Piston for disc brake device, and disc brake device

Abstract

To provide a piston for a disc brake device that can make it difficult for heat to be transmitted to a piston seal, can be made lighter, and can ensure rigidity.SOLUTION: A piston 3 has an overall cylindrical shape with a bottom, and comprises a cylindrical wall part 15, a bottom part 16, and a plurality of columnar ribs 17. The cylindrical wall part 15 has: an outer diameter side cylindrical part 19 having a seal slide contact part 22 on an outer peripheral surface; an inner diameter side cylindrical part 20 arranged radially inside the outer diameter side cylindrical part 19, and having a pad contact part 24 at an end part on the other side in an axial direction that protrudes in the axial direction with respect to the outer diameter side cylindrical part 19; and an annular gap 21 provided between the outer diameter side cylindrical part 19 and the inner diameter side cylindrical part 20. The plurality of columnar ribs 17 is arranged at an angle with respect to a piston center axis O3, where an end part on one side in a longitudinal direction is connected to a side surface of the bottom part 16 on the other side in the axial direction, and an end part on the other side in the longitudinal direction is connected to an inner peripheral surface of the inner diameter side cylindrical part 20.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a piston for a disc brake device and a disc brake device. [Background technology]

[0002] Disc brake systems are widely used to brake automobiles and motorcycles. When a disc brake system applies brakes, a pair of pads, located on either side of a rotor that rotates with the wheel, are pressed against both sides of the rotor by a piston. Friction between the pads and the rotor converts the vehicle's kinetic energy into thermal energy, braking the vehicle. This causes heat to accumulate in the rotor. While the heat accumulated in the rotor is dissipated to the surrounding area, some of it is transferred to the piston via the pads and then to the brake oil and piston seal.

[0003] Known examples of such disc brake devices include floating-type disc brake devices and opposed-piston-type disc brake devices.

[0004] FIG. 10 shows an opposed piston type disc brake device 100 of a conventional structure, which is described in Japanese Patent Application Laid-Open No. 2011-179676.

[0005] The disc brake device 100 includes a caliper 101 fixed to the vehicle body and a plurality of pistons 102.

[0006] The caliper 101 includes an inner body 104 and an outer body 105 on either side of a rotor 103 that rotates together with the wheel. The inner body 104 and the outer body 105 each include a cylinder 106.

[0007] The piston 102 is fitted into a cylinder 106. A piston seal 107 seals the gap between the piston 102 and the cylinder 106.

[0008] The piston 102 is configured as a cylinder with a bottom as a whole, and includes a cylindrical wall portion 108 having a substantially cylindrical shape, and a bottom portion 109. The bottom portion 109 closes one end of the cylindrical wall portion 108 that is located on the far side of the cylinder 106.

[0009] In the conventional structure described in JP 2011-179676 A, the structure of the cylindrical wall portion 108 that constitutes the piston 102 is devised to make it difficult for heat transferred from the pads 110a and 110b to the piston 102 to be transferred to the piston seal 107.

[0010] Specifically, the cylindrical wall portion 108 is composed of an outer diameter side cylindrical portion 111 whose outer peripheral surface is in sliding contact with the piston seal 107, an inner diameter side cylindrical portion 112 whose tip portion presses against the pads 110a and 110b, and an annular gap 113 provided between the inner peripheral surface of the outer diameter side cylindrical portion 111 and the outer peripheral surface of the inner diameter side cylindrical portion 112.

[0011] When braking, the disc brake device 100 sends brake oil from the master cylinder to the cylinder 106. This pushes out the piston 102 fitted in the cylinder 106 of the inner body 104, pressing the inner pad 110a supported by the caliper 101 against the side of the rotor 103. Similarly, the piston 102 fitted in the cylinder 106 of the outer body 105 is pushed out, pressing the outer pad 110b supported by the caliper 101 against the side of the rotor 103. As a result, the rotor 103 is tightly clamped between the pair of pads 110a, 110b, thereby braking the vehicle.

[0012] In a disc brake device 100 with a conventional structure, the cylindrical wall portion 108 that constitutes the piston 102 is divided into an outer diameter side cylindrical portion 111 that comes into sliding contact with the piston seal 107 and an inner diameter side cylindrical portion 112 that presses against the pads 110a, 110b, which makes it difficult for heat to be transferred from the pads 110a, 110b to the piston seal 107. This makes it possible to suppress a temperature rise in the piston seal 107 and to suppress deterioration of the piston seal 107. In addition, heat from the pads 110a, 110b is difficult to transfer to the brake oil, making it possible to suppress a temperature rise in the brake oil. [Prior art documents] [Patent documents]

[0013] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-179676 Summary of the Invention [Problem to be solved by the invention]

[0014] The disc brake device 100 with the conventional structure described in JP 2011-179676 A can suppress the temperature rise of the brake oil and also make it difficult for heat to be transferred to the piston seal 107. However, because the cylindrical wall portion 108 that constitutes the piston 102 has a hollow structure, there is a possibility that the rigidity may be insufficient.

[0015] On the other hand, because the disc brake device is located closer to the road surface than the springs that make up the suspension of the vehicle, it is subject to what is known as an unsprung load. For this reason, it is also necessary to reduce the weight of the pistons that make up the disc brake device in order to improve the fuel efficiency and driving performance of the vehicle.

[0016] The present disclosure aims to provide a piston for a disc brake device that can suppress a rise in temperature of brake oil and make it difficult for heat to be transmitted to a piston seal, as well as ensure rigidity while suppressing an increase in weight. [Means for solving the problem]

[0017] A piston for a disc brake device according to one aspect of the present disclosure is fitted into a cylinder of a caliper that constitutes a disc brake device such as an opposed piston type or a floating type.

[0018] A piston for a disc brake device according to one aspect of the present disclosure is configured as a cylinder with a bottom as a whole, and includes a cylindrical wall portion having an approximately cylindrical shape, a bottom portion that closes one axial end of the cylindrical wall portion that is located at the rear side of the cylinder, and a plurality of columnar ribs that are located radially inward of the cylindrical wall portion.

