JP2013015193A - Drum brake - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a drum brake which renders its braking force improved in comparison with a conventional one by getting a contact area where a brake shoe is brought into contact with a rotary drum larger in comparison with a conventional one when the drum brake brakes.SOLUTION: When the other ends of the first brake shoes 22 and 24 are brought into contact with the brake drum 12 by an expansion device 20, the first brake shoe 22 rotates together with the brake drum 12 to cause a corotation force F1 to rotate the first brake shoe 22 around a transmission member 32 so that one end of the first brake shoe 22 may approach the inner peripheral face 14 of the brake drum 12. Therefore, one end and the other end of the first brake shoe 22 are brought into contact with the brake drum 12 to get the contact area where the first brake shoe is brought into contact with the brake drum 12 when the drum brake 10 brakes larger in comparison with the conventional brake shoe, thereby rendering the braking force of the drum brake 10 improved in comparison with the conventional one.

Description

  The present invention relates to a technique for improving the performance of a drum brake, particularly a leading / trailing drum brake.

  For example, as shown in FIG. 12, the drum brake includes a pair of brake shoes 110 and 120 having an arc shape that is disposed on the backing plate 100 so as to be expandable, and between one end portions of the pair of brake shoes 110 and 120. And a pair of brake shoes 110 and 120 which are spread out to the outer peripheral side of the backing plate 100 by separating one end portions of the pair of brake shoes 110 and 120 from each other. And 120, which are in sliding contact with the inner peripheral surface 140a of the rotating drum 140 that rotates together with the vehicle wheel, and an anchor member 150 that receives the other end of one of the pair of brake shoes 110 and 120. Further, two concentric circles indicated by a one-dot chain line in FIG. 12 virtually indicate the rotating drum 140, and a circle on the center side of the two circles virtually indicates the inner peripheral surface 140 a of the rotating drum 140. It is. The drum brake as described above is, for example, a leading / trailing type drum brake as shown in FIG.

  The leading / trailing drum brake as described above is a brake in which the cam member 130a of the expansion device 130 is not shown when the rotary drum 140 rotates in the direction of the arrow A1 as shown in FIG. When the lever is rotated in the direction of arrow A2, the pair of brake shoes 110 and 120 are separated from each other by the cam member 130a so that the shaft center C of the anchor member 150 is separated. Rotate around. Therefore, the brake shoe 110 abuts on the inner peripheral surface 140a of the rotating drum 140 and receives a follower force from the rotating drum 140, and the other end portion of the brake shoe 110 is received by the anchor member 150 and is rotated. Braking force is generated.

JP 2005-133911 A

  However, in the leading / trailing type drum brake as described above, when the one end portions of the pair of brake shoes 110 and 120 are separated from each other by the cam member 130a of the spreading device 130, the pair of brake shoes 110 and 120 are anchored. Since it rotates around the axis C of the member 150, only a part of the brake shoes 110 and 120 substantially contacts the inner peripheral surface 140a of the rotary drum 140, and the brake shoes 110 and 120 and the rotary drum 140 are in contact with each other. Since the effective contact area with the inner peripheral surface 140a of the rotating drum 140 becomes relatively small, there is a problem that the magnitude of the braking force for braking the rotation of the rotating drum 140 may not be sufficiently obtained. there were.

  The present invention has been made against the background of the above circumstances. The purpose of the present invention is to provide a contact area where the brake shoe is brought into contact with the inner peripheral surface of the rotating drum during braking of the drum brake. It is an object of the present invention to provide a drum brake having a larger braking force than that of a conventional drum brake.

  The gist of the first invention for achieving this object is as follows: (a) a pair of brake shoes having an arc shape disposed in a backing plate so as to be expandable, and one end portion of the pair of brake shoes. And a widening device that spreads one end of the pair of brake shoes to the outer peripheral side of the backing plate by separating them from each other, and the pair of brake shoes together with the wheels of the vehicle by the widening device A drum brake that includes an anchor member that is in sliding contact with the inner peripheral surface of the rotating drum and that is received by the other end of the pair of brake shoes, and (b) the pair of brake shoes includes (b- 1) A part of the backing plate which is located on the side of the expansion device and has a partial arc shape whose one end is urged by a return spring in a direction approaching the expansion device. (B-2) a pair of first arcs that are located on the side of the anchor member of the backing plate and have a partial arc shape whose one end is urged by a return spring in a direction approaching the anchor member. 2 shoe part, (b-3) provided between the other end part of the second shoe part and the other end part of the first shoe part, and the first shoe part and the second shoe part are relatively rotated. , And the other end portion of the first shoe portion allows relative movement of the second shoe portion to the outer peripheral side of the backing plate with respect to the other end portion of the second shoe portion. And a pair of transmission members that transmit to each other.

  In addition, the gist of the second invention is that, in the first invention, the first shoe portion is formed on the outer peripheral side of the backing plate from a position where it abuts on the transmission member at the other end of the first shoe portion. A first projecting portion projecting toward the other end portion of the second shoe portion to prevent the transmission member from moving toward the outer peripheral side of the backing plate; and a second projecting portion of the first shoe portion. A flat first guide portion that is formed on the inner circumferential side of the backing plate from a position where the transmission member abuts and that allows the transmission member to move toward the inner circumferential side of the backing plate. There is.

  Further, the gist of the third invention is that in the first invention or the second invention, the second shoe portion is arranged at an outer periphery of the backing plate from a position where the second shoe portion comes into contact with the anchor member at one end portion of the second shoe portion. A second projecting portion projecting toward the anchor member in order to prevent the one end portion of the second shoe portion from moving toward the inner peripheral side of the backing plate, and one end of the second shoe portion A flat second guide that is formed on the inner peripheral side of the backing plate from a position where the anchor member abuts, and allows one end of the second shoe portion to move to the outer peripheral side of the backing plate. And having a part.

  The gist of the fourth invention is that in any one of the first to third inventions, (a) the anchor member includes a large-diameter head and a shaft having a smaller diameter than the large-diameter head. (B) the first shoe portion and the second shoe portion are each formed of a band plate-like shoe rim bent into a partial arc shape, and an inner portion of the shoe rim. A pair of shoe webs facing each other and projecting a predetermined amount from both ends in the width direction of the peripheral surface toward the inner peripheral side of the backing plate, and (c) the return spring, One end portion of the pair of shoe webs of the second shoe portion is pressed against the shaft portion of the anchor member.

