JP2017133584A - Disc brake - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a disc brake that improves a yield in production by decreasing the number of press-fitting processes to a holder of each component.SOLUTION: A support plate 59 of a disc brake 1 includes a hole part 59B for supporting a fitting bolt 218 for holding the support plate 59 on a holder 205, and a hole part 59C for rotatably supporting a non-deceleration spur gear 48 and supporting the other end of a shaft 55, one end of which is fixed to the holder 205. By the hole part 59C of the support plate 59, the rotation around the fitting bolt 218 of the support plate 59 with respect to the holder 205 can be restricted. Thereby, the number of press-fitting processes to the holder 205 of each component can be decreased as compared to a conventional disc brake, and by extension, a yield in production can be improved.SELECTED DRAWING: Figure 4

Description

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

  Some conventional disc brakes include a parking brake mechanism that operates at the time of parking brake, and the parking brake mechanism includes a speed reduction mechanism that increases rotation from a motor, a housing that houses the speed reduction mechanism, A cover member that closes one end opening of the housing, and a shaft that supports each gear of the speed reduction mechanism is supported by the cover member (see Patent Document 1).

  Although not used in the above-described disc brake, a motor and a speed reduction mechanism are assembled to a holder and a support plate to constitute a motor gear assembly, and the motor gear assembly is made of rubber (a vibration absorbing member made of synthetic resin). Some of them are attached to the housing and the cover member in a floating state. By adopting this, vibration generated by the motor and the speed reduction mechanism is suppressed from being transmitted to the housing and the cover member, and further, the assembly accuracy of each gear of the speed reduction mechanism is ensured.

  However, in this disc brake, there is a step of press-fitting and fixing the shaft extending from the speed reduction mechanism to the holder, which increases the dimensional accuracy and assembly accuracy required for each target component, which causes the production yield to deteriorate. It was.

JP 2014-70670 A

  In view of the above-described problems, an object of the present invention is to provide a disc brake that reduces the press-fitting process of each component into a holder and improves the production yield.

  As means for solving the above-described problems, the present invention provides a pair of pads disposed on both sides in the axial direction of the rotor across the rotor, a piston for pressing one of the pair of pads against the rotor, and the piston A caliper main body having a cylinder movably accommodated therein, a motor provided in the caliper main body, a speed reduction mechanism including a plurality of gears for increasing the rotation from the motor, a housing for accommodating the speed reduction mechanism, A support plate disposed in the housing and supporting the gears, a holder disposed in the housing and supporting the support plate, and provided in the cylinder, and propelling the piston by rotation from the speed reduction mechanism And a rotation / linear motion converting mechanism that holds the brake plate in a braking position, and the support plate is provided on the holder. A shaft that is coupled to the columnar support and defines a distance from the holder; and a shaft that rotatably supports one of the plurality of gears and has one end fixed to the holder. A second shaft supporting portion that supports the other end, and the second shaft supporting portion restricts rotation of the support plate relative to the holder around the columnar support portion.

  According to the disc brake of the present invention, it is possible to reduce the press-fitting process of each component into the holder and improve the production yield.

Sectional drawing which shows the disc brake which concerns on this embodiment. The exploded perspective view in the housing of this disc brake. The exploded perspective view in the housing of this disc brake. The top view in the housing of this disc brake. The expanded sectional view of the rotation linear motion conversion mechanism of this disc brake. FIG. 3 is an exploded perspective view of a rotation / linear motion conversion mechanism of the disc brake.

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. In the following description, for convenience of explanation, the right side in FIG. 1 will be described as one end side and the left side as the other end side as appropriate.

  As shown in FIG. 1, the caliper body 6 that is the main body of the caliper 4 opposes the cylinder portion 7 disposed on the base end side facing the inner brake pad 2 on the vehicle inner side and the outer brake pad 3 on the vehicle outer side. And a claw portion 8 disposed on the distal end side. 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. On the bottom wall 11 side in the cylinder 15, a small-diameter opening 9B that is continuous with the large-diameter opening 9A and has 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.

  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 (see FIGS. 5 and 6) are formed on the inner peripheral surface of the piston 18 along the circumferential direction. 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. By this engagement, the piston 18 is restricted so as not to rotate relative to the cylinder 15 and, consequently, the caliper body 6. In addition, a dust boot 27 is interposed between the outer peripheral surface on the bottom 19 side 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. Yes.

  As shown in FIGS. 1 to 3, a housing 30 in which a motor gear assembly 29 is housed is attached to the bottom wall 11 side of the cylinder 15 of the caliper body 6. The configuration of the motor gear assembly 29 will be described later. An opening 30 </ b> A is provided at one end of the housing 30. A cover member 36 that is airtightly closed is attached to the opening 30A. In other words, the opening 30 </ b> A of the housing 30 is closed by the cover member 36. A seal member 37 is provided between the housing 30 and the cylinder portion 7. The inside of the housing 30 is kept airtight by the seal member 37.