[0019] The cylindrical wall portion has an outer diameter side cylindrical portion having a seal sliding portion on its outer peripheral surface, an inner diameter side cylindrical portion arranged radially inside the outer diameter side cylindrical portion and having a pad abutment portion at its other axial end portion that protrudes axially further than the other axial end portion of the outer diameter side cylindrical portion, and an annular gap provided between the inner peripheral surface of the outer diameter side cylindrical portion and the outer peripheral surface of the inner diameter side cylindrical portion.

[0020] The multiple columnar ribs are arranged at an angle to the piston center axis, with one end of each in the longitudinal direction connected to the side surface on the other axial side of the bottom portion, and the other end of each in the longitudinal direction connected to the inner surface of the inner diameter side cylindrical portion.

[0021] In a piston for a disc brake device according to one aspect of the present disclosure, the other longitudinal end of each of the plurality of columnar ribs is connected to the other axial end of the inner circumferential surface of the inner diameter side cylindrical portion.

[0022] In the piston for a disc brake device according to one aspect of the present disclosure, the plurality of columnar ribs are arranged radially around the piston central axis.

[0023] In a piston for a disc brake device according to one aspect of the present disclosure, the end of each of the plurality of columnar ribs on one longitudinal side is connected to the radial middle portion of the side surface on the other axial side of the bottom portion.

[0024] In the piston for a disc brake device according to one aspect of the present disclosure, the plurality of columnar ribs are arranged at equal intervals in the circumferential direction.

[0025] In the piston for a disc brake device according to one aspect of the present disclosure, the outer diameter side cylindrical portion, the inner diameter side cylindrical portion, and the plurality of columnar ribs are integrally formed.

[0026] In a piston for a disc brake device according to one aspect of the present disclosure, the outer diameter side cylindrical portion and the inner diameter side cylindrical portion are configured separately, and the inner diameter side cylindrical portion and the multiple columnar ribs are configured integrally.

[0027] In the piston for a disc brake device according to one aspect of the present disclosure, the inner diameter side cylindrical portion has a communication hole penetrating therethrough in the radial direction.

[0028] In the piston for a disc brake device according to one aspect of the present disclosure, the communication hole is provided in a portion of the inner diameter side cylindrical portion that coincides in phase with the columnar rib in the circumferential direction.

[0029] In the piston for a disc brake device according to one aspect of the present disclosure, the communication hole is provided in the inner diameter side cylindrical portion near a connection portion with the other longitudinal end portion of the columnar rib.

[0030] In the piston for a disc brake device according to one aspect of the present disclosure, the communication hole is provided in a portion adjacent to one axial side of the connection portion.

[0031] In the piston for a disc brake device according to one aspect of the present disclosure, at least a portion of the communication hole is located on the other axial side of the other axial end of the outer diameter side cylindrical portion.

[0032] In the piston for a disc brake device according to one aspect of the present disclosure, the central axis of the communication hole is inclined with respect to the central axis of the piston in a direction that approaches one axial side as it moves radially inward.

[0033] In a piston for a disc brake device according to one aspect of the present disclosure, a heat shield plate is provided radially inside the inner diameter side cylindrical portion, and the heat shield plate covers the other axial side surface of the bottom portion while abutting against the multiple columnar ribs.

[0034] In the piston for a disc brake device according to one aspect of the present disclosure, the heat shield plate is engaged with the plurality of columnar ribs.

[0035] In a piston for a disc brake device according to one aspect of the present disclosure, the plurality of columnar ribs each have an engagement protrusion in a portion of their length, and the heat shield has an engagement hole in which the engagement protrusion engages.

[0036] A disc brake device according to one aspect of the present disclosure includes a caliper having a cylinder, and a piston fitted in the cylinder. In the disc brake device according to one aspect of the present disclosure, the piston is a piston for a disc brake device according to one aspect of the present disclosure. [Effects of the Invention]

[0037] According to the piston for a disc brake device according to one aspect of the present disclosure, it is possible to suppress a rise in the temperature of the brake oil, make it difficult for heat to be transmitted to the piston seal, achieve weight reduction, and ensure rigidity. [Brief explanation of the drawings]

[0038] [Figure 1] FIG. 1 is a cross-sectional view showing a disc brake device according to a first embodiment of the present disclosure. [Figure 2] FIG. 2 is a front view showing the piston of the first example. [Figure 3]FIG. 3 is a cross-sectional view taken along line AA in FIG. [Figure 4] FIG. 4 is a perspective view showing the piston of the first example. [Figure 5] FIG. 5 is a front view showing the piston body of the first example. [Figure 6] FIG. 6 is a combined view of the cross section taken along line BOB in FIG. 5 and the cross section taken along line COC in FIG. [Figure 7] FIG. 7 is a perspective view showing the piston body of the first example. [Figure 8] FIG. 8 is a perspective view showing the piston body of the first example at a different circumferential position from that of FIG. [Figure 9] FIG. 9 is a cross-sectional view showing a piston body according to a second example of an embodiment of the present disclosure. [Figure 10] FIG. 10 is a cross-sectional view showing a disc brake device of a conventional structure. DETAILED DESCRIPTION OF THE INVENTION

[0039] [Example 1] A first example of an embodiment of the present disclosure will be described with reference to FIGS.

[0040] In this example, a case will be described in which a piston for a disc brake device according to one aspect of the present disclosure is applied to an opposed-piston type disc brake device used for braking an automobile.

[0041] However, the piston for a disc brake device according to one aspect of the present disclosure is not limited to opposed piston type disc brake devices, and can also be applied to other disc brake devices, such as floating type disc brake devices.

[0042] The overall structure of the disc brake device 1 will be described below, and then the structure of the piston 3 of this example will be described in detail.

[0043] In the following description of the disc brake device 1, the axial direction, circumferential direction, and radial direction refer to the axial direction, circumferential direction, and radial direction of the disc-shaped rotor 5 (see FIG. 1) that rotates together with the wheel, unless otherwise specified. In FIG. 1, the left-right direction corresponds to the axial direction, the front-to-back direction corresponds to the circumferential direction, and the up-to-down direction corresponds to the radial direction. Furthermore, the right side of FIG. 1, which is the center side of the vehicle body when assembled to the vehicle body, is referred to as the axially inner side, and the left side of FIG. 1, which is the outside of the vehicle body when assembled to the vehicle body, is referred to as the axially outer side.

