JP2007187209A - Disk brake corresponding to pad abrasion - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a disk brake for holding a disk between pads by driving a pad with a piston, wherein the spacing distance between pads with respect to the disk during non-braking prevents pads from being increased with the advancement of abrasion associated with the use from the new state of the pad when a return amount of a piston in releasing of braking is constant. <P>SOLUTION: In a disk brake which forces a piston to be pulled back in releasing of braking by restoring force of elastic deformation developed during breaking in an elastic ring 30 frictionally engaged with an outer peripheral surface of a piston 16, the friction engagement force exhibited by the outer peripheral surface of the piston with respect to the elastic ring is reduced with the advancement of the abrasion of a pad 24. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a disc brake used in a vehicle such as an automobile, and more particularly to a disc brake that automatically maintains the distance of the pad from the disc in response to wear of the pad.

  A disc brake used in vehicles such as automobiles has a structure in which a disc is pressed by a caliper and a piston through a pad to brake its rotation, and the piston is driven to a braking position for pressing the disc during braking. There is known a disc brake in which the piston is pulled back from the braking position when the brake is released by an elastic restoring force of elastic deformation generated in an elastic ring frictionally engaged with the outer peripheral surface of the piston.

In this type of disc brake, in order to mitigate the difference in the distance to which the piston is pulled back when the brake is released due to the magnitude of the braking driving force acting on the piston, the counter-pressure side end surface of the elastic ring faces the opposite side. Patent Document 1 below describes that an elastic ring having an elastic coefficient higher than that of the elastic ring is interposed between the ring groove side walls. Further, in Patent Document 2 below, there is a knockback that may occur in this type of disc brake, that is, the piston is pushed back by the disc rotor swing or deformation, and the brake pedal stroke during braking increases. In order to suppress this, it is described that a groove having a sawtooth cross section is provided on the outer peripheral surface that is in sliding contact with the oil seal of the piston.
JP-A-5-133429 JP-A-11-117966

  Disc brake pads are relatively soft at first, but gradually become harder as they are used, reducing the elasticity of the pad against compression and reducing the amount of pad thickness reduction for the same compression load. come. This is due to both the material of the pad becoming harder by repeated compression and the reduction of the pad thickness due to wear. Therefore, if the return amount of the piston at the time of brake release is constant, the pad will be sufficiently separated from the disk during non-braking when the pad is new and its elasticity is high and the elastic recovery amount is large. If the pad is used, the amount of wear increases, the degree of elasticity decreases, and the amount of elastic restoration decreases, the pad separation distance from the disk increases, and the brake pedal depression stroke increases. There's a problem.

  The present invention pays attention to the above situation, and an object of the present invention is to improve the disc brake so that the change in the separation distance of the pad from the disc can be suppressed by the change in the elasticity accompanying the wear of the pad.

  In order to solve the above-described problems, the present invention has a structure in which a disk is pressed by a caliper and a piston through a pad to brake its rotation, and the piston is driven to a braking position at which the disk is pressed and held during braking. A disc brake in which the piston is pulled back from the braking position when the brake is released by an elastic restoring force of elastic deformation generated in an elastic ring frictionally engaging the outer peripheral surface of the piston. The present invention proposes a disc brake characterized in that the frictional engagement force that the outer peripheral surface exhibits with respect to the elastic ring decreases with the progress of wear of the pad.

  The frictional engagement force that the outer peripheral surface of the piston exhibits to the elastic ring decreases with the progress of wear of the pad, and the surface roughness that the outer peripheral surface of the piston exhibits to the elastic ring changes from coarse to fine. May be due to.

  Alternatively, the decrease in the frictional engagement force that the outer peripheral surface of the piston exhibits on the elastic ring with the progress of wear of the pad reduces the peripheral length that the outer peripheral surface of the piston exhibits on the elastic ring. May be due.

