JP2014109312A - Drum brake - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a drum brake in which an abutting area where brake shoes abut on a rotating drum at braking becomes large, and a brake force is improved.SOLUTION: In a pair of brake shoes 26, 28, ends of a pair of first shoe parts 52, 58 and ends of a pair of second shoe parts 54, 60 are rotatably connected to each other with a pair of connecting pins 50, 56. For example in the brake shoe 26, since the abutting area where the first shoe part 52 and the second shoe part 54 abut on an internal peripheral face 12a of a brake drum 12 at braking becomes large compared with an integrated brake shoe, a surface pressure distribution for pressing the internal peripheral face 12a of the brake drum 12 by the first shoe part 52 and the second shoe part 54 becomes uniform, and the brake shoe parts are made to abut on the whole surface so as to be adhered thereto, the brake force of the drum brake 10 is improved, the distorted wear of the first shoe part 52 and the second shoe part 54 is suppressed, and the durability of the drum braked 10 is suitably improved.

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. 3, 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 are slidably in contact with the inner peripheral surface 140a of the rotating drum 140 that rotates together with the vehicle wheel, and an anchor 150 that receives the other end of one of the pair of brake shoes 110 and 120 is provided. In addition, two concentric circles indicated by a one-dot chain line in FIG. 3 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, for example, as shown in FIG. When the lever is rotated in the direction of the arrow A2, the pair of brake shoes 110 and 120 are separated from each other by the cam member 130a, and the shaft center C of the anchor 150 is separated. Rotate around. For this reason, the brake shoe 110 abuts on the inner peripheral surface 140a of the rotating drum 140 and receives a follow-up force from the rotating drum 140, and the other end of the brake shoe 110 is received by the anchor 150 and the rotating drum 140 is received. 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. -150 rotates about the axis C of 150, so that only a part of the brake shoes 110 and 120 substantially contacts the inner peripheral surface 140a of the rotary drum 140. The brake shoes 110 and 120 and the rotary drum 140 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 object of the present invention is to increase the 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, compared to the conventional brake force of the drum brake. It is to provide an improved 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 spreading 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 one other end of the pair of brake shoes abuts each other. And a pair of return springs stretched between one end and the other end of the pair of brake shoes, and (b) the pair of brake shoes includes (b- 1) 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; and (b-2) a partial arc that is located on the anchor side of the backing plate. A pair of second shoe portions, and (b-3) a pair of connections for rotatably connecting between the ends of the pair of first shoe portions and the pair of second shoe portions that are close to each other. It is in having a pin.

  According to the drum brake of the present invention, (b) the pair of brake shoes is (b-1) a pair of first shoe portions that are located on the side of the expansion device of the backing plate and form a partial arc shape; (b-2) a pair of second shoe portions positioned on the anchor side of the backing plate and having a partial arc shape; and (b-3) the pair of first shoe portions and the pair of second shoe portions. A pair of connecting pins that rotatably connect the end portions on the sides approaching each other are provided. For this reason, when the pair of first shoe portions are moved to the outer peripheral side of the backing plate by the expanding device and brought into contact with the inner peripheral surface of the rotating drum, the accompanying force from the rotating drum causes The one first shoe portion is rotated around the connecting pin, and the one end portion and the other end portion of the first shoe portion are brought into contact with each other so as to be in close contact with the inner peripheral surface of the rotating drum. At the same time, the second shoe portion is rotated around the anchor by the follower force transmitted from the first shoe portion, and is brought into close contact with the inner peripheral surface of the rotating drum. For this reason, the contact area where the first shoe portion and the second shoe portion abut against the inner peripheral surface of the rotating drum during braking of the drum brake is larger than that of a conventional integrated brake shoe, and The surface pressure distribution that presses the inner peripheral surface of the rotating drum is uniform between the one end portion and the other end portion of the first shoe portion and the second shoe portion, and the braking force of the drum brake is compared with the conventional one. Improve. Further, when the drum brake is braked, the first shoe portion and the second shoe portion are brought into contact with the inner peripheral surface of the rotary drum so as to be in full contact with each other. The uneven wear of the friction material provided on the outer peripheral surface of the shoe portion is suppressed, and the durability of the drum brake is preferably improved.

  Here, preferably, (c) the first shoe portion and the second shoe portion are formed from a band plate-like shoe rim bent in a partial arc shape and a central portion in the width direction of the inner peripheral surface of the shoe rim. A plate-like shoe web integrally projecting a predetermined length toward the inner peripheral side of the backing plate, (d) the shoe web of the first shoe portion and the shoe of the second shoe portion The end portions of the webs that are close to each other are rotatably connected by the connecting pin in a surface contact state that is overlapped with each other in the thickness direction. In this way, the first shoe portion and the second shoe portion are reliably coupled with each other so as to be relatively rotatable with a simple configuration, so that the reliability of the drum brake is enhanced.