  Moreover, the gist of the fifth invention is that, in the fourth invention, (a) in the first shoe portion and the second shoe portion, the pair of shoe webs is provided between the pair of shoe webs. (B) the return spring is disposed between the pair of shoe webs in the first shoe portion and the second shoe portion, and is disposed between the pair of shoe webs. It is bent from a single wire so as to abut on the latching pin erected from the outer peripheral side and urge it toward the inner peripheral side.

  According to the drum brake of the first invention, (b) the pair of brake shoes are (b-1) located on the side of the expansion device of the backing plate, and one end thereof approaches the expansion device by a return spring. A pair of first shoe portions that form a partial arc shape biased in the direction to be moved, and (b-2) a direction in which one end portion approaches the anchor member by a return spring located on the anchor member side of the backing plate A pair of second shoe portions having a partial arc shape biased by (b-3) provided between the other end portion of the second shoe portion and the other end portion of the first shoe portion; The first shoe portion and the second shoe portion are relatively rotated, and the other end portion of the first shoe portion is allowed to move relative to the outer peripheral side of the backing plate with respect to the other end portion of the second shoe portion. The turning force of one shoe part And a pair of transmission members that transmit to the two shoe portions. For this reason, when one end part of the pair of first shoe parts is moved to the outer peripheral side of the backing plate by the expanding device, the other end part of the pair of first shoe parts is moved to the outer peripheral side of the backing plate. The other ends of the pair of first shoe portions are brought into contact with the inner peripheral surface of the rotating drum. As a result, one of the pair of first shoe portions is moved by the accompanying force from the rotating drum so that one end portion of the one first shoe portion approaches the inner peripheral surface of the rotating drum. Since one shoe part rotates around the transmission member, the one end part and the other end part of the first shoe part are brought into contact with each other so as to be in full contact with the inner peripheral surface of the rotating drum, and at the same time The second shoe portion is rotated around the anchor member and brought into contact with the inner peripheral surface of the rotating drum, and the one first shoe portion is engaged with the rotating drum when the drum brake is braked. The contact area where the contact area is larger than that of a conventional brake shoe, and the surface pressure between the one end and the other end of the first shoe portion presses the inner peripheral surface of the rotating drum. Even distribution , Braking force of the drum brake is improved as compared with the prior art. Further, during braking of the drum brake, the first shoe portion is brought into contact with the inner peripheral surface of the rotary drum so that the first shoe portion and the other end portion are in close contact with each other. The uneven wear of the friction material of the part is suppressed, and the durability of the first shoe part is preferably improved.

  According to the drum brake of the second invention, the first shoe portion is formed on the outer peripheral side of the backing plate from a position where the first shoe portion contacts the transmission member at the other end of the first shoe portion. A position where the first projecting portion projecting to the other end portion side of the second shoe portion and the transmitting member at the other end portion of the first shoe portion abut on each other to prevent the backing plate from moving to the outer peripheral side. And a flat first guide portion for allowing the transmission member to move to the inner peripheral side of the backing plate. For this reason, when one end part of the pair of first shoe parts is moved to the outer peripheral side of the backing plate by the spreading device, the other end part of the pair of first shoe parts is also the first protrusion of the other end part. Since the first guide portion, which is flat at the other end, is moved to the outer peripheral side of the backing plate from the position where the portion is in contact with the transmission member, one end of the first shoe portion is moved. The entire surface can be easily brought into contact with the inner peripheral surface of the rotary drum between the first portion and the other end portion.

  According to the drum brake of the third invention, the second shoe part is formed on the outer peripheral side of the backing plate from a position where the second shoe part comes into contact with the anchor member at one end of the second shoe part. The second projecting portion projecting toward the anchor member side in order to prevent the one end portion from moving toward the inner peripheral side of the backing plate, and the position where the anchor member at the one end portion of the second shoe portion abuts. A flat second guide portion that is formed on the inner peripheral side of the backing plate and allows one end of the second shoe portion to move to the outer peripheral side of the backing plate. For this reason, at the time of braking of the drum brake, if the one first shoe portion is rotated together with the rotary drum, one end portion of the second shoe portion is a flat second end portion of the one end portion via the transmission member. The guide portion moves to the outer peripheral side of the backing plate while sliding on the anchor member, and one end portion of the second shoe portion comes into contact with the inner peripheral surface of the rotating drum. As a result, the second shoe portion rotates with the rotating drum, and the second end portion of the second shoe portion approaches the inner peripheral surface of the rotating drum by the rotating force of the rotating drum. Since the shoe portion rotates around the anchor member, the one end portion and the other end portion of the second shoe portion are brought into contact with each other so as to more closely contact the inner peripheral surface of the rotating drum, The contact area where the one brake shoe abuts against the rotating drum during braking of the drum brake is preferably larger than that of the conventional brake shoe, and one end of the one second shoe portion. The surface pressure distribution that presses the inner peripheral surface of the rotating drum is uniform between the portion and the other end portion, and the braking force of the drum brake is further improved compared to the conventional case. Further, when braking the drum brake, the second shoe portion is brought into contact with the inner peripheral surface of the rotary drum so that the one end portion and the other end portion of the second shoe portion are in close contact with each other. The uneven wear of the friction material of the part is suppressed, and the durability of the second shoe part is preferably improved.

  According to the drum brake of the fourth invention, (a) the anchor member has a large-diameter head and a shaft having a smaller diameter than the large-diameter head, and is erected on the backing plate. (B) The first shoe portion and the second shoe portion are formed of a band plate-like shoe rim bent in a partial arc shape and an inner portion of the backing plate integrally from both end portions in the width direction of the inner peripheral surface of the shoe rim. A pair of shoe webs facing each other and projecting a predetermined amount toward the circumferential side, and (c) the return spring has one end of the pair of shoe webs of the second shoe portion connected to the anchor It presses against the shaft part of the member. For this reason, the second shoe portion is pressed by the urging force of the return spring so that one end portions of the pair of shoe webs of the second shoe portion are pressed against two locations on the outer peripheral surface of the shaft portion of the anchor member. Since the posture of the second shoe portion disposed on the backing plate is maintained, the shoe hold-down device conventionally used for maintaining the posture of the brake shoe can be dispensed with.

