WO2015151618A1

WO2015151618A1 - Disk brake

Info

Publication number: WO2015151618A1
Application number: PCT/JP2015/054442
Authority: WO
Inventors: 鶴見　理
Original assignee: 日立オートモティブシステムズ株式会社
Priority date: 2014-03-31
Filing date: 2015-02-18
Publication date: 2015-10-08
Also published as: JP6188922B2; JPWO2015151618A1

Abstract

A piston propulsion and maintenance mechanism (39) includes: a bottomed cylindrical member (46) which has an annular plate section (80) capable of contacting a bottom wall (19) of a cylinder (20) and a cylindrical section (81) connected to the outer periphery of the annular plate section (80) and covering a ball screw (44); and a clutch mechanism part (47) that, only when the ball screw (44) rotates in one direction, allows the bottomed cylindrical member (46) to rotate in the same direction. Because of the foregoing, once a piston (23) has been pressed against brake pads (2, 3) by the driving of a motor (32), the bottomed cylindrical member (46) is sandwiched and held so as to be unable to rotate between the annular plate section (80) and the bottom wall (19) by the counterforce on the ball screw (44), and rotation in a release direction of the ball screw (44) is restricted and a braking position is maintained by the clutch mechanism part (47).

Description

Disc brake

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

For example, Patent Document 1 includes a force transmission conversion mechanism that converts a rotational force of an electric motor into linear motion and presses a brake member against a braked member, and the force transmission conversion mechanism receives a rotational force from the electric motor. In the electric brake having the first rotating body and the second rotating body rotated by the first rotating body, a clutch mechanism is provided between the second rotating body and the non-rotating body. The rotational force of the electric motor is transmitted to the second rotating body via the first rotating body, and when the electric motor is stopped, the rotation of the second rotating body by the braking reaction force from the brake member is restricted. Sometimes, an electric brake configured to release the restriction is disclosed.

JP 2001-130402 A

However, in the electric brake according to the invention of Patent Document 1, since the braking position is held (braking lock) in the speed reduction mechanism, it is necessary to increase the strength of the speed reduction mechanism. Therefore, the weight of the speed reduction mechanism itself is increased. The problem arises that it leads to an increase in the weight of the disc brake.

Therefore, an object of the present invention is to hold the braking position while suppressing an increase in the weight of the disc brake.

As means for solving the above problems, a disc brake according to the present invention includes a pair of pads facing each other so as to sandwich a rotor that rotates together with a rotating part of a vehicle, and a piston that presses one of the pair of pads against the rotor. A disc brake comprising a caliper body having a cylinder in which the piston is movably disposed, and a brake holding mechanism for propelling the piston by an electric motor to hold the pair of pads at a braking position, The brake holding mechanism engages with a rotating member to which the rotational force of the electric motor is transmitted to one end side penetrating the bottom wall of the cylinder and the other end side of the rotating member. A linear member that moves and moves the piston, and an annular plate that is disposed between the rotating member and the bottom wall of the cylinder and faces the bottom wall of the cylinder And a bottomed cylindrical member integrally connected to the outer periphery of the annular plate portion and having a cylindrical portion covering the rotating member, and between the outer peripheral surface of the rotating member and the inner peripheral surface of the cylindrical portion And a clutch mechanism that rotates the bottomed cylindrical member in the same direction only when the rotating member rotates in one direction, and the piston is moved by the rotational drive of the electric motor. After pressing against the pad, the bottomed cylindrical member is held between the annular plate portion and the bottom wall of the cylinder in a non-rotatable state by the reaction force applied to the rotating member, and the rotation by the clutch mechanism portion. The rotation of the member in the return direction of the piston is restricted.

According to the disc brake of the present invention, it is possible to hold the braking position while suppressing an increase in weight.

Sectional drawing which shows a disc brake. Sectional drawing which expanded the principal part of the disc brake of FIG. FIG. 3 is a cross-sectional view taken along line AA in FIG. 2. Sectional drawing which follows the BB line of FIG.