  Preferably, (e) the portions of the shoe web of the first shoe portion and the shoe web of the second shoe portion which are overlapped with each other are locally shifted by half the plate thickness in the thickness direction. The positions of the mating surfaces that are in surface contact with each other are located within the thickness of the shoe web. In this way, the accompanying force transmitted from the shoe web of the first shoe portion to the shoe web of the second shoe portion is the force of the first shoe portion protruding from the central portion in the width direction of the inner peripheral surface. Similarly, it is transmitted from the shoe web to the shoe web of the second shoe portion projecting from the central portion in the width direction of the inner peripheral surface, so that it is attached to the outer peripheral surfaces of the first shoe portion and the second shoe portion. Uneven wear of the friction material is more preferably prevented.

The gist of the second invention for achieving the above object is as follows: (a) a pair of brake shoes having an arc shape disposed on the backing plate so as to be expandable, and one end of the pair of brake shoes. An expansion device that is disposed between the two parts and expands to the outer peripheral side of the backing plate by separating one end of the pair of brake shoes from each other, and one other end of the pair of brake shoes A drum brake comprising an anchor to be contacted and a pair of return springs respectively stretched between one end and the other end of the pair of brake shoes,
(f) The pair of brake shoes are (f-1) a pair of first shoe portions that are located on the side of the expansion device of the backing plate and form a partial arc shape, and (f-2) the backing plate A pair of second shoe portions that are located on the anchor side and have a partial arc shape; and (f-3) between the ends of the pair of first shoe portions and the pair of second shoe portions that are close to each other. And a pair of biasing devices that allow relative rotation while biasing each other so as to approach each other while maintaining the contact state between the end portions.

  According to the drum brake of the second invention, (f) the pair of brake shoes is (f-1) 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. And (f-2) a pair of second shoe portions positioned on the anchor side of the backing plate and forming a partial arc shape, and (f-3) the pair of first shoe portions and the pair of second shoes. A pair of urging devices that allow relative rotation while urging the end portions of the portions that are close to each other so as to approach each other and maintaining the contact state between the end portions; Yes. For this reason, when the pair of first shoe portions are moved to the outer peripheral side of the backing plate by the expanding device and brought into contact with the inner peripheral surface of the rotating drum, the accompanying force from the rotating drum causes The one first shoe portion rotates around a contact point with the second shoe portion so that the end portion of the first shoe portion and the other end portion are in close contact with the inner peripheral surface of the rotating drum. At the same time, the second shoe portion is rotated around the anchor by the follower force transmitted from the first shoe portion, and is brought into close contact with the inner peripheral surface of the rotating drum. For this reason, the contact area where the first shoe portion and the second shoe portion abut against the inner peripheral surface of the rotating drum during braking of the drum brake is larger than that of a conventional integrated brake shoe, and The surface pressure distribution that presses the inner peripheral surface of the rotating drum is uniform between the one end portion and the other end portion of the first shoe portion and the second shoe portion, and the braking force of the drum brake is compared with the conventional one. Improve. Further, when the drum brake is braked, the first shoe portion and the second shoe portion are brought into contact with the inner peripheral surface of the rotary drum so as to be in full contact with each other. The uneven wear of the friction material provided on the outer peripheral surface of the shoe portion is suppressed, and the durability of the drum brake is preferably improved.

  Here, preferably, (g) the pair of urging devices are a pair of coil springs respectively stretched between the pair of first shoe portions and the pair of second shoe portions. Accordingly, the relatively pivotable connection between the first shoe portion and the second shoe portion is achieved by the coil spring that allows relative rotation while maintaining a contact state between the pair of first shoe portions and the second shoe portion. Has the advantage of being easily configured.

  Preferably, (h) end portions of the first shoe portion and the second shoe portion which are close to each other are located on the inner peripheral side of the backing plate and contact each other, and the biasing device A first abutting surface that receives an urging force and an outer peripheral side of the backing plate, the first abutting against the urging force of the urging device by abutting each other during braking when the pair of brake shoes are expanded. And a second contact surface that functions as a rotation center point of relative rotation of the shoe portion and the second shoe portion. For this reason, since the first contact surface and the second contact surface are provided at the end portions of the first shoe portion and the second shoe portion that are close to each other, The circumferential position of the second abutment surface can be made different, and there is an advantage that the end portions of the first shoe portion and the second shoe portion that are close to each other are hardly displaced in the radial direction.

  Preferably, (i) the first shoe portion of one brake shoe and the first shoe portion of the other brake shoe of the pair of brake shoes have the same shape, and The second shoe portion of one brake shoe and the second shoe portion of the other brake shoe of the pair of brake shoes have the same shape. In this way, between the first shoe part of one brake shoe and the first shoe part of the other brake shoe, the second shoe part of one brake shoe and the other brake of the pair of brake shoes. There is an advantage that the number of types of parts can be reduced because parts can be interchanged with each other with the second shoe portion of the shoe.