[0044] The disc brake device 1 of this example includes a caliper 2, a plurality of pistons 3, and a pair of pads 4a, 4b.

[0045] The caliper 2 is supported and fixed to a knuckle of a suspension device in a state in which it covers the rotor 5 from the radial outside. The caliper 2 supports a pair of pads 4a, 4b so that they are movable in the axial direction.

[0046] The caliper 2 is integrally formed by casting a material made of a light alloy such as an aluminum alloy or an iron-based alloy.

[0047] The caliper 2 includes an inner body 6 and an outer body 7 disposed on either side of the rotor 5, and a bridge 8 connecting the inner body 6 and the outer body 7 in the axial direction.

[0048] The inner body 6 is disposed axially closer to the center of the vehicle body than the rotor 5. The outer body 7 is disposed axially outside the vehicle body than the rotor 5. The bridge 8 is disposed radially outside the rotor 5.

[0049] The inner body 6 and the outer body 7 each have a cylinder 9. The cylinder 9 is formed of a substantially cylindrical space. The cylinder 9 provided in the inner body 6 opens to the axially outer surface of the inner body 6. The cylinder 9 provided in the outer body 7 opens to the axially inner surface of the outer body 7. The inner body 6 and the outer body 7 have an oil passage (not shown) for sending brake oil from the master cylinder to the cylinder 9. The inner body 6 has a connection part 10 for connecting a brake hose between it and the master cylinder.

[0050] The inner body 6 and the outer body 7 have annular seal grooves 11 around the opening sides of the cylinder 9. A piston seal 12 made of an elastic material is fitted in the seal groove 11.

[0051] The piston 3 is fitted in a cylinder 9. Specifically, the piston 3 is fitted in each of the cylinders 9 provided in the inner body 6 and the outer body 7. A piston seal 12 seals the gap between the piston 3 and the cylinder 9.

[0052] In this example, the piston for a disc brake device according to one aspect of the present disclosure is fitted into both a cylinder provided in the inner body and a cylinder provided in the outer body. However, the opposed-type piston for a disc brake device according to one aspect of the present disclosure may also be fitted into only one of the cylinders provided in the inner body and the cylinder provided in the outer body.

[0053] Each of the pair of pads 4a, 4b includes a lining 13 and a metal backing plate 14 that supports the back surface of the lining 13. The back surface of the lining 13 refers to the axially inner surface of the lining 13 of the inner pad 4a, and refers to the axially outer surface of the lining 13 of the outer pad 4b. Of the pair of pads 4a, 4b, the inner pad 4a, which is positioned axially more inward than the rotor 5, is supported so as to be axially movable relative to the inner body 6. Of the pair of pads 4a, 4b, the outer pad 4b, which is positioned axially more outward than the rotor 5, is supported so as to be axially movable relative to the outer body 7.

[0054] When braking, the disc brake device 1 sends brake oil from the master cylinder to the cylinder 9. This pushes out the piston 3 fitted in the cylinder 9 of the inner body 6, pressing the lining 13 of the inner pad 4a against the axially inner side surface of the rotor 5. The cylinder 9 of the inner body 6 and the cylinder 9 of the outer body 7 are connected by tubing (not shown) or the like to form a hydraulic circuit, so that the piston 3 fitted in the cylinder 9 of the outer body 7 is similarly pushed out and presses the lining 13 of the outer pad 4b against the axially outer side surface of the rotor 5. As a result, the rotor 5 is tightly clamped in the axial direction by the linings 13 of the pair of pads 4a, 4b, thereby braking the vehicle.

[0055] The structure of the piston 3 of this example will be described in detail below.

[0056] In the following description, the axial direction, circumferential direction, and radial direction refer to the axial direction, circumferential direction, and radial direction of the piston 3 unless otherwise specified. The axial direction of the piston 3 coincides with the axial direction of the rotor 5. When the piston 3 is fitted in the cylinder 9, the inner side of the cylinder 9 is referred to as the one axial side, and the opening side of the cylinder 9 is referred to as the other axial side. That is, for the piston 3 fitted in the cylinder 9 of the inner body 6, the inner axial side corresponds to the one axial side, and the outer axial side corresponds to the other axial side. In contrast, for the piston 3 fitted in the cylinder 9 of the outer body 7, the outer axial side corresponds to the one axial side, and the inner axial side corresponds to the other axial side.

[0057] [Piston structure] The piston 3 has a piston central axis O3 and is configured as a cylinder with a bottom as a whole.

[0058] The piston 3 includes a cylindrical wall portion 15, a bottom portion 16, and a plurality of columnar ribs 17.

[0059] The piston 3 is manufactured by selective laser sintering (SLS) using metal powder such as titanium alloy, aluminum alloy, iron-based alloy, etc. However, the piston for a disc brake device according to one embodiment of the present disclosure can also be manufactured using various three-dimensional fabrication methods (such as fused deposition modeling, inkjet printing, powder bonding, stereolithography, laser direct deposition modeling (LENS), and fused metal deposition modeling (FDM)).

[0060] The piston 3 of this example is integrally formed with a cylindrical wall portion 15, a bottom portion 16, and a plurality of columnar ribs 17. The cylindrical wall portion 15, the bottom portion 16, and the plurality of columnar ribs 17 constitute a piston body 18, which is a single component.

[0061] When the piston 3 is not braking, the other axial end of the cylindrical wall portion 15 is exposed from the cylinder 9.

[0062] The cylindrical wall portion 15 has a substantially cylindrical shape and is hollow. In this example, the cylindrical wall portion 15 has a substantially U-shaped cross section.

[0063] The cylindrical wall portion 15 has an outer diameter side cylindrical portion 19, an inner diameter side cylindrical portion 20, and an annular gap 21.