  As described above, the structure has a structure in which the disk is pressed by the caliper and the piston through the pad to brake its rotation, and when the piston is driven to the braking position for pressing the disk during braking, the outer surface of the piston is In the disc brake in which the piston is pulled back from the braking position when the brake is released by the elastic restoring force of the elastic deformation generated in the elastic ring that is frictionally engaged, the elastic recovery of the elastic ring when the brake is released The pullback amount of the piston from the braking position due to the force is affected by the frictional engagement force between the outer peripheral surface of the piston and the elastic ring, and the pullback amount of the piston is larger than that when the frictional engagement force is stronger. It is thought to grow. Therefore, if the frictional engagement force exhibited by the outer peripheral surface of the piston against the elastic ring decreases with the progress of wear of the pad, the elasticity of the pad decreases with the progress of wear of the pad. The increase in the separation distance of the pad from the disk is offset by reducing the piston retraction amount by reducing the frictional engagement force that the outer peripheral surface of the piston exhibits against the elastic ring as the pad wear progresses, It is possible to suppress a change in the separation distance of the pad from the disk over the entire use period of the pad until the life of the pad is exhausted due to the progress of wear.

  The frictional engagement force between two objects that are in contact with each other varies depending on the roughness of the surface that at least one of the two objects exhibits against the other, so that the pad wear of the frictional radial force that the outer peripheral surface of the piston exhibits against the elastic ring If the surface roughness of the piston outer peripheral surface changes with respect to the elastic ring is changed from coarse to thin, the roughness of the piston outer peripheral surface becomes the axis of the piston. The above problems can be achieved by a simple method of finishing to change along the direction.

  Alternatively, since the frictional engagement force between two objects that are in contact with each other varies depending on the force with which the two objects are pressed against each other, the pad of the frictional engagement force that the outer peripheral surface of the piston exhibits against the elastic ring If the decrease in the wear of the piston is due to a decrease in the circumferential length of the outer peripheral surface of the piston with respect to the elastic ring, the elastic ring is slightly extended to be engaged with the outer peripheral surface of the piston. The above-described problems can be achieved by a simple method of finishing the piston so that the circumference of the piston changes along the axial direction of the piston.

  FIG. 1 is a schematic longitudinal sectional view showing a disc brake according to an embodiment of the present invention. In the figure, reference numeral 10 denotes a caliper, which is illustrated as being divided into several parts for the convenience of manufacture and assembly, but is a C-shaped member as a whole, with a cylinder at one end thereof. A chamber 12 is provided, and a pad support 14 is provided at the other end. A piston 16 is mounted in the cylinder chamber 12, and the piston 16 is attached to the caliper 10 by supplying hydraulic pressure to the chamber space on the left side of the cylinder chamber 12 via a hydraulic conduit not shown in the drawing. On the other hand, it is driven to the right in the figure. A pad 20 is attached to the right end of the piston 16 via a pad support plate 18. A pad 24 is also mounted on the caliper pad support 14 via a pad support plate 22, and a brake disk 26 is disposed between the pads 20 and 24, and is integrated with a wheel not shown in the drawing. It rotates around a rotation center axis not shown in the figure. The caliper 10 is supported so as to be movable along the axis of the piston 16 by a caliper support (not shown) so that its operating center is aligned with the center of the disk in accordance with the wear of the pad.

  Thus, when the piston 16 is driven rightward in the drawing with respect to the caliper 10 by supplying hydraulic pressure to the cylinder chamber 12, the piston 16 supports the pad 20 supported by the pad support portion 14 of the caliper. The disc 26 is pressed between the pads 20 and 24, and the rotation is braked.

  A ring groove 28 is formed in a part of the peripheral wall surface of the cylinder chamber 12, and an elastic ring 30 made of rubber or the like is mounted therein. Although not clearly shown in the drawing, when the piston 16 is driven rightward in the drawing, an elastic body that is dragged rightward in the drawing by frictional engagement with the outer peripheral surface of the piston. A space in which a part of the ring 30 is elastically deformed and fitted is formed, and the elastic restoring force of elastic deformation of the elastic body ring due to the fitting of a part of the elastic body ring in the space is applied to the piston. When the hydraulic drive force is released, the piston is pulled back in the direction away from the disk 26 toward the left in the figure. Reference numeral 32 denotes a telescopic dust boot that prevents foreign matter from entering the cylinder chamber through the gap between the piston and the cylinder.

  The basic structure of the disc brake as described above is a known structure. The present invention is in a special configuration relating to the finish of the outer peripheral surface of the piston 16 that engages with the elastic ring 30.

