JP6376883B2 - Disc brake - Google Patents

Description

  The present invention relates to a disc brake used for braking a vehicle.

  Some conventional disc brakes include a planetary gear reduction mechanism that includes a rotation restricting mechanism (ratchet mechanism) for maintaining braking force during parking braking or the like (see Patent Document 1).

JP 2010-169248 A

  However, in the disc brake of Patent Document 1, the configuration for maintaining the braking force is complicated, and there is a risk that the manufacturing efficiency of the disc brake will be reduced.

  An object of this invention is to provide the disc brake which simplifies the structure which hold | maintains braking force at the time of parking brake etc., and improves manufacturing efficiency.

As means for solving the above problems, the disc brake of the present invention includes a pair of pads disposed on both sides of the rotor in the axial direction with a rotor interposed therebetween, and one piston for pressing one of the pair of pads against the rotor. A caliper main body having a cylinder in which the piston is movably disposed, an electric motor provided in the caliper main body, and a rotary linear motion conversion mechanism provided in the caliper main body for propelling the piston and holding it in a braking position. The rotation / linear motion conversion mechanism includes: a rotation transmission member that transmits the rotation of the electric motor; a shaft member that is screw-fitted to the rotation transmission member and is rotatable; A ball-and-ramp mechanism that is screwed to the shaft member and applies axial thrust to the piston by rotation of the shaft member. The first member is formed with a first screw portion that is screw-fitted to the rotation transmission member on one end side, and is formed with a second screw portion that is screw-fitted to the ball and ramp mechanism on the other end side, The rotational resistance torque of the first threaded portion is greater than the rotational resistance torque of the second threaded portion.

  ADVANTAGE OF THE INVENTION According to this invention, the structure which hold | maintains braking force at the time of parking brake etc. can be simplified, and the disc brake which improves manufacturing efficiency can be provided.

Sectional drawing which shows the disc brake which concerns on this embodiment. FIG. 3 is an enlarged cross-sectional view of a rotation / linear motion conversion mechanism employed in the disc brake. Sectional drawing which follows the AA line of FIG. Sectional drawing which follows the BB line of FIG. FIG. 3 is an exploded perspective view of a rotation / linear motion conversion mechanism employed in the disc brake. Sectional drawing which showed the effect | action at the time of operating a parking brake in steps. Sectional drawing which showed the effect | action at the time of operating a parking brake in steps. Sectional drawing which showed the effect | action at the time of operating a parking brake in steps. Sectional drawing which showed the effect | action at the time of operating a parking brake in steps. Sectional drawing which showed the effect | action at the time of releasing a parking brake in steps. Sectional drawing which showed the effect | action at the time of releasing a parking brake in steps. Sectional drawing which showed the effect | action at the time of releasing a parking brake in steps.

Hereinafter, the present embodiment will be described in detail with reference to FIGS.
As shown in FIG. 1, the disc brake 1 includes a pair of inner brake pads 2 and outer brake pads 3 disposed on both sides in the axial direction with a disc rotor D attached to a rotating portion of the vehicle, and a caliper 4. And are provided. The disc brake 1 is configured as a caliper floating type. The pair of inner brake pads 2 and outer brake pads 3 and the caliper 4 are supported by a bracket 5 fixed to a non-rotating portion such as a knuckle of the vehicle so as to be movable in the axial direction of the disc rotor D. Hereinafter, for convenience of explanation, the right side of the drawing will be described as one end side, and the left side will be appropriately described as the other end side.

  The caliper body 6 that is the main body of the caliper 4 includes a cylinder portion 7 that is disposed on the base end side facing the inner brake pad 2 on the vehicle inner side, and a claw that is disposed on the distal end side facing the outer brake pad 3 on the vehicle outer side. Part 8. The cylinder portion 7 is formed with a bottomed cylinder 15 that is a large-diameter opening portion 9 </ b> A that is open on the inner brake pad 2 side and is closed on the opposite side by a bottom wall 11 having a hole 10. The bottom wall 11 side in the cylinder 15 is connected to the large diameter opening 9A, and a small diameter opening 9B having a smaller diameter than the large diameter opening 9A is formed. The cylinder 15 has a piston seal 16 disposed on the inner peripheral surface of the large-diameter opening 9A.

  As shown in FIGS. 1 and 2, the piston 18 is formed in a bottomed cup shape including a bottom portion 19 and a cylindrical portion 20. The piston 18 is accommodated in the cylinder 15 so that the bottom portion 19 faces the inner brake pad 2. The piston 18 is housed in the large-diameter opening 9A of the cylinder 15 so as to be movable in the axial direction while being in contact with the piston seal 16. A space between the piston 18 and the bottom wall 11 of the cylinder 15 is defined by a piston seal 16 as a hydraulic chamber 21. The fluid pressure chamber 21 is supplied with fluid pressure from a fluid pressure source (not shown) such as a master cylinder or a fluid pressure control unit through a port (not shown) provided in the cylinder portion 7. A plurality of rotation restricting vertical grooves 22 are formed along the circumferential direction on the inner peripheral surface of the piston 18. In the present embodiment, twelve rotation regulating longitudinal grooves 22 are formed along the circumferential direction (see FIG. 3).

  A recess 25 is provided on the outer peripheral side of the other end surface of the bottom portion 19 of the piston 18 facing the inner brake pad 2. The concave portion 25 is engaged with a convex portion 26 formed on the back surface of the inner brake pad 2, and the piston 18 is prevented from rotating with respect to the cylinder 15 and eventually the caliper body 6 by this engagement. Further, a dust boot 27 is interposed between the outer peripheral surface of the bottom portion 19 of the piston 18 and the inner peripheral surface of the large-diameter opening 9 </ b> A of the cylinder 15 to prevent foreign matter from entering the cylinder 15. . One end surface of the bottom portion 19 of the piston 18 facing the rotation / linear motion converting mechanism 43 has a circular plane portion 30 provided at the radial center portion thereof, and an inner periphery of the piston 18 continuously from the circular plane portion 30. An annular curved surface portion 31 extending so as to expand toward the one end side toward the surface is formed.

  As shown in FIG. 1, a housing 35 is attached to the bottom wall 11 side of the cylinder 15 in an airtight manner. A cover 36 is airtightly attached to one end opening of the housing 35. The housing 35 and the cylinder part 7 are kept airtight by a seal member 37. Further, the housing 35 and the cover 36 are kept airtight by a seal member 38. An electric motor 40 is hermetically attached to the housing 35 via a seal member 41 so as to be aligned with the caliper body 6. In the present embodiment, the motor 40 is disposed outside the housing 35, but the housing 35 may be formed so as to cover the motor 40 and the motor 40 may be accommodated in the housing 35. In this case, the sealing member 41 becomes unnecessary, and the number of assembling steps can be reduced. Further, the housing 35 and the cover 36 may be welded and joined. In this case, the seal member 38 becomes unnecessary, and the number of assembling steps can be reduced.

