Electric brake device

Abstract

Provided is an electric brake device capable of reducing the number of components of a drive source for braking and parking braking. An electric brake device (100) is provided with: a motor (3); a rotating shaft (6) which is provided so that the parking screwing part (60) and the braking screwing part (61) have a common central axis (C1) and which is rotated by the motor (3); and a piston (101) that includes: a parking piston part (7) that presses the brake pad (9a) by rotating the rotating shaft (6) in one rotation direction (R1) in a state in which the parking piston part (7) is screwed to the parking screwing part (60) and moving in the axial direction of the central axis (C1); and a brake piston section (8) that presses the brake pad (9a) by rotating the rotating shaft (6) in the other rotational direction while being screwed to the brake screwing section (61) and moving in the axial direction together with the parking piston section (7) moving in the direction in which the parking piston section (7) is separated from the axial brake pad (9a).

Description

Technical Field

[0001] The present invention relates to an electric braking device. Background Art

[0002] Conventionally, an electric braking device having a motor has been known (for example, refer to Patent Document 1).

[0003] In the above Patent Document 1, an electric braking device having a motor, a rotating shaft rotated by the motor, and a single piston screwed to the rotating shaft is disclosed. The piston moves forward and backward in the axial direction as the rotating shaft rotates. Further, the piston is configured to press a brake pad against a brake disc to brake the brake disc (tire). That is, the electric braking device is used as a so-called service brake which is a brake during normal operation.

[0004] The above electric braking device further includes a ratchet mechanism that holds the state in which the brake pad is pressed against the brake disc by the piston and is used to hold the parked state. The ratchet mechanism is configured to be driven by an electric solenoid, and in the state where the brake pad is pressed against the brake disc, the movement of the piston is locked to hold the parked state. That is, the electric braking device is also used as a parking brake.

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2006-142935

[0006] However, in the electric braking device of the above Patent Document 1, both a motor and an electric solenoid are required as drive sources for braking and parking braking. Conventionally, it has been required to reduce the number of components of the drive source for braking and parking braking in the electric braking device. Summary of the Invention

[0007] The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an electric braking device capable of reducing the number of components of the drive source for braking and parking braking.

[0008] To achieve the above object, an electric braking device according to an aspect of the present invention includes: a motor; a rotating shaft provided such that a parking screw portion and a braking screw portion have a common central axis and rotated by the motor; and a piston including: a parking piston portion that moves in the axial direction of the central axis by rotating in one rotation direction of the rotation axis in a state of being screwed to the parking screw portion to press a brake pad; and a braking piston portion that moves in the axial direction together with the parking piston portion in a direction separating from the brake pad in the axial direction by rotating in the other rotation direction opposite to the one rotation direction of the rotation axis in a state of being screwed to the braking screw portion to press the brake pad.

[0009] In the electric braking device according to one aspect of the present invention, as described above, there is provided a parking piston portion that presses a brake pad by moving axially in the direction of the central axis by rotating the rotating shaft in one rotation direction while being screwed into the parking screw portion of the rotating shaft; and a braking piston portion that moves axially together with the parking piston portion in the direction of separating from the brake pad by rotating the rotating shaft in the other rotation direction opposite to the one rotation direction while being screwed into the braking screw portion of the rotating shaft, and presses the brake pad. Thus, it is possible to switch the rotation direction of the rotating shaft by a motor as a drive source, move the parking piston portion to maintain the parked state. In addition, it is possible to switch the rotation direction of the rotating shaft by a motor as a drive source, move the braking piston portion to press the brake pad against the disc rotor and brake the disc rotor (tire). That is, it is possible to maintain the braking and parked states only by one motor. Therefore, there is no need for an electric solenoid for maintaining the parked state as in the prior art. As a result, it is possible to reduce the number of components of the drive source for braking and parking braking.

[0010] In the electric braking device according to the above one aspect, it is preferable that the piston includes a single pad contact member, and the single pad contact member is provided in a common structure for the parking piston portion and the braking piston portion so as to cover the parking piston portion and the braking piston portion from the brake pad side, and contacts the brake pad. The parking piston portion and the braking piston portion are configured to contact the brake pad via the pad contact member to press the brake pad.

[0011] If configured in this way, compared with the case of switching a plurality of components to press the brake pad, it is possible to ensure a larger contact area between the brake pad and the component that presses the brake pad, that is, the pad contact member. Therefore, it is possible to effectively generate a frictional force between the pad contact member and the brake pad to maintain the braking and parked states.

[0012] In the electric braking device according to the above one aspect, it is preferable that the parking screw portion is an external thread for parking provided on the outer peripheral surface of the rotating shaft and screwed into the parking piston portion, and the braking screw portion is a ball screw provided on the inner peripheral surface of the rotating shaft and screwed into the braking piston portion.

[0013] If configured in this way, it is possible to screw the parking piston portion into the external thread for parking of the rotating shaft from the outer peripheral side, so it is possible to suppress the enlargement of the rotating shaft. In addition, it is possible to smoothly operate the braking piston portion with respect to the braking screw portion of the rotating shaft by the ball screw, so it is possible to improve the responsiveness of the braking piston portion.

[0014] In the electric braking device according to one aspect described above, it preferably further includes a housing that houses a rotating shaft, a parking piston portion, and a braking piston portion. The rotating shaft is configured to move in a direction opposite to the pressing direction of the braking block by the parking piston portion when receiving a reaction force caused by the parking piston portion pressing the braking block against the disc-shaped rotor. The rotating shaft includes a contact portion that contacts the housing when the rotating shaft moves in a direction opposite to the pressing direction.

[0015] If configured in this way, the holding force for maintaining the parked state can be further increased by the contact portion that contacts the housing, so the parked state can be maintained more stably.

[0016] In addition, in the electric braking device according to one aspect described above, the following configuration is also considered.

[0017] (Supplementary Note Item 1)

[0018] In the above electric braking device, it is preferable that the parking piston portion and the braking piston portion are configured to directly contact the braking block to press the braking block. The parking piston portion is formed in an annular shape when viewed from the axial direction of the central axis, and the braking piston portion is formed in a circular shape that is arranged inside the parking piston portion when viewed from the axial direction of the central axis.

[0019] If configured in this way, compared with the screwed portion between the braking piston portion and the rotating shaft, the screwed portion between the parking piston portion and the rotating shaft can be arranged on the outer side (outer peripheral side), so the radial distance from the central axis of the rotating shaft to the screwed portion between the parking piston portion and the rotating shaft can be ensured to be larger, and the lead angle of the thread of the parking screwed portion can be reduced. As a result, the frictional force of the parking screwed portion can be increased.