  FIG. 2 shows that the surface roughness of the outer peripheral surface of the piston 16 changes from coarse to fine from the right end of the drawing toward the left end of the drawing at least in the sliding range in which the elastic ring 30 is engaged. FIG. Here, the range indicated as “sliding range” is the range of the outer peripheral surface of the piston that is slidably engaged with the elastic ring 30 according to the worn state while the pads 20 and 24 are worn from the new state. Indicates the area. The waveform from “rough” to “fine” in the upper part of FIG. 2 shows the state of the surface finish of the outer peripheral surface of the piston in an enlarged manner.

  As shown in the figure, if the surface roughness of the outer peripheral surface of the piston 16 changes from coarse to fine from the right end of the figure to the left end of the figure at least within the above-mentioned sliding range, the pad 20 And 24 are still new, their wear is small, their elasticity is high, and the amount of compression recovery is large, the elastic ring 30 engages with the piston outer peripheral surface in a region where the surface roughness is rough, A large frictional engagement force is generated between them, and the piston is largely pulled back by the elastic ring when the brake is released. However, the use of the pads 20 and 24 progresses, the wear amount increases, and the elasticity decreases, and the amount of restoration with respect to compression. Is reduced, the elastic ring 30 engages with the outer peripheral surface of the piston in a region with a fine surface roughness to generate a small frictional engagement force with the piston. Ri so the piston is pulled back low. In this way, even if the degree of wear of the pad progresses, it is possible to suppress a change in the distance of the pad from the disk when the brake is released.

  FIG. 3 shows an embodiment in which the circumferential length of the outer peripheral surface of the piston 16 decreases from the right end of the drawing toward the left end of the drawing at least in a sliding range where the piston 16 engages with the elastic body ring 30. It is explanatory drawing which shows a form. In the illustrated example, the circumferential length of the piston outer peripheral surface is reduced by reducing the diameter of the piston outer peripheral surface. (In FIG. 3, the reduction in diameter is shown with a greater emphasis than actual.) As described above, the circumferential length of the outer peripheral surface of the piston is at least in the sliding range where the elastic ring 30 is engaged. If the elastic body ring 30 is reduced from the right end of the figure toward the left end of the figure, the elastic ring 30 is engaged with the piston outer peripheral surface in a state of being at least somewhat stretched. At the right end of the sliding range with a large length, a large frictional engagement force is generated between the elastic ring and the piston, and at the left end of the sliding range with a small peripheral length of the outer peripheral surface of the piston. In this case, a small frictional engagement force can be generated between the elastic ring and the piston.

  Although the present invention has been described in detail with reference to two embodiments, it will be apparent to those skilled in the art that various modifications can be made to these embodiments within the scope of the present invention.

1 is a schematic longitudinal sectional view showing a disc brake according to an embodiment of the present invention. An embodiment in which the surface roughness of the outer peripheral surface of the piston changes from coarse to fine from the right end of the figure to the left end of the figure at least in the sliding range where it engages with the elastic ring. FIG. Explanatory drawing which shows embodiment which the circumference of the outer peripheral surface of a piston decreases from the right end of a figure toward the left end of a figure at least in the sliding range engaged with an elastic body ring.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Caliper, 12 ... Cylinder chamber, 14 ... Pad support part, 16 ... Piston, 18 ... Pad support plate, 20 ... Pad, 22 ... Pad support plate, 24 ... Pad, 26 ... Disc, 28 ... Ring groove, 30 ... Elastic ring

Claims (3)

  It has a structure in which a disk is pressed by a caliper and a piston through a pad to brake its rotation, and when the piston is driven to a braking position for pressing the disk during braking, it frictionally engages with the outer peripheral surface of the piston. Friction engagement force that the outer peripheral surface of the piston exerts on the elastic ring is a disc brake in which the piston is pulled back from the braking position when braking is released by elastic restoring force of elastic deformation generated in the elastic ring. The disc brake is characterized in that it decreases with the progress of wear of the pad.   The frictional engagement force that the outer peripheral surface of the piston exhibits to the elastic ring decreases with the progress of wear of the pad, and the surface roughness that the outer peripheral surface of the piston exhibits to the elastic ring changes from coarse to fine. The disc brake according to claim 1, wherein The decrease in the frictional engagement force exhibited by the outer peripheral surface of the piston with respect to the elastic ring with the progress of wear of the pad is due to the decrease in the peripheral length that the outer peripheral surface of the piston exhibits with respect to the elastic ring. The disc brake according to claim 1, wherein:

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