  The housing 30 is integrally formed from a first housing part 31 and a first housing part 31 that accommodates a spur multi-stage reduction mechanism 44 and a planetary gear reduction mechanism 45 described later so as to cover the outer periphery of the bottom wall 11 of the cylinder 15. And a second housing portion 32 that houses the motor 200. As described above, the housing 30 is configured to accommodate the motor 200 arranged in line with the caliper body 6 by the bottomed cylindrical second housing portion 32. The first housing portion 31 includes an outer wall portion 31F and a bottom surface portion 31G that surround a housing chamber 31E that houses a later-described spur multi-stage reduction mechanism 44 and a planetary gear reduction mechanism 45 together with a cover member 36, and one of the bottom walls 11 of the cylinder 15. A mounting opening 31A through which a polygonal shaft portion 81 of a base nut 75 of the rotation / linear motion conversion mechanism 43, which will be described later, is inserted, and an inner annular wall portion 31B protruding around the mounting opening 31A, An outer annular wall portion 31C that projects radially outward from the inner annular wall portion 31B, and a plurality of engagement grooves 31D that are formed at intervals in the circumferential direction of the outer annular wall portion 31C. have.

  As shown in FIG. 1, the caliper body 6 includes a spur multi-stage reduction mechanism 44 and a planetary gear reduction mechanism 45 that reinforces the driving force of the motor 200, and a rotation that propels the piston 18 and holds the piston 18 in the braking position. A linear motion conversion mechanism 43 is provided. The spur multi-stage reduction mechanism 44 and the planetary gear reduction mechanism 45 are accommodated in an accommodation chamber 31 </ b> E that is in the first housing portion 31 of the housing 30.

As shown in FIGS. 1 to 3, the spur multi-stage reduction mechanism 44 includes a pinion gear 46, a first reduction gear 47, a non-reduction spur gear 48, and a second reduction gear 49. The first reduction gear 47, the non-reduction spur gear 48, and the second reduction gear 49 are made of resin such as fiber reinforced resin.
The pinion gear 46 is formed in a cylindrical shape, and has a hole 50 that is press-fitted and fixed to the rotating shaft 201 of the motor 200, and a gear 51 that is formed on the outer periphery. 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. . A shaft 52 is integrally fixed to the first reduction gear 47. One end of the shaft 52 is rotatably supported by a hole 59D of a support plate 59 provided close to the inner surface of the cover member 36, and the other end is rotatably supported by a holder 205. The configuration of the holder 205 will be described in detail later.

  The small gear 54 of the first reduction gear 47 meshes with the non-reduction spur gear 48. The non-reducing spur gear 48 is rotatably supported by the shaft 55. One end of the shaft 55 is rotatably supported by the hole 59 </ b> C of the support plate 59, and the other end is integrally fixed to the holder 205. The shaft 55 is integrally fixed to the holder 205 by insert molding. The second reduction gear 49 includes a large-diameter large gear 56 that meshes with the non-reducing spur gear 48 and a small-diameter sun gear 57 that extends from the large gear 56 in the axial direction. The The sun gear 57 is configured as a part of a planetary gear reduction mechanism 45 described later. One end of the shaft 58 is press-fitted and fixed in the hole 59 </ b> A of the support plate 59. The second reduction gear 49 is rotatably supported by the shaft 58. Further, a stopper portion 56A that protrudes toward the planetary gear reduction mechanism 45 extends in an annular shape on the annular wall portion of the large gear 56 of the second reduction gear 49.

  As shown in FIGS. 1, 2, and 4, the support plate 59 is supported by a holder 205 described later in the vicinity of the inner surface of the cover member 36. The support plate 59 includes a hole portion 59A for the shaft 58 that rotatably supports the second reduction gear 49, and a hole for the mounting bolt 218 for supporting the support plate 59 on a cylindrical support portion 217 of the holder 205 described later. And a hole 59C for the shaft 55 that rotatably supports the non-reducing spur gear 48, and a hole 59D for the shaft 52 that rotatably supports the first reduction gear 47. The hole 59B of the support plate 59 corresponds to the first shaft support, and the hole 59C corresponds to the second shaft support.

  As shown in FIGS. 2 and 4, the support plate 59 has a substantially L shape, and extends linearly with a predetermined width from the hole portion 59 </ b> A for the shaft 58 toward the hole portion 59 </ b> B for the mounting bolt 218. A first plate portion 70A, and a second plate portion 70B that is integrally connected to the first plate 59A and extends linearly from the hole portion 59D for the shaft 52 toward the hole portion 59 for the shaft 55 with a predetermined width. Consists of The first plate portion 70 </ b> A extends from the radial center of the second reduction gear 49 toward one end in the short direction of the cover member 36 on the motor 200 side. On the other hand, the second plate portion 70 </ b> B extends along the short direction of the cover member 36. The first plate portion 70A is formed longer than the second plate portion 70B.

  As shown in FIGS. 1 to 3, the planetary gear reduction mechanism 45 includes a sun gear 57 of the second reduction gear 49, a plurality (four in this embodiment) of planetary gears 60, an internal gear 61, and a carrier 62. And have. Each planetary gear 60 has a gear 63 meshed with the sun gear 57 of the second reduction gear 49 and a hole 64 through which a pin 65 erected from the carrier 62 is rotatably inserted. The planetary gears 60 are arranged at equal intervals on the circumference of the carrier 62. An annular plate 66 is disposed on the other end side of each planetary gear 60.