  The caliper body 6 is provided with a rotation / linear motion conversion mechanism 43 that propels the piston 18 and holds it in the braking position, and a spur multi-stage reduction mechanism 44 and a planetary gear reduction mechanism 45 that increase the rotation by the motor 40. . The spur multi-stage reduction mechanism 44 and the planetary gear reduction mechanism 45 are housed in the housing 35.

  The rotation / linear motion conversion mechanism 43 converts the rotational motion from the spur multi-stage speed reduction mechanism 44 and the planetary gear speed reduction mechanism 45, that is, rotation of the motor 40 into linear motion (hereinafter referred to as linear motion), and thrusts the piston 18. To hold the piston 18 in the braking position. The rotation / linear motion conversion mechanism 43 is accommodated between the bottom wall 11 of the cylinder 15 and the bottom portion 19 of the piston 18, and includes a base nut 75, a push rod 102, and a ball and ramp mechanism 127. The base nut 75 is configured as a rotation transmission member that transmits the rotation of the motor 40, is rotatably supported by the cylinder 15, and rotates from the motor 40 through the spur multi-stage reduction mechanism 44 and the planetary gear reduction mechanism 45. Is transmitted. The base nut 75 is configured as a rotation transmission member that transmits the rotation of the motor 40. In the push rod 102, a first male screw portion 103 that is screwed into the female screw portion 97 of the base nut 75 is formed on one end side, and a second male screw portion 104 is formed on the other end side. The push rod 102 is configured as a shaft member that is screw-fitted to the rotation transmitting member and is supported so as to be rotatable and linearly movable. The ball and ramp mechanism 127 is screwed into the second male threaded portion 104 of the push rod 102 and applies an axial thrust to the piston 18 by the rotation of the push rod 102. In the rotation / linear motion converting mechanism 43 of the present embodiment, a first screw fitting portion 105 is configured between the female screw portion 97 of the base nut 75 and the first male screw portion 103 of the push rod 102. Further, in the rotation / linear motion conversion mechanism 43 of the present embodiment, the second screw fitting is performed between the female screw portion 162 of the rotation / linear motion ramp 151 of the ball and ramp mechanism 127 and the second male screw portion 104 of the push rod 102. Unit 106 is configured.

  The spur multi-stage reduction mechanism 44 has a pinion gear 46, a first reduction gear 47, and a second reduction gear 48. The pinion gear 46 is formed in a cylindrical shape, and has a hole 50 that is press-fitted and fixed to the rotary shaft 40 </ b> A of the motor 40, and a gear 51 that is formed on the outer peripheral surface. The first reduction gear 47 is integrally formed with a large-diameter large gear 53 that meshes with the gear 51 of the pinion gear 46 and a small-diameter small gear 54 that extends from the large gear 53 in the axial direction. . The first reduction gear 47 is rotatably supported by a shaft 55 having one end supported by the housing 35 and the other end supported by the cover 36. The second reduction gear 48 is integrally formed with a large-diameter large gear 56 that meshes with the small gear 54 of the first reduction gear 47 and a small-diameter sun gear 57 that extends from the large gear 56 in the axial direction. Yes. The sun gear 57 constitutes a part of the planetary gear reduction mechanism 45. The second reduction gear 48 is rotatably supported by a shaft 58 supported by the cover 36.

  The planetary gear reduction mechanism 45 includes a sun gear 57, a plurality of (for example, three) planetary gears 60, an internal gear 61, and a carrier 62. The planetary gear 60 has a gear 63 meshed with the sun gear 57 of the second reduction gear 48 and a hole portion 64 through which a pin 65 erected from the carrier 62 is inserted. The three planetary gears 60 are arranged at equal intervals on the circumference of the carrier 62.

  The carrier 62 is formed in a disk shape, and a polygonal hole 68 into which the polygonal column 81 of the base nut 75 is fitted is formed at the center in the radial direction. When the polygonal column 81 provided continuously from the tip of the cylindrical portion 76 of the base nut 75 is fitted into the polygonal hole 68, rotational torque can be transmitted between the carrier 62 and the base nut 75. A plurality of pin holes 69 are formed on the outer peripheral side of the carrier 62. A pin 65 for rotatably supporting each planetary gear 60 is press-fitted and fixed in each pin hole 69. The carrier 62 and each planetary gear 60 are formed by a wall surface 35B projecting from the periphery of the opening 35A of the housing 35 to one end side, and an annular wall portion 72 provided integrally on the second reduction gear 48 side of the internal gear 61. Axial movement is restricted. In this embodiment, the relative rotation with the base nut 75 is restricted by the polygonal hole 68 provided in the carrier 62, but a mechanical element capable of transmitting rotational torque such as a spline or a key may be adopted. .

  The internal gear 61 is integrally provided on the second reduction gear 48 side continuously from the internal teeth 71 with which the gears 63 of the respective planetary gears 60 are engaged, and moves in the axial direction of the planetary gear 60. It is formed from an annular wall portion 72 to be regulated. The internal gear 61 is press-fitted and fixed in the housing 35.

  In this embodiment, in order to obtain the rotational force for propelling the piston 18, a spur multi-stage reduction mechanism 44 and a planetary gear reduction mechanism 45 are provided as reduction mechanisms that increase the rotation by the motor 40. Any one or both of the speed reduction mechanisms may be omitted as long as the rotational force can be output.