  Preferably, (j) the pair of return springs includes an end portion of the first shoe portion of the one brake shoe on the side of the expansion device and the expansion device of the first shoe portion of the other brake shoe. A first return spring stretched between an end on the side, an end on the anchor side of the second shoe portion of the one brake shoe, and an anchor side of the second shoe portion of the other brake shoe It consists of a 2nd return spring stretched between end parts. In this way, regardless of the urging force of the first return spring and the second return spring, the pair of first shoe portions abuts on the expansion device during non-braking and is positioned accurately, and the pair of second shoes The shoe portion comes into contact with the anchor and is accurately positioned.

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. 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. It is a front view which shows the drum brake of the other Example of this invention. FIG. 6 is a sectional view taken along line VI-VI in FIG. 5.

  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 is a front view showing a leading and trailing vehicle drum brake (hereinafter referred to as a drum brake) 10 according to an embodiment of the present invention, with a bottomed cylindrical brake drum (rotating drum) removed. . A one-dot chain line in FIG. 1 indicates an inner peripheral surface 12 a of the brake drum 12. FIG. 2 shows a II-II cross section of the drum brake 10 of FIG.

  The drum brake 10 has a substantially disk shape, and includes a backing plate 16 having a mounting hole 14 that is integrally fastened to a vehicle body side member such as an axle tube, an axle housing, a suspension device, or a non-rotating member (not shown). Is provided.

  As shown in FIG. 1, a wheel cylinder 22 that projects a pair of pistons 18 and 20 from both ends based on the supply of brake hydraulic pressure generated by operation of a brake pedal (not shown) to the outer periphery of the backing plate 16, An anchor 24 located at a point symmetric with respect to the wheel cylinder 22 is fixed by a bolt (not shown) or the like. The wheel cylinder 22 functions as an expansion device for expanding a later-described brake shoe and pressing the brake shoe against the inner peripheral surface of the rotating drum.

  A pair of brake shoes 26 and 28 are slidably disposed on the backing plate 16 between the wheel cylinder 22 on the backing plate 16 and the anchor 24 along the circumferential direction of the outer peripheral portion of the backing plate 16. . Engaging grooves 30 in the direction parallel to the backing plate 16 are formed in the pistons 18 and 20 of the wheel cylinder 22, respectively, and a pair of engaging protrusions 32 protruding in the circumferential direction are formed in the anchor 24. . Ends of the brake shoes 26 and 28 on the wheel cylinder 22 side are respectively fitted into engagement grooves 30 formed in the pistons 18 and 20 so that movement in a direction away from the backing plate 16 is restricted. The pistons 18 and 20 are brought into contact with each other. Further, the ends of the brake shoes 26 and 28 on the anchor 24 side are brought into contact with the anchor 24 in a state where movement in a direction away from the backing plate 16 is restricted by the engagement protrusion 32.

  A first return spring 34 is stretched between the ends of the brake shoes 26 and 28 on the wheel cylinder 22 side, and a strut 36 having a shoe gap automatic adjustment function is installed. At both ends of the strut 36, slit-shaped notches 36a and 36b having a predetermined width cut from the center of the edge in the longitudinal direction are formed, respectively, and the brake shoes 26 and 28 on the wheel cylinder 22 side are formed. A shoe web located at the end is fitted into them.

  A second return spring 38 is stretched between the ends of the brake shoes 26 and 28 on the anchor 24 side, and a parking brake expanding device 40 is disposed. The parking brake spreading device 40 includes a pair of side wall portions 42a facing each other in a plate shape perpendicular to the backing plate 16, and one end edge of the pair of side wall portions 42a on the side away from the backing plate 16. The main body 42 having a connecting portion 42b for connecting the portions to each other, and one end of the main body 42 by a support shaft 44 parallel to the backing plate 16 is disposed at one end of the main body 42. The lever member 46 is rotatably supported, and one end of the lever member 46 and the other end of the main body are inscribed between the ends of the pair of brake shoes 26 and 28 on the anchor 24 side. When a parking brake cable (not shown) connected to the other end of the lever member is pulled through the backing plate 16, the brake shoe 26 Between the ends of the anchor 24 side beauty 28 is adapted to be expanded. The ends of the pair of side wall portions 42a opposite to the connecting portion 42b are joined to each other, and a notch 42c is formed there, and the lever member 46 is also cut at a position below the support shaft 44. A notch 46a is formed, and shoe webs located at the ends of the brake shoes 26 and 28 on the parking brake expansion device 40 side are fitted therein.