[0064] In this example, the cylindrical wall portion 15 and the multiple columnar ribs 17 are integrally formed, so the outer diameter side cylindrical portion 19, the inner diameter side cylindrical portion 20 and the multiple columnar ribs 17 are integrally formed.

[0065] The outer diameter side cylindrical portion 19 forms the radially outer portion of the cylindrical wall portion 15 and has a substantially cylindrical shape. The outer peripheral surface of the outer diameter side cylindrical portion 19 forms the outer peripheral surface of the cylindrical wall portion 15 and is configured to have a cylindrical surface shape. The outer diameter of the outer diameter side cylindrical portion 19 is slightly smaller than the inner diameter of the cylinder 9. The radial thickness dimension of the outer diameter side cylindrical portion 19 is substantially constant along the axial direction.

[0066] The outer circumferential surface of the outer tubular portion 19 has a seal sliding contact portion 22. The seal sliding contact portion 22 is provided at an axially intermediate portion of the outer circumferential surface of the outer tubular portion 19. The seal sliding contact portion 22 is in sliding contact with the piston seal 12 in the axial direction.

[0067] The outer diameter side cylindrical portion 19 has a tapered surface 23 at the other axial end of the inner circumferential surface, the inner diameter of which increases toward the other axial side.

[0068] The inner diameter side cylinder portion 20 constitutes the radially inner portion of the cylindrical wall portion 15 and has a substantially cylindrical shape. The inner diameter side cylinder portion 20 is located radially inside the outer diameter side cylinder portion 19, and is arranged so that a large portion of it radially overlaps with the outer diameter side cylinder portion 19. The inner diameter side cylinder portion 20 is arranged coaxially with the outer diameter side cylinder portion 19. The inner diameter side cylinder portion 20 and the outer diameter side cylinder portion 19 are separated from each other radially and are connected only at one end on one axial side of each other.

[0069] In this example, the outer peripheral surface of the inner diameter side cylindrical portion 20 is configured as a concave curved surface having a concave arc cross section, in which the outer diameter smoothly decreases toward the middle portion in the axial direction. The inner peripheral surface of the inner diameter side cylindrical portion 20 is configured as a convex curved surface having a convex arc cross section, in which the inner diameter smoothly decreases toward the middle portion in the axial direction. However, when implementing a piston for a disc brake device according to one aspect of the present disclosure, the outer peripheral surface and the inner peripheral surface of the inner diameter side cylindrical portion may be configured as cylindrical surfaces.

[0070] In this example, the end portion on one axial side of the inner diameter side cylinder portion 20 is offset toward the other axial side from the end portion on one axial side of the outer diameter side cylinder portion 19. In other words, the end portion on one axial side of the outer diameter side cylinder portion 19 protrudes in the axial direction further than the end portion on one axial side of the inner diameter side cylinder portion 20. Specifically, the end portion on one axial side of the inner diameter side cylinder portion 20 is connected to a portion of the inner peripheral surface of the outer diameter side cylinder portion 19 that is closer to one axial side.

[0071] The other axial side portion of the inner diameter side cylindrical portion 20 protrudes in the axial direction further than the other axial end portion of the outer diameter side cylindrical portion 19. The inner diameter side cylindrical portion 20 has a pad abutment portion 24 at the other axial end portion. In this example, the portion of the inner diameter side cylindrical portion 20 including the pad abutment portion 24 that protrudes in the axial direction further than the other axial end portion of the outer diameter side cylindrical portion 19 is exposed from the cylinder 9 when not braking.

[0072] In this example, because the pad abutment portion 24 protrudes axially from the outer diameter side cylindrical portion 19, the outer diameter side cylindrical portion 19 does not come into direct contact with the pads 4a, 4b. This effectively prevents heat from the pads 4a, 4b from being directly transferred to the outer diameter side cylindrical portion 19 and reaching the brake oil. The portion of the piston 3 to which heat is directly transferred through contact with the pads 4a, 4b is the pad abutment portion 24. Therefore, in order for heat to be transferred from the pad abutment portion 24 to the piston seal 12, the heat must pass through the inner diameter side cylindrical portion 20 and the columnar rib 17, pass through the bottom portion 16, and then to the outer diameter side cylindrical portion 19, which provides a sufficiently long heat transfer distance. This effectively prevents heat transfer to the piston seal 12.

[0073] The pad contact portion 24 contacts the back plate 14 of the pads 4a, 4b. The radial thickness of the pad contact portion 24 is larger than the radial thickness of the inner diameter side cylindrical portion 20 at a position separate from the pad contact portion 24. The radial thickness of the inner diameter side cylindrical portion 20 at a position separate from the pad contact portion 24 is approximately the same as the radial thickness of the outer diameter side cylindrical portion 19.

[0074] The end face on the other axial side of the pad contact portion 24 has a circular ring shape and is configured as a flat surface on an imaginary plane perpendicular to the piston central axis O3.

[0075] The annular gap 21 is a circular gap provided between the inner peripheral surface of the outer diameter side cylindrical portion 19 and the outer peripheral surface of the inner diameter side cylindrical portion 20, and constitutes a so-called heat insulation and heat dissipation means. That is, the air layer present in the annular gap 21 is expected to provide a heat insulation effect, and heat dissipation is achieved by the movement of the air layer. The annular gap 21 opens to the other axial side. One axial end (axial bottom) of the annular gap 21 is located on one axial side of the seal sliding contact portion 22.

[0076] The radial thickness dimension of the annular gap 21 is approximately constant along the axial direction, but the radial thickness dimension of the portion where the tapered surface 23 is provided on the inner surface of the outer diameter side cylindrical portion 19 is larger than the radial thickness dimension of the other portions.

[0077] The bottom portion 16 closes one axial end of the cylindrical wall portion 15 that is located at the rear side of the cylinder 9. The bottom portion 16 has a generally circular plate shape. The outer peripheral edge of the bottom portion 16 is connected to the other axial end of the inner diameter side cylinder portion 20 that constitutes the cylindrical wall portion 15.