[0020] (Supplementary Note Item 2)

[0021] In the structure where the above parking screwed portion is an external thread for parking provided on the outer peripheral surface of the rotating shaft and screwed with the parking piston portion, it is preferable that the rotating shaft is formed in a cylindrical shape with an external thread for parking provided on the outer peripheral surface, and the braking screwed portion is an internal thread for braking provided on the inner peripheral surface of the rotating shaft and screwed with the braking piston portion. In the axial direction, at least a part of the external thread for parking and the internal thread for braking are formed in an overlapping range.

[0022] If configured in this way, in the axial direction, the external thread for parking of the rotating shaft and the internal thread for braking of the rotating shaft can be overlapped, so the size of the rotating shaft in the axial direction can be reduced, and the device can be miniaturized in the axial direction.

[0023] (Supplementary Note Item 3)

[0024] In the structure in which the above-mentioned parking screw-on portion is a parking external thread arranged on the outer circumferential surface of the rotating shaft and screwed with the parking piston portion, it is preferred that the braking screw-on portion is a braking external thread arranged on the outer circumferential surface of the rotating shaft and screwed with the braking piston portion, and the rotating shaft includes a parking rotating shaft portion provided with the parking external thread, and a braking rotating shaft portion connected to one axial end of the parking rotating shaft portion and provided with the braking external thread, and in the axial direction, the parking external thread and the braking external thread are formed in a range that is staggered and does not overlap each other.

[0025] According to this structure, the parking piston and the braking piston can be arranged on the outer peripheral side of the rotating shaft, so the size of the rotating shaft in the direction intersecting the axial direction can be reduced, and the device can be miniaturized in the direction intersecting the axial direction.

[0026] (Supplementary Item 4)

[0027] In the structure having the above-mentioned housing and the rotating shaft including an abutment portion, it is preferably also provided with a force-applying component arranged between the housing and the rotating shaft in the axial direction, and the rotating shaft is constructed so that when it is subjected to a reaction force caused by the parking piston portion pressing the brake pad against the disc rotor, it overcomes the force of the force-applying component and moves in a direction opposite to the pressing direction of the brake pad, so that the abutment portion abuts against the housing.

[0028] According to this structure, when the rotating shaft is subjected to a reaction force caused by the parking piston portion pressing the brake pad against the disc rotor through the force applying member, the abutment portion of the rotating shaft can be brought into contact with the housing in such a manner that the force applying member begins to deform. That is, when the rotating shaft is braked by a relatively small reaction force from the braking piston portion side, the force applying member can be prevented from deforming and the abutment portion of the rotating shaft from coming into contact with the housing.

[0029] (Supplementary Item 5)

[0030] In the structure including the housing and the rotating shaft including the abutment portion, it is preferable that the abutment portion is a flange portion extending in a direction intersecting the axial direction and in surface contact with the inner bottom surface of the housing.

[0031] If it is constituted in this way, the contact surface area of the rotating shaft and the housing that generates the holding force for holding the parking state can be ensured to be larger through the abutment portion constituted by the flange portion. As a result, a larger holding force for holding the parking state can be generated.

[0032] (Supplementary Item 6)

[0033] In the above structure in which the piston includes the pad contact member, it is preferable to further include a biasing member that biases the parking piston portion and the braking piston portion toward the brake pad and biases the pad contact member in a direction opposite to the parking piston portion and the braking piston portion.

[0034] If configured in this way, the biasing member can apply pressure to the parking piston portion, the braking piston portion, and the pad contact member in a direction in which they separate from each other. Therefore, when switching between the braking state and the parking state, etc., it is possible to suppress a situation where a gap is generated between the positions of the pad contact member and the parking piston portion and the braking piston portion.

[0035] The present invention can reduce the number of components of the drive source for braking and parking braking. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a cross-sectional view showing the electric braking device and the tire of the first embodiment as viewed from the side.

[0037] Figure 2 It is a cross-sectional view showing the electric braking device of the first embodiment as viewed from the side, and is a view showing the parking state by the parking piston portion.

[0038] Figure 3 It is a cross-sectional view showing the electric braking device of the first embodiment as viewed from the side, and is a view showing the braking state by the braking piston portion.

[0039] Figure 4 It is a cross-sectional view showing the electric braking device of the second embodiment as viewed from the side.

[0040] Figure 5 It is a cross-sectional view showing the electric braking device of the third embodiment as viewed from the side.

[0041] Figure 6 It is a view for explaining the switching of the braking state, the neutral state, and the parking state of the electric braking device of the third embodiment.

[0042] Figure 7 It is a cross-sectional view showing the rotating shaft, the parking piston portion, and the braking piston portion of the electric braking device of the first modification as viewed from the side.

[0043] Figure 8 It is a cross-sectional view showing the rotating shaft, the parking piston portion, and the braking piston portion of the electric braking device of the second modification as viewed from the side.

[0044] Figure 9 It is a cross-sectional view showing the rotating shaft, the parking piston portion, and the braking piston portion of the electric braking device of the third modification as viewed from the side.

[0045] DESCRIPTION OF REFERENCE NUMERALS

[0046] 1: Housing, 3: Motor, 6, 206, 406, 606: Rotating shaft, 7, 207, 307, 507, 607: Parking piston part, 8, 208, 308, 508, 608: Braking piston part, 9a: Brake block, 9b: Disk rotor, 60, 660: (Rotating shaft) parking thread part, 61, 261, 461: (Rotating shaft) braking thread part, 61a: Ball screw, 62: (Rotating shaft) outer peripheral surface, 63: (Rotating shaft) inner peripheral surface, 64: (Rotating shaft) abutting part, 100, 200, 300, 400, 500, 600: Electric braking device, 101, 201, 301: Piston, 309: Pad contact member, C1: Central axis. Detailed implementation mode

[0047] Hereinafter, the implementation mode of the present invention will be described with reference to the drawings.

[0048] (First implementation mode)

[0049] Refer to Figures 1 to 3 The structure of the electric braking device 100 of the first implementation mode will be described.

[0050] Figure 1 The shown electric braking device 100 is an electric braking device provided on the tire T of a vehicle. The electric braking device 100 is used to brake the tire T (disk rotor 9b) and maintain the parked state of the vehicle. The electric braking device 100 can be provided only on a part of the tires T, such as only the front wheels or only the rear wheels, or can be provided on all the tires T.

[0051] The electric braking device 100 is mounted on a vehicle with a by-wire shift system that performs shift control based on an operation signal from a shift operation unit provided with a shift sensor. Although it is an example, when the control unit receives an operation signal for switching from the parking release state to the parking state from the shift operation unit, the electric braking device 100 is driven and controlled to perform an operation for switching from the parking release state to the parking state.