  As shown in FIGS. 2 and 5, the base nut 75 is configured to include a cylindrical portion 76 and a nut portion 77 provided integrally with the other end portion of the cylindrical portion 76. A washer 80 is disposed in contact with the bottom wall 11 of the cylinder 15. The cylindrical portion 76 of the base nut 75 is inserted into each of the insertion hole 80 </ b> A of the washer 80 and the hole portion 10 provided in the bottom wall 11 of the cylinder 15. A polygonal column part 81 that is chamfered in a polygonal shape is formed on the tip side of the cylindrical part 76. The polygonal column part 81 is inserted into the opening 35 </ b> A of the housing 35 and fitted into the polygonal hole 68 of the carrier 62. In this embodiment, as shown in FIG. 5, the polygonal column part 81 is formed in a hexagon, and the polygonal hole 68 is formed in a hexagonal hole. The polygonal column portion 81 may be a hexagon, a polygon such as a triangle, a quadrangle, a pentagon, a heptagon, and an octagon, or a two-sided shape. The nut portion 77 of the base nut 75 is formed in a bottomed cylindrical shape. The nut portion 77 is formed on the base end side of the cylindrical portion 76, and one end surface of the nut portion 77 protrudes integrally from the other end surface of the circular wall portion 82 and the circular wall portion 82 facing the bottom wall 11 of the cylinder 15. And a cylindrical portion 83. The circular wall portion 82 is disposed so that its outer peripheral surface is close to the inner wall surface of the small-diameter opening 9B of the cylinder 15. A small-diameter circular wall 84 protrudes from one end surface of the circular wall 82 from the central portion in the radial direction. The columnar part 76 protrudes from one end surface of the small-diameter circular wall part 84. The outer diameter of the cylindrical portion 76 is formed smaller than the outer diameter of the cylindrical portion 83 of the nut portion 77.

  A thrust bearing 87 is disposed between the base nut 75 and the washer 80. The thrust bearing 87 contacts the circular wall portion 82 around the small-diameter circular wall portion 84 of the nut portion 77 of the base nut 75. The base nut 75 is rotatably supported by the bottom wall 11 of the cylinder 15 by a thrust bearing 87. A seal member 88 and a sleeve 89 are provided between the outer peripheral surface of the cylindrical portion 76 of the base nut 75 and the hole 10 of the bottom wall 11 of the cylinder 15. The seal member 88 and the sleeve 89 are provided to maintain the fluid tightness of the hydraulic chamber 21. An annular groove 81 </ b> A is formed between the cylindrical portion 76 of the base nut 75 and the polygonal column portion 81. A retaining ring 90 is mounted in the annular groove 81A. The retaining ring 90 restricts the movement of the base nut 75 in the axial direction of the cylinder 15.

  The cylindrical portion 83 of the nut portion 77 of the base nut 75 includes a large diameter cylindrical portion 91 disposed on one end side and a small diameter cylindrical portion 92 disposed on the other end side. The inner peripheral surface 91 </ b> A of the large diameter cylindrical portion 91 and the inner peripheral surface 92 </ b> A of the small diameter cylindrical portion 92 are formed by a hole 83 </ b> A that opens to the other end of the cylindrical portion 83. One end of the large diameter cylindrical portion 91 is integrally connected to the circular wall portion 82. Between the outer peripheral surface of the large-diameter cylindrical portion 91 and the outer peripheral surface of the small-diameter cylindrical portion 92, an annular step surface 93 that faces the bottom portion 19 of the piston 18 is provided. The annular step surface 93 has a plurality of concave and convex portions 94 protruding in the axial direction of the base nut 75 and is formed in a continuous wave shape along the circumferential direction. A plurality of through-holes 95 extending in the radial direction of the large-diameter cylindrical portion 91 and penetrating therethrough are formed in the large-diameter cylindrical portion 91. A plurality of through holes 95 are formed at intervals in the circumferential direction. A female screw portion 97 is formed on the inner peripheral surface 92 </ b> A of the small diameter cylindrical portion 92 of the nut portion 77. A plurality of locking grooves 98 (for example, four locations) are formed on the other end surface of the peripheral wall portion of the small-diameter cylindrical portion 92 at intervals in the circumferential direction (see FIGS. 4 and 5).

  As shown in FIGS. 2, 4, and 5, the leading end portion 100 </ b> A of the first spring clutch 100 is fitted into any one of the locking grooves 98. The first spring clutch 100 has a distal end portion 100A facing outward in the radial direction and a coil portion 100B wound in a single layer from the distal end portion 100A. Then, the distal end portion 100A is fitted into one of the locking grooves 98, and the coil portion 100B is wound around the outer periphery on the other end side of the first male screw portion 103 of the push rod 102. The first spring clutch 100 has a rotational resistance torque with respect to the rotational direction when the push rod 102 moves toward the bottom wall 11 of the cylinder 15 with respect to the base nut 75, that is, the rotational direction when releasing to release the parking brake. On the other hand, the push rod 102 is configured to allow rotation in the rotation direction when the push rod 102 moves toward the bottom 19 of the piston 18 with respect to the base nut 75, that is, in the rotation direction at the time of applying the parking brake. Has been. That is, the first spring clutch 100 is configured as a first one-way clutch that imparts rotational resistance to rotation in one direction.

  One end of the push rod 102 is disposed in the hole 83 </ b> A of the nut portion 77 of the base nut 75. On one end side of the push rod 102, a first male screw portion 103 for forming the first screw fitting portion 105 is formed by screw fitting with the female screw portion 97 of the small diameter cylindrical portion 92 of the base nut 75. . The first screw fitting portion 105 has a large irreversibility so that its reverse efficiency becomes 0 or less so that the base nut 75 does not rotate due to the axial load transmitted from the piston 18 to the push rod 102. It is comprised as a screw fitting part.

  On the other hand, on the other end side of the push rod 102, a second male screw portion for constituting a second male screw portion 104 that is screwed into a female screw portion 162 provided on the rotary linear motion lamp 151 of the ball and ramp mechanism 127. 104 is formed. The second screw fitting portion 106 has a reverse efficiency of 0 or less, that is, irreversible so that the push rod 102 does not rotate due to the axial load transmitted from the piston 18 to the rotary linear motion ramp 151. Is configured as a large screw fitting portion.

  The push rod 102 is provided with a spline shaft 108 between the first male screw portion 103 and the second male screw portion 104. The outer diameter of the first male screw portion 103 is formed larger than the outer diameter of the second male screw portion 104. The outer diameter of the first male screw portion 103 is formed larger than the outer diameter of the spline shaft 108. The other end surface of the push rod 102 faces the circular flat portion 30 of the bottom portion 19 of the piston 18.

  A retainer 110 is supported between the outer peripheral surface of the small diameter cylindrical portion 92 of the base nut 75 and the inner peripheral surface of the cylindrical portion 20 of the piston 18 so as to be movable in the axial direction. The retainer 110 has an annular wall portion 111 on one end side facing the annular step surface 93 of the base nut 75, and is configured in a substantially cylindrical shape as a whole. A plurality of convex portions 112 are formed on one end surface of the annular wall portion 111 at intervals along the circumferential direction. A concave surface 113 is formed on one end side of the outer peripheral surface of the retainer 110. A plurality of circular through holes 114 are formed in the outer peripheral wall including the concave surface 113 of the retainer 110. In the present embodiment, the circular through-holes 114 are formed at three locations in the range of the concave surface 113 at intervals in the circumferential direction, and 3 at intervals in the circumferential direction on the outer peripheral wall on the other end side other than the concave surface 113. A part is formed (see FIGS. 3 and 5). A plurality of rectangular through holes 115 are formed in the range of the concave surface 113 on the outer peripheral wall of the retainer 110. In the present embodiment, three rectangular through holes 115 are formed at intervals in the circumferential direction (see FIG. 4).