[0078] The side surface on one axial direction of the bottom portion 16 is configured as a partially spherical convex surface that bulges slightly toward one axial direction. The side surface on the other axial direction of the bottom portion 16 is configured as a partially spherical concave surface that is slightly recessed toward one axial direction. However, when implementing a piston for a disc brake device according to one embodiment of the present disclosure, the bottom portion may be configured as a flat plate.

[0079] The axial thickness of the bottom portion 16 is substantially constant in the radial and circumferential directions. In this example, the axial thickness of the bottom portion 16 is substantially the same as the radial thickness of the portion of the inner diameter side cylindrical portion 20 that is separated from the pad contact portion 24 and the radial thickness of the outer diameter side cylindrical portion 19.

[0080] The multiple columnar ribs 17 serve to ensure the rigidity of the piston 3. Specifically, the multiple columnar ribs 17 increase the rigidity of the inner diameter side cylindrical portion 20 of the cylindrical wall portion 15 that constitutes the piston 3, which presses against the pads 4a, 4b during braking.

[0081] The number of columnar ribs 17 is not limited to this, but the piston 3 can be provided with, for example, 3 to 12 columnar ribs 17. In this example, the piston 3 is provided with 6 columnar ribs 17.

[0082] The plurality of columnar ribs 17 are arranged radially inside the cylindrical wall portion 15. Specifically, the plurality of columnar ribs 17 are arranged in a piston internal space 25 that exists radially inside the inner diameter side cylinder portion 20 that constitutes the cylindrical wall portion 15.

[0083] The columnar rib 17 has a linear, elongated shape. In this example, the columnar rib 17 has a substantially trapezoidal cross-sectional shape and is configured as a quadrangular prism whose cross-sectional shape changes in the length direction. However, when implementing a piston for a disc brake device according to one embodiment of the present disclosure, the shape of the columnar rib is not particularly limited, and any shape can be adopted, such as a triangular prism, a rectangular prism, a trapezoidal prism, a polygonal prism such as a pentagonal prism or a hexagonal prism, a cylindrical prism, an elliptical prism, a truncated cone, or a truncated polygonal pyramid.

[0084] The columnar rib 17 is configured to be solid as a whole, but the columnar rib may also be configured to be hollow.

[0085] The plurality of columnar ribs 17 are arranged at an angle with respect to the piston central axis O3. 17 (See FIG. 3) is inclined with respect to the piston central axis O3.

[0086] The plurality of columnar ribs 17 have one end in the length direction connected to the side surface on the other axial side of the bottom portion 16, and the other end in the length direction connected to the inner peripheral surface of the inner diameter side cylindrical portion 20. Therefore, the central axis O of the columnar rib 17 is 17 is inclined radially outward relative to the piston central axis O3 from one side in the lengthwise direction to the other side in the lengthwise direction.

[0087] In this example, one longitudinal end of each of the plurality of columnar ribs 17 is connected to a radially intermediate portion of the side surface on the other axial side of the bottom portion 16, and the other longitudinal end is connected to the other axial end of the inner circumferential surface of the inner diameter side cylindrical portion 20. In other words, the other longitudinal end of each columnar rib 17 is connected to the pad abutment portion 24.

[0088] The columnar rib 17 is not connected to the bottom portion 16 or the inner diameter side cylindrical portion 20 at any portion other than the ends on both sides in the length direction.

[0089] In this example, the multiple columnar ribs 17 are arranged at equal intervals in the circumferential direction and are arranged radially around the piston central axis O3. The multiple columnar ribs 17 are arranged at intervals in the circumferential direction and are independent of each other. In other words, two columnar ribs 17 adjacent to each other in the circumferential direction are not connected to each other. However, two columnar ribs adjacent to each other in the circumferential direction may be connected to each other in the circumferential direction.

[0090] In this example, the thickness dimension t (see FIG. 3) of the columnar rib 17 in the radial direction decreases from one side in the length direction to the other side in the length direction.

[0091] The width dimension w of the columnar rib 17 in the circumferential direction (see FIG. 5) increases from one side in the length direction to the other side in the length direction, except for both ends of the columnar rib 17 in the length direction.

[0092] A first reinforcing portion 26a protruding radially and circumferentially is provided at one end of the longitudinal direction of the columnar rib 17. A second reinforcing portion 26b protruding circumferentially is provided at the other end of the longitudinal direction of the columnar rib 17.

[0093] In this example, an engagement protrusion 27 for attaching a heat shield plate 29 (described later) is provided on a portion of the columnar rib 17 in the longitudinal direction. The engagement protrusion 27 is provided on the radially inner surface of the longitudinal middle portion of the columnar rib 17, and protrudes radially inward. In this example, the engagement protrusion 27 is provided on all columnar ribs 17, but it is not necessary that all columnar ribs 17 have the engagement protrusion 27.

[0094] The engaging protrusion 27 is configured in a substantially triangular plate shape, however, the shape of the engaging protrusion is not limited to a triangular plate shape and other shapes such as a hemisphere may be adopted.

[0095] In the piston 3 of this example, the inner diameter side cylindrical portion 20 has a communication hole 28 penetrating in the radial direction. The communication hole 28 communicates between the annular gap 21 and the piston internal space 25. However, when implementing a piston for a disc brake device according to one aspect of the present disclosure, providing a communication hole in the inner diameter side cylindrical portion is optional.

[0096] The inner diameter side cylindrical portion 20 has a plurality of communication holes 28. In this example, the inner diameter side cylindrical portion 20 has the same number of communication holes 28 as the columnar ribs 17. However, the number of communication holes provided in the inner diameter side cylindrical portion does not have to be the same as the number of columnar ribs.

[0097] In this example, each of the plurality of communication holes 28 is provided in a portion of the inner diameter side cylindrical portion 20 whose phase in the circumferential direction coincides with that of the columnar rib 17. Therefore, the plurality of communication holes 28 are arranged at equal intervals in the circumferential direction.