[0052] Here, in the drawings, the axial direction of the central axis C1 of the rotating shaft 6 of the electric braking device 100 is represented by the A direction. In the A direction, the pressing direction of the brake block 9a by the parking piston part 7 and the braking piston part 8 described later is represented by the A1 direction, and the opposite direction is represented by the A2 direction. In addition, the central axis C1 is also the central axis shared by the parking thread part 60 and the braking thread part 61 described later. In addition, the central axis C2 of the motor shaft 32 of the motor 3 and the central axis C3 of the disk rotor 9b (tire T) also extend in the A direction.

[0053] In addition, in the drawings, one rotational direction of the rotary shaft 6 is indicated by the R1 direction, and the other rotational direction opposite to one rotational direction of the rotary shaft 6 is indicated by the R2 direction. Although it is an example, when the motor 3 rotates forward, the rotary shaft 6 rotates in one rotational direction (the R1 direction), and when the motor 3 rotates in reverse, the rotary shaft 6 rotates in the other rotational direction (the R2 direction). In addition, although it is an example, when the motor 3 rotates forward, the parking piston portion 7 moves in the A1 direction, and at the same time, the braking piston portion 8 moves in the A2 direction. When the motor 3 rotates in reverse, the parking piston portion 7 moves in the A2 direction, and at the same time, the braking piston portion 8 moves in the A1 direction.

[0054] The electric braking device 100 includes: a housing 1, a biasing member 2, a motor 3 as a drive source, a transmission gear 4 that transmits the driving force of the motor 3, a driven gear 5 that rotates by transmitting the driving force of the motor 3 via the transmission gear 4, a rotary shaft 6 that rotates together with the motor 3 and the driven gear 5, a piston 101, a brake pad 9a, and a disk-shaped rotor 9b. The piston 101 includes a parking piston portion 7 and a braking piston portion 8. The parking piston portion 7 and the braking piston portion 8 are configured to be in direct contact with the brake pad 9a to press the brake pad 9a. The parking piston portion 7 and the braking piston portion 8 come into contact with the brake pad 9a at different times. The piston 101 includes only one parking piston portion 7. That is, the parking piston portion 7 is a single structure. The piston 101 includes only one braking piston portion 8. That is, the braking piston portion 8 is a single structure.

[0055] (Structure of the housing)

[0056] Each part of the electric braking device 100 (the motor 3, the transmission gear 4, the driven gear 5, the rotary shaft 6, the parking piston portion 7, the braking piston portion 8, the biasing member 2, the brake pad 9a) is housed in the housing 1. In addition, a part of the disk-shaped rotor 9b opposed to the brake pad 9a is housed in the housing 1.

[0057] The housing 1 is configured to be divisible into a plurality of parts in consideration of assemblability. Specifically, the housing 1 includes a cylindrical housing main body 10 and a cover member 11. The rotary shaft 6, the parking piston portion 7, the braking piston portion 8, etc. are housed in the cylindrical housing main body 10. The cover member 11 is attached to the cylindrical housing main body 10 from the A2 direction side.

[0058] A bearing housing recess 12 for housing a bearing B that rotatably supports a rotary shaft 6 is provided in a housing 1. The bearing housing recess 12 is a circular ring-shaped recess for arranging the bearing B. The bearing housing recess 12 is formed to be recessed from a piston housing area 13 for housing a parking piston portion 7 and a braking piston portion 8 on the inner side of the housing 1 along the rotary shaft 6 in the A2 direction. A biasing member 2 is arranged on the bottom surface of the bearing housing recess 12. That is, the biasing member 2 is arranged between the bottom surface (housing 1) of the bearing housing recess 12 on the A2 direction side and the rotary shaft 6 on the A1 direction side in the axial direction (A direction). Therefore, the bearing B is arranged between the biasing member 2 and the rotary shaft 6 in the axial direction (A direction). In the axial direction (A direction), the bottom surface (housing 1) of the bearing housing recess 12, the bearing B, and the biasing member 2 are always kept in a contacting state.

[0059] An inner bottom surface 13a provided in the housing 1 and located on the A2 direction side of the piston housing area 13 is configured to be in surface contact with a flange portion of a contact portion 64 of the rotary shaft 6 to be described later in a parked state. Details will be described later.

[0060] (Structure of the biasing member)

[0061] As an example, the biasing member 2 is a so-called disc spring. The biasing member 2 is formed in a circular ring shape surrounding the rotary shaft 6 having a central axis C1. The biasing member 2 extends along an end surface in the A2 direction of the bearing housing recess 12, that is, the bottom surface. The biasing member 2 has relatively high rigidity and is deformed (shrinks in the A direction) only after receiving a large compressive force in the A direction. The biasing member 2 is kept in a non-deformed state during a period including a state where braking of a disc-shaped rotor 9b by the braking piston portion 8 is released during parking. On the other hand, the biasing member 2 is kept in a deformed state during the parked state.

[0062] (Structure of the motor and the transmission gear)

[0063] The motor 3 includes a motor main body 30 and a motor shaft 32 provided with a motor gear 31. The motor 3 is arranged side by side at a position in a direction intersecting the A direction with respect to the rotary shaft 6 as an object for transmitting driving force. That is, the motor 3 is configured not as a direct-acting type that directly rotates the rotary shaft 6 but as an indirect-rotating type for the rotary shaft 6. The transmission gear 4 is arranged between the motor shaft 32 and the rotary shaft 6 in a direction intersecting the A direction. A plurality of transmission gears 4 are provided and configured to decelerate and transmit the output of the motor 3 to the rotary shaft 6. The plurality of transmission gears 4 are supported by bearings (not shown) so as to be rotatable. As an example, the motor gear 31 and the transmission gear 4 are composed of spur gears.

[0064] (Structure of the driven gear and the rotary shaft)

[0065] The driven gear 5 is provided on the rotating shaft 6. The driven gear 5 and the rotating shaft 6 have a common central axis C1. Although it is an example, the driven gear 5 is composed of a spur gear.

[0066] The rotating shaft 6 is a structure for moving the parking piston portion 7 and the braking piston portion 8 in the axial direction (A direction). Specifically, a parking screw portion 60 and a braking screw portion 61 having a common central axis C1 are provided on the rotating shaft 6.