  Within the retainer 110, one end side washer 120, a coil spring 121, the other end side washer 122, a support plate 123, a second spring clutch 124, a rotating member 125, a thrust bearing 126, a ball and ramp mechanism 127, in order from one end side. A thrust bearing 128 and an annular pressing plate 129 are arranged. The one end side washer 120 is disposed so as to contact the other end surface of the annular wall portion 111 of the retainer 110.

  The coil spring 121 is interposed between the one end side washer 120 and the other end side washer 122. The coil spring 121 biases the one end side washer 120 and the other end side washer 122 in a direction in which the one end side washer 120 and the other end side washer 122 are separated from each other. A plurality of (for example, three) locking grooves 132 having a predetermined depth are formed on the other end surface of the peripheral wall portion of the retainer 110 at intervals in the circumferential direction. The locking groove 132 includes a narrow locking groove 133 positioned on one end side of the retainer 110 and a wide locking groove 134 positioned on the other end side. The wide locking groove 134 is formed so that the depth dimension is larger than the depth dimension of the narrow locking groove 133. The retainer 110 is formed with a plurality of claw portions 136 (for example, six locations) extending toward the inner diameter side at the other end portion facing the bottom portion 19 of the piston 18. Each claw 136 is disposed at a predetermined position in the retainer 110 at one end side washer 120, coil spring 121, other end side washer 122, support plate 123, second spring clutch 124, rotating member 125, thrust bearing 126, ball and ramp. After the structural members such as the mechanism 127, the thrust bearing 128, and the annular pressing plate 129 are accommodated, the structural members described above are integrated into the retainer 110 by being folded toward the accommodating recess 171 of the annular pressing plate 129 of the retainer 110. Will be placed in. In addition, you may comprise without providing the one end side washer 120 and the other end side washer 122. FIG.

  It arrange | positions so that the cyclic | annular support plate 123 may contact | abut to the other end surface of the other end side washer 122. FIG. A plurality of protrusions 137 (for example, three locations) are provided on the outer peripheral surface of the support plate 123 at intervals along the circumferential direction. Each protruding piece 137 is fitted into the narrow locking groove 133 of the retainer 110. As a result, the support plate 123 is supported such that it cannot rotate relative to the retainer 110 and can move relative to the axial direction. The protruding piece 137 may be configured to be widened and engaged with the rotation restricting vertical groove 22 provided on the inner peripheral surface of the piston 18.

  In the retainer 110, the rotation member 125 is rotatably supported on the other end side of the support plate 123. The rotating member 125 includes a large-diameter annular portion 141 having a spline hole 140 and a small-diameter cylindrical portion 142 that projects integrally from one end surface of the large-diameter annular portion 141. One end of the small diameter cylindrical portion 142 is in contact with the other end surface of the support plate 123. An annular groove 143 is formed on the outer peripheral surface of the small diameter cylindrical portion 142. The push rod 102 is disposed in the rotating member 125. The spline hole 140 of the large-diameter annular portion 141 of the rotating member 125 is splined to the spline shaft 108 of the push rod 102. As a result, the rotating member 125 and the push rod 102 can be slid relative to each other in the axial direction while transmitting the rotational torque therebetween. Although a spline is used as a detent, other known anti-rotation machine elements such as key fitting and D hole may be used. Moreover, you may make it fix by press-fitting etc., without making it slide in an axial direction.

  The second spring clutch 124 is wound around the annular groove 143 provided in the small diameter cylindrical portion 142 of the rotating member 125. Similar to the first spring clutch 100, the second spring clutch 124 has a distal end portion 124A facing outward in the radial direction, and a coil portion 124B wound around the distal end portion 124A. The distal end portion 124A is fitted into the narrow locking groove 133 of the retainer 110, and the coil portion 124B is wound around the annular groove 143 provided on the outer peripheral surface of the small diameter cylindrical portion 142 of the rotating member 125. The second spring clutch 124 applies a rotational resistance torque to the rotational direction (the rotational direction at the time of application) when the rotational member 125 (push rod 102) moves toward the bottom 19 side of the piston 18 with respect to the retainer 110. On the other hand, it is configured to allow rotation in the rotational direction (rotational direction at release) when moving to the bottom wall 11 side of the cylinder 15. That is, the second spring clutch 124 is configured as a second one-way clutch that imparts rotational resistance to rotation in one direction.

  The rotational resistance torque when the second spring clutch 124 is applied is greater than the rotational resistance torque of the first screw fitting portion 105 between the first male screw portion 103 of the push rod 102 and the female screw portion 97 of the base nut 75. Set to be larger. A ball and ramp mechanism 127 is disposed on the other end side of the rotating member 125 via a thrust bearing 126. The rotating member 125 is rotatably supported by a ball and ramp mechanism 127 via a thrust bearing 126.

  As shown in FIGS. 2, 3, and 5, the ball-and-ramp mechanism 127 includes the fixed lamp 150, the rotary linear motion lamp 151, and each interposed between the fixed ramp 150 and the rotational linear motion ramp 151. And a ball 152. The fixed lamp 150 is disposed on the other end side of the rotating member 125 with the thrust bearing 126 interposed therebetween. The fixed lamp 150 includes a disk-shaped fixed plate 154 and a plurality of convex portions 155 (for example, three locations) that protrude from the outer peripheral surface of the fixed plate 154 along the circumferential direction. Configured. The fixing plate 154 is formed with an insertion hole 156 through which the push rod 102 is inserted in the central portion in the radial direction. In the fixed lamp 150, each convex portion 155 is fitted into the wide locking groove 134 of each locking groove 132 of the retainer 110, and a plurality of rotation restricting vertical grooves 22 provided on the inner peripheral surface of the piston 18. Is supported so that it cannot rotate relative to the piston 18 and is movable in the axial direction.