Hereinafter, the present embodiment will be described in detail with reference to FIGS.
As shown in FIG. 1, the disc brake 1 according to the present embodiment includes a pair of inner brake pads 2 and an outer brake pad 3 disposed on both sides in the axial direction with a disc rotor D attached to a rotating portion of a vehicle interposed therebetween. , And caliper 4. The disc brake 1 is configured as a caliper floating type. The pair of inner brake pad 2, outer brake pad 3, and caliper 4 are supported by a bracket 5 fixed to a non-rotating portion (not shown) such as a knuckle of a vehicle so as to be movable in the axial direction of the disk rotor D. Has been.

As shown in FIGS. 1 and 2, the caliper body 10 that is the main body of the caliper 4 includes a cylinder portion 11 that is disposed on the base end side facing the inner brake pad 2 on the vehicle inner side, and an outer brake pad 3 on the vehicle outer side. And a claw portion 12 that is disposed on the tip side facing the. The cylinder portion 11 is formed with a bottomed cylinder 20 that is closed by a bottom wall 19 having an opening portion 21 on the inner brake pad 2 side and a hole portion 18 on the opposite side. The inside of the cylinder 20 includes a small diameter opening 20a provided on the bottom wall 19 side and a large diameter opening 20b provided on the opening 21 side. The cylinder 20 is provided with a piston seal 22 on the inner peripheral surface on the opening 21 side.
In the following description, the bottom wall 19 side of the cylinder 20 will be described as one end side, and the opening 21 side of the cylinder 20 will be described as the other end side.

The piston 23 is formed in a bottomed cup shape including a bottom portion 24 and a cylindrical portion 25. The inside of the cylindrical portion 25 includes a small diameter portion 25a formed on one end side and a large diameter portion 25b formed on the other end side. A nut member 45 of the ball screw mechanism 43 is disposed in the large diameter portion 25b so as to be movable in the axial direction and immovable in the rotational direction. The piston 23 is accommodated in the large-diameter opening 20b of the cylinder 20 so as to be opposed to the inner brake pad 2 so as to face the inner brake pad 2 so as to be movable in the axial direction in contact with the piston seal 22. A hydraulic chamber 26 defined by a piston seal 22 is formed between the piston 23 and the bottom wall 19 of the cylinder 20.

The fluid pressure chamber 26 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 11. The piston 23 has a recess 27 formed on the outer peripheral side of the bottom 24 facing the inner brake pad 2. A concave portion 27 provided in the bottom portion 24 and a convex portion 28 formed on the back surface of the inner brake pad 2 are engaged. With this engagement, the piston 23 rotates relative to the cylinder 20 and eventually the caliper body 10. It becomes impossible. In addition, a dust boot 29 is interposed between the bottom 24 of the piston 23 and the cylinder 20 to prevent foreign matter from entering the cylinder 20.

Further, as shown in FIG. 1, a housing 30 is airtightly attached to the bottom wall 19 side of the cylinder 20 of the caliper body 10. In other words, the housing 30 and the bottom wall 19 of the cylinder 20 are kept airtight by the seal member 31. The housing 30 is formed so as to accommodate a motor 32 that is an example of an electric motor arranged so as to be aligned with the caliper body 10. That is, the housing 30 is formed so as to cover the outer periphery of the bottom wall 19 of the cylinder 20, and is integrally formed so as to be aligned with the first housing 33 that houses a planetary gear reduction mechanism 41 and the like that will be described later. It is comprised from the 2nd housing 34 which accommodates the motor 32.

The first housing 33 is provided with an opening 33a through which a cylindrical portion 67 on one end side of a ball screw 44 of a ball screw mechanism 43 described later is inserted. A cover 35 is hermetically attached to one end openings of the first housing 33 and the second housing 34 of the housing 30. The first housing 33 and the second housing 34 and the cover 35 are hermetically sealed by welding or adhesive bonding. In order to maintain this airtightness, a seal member made of an elastic body such as rubber may be sandwiched between the housing 30 and the cover 35 to join the housing 30 and the cover 35.

