JP2010242849A - Double-drum type drum brake - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To restrain partial abrasion of an outer peripheral side pad in a double-drum type drum brake. <P>SOLUTION: A frictional force generating device 10 is arranged between both cylindrical parts 14 and 16 of a double drum 12 having the outer peripheral side cylindrical part 14 and the inner peripheral side cylindrical part 16. The frictional force generating device 10 has the outer peripheral side pad 52 to an inner peripheral frictional surface 50 of the outer peripheral side cylindrical part 14, an inner peripheral side pad 56 to an outer peripheral frictional surface 54 of the inner peripheral side cylindrical part 16, and a cylinder assembly 24 for driving both these pads. The cylinder assembly 24 has first and second outer peripheral side cylinders 30 and 32 and an inner peripheral side cylinder 34. The first and second outer peripheral side cylinders 30 and 32 are not symmetrically arranged to the center in the peripheral direction of the outer peripheral side pad 52, and are deviatively arranged to the downstream side in the rotational direction of the double drum 12. At the same time or instead of it, a diameter of a piston 42 of the first outer peripheral side cylinder 30 on the downstream side, may be formed larger than that of the second outer peripheral side cylinder 32. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a double drum type drum brake, and more particularly to an improvement in the behavior of a friction pad.

  The double drum type drum brake includes (a) an outer peripheral side cylindrical portion having an inner peripheral friction surface, and an inner peripheral side cylindrical portion disposed on the inner peripheral side of the outer peripheral side cylindrical portion and having an outer peripheral friction surface. (B) is arranged opposite to the inner peripheral friction surface of the outer cylindrical portion, and is non-rotatable so that it can move in the radial direction of the double cylindrical drum and cannot move in the circumferential direction. (C) an outer peripheral side cylinder that presses the outer peripheral side pad against the inner peripheral friction surface, and (d) an outer peripheral pad that faces the outer peripheral friction surface of the inner peripheral side cylindrical portion. The member includes an inner peripheral pad that is held movable in the radial direction and immovable in the circumferential direction, and (e) an inner peripheral cylinder that presses the inner peripheral pad against the outer friction surface. Configured.

  One such double drum drum brake is described in US Pat. In this double drum type drum brake, the trailing force of the outer peripheral side pad and the inner peripheral side pad with respect to the double drum is applied to the trailing end which is the downstream end of both pads in the rotational direction of the double drum. The braking ability is increased by converting the pressing force to the inner peripheral friction surface and the outer peripheral friction surface in the vicinity.

  Further, in Patent Document 2, a plurality of wheel cylinders for pressing one brake pad against the inner peripheral friction surface of the single drum are provided, and the brake fluid pressure is individually controlled to control the brake pads. And the control of the surface pressure distribution between the inner circumferential friction surface and the occurrence of squealing.

  Furthermore, in Patent Document 3, two friction pads are provided on the inner peripheral side and the outer peripheral side of a single drum having an inner peripheral friction surface and an outer peripheral friction surface so as to face each other, and the two friction pads are straddled. A drum brake with a floating caliper is described. It is also described that the floating caliper is provided with two wheel cylinders arranged in the circumferential direction of the single drum.

Japanese Patent Publication No.49-12747 JP 2006-22860 A JP 51-144874 A

  In view of the above circumstances, the present invention has been made to further improve the double drum type drum brake.

In the double drum drum brake, the present invention provides an outer peripheral side cylinder that presses an outer peripheral side pad disposed to face the inner peripheral friction surface of the outer peripheral side cylindrical portion against the inner peripheral friction surface. One is characterized in that two are provided side by side in the circumferential direction of the double drum.
The distance between the center line of the upstream cylinder which is the upstream side in the rotational direction of the double drum and the center line passing through the center in the circumferential direction of the outer side pad is the downstream side. It is desirable that the distance between the center line of the cylinder and the distance between the center line is smaller than the distance between the cylinder line and the upstream cylinder operating force is smaller than the downstream cylinder operating force. .
According to the present invention, there is further provided an action member which is stretched between the outer peripheral side pad and the inner peripheral side pad and which acts on an intermediate portion of the tension spring that urges both the pads toward each other, thereby bending the tension spring. By doing so, a double drum type drum brake is obtained in which the outer peripheral side pad and the inner peripheral side pad are positively pressed against the non-rotating member holding them.