  In addition, as a structure in which the fixed ramp 150 is supported so as not to rotate relative to the piston 18 and to be movable in the axial direction, a plurality of plane portions are formed on the outer peripheral surface of the fixed ramp 150 at intervals in the circumferential direction. Then, a plurality of flat portions corresponding to the respective flat portions of the fixed ramp 150 are formed on the inner peripheral surface of the piston 18, and the rotation of the fixed ramp 150 with respect to the piston 18 is restricted by bringing these flat portions into contact with each other. You may comprise. The other end surface of the fixed plate 154 has a plurality of ball grooves 157 (for example, three or four locations) having a predetermined inclination angle along the circumferential direction and extending in an arc shape and having an arc-shaped cross section in the radial direction. ) Is formed.

  The rotation / linear motion ramp 151 includes an annular rotation / linear motion plate 160 and a cylindrical portion 161 that projects integrally from the radial center of the other end surface of the rotation / linear motion plate 160. . On the inner peripheral surface from the rotary translation plate 160 to the cylindrical portion 161, a female screw portion 162 into which the second male screw portion 104 of the push rod 102 is screwed is formed. A plurality of ball grooves having a predetermined inclination angle along the circumferential direction and extending in an arc shape and having an arc-shaped cross section in the radial direction on a surface of the rotary linear motion plate 160 facing the fixed plate 154 of the fixed lamp 150 163 (for example, three or four places) are formed. In addition, each ball groove 157 of the fixed ramp 150 and each ball groove 163 of the rotation linear motion ramp 151 are configured such that a depression is provided in the middle of the inclination along the circumferential direction, or the inclination is changed in the middle. Also good.

  The ball 152 is interposed between each ball groove 163 of the rotation linear motion ramp 151 (rotation linear motion plate 160) and each ball groove 157 of the stationary ramp 150 (fixation plate 154). In the ball and ramp mechanism 127, when a rotational torque is applied to the rotation / linear motion ramp 151, the balls 152 between the ball grooves 163 of the rotation / linear motion plate 160 and the ball grooves 157 of the fixed plate 154 roll. Thus, the relative distance in the axial direction between the rotation / linear motion plate 160 and the fixed plate 154 varies due to the difference in rotation between the rotation / linear motion plate 160 and the fixed plate 154.

  In addition, an annular ball groove 164 is formed around the cylindrical portion 161 on the other end surface of the rotary translation plate 160. An annular pressing plate 129 is disposed on the other end side of the rotary translation plate 160 via a thrust bearing 128. An annular ball groove 166 is also formed on one end surface of the annular pressing plate 129. A thrust bearing 128 is disposed between the annular ball groove 164 of the rotary translation plate 160 and the annular ball groove 166 of the annular pressing plate 129 so that a plurality of balls are rotatably supported in the circumferential direction. The cylindrical portion 161 of the rotary translation plate 160 is inserted into the annular pressing plate 129. A plurality of protruding portions 168 are formed on the outer peripheral surface of the annular pressing plate 129 so as to protrude at intervals along the circumferential direction. The annular pressing plate 129 has a plurality of rotation restricting longitudinal grooves 22 provided on the inner peripheral surface of the piston 18 while the convex portions 168 of the annular pressing plate 129 are fitted into the wide engaging grooves 134 of the engaging grooves 132 of the retainer 110. Is supported so that it cannot rotate relative to the piston 18 and is movable in the axial direction.

  The rotation / linear motion ramp 151 of the ball and ramp mechanism 127 is supported by the annular pressing plate 129 through the thrust bearing 128 so as to be rotatable. The other end surface of the annular pressing plate 129 faces the annular curved surface portion 31 of the bottom portion 19 of the piston 18. On the other end surface of the annular pressing plate 129, a curved pressing portion 170 that is curved toward one end side from the radial center toward the outer peripheral end portion is formed. The annular pressing plate 129 is configured to contact the annular curved surface portion 31 provided on the bottom portion 19 of the piston 18 and press the piston 18. On the other end surface of the annular pressing plate 129, an accommodation recess 171 for accommodating each claw portion 136 of the retainer 110 that is folded inward is formed on the outer peripheral portion between the projections 168.

  As shown in FIGS. 2 and 5, a retaining ring 172 is integrally fixed to the tip of the second male screw portion 104 of the push rod 102. The retaining ring 172 is disposed in the cylindrical portion 161 of the rotary linear lamp 151, and restricts the relative rotation angle between the push rod 102 and the rotary linear lamp 151 to a certain value or less. A convex portion 173 is provided on a part of the retaining ring 172, and the convex portion 173 is fitted in the wide concave portion of the cylindrical portion 161. The convex part 173 approaches one side of the concave part when not braking, and approaches the other side when braking, that is, in any case, the convex parts 173 contact each other in the circumferential direction. Thereby, since the relative rotation angle of the retaining ring 172 and the bush rod 102 is limited, it is possible to prevent the retaining ring 172 from dropping from the bush rod 102 due to the thrust by the rotation linear motion lamp 151 in the applied state. The rotational resistance torque of the second screw fitting portion 106 between the second male screw portion 104 of the push rod 102 and the female screw portion 162 of the rotary linear motion ramp 151 of the ball and ramp mechanism 127 is the first spring clutch. The rotation resistance torque in the release direction of the push rod 102 with respect to the base nut 75 by 100 is applied to the first screw fitting portion 105 between the first male screw portion 103 of the push rod 102 and the female screw portion 97 of the base nut 75. It is set to be smaller than the rotational resistance obtained by adding the rotational resistance torque.

  As shown in FIG. 1, the motor 40 is connected to an ECU 175 composed of an electronic control device that is a control means for driving and controlling the motor 40. The ECU 175 is connected to a parking switch 176 that is operated to instruct the operation / release of the parking brake. Further, ECU 175 can be operated regardless of operation of parking switch 176 based on a signal from the vehicle side (not shown).

  Next, the operation of the disc brake 1 according to this embodiment will be described. First, the action at the time of braking of the disc brake 1 as a normal hydraulic brake by the operation of a brake pedal (not shown) will be described.

  When the driver depresses the brake pedal, the hydraulic pressure corresponding to the depressing force of the brake pedal is supplied from the master cylinder to the hydraulic chamber 21 in the caliper 4 via a hydraulic circuit (both not shown). Thus, the piston 18 moves forward (moves in the left direction in FIG. 1) from the original position during non-braking while pressing the piston seal 16 against the disc rotor D while elastically deforming the piston seal 16. The caliper body 6 moves to the right in FIG. 1 with respect to the bracket 5 by the reaction force of the pressing force of the piston 18, and presses the outer brake pad 3 attached to the claw portion 8 against the disc rotor D. As a result, the disc rotor D is sandwiched between the pair of inner and outer brake pads 2 and 3 to generate a frictional force, and hence a braking force for the vehicle.

