Disc brake

Abstract

A disc brake includes: a cylinder bore (35) into which a piston is fitted; a sealing groove (55) which is provided as an annular groove on the cylinder bore (35); and a square-section sealing member (22) that fits into the sealing groove (55) and seals the piston and the cylinder bore (35). The sealing groove (55) has a bottom portion (103), a side portion (104), and a chamfered portion (105). The chamfered portion (105) is formed to enlarge the opening (108) of the sealing groove (55) in the axial direction of the cylinder bore (35) and has two radii of curvature (R1, R2).

Description

[0001] This application is a divisional application of the invention patent application filed on May 15, 2019, with application number 201980035866.7 and invention title "Disc Brake". Technical Field

[0002] This invention relates to a disc brake.

[0003] This application claims priority based on Japanese Patent Application No. 2018-102315, filed in Japan on May 29, 2018, the contents of which are incorporated herein by reference. Background Technology

[0004] A disc brake is provided in which brake fluid is introduced between a cylinder bore and a piston slidably fitted into the cylinder bore, causing the piston to advance and pressing the brake pads against the disc rotor (see, for example, patent literature). ).

[0005] Patent Document 1: Japanese Patent Application Publication No. 2010-175041

[0006] Patent Document 2: Japanese Patent Application Publication No. 2011-214623

[0007] Patent Document 3: US Patent No. 6244393 Summary of the Invention

[0008] In disc brakes, a phenomenon known as drag can occur, where the brake pads continue to contact the disc after the brakes have been released. It is desirable to suppress this drag.

[0009] The present invention provides a disc brake capable of suppressing drag.

[0010] According to one aspect of the invention, a disc brake has: a bottom portion that inclines a sealing groove, which is an annular groove recessed from the inner circumferential surface and located in the cylinder bore, toward an increasing diameter direction toward the opening side of the cylinder bore; a side portion that extends from the larger diameter side of the bottom portion toward the opening side of the sealing groove; and a chamfer portion disposed between the side portion and the inner circumferential surface of the cylinder bore, thereby increasing the opening of the sealing groove in the axial direction of the cylinder bore. The chamfer portion has two radii of curvature.

[0011] Invention Effects

[0012] The disc brake described above can suppress drag. Attached Figure Description

[0013] Figure 1 This is a top view showing the disc brake according to the first embodiment of the present invention;

[0014] Figure 2This is a side sectional view showing the disc brake according to the first embodiment of the present invention;

[0015] Figure 3A This is a partial cross-sectional view showing the sealing component of the disc brake according to the first embodiment of the present invention;

[0016] Figure 3B This is a partial cross-sectional view showing the state of the sealing groove of the disc brake according to the first embodiment of the present invention before assembly;

[0017] Figure 4A This is a partial cross-sectional view of the sealing groove in Comparative Example 1 of a disc brake;

[0018] Figure 4B This is a partial cross-sectional view of the sealing groove of Comparative Example 2 of the disc brake;

[0019] Figure 5 This is a characteristic graph showing the piston return amount relative to the brake hydraulic pressure in the first and second embodiments of the present invention and Comparative Examples 1 and 2.

[0020] Figure 6 This is a partial cross-sectional view showing the sealing groove of the disc brake according to the second embodiment of the present invention. Detailed Implementation

[0021] [First Implementation Method]

[0022] The following is for reference Figures 1 to 5 The first implementation method is described below.

[0023] Figure 1 and Figure 2 This illustrates a disc brake 10 according to the first embodiment. This disc brake 10 applies braking force to vehicles such as automobiles. Specifically, the disc brake 10 is used for braking four-wheeled vehicles. The disc brake 10 brakes the vehicle by stopping the rotation of a disc rotor 11, which rotates together with the wheels (not shown in the diagram). Hereinafter, the direction of the central axis of the disc rotor 11 will be referred to as the disc axis direction, the radial direction of the disc rotor 11 will be referred to as the disc diameter direction, and the circumferential direction (rotation direction) of the disc will be referred to as the disc circumferential direction.

[0024] The disc brake 10 includes: a bracket 12, Figure 2 The pair of brake pads 13 and 14, caliper 15, and shown are shown. Figure 1 A pair of dust covers 16 are shown. A bracket 12 is positioned across the outer periphery of the disc rotor 11 and is fixed to the non-rotating part of the vehicle. A pair of brake pads 13 and 14 are positioned on both sides, sandwiching the disc rotor 11, and are supported on the bracket 12 in a manner that allows them to move in the disc shaft direction. A caliper 15 is supported on the bracket 12 in a manner that allows it to move in the disc shaft direction. The caliper 15 clamps the pair of brake pads 13 and 14 and presses them against both sides of the disc rotor 11.

[0025] The caliper 15 includes: a caliper body 20, a piston 21, a sealing component 22, a dust cover component 23, and Figure 1 The pair of sliding pins 24 shown.