As shown in FIG. 1, the caliper body 10 includes a piston propulsion holding mechanism 39 that moves the piston 23 by the rotational drive of the motor 32 and holds the piston 23 at its braking position, and a flat-tooth multistage reduction mechanism that increases the rotation by the motor 32. 40 and a planetary gear speed reduction mechanism 41. The piston propulsion holding mechanism 39 has a function of moving the piston 25 to the braking position and generating a braking force by the pair of inner and

outer brake pads

2 and 3, and the piston 25 (the pair of inner and outer brake pads 2 and 3). It has a function of maintaining the braking force by holding at the braking position. The piston propulsion holding mechanism 39 corresponds to a brake holding mechanism. The spur multi-stage reduction mechanism 40 and the planetary gear reduction mechanism 41 are accommodated in the first housing 33 and the second housing 34. The piston propulsion holding mechanism 39 is accommodated in the cylinder 20 of the caliper body 10.
The configuration of the speed reduction mechanism is not limited to the embodiment, and any configuration that transmits the driving force of the motor 32 to the piston propulsion holding mechanism 39 may be used.

As shown in FIGS. 1 and 2, the piston propulsion holding mechanism 39 converts the rotational movement from the spur multi-stage reduction mechanism 40 and the planetary gear reduction mechanism 41 into linear movement (hereinafter referred to as linear movement for convenience), A ball screw mechanism 43 that applies thrust to the piston 23, a bottomed cylindrical member 46 disposed so as to surround a clutch shaft portion 69 of the ball screw 44 of the ball screw mechanism 43, a clutch shaft portion 69 of the ball screw 44, and a bottom The clutch mechanism part 47 is arranged between the cylindrical part 81 of the cylindrical member 46. In addition, although the mechanism for converting the rotational motion of the present invention into the linear motion is the ball screw mechanism 43, the present invention is not limited to this, and if the rotational motion is converted into the linear motion and the input shaft moves linearly with the rotation, The present invention can be applied.

As shown in FIG. 1, the spur multi-stage reduction mechanism 40 has a first reduction gear 50 and a second reduction gear 51. A common shaft 52 is press-fitted into the first reduction gear 50 and the second reduction gear 51. The shaft 52 is rotatably supported between a support plate 53 adjacent to the cover 35 and a wall portion 54 in the second housing 34. The first reduction gear 40 meshes with a pinion gear 55 into which the rotation shaft 32a of the motor 32 is press-fitted. The second reduction gear 51 meshes with external teeth of a large gear 58 to which a sun gear 59 that is a configuration of a planetary gear reduction mechanism 41 described later is integrally connected. A sun gear 59 projects from the large gear 58 in the radial direction on the cylinder 20 side, and a shaft 60 is press-fitted into the large gear 58. The shaft 60 is rotatably supported by the support plate 53.

The planetary gear speed reduction mechanism 41 includes a sun gear 59 of a large gear 58, a plurality (four in this embodiment) of planetary gears 62, an internal gear 63, and a carrier 64. The internal gear 63 is fixed in the first housing 33 so as not to move in the axial direction and the rotational direction. Each planetary gear 62 meshes with the internal teeth of the internal gear 63. Each planetary gear 62 meshes with the sun gear 59 of the large gear 58, and each pin 65 erected at equal intervals in the circumferential direction of the carrier 64 is rotatably inserted therethrough. The planetary gears 62 are arranged at equal intervals on the circumference of the carrier 64. Accordingly, the sun gear 59 of the planetary gear speed reduction mechanism 41 is rotated by the rotation drive of the motor 32 via the spur gear multi-stage speed reduction mechanism 40, and the carrier 64 is rotated via each planetary gear 62 by the rotation of the sun gear 59. .

The carrier 64 is formed in a disk shape, and has a spline hole 64a provided at a substantially central portion in the radial direction. The outer diameter of the carrier 64 is formed larger than the inner diameter of the opening 33 a of the first housing 33. The spline hole 64a of the carrier 64 and the spline shaft 67a provided at the tip of the cylindrical portion 67 of the ball screw 44 of the ball screw mechanism 43, which will be described later, are engaged with each other, so that rotational torque is transmitted between the carrier 64 and the ball screw 44. It can be done.