  The carrier 62 is formed in a disk shape, and a polygonal hole 68 is formed at the substantially radial center. The outer diameter of the carrier 62 is substantially the same as the outer diameter of the revolution trajectory of each planetary gear 60. A plurality of pin holes 69 are formed on the outer peripheral side of the carrier 62 at intervals along the circumferential direction. A pin 65 is press-fitted and fixed in each pin hole 69. Each pin 65 is rotatably inserted into a hole 64 of each planetary gear 60. The carrier 62 and the base nut 75 transmit rotational torque to each other by fitting the polygonal hole 68 of the carrier 62 and the polygonal shaft portion 81 of the base nut 75 of the rotation / linear motion converting mechanism 43 described later. It can be done.

  The internal gear 61 continuously extends in the radial direction from one end on the cover member 36 side of the inner teeth 71 with which the gear 63 of each planetary gear 60 is meshed, and moves in the axial direction of each planetary gear 60. An annular wall portion 72 to be regulated and a cylindrical wall portion 73 extending from the inner teeth 71 toward the bottom wall 11 of the cylinder 15 are provided. The internal gear 61 is fixed to the housing 30 by inserting the cylindrical wall portion 73 into the annular space between the inner annular wall portion 31B and the outer annular wall portion 31C of the first housing portion 31. An annular plate 66 is disposed in the internal gear 61. The annular plate 66 is sandwiched between the end surface of the internal teeth 71 of the internal gear 61 and the inner annular wall portion 31 </ b> B of the first housing portion 31. Thereby, each planetary gear 60 is arrange | positioned between the annular wall part 72 and the annular plate 66 of the internal gear 61, and the movement of an axial direction is controlled.

  In addition, a plurality of protrusions 74 are provided on the other end side of the outer peripheral surface of the internal gear 61 so as to be spaced apart in the circumferential direction. Each protrusion 74 protrudes outward and is engaged with each engagement groove 31 </ b> D provided in the first housing portion 31. The internal gear 61 is supported in the first housing portion 31 so as not to rotate by inserting and engaging the protrusions 74 with the engaging grooves 31 </ b> D of the first housing portion 31. Further, the internal gear 61 is moved in the axial direction because an annular stopper portion 56A provided on the large gear 56 of the second reduction gear 49 is disposed on the cover member 36 side of the annular wall portion 72. It is impossiblely supported in the first housing part 31.

  As shown in FIGS. 2 and 3, the motor 200 is supported by a holder 205 arranged on the flange portion 202. The holder 205 is configured by integrally connecting a motor support portion 206 and a ring-shaped support portion 207. The motor support portion 206 is arranged between the first reduction gear 47 and the non-reduction spur gear 48 and the flange portion 202 of the motor 200 to support the motor 200. The ring-shaped support portion 207 is disposed around the internal gear 61 of the planetary gear reduction mechanism 45 so as to surround the internal gear 61. The motor support portion 206 is formed with a rotation shaft insertion hole 208 through which the pinion gear 46 press-fitted and fixed to the rotation shaft 201 of the motor 200 is inserted. Around the rotating shaft insertion hole 208, two terminal insertion holes through which the motor terminals 203 of the motor 200 are inserted are formed. A pair of terminal insertion holes is formed on both sides in the radial direction of the rotation shaft insertion hole 208. Harnesses 250 and 251 are connected to the motor terminals 203 of the motor 200, respectively.

  The motor support portion 206 of the holder 205 includes a holder-side first convex portion 211, a holder-side second convex portion 212, and a holder-side first portion on the opposite side of the planetary gear speed reduction mechanism 45 around the rotation shaft insertion hole 208. Three convex portions 213 are formed at intervals from each other. The holder-side first convex portion 211, the holder-side second convex portion 212, and the holder-side third convex portion 213 are columnar and project toward the cover member 36 side. Two fastening holes 216 are formed in the motor support portion 206. Each mounting bolt 215 is fastened to the fastening hole 216 of the motor support portion 206 via each through hole 202 </ b> A of the flange portion 202 of the motor 200. By this fastening, the motor 200 is supported by the motor support part 206 of the holder 205. The ring-shaped support portion 207 is disposed above each protrusion 74 so as to contact the outer peripheral surface of the internal gear 61 of the planetary gear reduction mechanism 45.

  The holder 205 is provided with a cylindrical support portion 217 at a position between the motor support portion 206 and the ring-shaped support portion 207 by insert molding. The support plate 59 is disposed on the cylindrical support portion 217, and the mounting bolt 218 is fastened to the cylindrical support portion 217 of the holder 205 through the hole portion 59 </ b> B of the support plate 59. Further, the shaft 55 extending integrally from the holder 205 is inserted through the hole 59 </ b> C of the support plate 59 via the non-reducing spur gear 48. As a result, the support plate 59 is supported by the cylindrical support portion 217, and as a result, is supported on the holder 205 at an interval. The support plate 59 is restricted from moving along the axial direction of the first reduction gear 47, the non-reduction spur gear 48, and the like by the cylindrical support portion 217 and the mounting bolt 218. However, the rotation of the support plate 59 relative to the holder 205 around the mounting bolt 218 can be restricted. In other words, relative rotation of the support plate 59 with respect to the holder 205 around the mounting bolt 218 or the shaft 55 can be restricted by the mounting bolt 218 and the shaft 55.

  As shown in FIGS. 1 to 3, the cover member 36 is made of a synthetic resin and is formed so as to close the one end opening 30 </ b> A of the housing 30. The cover member 36 is provided with a cover-side first cylindrical portion 221, a cover-side second convex portion 222, and a cover-side third convex portion 223 that protrude from each other at intervals. The cover-side first cylindrical portion 221, the cover-side second convex portion 222, and the cover-side third convex portion 223 are a holder-side first convex portion 211, a holder-side second convex portion 212, and a holder-side provided on the holder 205. Each is formed at a position facing the third convex portion 213.

