gap becomes large, the shoe gap automatic adjustment mechanism 26 operates to reduce the shoe gap as described above. Adjusted.

  When the amount of frictional heat caused by brake operation is relatively high while the vehicle is running at a relatively low environmental temperature such as winter in a cold region or a relatively high environmental temperature such as summer in a high temperature region The amount of frictional heat that is transiently transmitted to the second temperature-sensitive deformable member 114 is smaller than that of the first temperature-sensitive deformable member 112 by the low heat conductive member 116, and the temperature of the second temperature-sensitive deformable member 114 is It becomes lower than the temperature of the first temperature-sensitive deformation member 112. The force that the engaging portion 112c of the first temperature-sensitive deformable member 112 pushes in the direction of arrow F9 exceeds the force of the second temperature-sensitive deformable member in the direction of arrow F10, whereby the engaging portion 112c of the first temperature-sensitive deformable member 112. Moves in the direction of arrow F9, and the lever portion 112b is positioned in the second hole portion 110f of the through hole 110d formed in the first lever portion 110b of the lever member 110. As a result, the lever member 110 abuts on the engaging portion 112c of the first temperature-sensitive deformable member 112 and the movement of the first lever portion 110b in the direction of the arrow F8 is prevented. When the separation from the brake shoe 20 is suppressed and the temperature of the brake drum 12 rises due to frictional heat and the inner diameter of the brake drum 12 is increased, the adjusting wheel 86 is rotated by the adjusting lever 108. Therefore, the automatic adjustment of the shoe gap of the shoe gap automatic adjustment mechanism 104 is suppressed.

  According to the drum brake 106 having the shoe gap automatic adjusting mechanism 104 of the present embodiment, the adjusting lever 108 has the lever portion 108b that engages with the adjusting wheel 86, and the lever portion 108b is adjusted to the strut 78. It is fixed in a state of being biased toward the wheel 86 side.

  As shown in FIGS. 18 and 19, the drum brake 120 provided with the shoe gap automatic adjusting mechanism 118 of the present embodiment is not provided with the low heat conduction member 116 of the above-described fifth embodiment, and the second temperature sensing. The shape of the fixing portion 112a of the deformation member 122 is different from that of the fixing portion 114a of the second temperature-sensitive deformation member 114 of the above-described fifth embodiment, and the other configuration is substantially the same.

  As shown in FIG. 18, the second temperature-sensitive deformable member 122 is deformed to the side of suppressing the deformation of the first temperature-sensitive deformable member 112 due to a temperature rise, as in the fifth embodiment. The second temperature-sensitive deformable member 122 includes a flat plate-shaped fixed portion (contact area reducing portion) 122a directly fixed to the fixed portion 112a of the first temperature-sensitive deformable member 112 and the engaging portion 114b of the fifth embodiment. The engagement portion 122b, the connection portion 122c similar to the connection portion 114c of the fifth embodiment, and the insertion hole 122d similar to the insertion hole 114d of the fifth embodiment are integrally provided.

  As shown in FIG. 19, the fixing portion 122 a of the second temperature-sensitive deformation member 122 has a contact area between the second temperature-sensitive deformation member 122 and the fixing portion 112 a of the first temperature-sensitive deformation member 112 of the above-described fifth embodiment. The second temperature-sensitive deformable member 114 is reduced in comparison with the fixed portion 114a. In addition, the dashed-dotted line shown by FIG. 19 shows the shape of the fixing | fixed part 114a of the 2nd temperature sensitive deformation member 114 of Example 5. FIG.

  For this reason, when frictional heat is transmitted to the first temperature-sensitive deformable member 112 and the second temperature-sensitive deformable member 122 during braking, a transition between the first temperature-sensitive deformable member 112 and the second temperature-sensitive deformable member 122 is transiently performed. Thus, a large temperature difference is preferably generated, and over-adjustment by the shoe gap automatic adjustment mechanism 120 is prevented. Further, the drum brake 118 having the shoe gap automatic adjusting mechanism 120 of the present embodiment, when the frictional heat is transmitted to the first temperature-sensitive deformation member 112 and the second temperature-sensitive deformation member 122, the low heat conduction of the fifth embodiment. The temperature of the second temperature-sensitive deformation member 122 is made lower than the temperature of the first temperature-sensitive deformation member 112 by the fixing portion 122a that is a contact area reducing portion provided in the second temperature-sensitive deformation member 122 without using the member 116. This is only different from the drum brake 106 having the shoe gap automatic adjusting mechanism 104 of the fifth embodiment. For this reason, the drum brake 118 provided with the shoe gap automatic adjusting mechanism 120 of this embodiment has the same effect as the drum brake 106 provided with the shoe gap automatic adjusting mechanism 104 of the fifth embodiment.

  As shown in FIGS. 20 and 21, in the drum brake having the shoe gap automatic adjusting mechanism of the present embodiment, the shape of the fixing portion 124a of the second temperature-sensitive deformable member 124 is the second temperature sensitive of the aforementioned sixth embodiment. It differs in the point which is different from the fixing | fixed part 122a of the deformation | transformation member 122, and other than that is comprised substantially the same.

