JP6120588B2 - Disc brake - Google Patents

Description

  The present invention relates to a disc brake.

  Patent Literature 1 discloses a disc brake including a piston in which a chromium plating layer is formed on the outer peripheral surface of an aluminum alloy piston base. The piston of the disc brake is formed in a cup shape with an opening on the pad side, and a chromium plating layer is formed on the outer peripheral surface of the piston by an electrolytic plating method using a cylindrical anode.

JP 2006-292119 A

  When a chromium plating layer is formed on the outer peripheral surface of such a piston, the current density distribution at the time of energization is such that the current density at the outer peripheral side corner of the opening side (pad side) end of the piston is higher than the outer peripheral surface. . As a result, in order to form a film with the target film thickness on the outer peripheral surface of the piston, energization time significantly exceeding the standard energization time at the target film thickness is required, and the productivity of the disc brake is reduced. there were. An object of this invention is to provide the disc brake which improved productivity.

In order to solve the above problems, a disc brake according to the present invention includes a cylinder having one end opened, a piston slidably provided in the cylinder, and a pad pressed against the disc rotor by the piston. The piston has a cup shape with an opening on the pad side, a convex curved surface continuous with the outer peripheral surface at an outer peripheral side corner of the opening side end, and an inner peripheral side corner of the opening side end. is formed with a curved convex shape, have at least the plating layer on the outer peripheral surface, the curvature of the outer peripheral corner portion may be smaller than the curvature of the inner peripheral side corner portion.

  According to the present invention, the productivity of the disc brake can be improved.

It is explanatory drawing of the disc brake of this embodiment. It is sectional drawing by the axial plane of the piston of the disc brake of this embodiment. It is a figure which expands and shows the opening side edge part of the piston shown by FIG. 2 partially. It is a figure corresponding to FIG. 3 in the piston of the conventional disc brake. It is explanatory drawing of the plating apparatus for surface-treating at least the outer peripheral surface of the piston of a disk brake by the electrolytic plating method. It is sectional drawing by the axial plane of the outer peripheral side corner | angular part of the opening side edge part of the piston of the conventional disc brake immediately after forming a membrane | film | coat at least on an outer peripheral surface using the plating apparatus shown by FIG. 5 (before grinding process). . It is a figure corresponding to FIG. 6 in the piston of the disc brake of this embodiment.

  An embodiment of the present invention will be described with reference to the accompanying drawings. The disc brake illustrated in FIG. 1 is a so-called caliper floating disc brake, and includes a caliper 1, a disc rotor 2, and a pair of brake pads 3 and 4 disposed on both sides of the disc rotor 2. The caliper 1 and the brake pads 3 and 4 are supported by a carrier (not shown) fixed to the non-rotating part of the vehicle so as to be movable in the axial direction of the disk rotor 2 (left and right direction in FIG. 1). The caliper 1 includes a caliper body 5, a bottomed bore 6 provided at an end of the caliper body 5 on the inner side of the vehicle body (right side in FIG. 1), and a piston slidably provided in the bore 6 via a piston seal 7. 8. The piston 8 is formed in a bottomed cylindrical shape (cup shape) with an opening on the pad side (left side in FIG. 1). In the disc brake of this embodiment, the bore 6 is formed in the caliper body 5 to constitute a cylinder having one end opened.

  A claw portion 9 is provided at the tip of the caliper body 5. The claw portion 9 is formed to face the brake pad 4 disposed on the outside of the vehicle body (left side in FIG. 1). Each brake pad 3 and 4 is comprised by each back plate 3a, 4a and each lining material 3b, 4b joined to each back plate 3a, 4a. A hydraulic chamber 10 is defined by the bore 6 and the piston 8 of the caliper body 5. In the present embodiment, the brake fluid is supplied to the hydraulic pressure chamber 10 according to the operation of the brake pedal, so that the piston 8 propels the caliper body 5. As a result, the brake pad 3 disposed on the inner side of the vehicle body (right side in FIG. 1) is pressed against the inner surface of the disk rotor 2 (right side surface in FIG. 1), and the reaction force generated thereby causes the caliper body 5 to move. Move to the inside of the car. As a result, the brake pad 4 on the outer side of the vehicle body is pressed against the outer surface of the disc rotor 2 (the left side surface in FIG. 1) by the claw portion 9, and the disc rotor 2 is clamped by the pair of brake pads 3 and 4. As a result, a braking force is generated in the vehicle.