In the present embodiment, in order to obtain the rotational force for propelling the piston 23, the spur multi-stage reduction mechanism 40 and the planetary gear reduction mechanism 41 that increase the rotational force by the motor 32 are employed. You may comprise only. Further, a speed reducer according to another known technique such as a cyclone speed reducing mechanism or a wave speed reducer may be combined with the planetary gear speed reducing mechanism.

As shown in FIGS. 1 and 2, the ball screw mechanism 43 is screwed into a ball screw 44 as a rotating member to which the rotational force from the motor 32 is transmitted and a screw portion 68 of the ball screw 44. And a plurality of balls 48 interposed between a male screw portion 68a of the ball screw 44 and a female screw portion 45a of the nut member 45.

The ball screw 44 is provided on one end side, and a cylindrical portion 67 inserted into the hole 18 of the bottom wall 19 of the cylinder 20 and a screw portion extending into the piston 23 on the other end side and having a male screw portion 68a on the outer peripheral surface. 68 and a clutch shaft portion 69 provided between the cylindrical portion 67 and the screw portion 68 are integrally connected. The cylindrical portion 67 is inserted into the hole 18 of the bottom wall 19 of the cylinder 20 and a spline shaft 67 a provided at the tip of the cylindrical portion 67 is fitted in a spline hole 64 a provided in the carrier 64. The clutch shaft 69 is disposed in the small diameter opening 20 a of the cylinder 20. The clutch shaft portion 69 is formed with a larger diameter than the cylindrical portion 67 and the screw portion 68. The clutch shaft portion 69 is configured by integrally connecting a large-diameter clutch shaft portion 72 provided on one end side and a small-diameter clutch shaft portion 73 provided on the other end side. An O-ring 74 and a sleeve 75 are disposed between the cylindrical portion 67 of the ball screw 44 and the hole 18 of the bottom wall 19 of the cylinder 20. A friction plate 78 is disposed on the surface of the bottom wall 19 of the cylinder 20 facing the small diameter opening 20a. The friction plate 78 has functions such as preventing the O-ring 74 from coming off and preventing damage when the bottomed cylindrical member 46 rotates, and protecting the cylinder 20 against receiving a load on the bottom 24.

A bottomed cylindrical member 46 is disposed close to the outer periphery of the clutch shaft 69 of the ball screw 44. The bottomed cylindrical member 46 includes an annular plate portion 80 and a cylindrical portion 81 that is integrally connected to the outer periphery of the annular plate portion 80. The annular plate portion 80 is disposed between the clutch shaft portion 69 of the ball screw 44 and the friction plate 78 disposed on the bottom wall 19 of the cylinder 20. A substantially circular contact portion 82 that can come into contact with the friction plate 78 protrudes from a central portion in the radial direction of the surface of the annular plate portion 80 on the bottom wall 19 side of the cylinder 20. The cylindrical portion 81 is disposed so as to surround the clutch shaft portion 69 of the ball screw 44. A clutch mechanism 47 is disposed between the clutch shaft 69 of the ball screw 44 and the cylindrical part 81 of the bottomed cylindrical member 46. Referring also to FIG. 4, the clutch mechanism portion 47 includes a plurality of clutch groove portions 85 provided at intervals along the circumferential direction on the outer peripheral surface on the other end side of the large diameter clutch shaft portion 72, and each clutch groove portion 85. Each of the clutch balls 86 is arranged in the inside, and a torsion spring 87 that urges each clutch ball 86 in the counterclockwise direction (rotation direction at the time of application) in FIG. In the present embodiment, three clutch groove portions 85 are formed. On the bottom surface of each clutch groove 85, a cam surface 90 is formed whose groove depth becomes shallower in the counterclockwise direction (rotation direction at the time of application) in FIG.