[0026] The caliper body 20 is formed by machining a metal raw material that is integrally cast. The caliper body 20 has: a cylinder 26 disposed on one side of the disc rotor 11 in the disc axis direction; a bridge portion 27 extending from the outer side of the cylinder 26 in the disc diameter direction across the outer periphery of the disc rotor 11; and a claw portion 28 extending from the side of the bridge portion 27 opposite to the cylinder 26 in the disc diameter direction and disposed on the other side of the disc rotor 11 in the disc axis direction. Figure 1 The pair of wrists 29 shown extend from the cylinder 26 to both sides in the circumferential direction. The caliper body 20 is movably supported on the bracket 12 on the sliding pins 24 mounted on the pair of wrists 29. A pair of dust covers 16 cover the sliding pins 24.

[0027] like Figure 2 As shown, a cylinder bore 35 is formed on cylinder 26, with one end opening towards the claw portion 28 and recessed towards the side opposite to the disc rotor 11 in the direction of the disc shaft. By forming the cylinder bore 35 opening towards the claw portion 28, cylinder 26 has a cylinder bottom 39 on the side opposite to the claw portion 28, including the inner bottom 38 of the cylinder bore 35, and a cylinder body portion 42 extending from the cylinder bottom 39 towards the claw portion 28, including the inner wall portion 41 of the cylinder bore 35. The cylinder bore 35 has an opening 43 on the side of the cylinder body portion 42 opposite to the cylinder bottom 39. The cylinder bottom 39 side of the cylinder bore 35 is referred to as the bore bottom side, and the opening 43 side of the cylinder bore 35 is referred to as the bore opening side.

[0028] The piston 21 is fitted into the cylinder bore 35 in a manner that allows it to slide along the axis of the cylinder. The inner wall 41 of the cylinder bore 35 has a guide inner circumferential surface 51 (inner circumferential surface) that guides the movement of the piston 21 and has a constant inner diameter along its entire length. The central axis of this guide inner circumferential surface 51 is the central axis of the cylinder bore 35. This central axis is referred to as the bore axis. In addition, the direction orthogonal to this central axis is referred to as the bore diameter direction, and the circumferential direction centered on this central axis is referred to as the bore circumferential direction.

[0029] The inner wall portion 41 of the cylinder bore 35 has an annular large-diameter groove 52 that is recessed outward in the bore diameter direction than the inner circumferential surface 51 of the guide. The large-diameter groove 52 is annular with the bore axis as the center, and the bottom diameter of the groove is larger than that of the inner circumferential surface 51 of the guide.

[0030] The inner wall portion 41 of the cylinder bore 35 has an annular sealing groove 55 located at the midpoint of the guide inner circumferential surface 51 on the bore opening side, which is recessed further outward in the bore diameter direction than the guide inner circumferential surface 51. The sealing groove 55 is an annular groove centered on the bore axis, recessed from the guide inner circumferential surface 51 within the inner wall portion 41 of the cylinder bore 35. The bottom diameter of the sealing groove 55 is larger than the diameter of the guide inner circumferential surface 51.

[0031] On the inner wall portion 41 of the cylinder bore 35, a circular dust cover fitting groove 58 is formed on the side closer to the bore opening than the sealing groove 55, and is recessed outward in the bore diameter direction than the inner circumferential surface 51 of the guide. The dust cover fitting groove 58 is annular with the bore axis as the center, and its bottom diameter is larger than that of the inner circumferential surface 51 of the guide.

[0032] On the inner wall 41 of the cylinder bore 35, a dust cover mounting hole 59 is formed closer to the bore opening than the dust cover fitting groove 58. This dust cover mounting hole 59 is conical, centered on the bore axis, and its diameter increases with distance from the dust cover fitting groove 58. The end of the dust cover mounting hole 59 located opposite to the cylinder bottom 39 forms the opening 43 of the cylinder bore 35. The large-diameter groove 52 and the inner bottom 38 connected thereto are cast during the casting of the raw material of the caliper body 20. The guide inner circumferential surface 51, the sealing groove 55, the dust cover fitting groove 58, and the dust cover mounting hole 59 are formed by machining the raw material of the caliper body 20.

[0033] A piping hole 68 is formed at the bottom 39 of the cylinder, opening into the cylinder bore 35 and extending along the bore axis. The piping hole 68 is formed by machining the material of the caliper body 20. A brake hose (not shown) is connected to the piping hole 68.

[0034] The piston 21 has a circular piston bottom 71 and a cylindrical piston body portion 72. The piston 21 is formed as a bottomed cylindrical part with an opening at the end of the piston body portion 72 opposite to the piston bottom 71. In the piston body portion 72, on its axial side opposite to the piston bottom 71, an annular fitting groove 75 is formed that is recessed radially inward than the outer diameter surface 74 formed by the cylindrical surface. The piston 21 is housed in the cylinder bore 35 such that the piston bottom 71 is located at the bottom side of the bore, and in this state, the front end of the claw portion 28 protrudes further into the claw portion 28 side than the cylinder bore 35. The fitting groove 75 is formed on the piston 21 at the front end side that protrudes further than the cylinder bore 35 as described above.