  Here, the piston 8 used for the disc brake of this embodiment will be described in more detail. The piston 8 is obtained by subjecting a piston base 11 made of an aluminum alloy (for example, A6061) to surface treatment by an electrolytic plating method. On at least the outer peripheral surface 12 of the piston 8, for example, a film 13 (see FIG. 7) obtained by laminating a chromium plating layer on an anodized film layer is formed. As shown in FIG. 2, the piston 8 has a pressure receiving surface 14 that receives the pressure of the brake fluid supplied to the hydraulic pressure chamber 10. A chamfered portion 16 having a rounded chamfer is formed at a corner of the non-opening side (right side in FIG. 2) end portion 15 of the piston 8. That is, the chamfered portion 16 has a convex curved surface (hereinafter, curved surface 16 as necessary) having a constant curvature that is smoothly continuous with the outer peripheral surface 12 and is smoothly continuous with the pressure-receiving surface 14 formed in a circle.

  As shown in FIG. 3, the chamfered surface is rounded at the outer peripheral side (upper side in FIG. 3) of the end portion 17 of the piston 8 on the opening side (left side in FIG. 3 and the pad side in FIG. 1). Part 18 is formed. That is, the chamfered portion 18 has a convex curved surface (hereinafter, curved surface 18 as necessary) having a constant curvature that is smoothly continuous with the outer peripheral surface 12 and is smoothly continuous with the opening-side end surface 19 formed in an annular shape. Have. Further, a chamfered portion 20 having an R-chamfer is formed at an inner peripheral side (lower side in FIG. 3) corner portion of the opening-side end portion 17 of the piston 8. That is, the chamfered portion 20 has a convex curved surface having a constant curvature (hereinafter, referred to as a curved surface 20 as needed) that is smoothly continuous with the inner peripheral surface 21 and is smoothly continuous with the end surface 19 on the opening side.

  In the present embodiment, the piston 8 is set such that the curvature of the curved surface 18 at the outer peripheral side corner portion of the opening side end portion 17 is smaller than the curvature of the curved surface 20 at the inner peripheral side corner portion of the opening side end portion 17. In other words, the radius of curvature of the curved surface 18 at the outer peripheral side corner portion of the opening side end portion 17 is set larger than the curvature radius of the curved surface 20 at the inner peripheral side corner portion of the opening side end portion 17. In other words, in the state where the piston 8 shown in FIG. 1 is inserted into the bore 6, the start position P20 on the inner peripheral surface 21 of the piston 8 of the curved surface 20 of the inner peripheral side corner of the opening-side end 17 is: The curved surface 18 of the outer peripheral side corner portion of the opening side end portion 17 is on the pad side (left side in FIGS. 1 to 3) from the start position P18 on the outer peripheral surface 12 of the piston 8. As shown in FIG. 2, the piston 8 has a concave curved surface 23 with a constant curvature that is smoothly continuous with the inner peripheral surface 21 and smoothly connected with the bottom surface 22. Further, the curvature of the curved surface 23 is set smaller than the curvature of the curved surface 16. Further, the curvature of the curved surface 16 is set to be equal to or less than the curvature of the curved surface 18.

  Next, the operation of this embodiment will be described. The piston 8 of the disc brake of this embodiment exemplified here has an outer diameter of 32 mm, a height (length in the axial direction) of 22.2 mm, an inner diameter of 25 mm, and an outer peripheral side corner of the opening side end 17. The curvature radius of the curved surface 18 is R0.5 to R1.5, and the curvature radius of the curved surface 20 at the inner peripheral side corner of the opening-side end 17 is R0.5 or less. FIG. 5 is an explanatory view of a plating apparatus 24 used for surface treatment of the disc brake piston 8 by electrolytic plating. As shown in this figure, the plating apparatus 24 contains a solution 25. A container 26, a cylindrical electrode 27 disposed in the solution 25, a DC power source 28 for energizing between the electrode 27 (anode) and the piston base 11 (cathode) disposed inside the electrode 27, Have