  The cover side first cylindrical portion 221, the cover side second convex portion 222 and the cover side third convex portion 223 of the cover member 36, and the holder side first convex portion 211 and the holder side second convex portion 212 of the holder 205. And the rubber 230 which is an elastic member is interposed between the holder side 3rd convex part 213. FIG. The rubber 230 is formed by integrating the first cup portion 231, the second cup portion 232, the third cup portion 233, and the opening side end portions of the first cup portion 231, the second cup portion 232, and the third cup portion 233. And a plate-like base portion 234 connected to each other.

  Then, the first cup portion 231 of the rubber 230 is fitted to the holder-side first convex portion 211 of the holder 205, the second cup portion 232 of the rubber 230 is fitted to the holder-side second convex portion 212 of the holder 205, The third cup portion 233 of the rubber 230 is fitted to the holder-side third convex portion 213 of the holder 205 so that the rubber 230 is unitized with the holder 205. Thereafter, the cover side first cylindrical portion 221 of the cover member 36 is fitted into the first cup portion 231 of the rubber 230, and the cover side second convex portion 222 of the cover member 36 is fitted to the second cup of the rubber 230. The cover member 36 is covered so that the cover-side third convex portion 223 of the cover member 36 is in contact with the third cup portion 233 of the rubber 230. Harnesses 250 and 251 extending from the motor terminals 203 of the motor 200 are arranged along the base portion 234 of the rubber 230.

  As shown in FIG. 2, in this embodiment, a plurality of types of rubbers 281, 282, and 283 different from the rubber 230 described above are provided in the housing 30. A U-shaped support section 280 is formed at the end of the holder 205 on the motor support section 206 side, and a U-shaped rubber section 281 is integrally disposed therein. Block-shaped rubbers 282 are respectively disposed between the outer peripheral surface at a position close to each cylindrical support portion 217 and the inner wall surface of the first housing portion 31 in the ring-shaped support portion 207 of the holder 205. A cylindrical rubber 283 is disposed between the main body side end portion of the motor 200 and the bottom wall portion of the second housing portion 32.

  Thus, the motor gear assembly 29 is configured by assembling the motor 200, the spur multi-stage reduction mechanism 44, the planetary gear reduction mechanism 45, and the rubbers 230, 281, 282, and 283 to the holder 205 and the support plate 59. The motor gear assembly 29 is attached to the housing 30 and the cover member 36 by rubbers 230, 281, 282, and 283 in a suspended state, that is, a so-called floating state. In other words, the motor gear assembly 29 is fixed to the housing 30 and the cover member 36 via the rubbers 230, 281, 282, and 283 without the holder 205 coming into contact with the housing 30 and the cover member 36. As described above, the motor gear assembly 29 is fixed to the housing 30 and the cover member 36 via the rubbers 230, 281, 282, and 283, so that the motor 200, the spur multi-stage reduction mechanism 44, and the planetary gear reduction mechanism 45 are used. Transmission of the generated vibration to the housing 30 or the cover member 36 is suppressed, and generation of sound accompanying the vibration can be suppressed.

  In the present embodiment, in order to obtain the rotational force for propelling the piston 25, the spur multi-stage reduction mechanism 44 and the planetary gear reduction mechanism 45 as the reduction mechanism that reinforces the driving force by the motor 200 are employed. You may comprise only the deceleration mechanism 45. FIG. Further, a speed reducer according to another known technique such as a cycloid speed reduction mechanism or a wave speed reducer may be combined with the planetary gear speed reduction mechanism 45.

Next, the rotation / linear motion conversion mechanism 43 will be specifically described with reference to FIGS. 1, 5, and 6. In the following description, for convenience of explanation, the right side of FIGS. 1 and 5 will be described as one end side and the left side will be appropriately described as the other end side.
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 200 into motion in a linear direction (hereinafter referred to as linear motion for convenience), and the piston 18. A thrust is applied to the piston 18 to hold the piston 18 in the braking position. The rotation / linear motion converting mechanism 43 includes a base nut 75 that is rotatably supported by the rotational motion transmitted from the spur multi-stage speed reduction mechanism 44 and the planetary gear speed reduction mechanism 45, and a female screw portion 97 of the base nut 75. A push rod 102 that is fitted and rotatably supported by the rotation of the base nut 75, and is screwed to the push rod 102, and is axially moved to the piston 18 by the rotation of the push rod 102. And a ball-and-ramp mechanism 127 that applies thrust. The rotation / linear motion conversion mechanism 43 is accommodated between the cylinder 15 and the piston 18 of the caliper body 6.

  As shown in FIGS. 5 and 6, the base nut 75 includes 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 so as to contact 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 shaft portion 81 is integrally connected to the tip of the cylindrical portion 76. The polygon shaft 81 is inserted through the attachment opening 31 </ b> A of the first housing portion 31 and is fitted into the polygon hole 68 of the carrier 62. The nut portion 77 of the base nut 75 is formed in a bottomed cylindrical shape. The nut portion 77 includes a circular wall portion 82 and a cylindrical portion 83 projecting integrally from the other end surface of the circular wall portion 82. The outer peripheral surface of the circular wall portion 82 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 the radial center of one end face of the circular wall 82. A cylindrical portion 76 projects from one end surface of the small-diameter circular wall portion 84 toward one end side. 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 washer 80 and the circular wall portion 82 around the small-diameter circular wall portion 84 provided in 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. Thereby, the fluid tightness of the hydraulic chamber 21 is maintained. A retaining ring 90 is mounted in an annular groove provided between the cylindrical portion 76 of the base nut 75 and the polygonal shaft portion 81. By the retaining ring 90, the base nut 75 is restricted from moving in the axial direction.