  One brake shoe 26 of the pair of brake shoes 26 and 28 includes a first shoe portion 52 and a second shoe portion 54 that are connected to each other around an axis perpendicular to the backing plate 16 by a connecting pin 50. It is composed of Both the first shoe portion 52 and the second shoe portion 54 are backed from the central portion in the width direction of the inner peripheral surface of the shoe rims 52a and 54a and the belt-like shoe rims 52a and 54a bent in a partial arc shape. Shoe webs 52b and 54b projecting a predetermined length integrally with the flat plate portion 16a located on the inner peripheral side of the backing plate 16 on the inner peripheral side of the backing plate 16, and outer peripheries of the shoe rims 52a and 54a It is comprised from the friction materials 52c and 54c fixed to the surface. The end portions of the shoe web 52b of the first shoe portion 52 and the shoe web 54b of the second shoe portion 54b that are close to each other are connected to each other by the connecting pin 50 in a state of being in surface contact with each other. Further, as shown in FIG. 2, the portions of the shoe web 52b of the first shoe portion 52 and the shoe web 54b of the second shoe portion 54 that are overlapped with each other are locally localized by approximately half of the plate thickness in the thickness direction. The positions in the plate thickness direction of the mating surfaces S that are shifted and are in surface contact with each other are located within the thickness of the shoe webs 52b and 54b.

  Of the pair of first brake shoes 26 and 28, the other brake shoe 28 is connected to a first shoe portion 58 and a second shoe pivotably connected to each other around an axis perpendicular to the backing plate 16 by a connecting pin 56. The shoe portion 60 is configured. Both the first shoe portion 58 and the second shoe portion 60 are backed from a central portion in the width direction of the inner peripheral surface of the shoe rims 58a and 60a and strip-like shoe rims 58a and 60a bent in a partial arc shape. Shoe webs 58b and 60b projecting a predetermined length integrally with a flat plate portion 16a located on the inner peripheral side of the backing plate 16 on the inner peripheral side of the plate 16, and outer peripheries of shoe rims 58a and 60a It is comprised from the friction materials 58c and 60c fixed to the surface. The end portions of the shoe web 58b of the first shoe portion 58 and the shoe web 60b of the second shoe portion 60 that are close to each other are connected to each other by a connecting pin 56 in a state of being in surface contact with each other. Further, the portions of the shoe web 58b of the first shoe portion 58 and the shoe web 60b of the second shoe portion 60 that are overlapped with each other are locally half the plate thickness in the thickness direction, like the shoe webs 52b and 54b. The positions in the plate thickness direction of the mating surfaces that are displaced and are in surface contact with each other are located within the thickness of the shoe webs 58b and 60b.

  As a result, the first shoe portion 52 of one brake shoe 26 of the pair of brake shoes 26 and 28 and the first shoe portion 58 of the other brake shoe 28 have the same shape. The second shoe portion 54 of one of the brake shoes 26 and 28 and the second shoe portion 60 of the other brake shoe 28 have the same shape and are compatible with each other. It is possible.

  In the drum brake 10 configured as described above, for example, when the pistons 18 and 20 of the wheel cylinder 22 are protruded by a brake operation operation such as depression of a brake pedal, one end portions of the pair of brake shoes 26 and 28 are moved outward. Since it is expanded and slidably contacts the inner peripheral surface 12a of the brake drum 12, a braking force that suppresses the rotation of the brake drum 12 is generated. Further, when a parking brake cable (not shown) is pulled by manual operation, the other end portions of the pair of brake shoes 26 and 28 are expanded to the outer peripheral side by the parking brake expanding device 40, and the inner peripheral surface 12a of the brake drum 12 is expanded. Therefore, a braking force that suppresses the rotation of the brake drum 12 is generated. As shown in FIG. 1, the pair of brake shoes 26 and 28 are configured in the same manner and have the same operation. Therefore, the first shoe portion 52 and the second shoe 54 are connected to the connecting pin 50 in the braking operation. The brake shoe 26 that is configured to be connected to each other will be described as a representative.

  As shown in FIG. 1, when the brake drum 12 rotates in the clockwise direction A, when the pistons 18 and 20 of the wheel cylinder 22 are protruded by the brake operation operation, one end of the pair of brake shoes 26 and 28 is provided. The part is expanded to the outer peripheral side. When the friction material 52c of the first shoe portion 52 on the wheel cylinder 22 side of the brake shoe 26 on the leading side comes into contact with the inner peripheral surface 12a of the brake drum 12, the first shoe portion 52 rotates with the brake drum 12 and the brake The first shoe portion 52 is rotated by the accompanying force of the drum 12, and the friction material 52 c of the first shoe portion 52 is brought into close contact with the inner peripheral surface 12 a of the brake drum 12.