In the double drum type drum brake, it is desirable that the outer peripheral side pad pressed against the inner peripheral friction surface of the outer peripheral cylindrical portion having a long peripheral length is longer than the inner peripheral pad. However, in that case, when the outer peripheral pad is pressed against the inner peripheral friction surface by one wheel cylinder, the outer peripheral pad is bent due to elastic deformation, and the surface pressure of the intermediate portion in the circumferential direction is higher than the surface pressure of other portions. Thus, uneven wear occurs. On the other hand, if two wheel cylinders are arranged in the circumferential direction, the occurrence of the knitting wear can be suppressed.
Further, in the outer peripheral side pad, the acting point of the resultant force of the frictional force generated with the inner peripheral friction surface deviates to the outer peripheral side with respect to the receiving surface of the non-rotating member that receives the accompanying force of the outer peripheral side pad. Since this is unavoidable, a rotational moment is generated on the outer peripheral pad, and uneven wear occurs in which the wear on the leading end side is greater than the wear on the trailing end side. On the other hand, if the two wheel cylinders satisfy at least one of the conditions (a) and (b), the occurrence of uneven wear due to the rotational moment can be suppressed.
Furthermore, if the acting member is applied to the intermediate part of the tension spring stretched between the outer pad and the inner pad to curve the tension spring, the outer pad and the inner pad are not rotated. A force that positively presses the member can be applied, and the generation of abnormal noise during traveling on rough roads (rough roads) can be suppressed.

It is a partial cross section front view which shows the principal part of the double drum type drum brake which is one Embodiment of this invention. It is a partial cross section front view which shows the principal part of the double drum type drum brake which is another embodiment of this invention. It is a front view which shows the principal part of the double drum type drum brake which is another embodiment of this invention. It is AA sectional drawing in FIG. It is a figure equivalent to FIG. 4 in the double drum type drum brake which is another embodiment of this invention.

  FIG. 1 shows one frictional force generator 10 in a double drum type drum brake according to an embodiment of the present invention. The frictional force generator 10 is provided between the outer peripheral cylindrical portion 14 and the inner peripheral cylindrical portion 16 of the double drum 12. The double drum 12 includes a disk portion (not shown) that connects the outer circumferential side cylindrical portion 14 and the inner circumferential side cylindrical portion 16, and is fixed to the wheel of the vehicle in the disk portion and rotates integrally with the wheel. The double drum rotates in the direction indicated by the arrow X when the vehicle moves forward. A backing plate 20 is provided in a state where the opening of the double drum opposite to the disk portion is closed, and the frictional force generator 10 is attached to the backing plate 20. Note that a plurality of frictional force generators 10 are spaced apart from each other in the circumferential direction of the double drum 12 and are arranged symmetrically with respect to the rotational axis of the double drum 12 as an axis of symmetry. FIG. Only a representative is shown.

  A bracket 22 as a non-rotating member is fixed to the backing plate 20, and a cylinder assembly 24 including three wheel cylinders is fixed to the bracket 22. The three wheel cylinders are a first outer peripheral cylinder 30, a second outer peripheral cylinder 32, and an inner peripheral cylinder 34, and the first outer peripheral cylinder 30 is located downstream in the rotational direction of the double drum 12. It is a downstream cylinder, and the second outer cylinder 32 is an upstream cylinder. Each of the wheel cylinders 30, 32, and 34 includes a cylinder housing 40 and a piston 42 that is liquid-tightly and slidably fitted therein. The outer diameters of the pistons 42 of the first outer peripheral side cylinder 30 and the second outer peripheral side cylinder 32 are the same, and the piston 42 of the inner peripheral side cylinder 34 has a larger outer diameter than both the pistons 42. The three wheel cylinders 30, 32, and 34 are supplied with the same hydraulic pressure.

  The outer peripheral side cylindrical portion 14 has an inner peripheral friction surface 50, and an outer peripheral side pad 52, which is a friction pad, is provided facing the inner peripheral friction surface 50. The inner peripheral cylindrical portion 16 has an outer peripheral friction surface 54, and an outer peripheral pad 56 is provided opposite to the outer peripheral friction surface. Both friction pads 52 and 56 are held by the bracket 22 so as to be movable in the radial direction of the double drum 12 but immovable in the circumferential direction of the double drum 12. A gap is formed between the outer side surfaces of the friction pads 52 and 56 and the inner side surface of the bracket 22 to allow the friction pads 52 and 56 to slide. Therefore, even if both the friction pads 52 and 56 say “impossible to move in the circumferential direction of the double drum 12”, the friction pads 52 and 56 are not impossible to move at all. A pair of tension coil springs 58 is stretched between the friction pads 52 and 56 so that the friction pads 52 and 56 approach each other, i.e., the outer peripheral pad 52 extends from the inner peripheral friction surface 50 to the inner peripheral side. The pads 56 are biased in directions away from the outer peripheral friction surface 54.