  And when a driver | operator releases a brake pedal, supply of the hydraulic pressure from a master cylinder stops, and the hydraulic pressure in the hydraulic pressure chamber 21 falls. Thereby, the piston 18 is retracted to the original position by the restoring force of the elastic deformation of the piston seal 16 and the braking force is released. Incidentally, when the movement amount of the piston 18 increases with the wear of the inner and outer brake pads 2 and 3 and exceeds the limit of elastic deformation of the piston seal 16, slip occurs between the piston 18 and the piston seal 16. By moving the original position of the piston 18 with respect to the caliper body 6 due to this slip, even when the brake pads 2 and 3 are worn, the pad clearance is adjusted to be constant.

  Next, the operation as a parking brake for maintaining the stopped state of the vehicle will be described with reference to FIGS. 6 to 9 show stepwise actions when the parking brake is operated, and FIGS. 10 to 12 show stepwise actions when the parking brake is released.

  First, when the parking switch is operated from the released state of the parking brake and the parking brake is operated (applied), the ECU 175 drives the motor 40 and the planetary gear reduction mechanism 45 via the spur multi-stage reduction mechanism 44. The sun gear 57 is rotated. Due to the rotation of the sun gear 57, the carrier 62 is rotated through each planetary gear 60. Then, the rotational torque from the carrier 62, that is, the rotation of the motor 40 is transmitted to the base nut 75.

  Next, by rotation of the base nut 75 in the apply direction, as shown in FIG. 7, from the initial position shown in FIG. 6 (a state where a predetermined gap is provided between the annular pressing plate 129 and the bottom portion 19 of the piston 18). The first screw fitting portion 105 between the female screw portion 97 of the base nut 75 and the first male screw portion 103 of the push rod 102 relatively rotates, that is, only the base nut 75 rotates in the apply direction. The push rod 102 advances toward the bottom 19 side of the piston 18 along the axial direction. Here, the reason why the push rod 102 does not rotate together with the base nut 75 is that the rotation resistance torque in the apply direction of the rotating member 125 (push rod 102) by the second spring clutch 124 with respect to the retainer 110 is the first resistance of the push rod 102. The push rod 102 is set so as to be larger than the rotational resistance torque by the first screw fitting portion 105 between the male screw portion 103 and the female screw portion 97 of the base nut 75, and by the first spring clutch 100. This is because the rotation of the cylinder 15 with respect to the base nut 75 in the apply direction is permitted.

  As a result, as shown in FIG. 7, the one end side washer 120, the coil spring 121, the other end side washer 122, the support plate 123, the second spring clutch 124, and the rotating member 125 in the retainer 110 including the retainer 110 together with the push rod 102. The thrust bearing 126, the ball-and-ramp mechanism 127, the thrust bearing 128, and the annular pressing plate 129 are integrally moved forward along the axial direction toward the bottom 19 of the piston 18, and the annular pressing plate 129. The curved pressing portion 170 contacts the annular curved surface portion 31 of the bottom portion 19 of the piston 18. By this contact, the piston 18 moves forward, and one end surface of the bottom portion 19 of the piston 18 contacts the inner brake pad 2.

  When the rotation drive of the motor 40 in the apply direction is continued, the piston 18 starts to press the disc rotor D via the brake pads 2 and 3 by the movement of the push rod 102. When this pressing force begins to be generated, the first screw fitting portion 105 between the first male screw portion 103 of the push rod 102 and the female screw portion 97 of the base nut 75 is caused by an axial force that is a reaction force against the pressing force. As the rotational resistance torque increases, the rotational torque required to advance the push rod 102 increases. Then, the rotational resistance torque of the first screw fitting portion 105, which is the necessary rotational torque, becomes larger than the rotational resistance torque of the second spring clutch 124. As a result, as shown in FIG. 8, the push rod 102 starts to rotate in the apply direction together with the rotating member 125 as the base nut 75 rotates. That is, the push rod 102 is rotated with the base nut 75. Then, the second screw fitting portion between the second male screw portion 104 of the push rod 102 and the female screw portion 162 of the rotary linear motion lamp 151 of the ball and ramp mechanism 127 is generated by a reaction force from the pressing force of the disk rotor D. Since the rotational resistance torque in 106 also increases due to the reaction force of the pressing force of the disk rotor D, the rotational torque in the apply direction of the push rod 102 is applied to the ball and ramp mechanism 127 via the second screw fitting portion 106. Is transmitted to the rotation linear motion lamp 151.

  Then, while the linear motion ramp 151 of the ball and ramp mechanism 127 rotates in the apply direction, the linear motion ramp 151 and the fixed ramp 150 are separated from each other against the biasing force of the coil spring 121 by the rolling of each ball 152. Thus, the curved pressing portion 170 of the annular pressing plate 129 further presses the annular curved surface portion 31 of the bottom portion 19 of the piston 18, and the pressing force of the disc rotor D by the inner and outer brake pads 2 and 3 increases. At this time, a force obtained by adding the thrust generated by the ball and ramp mechanism 127 to the thrust generated by the second screw fitting portion 106 is applied to the bottom 19 of the piston 18.

  In the present embodiment, at the initial stage of the application, the first screw fitting portion 105, here, the first screw fitting portion 105 between the male screw portion of the push rod 102 and the female screw portion 97 of the base nut 75 is provided. Since the push rod 102 is moved forward relative to the piston rod 18 to move forward and obtain a pressing force to the disk rotor D, the pair of inner and outer brakes are actuated by the operation of the first screw fitting portion 105. Even if the position of the piston 18 with respect to the cylinder 11 changes due to wear of the pads 2 and 3 with time, the original position of the push rod 102 with respect to the piston 18 can be adjusted.

Here, the lead L when the ball-and-ramp mechanism 127 and the second screw fitting portion 106 operate (the amount of advancement of the rotation / linear motion ramp 151 when the rotation / linear motion ramp 151 makes one rotation) is expressed by the following equation: It is represented by
L = L _SCREW × L _{B & R} / (L _SCREW + L _{B & R} )

However, L _SCREW is a lead of the second screw fitting portion 106 between the second male screw portion 104 of the push rod 102 and the female screw portion 162 of the rotary linear motion lamp 151. L _{B & R} is the lead of each ball groove 163 of the rotary linear motion ramp 151 and each ball groove 157 of the fixed ramp 150. Thereby, based on the value of each lead, the power increase ratio (thrust against the rotational torque) can be set to an appropriate value according to the vehicle on which the disc brake 1 is mounted.