[0035] The sealing member 22 is made of an elastic material, specifically rubber. The sealing member 22 has an interference fit into a sealing groove 55 of the cylinder bore 35. The piston 21 has an interference fit into the inner circumferential side of the sealing member 22. The sealing member 22 undergoes radial elastic deformation, thus tightly fitting against the piston 21 and the sealing groove 55, thereby sealing the cylinder bore 35 of the cylinder 26 and the piston 21. Furthermore, the sealing member 22 supports the outer diameter surface 74 of the piston 21 on the guiding inner circumferential surface 51 of the cylinder bore 35 in a manner that allows movement in the axial direction of the bore. The sealing member 22 forms a hydraulic chamber 69 through the cylinder bore 35 and the piston 21. Brake fluid is supplied and discharged to this hydraulic chamber 69 via a brake hose connected to a piping port 68.

[0036] The dust cover component 23 is a retractable, meandering cylindrical body. One end of the dust cover component 23 is fitted into the dust cover fitting groove 58 of the cylinder 26, and the other end is fitted into the fitting groove 75 of the piston 21. The dust cover component 23 covers the portion of the outer diameter surface 74 on the piston bottom 71 side that protrudes from the cylinder bore 35 relative to the fitting groove 75 of the piston 21. The dust cover component 23 extends and retracts as the piston 21 moves relative to the cylinder bore 35.

[0037] Regarding the disc brake 10, when the brake pedal (not shown) is operated, brake fluid is introduced into the hydraulic chamber 69 via a brake hose (not shown) connected to the hose port 68. This causes the brake fluid to act on the piston bottom 71 of the piston 21 in a direction away from the cylinder bottom 39. As a result, the piston 21 advances relative to the cylinder bore 35 toward the disc rotor 11, pressing the brake pad 13 disposed between the piston 21 and the disc rotor 11 toward the disc rotor 11. Consequently, the brake pad 13 moves and contacts the disc rotor 11. As the piston 21 advances toward the disc rotor 11 relative to the cylinder bore 35, the contact portion of the sealing member 22 housed in the sealing groove 55 elastically deforms the inner circumference of the sealing member 22 due to friction, causing it to move integrally.

[0038] Furthermore, utilizing the reaction force of pressing the brake pads 13 against the disc rotor 11, the caliper body 20 slides relative to the bracket 12 within a pair of sliding pins 24, and the claws 28 press the brake pads 14, positioned between the claws 28 and the disc rotor 11, toward the disc rotor 11. Thus, the brake pads 14 come into contact with the disc rotor 11. In this way, the caliper 15, through the operation of the piston 21, clamps a pair of brake pads 13 and 14 from both sides and presses them against both sides of the disc rotor 11. As a result, the caliper 15 applies frictional resistance to the disc rotor 11, generating braking force. The piston 21 uses brake hydraulic pressure to press the brake pads 13 and 14 on both sides onto the disc rotor 11.

[0039] If the brake pedal (not shown) is released from this state, the hydraulic pressure in the hydraulic chamber 69 decreases, and the force exerted by the piston 21 on the sealing member 22, which has undergone elastic deformation as described above, decreases. As a result, the sealing member 22 returns to its original state from the deformed state using its own elasticity. At this time, a so-called return process occurs, causing the piston 21 to retract towards the bottom of the bore through friction, creating a gap between the piston 21 and the brake pad 13. Consequently, due to the vibration of the disc rotor 11, the brake pads 13, 14, and the claw portion 28 move away from the disc rotor 11 in a direction away from the disc shaft.

[0040] like Figure 3A As shown, if the sealing member 22, made of elastic material, is formed into a circular shape in its natural state before being fitted into the sealing groove 55, it has: an outer peripheral surface 91 formed by cylindrical surfaces, an inner peripheral surface 92 formed by cylindrical surfaces with a smaller diameter than the outer peripheral surface 91, a flat end surface 93 orthogonal to the outer peripheral surface 91 and the inner peripheral surface 92 and connecting their axial one-end edges to each other, and a flat end surface 94 orthogonal to the outer peripheral surface 91 and the inner peripheral surface 92 and connecting their axial other-end edges to each other. In other words, if the sealing member 22 is formed into a circular shape in its natural state before being fitted into the sealing groove 55, when a cross-section is formed on a surface including the central axis of the sealing member 22, its cross-sectional shape forms a rectangle with a long side parallel to the central axis.

[0041] The sealing groove 55 is an annular shape centered on the hole shaft, extending from the bottom side of the hole in the direction of the hole shaft ( Figure 3B The BBS shown has, in sequence, the following: a bottom chamfered portion 101, a bottom side portion 102, a groove bottom portion 103 (bottom portion), a hole opening side portion 104 (side portion), a hole opening side chamfered portion 105 (chamfered portion), an axially extending portion 106, and a radially extending portion 107. The small-diameter side of the sealing groove 55 becomes a groove opening 108 facing the hole shaft opening.

[0042] The chamfered portion 101 at the bottom of the hole extends outward from the inner guide circumferential surface 51 of the cylindrical surface in the direction of the hole diameter, and is located further outward from the direction of the hole diameter towards the hole opening side. Figure 3B The BOS-shaped tapered surface is inclined and centered on the hole axis. The bottom chamfer 101 of the hole is an annular shape with a constant diameter on both the small and large diameter sides along the circumference of the hole.