  According to the drum brake of the fifth aspect of the invention, (a) in the first shoe portion and the second shoe portion, the pair of shoe webs has a latch pin fixed between the pair of shoe webs. (B) The return spring is disposed between the pair of shoe webs in the first shoe portion and the second shoe portion, and is hooked between the pair of shoe webs. It is bent from a single wire so as to abut on the outer peripheral side and urge toward the inner peripheral side. For this reason, the return spring is disposed between the pair of shoe webs in the pair of first shoe portions and the pair of second shoe portions by being latched by the latch pin. Compared to a coil-like return spring that is stretched between a pair of brake shoes, the space on the inner peripheral portion of the backing plate is suitably widened, and the drum brake is operated by a worker on the vehicle body side member. Since it becomes difficult to contact the return spring when mounted on the drum brake, it is easy to attach the drum brake.

It is a front view which shows the drum brake of one Example to which this invention was applied. It is the II-II sectional view taken on the line of FIG. FIG. 3 is a sectional view taken along line III-III in FIG. 1. FIG. 4 is a sectional view taken along line IV-IV in FIG. 1. It is a figure which shows the shape of the one end part of a 2nd brake shoe. It is a figure which shows the shape of the other end part of a 1st brake shoe, and the shape of the other end part of a 2nd brake shoe. It is a figure which shows the state which the cam member of an expansion apparatus rotates, and the one end part of a pair of brake shoes expands. It is a figure which shows the state which the other end part of a 1st brake shoe moves to the outer peripheral side of a backing plate, and contact | abuts to the internal peripheral surface of a brake drum by an expansion apparatus. It is a figure which shows the state which the other end part of a 1st brake shoe contact | abuts to the internal peripheral surface of a brake drum, and the 1st brake shoe rotates with a brake drum. A state in which the accompanying force of the first brake shoe is transmitted to the second brake shoe via the transmission member, and one end portion of the second brake shoe moves to the outer peripheral side of the backing plate and contacts the inner peripheral surface of the brake drum FIG. It is a figure which shows the state which the one end part of a 2nd brake shoe contact | abuts to the internal peripheral surface of a brake drum, and the 2nd brake shoe rotates with a brake drum. It is a figure explaining the conventional leading / trailing type drum brake. It is a figure explaining the braking state of the drum brake 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 front and trailing type vehicle drum brake (hereinafter referred to as drum brake) 10 according to an embodiment of the present invention, in which a bottomed cylindrical brake drum (rotating drum) 12 is removed. 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. .

  Further, as shown in FIG. 1, the drum brake 10 has a cam member 18 having a rectangular cross section that is rotated by a brake operation operation (not shown), and is fixed to a predetermined position on the outer peripheral portion of the backing plate 16. And a pair of first brake shoes (first shoe portions) 22 having a partially arcuate shape and disposed substantially symmetrically with the cam member 18 of the expanding device 20 sandwiched between one end portions thereof, and 24, an anchor member 26 fixed at a position substantially symmetric to the expansion device 20 with respect to the center C1 of the backing plate 16 at the outer peripheral portion of the backing plate 16, and the anchor member 26 between the one end portions. A pair of second brake shoes (second shoe portions) 28 and 30 that are arranged in a substantially symmetrical manner with respect to each other, and the other ends of the second brake shoes 28 and 30 and the first brake. A pair of transmission members 32 and 34 interposed between the other ends of the shoes 22 and 24 are provided.

  As shown in FIGS. 2 to 4, the pair of first brake shoes 22 and 24 and the pair of second brake shoes 28 and 30 are both strip-shaped shoe rim portions (shoe rims) bent into a partial arc shape. 36a and both ends in the width direction of the inner peripheral surface 36b of the shoe rim portion 36a are integrally projected to the inner peripheral side of the backing plate 16 substantially in parallel with the flat flat plate portion 16a located on the inner peripheral portion of the backing plate 16. A shoe body 36 having a pair of shoe web portions (shoe webs) 36c and 36d facing each other and a substantially cylindrical shape fixed between the pair of shoe web portions 36c and 36d of the shoe body 36. The lining 4 is made of a friction material integrally fixed to the outer peripheral surface 36e of the shoe rim portion 36a of the shoe main body 36 with an adhesive or the like. And 0, respectively.

  As shown in FIG. 1 to FIG. 3, the latch pin 38 is a cylindrical shaft portion fitted in a pair of through holes 36 f that pass through an intermediate portion of the pair of shoe web portions 36 c and 36 d of the shoe main body 36. 38a, and a pair of shoe web portions 36c and 36d in the shaft portion 38a, and the end portion protruding from the through hole 36f of the shoe web portion 36d on the backing plate 16 side is formed larger than the diameter of the through hole 36f. A diameter portion 38b, and an end portion protruding from the through hole 36f of the shoe web portion 36c of the shaft portion 38a is caulked to have a larger diameter than that of the through hole 36f, thereby fixing a space between the pair of shoe web portions 36c and 36d. It is to be established.

  As shown in FIGS. 1 and 2, the pair of first brake shoes 22, 24 and the pair of second brake shoes 28, 30 include the pair of first brake shoes 22, 24 and the pair of second brake shoes 28. , 30 is disposed between the pair of shoe web portions 36c and 36d and abuts from the outer peripheral side of the backing plate 16 to the shaft portion 38a of the latch pin 38 installed between the pair of shoe web portions 36c and 36d. A return spring 42 that urges the shaft portion 38a of the latching pin 38 toward the inner peripheral side of the backing plate 16 is latched, and the return spring 42 is formed of a single wire having a circular cross section. As shown in FIG. 1, it is bent into a substantially square shape so as to be hooked on the shaft portion 38a of the stop pin 38. As shown in FIG. 1, when the return spring 42 is hooked on the latch pin 38, the first brake shoe 22 is moved in the direction of the arrow D <b> 1 via the latch pin 38 by the elastic return force of the return spring 42. The first brake shoe 24 is in the direction of the arrow D2 through the latch pin 38, the second brake shoe 28 is in the direction of the arrow D3 through the latch pin 38, and the second brake shoe 30 is in the direction of arrow D3. It is urged in the direction of arrow D4.