  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. One end of the large-diameter cylindrical portion 91 is integrally connected to the circular wall portion 82. A plurality of through holes 95 extending in the radial direction are formed in the peripheral wall portion of the large diameter cylindrical portion 91. A plurality of through holes 95 are formed at intervals in the circumferential direction. A female thread portion 97 is formed on the inner peripheral surface of the small diameter cylindrical portion 92 of the nut portion 77. A plurality of locking grooves 98 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. In the present embodiment, four locking grooves 98 are formed.

  One of the locking grooves 98 of the small-diameter cylindrical portion 92 of the base nut 75 is fitted with a distal end portion 100A of the first spring clutch 100 as a one-way clutch that applies rotational resistance to rotation in one direction. The The first spring clutch 100 includes a distal end portion 100A facing outward in the radial direction and a coil portion 100B wound continuously from the distal end portion 100 in a single layer. Then, the distal end portion 100 </ b> A of the first spring clutch 100 is fitted into one of the locking grooves 98 of the small diameter cylindrical portion 92 of the base nut 75. The coil portion 100B of the first spring clutch 100 is wound around a screw groove on the other end side of the male screw portion 103 of the push rod 102, which will be described in detail later. The first spring clutch 100 applies a rotational resistance torque in the rotational direction (the rotational direction at the time of release) when the push rod 102 moves toward the bottom wall 11 side of the cylinder 15 with respect to the base nut 75. The push rod 102 is configured to allow rotation in the rotation direction (rotation direction at the time of application) when the push rod 102 moves to the bottom 19 side of the piston 18 with respect to the base nut 75.

  One end side of the push rod 102 is inserted into the nut portion 77 of the base nut 75. On one end side of the push rod 102, a male screw portion 103 that is screwed into the female screw portion 97 of the small diameter cylindrical portion 92 of the base nut 75 is formed. The first screw fitting portion 105 between the male screw portion 103 of the push rod 102 and the female screw portion 97 of the small-diameter cylindrical portion 92 of the base nut 75 causes the base nut to move in the axial direction from the piston 18 to the push rod 102. In order not to rotate 75, the reverse efficiency is set to 0 or less, that is, it is configured as a screw fitting portion having a large irreversibility. Further, the coil portion 103 </ b> A of the first spring clutch 100 is wound around the thread groove of the male screw portion 103 on the other end side from the first screw fitting portion 105 of the push rod 102 with the base nut 75.

  On the other hand, on the other end side of the push rod 102, a male screw portion 104 that is screw-fitted to a female screw portion 162 provided on a rotary linear motion lamp 151 of a ball and ramp mechanism 127 described later is formed. Here again, the second screw fitting portion 106 between the male threaded portion 104 of the push rod 102 and the female threaded portion 162 provided on the rotary linear motion ramp 151 is used for the axial load from the piston 18 to the rotational linear motion ramp 151. In order to prevent the push rod 102 from rotating, the reverse efficiency of the push rod 102 becomes 0 or less, that is, the screw fitting portion has a large irreversibility.

  The push rod 102 is provided with a spline shaft 108 between a male screw portion 103 on one end side and a male screw portion 104 on the other end side. The outer diameter of the male screw portion 103 on one end side is formed larger than the outer diameter of the male screw portion 104 on the other end side. The outer diameter of the male screw portion 103 on one end side is formed larger than the outer diameter of the spline shaft 108. A small-diameter cylindrical portion 107 is continuously formed on the other end side from the male screw portion 104 of the push rod 102. The outer peripheral surface of the cylindrical portion 107 is knurled. A stopper member 172 is integrally fixed to the cylindrical portion 107 of the push rod 102 by press-fitting. The stopper member 172 defines a relative rotation range of the rotary linear movement lamp 151 with respect to the push rod 102. The other end surface of the cylindrical portion 107 of the push rod 102 faces the bottom portion 19 of the piston 18.

  The retainer 110 is supported between the outer peripheral surface of the small diameter cylindrical portion 92 of the cylindrical portion 84 constituting the nut portion 77 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, and is configured in a substantially cylindrical shape as a whole. A plurality of through holes 114 and 115 are formed in the outer peripheral wall of the retainer 110.

  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.

  A coil spring 121 is interposed between the one end side washer 120 and the other end side washer 122. The coil spring 121 urges the one end side washer 120 and the other end side washer 122 in a direction to separate them. A plurality of 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. Each locking groove 132 includes a narrow locking groove 133 positioned on one end side and a wide locking groove 134 positioned on the other end side. The locking groove 132 is formed in three places in this embodiment. At the other end of the retainer 110, a plurality of claw portions 136 are formed toward the bottom portion 19 of the piston 18. Inside the retainer 110, 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 mechanism 127, thrust bearing 128, and annular pressure After the plate 129 is accommodated, the claws 136 of the retainer 110 are folded toward the accommodating recess 171 of the annular pressing plate 129, which will be described later, so that a large number of the above-described constituent members are integrally disposed in the retainer 110. Can be assembled.