[0098] The communication hole 28 is provided in the inner diameter side cylindrical portion 20 near the connection portion with the end portion on the other longitudinal side of the columnar rib 17. In this example, the communication hole 28 is provided in a portion of the inner diameter side cylindrical portion 20 adjacent to one axial side of the connection portion with the end portion on the other longitudinal side of the columnar rib 17. Here, the end portion on the other longitudinal side of the columnar rib 17 is connected to the end portion on the other axial side of the inner peripheral surface of the inner diameter side cylindrical portion 20, so the communication hole 28 is provided in a portion of the inner diameter side cylindrical portion 20 closer to the other axial side.

[0099] At least a portion of the communicating hole 28 is located on the other axial side of the other axial end of the outer diameter side cylindrical portion 19. In this example, the other axial half of the communicating hole 28 is located on the other axial side of the other axial end of the outer diameter side cylindrical portion 19. Therefore, in a non-braking state, the other axial half of the communicating hole 28 is exposed from the cylinder 9. The one axial half of the communicating hole 28 is covered from the radial outside by the outer diameter side cylindrical portion 19.

[0100] In this example, the communication holes 28 have a substantially rectangular opening shape when viewed in the radial direction. However, the opening shape of the communication holes is not limited to a rectangular shape and may be any shape, such as a circle, an ellipse, a triangle, or a polygon.

[0101] Central axis O of the communication hole 28 28 (See FIG. 6) is inclined in a direction toward one axial side as it moves radially inward with respect to the piston central axis O3. 28 The extension line of passes through the other axial side surface of the bottom portion 16.

[0102] The piston 3 of this example further includes a heat shield 29 in addition to the piston body 18. The heat shield 29 serves to suppress heat transfer from the pads 4a, 4b to the bottom 16. However, when implementing a piston for a disc brake device according to one embodiment of the present disclosure, the inclusion of a heat shield is optional.

[0103] The heat shield plate 29 is configured such that the cylindrical wall portion 15, the bottom portion 16, and the columnar ribs 17 are separate from each other. That is, the heat shield plate 29 is configured as a separate body from the piston body 18.

[0104] The heat shield plate 29 is made of a metal plate. In this example, the heat shield plate 29 is made by pressing a stainless steel plate.

[0105] The heat shield plate 29 is disposed radially inside the inner diameter side cylindrical portion 20 that constitutes the cylindrical wall portion 15. In other words, the heat shield plate 29 is disposed in the piston internal space 25.

[0106] The heat shield plate 29 covers the other axial side surface of the bottom portion 16 while abutting against the plurality of columnar ribs 17. In this example, the heat shield plate 29 abuts against the plurality of columnar ribs 17 by engaging with the columnar ribs 17.

[0107] The heat shield plate 29 has a cover portion 30 having a substantially circular plate shape and a plurality of engagement pieces 31 .

[0108] In this example, the heat shield 29 has half the number of engagement pieces 31 as the columnar ribs 17. However, the number of engagement pieces provided on the heat shield is not limited to half the number of columnar ribs. The multiple engagement pieces 31 are arranged at equal intervals in the circumferential direction.

[0109] The engagement piece 31 is configured in a substantially rectangular plate shape, and its base end is connected to the outer periphery of the lid part 30. The engagement piece 31 is bent in a direction approaching the piston central axis O3 from the base end side toward the tip end side.

[0110] The engagement piece 31 has an engagement hole 32 having a hole shape that can engage with the engagement protrusion 27. In this example, the engagement hole 32 is configured as a rectangular hole.

[0111] The heat shield plate 29 is arranged in the piston internal space 25 so as not to fall off, by engaging the engaging projections 27 with the engaging holes 32 provided in each of the plurality of engaging pieces 31 .

[0112] In this example, the cover 30 has a notch 33 between two circumferentially adjacent engagement pieces 31 on the outer periphery, through which the other axial side portion of the columnar rib 17 can be inserted. The cover 30 has a small hole 34 in its center, which can be engaged with the tip of a tool when removing the heat shield 29.

[0113] The piston 3 of this embodiment can suppress the temperature rise of the brake oil and make it difficult for heat to be transmitted to the piston seal 12, as well as ensure rigidity while suppressing an increase in weight.

[0114] That is, the cylindrical wall portion 15 constituting the piston 3 of this example is divided into an outer diameter side cylindrical portion 19 having a seal sliding contact portion 22 on its outer peripheral surface and an inner diameter side cylindrical portion 20 having a pad abutment portion 24 at the other axial end. This reduces the heat transfer from the pads 4a, 4b to the seal sliding contact portion 22. That is, in the piston 3 of this example, the heat transfer distance from the pad abutment portion 24 to the seal sliding contact portion 22 is longer than, for example, when the seal sliding contact portion and the pad abutment portion are provided on the same cylindrical portion, so that the heat from the pads 4a, 4b is less likely to be transferred to the seal sliding contact portion 22. In particular, in this example, the inner diameter side cylindrical portion 20 and the outer diameter side cylindrical portion 19 are connected only at one axial end of each, so the heat transfer distance is sufficiently long, and the heat from the pads 4a, 4b is less likely to be transferred to the seal sliding contact portion 22. This reduces the heat transfer to the piston seal 12. As a result, the temperature rise of the piston seal 12 is suppressed, and deterioration of the piston seal 12 is suppressed.

[0115] The piston 3 of this example is provided with a plurality of columnar ribs 17 to ensure rigidity, thereby ensuring the rigidity of the piston 3 while suppressing an increase in weight. In particular, the plurality of columnar ribs 17 are arranged at an angle with respect to the piston central axis O3, with one end of each of them in the longitudinal direction connected to a side surface on the other axial side of the bottom portion 16, and the other end of each of them in the longitudinal direction connected to the inner circumferential surface of the inner diameter side cylindrical portion 20. Therefore, the plurality of columnar ribs 17 are tensioned between the bottom portion 16 and the inner diameter side cylindrical portion 20, which includes pad contact portions 24 that press against the pads 4a, 4b during braking, and therefore the rigidity of the inner diameter side cylindrical portion 20, which is particularly required to have rigidity, can be sufficiently ensured.