[0043] The bottom side surface 102 is an annular plane centered on the hole axis, extending outward from the end edge of the large diameter side of the bottom chamfered portion 101 of the hole axis, perpendicular to the hole axis. The bottom side surface 102 is an annular shape with a constant diameter on both the small diameter side and the large diameter side along the circumference of the hole.

[0044] The groove bottom surface 103 has, in sequence from the bottom side of the hole, a first conical surface 111, a second conical surface 112, a concave surface 113, a third conical surface 114, and a fourth conical surface 115.

[0045] The first tapered section 111 extends from the end edge of the large-diameter side of the bottom side section 102 toward the hole opening side, and is inclined in a manner that the closer it is to the hole opening side, the more outward it is located in the hole diameter direction, and is centered on the hole axis. The taper of the first tapered section 111 is smaller than that of the chamfered section 101 on the bottom side of the hole. The first tapered section 111 is an annular shape with a constant diameter on both the small-diameter side and the large-diameter side along the entire circumference of the hole.

[0046] The second conical surface 112 extends from the end edge of the first conical surface 111 on the hole opening side toward the hole opening side and is inclined in such a way that it is located further outward in the hole diameter direction as it gets closer to the hole opening side, and is centered on the hole axis. The taper of the second conical surface 112 is smaller than that of the first conical surface 111. The second conical surface 112 is an annular shape with a constant diameter on both the small diameter side and the large diameter side along the entire circumference of the hole.

[0047] The concave portion 113 is a curved surface that extends from the end edge of the second conical portion 112 on the hole opening side toward the hole opening side, and is inclined such that it is located further outward in the hole diameter direction as it approaches the hole opening side, and then inclined further inward in the hole diameter direction as it approaches the hole opening side. The concave portion 113 is annular in shape with the hole axis as the center.

[0048] The concave portion 113 forms a cross-section containing the bore axis with a central arc shape inside the bore diameter direction. The concave portion 113 forms a shape whose cross-section is constant throughout the circumference of the bore.

[0049] The third conical surface 114 extends from the end edge of the concave surface 113 towards the opening side and is inclined towards the opening side, with the diameter of the hole being further outward. It is a conical surface centered on the hole axis. The taper of the third conical surface 114 is equal to that of the second conical surface 112, and it is positioned on the same conical surface as the second conical surface 112. The third conical surface 114 is an annular shape with a constant small diameter and a constant large diameter along the entire circumferential direction of the hole. Relative to the second conical surface 112 and the third conical surface 114 positioned on the same conical surface, the concave surface 113 is recessed outward in the diameter direction, forming an annular bottom groove 118 in the groove bottom surface 103 of the sealing groove 55.

[0050] The fourth conical surface 115 is a conical surface centered on the hole axis that extends from the end edge of the third conical surface 114 on the hole opening side and is inclined in such a way that it is located further inside the hole diameter direction as it gets closer to the hole opening side. The fourth conical surface 115 is an annular shape with a constant diameter on both the major and minor diameter sides along the hole circumference.

[0051] The bottom surface 103 of the groove, which has a first conical surface 111, a second conical surface 112, a concave surface 113, a third conical surface 114, and a fourth conical surface 115, is inclined in the direction of increasing the diameter towards the opening side of the hole. The side of the first conical surface 111 in the direction of the hole axis is the small diameter side, and the side of the fourth conical surface 115 is the large diameter side.

[0052] The orifice opening side surface 104 is an annular plane centered on the orifice axis, extending from the end edge of the fourth conical surface 115 on the orifice opening side, perpendicular to the orifice axis and extending inward in the orifice diameter direction. In other words, the orifice opening side surface 104 extends from the large-diameter side of the groove bottom surface 103 towards the groove opening 108 side of the sealing groove 55. The orifice opening side surface 104 is an annular shape with a constant diameter on both the large-diameter and small-diameter sides along the entire circumference of the orifice.

[0053] A chamfered portion 105 on the opening side is provided between the opening side surface portion 104 and the portion of the guide inner circumferential surface 51 that is closer to the opening side than the sealing groove 55. The opening side chamfered portion 105 is a curved surface that extends inward in the bore diameter direction from the small diameter side edge of the opening side surface portion 104, and is inclined such that it is closer to the opening side as it moves inward in the bore diameter direction. The opening side chamfered portion 105 is annular with the bore axis as its center. In other words, the opening side chamfered portion 105 is formed from the small diameter side edge of the opening side surface portion 104 in a manner that expands the groove opening 108 of the sealing groove 55 towards the bore axis. The opening side chamfered portion 105 is annular with a constant diameter on both the large and small diameter sides along the entire circumference of the bore. The width of the opening side chamfered portion 105 in the bore diameter direction is smaller than that of the opening side surface portion 104.

[0054] The chamfered portion 105 on the orifice opening side is a curved surface with two radii of curvature. That is, the chamfered portion 105 on the orifice opening side has: a first radius of curvature portion 121, which is formed by a curved surface formed on the groove bottom surface 103 side of the sealing groove 55; and a second radius of curvature portion 122, which is formed by a curved surface formed on the guide inner circumferential surface 51 side of the cylinder bore 35 compared to the first radius of curvature portion 121.