2 to 4, an annular plate 91 is disposed around the small diameter clutch shaft portion 73 on the other end surface of the large diameter clutch shaft portion 72 of the clutch shaft portion 69. The annular plate 91 is restricted from moving in the axial direction by a retaining ring 93 provided on the inner peripheral surface of the other end of the cylindrical portion 81 of the bottomed tubular member 46, but is allowed to move in the rotational direction. The annular plate 91 is formed with a pressing plate portion 92 that is bent and erected on the side of each clutch groove 85 at a position corresponding to each clutch groove 85 of the large-diameter clutch shaft portion 72. In FIG. 4, each pressing plate portion 92 is disposed at a position where the clutch ball 86 in each clutch groove 85 can be pressed in the counterclockwise direction (rotating direction at the time of application). A torsion spring 87 is disposed around the small diameter clutch shaft portion 73. One end of the torsion spring 87 is fixed to the surface of the annular plate 91 on the piston 23 side, and the other end of the torsion spring 87 is fixed to the outer peripheral surface of the small diameter clutch shaft 73. As a result, the annular plate 91 (each pressing plate portion 92) is biased by the biasing force of the torsion spring 87 so as to rotate in the counterclockwise direction (rotating direction at the time of application) in FIG. In the bottomed tubular member 46, a thrust bearing 70 is disposed between the annular plate portion 80 and the large-diameter clutch shaft portion 72 of the clutch shaft portion 69.

When the ball screw 44 is rotated counterclockwise in FIG. 4 when the piston 23 is propelled, each clutch ball 86 resists the biasing force of the torsion spring 87 and the cam surface 90 and the cylindrical portion. It moves by the frictional force between the inner peripheral surfaces of 81, and the meshing state is released. For this reason, the bottomed cylindrical member 46 rotates idly with respect to the rotation of the ball screw 44 in the apply direction of the clutch shaft portion 69. On the other hand, when the ball screw 44 is rotated in the clockwise direction in FIG. 4 when releasing the piston 23, each clutch ball 86 is brought into the engagement position of the cam surface 90 of the clutch groove 85 by the biasing force of the torsion spring 87. The wedge shaft action between the cam surface 90 of the clutch groove portion 85 of the clutch shaft portion 69 and the inner peripheral surface of the cylindrical portion 81 of the bottomed tubular member 46 allows the clutch shaft portion 69 to rotate in the release direction. On the other hand, the bottomed tubular member 46 also rotates in the same direction. In short, in the present embodiment, due to the action of the clutch mechanism portion 47, the mutual rotational force is not transmitted between the bottomed cylindrical member 46 and the ball screw 44 in the rotational direction during the application, In the rotational direction at the time of release, the mutual rotational force is transmitted between the bottomed tubular member 46 and the ball screw 44.

As shown in FIG. 1, the screw portion 68 of the ball screw 44 extends into the small diameter portion 25 a of the cylindrical portion 25 of the piston 23. The nut member 45 screwed into the screw portion 68 of the ball screw 44 via each ball 48 is movable in the axial direction within the large diameter portion 25b of the cylindrical portion 25 of the piston 23 and is supported so as not to rotate. . As a result, when the ball screw 44 is rotated in the apply direction, the nut member 45 moves to the other end side, and the piston 25 presses the inner brake pad 2.

Next, the operation of the disc brake 1 according to this embodiment will be described. First, the operation of the disc brake 1 as a normal hydraulic brake by operating the brake pedal will be described.

When the brake pedal is depressed by the driver, the hydraulic pressure corresponding to the depressing force of the brake pedal is supplied from the master cylinder to the hydraulic pressure chamber in the caliper 4 through a hydraulic pressure circuit (both not shown). As a result, the piston 23 moves forward (moves leftward in FIG. 1) from the original position during non-braking while pushing the inner brake pad 2 against the disc rotor D while elastically deforming the piston seal 22. The caliper body 10 moves to the right in FIG. 1 with respect to the bracket 5 by the reaction force of the pressing force of the piston 23, and presses the outer brake pad 3 against the disc rotor D by the claw portion 12. 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.