  An annular support plate 123 is disposed so as to contact the other end surface of the other end washer 122. A plurality of protruding pieces 137 are provided on the outer peripheral surface of the support plate 123 at intervals along the circumferential direction. In the present embodiment, three protrusion pieces 137 are formed. The protrusions 137 of the support plate 123 are fitted into the narrow locking grooves 133 of the retainer 110 and the rotation restricting vertical grooves 22 provided on the inner peripheral surface of the piston 18, respectively. As a result, the retainer 110 is supported together with the one end side washer 120, the coil spring 121, the other end side washer 122, and the support plate 123 so as not to rotate relative to the piston 18 and to be relatively movable in the axial direction.

  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 brought into contact with the other end surface of the support plate 123. The push rod 102 is inserted into the rotating member 125, and the spline hole 140 of the large-diameter annular portion 141 of the rotating member 125 and the spline shaft 108 of the push rod 102 are splined. As a result, the rotating member 125 and the push rod 102 can transmit mutual rotational torque.

  A second spring clutch 124 that imparts rotational resistance to rotation in one direction is wound around the outer peripheral surface of the small-diameter cylindrical portion 142 of the rotating member 125. Similar to the first spring clutch 100, the second spring clutch 124 includes a distal end portion 124A facing outward in the radial direction and a coil portion 124B continuously wound from the distal end portion 124A. . Then, the distal end portion 124 </ b> A of the second spring clutch 124 is fitted into one of the narrow locking grooves 133 of the retainer 110, and the coil portion 124 </ b> B is wound around 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 rotating 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 rotation direction (rotation direction at release) when moving to the bottom wall 11 side of the cylinder 15.

  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 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.

  The ball-and-ramp mechanism 127 includes a fixed lamp 150, a rotation / linear motion lamp 151, and each ball 152 interposed between the fixed lamp 150 and the rotation / linear motion lamp 151. The fixed lamp 150 is disposed on the other end side of the rotating member 125 via a thrust bearing 126. The fixed lamp 150 includes a disk-shaped fixed plate 154 and a plurality of convex portions 155 that protrude from the outer peripheral surface of the fixed plate 154 at intervals along the circumferential direction. In the present embodiment, three convex portions 155 are formed. An insertion hole 156 through which the push rod 102 is inserted is formed at the center in the radial direction of the fixed plate 154. The fixed ramp 150 has its convex portions 155 fitted into the wide locking grooves 134 of the retainer 110 and fitted into the rotation restricting vertical grooves 22 provided on the inner peripheral surface of the piston 18. The piston 18 is supported so as not to rotate relative to the piston 18 and to be movable in the axial direction. On the other end surface of the fixed plate 154, a plurality of ball grooves 157 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 are formed in the present embodiment. ing.

  The rotation / linear motion ramp 151 includes an annular rotation / linear motion plate 160 and a cylindrical portion 161 that protrudes integrally from a central portion in the radial direction 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 male screw portion 104 of the push rod 102 is screwed is formed. On the surface of the rotary linear motion plate 160 facing the fixed plate 154 of the fixed lamp 150, a plurality of books 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 In the embodiment, three ball grooves 163 are formed. In addition, each ball groove 157 of the fixed ramp 150 and each ball groove 163 of the rotary linear motion ramp 151 may be configured by forming a recess in the middle of the inclination along the circumferential direction or changing the inclination in the middle. good.

  As shown in FIGS. 5 and 6, the ball 152 is interposed between each ball groove 163 of the rotation linear movement ramp 151 (rotation linear movement plate 160) and each ball groove 157 of the fixed ramp 150 (fixation plate 154). It is intervened. Then, when a rotational torque is applied to the rotation / linear motion ramp 151, each ball 152 between each ball groove 163 of the rotation / linear motion plate 160 and each ball groove 157 of the fixed plate 154 rolls. Due to the rotational difference between the plate 160 and the fixed plate 154, the relative distance in the axial direction between the rotary translation plate 160 and the fixed plate 154 varies.

  An annular pressing plate 129 is disposed on the other end surface around the cylindrical portion 161 of the rotary translation plate 160 via a thrust bearing 128. On the outer peripheral surface of the annular pressing plate 129, a plurality of convex portions 168 are provided protruding at intervals along the circumferential direction. In the present embodiment, three convex portions 168 are formed. Each of the convex portions 168 of the annular pressing plate 129 is fitted into each of the wide locking grooves 134 of the retainer 110 and is fitted into each of the rotation restricting vertical grooves 22 provided on the inner peripheral surface of the piston 18. The piston 18 is supported so as not to rotate relative to the piston 18 and to be movable in the axial direction.

  The rotation / linear motion ramp 151 of the ball and ramp mechanism 127 is supported by an annular pressing plate 129 through a thrust bearing 128 so as to be rotatable. The other end surface of the annular pressing plate 129 comes into contact with the bottom portion 19 of the piston 18 to 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.