[0055] The first radius of curvature 121 is a curved surface that extends inward from the small-diameter end edge of the orifice side surface 104 in the orifice diameter direction and is inclined in such a way that it is closer to the orifice opening side the closer it is to the orifice diameter direction. The first radius of curvature 121 forms an annular shape centered on the orifice axis. The cross-section of the surface of the first radius of curvature 121 containing the orifice axis is formed in the cylinder 26 in an arc shape with a constant radius of curvature r1 at the center of the solid part of the first radius of curvature 121. In the cross-section of the surface of the first radius of curvature 121 containing the orifice axis, the center of the radius of curvature r1 is located closer to the orifice diameter direction than the bisecting line of the angle formed by the orifice opening side surface 104 and the axially extending surface 106. In other words, the first radius of curvature 121 is inclined at an angle closer to the orifice diameter direction than the orifice axis direction. The first radius of curvature 121 forms a shape with a cross-section that is constant throughout the circumference of the orifice.

[0056] The first curvature radius portion 121 is an annular shape with a constant diameter on both the major and minor diameter sides along the circumference of the hole.

[0057] The second radius of curvature 122 is a curved surface that extends inward from the small-diameter side of the first radius of curvature 121 towards the bore diameter direction and is inclined in such a way that it is located closer to the bore opening side as it moves towards the bore diameter direction. The second radius of curvature 122 forms an annular shape centered on the bore axis. The cross-section of the second radius of curvature 122, including the bore axis, is an arc shape with a constant radius of curvature r2 at the center on the solid side of the cylinder 26. The second radius of curvature 122 forms a shape whose cross-section is constant throughout the circumference of the bore. The second radius of curvature 122 is an annular shape with a constant diameter on both the large-diameter and small-diameter sides throughout the circumference of the bore. The radius of curvature r2 of the second radius of curvature 122 is smaller than the radius of curvature r1 of the first radius of curvature 121. In other words, the radius of curvature of the second radius of curvature 122 is smaller than that of the first radius of curvature 121. In addition, the width of the second radius of curvature portion 122 in the aperture direction is smaller than that of the first radius of curvature portion 121.

[0058] The axially extending surface 106 is a cylindrical surface centered on the hole axis, extending from the end edge of the small-diameter side of the second radius of curvature portion 122 of the chamfered portion 105 on the hole opening side towards the hole opening side. The inner diameter of the axially extending surface 106 is a constant diameter throughout its entire length and is larger than the inner diameter of the guide inner circumferential surface 51.

[0059] The radially extending facet 107 is an annular plane centered on the bore axis, extending inward from the end edge of the axially extending facet 106 on the bore opening side, perpendicular to the bore axis. The radially extending facet 107 is an annular shape with a constant diameter on both the small and large diameter sides along the entire circumference of the bore. The small diameter side of the radially extending facet 107 is connected to the portion of the guide inner circumferential surface 51 that is closer to the bore opening side than the sealing groove 55.

[0060] The axially extending portion 106 and the radially extending portion 107 are configured to form a stepped portion 125 that is recessed outward in the bore direction at the end of the sealing groove 55 on the bore opening side and the groove opening 108 side. In other words, the sealing groove 55 has a stepped portion 125 formed in a manner that is recessed outward in the bore direction at the end of its bore opening side and the groove opening 108 side.

[0061] The disc brakes described in Patent Documents 1-3 introduce brake hydraulic pressure between the cylinder bore and a piston slidably mounted on the cylinder bore, causing the piston to advance and pressing the brake pads against the disc rotor. In such disc brakes, a sealing member is provided to seal the gap between the cylinder bore and the piston. This sealing member returns the piston to its original position to the bottom of the cylinder when the brake hydraulic pressure is released.

[0062] Additionally, there is a desire to improve fuel efficiency by suppressing so-called "drag," where the brake pads continue to contact the disc after brake release. This drag is particularly effective when brake fluid pressure is high by increasing the return amount of the piston upon hydraulic release, based on the sealing components. However, increasing the return amount of the piston upon hydraulic release, based on the sealing components, increases the resistance of the sealing components relative to piston movement when brake fluid pressure is low, leading to reduced piston responsiveness and a deterioration in pedal feel.

[0063] In this regard, the disc brake 10 of the first embodiment includes: a groove bottom portion 103 of the sealing groove 55 inclined in the direction of increasing diameter toward the hole opening side; a hole opening side portion 104 extending from the large diameter side of the groove bottom portion 103 toward the groove opening 108 side of the sealing groove 55; and a hole opening side chamfered portion 105 disposed between the hole opening side portion 104 and the inner peripheral surface 51 of the guide member of the cylinder bore 35, which enlarges the groove opening 108 in the hole axial direction. The hole opening side chamfered portion 105 has two radii of curvature r1 and r2.

[0064] Specifically, the chamfered portion 105 on the opening side has a first radius of curvature 121 with a radius of curvature r1 on the bottom surface 103 side and a second radius of curvature 122 formed on the inner guiding surface 51 side, which has a radius of curvature r2 smaller than that of the first radius of curvature 121.