  That is, the pair of first brake shoes 22, 24 and the pair of second brake shoes 28, 30 are configured so that one end portions of the pair of first brake shoes 22, 24 are expanded by the elastic return force of the return spring 42. The pair of second brake shoes 28 and 30 is biased in the direction approaching the anchor member 26, and the other end portions of the first brake shoes 22 and 24 are biased in the direction approaching the anchor member 26. And the other ends of the second brake shoes 28 and 30 are biased in a direction approaching the transmission members 32 and 34. As a result, the first brake shoes 22 and 24 and the second brake shoes 28 and 30 are configured so that one end portions of the pair of shoe webs 36c and 36d of the first brake shoes 22 and 24 are cam members by the urging force of the return spring 42. The two brake shoes 28 and 30 are pressed against two locations on the contact surface 18a, and one end portions of the pair of shoe webs 36c and 36d of the second brake shoes 28 and 30 are two locations on the outer peripheral surface of the torque receiving shaft portion 26c of the anchor member 26. And the postures of the first brake shoes 22 and 24 and the second brake shoes 28 and 30 disposed on the backing plate 16 are maintained. The force that is biased in the direction in which one end of the first brake shoe 22 approaches the cam member 18 and the force that is biased in the direction in which the other end of the first brake shoe 22 approaches the transmission member 32 are: This is a component force of the force that urges the first brake shoe 22 in the direction of the arrow D <b> 1 by the elastic return force of the return spring 42. Further, the force urged in the direction in which one end of the first brake shoe 24 approaches the cam member 18 and the force urged in the direction in which the other end of the first brake shoe 24 approaches the transmission member 34 are: This is a component force of the force that urges the first brake shoe 24 in the direction of the arrow D2 by the elastic return force of the return spring 42. Further, the force urged in the direction in which one end of the second brake shoe 28 approaches the anchor member 26 and the force urged in the direction in which the other end of the second brake shoe 28 approaches the transmission member 32 are: This is a component of the force that urges the second brake shoe 28 in the direction of the arrow D3 by the elastic return force of the return spring 42. Further, the force urged in the direction in which one end of the second brake shoe 30 approaches the anchor member 26 and the force urged in the direction in which the other end of the second brake shoe 30 approaches the transmission member 34 are: This is a component of the force that urges the second brake shoe 30 in the direction of the arrow D4 by the elastic return force of the return spring 42.

  As shown in FIGS. 1 and 2, the transmission members 32 and 34 include a pair of shoe web portions 36 c and 36 d at the other end portions of the first brake shoes 22 and 24 and the other end portions of the second brake shoes 28 and 30. Columnar shaft portions 32a and 34a interposed between the pair of shoe web portions 36c and 36d, and the diameters of both end portions of the shaft portions 32a and 34a are larger than the diameter of the cross section of the shaft portions 32a and 34a. A pair of disk-shaped large-diameter portions 32 b and 34 b are provided, and the shaft portions 32 a and 34 a of the transmission members 32 and 34 are connected to the first brake shoes 22 and 24 by the elastic return force of the return spring 42. Between the other end of the second brake shoe 28 and the other end of the second brake shoe 28 and 30.

  As shown in FIGS. 1 and 6, the pair of shoe web portions 36 c and 36 d at the other end portions of the pair of first brake shoes 22 and 24 are connected to the shaft portions 32 a of the transmission members 32 and 34 by the elastic return force of the return spring 42. And 34a, the pair of first brake shoes 22 and 24 have a pair of shoe web portions 36c and 36d at the other end of the pair of first brake shoes 22 and 24. In order to prevent the other end portions of the pair of first brake shoes 22 and 24 from moving toward the inner periphery side of the backing plate 16 at the other end portions of the first brake shoes 22 and 24. The shoe web portions 36c and 36d approach the other end portions of the second brake shoes 28 and 30. A first projecting portion 36g projecting in the direction and a pair of shoe web portions 36c and 36d on the inner peripheral side of the backing plate 16 at the other end of the pair of first brake shoes 22 and 24, and the first brake A flat first guide portion 36h for allowing the other end portions of the shoes 22 and 24 to move toward the outer peripheral side of the backing plate 16, and a pair of the other end portions of the pair of first brake shoes 22 and 24. The shoe web portions 36c and 36d are bent to have substantially the same curvature as that of the outer peripheral surfaces of the shaft portions 32a and 34a of the transmission members 32 and 34 that connect the end surface of the first projecting portion 36g and the end surface of the first guide portion 36h. And a curved surface 36i.

  Further, as shown in FIGS. 1 and 6, the pair of shoe web portions 36 c and 36 d at the other end of the pair of second brake shoes 28 and 30 are connected to the shafts of the transmission members 32 and 34 by the elastic return force of the return spring 42. At the position abutted against the portions 32a and 34a, the other end portions of the pair of second brake shoes 28 and 30 are connected to the pair of shoe web portions 36c and 36d at the other end portions and the shaft portions 32a of the transmission members 32 and 34, respectively. A concave portion 36j is formed so as to bend to a curvature substantially the same as the curvature of the outer peripheral surface of 34a and 34a, and a part of the outer peripheral surface of the shaft portions 32a and 34a of the transmission members 32 and 34 abuts.

  As shown in FIGS. 1 and 2, the anchor member 26 has a fixed portion 26a fixed between one end portions of the pair of second brake shoes 28 and 30 of the backing plate 16, and a pair of the fixed portions 26a. Torque receiving shaft portion (shaft portion) 26c erected in a cylindrical shape in a direction away from the backing plate 16 from the seating surface 26b on which one end portions of the second brake shoes 28 and 30 are seated, and the torque receiving shaft portion 26c is provided with a disk-shaped large-diameter portion (large-diameter head portion) 26d formed larger in diameter than the cross-sectional diameter of the torque receiving shaft portion 26c, and an elastic return force of the return spring 42 Thus, the pair of shoe web portions 36c and 36d at one end portions of the pair of second brake shoes 28 and 30 are brought into contact with two locations on the outer peripheral surface of the torque receiving shaft portion 26c, respectively. As a result, the second brake shoes 28 and 30 and the first brake shoes 22 and 24 connected to the other ends of the second brake shoes 28 and 30 via the transmission members 32 and 34 are in the direction of the center C1 of the backing plate. The brake drum 12 is positioned in the circumferential direction.