  Further, as shown in FIG. 1, the motor 200 is electrically connected to an ECU 175 composed of an electronic control unit that drives and controls the motor 200. The ECU 175 is connected to a parking switch 176 that is operated to instruct the operation / release of the parking brake. Further, the ECU 175 can be operated regardless of the operation of the 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 operating 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). Thereby, the piston 18 moves forward (moves leftward in FIG. 1) from the original position during non-braking while elastically deforming the piston seal 16, and presses the inner brake pad 2 against the disc rotor D. 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. As a result, 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, 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 this slip, the original position of the piston 18 with respect to the caliper body 6 is moved, and the pad clearance is adjusted to be constant.

Next, an operation as a parking brake, which is an example of an operation for maintaining the stopped state of the vehicle, will be described.
First, when the parking switch is operated from the parking brake released state and the parking brake is operated (applied), the ECU 175 drives the motor 200 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 is transmitted to the base nut 75.

  Next, the rotational resistance torque in the apply direction of the rotating member 125 (push rod 102) to the retainer 110 (piston 18) by the second spring clutch 124 causes the first screw fit between the push rod 102 and the base nut 75. It is set to be larger than the rotational resistance torque by the joint portion 105. Accordingly, the first spring clutch 100 is allowed to rotate the push rod 102 in the apply direction with respect to the base nut 75. Therefore, the rotation of the base nut 75 in the apply direction causes the first screw fitting portion 105 to rotate relatively, that is, only the base nut 75 rotates in the apply direction, while the push rod 102 extends along the axial direction. The piston 18 moves forward toward the bottom 19 side.

  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 moved toward the bottom 19 side of the piston 18 along the axial direction. By advancement of these components, the annular pressing plate 129 comes into contact with the bottom portion 19 of the piston 18, and the piston 18 advances and one end surface of the bottom portion 19 of the piston 18 comes into contact with the inner brake pad 2.

  When the rotation of the motor 200 in the apply direction is continued, the piston 18 starts to press the disc rotor D via the inner and outer brake pads 2 and 3 by the movement of the push rod 102. When this pressing force starts to be generated, this time, the rotational resistance torque in the first screw fitting portion 105 between the push rod 102 and the base nut 75 increases due to the axial force that is the reaction force against the pressing force. Thus, the rotational resistance torque of the second spring clutch 124 becomes larger. As a result, the push rod 102 starts to rotate in the apply direction together with the rotating member 125 as the base nut 75 rotates. Then, due to the reaction force from the pressing force of the disk rotor D, the rotational resistance torque in the second screw fitting portion 106 between the push rod 102 and the ball and ramp mechanism 127 also increases due to the reaction force of the pressing force of the disk rotor D. For this reason, the rotational torque in the apply direction of the push rod 102 is transmitted to the rotary linear motion lamp 151 of the ball and ramp mechanism 127 via the second screw fitting portion 106.

  At this time, the rotational torque in the apply direction of the push rod 102 causes a relative rotation difference (the rotation linear motion lamp 151 rotates slightly behind the push rod 102) at the second screw fitting portion 106. Then, it is transmitted to the rotation / linear motion lamp 151 of the ball and ramp mechanism 127. Then, each of the balls 152 rolls while the rotary linear motion lamp 151 of the ball and ramp mechanism 127 rotates in the apply direction, and the rotary linear motion ramp 151 and the fixed ramp 150 resist the urging force of the coil spring 121. Then, the annular pressing plate 129 further presses the bottom portion 19 of the piston 18 by being separated. As a result, the pressing force of the disc rotor D by the inner and outer brake pads 2 and 3 increases.

  In the disc brake 1 according to the present embodiment, first, the first screw fitting portion 105 between the push rod 102 and the base nut 75 relatively rotates, the push rod 102 moves forward, and the piston 18 is moved. Advancing to obtain a pressing force to the disk rotor D. For this reason, the operation of the first screw fitting portion 105 can adjust the original position of the push rod 102 with respect to the piston 18 that changes due to the wear of the inner and outer brake pads 2 and 3 with time.

  The ECU 175 drives the motor 200 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 200 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 200 has reached a predetermined value, the ECU 175 stops energization of the motor 200. Then, the linear motion accompanying the rotation of the rotary linear motion lamp 151 of the ball and ramp mechanism 127 is stopped.

  Eventually, the reaction force of the pressing force from the disk rotor D acts on the rotary linear motion lamp 151, but the second screw fitting portion 106 between the push rod 102 and the ball and ramp mechanism 127 is The first screw fitting portion 105 between the push rod 102 and the base nut 75 is also constituted by a screw fitting portion that does not reversely operate. Since the first spring clutch 100 applies a rotational resistance torque in the release direction to the push rod 102 with respect to the base nut 75, 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.

  Next, when the parking brake is released (released), the motor 200 is rotationally driven in the release direction for separating the piston 18 from the disk rotor D by the ECU 175 based on the parking release operation of the parking switch 176. Thereby, the spur multi-stage reduction mechanism 44 and the planetary gear reduction mechanism 45 are driven to rotate in the release direction for returning the piston 18, and the rotation drive in the release direction is transmitted to the base nut 75 via the carrier 62.

  At this time, the reaction force of the pressing force from the disk rotor D acts on the push rod 102. In other words, the push rod 102 has a second force between the push rod 102 and the ball and ramp mechanism 127. The rotation resistance torque of the screw fitting portion 106, the rotation resistance torque of the first screw fitting portion 105 between the push rod 102 and the base nut 75, and the base nut 75 of the push rod 102 by the first spring clutch 100. And a rotational resistance torque in the release direction with respect to. For this reason, 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 also to the rotary linear motion lamp 151 of the ball and ramp mechanism 127. 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.