  Furthermore, in order to facilitate understanding of the operation of the present embodiment, a conventional disc brake piston 29 as a comparison target will be described. FIG. 4 is a view corresponding to FIG. 3 illustrating the opening end 17 of the piston 8 of the disc brake of the present embodiment, and is the opening end (left side in FIG. 4) of the piston 29 of the conventional disc brake. It is sectional drawing by 30 axial planes. As shown in FIG. 4, a chamfered portion 31 that is chamfered by C chamfering (C0.1 to C0.3) is provided at the outer peripheral side (upper side in FIG. 4) corner of the opening end 30 of the piston 29. It is formed. Further, a chamfered portion 32 that is chamfered by C chamfering (C0.1 to C0.6) is formed at the inner peripheral side (lower side in FIG. 4) corner portion of the opening side end portion 30 of the piston 29. The other dimensions (outer diameter, height, etc.) of the piston 29 of the conventional disc brake are the same as the piston 8 of the disc brake of this embodiment.

  Here, FIG. 6 shows the opening side of the piston 29 of the conventional disc brake (FIG. 6) immediately after forming the coating 34 on at least the outer peripheral surface 33 (before grinding) using the plating apparatus 24 shown in FIG. 7 is a cross-sectional view of the outer peripheral side (upper side in FIG. 6) corner portion of the end portion 30 by an axial plane. 7 shows the opening side (left side in FIG. 7) end of the piston 8 of the disc brake of the present embodiment immediately after forming the coating 13 on at least the outer peripheral surface 12 using the plating apparatus 24 shown in FIG. It is sectional drawing by the axial plane of the outer peripheral side (upper side in FIG. 7) corner | angular part of the part 17. FIG. Here, in this embodiment, the target film thickness of the film 13 formed on the outer peripheral surface 12 of the piston 8 and the film 34 formed on the outer peripheral surface 33 of the piston 29 will be described as 50 μm.

  As can be understood from FIG. 6, in the conventional disk brake piston 29, when the plating device 24 is used to form a film 34 having a target film thickness of 50 μm on the outer peripheral surface 33, the outer peripheral side of the opening-side end portion 30. The film thickness of the corner (the chamfered portion 31) is twice or more the target film thickness (film thickness of 120 to 300 μm). Such a variation in film thickness is caused by a variation in current density distribution during energization, and in the piston 29 of the conventional disc brake, it is a C-chamfered outer peripheral side corner of the opening side end 30. Since the current density of the chamfered portion 31 is high and the current density of the outer peripheral side corner portion is increased, the current density of the outer peripheral surface 33 is decreased.

  As a result, if the current density distribution is uniform, a film 34 having a target film thickness of 50 μm is usually obtained on the outer peripheral surface 33 in a current application time of 50 to 60 minutes. In order to form the film 34 having the target film thickness on the outer peripheral surface 33 having a lower current density than that at the corner portion, energization time (125 minutes) more than twice is required, which hinders reduction of man-hours. Further, in the piston 29 of the conventional disc brake, the film thickness at the outer peripheral side corner portion becomes excessive, and surface roughness due to precipitation abnormality, so-called kogation is likely to occur. Further, in the conventional disc brake piston 29, when the outer periphery of the piston 29 on which the film 34 is formed is ground, the grinding time is reduced because the film thickness of the outer peripheral side corner portion (the chamfered portion 31) is increased. It has come to take.

  On the other hand, as can be understood from FIG. 7, in the piston 8 of the disc brake of this embodiment, when the coating 13 having the target film thickness (50 μm) is formed on the outer peripheral surface 12 using the plating device 24, the outer periphery Even in the portion where the film 13 of the chamfered portion 18 which is a side corner portion has the largest film thickness, the film thickness was 100 μm. That is, in the piston 8 of the disc brake of this embodiment, the outer peripheral side corner of the opening side end 17 and the outer peripheral surface 12 are smoothly continued by the convex curved surface 18, so that the piston 8 of the piston 8 is electroplated. In the case where the coating 13 is formed on at least the outer peripheral surface 12, the variation in current density distribution between the outer peripheral surface 12 and the outer peripheral corner portion of the opening-side end portion 17 during energization is eliminated. It can be made uniform.