[0067] The parking screw portion 60 is an external (male) thread for parking provided on the outer peripheral surface 62 of the rotating shaft 6 and screwed with the parking piston portion 7. The rotating shaft 6 is formed in a cylindrical shape with an external thread for parking provided on the outer peripheral surface 62. Therefore, an internal (female) thread screwed with the parking screw portion 60 of the rotating shaft 6, that is, the external thread for parking, is provided on the parking piston portion 7. The screwed portion of the parking screw portion 60 and the parking piston portion 7 is composed of a trapezoidal thread 60a. In the parking screw portion 60, a greater frictional force is generated compared to the braking screw portion 61.

[0068] The braking screw portion 61 is an internal (female) thread for braking provided on the inner peripheral surface 63 of the rotating shaft 6 and screwed with the braking piston portion 8. Therefore, an external (male) thread screwed with the braking screw portion 61 of the rotating shaft 6, that is, the internal thread for braking, is provided on the braking piston portion 8. The screwed portion of the braking screw portion 61 and the braking piston portion 8 is composed of a ball screw 61a. The ball screw 61a is configured to be provided on the inner peripheral surface 63 of the rotating shaft 6 and screwed with the braking piston portion 8.

[0069] In the axial direction (A direction), at least a part of the external thread for parking forming the parking screw portion 60 of the rotating shaft 6 and the internal thread for braking forming the braking screw portion 61 of the rotating shaft 6 are formed in an overlapping range.

[0070] Although it is an example, the pitch of the thread teeth in the axial direction of the parking screw portion 60 of the rotating shaft 6 is equal to the pitch of the thread teeth in the axial direction of the braking screw portion 61 of the rotating shaft 6. Of course, the pitch of the thread teeth in the axial direction of the internal thread of the parking piston portion 7 is equal to the pitch of the thread teeth in the axial direction of the external thread of the braking piston portion 8. In addition, the diameter of the internal thread of the parking piston portion 7 is larger than the diameter of the external thread of the braking piston portion 8. In addition, the moving speeds of the parking piston portion 7 and the braking piston portion 8 that move in opposite directions at the same time are equal to each other.

[0071] Therefore, when moving the parking piston portion 7 with the same electric power to press the brake pad 9a against the disc rotor 9b by the parking piston portion 7 and moving the braking piston portion 8 to press the brake pad 9a against the disc rotor 9b by the braking piston portion 8, and comparing the two, the braking piston portion 8 can obtain a faster movement responsiveness. That is, the braking piston portion 8 can move more efficiently than the parking piston portion 7.

[0072] As Figure 2 shown, the rotating shaft 6 is configured to move slightly in a direction (A2 direction) opposite to the pressing direction (A1 direction) of the parking piston portion 7 on the brake pad 9a when receiving the reaction force caused by pressing the brake pad 9a against the disc rotor 9b by the parking piston portion 7.

[0073] The rotating shaft 6 includes an abutting portion 64. The abutting portion 64 is configured to abut against the inner bottom surface 13a of the housing 1 when the rotating shaft 6 moves in a direction opposite to the pressing direction of the brake pad 9a. The abutting portion 64 is a flange portion that extends in a direction intersecting the axial direction and is in surface contact with the inner bottom surface 13a of the housing 1. The abutting portion 64 is formed in an annular shape with the central axis C1 located at the center.

[0074] (Structure of parking piston portion and braking piston portion)

[0075] Figure 2 The shown parking piston portion 7 is configured to move in the axial direction (A1 direction) of the central axis C1 by rotating the rotating shaft 6 in a single rotation direction (R1 direction) in a state of being screwed with the parking screwing portion 60 of the rotating shaft 6 to press the brake pad 9a. When the parking piston portion 7 presses the brake pad 9a, it is in direct contact with the brake pad 9a. Moreover, the parking piston portion 7 is configured to press the contacted brake pad 9a against the disc rotor 9b and lock the rotation of the rotating shaft 6 through the frictional force between the parking screwing portion 60 to switch from the parking release state to the parking state.

[0076] In consideration of the assemblability, the parking piston portion 7 is configured to be divisible into a plurality of components. As a specific example, although not shown, the parking piston portion 7 is configured to be divisible into two components on one side and the other side in the axial direction. A predetermined tilt suppression mechanism including a spring member for suppressing the tilt of the parking piston portion 7 relative to the opposed disc rotor 9b is provided between the two components constituting the parking piston portion 7.

[0077] Figure 3The brake piston portion 8 shown is configured such that when the rotary shaft 6 rotates in the other rotary direction (R2 direction) opposite to one rotary direction (R1 direction) while being screwed with the brake screw portion 61 of the rotary shaft 6, the parking piston portion 7 moves in a direction separating from the brake pad 9a in the axial direction, and moves in the direction (A1 direction) opposite to the parking piston portion 7 along the axial direction of the central axis C1, thereby pressing the brake pad 9a. When the brake piston portion 8 presses the brake pad 9a, it is in direct contact with the brake pad 9a. Further, the brake piston portion 8 is configured to press the contacted brake pad 9a against the disc rotor 9b to brake the disc rotor 9b.

[0078] The pressing force by which the brake piston portion 8 presses the brake pad 9a is smaller than the pressing force by which the parking piston portion 7 presses the brake pad 9a. Although it is an example, the area of the end surface in the A1 direction of the parking piston portion 7, that is, the pressing surface 7a having an annular shape of the brake pad 9a, is larger than the area of the end surface in the A1 direction of the brake piston portion 8, that is, the pressing surface 8a having a circular shape of the brake pad 9a.

[0079] The parking piston portion 7 and the brake piston portion 8 are always screwed with the parking screw portion 60 and the brake screw portion 61 of the rotary shaft 6, respectively. Therefore, the parking piston portion 7 and the brake piston portion 8 move simultaneously as the rotary shaft 6 rotates. Each of the parking screw portion 60 and the brake screw portion 61 of the rotary shaft 6 has helical threads in opposite directions such that the moving directions along the axial direction (A direction) of the parking piston portion 7 and the brake piston portion 8 are always opposite to each other. In short, the parking piston portion 7 has one of a right-handed thread and a left-handed thread, and the brake piston portion 8 has the other of the right-handed thread and the left-handed thread.

[0080] When viewed from the axial direction of the central axis C1, the parking piston portion 7 is formed in an annular shape. When viewed from the axial direction, the brake piston portion 8 is formed in a circular shape disposed inside the parking piston portion 7. That is, the parking piston portion 7 is configured to contact the brake pad 9a at a position farther from the central axis C1 than the brake piston portion 8.