  Accordingly, the first shoe portion 52 is rotated together with the brake drum 12, and the accompanying force is transmitted to the second shoe portion 54 via the connecting pin 50. Therefore, the end portion of the friction material 54c of the second shoe portion 54 on the connection pin 50 side is brought into contact with the inner peripheral surface 12a of the brake drum 12. When one end of the friction material 54c is brought into contact with the inner peripheral surface 12a of the brake drum 12 in this way, the second shoe portion 54 is rotated together with the brake drum 12, and the brake drum 12 is set with the contact point with respect to the anchor 24 as a fulcrum. The outer peripheral surface of the friction material 54c of the second shoe portion 54 is almost completely brought into close contact with the inner peripheral surface 12a of the brake drum 12.

  Therefore, in the first shoe portion 52 and the second shoe portion 54 of the brake shoe 26, self-boosting force acts on substantially the entire outer peripheral surface of the friction materials 52c and 54c, and the friction of the first shoe portion 52 is increased. The surface pressure distribution in which the substantially entire surface of the material 52c presses the inner peripheral surface 12a of the brake drum 12 is substantially uniform, and the substantially entire surface of the friction material 54c of the second shoe portion 54 contacts the inner peripheral surface 12a of the brake drum 12. The surface pressure distribution to be pressed becomes substantially uniform, and the rotation of the brake drum 12 is braked.

  When the operation position of a brake pedal (not shown) is returned to the original position, the pistons 18 and 20 of the wheel cylinder 22 are pushed according to the urging force of the first return spring 34 and the first return spring 34 and the second return spring 38 are attached. The first shoe portion 52 and the second shoe portion 54 of the brake shoe 26 are returned to the original positions shown in FIG. 1 by the force, and the first shoe portion 58 and the second shoe portion 60 of the brake shoe 28 are also shown in FIG. Return to original position.

  According to the drum brake 10 of the present embodiment, the pair of brake shoes 26, 28 are positioned on the wheel cylinder 22 (expansion device) side of the backing plate 16, and the pair of first shoe portions 52 that form a partial arc shape, 58, a pair of second shoe portions 54, 60 located on the anchor 24 side of the backing plate 16 and forming a partial arc shape, a pair of first shoe portions 52, 58 and a pair of second shoe portions 54, 60 And a pair of connecting pins 50 and 56 that rotatably connect the end portions on the sides close to each other. Therefore, when the pair of first shoe portions 52 and 58 are moved to the outer peripheral side of the backing plate 16 by the wheel cylinder 22 and brought into contact with the inner peripheral surface 12a of the brake drum 12, for example, the brake shoe 26 The first shoe portion 54 is rotated around the connecting pin 50 by the accompanying force from the drum 12, and the space between one end portion and the other end portion of the first shoe portion 54 is entirely on the inner peripheral surface of the brake drum 12. At the same time, the second shoe portion 54 is rotated around the anchor 24 by the follower force transmitted from the first shoe portion 52 to be brought into close contact with the inner peripheral surface 12 a of the brake drum 12. It is done. Therefore, when the drum brake 10 is braked, the contact area where the first shoe portion 52 and the second shoe portion 54 are in contact with the inner peripheral surface 12a of the brake drum 12 is larger than that of a conventional integrated brake shoe. Further, the surface pressure distribution that presses the inner peripheral surface 12a of the brake drum 12 between the one end portion and the other end portion of the first shoe portion 52 and the second shoe portion 54 becomes uniform, and the braking force of the drum brake 10 Is improved as compared with the prior art. Further, when the drum brake 10 is braked, the first shoe portion 52 and the second shoe portion 54 are brought into contact with the inner peripheral surface 12a of the brake drum 12 so as to be in close contact with each other. Uneven wear of the friction materials 52c and 54c provided on the outer peripheral surface of the second shoe portion 54 is suppressed, and the durability of the drum brake 10 is preferably improved.

  Further, according to the drum brake 10 of the present embodiment, the first shoe portions 52 and 58 and the second shoe portions 54 and 60 are belt-like shoe rims 52a, 58a, 54a, 60a bent into a partial arc shape. , Plate-like shoe webs 52b, 58b integrally projecting a predetermined length from the center in the width direction of the inner peripheral surface of the shoe rims 52a, 58a, 54a, 60a toward the inner peripheral side of the backing plate 16; 54b, 60b, and the end portions of the shoe webs 52b, 58b of the first shoe portions 52, 58 and the shoe webs 54b, 60b of the second shoe portions 54, 60 close to each other in the thickness direction. In a state of surface contact with each other, the connection pins 50 and 56 are rotatably connected. For this reason, since the 1st shoe parts 52 and 58 and the 2nd shoe parts 54 and 60 are reliably connected so that relative rotation is possible by simple structure, the reliability of the drum brake 10 is improved.