On the other hand, when the driver releases the brake pedal, the supply of the hydraulic pressure from the master cylinder is interrupted, and the hydraulic pressure in the hydraulic pressure chamber 26 decreases. As a result, the piston 23 is retracted to the original position by the restoring force of the elastic deformation of the piston seal 22 and the braking force is released.

Next, in the disc brake 1 according to this embodiment, for example, an operation as a parking brake will be described. First, a parking switch (not shown) is operated from the released state of the parking brake, and an electric signal is input from the ECU (not shown) to the motor 32 to rotate the motor 32. The sun gear 59 of the planetary gear speed reduction mechanism 41 is rotated by the rotation drive of the motor 32 via the spur multi-stage speed reduction mechanism 40. Due to the rotation of the sun gear 59, the carrier 64 is rotated via each planetary gear 62. Then, the rotational force from the carrier 64 is transmitted to the ball screw 44 of the ball screw mechanism 43. At this time, when the ball screw 44 rotates in the rotation direction at the time of application (counterclockwise direction in FIG. 4), each clutch ball 86 of the clutch mechanism portion 47 resists the biasing force of the torsion spring 87 and the cam surface 90 and the cylinder. The mesh portion 81 is moved by the frictional force between the inner peripheral surfaces of the shaped portion 81, and the meshing state is released. For this reason, the bottomed tubular member 46 idles with respect to the rotation of the ball screw 44 in the apply direction. Then, when the nut member 45 screwed through the ball screw 44 and each ball 48 moves forward (moves leftward in FIG. 1), the piston 23 moves forward.

Further, when the motor 32 is driven to rotate, the piston 23 starts to press the disc rotor D through the

brake pads

2 and 3 as the nut member 45 advances. The ECU 32 rotates the motor 32 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. Thereafter, when the ECU 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 32 has reached a predetermined value, the ECU stops energization of the motor 32. At this time, the ball screw 44 tends to rotate slightly in the release direction due to the reaction force from the pressing force to the disk rotor D, while the annular plate portion 80 of the bottomed cylindrical member 46 also presses the disk rotor D. Reaction force from the piston 23, the nut member 45, and the clutch shaft 69 of the ball screw 44, the bottomed cylindrical shape is caused by the frictional force between the contact portion 82 of the annular plate portion 80 and the friction plate 78. The member 46 is clamped between the contact portion 82 of the annular plate portion 80 and the friction plate 78 so as not to rotate. Thereby, the ball screw 44 is also rotated by the wedge action of each clutch ball 86 between the cam surface 90 of each clutch groove 85 of the clutch shaft 69 and the inner peripheral surface of the cylindrical portion 81 of the bottomed cylindrical member 46. Be regulated. With this action, the braking force applied to the disc rotor D by the pair of inner and

outer pads

2 and 3 is maintained, and the operation of the parking brake is completed.

Next, when releasing the parking brake, based on the parking release operation of the parking switch, the ECU rotationally drives the motor 32 in the rotation direction at the time of release, that is, the rotation direction in which the piston 23 is separated from the disk rotor D. . As a result, the reaction force from the disk rotor D to the bottomed cylindrical member 46 is released by the rotation of the spur multi-stage speed reduction mechanism 40 and the planetary gear speed reduction mechanism 41 in the release direction. The frictional force between the contact portion 82 of the annular plate portion 80 of the member 46 and the friction plate 78 disappears, and the bottomed tubular member 46 becomes free in the rotational direction. Then, by rotation of the ball screw 44 in the release direction (clockwise rotation in FIG. 4), each clutch ball 86 advances to a meshing position with the cam surface 90 of the clutch groove 85 by the biasing force of the torsion spring 87, Due to the wedge action between the cam surface 90 of the clutch shaft portion 69 and the inner peripheral surface of the cylindrical portion 81 of the bottomed cylindrical member 46, the bottomed cylindrical member 46 starts to rotate in the release direction together with the ball screw 44. Finally, the piston 23 moves backward in a direction away from the inner and

outer pads

2 and 3 to release the parking brake.