[0081] Although not shown, a prescribed anti-rotation structure for preventing the parking piston portion 7 and the brake piston portion 8 from rotating about the central axis C1 as the rotary shaft 6 rotates is provided in the parking piston portion 7 and the brake piston portion 8. Although it is an example, this anti-rotation structure is a guiding structure formed by engaging convex portions and concave portions extending in the axial direction provided in the parking piston portion 7, the brake piston portion 8, and the housing 1.

[0082] (Structure of Brake Pad and Disc Rotor)

[0083] Figure 1The brake pads 9a and the disc rotor 9b shown are arranged on the A1 direction side of the parking piston portion 7 and the braking piston portion 8. A pair of brake pads 9a are arranged opposite to each other in the axial direction (A direction). The disc rotor 9b is arranged between the pair of brake pads 9a. Outside the housing 1, a tire T is fixed to the disc rotor 9b. That is, the disc rotor 9b is configured to rotate together with the tire T. The pair of brake pads 9a are configured to generate a braking force that reduces the torque of the disc rotor 9b (tire T) or inhibits an increase in torque by being pressed against the disc rotor 9b using the driving force of the motor 3.

[0084] (Regarding the holding force for maintaining the parked state of the electric braking device)

[0085] Refer to Figure 2 The holding force for maintaining the parked state of the electric braking device 100 will be described. The holding force for maintaining the parked state of the electric braking device 100 has two holding forces.

[0086] As the first holding force, as described above, the frictional force between the parking piston portion 7 and the parking screw portion 60 can be cited. The parking piston portion 7 is configured to lock the rotation of the rotating shaft 6 through this frictional force and switch from the parking release state to the parked state.

[0087] As the second holding force, the frictional force between the abutting portion 64, which is configured as a flange portion of the rotating shaft 6, and the housing 1 can be cited. Specifically, the rotating shaft 6 is configured to move in the direction opposite to the pressing direction (A1 direction) of the brake pads 9a, i.e., the A2 direction, against the acting force of the biasing member 2 when receiving the reaction force caused by the brake pads 9a being pressed against the disc rotor 9b by the parking piston portion 7, causing the abutting portion 64 to abut against the housing 1. Moreover, in addition to the frictional force between the parking screw portion 60 and the parking piston portion 7, the abutting portion 64 is configured to maintain the state of locking the rotation of the rotating shaft 6, i.e., the parked state, also through the frictional force with the housing 1.

[0088] More specifically, when the parking piston portion 7 moves in the A1 direction as the rotating shaft 6 rotates and the pressing force for pressing the brake pads 9a against the disc rotor 9b does not become large, a state is reached where the parking piston portion 7 can no longer move in the A1 direction. As a result, due to the reaction force from the disc rotor 9b side, an extremely large force is generated in which the internal thread of the parking piston portion 7 presses the parking screw portion 60 of the rotating shaft 6 in the A2 direction. Moreover, as the above reaction force increases, the force for pressing the parking screw portion 60 of the rotating shaft 6 in the A2 direction also further increases, and when it reaches a magnitude capable of deforming the biasing member 2, the biasing member 2 changes from the non-deformed state (refer to Figure 3 ) to a deformed state that shrinks in the A direction.

[0089] Accordingly, in a manner of overcoming the acting force of the applying member 2 to reduce the gap S between the abutting portion 64 and the inner bottom surface 13a of the housing 1 (refer to Figure 3 ), the rotating shaft 6 slightly moves in the A2 direction. As a result, the abutting portion 64 of the rotating shaft 6 comes into surface contact with the inner bottom surface 13a of the housing 1. The electric braking device 100 is configured to suppress the rotation of the rotating shaft 6 and more reliably maintain the parked state by the frictional force at the surface contact portion between the abutting portion 64 of the rotating shaft 6 and the inner bottom surface 13a of the housing 1.

[0090] (Effect of the First Embodiment)

[0091] In the first embodiment, the following effects can be obtained.

[0092] In the first embodiment, as described above, it includes: a parking piston portion 7 that moves axially along the central axis C1 by rotating the rotating shaft 6 in one rotation direction in a state where it is screwed with the parking screw portion 60 of the rotating shaft 6 to press the brake pad 9a; and a braking piston portion 8 that moves axially together with the parking piston portion 7 in a direction separating from the brake pad 9a by rotating the rotating shaft 6 in another rotation direction opposite to the one rotation direction in a state where it is screwed with the braking screw portion 61 of the rotating shaft 6 to press the brake pad 9a. Accordingly, by switching the rotation direction of the rotating shaft 6 by the motor 3 as a drive source, the parking piston portion 7 can be moved to maintain the parked state. In addition, by switching the rotation direction of the rotating shaft 6 by the motor 3 as a drive source, the braking piston portion 8 can be moved to press the brake pad 9a against the disk-shaped rotor 9b to brake the disk-shaped rotor 9b (tire T). That is, braking and the parked state can be maintained only by one motor 3. Therefore, an electric solenoid for maintaining the parked state as in the prior art is not required. As a result, the number of components of the drive source for braking and parking braking can be reduced.

[0093] In the first embodiment, as described above, the parking screw portion 60 is a parking external thread provided on the outer peripheral surface 62 of the rotating shaft 6 and screwed with the parking piston portion 7, and the braking screw portion 61 is a ball screw 61a provided on the inner peripheral surface 63 of the rotating shaft 6 and screwed with the braking piston portion 8. Accordingly, since the parking piston portion 7 can be screwed with the parking external thread of the rotating shaft 6 from the outer peripheral side, the enlargement of the rotating shaft 6 can be suppressed. In addition, the braking piston portion 8 can smoothly act with respect to the braking screw portion 61 of the rotating shaft 6 through the ball screw 61a, so the responsiveness of the braking piston portion 8 can be improved.

[0094] In the first embodiment, as described above, the housing 1 that houses the rotating shaft 6, the parking piston portion 7, and the braking piston portion 8 is further provided. The rotating shaft 6 is configured to move in a direction opposite to the pressing direction of the parking piston portion 7 on the brake pad 9a when receiving the reaction force caused by the parking piston portion 7 pressing the brake pad 9a against the disc-shaped rotor 9b. The rotating shaft 6 includes a contact portion 64 that contacts the housing 1 when the rotating shaft 6 moves in a direction opposite to the pressing direction. In addition to the frictional force between the parking screw portion 60 and the parking piston portion 7, the contact portion 64 is configured to also maintain the state of locking the rotation of the rotating shaft 6, that is, the parking state, through the frictional force with the housing 1. Thus, the contact portion 64 that contacts the housing 1 can further increase the holding force for maintaining the parking state, so the parking state can be maintained more stably.