  The outer circumferential side pad 52 has a longitudinal shape in which the dimension (length) in the direction parallel to the circumferential direction of the double drum 12 is larger than the dimension in the direction parallel to the rotational axis of the double drum 12. Two places separated in the longitudinal direction are pressed against the inner peripheral friction surface 50 of the outer cylindrical part 14 by the two pistons 42 of the first and second outer cylinders 30. Therefore, as in the case where the central portion in the longitudinal direction is pressed against the inner peripheral friction surface 50 by one piston 42, the surface pressure is higher in the central portion than in the other portions due to the elastic deformation of the outer peripheral side pad 52. Occurrence of uneven wear in which the amount of wear becomes particularly large is suppressed.

  Further, the outer peripheral side pad 52 is pressed against the inner peripheral friction surface 50, and a braking force is applied to the double drum 12 by the frictional force generated between the inner peripheral friction surface 50. Trying to be taken to the double drum 12. This revolving force is received by the receiving surface 60 of the bracket 22. Assuming that the pressing force of the outer peripheral pad 52 by the first and second outer peripheral cylinders 30 and 32 is symmetric with respect to the center of the outer peripheral pad 52, the outer peripheral pad 52 and the inner peripheral friction surface 50 are The point of action of the resultant force F1 of the frictional force generated between them can be considered to be located substantially at the center on the frictional surface of the outer circumferential pad 52. The line of action of the reaction force R1 applied to the side pad 52 is separated by a distance L1. Therefore, a rotational moment is generated in the outer peripheral side pad 52, and unevenness of the surface pressure between the outer peripheral side pad 52 and the inner peripheral friction surface 50 is generated. Since the surface pressure on the leading end side of the outer peripheral side pad 52 becomes higher than the surface pressure on the trailing end side, uneven wear that increases the amount of wear on the leading end side occurs.

  Therefore, in the present embodiment, as shown in FIG. 1, the first and second outer cylinders 30 and 32 are arranged asymmetrically with respect to the center of the outer pad 52. The axis of the piston 42 of the first outer cylinder 30 is closer to the center of the outer pad than the axis of the piston 42 of the second cylinder 32. Therefore, considering the state where there is no rotational moment due to the following force, the surface pressure of the outer peripheral side pad 52 is larger on the trailing end side than on the leading end side. This non-uniform surface pressure distribution shows a tendency opposite to the non-uniform surface pressure distribution described above due to the rotational moment, and the non-uniform surface pressure distribution due to the rotational moment is canceled out to make the surface pressure distribution uniform. Or non-uniformity is reduced.

  As for the inner circumferential side pad 56, the action line of the resultant force F2 of the frictional force and the action line of the reaction force R2 from the receiving surface 62 are substantially coincident as shown in FIG. A rotational moment does not occur in the pad 56, and unevenness of the surface pressure does not occur. Therefore, the axis of the piston 42 of the inner peripheral side cylinder 34 passes through the center of the inner peripheral side pad 56.

  In addition, the outer peripheral side pad 52 has the friction material 65 fixed to the outer peripheral surface of a metal member having a T-shaped cross section with the web 64 fixed to the inner peripheral surface of the partially cylindrical rim 63 at a right angle. The web 64 is engaged with the piston 42 by being fitted into an engagement groove 66 formed in the piston 42. By this engagement, movement of the outer peripheral side pad 52 in the axial direction of the double drum 12 is prevented. An engagement groove may be formed in the receiving surface 60, and the web 64 may be fitted into the engagement groove to prevent the outer peripheral side pad 52 from moving in the axial direction of the double drum 12. In that case, the bottom surface of the engaging groove functions as a receiving surface. Similarly, the inner circumferential side pad 56 includes a rim 67, a web 68 and a friction material 69, and is engaged with the piston 42 in the web 68.

  FIG. 2 shows a frictional force generator 70 for a double drum drum brake which is another embodiment of the present invention. The present embodiment is different from the above-described embodiment in the cylinder assembly 72, and the other parts are the same. Therefore, the same reference numerals are given to the parts corresponding to each other, and the description is omitted.