  Further, according to the drum brake 10 of the present embodiment, the overlapping portions of the shoe webs 52b and 58b of the first shoe portions 52 and 58 and the shoe webs 54b and 60b of the second shoe portions 54 and 60 are overlapped with each other. The positions of the mating surfaces S that are locally shifted by half the plate thickness in the thickness direction and are in surface contact with each other are located within the thickness of the shoe webs 52b, 58b and 54b, 60b. Therefore, the entrainment force transmitted from the shoe webs 52b, 58b of the first shoe parts 52, 58 to the shoe webs 54b, 60b of the second shoe parts 54, 60 is projected to the central part in the width direction of the inner peripheral surface. Similarly, the shoe webs 52b and 58b of the first shoe parts 52 and 58 are transmitted to the shoe webs 54b and 60b of the second shoe parts 54 and 60 which are similarly projected from the center part in the width direction of the inner peripheral surface. Therefore, the uneven wear 52c, 58c and 54c, 60c of the friction material adhered to the outer peripheral surfaces of the first shoe parts 52, 58 and the second shoe parts 54, 60 is more preferably prevented.

  Further, according to the drum brake 10 of the present embodiment, the first shoe portion 52 of one brake shoe 26 and the first shoe portion 58 of the other brake shoe 28 are mutually connected. The second shoe portion 54 of one brake shoe 26 and the second shoe portion 60 of the other brake shoe 28 have the same shape as each other. It is what you have. Therefore, between the first shoe portion 52 of one brake shoe 26 and the first shoe portion 58 of the other brake shoe 28 of the pair of brake shoes 26, 28, the second shoe portion of one brake shoe 26. Between the second shoe portion 60 of the other brake shoe 28 and 54, the interchangeability of the components is mutually possible, so there is an advantage that the number of types of components is reduced.

  Further, according to the drum brake 10 of the present embodiment, the pair of return springs 34, 38 are arranged such that the end portion of the first shoe portion 52 of one brake shoe 26 on the wheel cylinder 22 side and the first brake shoe 28 first. The first return spring 34 stretched between the end portion of the shoe portion 58 on the wheel cylinder 22 side, the end portion of the second shoe portion 54 of one brake shoe 26 on the anchor 24 side, and the other brake shoe 28. And a second return spring 38 stretched between the second shoe portion 60 and the end of the second shoe portion 60 on the anchor 24 side. For this reason, regardless of the urging force of the first return spring 34 and the second return spring 38, the pair of first shoe portions 52, 58 abuts against the pistons 18, 20 of the wheel cylinder 22 and accurately positions during non-braking. Then, the pair of second shoe parts 54 and 60 abuts against the anchor 24 and is positioned accurately.

  Further, according to the drum brake 10 of the present embodiment, the strut 36 spanned between the first shoe portion 52 of one brake shoe 26 and the first shoe portion 58 of the other brake shoe 28, A parking brake spreading mechanism 40 is provided between the second shoe portion 54 of the brake shoe 26 and the second shoe portion 60 of the other brake shoe 28, and the first shoe of one brake shoe 26 is provided. The first shoe portion 58 of the portion 52 and the other brake shoe 28 are respectively fitted into notches 36a and 36b having a predetermined width cut in the longitudinal direction of the strut 34 from both end edges of the strut 34. The second shoe portion 54 of the brake shoe 26 and the second shoe portion 60 of the other brake shoe 28 are provided with a parking brake expanding mechanism 40. Notch 46a of a predetermined width provided at both ends, are respectively fitted into the inside 42c. For this reason, the first shoe portions 52 and 58 are fitted into the notches 36a and 36b having a predetermined width of the strut 34, so that the lifting from the backing plate 16 is restricted, and the second shoe portions 54 and 60 are used for parking brakes. By being fitted into the notches 46a and 42c having a predetermined width of the expansion mechanism 40, the lifting from the backing plate 16 is prevented, and the postures of the first shoe portions 52 and 58 and the second shoe portions 54 and 60 are maintained. Therefore, it becomes easy to remove the shoe hold down device conventionally used for maintaining the posture of the brake shoe, and may not be necessary for a small-diameter drum brake.

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

  FIG. 5 is a front view for explaining the configuration of a drum brake according to another embodiment of the present invention, and FIG. 6 is a sectional view taken along line VI-VI in FIG. The drum brake 10 shown in FIGS. 5 and 6 is different from the drum brake 10 shown in FIG. 1 in that end portions of the pair of first shoe portions 52 and 58 and the pair of second shoe portions 54 and 60 approach each other. These are not connected to each other by the connecting pins 50 and 56 so as to be rotatable relative to each other, and are kept in contact with each other by the biasing force of the pair of coil springs 70 and 72 stretched between them. However, they are different in that they are connected in a state in which relative rotation is allowed, but the others are configured similarly.

  As shown in FIGS. 5 and 6, the pair of coil springs 70 and 72 includes shoe webs 52 b and 58 b, between the pair of first shoe parts 52 and 58 and the pair of second shoe parts 54 and 60, The shoe webs 54b and 60b are stretched in an intermediate portion in the circumferential direction with their both ends hooked.