As described above, the disc brake 1 according to the present embodiment includes the piston propulsion holding mechanism 39, and the piston propulsion holding mechanism 39 is a friction plate on the clutch shaft portion 69 of the ball screw 44 and the bottom wall 19 of the cylinder 20. 78 and an annular plate portion 80 having a contact portion 82 that can come into contact with the friction plate 78, and integrally connected to the outer periphery of the annular plate portion 80, and the clutch shaft portion 69 of the ball screw 44. Arranged between the bottomed cylindrical member 46 having a cylindrical portion 81 covering the outer periphery, and the outer peripheral surface of the clutch shaft portion 69 of the ball screw 44 and the inner peripheral surface of the cylindrical portion 81 of the bottomed cylindrical member 46. And a clutch mechanism 47 that causes the bottomed tubular member 46 to follow the rotation of the ball screw 44 only in the release direction. As a result, the piston 23 is pressed against the pair of inner and

outer brake pads

2, 3 by the rotational drive of the motor 32, and then the bottomed tubular member 46 is moved to the annular plate portion 80 by the reaction force applied to the ball screw 44. Between the provided contact portion 82 and the friction plate 78 provided on the bottom wall 19 of the cylinder 20, the rotation of the ball screw 44 in the release direction is restricted by the clutch mechanism portion 47. The braking force applied to the disk rotor D by the pair of inner and

outer pads

2 and 3 is maintained. Accordingly, it is possible to provide the disc brake 1 that maintains the braking state while suppressing an increase in weight.

1 disc brake, 2 inner brake pad, 3 outer brake pad, 4 caliper, 10 caliper body, 11 cylinder part, 19 bottom wall, 20 cylinder, 23 piston, 32 motor (electric motor), 39 piston propulsion holding mechanism (brake holding) Mechanism), 43 ball screw mechanism, 44 ball screw (rotating member), 45 nut member (linear motion member), 46 bottomed cylindrical member, 47 clutch mechanism part, 80 annular plate part, 81 cylindrical part, 82 contact part, D Disc rotor

Claims

A pair of pads opposed so as to sandwich a rotor that rotates together with a rotating part of the vehicle, a piston that presses one of the pair of pads against the rotor, and a caliper body having a cylinder in which the piston is movably disposed; A disc brake including a brake holding mechanism for propelling the piston by an electric motor to hold the pair of pads in a braking position;
The brake holding mechanism is
A rotating member that transmits the rotational force of the electric motor to one end side that penetrates the bottom wall of the cylinder;
A direct acting member that engages with the other end of the rotating member and moves the piston by direct movement by rotation of the rotating member;
An annular plate portion disposed between the rotating member and the bottom wall of the cylinder, facing the bottom wall of the cylinder, and a cylindrical portion integrally connected to the outer periphery of the annular plate portion and covering the rotating member A bottomed cylindrical member having
A clutch mechanism that is disposed between the outer peripheral surface of the rotating member and the inner peripheral surface of the cylindrical portion, and rotates the bottomed cylindrical member in the same direction only when the rotating member rotates in one direction; Have
After the piston is pressed against the pair of pads by the rotation of the electric motor, the bottomed cylindrical member is placed between the annular plate portion and the bottom wall of the cylinder by a reaction force applied to the rotating member. A disc brake that is held in a non-rotatable state and restricts rotation of the rotating member in the return direction of the piston by the clutch mechanism.
The clutch mechanism portion includes a plurality of clutch groove portions provided at intervals along the circumferential direction of the rotating member, clutch balls respectively disposed in the clutch groove portions, and the clutch balls in the one direction. A torsion spring that biases in the direction of rotation when rotating,
2. The clutch ball is moved by a frictional force between a cam surface of the clutch groove and an inner peripheral surface of the rotating member against an urging force of the torsion spring to release the meshing state. Disc brake as described.
When the electric motor rotationally drives the rotating member to rotate in a direction opposite to the one direction, the clutch balls advance to a meshing position of the cam surface of the clutch groove by the biasing force of the torsion spring, 3. The disc brake according to claim 2, wherein the rotating member also rotates in a direction opposite to the one direction by a wedge action between a cam surface and the inner peripheral surface of the rotating member.