[0065] Therefore, regarding the sealing member 22, which moves with the piston 21 along with the piston 21 on the inner circumferential surface 92 side as the piston 21 advances, when the braking hydraulic pressure is low, the end face 93 on the orifice opening side deforms with a large radius of curvature r1, mimicking the first radius of curvature 121, and the fulcrum of deformation gradually changes while smoothly increasing under a low spring constant. On the other hand, when the braking hydraulic pressure is high, the end face 93 deforms with a small radius of curvature r2, mimicking the second radius of curvature 122 after the first radius of curvature 121, thereby gradually changing the fulcrum of deformation while smoothly increasing under a high spring constant.

[0066] Therefore, by not reducing the responsiveness of piston 21 when the brake hydraulic pressure is low, and increasing the return amount of piston 21 when the hydraulic pressure is released based on seal member 22 when the brake hydraulic pressure is high, the drag effect can be achieved. In addition, since the chamfered portion 105 on the orifice opening side is a curved surface, the load on seal member 22 when it deforms can be reduced, and the durability of seal member 22 can be improved.

[0067] Furthermore, a first radius of curvature 121, with a radius of curvature r1 larger than that of the second radius of curvature 122, is provided on the side closer to the bottom portion 103 than the second radius of curvature 122. In a cross-section including the bore shaft, the center of this first radius of curvature 121 is positioned inside the bore diameter direction relative to the bisector of the angle formed by the bore opening side portion 104 and the axially extending portion 106. Therefore, the outer portion of the bore opening side chamfer 105 in the bore diameter direction can be positioned closer to the bottom of the bore. This reduces the deflection space of the sealing member 22 when the brake hydraulic pressure is low, allowing the sealing member 22 to be compressed using the brake hydraulic pressure, thereby assisting in its return to its original position.

[0068] Furthermore, by properly positioning the boundary between the first radius of curvature portion 121, which serves as the deformation fulcrum of the sealing member 22, and the side portion 104 of the hole opening, the stress distribution relative to the restoration of the sealing member 22 to its original state can be made more uniform.

[0069] Furthermore, since a stepped portion 125 is provided on the hole opening side and the groove opening 108 side of the sealing groove 55, when the inner circumferential surface 92 side of the sealing member 22 moves toward the hole opening side together with the piston 21, it is allowed to cross the second radius of curvature 122 and deform toward the gap between the stepped portion 125 and the piston 21, thus enabling a large deformation.

[0070] Here, regarding the disc brake 10 of the first embodiment, as a comparative example 1, such as... Figure 4A The sealing groove 55 shown has a disc brake with a chamfered portion 105A on the hole opening side formed by a conical surface, which is the same as the conventional structure, and as a comparative example 2, such as Figure 4BThe disc brake shown, with a sealing groove 55 and a chamfered portion 105B on the opening side with a constant radius of curvature, experimentally determined the return amount (hereinafter referred to as piston return amount) of the piston 21 upon hydraulic release relative to the brake hydraulic pressure. The results are as follows... Figure 5 As shown. In Figure 5 In the chart, the horizontal axis represents the brake hydraulic pressure P, the vertical axis represents the piston return amount L, and the broken line represents the measurement results of the first embodiment and comparative examples 1 and 2.

[0071] like Figure 5 As shown by the solid line X1, the disc brake 10 of the first embodiment is capable of engaging with... Figure 5 Similar to Comparative Example 1, which shows the conventional structure indicated by the dashed line X2, the piston return amount when the brake hydraulic pressure is low is kept low, while the piston return amount when the brake hydraulic pressure is high is increased compared to Comparative Example 1. In other words, the disc brake 10 of the first embodiment can increase the rate of increase in piston return amount per unit rise in brake hydraulic pressure compared to Comparative Example 1 of the conventional structure.

[0072] Here, in Figure 5 In Comparative Example 2, shown by dashed line X3, compared to Comparative Example 1 with the existing structure, the piston return amount when the brake hydraulic pressure is high can be increased, thereby achieving the effect of suppressing drag. However, the piston return amount when the brake hydraulic pressure is low also increases, resulting in increased resistance of the sealing component relative to the piston's movement and reduced piston responsiveness.

[0073] As described above, the disc brake 10 of the first embodiment can achieve the effect of suppressing drag by increasing the return amount of the piston 21 based on the sealing member 22 when the brake hydraulic pressure is high without reducing the responsiveness of the piston 21 when the brake hydraulic pressure is low.

[0074] [Second Implementation Method]

[0075] Next, mainly based on Figure 5 , Figure 6 The second embodiment will be described focusing on the parts that differ from the first embodiment. Furthermore, parts common to the first embodiment will be referred to using the same names and symbols.

[0076] like Figure 6 As shown, in the second embodiment, the sealing groove 55 has the same features as in the first embodiment: a bottom chamfered portion 101, a bottom side surface portion 102, a hole opening side surface portion 104, a hole opening side chamfered portion 105, an axially extending portion 106, and a radially extending portion 107. Between the bottom side surface portion 102 and the hole opening side surface portion 104, there is a groove bottom surface portion 203 (bottom surface portion) that is different from the groove bottom surface portion 103 in the first embodiment.