  In the cylinder assembly 72, the diameter of the piston 76 of the first outer cylinder 74 that is the downstream cylinder is larger than the diameter of the piston 76 of the second outer cylinder 78. In the illustrated embodiment, the diameter of the piston 76 of the first outer peripheral cylinder 74 is an intermediate size between the diameter of the piston 76 of the second outer peripheral cylinder 78 and the diameter of the piston 76 of the inner peripheral cylinder 80. Yes. These three wheel cylinders 74, 78, 80 are supplied with the same hydraulic pressure.

Therefore, considering the state in which the aforementioned rotational moment does not occur in the outer peripheral side pad 52, the surface pressure between the outer peripheral side pad 52 and the inner peripheral friction surface 50 is larger on the trailing end side than on the leading end side. This non-uniform surface pressure distribution shows a tendency opposite to the non-uniform surface pressure distribution caused by the rotational moment, and the non-uniform surface pressure distribution caused by the rotational moment is canceled out to make the surface pressure distribution uniform. Or non-uniformity is reduced.
In this embodiment, the positions of the axes of the first and second outer cylinders 74 and 78 are symmetric with respect to the center of the outer pad 52. Similarly, non-targeting is possible, in which case it becomes easier to counteract the unevenness of the surface pressure distribution caused by the rotational moment.

  Another embodiment of the present invention is shown in FIGS. In the frictional force generator 88 according to the present embodiment, the cylinder assembly 90 includes one outer cylinder 92 and one inner cylinder 94. Moreover, both the wheel cylinders 92 and 94 have a structure in which two pistons 98 are fitted in opposite directions to a common cylinder housing 96 opened at both ends.

  The outer peripheral side cylinder 92 and the inner peripheral side cylinder 94 are respectively connected to the outer peripheral side pad 100 and the inner peripheral side pad 102 with the inner peripheral friction surface 50 of the outer peripheral side cylindrical portion 14 and the outer peripheral friction surface 54 of the inner peripheral side cylindrical portion 16. Press on. A pair of tension coil springs 58 are stretched between the two friction pads 52 and 54 to urge both friction pads 52 and 54 in a direction approaching each other. The action members 104 and 106 are applied to the intermediate portions of the pair of tension coil springs 58, respectively, and the tension coil springs 58 are curved.

  As shown in FIG. 4, the action member 104 acting on the downstream tension coil spring 58 in the rotation direction of the double drum 12 is intermediate between the tension coil springs 58 by the action surface 110 orthogonal to the rotation axis of the double drum 12. Acting on the portion, the tension coil spring 58 is bent in a direction parallel to the rotational axis of the double drum 12 in a direction approaching the backing plate 20. Therefore, the end portion of the tension coil spring 58 connected to the outer peripheral side pad 100 and the inner peripheral side pad 102 applies a force in the direction in which both the friction pads 100 and 102 are brought close to each other, and both are applied to the backing plate 20. Apply the force of the direction to approach. As a result, for example, the outer peripheral pad 100 typically shown in FIG. 4 is pressed against the support surface 114 of the bracket 112.

  On the other hand, the action member 106 acting on the upstream tension coil spring 58 in the rotation direction of the double drum 12 is inclined from the state orthogonal to the rotation axis of the double drum 12, as shown in FIG. 116 acts on an intermediate portion of the tension coil spring 58. For this reason, the intermediate portion of the tension coil spring 58 approaches the backing plate 20 and is curved toward the downstream side in the rotational direction of the double drum 12, so that the outer peripheral pad 100 and the inner peripheral pad 102 are curved. Apply force in the same direction. As a result, for example, the outer peripheral pad 100 is pressed against the support surface 114 and also against the receiving surface 118.

  Thus, the outer peripheral side pad 100 and the inner peripheral side pad 102 are urged toward the backing plate 20 side and the downstream side in the rotational direction of the double drum 12 and are pressed against the support surface 114 and the receiving surface 118, respectively. As a result, the friction pads 100 and 102 are stably held by the bracket 112, and the friction pads 100 and 102 may repeatedly move away from or contact the bracket 112 even when the vehicle travels on a rough road. It is suppressed and the generation of abnormal noise is suppressed.

  Another embodiment of the present invention is shown in FIG. In this embodiment, the action member acting on the upstream tension coil spring 58 in the rotation direction of the double drum 12 is an action member having the same configuration as the action member 104 in the above embodiment. Also with this configuration, the outer peripheral side pad 100 and the inner peripheral side pad 102 (only the outer peripheral side pad 100 is shown in FIG. 5) are pressed against the support surface 114, so that the support surface 11 and the two friction pads 100 when traveling on a rough road. , 102 is prevented from generating abnormal noise due to repeated collisions, and the frictional force between the support surface 114 and the friction pads 100, 102 causes the friction pads 100, 102 to move in a direction parallel to the backing plate 20. Accordingly, the generation of noise due to repeated collision between the receiving surface 118 and the friction pads 100 and 102 is also suppressed.