  According to the disc brake of the present embodiment, the convex curved surface 18 that is smoothly continuous with the outer peripheral surface 12 is formed at the outer peripheral side corner of the opening end 17 of the piston 8, so that the piston 8 of the piston 8 is electroplated. In the case where the film 13 is formed at least on the outer peripheral surface 12, the variation in the current density distribution between the outer peripheral surface 12 and the outer peripheral side corner of the opening-side end portion 17 during energization is eliminated. Uniformity can be achieved, and segregation of plating at the outer peripheral side corners of the opening end 17 can be prevented.

  Thereby, compared with the piston 29 of the conventional disc brake in which the chamfered portion 31 by C chamfering is formed at the outer peripheral side corner portion of the opening side end portion 30, the electrolytic plating treatment time (energization time) can be greatly shortened. Therefore, the number of steps for the piston 8 can be greatly reduced. In addition, the current value of electrolytic plating can be increased as compared with the piston 29 of the conventional disc brake, and the productivity of the piston 8 and thus the disc brake can be increased.

  Further, in the conventional disc brake piston 29, the current density at the outer peripheral side corner portion (the chamfered portion 31) of the opening side end portion 30 is higher than the current density of the outer peripheral surface 33 when the electroplating is energized. Although it is easy to generate kogation due to precipitation abnormalities in the part, the piston 8 of the disc brake of this embodiment can prevent the generation of kogation at the outer peripheral side corners. Peeling from the segregated portion of the film can be suppressed.

  Furthermore, in the piston 8 of the disc brake according to the present embodiment, when the outer periphery of the piston 8 is ground, the film thickness of the chamfered portion 18 that is the outer peripheral side corner portion is smaller than that of the piston 29 of the conventional disc brake. Accordingly, the grinding time can be shortened, and the productivity of the disc brake can be increased in this respect as well.

  Also, in disc brakes, the piston should not come into contact with the brake pad back plate or the shim attached to the back plate as a counterpart due to uneven wear, warpage, or caliper deformation of the brake pad. There is a case. In such a case, the piston comes into contact with the mating part not at the pad facing surface but at the outer peripheral side corner. In the present embodiment, the piston 8 has an R chamfer with a relatively large radius of curvature at the chamfered portion 18 which is a corner portion on the outer peripheral side even when the piston 8 does not vertically contact the counterpart part as described above. For this reason, the contact area with the counterpart component becomes larger than that of the conventional piston 29 due to elastic deformation. For this reason, the surface pressure of the chamfered portion 18 can be relatively lowered. Thereby, a deformation | transformation, damage, etc. of an other party part can be suppressed, and a deformation | transformation, plating peeling, etc. of the outer peripheral side corner | angular part of piston 8 can be suppressed.

  The present invention is not intended to be limited to the above embodiment, and can be configured as follows, for example.

  In the present embodiment, the disc brake is configured by forming a convex curved surface 20 that smoothly continues to the inner peripheral surface 21 at the inner peripheral side corner of the opening side (pad side) end 17 of the piston 8. Instead of the curved surface 20 by R chamfering, a chamfering portion 20 by C chamfering may be formed at the inner peripheral side corner portion to constitute a disc brake.

1 Caliper, 2 Disc rotor, 3, 4 Brake pad, 8 Piston, 12 Outer peripheral surface, 13 Coating, 17 Open side end, 18 Chamfered portion (curved surface)

Claims (2)

A disc brake having a cylinder having an open end, a piston slidably provided in the cylinder, and a pad pressed against the disc rotor by the piston,
The piston has a cup shape with an opening on the pad side, a convex curved surface continuous with the outer peripheral surface at the outer peripheral side corner portion of the opening side end portion, and a convex curved surface at the inner peripheral side corner portion of the opening side end portion. : it is formed, to have at least the plating layer on the outer peripheral surface,
The disc brake characterized in that a curvature of the outer peripheral side corner is smaller than a curvature of the inner peripheral side corner . A disc brake having a cylinder having an open end, a piston slidably provided in the cylinder, and a pad pressed against the disc rotor by the piston,
The piston has a cup shape with an opening on the pad side, a convex curved surface continuous with the outer peripheral surface at the outer peripheral side corner portion of the opening side end portion, and a flat or convex shape at the inner peripheral side corner portion of the opening side end portion. is a chamfered portion formed of a curved surface is formed, at least plating layer on the outer peripheral surface,
The starting position of the chamfer, features and to Lud Isukubureki that than the starting position of the curved surface of the outer peripheral corner the convex shape formed on the unit a pad side.

Images