  The ECU 175 drives the motor 40 until the pressing force from the pair of inner and outer brake pads 2 and 3 to the disc rotor D reaches a predetermined value, for example, until the current value of the motor 40 reaches a predetermined value. Thereafter, when the ECU 175 detects that the pressing force to the disk rotor D has reached a predetermined value by the fact that the current value of the motor 40 has reached a predetermined value, the ECU 175 stops energization of the motor 40. Then, since the rotation of the push rod 102 in the apply direction is stopped, the rotation of the rotation linear motion lamp 151 of the ball and ramp mechanism 127 is stopped.

  Thereafter, as shown in FIG. 9, the reaction force of the pressing force from the disk rotor D acts on the rotary linear motion lamp 151, but the rotation of the second male threaded portion 104 of the push rod 102 and the ball and ramp mechanism 127. The second screw fitting portion 106 between the female screw portion 162 of the linear motion lamp 151 is configured as a screw fitting portion that does not reversely operate between the push rod 102 and the rotary linear motion lamp 151 as described above. Further, the first screw fitting portion 105 between the first male screw portion 103 of the push rod 102 and the female screw portion 97 of the base nut 75 is also reversed between the push rod 102 and the base nut 75 as described above. Further, the first spring clutch 100 causes the push rod 102 to rotate with respect to the base nut 75 in the release direction. Since the resistance torque is applied, rotary-to-linear ramp 151 of the ball-and-ramp mechanism 127 is maintained stopped without rotating, the piston 18 is held in the braking position. As a result, the braking force is maintained and the operation of the parking brake is completed. In this state, the reaction force of the pressing force from the disk rotor D is transmitted to the bottom wall 11 of the cylinder 15 via the ball and ramp mechanism 127, the push rod 102, the base nut 75 and the thrust bearing 87 to hold the piston 18. It has become a force. In the present embodiment, only the thrust generated by the ball and ramp mechanism 127 acts on the thrust bearing 126 for which a relatively small diameter must be used, so that the durability of the disc brake 1 is improved. It has become. As described above, in the present disc brake 1, the piston 18 is moved by the ball and ramp mechanism 127 after the piston 18 is moved by the direct movement of the push rod 102 during the application.

  Next, when releasing (releasing) the parking brake, based on the parking release operation of the parking switch 176, the ECU 175 returns the piston 18, that is, moves the motor 40 in the release direction to separate the piston 18 from the disk rotor D. Rotation drive. Accordingly, the spur multi-stage speed reduction mechanism 44 and the planetary gear speed reduction mechanism 45 are rotationally driven in the release direction for returning the piston 18, and the rotational drive is transmitted to the base nut 75 via the carrier 62.

  At this time, since the reaction force of the pressing force from the disk rotor D is acting on the push rod 102, the second male screw portion 104 of the push rod 102 and the female screw portion of the rotary linear motion lamp 151 of the ball and ramp mechanism 127 are applied. 162 and the rotation resistance torque of the second screw fitting portion 106 between the first screw fitting portion 105 and the first screw fitting portion 105 between the first male screw portion 103 of the push rod 102 and the female screw portion 97 of the base nut 75. The rotation resistance torque and the rotation resistance torque in the release direction of the push rod 102 with respect to the base nut 75 by the first spring clutch 100 are applied. For this reason, as shown in FIG. 10, the rotational torque in the release direction from the base nut 75 is transmitted to the push rod 102 (including the rotating member 125), and is also transmitted to the rotary linear motion lamp 151 of the ball-and-ramp mechanism 127. The As a result, the rotation linear motion lamp 151 only rotates in the release direction and returns to the initial position in the rotation direction. At this time, the rotation linear movement lamp 151 does not move in the axial direction, and the position in the axial direction remains unchanged.

  Here, when the rotary linear motion ramp 151 returns to the initial position in the rotational direction, the fixed ramp 154 is urged by the coil spring 121 together with the other end side washer 122, the support plate 123, the rotating member 125, and the thrust bearing 126. Therefore, the support plate 123, the rotating member 125, the thrust bearing 126, and the fixed ramp 154 move forward with respect to the retainer 10 while the balls 152 roll between the ball grooves 157 and 163. For this reason, the bush rod 102 and the rotating member 125 move in the axial direction by a spline. When the rotating member 125 is fixed to the push rod 102 by press fitting or the like, the fixed lamp 154 does not move in the axial direction, and the ball 152 is separated from the ball grooves 157 and 163 in the axial direction, but does not fall off. The subsequent operation is the same. Further, the rotational resistance torque of the second screw fitting portion 106 may be configured to be smaller than the rotational resistance torque of the thrust bearing 128. In this case, the rotary linear motion lamp 151 returns to the axial direction simultaneously with the rotation. It becomes like this.

  Next, when the rotation / linear motion ramp 151 returns to the initial position in the rotation direction, each ball 152 is sandwiched between each ball groove 163 of the rotation / linear motion ramp 151 and each ball groove 157 of the stationary plate 154. The rotation / linear motion ramp 151 can no longer rotate with respect to 154, and the rotation / linear motion ramp 151 stops rotating. As a result, as shown in FIG. 11, only the second screw fitting portion 106 relatively rotates first, and the rotation linear motion ramp 151 of the ball and ramp mechanism 127 moves along with the retainer 110 in the axial direction along the bottom of the cylinder 15. It moves to the wall 11 side (release direction) and returns to the initial position in the axial direction.

  Further, when the motor 40 is driven to rotate in the release direction and the rotation of the base nut 75 in the release direction is continued, the rotation linear motion lamp 151 of the ball and ramp mechanism 127 returns to the initial position in both the rotation direction and the axial direction. At the same time, the screwing position of the second screw fitting part 106 between the second male screw part 104 of the push rod 102 and the female screw part 162 of the rotary linear motion lamp 151 of the ball and ramp mechanism 127 returns to the initial position, The rotation of the push rod 102 in the release direction is stopped. When the rotation of the base nut 75 continues in the release direction, the push rod 102 has a rotational resistance torque in the release direction of the push rod 102 with respect to the base nut 75 by the first spring clutch 100 as shown in FIG. On the other hand, it retreats toward the bottom wall 11 side (release direction) of the cylinder 15 along the axial direction. As a result, the one end side washer 120 in the retainer 110 including the retainer 110 together with the push rod 102, the coil spring 121, the other end side washer 122, the support plate 123, the second spring clutch 124, the rotating member 125, the thrust bearing 126, the ball and The constituent members of the ramp mechanism 127, the thrust bearing 128, and the annular pressing plate 129 are integrally retreated toward the bottom wall 11 side (release direction) of the cylinder 15 along the axial direction. Then, the ECU 175 controls the motor 40 to stop when it reaches the initial position between the annular pressing plate 129 of the rotary linear motion lamp 151 and the annular curved surface portion 31 of the bottom portion 19 of the piston 18 having a predetermined gap. doing. Finally, the piston 18 is retracted to the original position by the restoring force of the elastic deformation of the piston seal 16 and the braking force is completely released. As described above, in the present disc brake 1, upon release, the ball and ramp mechanism 127 is returned to the initial position, the ball and ramp mechanism 127 is moved backward, and then the push rod 102 is moved backward to the piston 19. The holding power is released.