  As shown in FIGS. 1 and 5, the pair of shoe web portions 36 c and 36 d at one end of the pair of second brake shoes 28 and 30 are connected to the torque receiving shaft portion 26 c of the anchor member 26 by the elastic return force of the return spring 42. At a position in contact with the outer peripheral surface, the pair of second brake shoes 28 and 30 has an outer periphery of the backing plate 16 of the pair of shoe web portions 36c and 36d at one end of the pair of second brake shoes 28 and 30. And a pair of second brake shoes 28 and 30 at one end of the pair of second brake shoes 28 and 30 to prevent the one end of the pair of second brake shoes 28 and 30 from moving toward the inner peripheral side of the backing plate 16. Second projecting portion 3 projecting in a direction in which the shoe web portions 36c and 36d of each of the shoe webs approach each other k, and a pair of shoe web portions 36c and 36d at one end of the pair of second brake shoes 28 and 30 on the inner peripheral side of the backing plate 16, and the ends of the second brake shoes 28 and 30 are backed. A flat second guide portion 36l for allowing movement to the outer peripheral side of the plate 16, and a second projecting portion of the pair of shoe web portions 36c and 36d at one end of the pair of second brake shoes 28 and 30 There is provided a curved surface 36m that is curved with substantially the same curvature as the curvature of the outer peripheral surface of the torque receiving shaft portion 26c that connects the end surface of 36k and the end surface of the second guide portion 36l.

  As shown in FIGS. 2 to 4, the backing plate 16 includes the above-described flat plate portion 16a and the backing plate 16 of the pair of shoe web portions 36c and 36d in the pair of first brake shoes 22 and 24 from the flat plate portion 16a. A pair of first protrusions 16b protruding toward the respective shoe web portions 36d, and a pair of shoe web portions 36c and 36d in the pair of second brake shoes 28 and 30 from the flat plate portion 16a on the backing plate 16 side. A pair of second protrusions 16c protruding toward the shoe web portions 36d are integrally provided.

  Further, as shown in FIGS. 2 to 4, the front end portion of the first protrusion 16b of the backing plate 16 has a flat surface 16d substantially parallel to the flat plate portion 16a and the first brake shoes 22 and 24 on the flat surface 16d. A concave portion 16e is provided to prevent the large-diameter portion 36b of the latch pin 38 from coming into contact. Further, a flat surface 16f substantially parallel to the flat plate portion 16a and a large-diameter portion 38b of the latch pin 38 of the second brake shoes 28 and 30 are formed on the front end portion of the second protrusion 16c of the backing plate 16 and the flat surface 16f. In order to prevent contact, a recessed portion 16g that is recessed is provided.

  As shown in FIGS. 2 to 4, the first protrusion 16 b and the second protrusion 16 c of the backing plate 16 approach the shoe web 26 d of the first brake shoes 22, 24 and the second brake shoes 28, 30. For example, when the first brake shoes 22, 24 and the second brake shoes 28, 30 vibrate in the direction of the axle of the vehicle body due to external forces due to vibrations while the vehicle is running, the backing is performed with a relatively small swing width. The vibrations are preferably received by the flat surfaces 16 d and 16 f of the first protrusion 16 b and the second protrusion 16 c of the plate 16 and the large-diameter portion 26 b of the anchor member 26.

  As shown in FIG. 2, the expansion device 20 includes a fixing member 44 fixed between one ends of the pair of first brake shoes 22 and 24 of the backing plate 16, and a pair of first members of the fixing member 11. A columnar shaft member 46 fitted into a columnar through hole 44b penetrating through a seating surface 44a on which one end portions of the brake shoes 22 and 24 are seated, and a pair fixed to the shaft member 46. And the above-described cam member 18 disposed between one end portions of the first brake shoes 22 and 24, and one end portions of the pair of first brake shoes 22 and 24 by the elastic return force of the return spring 42. Is brought into contact with the cam member 18, and the shaft member 46 is rotated around the axis C2 by a brake operation operation (not shown).

  According to the drum brake 10 configured as described above, for example, when the shaft member 46 of the expansion device 20 is rotated by a brake operation operation such as depression of a brake pedal, the cam member 18 is rotated around the axis C2 of the shaft member 46. And one end of the pair of first brake shoes 22 and 24 is expanded, that is, moved in the directions of arrows B1 and B2, respectively. In the following, the movement of the first brake shoes 22 and 24 and the second brake shoes 28 and 30 when one end of the pair of first brake shoes 22 and 24 is expanded by the expansion device 20 will be described with reference to FIGS. 11 will be described. Further, it is assumed that the brake drum 12 rotates in the arrow A3 direction. The drum brake 10 of this embodiment is a leading / trailing type, and the left and right sides of the pair of first brake shoes 22 and 24 and the pair of second brake shoes 28 and 30 are the same as shown in FIG. Therefore, in the following, description of the movement of the first brake shoes 22 and 24 and the second brake shoes 28 and 30 when the brake drum 12 rotates in the direction opposite to the arrow A3 direction will be omitted.

  As shown in FIG. 7, when the one end portions of the pair of first brake shoes 22 and 24 are moved in the directions of arrows B1 and B2 against the urging force of the return spring 42 by the expansion device 20, respectively. As shown in FIG. 8, the other end portions of the brake shoes 22 and 24 are connected to the first guide portion 36h from the position where the first projecting portion 36g at the other end abuts the shaft portion 32a of the transmission member 32. The backing plate 16 is moved in the direction of the arrow B3 while sliding on the outer peripheral surface of 32a, and the lining 40 at the other end of the pair of first brake shoes 22 contacts the inner peripheral surface 14 of the brake drum 12. Touched. 8 is moved to the outer peripheral side of the backing plate 16 by the spreading device 20 so that the other end of the first brake shoe 22 shown in FIG. The state which contact | abutted to the internal peripheral surface 14 is shown.