[0095] In the first embodiment, as described above, the parking piston portion 7 and the braking piston portion 8 are configured to directly contact the brake pad 9a to press the brake pad 9a. The parking piston portion 7 is formed in an annular shape when viewed from the axial direction of the central axis C1, and the braking piston portion 8 is formed in a circular shape that is disposed inside the parking piston portion 7 when viewed from the axial direction. Thus, compared with the screwed portion between the braking piston portion 8 and the rotating shaft 6, the screwed portion between the parking piston portion 7 and the rotating shaft 6 can be disposed on the outside (outer peripheral side), so the radial distance from the central axis C1 of the rotating shaft 6 to the screwed portion between the parking piston portion 7 and the rotating shaft 6 can be ensured to be large, and the lead angle of the threads of the parking screw portion 60 can be reduced. As a result, the frictional force of the parking screw portion 60 can be increased.

[0096] In the first embodiment, as described above, the rotating shaft 6 is formed in a cylindrical shape with an external thread for parking provided on the outer peripheral surface 62. The braking screw portion 61 is an internal thread for braking that is provided on the inner peripheral surface 63 of the rotating shaft 6 and is screwed with the braking piston portion 8. In the axial direction, at least a part of the external thread for parking and the internal thread for braking of the rotating shaft 6 are formed in an overlapping range. Thus, in the axial direction, the external thread for parking of the rotating shaft 6 and the internal thread for braking of the rotating shaft 6 can be overlapped, so the size of the rotating shaft 6 in the axial direction can be reduced, and the device can be miniaturized in the axial direction.

[0097] In the first embodiment, as described above, there is also a biasing member 2 disposed axially between the housing 1 and the rotary shaft 6. The rotary shaft 6 is configured to move in a direction opposite to the pressing direction of the brake pad 9a when receiving a reaction force caused by the parking piston portion 7 pressing the brake pad 9a against the disc-shaped rotor 9b, overcoming the acting force of the biasing member 2, and bringing the abutting portion 64 into contact with the housing 1. Thus, when the rotary shaft 6 receives a reaction force caused by the parking piston portion 7 pressing the brake pad 9a against the disc-shaped rotor 9b through the biasing member 2, the abutting portion 64 of the rotary shaft 6 can be brought into contact with the housing 1 in such a way that the biasing member 2 starts to deform. That is, when the rotary shaft 6 is braked by receiving a relatively small reaction force from the side of the braking piston portion 8, the deformation of the biasing member 2 and the contact of the abutting portion 64 of the rotary shaft 6 with the housing 1 can be suppressed.

[0098] In the first embodiment, as described above, the abutting portion 64 is a flange portion that extends in a direction intersecting the axial direction and is in surface contact with the inner bottom surface 13a of the housing 1. Thus, through the abutting portion 64 constituted by the flange portion, a relatively large contact area between the rotary shaft 6 that generates a holding force for maintaining the parked state and the housing 1 can be ensured. As a result, a greater holding force for maintaining the parked state can be generated.

[0099] (Second Embodiment)

[0100] Refer to Figure 4 The second embodiment will be described. In this second embodiment, an example will be described in which, unlike the first embodiment in which the braking screw portion 61 of the rotary shaft 6 that is screwed with the braking piston portion 8 is formed by an internal (female) thread, the braking screw portion 261 that is screwed with the braking piston portion 208 is formed by an external (male) thread. In addition, in the drawings, the same reference numerals are used to denote the same structures as those in the first embodiment and are illustrated.

[0101] The electric braking device 200 of the second embodiment includes a rotary shaft 206 and a piston 201. The piston 201 includes a parking piston portion 207 and a braking piston portion 208.

[0102] The rotary shaft 206 includes a parking screw portion 60 formed by a parking internal thread and a braking screw portion 261 formed by a braking internal thread.

[0103] The braking screw portion 261 is a braking external thread provided on the outer peripheral surface 62 of the rotary shaft 206 and screwed with the braking piston portion 208.

[0104] The rotating shaft 206 includes a parking rotating shaft portion 206a provided with an external thread for parking that forms a screwing portion 60 for parking. Further, the rotating shaft 206 includes a braking rotating shaft portion 206b connected to one end 206c in the axial direction (A1 direction) of the parking rotating shaft portion 206a and provided with an external thread for braking that forms a screwing portion 261 for braking.

[0105] The diameter of the parking rotating shaft portion 206a is larger than the diameter of the braking rotating shaft portion 206b. Accordingly, the rotating shaft 206 is formed in a stepped shape that tapers toward the A1 direction side by the parking rotating shaft portion 206a and the braking rotating shaft portion 206b. In the axial direction, the external thread for parking that forms the screwing portion 60 for parking of the rotating shaft 206 and the external thread for braking that forms the screwing portion 261 for braking of the rotating shaft 206 are formed in non-overlapping ranges.

[0106] The parking piston portion 207 has an internal thread that engages with the screwing portion 60 (external thread for parking) of the rotating shaft 206. The braking piston portion 208 has an internal thread that engages with the screwing portion 261 (external thread for braking) of the rotating shaft 206.

[0107] Other configurations of the second embodiment are the same as those of the first embodiment described above.

[0108] (Effects of the Second Embodiment)

[0109] In the second embodiment, the following effects can be obtained.

[0110] In the second embodiment, as described above, there is provided a parking piston portion 207 that moves axially in the direction of the central axis C1 by rotating the rotating shaft 206 in one rotation direction in a state where it is engaged with the screwing portion 60 for parking of the rotating shaft 206, to press the brake pad 9a; and a braking piston portion 208 that moves axially together with the parking piston portion 207 in a direction separating from the brake pad 9a in the axial direction by rotating the rotating shaft 206 in another rotation direction opposite to the one rotation direction in a state where it is engaged with the screwing portion 261 for braking of the rotating shaft 206, to press the brake pad 9a. Thereby, as in the first embodiment described above, the number of components of the drive source for braking and parking braking can be reduced.

[0111] In the second embodiment, as described above, the threaded portion 261 for braking is an external thread for braking provided on the outer peripheral surface 62 of the rotary shaft 206 and screwed with the piston portion 208 for braking. The rotary shaft 206 includes a rotary shaft portion 206a for parking provided with an external thread for parking; and a rotary shaft portion 206b for braking connected to one axial end 206c of the rotary shaft portion 206a for parking and provided with an external thread for braking. Axially, the external thread for parking and the external thread for braking are formed in non-overlapping ranges. Thus, the piston portion 207 for parking and the piston portion 208 for braking can be arranged on the outer peripheral side of the rotary shaft 206, so that the size of the rotary shaft 206 in the direction intersecting the axial direction can be reduced, and the device can be miniaturized in the direction intersecting the axial direction.