  As described above, in the disc brake 1 according to the present embodiment, when the piston 18 such as a parking brake is propelled and held at the braking position, the pressing force is applied from the pair of inner and outer brake pads 2 and 3 to the disc rotor D. Are added, the first male threaded portion 105 between the first male threaded portion 103 of the push rod 102 and the male threaded portion of the base nut 75 and the second male threaded portion 104 of the push rod 102 are low in mechanical efficiency. Is combined with the second screw fitting portion 106 between the female screw portion 162 of the rotary linear motion lamp 151 of the ball and ramp mechanism 127 and the ball and ramp mechanism 127 having high mechanical efficiency. The pressing force to the disk rotor D can be maintained while ensuring good operating efficiency of 43. Thereby, compared with the ratchet mechanism employ | adopted as the conventional disc brake, the structure can be simplified and the manufacturing efficiency of this disc brake 1 can be improved.

  In the disc brake 1 according to this embodiment, not only the pressing force from the first screw fitting portion 105 and the second screw fitting portion 106 but also the pressing force from the ball and ramp mechanism 127 is applied to the piston 18. Therefore, a desired braking force can be obtained even if the motor 40 is downsized. Further, by reducing the size of the motor 40 (lowering the torque), the rotational torque applied to the spur multi-stage speed reduction mechanism 44 and the planetary gear speed reduction mechanism 45 can be kept low. Can be achieved.

  In the disc brake 1 according to the present embodiment, the lead of the first screw fitting portion 105 is made larger than the lead L when the ball and ramp mechanism 127 and the second screw fitting portion 106 are operated. Thus, it is possible to improve the responsiveness until the clearance is secured when the parking brake is operated.

  In the disc brake 1 according to the present embodiment, at the time of release, the ball and ramp mechanism 127 is returned to the initial position, the ball and ramp mechanism 127 is moved backward, and then the push rod 102 is moved backward to the piston 19. The holding power is released. Therefore, the apply operation can be started immediately even if the apply operation is switched to the apply operation during the release.

  In the disc brake 1 according to the present embodiment, the spur multi-stage reduction mechanism 44 and the planetary gear reduction mechanism 45 are used as the reduction mechanism, but other known reduction mechanisms such as a cycloid reduction gear and a wave reduction gear are used. May be. Further, although the ball 152 is employed as the rolling element of the ball and ramp mechanism 127, a roller and ramp mechanism using a cylindrical member having excellent load resistance may be employed.

  Further, in the present embodiment, the operation of the rotation / linear motion conversion mechanism 43 has been described by taking the parking brake as an example of the operation for maintaining the stop state of the vehicle. However, in the case other than the parking brake, for example, a slope In the case of hill start assist or hill down assist for assisting the start of the vehicle at the time of automatic stop when the vehicle is stopped with the accelerator off, the rotation linear motion conversion mechanism 43 that is a parking brake mechanism is operated. Also good.

  1 Disc brake, 2 Inner brake pad, 3 Outer brake pad, 4 Caliper, 6 Caliper body, 7 Cylinder, 15 Cylinder, 18 Piston, 40 Motor (electric motor), 43 Rotary linear motion conversion mechanism, 75 Base nut (Rotation) Transmission member), 97 female threaded portion, 100 first spring clutch (first one-way clutch), 102 push rod (shaft member), 103 first male threaded portion (first threaded portion), 104 second male threaded portion (Second screw portion), 105 first screw fitting portion, 106 second screw fitting portion, 124 second spring clutch (second one-way clutch) 127 ball and ramp mechanism, 150 fixed ramp, 151 Rotating linear motion lamp, 162 female thread, D disk rotor

Claims (5)

A pair of pads disposed on both sides in the rotor axial direction across the rotor;
One piston for pressing one of the pair of pads against the rotor;
A caliper body having a cylinder in which the piston is movably disposed;
An electric motor provided in the caliper body;
A rotation / linear motion conversion mechanism provided in the caliper body and propelling the piston to hold it in a braking position;
The rotation / linear motion conversion mechanism is:
A rotation transmission member for transmitting rotation of the electric motor;
A shaft member that is screw-fitted to the rotation transmission member and is rotatable and linearly movable;
A ball and ramp mechanism that is screwed into the shaft member and applies axial thrust to the piston by rotation of the shaft member;
The shaft member is formed with a first screw portion that is screw-fitted to the rotation transmission member on one end side, and a second screw portion that is screw-fitted to the ball and ramp mechanism on the other end side,
The disk brake, wherein the rotation resistance torque of the first screw portion is larger than the rotation resistance torque of the second screw portion.   The disc brake according to claim 1, wherein a diameter of the first threaded portion is larger than a diameter of the second threaded portion. The rotation / linear motion conversion mechanism includes a first one-way clutch that applies a rotation resistance torque to rotation in one direction,
3. The disc brake according to claim 1, wherein the first one-way clutch applies a rotational resistance torque to the rotation transmitting member with respect to rotation in a release direction in which the piston of the shaft member moves backward. . The rotation / linear motion conversion mechanism includes a second one-way clutch that applies a rotation resistance torque to rotation in one direction,
4. The disk according to claim 1, wherein the second one-way clutch applies a rotational resistance torque to the piston in rotation in an apply direction in which the shaft member propels the piston. 5. brake.   When the piston is retracted in the release direction, the rotational resistance torque in the screw fitting portion between the shaft member and the ball and ramp mechanism is changed to the rotational resistance torque by the first one-way clutch. 5. The disc brake according to claim 3, wherein the torque is smaller than a rotation resistance torque obtained by adding a rotation resistance torque in a screw fitting portion between the rotation transmission member and the rotation transmission member.