  A pair of second shoe portions 54, 60 side end portions of the pair of first shoe portions 52, 58 and a pair of second shoe portions 54, 60 pair of shoe webs 54b, 60b. First abutting surfaces 74 and 76 that are positioned on the inner peripheral side of the backing plate 16 and abut against each other and receive the urging force of the coil springs 70 and 72, The first shoe portions 52, 58 and the second shoe portion are located on the outer peripheral side of the plate 16 and come into contact with each other at the time of braking when the pair of brake shoes 26, 28 are expanded, against the urging force of the urging device. Second contact surfaces 78 and 80 functioning as rotation center points of relative rotation of 54 and 60 are provided.

The first contact surfaces 74 and 76 and the second contact surfaces 78 and 80 are formed along a substantially radial direction, and the first contact surfaces 74 and 76 are more than the second contact surfaces 78 and 80. It is located on the wheel cylinder 22 side and is formed at a position shifted in the circumferential direction.
As a result, the space between the pair of first shoe portions 52 and 58 and the space between the second shoe portions 54 and 60 have a symmetrical shape in FIG. They are compatible with each other.

  The braking action of the drum brake 10 of the present embodiment is connected so that the first shoe portion 52 and the second shoe portion 54 are brought into contact with each other by a spring 70 in the same manner as in the above-described embodiment. The brake shoe 26 will be described as a representative. For example, when the piston 18 and 20 of the wheel cylinder 22 is projected while the brake drum 12 is rotating in the clockwise direction A, one end portions of the pair of brake shoes 26 and 28 are expanded outward. . When the friction material 52c of the first shoe portion 52 on the wheel cylinder 22 side of the brake shoe 26 on the leading side comes into contact with the inner peripheral surface 12a of the brake drum 12, the first shoe portion 52 rotates with the brake drum 12 and the brake The first shoe portion 52 is rotated by the accompanying force of the drum 12, and the friction material 52 c of the first shoe portion 52 is brought into close contact with the inner peripheral surface 12 a of the brake drum 12. As a result, when the first shoe portion 52 is rotated together with the brake drum 12 and the rotation force is transmitted to the second shoe portion 54, the end portion of the friction material 54c of the second shoe portion 54 on the first shoe portion 52 side. Is brought into contact with the inner peripheral surface 12 a of the brake drum 12. When one end of the friction material 54c is brought into contact with the inner peripheral surface 12a of the brake drum 12 in this way, the second shoe portion 54 is rotated together with the brake drum 12, and the brake drum 12 is set with the contact point with respect to the anchor 24 as a fulcrum. The outer peripheral surface of the friction material 54c of the second shoe portion 54 is almost completely brought into close contact with the inner peripheral surface 12a of the brake drum 12. Therefore, in the first shoe portion 52 and the second shoe portion 54 of the brake shoe 26, self-boosting force acts on substantially the entire outer peripheral surface of the friction materials 52c and 54c, and the friction of the first shoe portion 52 is increased. The surface pressure distribution in which substantially the entire surface of the material 52c and the friction material 54c of the second shoe portion 54 presses the inner peripheral surface 12a of the brake drum 12 becomes substantially uniform, and the rotation of the brake drum 12 is braked.

  According to this embodiment, as in the previous embodiment, the contact area where the first shoe portion 52 and the second shoe portion 54 are in contact with the inner peripheral surface 12a of the brake drum 12 when the drum brake 10 is braked. Is larger than that of the conventional integrated brake shoe, and the pressure between the one end and the other end of the first shoe portion 52 and the second shoe portion 54 presses the inner peripheral surface 12a of the brake drum 12. The distribution becomes uniform, and the braking force of the drum brake 10 is improved compared to the conventional case. Further, when the drum brake 10 is braked, the first shoe portion 52 and the second shoe portion 54 are brought into contact with the inner peripheral surface 12a of the brake drum 12 so as to be in close contact with each other. Uneven wear of the friction materials 52c and 54c provided on the outer peripheral surface of the second shoe portion 54 is suppressed, and the durability of the drum brake 10 is preferably improved.

  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 wheel cylinder 22 that widens one end of the pair of brake shoes 26 and 28 is provided, but instead of this, a cam member driven by hydraulic pressure, an electric type Other type expansion devices such as a cam mechanism may be provided. In short, what is necessary is just to expand one end part of a pair of brake shoes 26 and 28. FIG.

  Further, the strut 36 of the above-described embodiment automatically adjusts the shoe gap, but may manually adjust the shoe gap.