[0077] The bottom surface 203 has the same first conical surface 111, concave surface 113 and fourth conical surface 115 as in the first embodiment. Between the first conical surface 111 and the concave surface 113, there is a first curved surface 212 (first curved surface) that is different from the second conical surface 112 in the first embodiment. Between the concave surface 113 and the fourth conical surface 115, there is a second curved surface 214 (second curved surface) that is different from the third conical surface 114 in the first embodiment.

[0078] The first curved face 212 is from the hole opening side of the first conical face 111 ( Figure 6 The BOS (Bend-Off Surface) shown has an end edge that extends towards the aperture opening side and is inclined in a manner that the closer to the aperture opening side, the further outward it is in the aperture direction, forming an annular shape centered on the aperture axis. The first curved surface 212 forms an arc-shaped cross-section including the aperture axis with its center on the outer side in the aperture direction. The first curved surface 212 is significantly further inward in the aperture direction than the conical surface that connects the end edge of the first conical surface 111 on the aperture opening side and the end edge of the fourth conical surface 115 on the aperture bottom side in the aperture axis direction. The first curved surface 212 is an annular shape with a constant diameter on both the small and large diameter sides along the entire circumference of the aperture.

[0079] The second curved surface 214 is disposed closer to the hole opening side than the first curved surface 212. The second curved surface 214 is a curved surface extending from the end edge of the concave surface 113 on the hole opening side towards the hole opening side and inclined in a manner that the closer to the hole opening side, the further outward it is in the hole diameter direction, forming an annular shape centered on the hole axis. The cross-section of the second curved surface 214, including the hole axis, has a central arc shape on the outer side in the hole diameter direction. This cross-section of the second curved surface 214 is disposed on the same arc as the first curved surface 212. The second curved surface 214 is positioned relative to the end edge of the first conical surface 111 on the hole opening side and the bottom side of the fourth conical surface 115 (…). Figure 6 The conical surface connected to the end edge of the BBS shown in the diagram moves significantly further inward toward the bore diameter direction as it approaches the bottom of the bore in the axial direction. The second curved surface 214 is an annular shape with a constant diameter on both the small and large diameter sides along the circumference of the bore.

[0080] The first curved portion 212 and the second curved portion 214 decrease in diameter towards the bottom of the hole in the axial direction. The diameter reduction rate of the first curved portion 212 is smaller than that of the second curved portion 214, and the diameter reduction is gradual. In other words, the first curved portion 212 and the second curved portion 214 increase in diameter towards the hole opening in the axial direction. The diameter expansion rate of the first curved portion 212 is smaller than that of the second curved portion 214, and the diameter expansion is gradual.

[0081] The first curved surface 212 and the second curved surface 214 form a convex R shape that protrudes radially inward compared to the conical surfaces of the end edge of the first conical surface 111 on the aperture side and the end edge of the fourth conical surface 115 on the aperture bottom side. An annular concave surface 113, i.e., an annular bottom groove 118, is formed between the first curved surface 212 and the second curved surface 214, recessed outward in the aperture direction. The groove bottom surface 203 has: a first curved surface 212, which expands in diameter as it moves further outward in the aperture direction towards the aperture opening side; and a second curved surface 204, which is positioned further outward in the aperture direction than the first curved surface 212 and expands in diameter as it moves further outward in the aperture direction towards the aperture opening side, with a larger expansion rate than the first curved surface 212.

[0082] According to the second embodiment, since the groove bottom portion 203 is bulging inward in the bore diameter direction, even if the sealing member 22 moves within the gap in the bore axis direction, it becomes difficult to impede the deflection of the sealing member 22. In addition, since the bulging shape of the groove bottom portion 203 increases the interference of the sealing member 22, the return amount when the piston 21 is hydraulically released can be increased.

[0083] According to the second embodiment, such as Figure 5 As shown by the double-dotted line X4, the piston return amount can be increased from low pressure to high pressure, with the rate of increase of piston return amount relative to the unit rise of hydraulic pressure being approximately the same as in the first embodiment.

[0084] In this embodiment, the disc brake 10 is a floating type where the caliper 15 can move relative to the disc rotor 11 in the disc shaft direction. Therefore, the piston 21, located on one side of the disc rotor 11, presses the brake pads 13 and 14 on both sides against the disc rotor 11. In contrast, in the case of a fixed type caliper where the caliper cannot move relative to the disc rotor in the disc shaft direction, the piston only presses the brake pad located on one side between itself and the disc rotor. The shape of the sealing groove 55 described above can also be applied to such a fixed type caliper. That is, the shape of the sealing groove 55 can be applied to a disc brake having a piston for pressing at least one brake pad onto the disc rotor.

[0085] Furthermore, the sealing member 22 is explained using the following example: when its shape is circular in its natural state, the cross-sectional shape when forming a cross-section on the surface including the central axis is a rectangle with a long side parallel to the central axis. However, the cross-sectional shape when forming a cross-section on the surface including the central axis can also be a square with two sides parallel to the central axis. That is, the sealing member 22 only needs to have a square cross-sectional shape when forming a cross-section on the surface including the central axis.