[0112] Other effects of the second embodiment are the same as those of the first embodiment described above.

[0113] (Third Embodiment)

[0114] Refer to Figure 5 and Figure 6 The third embodiment will be described. In this third embodiment, different from the first embodiment in which there are two components that directly contact the brake block 9a from the rotary shaft 6 side, an example in which there is one component that directly contacts the brake block 9a from the rotary shaft 6 side will be described. In addition, in the drawings, the same reference numerals are used to denote the same structures as those in the first embodiment and are illustrated.

[0115] Figure 5 and Figure 6 The electric braking device 300 of the third embodiment shown in and includes a rotary shaft 6, a piston 301, a biasing member 302, and a sealing member 303. The piston 301 includes a piston portion 307 for parking, a piston portion 308 for braking, and a pad contact member 309.

[0116] The piston portion 307 for parking is configured to press the brake block 9a by moving in the axial direction (A1 direction) of the central axis C1 when the rotary shaft 6 rotates in one rotation direction (R1 direction) about the central axis C1 in a state of being screwed with the threaded portion 60 for parking. The piston portion 307 for parking has the central axis C1 disposed at the center and is formed in a cylindrical shape extending along the A direction. The piston portion 307 for parking has a portion in contact with the pad contact member 309, that is, a flange-shaped contact portion 307a, at the end in the A1 direction. In addition, a guide portion 307b is provided on the contact portion 307a. The guide portion 307b is configured to limit the rotation of the piston portion 307 for parking relative to the pad contact member 309 about the central axis C1 and guide the movement of the piston portion 307 for parking in the A direction.

[0117] The piston portion 308 for braking is configured such that, in a state of being screwed with the screw portion 61 for braking, when the rotary shaft 6 rotates in the other rotational direction (R2 direction) opposite to one rotational direction around the central axis C1, it moves in the direction (A1 direction) opposite to the parking piston portion 307 along the axial direction of the central axis C1 to press the brake pad 9a. The piston portion 308 for braking always moves in the direction opposite to the pad contact member 309 simultaneously with the movement of the pad contact member 309 in the A direction. The piston portion 308 for braking is formed in a cylindrical shape extending in the A direction along the central axis C1. The end portion of the piston portion 308 for braking in the A1 direction has a portion in contact with the pad contact member 309, that is, a flange-shaped contact portion 308a. Further, a guide portion 308b is provided on the contact portion 308a. The guide portion 308b is configured to restrict the rotation of the piston portion 308 for braking around the central axis C1 with respect to the pad contact member 309 and guide the movement of the piston portion 308 for braking in the A direction.

[0118] The pad contact member 309 is a single structure that contacts the brake pad 9a. The pad contact member 309 is provided as a common structure for the parking piston portion 307 and the piston portion 308 for braking so as to cover the parking piston portion 307 and the piston portion 308 for braking from the brake pad 9a side. The end portion of the pad contact member 309 in the A1 direction is closed and formed in a hollow cylindrical shape with an open end portion in the A2 direction. That is, the pad contact member 309 is formed in a shape like a lateral cup with the opening portion arranged on the A2 direction side. The cylindrical pad contact member 309 has the central axis C1 disposed at the center. The pad contact member 309 is fitted to the inner peripheral surface of the housing 1 in a state capable of moving in the A direction. A guide portion (not shown) for restricting the rotation of the pad contact member 309 around the central axis C1 with respect to the housing 1 and guiding the movement of the pad contact member 309 in the A direction is provided on the outer peripheral surface of the pad contact member 309.

[0119] The parking piston portion 307 and the piston portion 308 for braking are configured to contact the brake pad 9a via the pad contact member 309 and press the brake pad 9a.

[0120] Here, the electric braking device 300 is set to a state where braking by the piston portion 308 for braking is not performed, and a parking release state where locking of the disc rotor 9b (tire T (refer to Figure 1 )) by the parking piston portion 307 is not performed. This state is set as the neutral state.

[0121] A case where the state is switched from the neutral state to the braking state (a state in which the disk-shaped rotor 9b (tire T) is braked) will be described. In this case, the rotating shaft 6 rotates in the other rotating direction (R2 direction) opposite to one rotating direction around the central axis C1. As a result, the braking piston portion 308 moves in the A1 direction toward the brake pad 9a. At the same time, the parking piston portion 307 moves in the A2 direction. Further, the braking piston portion 308 pushes the pad contact member 309 forward in the A1 direction while contacting the pad contact member 309. As a result, the braking piston portion 308 contacts the brake pad 9a via the pad contact member 309 and presses the brake pad 9a.

[0122] Next, a case where the state is switched from the neutral state (parking release state) to the parking state will be described. In this case, the rotating shaft 6 rotates in one rotating direction (R1 direction) around the central axis C1. As a result, the parking piston portion 307 moves in the A1 direction toward the brake pad 9a. At the same time, the braking piston portion 308 moves in the A2 direction. Further, the parking piston portion 307 pushes the pad contact member 309 forward in the A1 direction while contacting the pad contact member 309. As a result, the parking piston portion 307 contacts the brake pad 9a via the pad contact member 309 and presses the brake pad 9a. Further, when the rotating shaft 6 rotates further and presses the pad contact member 309 against the brake pad 9a with a greater force via the parking piston portion 307, the parking piston portion 307 is pressed in the A2 direction by the reaction force from the brake pad 9a. The rotating shaft 6 is also pressed in the A2 direction by this reaction force. Further, when this reaction force is greater than the acting force of the biasing member 2, the contact portion 64 of the rotating shaft 6 moves in the A2 direction to contact the housing 1, overcoming the acting force of the biasing member 2. Although this is an example, the biasing member 2 is formed of a compression coil spring.

[0123] The biasing member 302 is configured to bias the parking piston portion 307 and the braking piston portion 308 toward the brake pad 9a in the A1 direction, and to bias the pad contact member 309 in the direction opposite to the parking piston portion 307 and the braking piston portion 308 (the A2 direction). The biasing member 302 is disposed inside the pad contact member 309. The biasing member 302 is formed of an elastic member that generates a biasing force in the A direction. Although it is an example, the biasing member 302 is formed of a compression coil spring. The biasing member 302 has its central axis C1 disposed at the center. The end portion of the biasing member 302 in the A2 direction abuts against the pad contact member 309, and the end portion in the A1 direction abuts against the parking piston portion 307. That is, the biasing member 302 always presses the pad contact member 309 in the A2 direction and always presses the parking piston portion 307 in the A1 direction. In short, the biasing member 302 always applies a pressure toward the outside in the A direction between the pad contact member 309 and the parking piston portion 307 to the pad contact member 309 and the parking piston portion 307. In addition, the braking piston portion 308 is connected to the parking piston portion 307 via a rotating shaft 6 that can move slightly in the A direction. Therefore, the braking piston portion 308 also always receives a pressure in the A1 direction from the biasing member 302.