  As shown in FIG. 9, when the lining 40 at the other end of the first brake shoe 22 comes into contact with the inner peripheral surface 14 of the brake drum 12, the first brake shoe 22 rotates with the brake drum 12, and the brake drum 12 The first brake shoe 22 rotates in the direction of arrow B4 around the shaft portion 32a of the transmission member 32 so that one end of the first brake shoe 22 approaches the inner peripheral surface 14 of the brake drum 12 by the accompanying force F1. Thus, between one end and the other end of the first brake shoe 22, that is, substantially the entire outer peripheral surface of the lining 40 of the first brake shoe 22 is in close contact with the inner peripheral surface 14 of the brake drum 12. It is made to contact.

  As shown in FIG. 9, when the first brake shoe 22 is rotated together with the brake drum 12, the rotating force F <b> 1 is transmitted to the second brake shoe 28 via the transmission member 32. Therefore, as shown in FIG. 10, one end portion of the second brake shoe 28 slides the second guide portion 36 l at the one end portion on the outer peripheral surface of the torque receiving shaft portion 26 c of the anchor member 26, and thereby the outer periphery of the backing plate 16. The lining 40 at one end of the second brake shoe 28 is brought into contact with the inner peripheral surface 14 of the brake drum 12. In addition, the second brake shoe 28 shown by the alternate long and short dash line shown in FIG. 10 causes the one end portion of the second brake shoe 28 to move to the outer peripheral side of the backing plate 16 when the first brake shoe 22 rotates with the brake drum 12. It shows a state in which it has moved and is in contact with the inner peripheral surface 14 of the brake drum 12.

  As shown in FIG. 11, when the lining 40 at one end of the second brake shoe 28 comes into contact with the inner peripheral surface 14 of the brake drum 12, the second brake shoe 28 rotates with the brake drum 12, and the brake drum The second brake shoe 28 is moved around the torque receiving shaft 26c of the anchor member 26 by the arrow E2 so that the other end of the second brake shoe 28 approaches the inner peripheral surface 14 of the brake drum 12 by the rotating force F2 of the twelve. And the substantially entire surface of the outer peripheral surface of the lining 40 of the second brake shoe 28 entirely covers the inner peripheral surface 14 of the brake drum 12. It is made to contact | abut so that it may closely_contact | adhere.

  Therefore, the self-boosting force acts on substantially the entire outer peripheral surface of the lining 40 of the first brake shoe 22 and the second brake shoe 28, and the substantially entire surface of the lining 40 of the first brake shoe 22 is within the brake drum 12. The surface pressure distribution that presses the peripheral surface 14 becomes substantially uniform, and the surface pressure distribution that the substantially entire surface of the lining 40 of the second brake shoe 28 presses the inner peripheral surface 14 of the brake drum 12 becomes substantially uniform, The rotation of the brake drum 12 is braked. When the cam member 18 of the expansion device 20 is returned to the original position shown in FIG. 1 and the brake operation operation is released, the pair of first brake shoes 22 and 24 and the pair of first brake shoes 22 and 24 are restored by the elastic return force of the return spring 42. The second brake shoes 28 and 30 are returned to their original positions shown in FIG.

  According to the drum brake 10 of the present embodiment, the pair of brake shoes are positioned on the side of the expansion device 20 of the backing plate 16 and are urged by the return spring 42 in a direction in which one end thereof approaches the expansion device 20. A pair of first brake shoes 22 and 24 having a partially arcuate shape, and one end portion of the first brake shoes 22 and 24 on the anchor member 26 side of the backing plate 16 are arranged on the outer peripheral surface of the torque receiving shaft portion 26c of the anchor member 26 by the return spring 42. A pair of second brake shoes 28 and 30 having a partial arc shape biased in the approaching direction, the other end portions of the second brake shoes 28 and 30, and the other end portions of the first brake shoes 22 and 24 The first brake shoes 22 and 24 and the second brake shoes 28 and 30 are rotated relative to each other. And the other ends of the first brake shoes 22 and 24 are rotated together with the first brake shoes 22 and 24 while allowing the other ends of the second brake shoes 28 and 30 to move relative to the outer peripheral side of the backing plate 16. A pair of transmission members 32 and 34 for transmitting the force F1 to the second brake shoes 28 and 30 are provided. For this reason, when the one end part of a pair of 1st brake shoes 22 and 24 moves to the outer peripheral side of the backing plate 16 by the expansion apparatus 20, the other end part of the pair of 1st brake shoes 22 and 24 becomes the backing plate 16 side. Moving to the outer peripheral side, the other end portions of the pair of first brake shoes 22 and 24 are brought into contact with the inner peripheral surface 14 of the brake drum 12. As a result, the first brake shoe 22 transmits the transmission member so that one end of the first brake shoe 22 approaches the inner peripheral surface 14 of the brake drum 12 by the accompanying force F1 of the first brake shoe 22 from the brake drum 12. 32, the first brake shoe 22 is brought into contact with the inner peripheral surface 14 of the brake drum 12 so that the one end and the other end of the lining 40 of the first brake shoe 22 are in close contact with each other. At the same time, the second brake shoe 28 is rotated around the torque receiving shaft portion 26 c of the anchor member 26 and brought into contact with the inner peripheral surface 14 of the brake drum 12, so that the first brake at the time of braking of the drum brake 10 is performed. The contact area where the shoe abuts against the inner peripheral surface 14 of the brake drum 12 is the same as that of the conventional brake shoes 110 and 120. A surface that is larger than the contact area that is in contact with the inner peripheral surface 140 a of 0 and that presses the inner peripheral surface 14 of the brake drum 12 between one end and the other end of the first brake shoe 22. The pressure distribution becomes uniform, and the braking force of the drum brake 10 is improved as compared with the conventional case. Further, when the drum brake 10 is braked, the first and second brake shoes 22 and 24 are brought into contact with each other so that the one end portion and the other end portion thereof are in close contact with the inner peripheral surface 14 of the brake drum 12. Uneven wear of the lining 40 of the first brake shoes 22 and 24 is suppressed, and the durability of the first brake shoes 22 and 24 is preferably improved.