[0116] A portion of the heat transferred from the pads 4a, 4b to the pad contact portions 24 is also transferred to the columnar ribs 17, so the amount of heat transferred to the bottom portion 16 is less than when the columnar ribs 17 are not provided. This makes it possible to suppress a rise in temperature of the brake oil present between the bottom portion 16 and the cylinder 9.

[0117] In the piston 3 of this example, a portion of the inner diameter side cylindrical portion 20 that protrudes in the axial direction beyond the other axial end of the outer diameter side cylindrical portion 19 is exposed from the cylinder 9 when not braking. In addition, the outer peripheral surface of the inner diameter side cylindrical portion 20 is configured as a concave curved surface in which the outer diameter smoothly decreases toward the middle portion in the axial direction. Therefore, when the vehicle is running, wind impinges on the portion of the outer peripheral surface of the inner diameter side cylindrical portion 20 that is exposed from the cylinder 9 and is guided along the outer peripheral surface of the inner diameter side cylindrical portion 20 to one axial side (the back side) of the annular gap 21. This cools the outer diameter side cylindrical portion 19, thereby suppressing a temperature rise in the piston seal 12.

[0118] Furthermore, the outer diameter side cylindrical portion 19 has a tapered surface 23 at the other axial end of the inner circumferential surface, which allows the traveling wind to easily enter the annular gap 21. Therefore, this surface also helps to suppress the temperature rise of the piston seal 12.

[0119] The piston 3 of this example has a communication hole 28 in the inner diameter side cylindrical portion 20. Therefore, the wind generated by running is guided through the communication hole 28 into the piston internal space 25. This allows the wind to be used to cool the bottom portion 16. Therefore, this also helps to suppress the temperature rise of the brake oil.

[0120] In this example, the communication holes 28 are provided in the inner diameter side cylindrical portion 20 at a portion where the phase in the circumferential direction coincides with the columnar ribs 17, so that the traveling wind that passes through the communication holes 28 hits the radially outer surfaces of the columnar ribs 17. As a result, the columnar ribs 17 are cooled, and the cooling wind is guided along the columnar ribs 17 to the bottom portion 16. Therefore, the bottom portion 16 is cooled effectively.

[0121] At least a portion of the communication hole 28 is located on the other axial side of the other axial end of the outer diameter side cylindrical portion 19 and is exposed from the cylinder 9 when not braking. This increases the amount of air passing through the communication hole 28 and directed to the bottom portion 16. Furthermore, because the communication hole 28 is provided in the inner diameter side cylindrical portion 20, cooling air introduced from the outside of the piston 3 into the piston internal space 25 through the communication hole 28 can be discharged to the outside of the piston 3 through the communication hole 28, as shown by the arrows in FIG. 3 . In other words, the cooling air can be circulated using the communication hole 28, thereby effectively dissipating heat accumulated in the piston 3. Furthermore, as shown by the dashed arrows in FIG. 3 , the cooling air introduced into the piston internal space 25 also passes between the columnar ribs 17.

[0122] Central axis O of the communication hole 28 28 is inclined in a direction toward one axial side as it moves radially inward with respect to the piston central axis O3, and the central axis O 28 Since the extension of the line passes through the other axial side surface of the bottom portion 16, the running wind that passes through the communication hole 28 is efficiently guided to the bottom portion 16.

[0123] Furthermore, the communication hole 28 is provided in the vicinity of the connection part of the inner diameter side cylindrical portion 20 with the other longitudinal end part of the columnar rib 17, i.e., in the part of the inner diameter side cylindrical portion 20 that is sufficiently strong due to the connection of the other longitudinal end part of the columnar rib 17. Therefore, a decrease in the strength of the inner diameter side cylindrical portion 20 caused by the provision of the communication hole 28 is efficiently suppressed.

[0124] In the piston 3 of this example, the heat shield plate 29 is provided on the radially inner side of the inner diameter side cylindrical portion 20, so that the amount of heat transferred from the pads 4a, 4b to the bottom portion 16 can be reduced.

[0125] In addition, the heat shield 29 is positioned in the piston internal space 25 so that it cannot fall off by engaging the engaging protrusions 27 with the engaging holes 32 provided in each of the multiple engaging pieces 31, thereby reducing the cost of the heat shield 29 and improving the workability of installing the heat shield 29.

[0126] [Example 2] A second example of the embodiment of the present disclosure will be described with reference to FIG.

[0127] In this example, only the structure of the piston 3a is different from the structure of the piston 3 in the first example.

[0128] In this example, the piston 3a is configured such that the outer diameter side cylindrical portion 19a and the inner diameter side cylindrical portion 20a that constitute the cylindrical wall portion 15a are separate bodies, and the inner diameter side cylindrical portion 20a and the multiple columnar ribs 17a are configured integrally.

[0129] In this example, piston body 18a, which includes cylindrical wall portion 15a, bottom portion 16a, and multiple columnar ribs 17a, is not composed of a single component but of two components. Specifically, piston body 18a is composed of an outer member 35 and an inner member 36.

[0130] The outer member 35 has a cup shape and is composed of an outer diameter side cylindrical portion 19a and a disk-shaped outer bottom portion 37a that closes an end opening on one axial side of the outer diameter side cylindrical portion 19a.

[0131] The inner member 36 is composed of an inner diameter side cylindrical portion 20a, a disk-shaped inner bottom portion 37b that closes the end opening on one axial side of the inner diameter side cylindrical portion 20a, and a plurality of columnar ribs 17a.

[0132] The piston body 18a in this example is formed by press-fitting the inner member 36 into the outer member 35. Specifically, one axial end of the inner diameter side cylindrical portion 20a constituting the inner member 36 is press-fitted into one axial end of the outer diameter side cylindrical portion 19a constituting the outer member 35, and one axial side of the inner bottom portion 37b constituting the inner member 36 is closely overlapped with the other axial side of the outer bottom portion 37a constituting the outer member 35 to form the piston body 18a. Therefore, the bottom portion 16a is formed by the outer bottom portion 37a and the inner bottom portion 37b, and when the inner member 36 is internally fitted into the outer member 35, the annular gap 21 is formed between the inner circumferential surface of the outer diameter side cylindrical portion 19a and the inner circumferential surface of the inner diameter side cylindrical portion 20a.