  Next, the reaction force to the push rod 102 is reduced, and the rotation resistance torque of the second screw fitting portion 106 between the push rod 102 and the ball and ramp mechanism 127 becomes the base nut by the first spring clutch 100. The rotational resistance torque in the release direction of the push rod 102 with respect to 75 is added to the rotational resistance torque of the first screw fitting portion 105 between the push rod 102 and the base nut 75, so that the rotational resistance becomes smaller. Since the dynamic ramp 151 can no longer rotate in the release direction, only the second screw fitting portion 106 relatively rotates, and the rotary linear motion ramp 151 of the ball and ramp mechanism 127 along with the retainer 110 along the axial direction. Then, it moves to the bottom wall 11 side (release direction) of the cylinder 15 and returns to the initial position in the axial direction.

  Further, when the motor 200 is driven to rotate in the release direction and the rotation of the base nut 75 continues in the release direction, the rotation linear motion lamp 151 of the ball and ramp mechanism 127 returns to the initial position in the axial direction, and the push rod The second screw fitting portion 106 between the ball 102 and the ball and ramp mechanism 127 returns to the initial screwing position, and the rotation of the push rod 102 in the release direction is stopped.

  When the rotation of the base nut 75 is further continued, the push rod 102 moves in the axial direction against the 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. Along the bottom wall 11 side (release direction) of the cylinder 15. 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 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.

  By the way, in the conventional disc brake, the cylindrical support portions 217 and 217 are fixed to the holder 205 at two positions at intervals, and the two mounting bolts 218 and 218 are the hole portions of the support plate 59. The support plate 59 is supported on the holder 205 at intervals by being fastened to the cylindrical support portions 217 and 217 of the holder 205 via 59B and 59B. The support plate 59 is restricted from moving along the axial direction of the first reduction gear 47, the non-reduction spur gear 48, and the like by the cylindrical support portions 217 and the mounting bolts 218. The relative rotation around each of the mounting bolts 218 and 218 is restricted. Further, in the conventional disc brake, the shaft 55 that rotatably supports the non-reducing spur gear 48 is press-fitted and fixed to the holder 205.

  On the other hand, in the disc brake 1 according to the present embodiment, as described above, the mounting bolt 218 is fastened to the cylindrical support portion 217 insert-molded in the holder 205 through the hole portion 59B of the support plate 59, The shaft 55 insert-molded in the holder 205 is inserted into the hole 59C of the support plate 59 via the non-reducing spur gear 48, and the support plate 59 is supported on the holder 205 with a space. The support plate 59 is restricted from moving along the axial direction of the first reduction gear 47 and the non-reduction spur gear 48 by the cylindrical support portion 217 and the mounting bolt 218, and the hole portion 59 </ b> C of the support plate 59 is also provided. However, the rotation of the support plate 59 relative to the holder 205 around the mounting bolt 218 can be restricted.

  Thereby, in the disc brake 1 according to the present embodiment, the press-fitting process of the shaft 55 into the holder 205 is reduced as compared with the conventional disc brake, and as a result, dimensional accuracy and assembly accuracy for each target component are required. Since the press-fitting process to be performed is reduced, the production yield can be improved. Furthermore, the number of steps required for the press-fitting process can be reduced, leading to cost reduction. Further, in the disc brake 1 according to the present embodiment, one of the two cylindrical support portions 217 and 217 conventionally fixed to the holder 205 by insert molding is shared with the shaft 55, and the support plate 59 is further provided. Can be made smaller than the conventional support plate 59 formed in a substantially pentagonal shape in plan view, so that the motor gear assembly 29 as a whole can be reduced. The entire disc brake 1 can be reduced in weight.

  DESCRIPTION OF SYMBOLS 1 Disc brake, 2 Inner brake pad, 3 Outer brake pad, 4 Caliper, 6 Caliper main body, 7 Cylinder part, 15 cylinder, 18 piston, 30 Housing, 59 Support plate, 43 Rotation linear motion conversion mechanism, 44 Flat-tooth multistage deceleration Mechanism, 45 planetary gear reduction mechanism, 55 shaft, 59 support plate, 59B hole (first shaft support), 59C hole (second shaft support), 200 motor, 205 holder, 218 mounting bolt, D disk rotor

Claims (2)

A pair of pads disposed on both axial sides of the rotor across the rotor;
A piston that presses one of the pair of pads against the rotor;
A caliper body having a cylinder in which the piston is movably housed;
A motor provided in the caliper body;
A speed reduction mechanism comprising a plurality of gears for increasing the rotation from the motor;
A housing that houses the speed reduction mechanism;
A support plate disposed within the housing and supporting the gears;
A holder disposed within the housing and supporting the support plate;
A rotation / linear motion conversion mechanism provided in the cylinder and propelled by the piston by rotation from the speed reduction mechanism and held in a braking position;
The support plate is
A first pivotal support that is coupled to a columnar support provided on the holder and defines a distance from the holder;
A second shaft supporting portion that rotatably supports one gear of the plurality of gears and supports the other end of the shaft whose one end is fixed to the holder;
The second shaft support part is a disc brake that restricts rotation of the support plate relative to the holder around the columnar support part. The holder is made of synthetic resin;
The disc brake according to claim 1, wherein the shaft is integrally fixed to the holder by insert molding.

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