  In the embodiment shown in FIGS. 3 and 4 and the embodiment shown in FIG. 5, the cylinder assembly 90 is different from the cylinder assemblies 24 and 72 in the embodiment shown in FIGS. However, it is possible to have the same configuration as any of the cylinder assemblies 24 and 72, or to have the characteristics of both the cylinder assemblies 24 and 72.

  Although several embodiments of the present invention have been described in detail above, these are merely examples, and the present invention can be implemented in various modifications based on the knowledge of those skilled in the art.

  10: Friction force generator 12: Double drum 14: Outer cylindrical part 16: Inner cylindrical part 20: Backing plate 22: Bracket 24: Cylinder assembly 30: First outer cylinder 32: Second outer cylinder 34: Inner peripheral side cylinder 40: Cylinder housing 42: Piston 50: Inner peripheral friction surface 52: Outer peripheral side pad 54: Outer peripheral friction surface 56: Inner peripheral side pad 58: Tensile coil spring 60: Receiving surface 62: Receiving surface 70: Friction force generator 72: Cylinder assembly 74: First outer cylinder 76: Piston 78: Second outer cylinder 80: Inner cylinder 90: Cylinder assembly 92: Outer cylinder 94: Inner cylinder 96: Cylinder housing 98: Piston 100: Outer circumference Pad 102: inner circumferential side pad 104, 106: working members 110, 114: working surface 112: Bracket 114: bearing surface 118: reception surface

Claims (3)

A double drum provided with an outer peripheral side cylindrical portion having an inner peripheral friction surface, and an inner peripheral side cylindrical portion disposed on the inner peripheral side of the outer peripheral side cylindrical portion and having an outer peripheral friction surface;
An outer peripheral pad disposed opposite to the inner peripheral friction surface of the outer cylindrical portion and held on a non-rotating member so as to be movable in the radial direction of the double cylindrical drum and immovable in the circumferential direction. When,
An outer peripheral cylinder that presses the outer peripheral pad against the inner peripheral friction surface;
An inner circumferential pad disposed opposite to the outer circumferential friction surface of the inner circumferential cylindrical portion and held on the non-rotating member so as to be movable in the radial direction and immovable in the circumferential direction;
In the double drum type drum brake including the inner peripheral side cylinder that presses the inner peripheral side pad against the outer peripheral friction surface,
A double drum drum brake, wherein two outer cylinders are provided side by side in the circumferential direction with respect to one outer pad.   (a) Of the two outer cylinders, the distance between the center line of the upstream cylinder, which is upstream of the rotation direction of the double drum, and the center line passing through the center of the outer pad in the circumferential direction Is smaller than the distance between the center line of the downstream cylinder that is the downstream side in the rotational direction of the double drum and the center line, and (b) the operating force of the upstream cylinder is that of the downstream cylinder. The double-drum type drum brake according to claim 1, wherein at least one condition of being smaller than the operating force is satisfied. A double drum provided with an outer peripheral side cylindrical portion having an inner peripheral friction surface, and an inner peripheral side cylindrical portion disposed on the inner peripheral side of the outer peripheral side cylindrical portion and having an outer peripheral friction surface;
An outer peripheral pad disposed opposite to the inner peripheral friction surface of the outer cylindrical portion and held on a non-rotating member so as to be movable in the radial direction of the double cylindrical drum and immovable in the circumferential direction. When,
An outer peripheral cylinder that presses the outer peripheral pad against the inner peripheral friction surface;
An inner circumferential pad disposed opposite to the outer circumferential friction surface of the inner circumferential cylindrical portion and held on the non-rotating member so as to be movable in the radial direction and immovable in the circumferential direction;
An inner peripheral cylinder that presses the inner peripheral pad against the outer peripheral friction surface;
In a double drum type drum brake including a tension spring that is stretched between the outer peripheral side pad and the inner peripheral side pad and biases both pads in a direction approaching each other.
An action member that positively presses the outer peripheral side pad and the inner peripheral side pad against the non-rotating member by acting on an intermediate portion of the tension spring to bend the tension spring is provided. Heavy drum drum brake.

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