  Further, according to the drum brake 10 of the present embodiment, the first brake shoes 22 and 24 are arranged on the outer periphery of the backing plate 16 from a position where they are in contact with the transmission members 32 and 34 at the other ends of the first brake shoes 22 and 24. A first projecting portion 36g that is formed on the other end side of the second brake shoes 28 and 30 to prevent the transmission members 32 and 34 from moving toward the outer peripheral side of the backing plate 16; The first brake shoes 22 and 24 are formed on the inner peripheral side of the backing plate 16 from the position where the transmission members 32 and 34 on the other end of the first brake shoes 22 and 24 abut, and the transmitting members 32 and 34 move to the inner peripheral side of the backing plate 16. And a flat first guide portion 36h for allowing this. For this reason, when the one end part of a pair of 1st brake shoes 22 and 24 moves to the outer peripheral side of the backing plate 16 by the expansion apparatus 20, the other end part of the pair of 1st brake shoes 22 and 24 will also be the other end part. The flat first guide portion 36h at the other end from the position where the first projecting portion 36g of the first contact portion 36g contacts the outer peripheral surface of the shaft portions 32a and 34a of the transmission members 32 and 34 is changed to the shaft portions 32a and 32a of the transmission members 32 and 34. Since it is moved to the outer peripheral side of the backing plate 16 while sliding on the outer peripheral surface of 34a, the entire area between one end portion and the other end portion of the first brake shoe 22 is easily brought into contact with the inner peripheral surface 14 of the brake drum 12. It becomes possible.

  Further, according to the drum brake 10 of the present embodiment, the second brake shoes 28 and 30 are in contact with the outer peripheral surface of the torque receiving shaft portion 26c of the anchor member 26 at one end of the second brake shoes 22 and 24. Is formed on the outer peripheral side of the backing plate 16, and the second protrusions projecting toward the anchor member 26 in order to prevent the end portions of the second brake shoes 28 and 30 from moving toward the inner peripheral side of the backing plate 16. The portion 36k is formed on the inner peripheral side of the backing plate 16 from the position where the outer peripheral surface of the shaft portion 26c of the anchor member 26 at one end of the second brake shoes 28 and 30 abuts. A flat second guide portion 36 l for allowing one end of the plate to move to the outer peripheral side of the backing plate 16.For this reason, when the first brake shoe 22 is rotated together with the brake drum 12 during braking of the drum brake 10, one end portion of the second brake shoe 28 is flat at the one end portion via the transmission member 32. 36 l is moved to the outer peripheral side of the backing plate 16 while sliding on the outer peripheral surface of the shaft portion 26 c of the anchor member 26, and one end portions of the second brake shoes 28 and 30 abut against the inner peripheral surface 14 of the brake drum 12. . As a result, the second brake shoe 28 is rotated together with the brake drum 12 so that the other end of the second brake shoe 28 approaches the inner peripheral surface 14 of the brake drum 12 by the accompanying force F2 of the brake drum 12. Since the second brake shoe 28 rotates around the torque receiving shaft portion 26 c of the anchor member 26, the space between one end and the other end of the second brake shoes 28 and 30 is further increased on the inner peripheral surface 14 of the brake drum 12. The contact area where the brake shoes, that is, the first brake shoe 22 and the second brake shoe 28 are in contact with the inner peripheral surface 14 of the brake drum 12 when the drum brake 10 is braked. The second brake shoe 2 is preferably larger than the conventional brake shoes 110 and 120, and the second brake shoe 2 Between one and the other ends of the surface pressure distribution for pressing the inner circumferential surface 14 of the brake drum 12 becomes uniform, the braking force of the drum brake 10 is improved more as compared with the prior art. Further, when the drum brake 10 is braked, the one end and the other end of the second brake shoes 28 and 30 are brought into contact with the inner peripheral surface 14 of the brake drum 12 so as to be in close contact with each other. Uneven wear of the lining 40 of the first brake shoes 28 and 30 is suppressed, and the durability of the second brake shoes 28 and 30 is preferably improved.

  Further, according to the drum brake 10 of the present embodiment, the anchor member 26 has a large diameter portion (large diameter head portion) 26d and a torque receiving shaft portion (shaft portion) 26c having a smaller diameter than the large diameter portion 26d. The first brake shoes 22, 24 and the second brake shoes 28, 30 are erected on the backing plate 16, and the belt plate-like shoe rim part (shoe rim) 36 a bent into a partial arc shape, The shoe rim portion 36a has a pair of shoe web portions (shoe webs) 36c and 36d that are opposed to each other and project toward the inner peripheral side of the backing plate 16 from both ends in the width direction of the inner peripheral surface 36b. The return spring 42 includes an end portion of a pair of shoe web portions 36c and 36d of the second brake shoes 28 and 30 as anchors. Those pressed against the torque bearing shaft portion 26c of the timber 26. For this reason, the second brake shoes 28 and 30 are configured so that the one end portions of the pair of shoe web portions 36c and 36d of the second brake shoes 28 and 30 are the torque receiving shaft portions 26c of the anchor member 26 by the urging force of the return spring 42. Since the posture of the second brake shoes 28 and 30 disposed on the backing plate 16 is maintained by being pressed against two locations on the outer peripheral surface of the shoe, the shoe used to maintain the posture of the conventional brake shoe is maintained. A hold-down device can be dispensed with.

  Further, according to the drum brake 10 of the present embodiment, in the first brake shoes 22 and 24 and the second brake shoes 28 and 30, the pair of shoe web portions 36c and 36d includes the pair of shoe web portions 36c and 36d. A return pin 42 is provided between the pair of shoe web portions 36c and 36d in the first brake shoes 22, 24 and the second brake shoes 28, 30. One wire rod is arranged so as to abut against the latching pin 38 installed between the pair of shoe web portions 36c and 36d from the outer peripheral side of the backing plate 16 and to be urged toward the inner peripheral side of the backing plate 16 It is composed of. For this reason, the return spring 42 is latched by the latch pin 38, so that the return spring 42 is interposed between the pair of shoe web portions 36 c and 36 d in the pair of first brake shoes 22, 24 and the pair of second brake shoes 28, 30. Therefore, the space of the inner peripheral portion of the backing plate 16 is suitably widened compared to a conventional coiled return spring that is stretched between a pair of brake shoes, and the drum brake 10 Since it becomes difficult for the operator to come into contact with the return spring 42 when mounting it on the vehicle body side member, the drum brake 10 can be easily attached.