  As shown in FIGS. 20 and 21, the fixing portion 124 a of the second temperature-sensitive deformation member 124 has a plurality of protrusions protruding toward the fixing portion 112 a of the first temperature-sensitive deformation member 112 in the thickness direction of the fixing portion 124 a ( A contact area reducing portion) 124b is formed. Further, the fixing portion 124a of the second temperature-sensitive deformation member 124 is fixed to the fixing portion 112a of the first temperature-sensitive deformation member 112, and the tips of the plurality of protrusions 124b formed on the fixing portion 124a are the first portions. 1 The temperature-sensitive deformation member 112 is in contact with the fixing portion 112a.

  For this reason, when frictional heat is transmitted to the first temperature-sensitive deformation member 112 and the second temperature-sensitive deformation member 124 during braking, a transition between the first temperature-sensitive deformation member 112 and the second temperature-sensitive deformation member 124 is made transiently. Thus, a large temperature difference is preferably generated, and over-adjustment by the shoe gap automatic adjusting mechanism is prevented.

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

  For example, in the shoe gap automatic adjusting mechanisms 26 and 104 of the present embodiment, the second temperature-sensitive deformation members 68 and 114 are provided in the second strut members 58 and 84 via the low heat conductive members 70 and 116, respectively. The second temperature-sensitive deformation members 68 and 114 may be fixed to the second strut members 58 and 84 via the low heat conduction members 70 and 116, although they are fixed to the temperature-deformation members 66 and 112. Further, the second temperature-sensitive deformation members 68 and 114 may be fixed to the first strut members 56 and 82 via the low heat conductive members 70 and 116.

  Further, in the shoe gap automatic adjusting mechanisms 26, 118 of the present embodiment, the fixing portions 72a, 122a, 124a, which are the contact area reducing portions of the second temperature-sensitive deformation members 72, 122, 124, are the second strut members 58, 84. The first temperature-sensitive deformable members 66 and 112 provided on the first strut members 58 and 84 are fixed to the first temperature-sensitive deformable members 66 and 112. , 122 and 124 cause a temperature difference. Further, the fixing portions 72a, 122a, and 124a, which are the contact area decreasing portions of the second temperature-sensitive deformation members 72, 122, and 124, may be directly fixed to the first strut members 56 and 82.

  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.

10, 76, 106, 120: Drum brake 12: Brake drum (rotating drum)
18, 20: A pair of brake shoes 26, 74, 98, 104, 118: Automatic shoe clearance adjustment mechanism 52, 78: Struts 54, 80, 108: Adjust lever (adjustment member)
54c, 80a, 108b: lever portions 56, 82: first strut members 58, 84: second strut members 60a, 86: adjusting wheels 66, 90, 112: first temperature-sensitive deformation members 68, 72, 92, 102 114, 122, 124: second temperature-sensitive deformation members 72a, 122a: fixed portion (contact area reducing portion)
70, 94, 96, 116: Low thermal conductive members 102g, 124b: Projections (contact area reduced portions)

Claims (5)

A first strut member that engages with one end portion of the pair of expandable brake shoes, a second strut member that engages with the other end portion of the pair of brake shoes, the first strut member, An adjusting wheel disposed between the two strut members and extending the distance between the first strut member and the second strut member by being rotated, and the pair of brakes at the time of non-braking A strut that defines the standby position of the shoe;
An adjusting member for rotating the adjusting wheel in one direction in relation to a separation operation between the first strut member or the second strut member and one of the brake shoes;
A drum brake provided with 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 by rotating the adjusting wheel by the adjusting member. There,
The strut includes a first temperature-sensitive deformation member that suppresses the separation of the first strut member or the second strut member from one of the brake shoes due to deformation caused by a temperature rise, and the first temperature-sensitive deformation caused by a temperature rise. A second temperature-sensitive deformation member that deforms to a side that suppresses deformation of the deformation member ,
The first temperature-sensitive deformation member is provided on the first strut member or the second strut member so as to be closer to the first strut member side or the second strut member side than the second temperature-sensitive deformation member. And
The separation of the first strut member or the second strut member from one of the brake shoes is suppressed based on a temperature difference between the first temperature-sensitive deformable member and the second temperature-sensitive deformable member. Drum brake with automatic shoe clearance adjustment mechanism.   2. The shoe clearance automatic adjusting mechanism according to claim 1, wherein the second temperature-sensitive deformation member is provided on the first strut member or the second strut member via a low heat conductive member having a lower thermal conductivity than the strut. Drum brake provided.   The second temperature-sensitive deformable member is formed with a contact area reducing portion that relatively reduces the contact area with the first strut member or the second strut member to which the second temperature-sensitive deformable member is attached. A drum brake comprising the shoe gap automatic adjusting mechanism according to claim 1.   4. The shoe gap automatic adjusting mechanism according to claim 1, wherein the adjusting member has a lever portion that engages with the adjusting wheel and is rotatably provided on one of the pair of brake shoes. 5. Drum brake provided.   The adjustment member has a lever portion that engages with the adjusting wheel, and the lever portion is provided on the strut in a state of being biased toward the adjusting wheel. A drum brake equipped with one shoe clearance automatic adjustment mechanism.

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