[0086] According to a first aspect of the disc brake according to the above embodiment, the disc brake includes: brake pads disposed on both sides clamping a disc rotor; a piston for pushing at least one of the brake pads toward the disc rotor; a cylinder bore in which the piston is slidably fitted; a sealing groove provided in the cylinder bore as an annular groove recessed from its inner circumferential surface; and a sealing member with a square cross-section that fits into the sealing groove to seal the space between the piston and the cylinder bore. The sealing groove has: a bottom portion inclined in a direction expanding toward the opening side of the cylinder bore; a side portion extending from the larger diameter side of the bottom portion toward the opening side of the sealing groove; and a chamfered portion formed between the side portion and the inner circumferential surface of the cylinder bore, which expands the opening of the sealing groove axially in the cylinder bore. The chamfered portion has two radii of curvature. This suppresses drag.

[0087] Furthermore, the second aspect is characterized in that, in the first aspect, the chamfered portion has: a first radius of curvature formed on the bottom surface side of the sealing groove, and a second radius of curvature formed on the inner circumferential surface side of the cylinder bore that is smaller than the first radius of curvature.

[0088] Furthermore, the third aspect is characterized in that, in the first or second aspect, the bottom surface has: a first curved surface that expands in diameter such that it is located radially outward from the opening side of the cylinder bore; and a second curved surface that is disposed closer to the opening side of the cylinder bore than the first curved surface, and has a larger diameter expansion rate than the first curved surface.

[0089] Industrial availability

[0090] The disc brake described above can suppress drag.

[0091] Explanation of reference numerals in the attached figures

[0092] 10: Disc brake

[0093] 11: Disc rotor

[0094] 13, 14: Brake pads

[0095] 21: Piston

[0096] 22: Sealing components

[0097] 35: Cylinder bore

[0098] 51: Guiding inner circumferential surface (inner circumferential surface)

[0099] 55: Sealing groove

[0100] 60: Opening (opening of the cylinder bore)

[0101] 103, 203: Bottom surface of the channel (bottom surface)

[0102] 104: Side view of the hole opening (side view)

[0103] 105: Chamfered section on the side of the hole opening (bevel)

[0104] 108: Groove opening (opening of the sealing groove)

[0105] 121: First radius of curvature

[0106] 122: Second radius of curvature

[0107] 212: First curved face (first curved surface)

[0108] 214: Second Curved Face (Second Curved Surface)

[0109] r1, r2: radii of curvature

Claims

1. A disc brake, wherein, have: A pair of brake pads, which clamp the disc rotor, are arranged on both sides; A piston that presses at least one of the pair of brake pads toward the disc rotor; A cylindrical cylinder bore that houses the piston and has a cylinder bore opening that opens toward at least one of the pair of brake pads, a cylinder bore bottom located opposite the cylinder bore opening, and an inner circumferential surface of the cylinder bore for the piston to slide on its outer circumferential surface when the piston moves within the cylinder bore. The annular sealing groove, in a cross section within the cylinder bore orthogonal to the direction of piston movement, is recessed further away from the central axis than the inner circumferential surface of the cylinder bore when the axis passing through the center of the cylinder bore and parallel to the direction of piston movement is taken as the central axis. A sealing component with a square cross-section when cut along the central axis is disposed in the sealing groove and seals the piston and the cylinder bore; The sealing groove has: The closer the bottom surface is to the cylinder bore opening in the direction of the central axis, the farther it is from the inner circumferential surface of the cylinder bore. The side portion extends radially toward the inner circumferential surface of the cylinder bore from the bottom portion near the cylinder bore opening on the central axis; A chamfered portion, which bends chamferedly from the side portion near the cylinder bore opening toward the cylinder bore opening; A cylindrical facet extends from the chamfered portion approaching the cylinder bore opening in the direction of the central axis toward the cylinder bore opening, and the length of the cylindrical facet in the direction of the central axis is longer than the length of the chamfered portion in the direction of the central axis. A planar portion extends radially toward the inner circumferential surface of the cylinder bore from the cylindrical face near the cylinder bore opening on the central axis and is connected to the inner circumferential surface of the cylinder bore.

2. The disc brake as described in claim 1, wherein, The length of the chamfered portion in the radial direction relative to the central axis is longer than the length of the flat portion in the radial direction relative to the central axis.

3. The disc brake as described in claim 1, wherein, The sealing groove has: The bottom side surface of the cylinder bore extends radially toward the inner circumferential surface of the cylinder bore from the bottom surface near the bottom of the cylinder bore on the central axis; The bottom chamfer portion of the cylinder bore is located between the bottom side surface of the cylinder bore and the inner circumferential surface of the cylinder bore. In the radial direction relative to the central axis, the closer it is to the cylinder bore opening, the farther it is from the inner circumferential surface of the cylinder bore. The distance from the inner circumferential surface of the cylinder bore to the bottom side surface of the cylinder bore is longer than the distance from the inner circumferential surface of the cylinder bore to the side surface.

Images