  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 drum brake 10 of the present embodiment, the drum brake 10 is used as a drum brake for a service brake while the vehicle is running, but may be used as a drum brake for a parking brake, for example.

  Further, in the drum brake 10 of the present embodiment, the expansion device 20 is configured such that one end of the pair of first brake shoes 22 and 24 is expanded by rotating the cam member 18. The expansion device 20 may be anything that expands one end of the pair of first brake shoes 22 and 24, and may be a wheel cylinder, for example.

  In the drum brake 10 of the present embodiment, the pair of brake shoes includes a pair of first brake shoes 22 and 24, a pair of second brake shoes 28 and 30, and a pair of transmission members 32 and 34. However, for example, the first brake shoes 22, 24 and the second brake shoes 28, 30 in which the lengths in the longitudinal direction of the first brake shoes 22, 24 and the second brake shoes 28, 30 are shortened are manufactured. A pair of third brake shoes having one end and the other end having substantially the same shape at one end and the other end of the second brake shoes 28 and 30 are connected to one end of the second brake shoes 28 and 30 and the anchor member 26. And a pair of transmissions between the other end of the third brake shoe and one end of the second brake shoes 28 and 30. Material may be interposed. That is, the number of brake shoes of the drum brake 10 of this embodiment is not limited.

  In the drum brake 10 of the present embodiment, the pair of transmission members 32 and 34 are sandwiched between the other end portions of the pair of first brake shoes 22 and 24 and the other end portion of the pair of second brake shoes 28 and 30. However, the transmission members 32 and 34 may be fixed to the other ends of the second brake shoes 28 and 30 by, for example, welding. Furthermore, a protrusion projecting in a substantially arc shape like the cross section of the shaft portions 32 a and 34 a of the transmission members 32 and 34 is integrally provided at the other end of the second brake shoes 28 and 30, and the protrusion is provided as the transmission member 32. And 34 may be substituted.

  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: Drum brake 12: Brake drum (rotary drum)
14: Inner circumferential surface of brake drum 16: Backing plate 20: Expansion device 22, 24: A pair of first brake shoes (first shoe part)
26: Anchor member 26b: Large diameter portion (large diameter head)
26c: Torque bearing shaft (shaft)
28, 30: A pair of second brake shoes (second shoe part)
32, 34: A pair of transmission members 36a: Shoe rim portions (shoe rims)
36c, 36d: A pair of shoe web parts (shoe webs)
36g: 1st protrusion part 36h: 1st guide part 36k: 2nd protrusion part 36l: 2nd guide part 38: Stop pin 42: Return spring

Claims (5)

A pair of arcuate brake shoes disposed on the backing plate so as to be expandable, and one end of the pair of brake shoes, the one end of the pair of brake shoes being separated from each other An expansion device that expands to the outer peripheral side of the backing plate, and the pair of brake shoes slidably contact the inner peripheral surface of the rotating drum that rotates together with the vehicle wheels by the expansion device, and one of the pair of brake shoes A drum brake having an anchor member that is received at the other end,
The pair of brake shoes is a pair of first shoe portions that are located on the side of the expansion device of the backing plate and have a partial arc shape whose one end is urged by a return spring in a direction approaching the expansion device. A pair of second shoe portions that are located on the anchor member side of the backing plate and have a partial arc shape whose one end portion is biased in a direction approaching the anchor member by a return spring; and the second shoe portion Between the other end portion of the first shoe portion and the other end portion of the first shoe portion, the first shoe portion and the second shoe portion are relatively rotated, and the other end portion of the first shoe portion is the second shoe portion. And a pair of transmission members that transmit the follower force of the first shoe portion to the second shoe portion while allowing relative movement to the outer peripheral side of the backing plate with respect to the other end portion of the backing plate. Drum brake that.   The first shoe portion is formed on the outer peripheral side of the backing plate from a position where the other end portion of the first shoe portion contacts the transmitting member, and the transmitting member moves to the outer peripheral side of the backing plate. Formed on the inner peripheral side of the backing plate from the position where the first projecting portion projecting to the other end portion side of the second shoe portion and the transmission member of the other end portion of the first shoe portion abut to prevent The drum brake according to claim 1, further comprising a flat first guide portion for allowing the transmission member to move toward an inner peripheral side of the backing plate.   The second shoe part is formed on the outer peripheral side of the backing plate from a position where the second shoe part comes into contact with the anchor member, and the one end part of the second shoe part is on the inner peripheral side of the backing plate. A second projecting portion projecting to the anchor member side to prevent movement to the anchor member side, and a position where the anchor member of one end portion of the second shoe portion abuts on the inner peripheral side of the backing plate, The drum brake according to claim 1 or 2, further comprising a flat second guide portion for allowing one end portion of the second shoe portion to move toward the outer peripheral side of the backing plate. The anchor member has a large-diameter head and a shaft portion having a smaller diameter than the large-diameter head, and is erected on the backing plate.
The first shoe part and the second shoe part are integrally formed from a band plate-like shoe rim bent in a partial arc shape and both ends in the width direction of the inner peripheral surface of the shoe rim toward the inner peripheral side of the backing plate. And a pair of shoe webs facing each other and projecting by a predetermined amount.
The drum brake according to any one of claims 1 to 3, wherein the return spring presses one end portion of a pair of shoe webs of the second shoe portion against a shaft portion of the anchor member. In the first shoe portion and the second shoe portion, the pair of shoe webs includes a latch pin fixed between the pair of shoe webs,
The return spring is disposed between the pair of shoe webs in the first shoe portion and the second shoe portion, and comes into contact with a latch pin laid between the pair of shoe webs from the outer peripheral side. The drum brake according to claim 4, wherein the drum brake is bent from one wire so as to be biased toward the circumferential side.

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