  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 12a: Brake drum inner peripheral surface 16: Backing plate 18: Piston 20: Piston 22: Wheel cylinder (expansion device)
24: anchor 26, 28: brake shoe 30: engagement groove 32: engagement protrusion 34: first return spring 36: strut 36a: notch 36b: notch 38: second return spring 40: expansion device for parking brake 42c: Notch 46a: Notch 50: Connecting pin 52: First shoe portion 52a: Shoe rim 52b: Shoe web 54: Second shoe portion 54a: Shoe rim 54b: Shoe web 56: Connecting pin 58: First shoe portion 58a: Shoe rim 58b: Shoe web 60: Second shoe portion 60a: Shoe rim 60b: Shoe web 70, 72: Coil spring (biasing device)
74, 76: 1st contact part 78, 80: 2nd contact part

Claims (10)

A pair of arcuate brake shoes disposed on the backing plate so as to be expandable, and a pair of brake shoes disposed between one end of the pair of brake shoes, and by separating one end of the pair of brake shoes from each other An expansion device that expands to the outer peripheral side of the backing plate, an anchor with which one other end of the pair of brake shoes is brought into contact, and between one end and the other end of the pair of brake shoes A drum brake having a pair of return springs each stretched;
The pair of brake shoes are positioned on the expansion device side of the backing plate, and are positioned on the anchor side of the backing plate and a pair of first shoe portions forming a partial arc shape, and form a partial arc shape. A pair of second shoe portions, and a pair of connecting pins that rotatably connect the end portions of the pair of first shoe portions and the pair of second shoe portions that are close to each other, are provided. Drum brake. The first shoe portion and the second shoe portion are a strip-shaped shoe rim bent in a partial arc shape, and a predetermined distance from the center portion in the width direction of the inner peripheral surface of the shoe rim toward the inner peripheral side of the backing plate. A plate-like shoe web that protrudes integrally with the length,
End portions of the shoe web of the first shoe and the shoe web of the second shoe that are close to each other are pivotally coupled by the coupling pin in a surface contact state that is overlapped with each other in the thickness direction. The drum brake of claim 1 characterized in that   The portions of the shoe web of the first shoe portion and the shoe web of the second shoe portion that are overlapped with each other are locally shifted by half of the plate thickness in the thickness direction, and of the mating surfaces that are in surface contact with each other. The drum brake according to claim 2, wherein the position is located within the thickness of the shoe web.   The first shoe portion of one of the pair of brake shoes and the first shoe portion of the other brake shoe have the same shape, and one of the pair of brake shoes 4. The drum brake according to claim 3, wherein the second shoe portion of the brake shoe and the second shoe portion of the other brake shoe have the same shape.   The pair of return springs are stretched between an end of the first shoe portion of the one brake shoe on the side of the expansion device and an end of the first shoe portion of the other brake shoe on the side of the expansion device. A first return spring provided, and an anchor side end of the second shoe portion of the one brake shoe and an anchor side end of the second shoe portion of the other brake shoe. The drum brake according to any one of claims 1 to 4, further comprising a second return spring. A pair of arcuate brake shoes disposed on the backing plate so as to be expandable, and a pair of brake shoes disposed between one end of the pair of brake shoes, and by separating one end of the pair of brake shoes from each other An expansion device that expands to the outer peripheral side of the backing plate, an anchor with which one other end of the pair of brake shoes is brought into contact, and between one end and the other end of the pair of brake shoes A drum brake having a pair of return springs each stretched;
The pair of brake shoes are positioned on the expansion device side of the backing plate, and are positioned on the anchor side of the backing plate and a pair of first shoe portions forming a partial arc shape, and form a partial arc shape. The pair of second shoe parts and the pair of first shoe parts and the pair of second shoe parts are urged so as to approach each other so as to approach each other. A drum brake comprising a pair of urging devices that allow relative rotation while maintaining a contact state.   The drum brake according to claim 6, wherein the pair of urging devices are a pair of coil springs respectively stretched between the pair of first shoes and the pair of second shoes.   End portions of the first shoe portion and the second shoe portion, which are close to each other, are located on the inner peripheral side of the backing plate and are in contact with each other and receive a biasing force of the biasing device. And the first shoe portion and the second shoe portion that are located on the outer peripheral side of the backing plate and contact each other at the time of braking when the pair of brake shoes are expanded to resist the biasing force of the biasing device. 8. The drum brake according to claim 6, further comprising a second contact surface that functions as a rotation center point of relative rotation.   The first shoe portion of one of the pair of brake shoes and the first shoe portion of the other brake shoe have the same shape, and one of the pair of brake shoes The drum brake according to claim 8, wherein the second shoe portion of the brake shoe and the second shoe portion of the other brake shoe have the same shape.   The pair of return springs are stretched between an end of the first shoe portion of the one brake shoe on the side of the expansion device and an end of the first shoe portion of the other brake shoe on the side of the expansion device. A first return spring provided, and an anchor side end of the second shoe portion of the one brake shoe and an anchor side end of the second shoe portion of the other brake shoe. The drum brake according to any one of claims 6 to 9, further comprising a second return spring.

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