[0133] In this example, the radial thickness t of the columnar rib 17a is substantially constant over the entire length and is greater than the radial thicknesses of the outer diameter side cylindrical portion 19a and the inner diameter side cylindrical portion 20a.

[0134] In this example, the piston body 18a is not composed of a single component, but of two components: an outer member 35 and an inner member 36. This allows the piston body 18a to be manufactured by separately manufacturing the outer member 35 and the inner member 36 and then assembling them together, thereby improving the flexibility of the manufacturing method. Specifically, the outer member 35 and the inner member 36 can be manufactured by machining, injection molding, or the like. This reduces the manufacturing time and costs.

[0135] The other configurations and effects are the same as those of the first example. [Explanation of symbols]

[0136] 1 Disc brake device 2 calipers 3, 3a piston 4a, 4b pads 5 rotors 6 Inner Body 7 Outer Body 8. Bridge 9 cylinders 10 Connection 11 Seal groove 12 Piston seal 13 Lining 14 Back plate 15, 15a Cylindrical wall 16, 16a bottom 17, 17a Columnar rib 18, 18a Piston body 19, 19a Outer cylinder part 20, 20a Inner cylinder part 21 Annular gap 22 Seal sliding contact part 23 Tapered surface 24 Pad contact part 25 Piston internal space 26a 1st reinforcement part 26b Second reinforcement part 27 Engagement protrusion 28 Communication hole 29 Heat shield 30 Lid 31 Engagement piece 32 Engagement hole 33 Cutout 34 small hole 35 Outer member 36 Inner member 37a outer bottom 37b Inner bottom 100 Disc brake device 101 Caliper 102 Piston 103 Rotor 104 Inner Body 105 Outer Body 106 cylinders 107 Piston seal 108 Cylindrical wall 109 Bottom 110a, 110b pads 111 Outer cylinder part 112 Inner cylinder part 113 Annular gap

Claims

1. A piston for a disc brake device that is fitted into a cylinder of a caliper that constitutes a disc brake device, The entire cylinder is configured in a cylindrical shape with a bottom, and includes a cylindrical wall portion having a substantially cylindrical shape, a bottom portion that closes one axial end of the cylindrical wall portion and is located at the back side of the cylinder, and a plurality of columnar ribs that are located radially inside the cylindrical wall portion, the cylindrical wall portion has an outer diameter side cylindrical portion having a seal sliding contact portion on its outer peripheral surface, an inner diameter side cylindrical portion arranged radially inside the outer diameter side cylindrical portion and having a pad abutment portion at an end portion on the other axial side that protrudes in the axial direction further than an end portion on the other axial side of the outer diameter side cylindrical portion, and an annular gap provided between the inner peripheral surface of the outer diameter side cylindrical portion and the outer peripheral surface of the inner diameter side cylindrical portion, The plurality of columnar ribs are arranged at an angle with respect to the piston central axis, and each end on one side in the length direction is connected to a side surface on the other side in the axial direction of the bottom portion, and each end on the other side in the length direction is connected to the inner peripheral surface of the inner diameter side cylindrical portion. Piston for disc brake device.

2. 2. The piston for a disc brake device according to claim 1, wherein each of the plurality of columnar ribs has a longitudinal end connected to an axial end of the inner circumferential surface of the inner diameter side cylindrical portion.

3. 2. The piston for a disc brake device according to claim 1, wherein the plurality of columnar ribs are arranged radially around the piston center axis.

4. 2. The piston for a disc brake device according to claim 1, wherein one end of each of the plurality of columnar ribs in the longitudinal direction is connected to a radially intermediate portion of a side surface on the other axial side of the bottom portion.

5. 2. The piston for a disc brake device according to claim 1, wherein the plurality of columnar ribs are arranged at equal intervals in the circumferential direction.

6. 2. The piston for a disc brake device according to claim 1, wherein the outer diameter side cylindrical portion, the inner diameter side cylindrical portion, and the plurality of columnar ribs are integrally formed.

7. 2. The piston for a disc brake device according to claim 1, wherein the outer diameter side cylindrical portion and the inner diameter side cylindrical portion are configured separately, and the inner diameter side cylindrical portion and the plurality of columnar ribs are configured integrally.

8. 2. The piston for a disc brake device according to claim 1, wherein the inner diameter side cylindrical portion has a communication hole penetrating therethrough in the radial direction.

9. 9. The piston for a disc brake device according to claim 8, wherein the communication hole is provided in a portion of the inner diameter side cylindrical portion that coincides in phase with the columnar rib in the circumferential direction.

10. 9. The piston for a disc brake device according to claim 8, wherein the communication hole is provided in the inner diameter side cylindrical portion near a connection portion where the columnar rib is connected to the other end portion in the longitudinal direction.

11. 11. The piston for a disc brake device according to claim 10, wherein the communication hole is provided in a portion adjacent to one axial side of the connection portion.

12. 9. The piston for a disc brake device according to claim 8, wherein at least a portion of the communication hole is located on the other axial side of the other axial end of the outer diameter side cylindrical portion.

13. 9. The piston for a disc brake device according to claim 8, wherein the central axis of the communication hole is inclined with respect to the central axis of the piston in a direction that approaches one axial side as it moves radially inward.

14. A heat shield plate is provided on the radially inner side of the inner diameter side cylindrical portion, The heat shield plate covers the other axial side surface of the bottom portion while contacting the plurality of columnar ribs. The piston for a disc brake device according to claim 1.

15. 15. The piston for a disc brake device according to claim 14, wherein the heat shield plate is engaged with the plurality of columnar ribs.

16. Each of the plurality of columnar ribs has an engagement protrusion at a portion in the length direction thereof, The heat shield plate has an engagement hole, The engagement projection is engaged with the engagement hole. The piston for a disc brake device according to claim 15.

17. A caliper having a cylinder and a piston fitted in the cylinder, A disc brake device, wherein the piston is the piston for a disc brake device according to any one of claims 1 to 16.

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