[0124] The pad contact member 309 always receives a pressing force that presses the pad contact member 309 in the A2 direction against the parking piston portion 307 through the biasing member 302. This pressing force is a force that is balanced around the central axis C1. When moving the parking piston portion 307 and the braking piston portion 308 and switching the usage states of the parking piston portion 307 and the braking piston portion 308, etc., this balanced pressing force can prevent gaps from occurring in the pad contact member 309, the parking piston portion 307, and the braking piston portion 308.

[0125] In addition, when rotating the rotating shaft 6 and returning from the parking state to the above neutral state, through the biasing member 302, the pad contact member 309 moves in the A2 direction together with the parking piston portion 307. Similarly, when rotating the rotating shaft 6 and returning from the braking state to the above neutral state, through the biasing member 302, the pad contact member 309 moves in the A2 direction together with the braking piston portion 308.

[0126] The sealing member 303 is provided at the interface E between the outer peripheral surface of the pad contact member 309 and the inner peripheral surface of the housing 1. That is, the sealing member 303 is provided at the position where intrusion of foreign matters, etc., into the device should be prevented, namely the interface E. In the electric braking device 300, the interface E where the sealing member 303 should be provided to prevent intrusion of foreign matters, etc., from the outside is only one position between the pad contact member 309 and the housing 1.

[0127] Although it is an example, the sealing member 303 includes a corrugated seal 303a disposed at the end of the housing 1 in the A1 direction. The corrugated seal 303a is formed of an elastic member. The corrugated seal 303a is formed in an annular shape with the central axis C1 disposed at the center. One end of the corrugated seal 303a is provided in a recess on the outer peripheral surface of the gasket contact member 309, and the other end is provided in a recess on the inner peripheral surface of the housing 1. And, although it is an example, the sealing member 303 includes a rectangular seal 303b disposed on the A2 direction side of the corrugated seal 303a at the interface E. The rectangular seal 303b is formed in an annular shape with the central axis C1 disposed at the center. The rectangular seal 303b is formed of an elastic member.

[0128] Other configurations of the third embodiment are the same as those of the first embodiment described above.

[0129] (Effects of the third embodiment)

[0130] In the third embodiment, the following effects can be obtained.

[0131] In the third embodiment, as described above, there is provided a parking piston portion 307 which, when the rotary shaft 6 rotates in one rotational direction in a state of being screwed with the parking screw portion 60 of the rotary shaft 6, moves axially in the direction of the central axis C1 to press the brake pad 9a; and a braking piston portion 308 which, when the rotary shaft 6 rotates in another rotational direction opposite to the one rotational direction in a state of being screwed with the braking screw portion 61 of the rotary shaft 6, moves axially together with the parking piston portion 307 in the direction of separating from the brake pad 9a to press the brake pad 9a. Thus, as in the first embodiment described above, the number of components of the drive source for braking and parking braking can be reduced.

[0132] In the third embodiment, as described above, the piston 301 includes a single gasket contact member 309 which is provided in a common structure for the parking piston portion 307 and the braking piston portion 308 so as to cover the parking piston portion 307 and the braking piston portion 308 from the brake pad 9a side, and contacts the brake pad 9a. The parking piston portion 307 and the braking piston portion 308 are configured to contact the brake pad 9a via the gasket contact member 309 to press the brake pad 9a. Thus, compared with the case of pressing the brake pad 9a by switching a plurality of components, a larger contact area between the brake pad 9a and the component for pressing the brake pad 9a, that is, the gasket contact member 309, can be ensured. Therefore, a frictional force can be effectively generated between the gasket contact member 309 and the brake pad 9a to maintain the braking and parking states.

[0133] In the third embodiment, as described above, there is also a biasing member 302 that biases the parking piston portion 307 and the braking piston portion 308 toward the brake pad 9a, and biases the pad contact member 309 in a direction opposite to that of the parking piston portion 307 and the braking piston portion 308. Thus, the biasing member 302 can apply pressure to the parking piston portion 307, the braking piston portion 308, and the pad contact member 309 in a direction in which they separate from each other. Therefore, when switching between the braking state and the parking state, etc., it is possible to suppress a situation where gaps are generated in the positions among the pad contact member 309, the parking piston portion 307, and the braking piston portion 308.

[0134] Other effects of the third embodiment are the same as those of the first embodiment described above.

[0135] (Modification example)

[0136] It should be considered that the embodiments disclosed this time are illustrative in all aspects and not restrictive. The scope of the present invention is shown not by the description of the above embodiments but by the claims, and includes all changes (modification examples) within the meaning and scope equivalent to the claims.

[0137] For example, in the first to third embodiments described above, although an example of a braking screw portion formed by an external (male) thread for braking is shown, the present invention is not limited to this. In the present invention, it may also be as Figure 7 in the electric braking device 400 of the first modification example shown, where a braking screw portion 461 formed by an internal (female) thread for braking forms the rotating shaft 406.

[0138] In addition, in the first and second embodiments described above, although an example of forming the parking piston portion in an annular shape and disposing the braking piston portion inside the parking piston portion is shown, the present invention is not limited to this. In the present invention, it may also be as Figure 8 in the electric braking device 500 of the second modification example shown, where the braking piston portion 508 is formed in an annular shape and the parking piston portion 507 is disposed inside the braking piston portion 508. In this case, although it is an example, the rotating shaft is formed in the same stepped shape as in the second embodiment described above.

[0139] In addition, it may also be as Figure 9 in the electric braking device 600 of the third modification example shown, where a parking screw portion 660 formed by an internal (female) thread for parking forms the rotating shaft 606, and the braking piston portion 608 is formed in an annular shape and the parking piston portion 607 is disposed inside the braking piston portion 608.

[0140] In addition, in the above-described first to third embodiments, although an example in which at least one of the screwing portions for parking and the screwing portion for braking the rotating shaft is formed by an external (male) thread is shown, the present invention is not limited thereto. In the present invention, both the screwing portion for parking the rotating shaft and the screwing portion for braking the rotating shaft may be formed by an internal (female) thread.

[0141] In addition, in the above-described first to third embodiments, although an example in which a ball screw is used for the screwing portion for braking the rotating shaft is shown, the present invention is not limited thereto. In the present invention, a sliding thread, a trapezoidal thread, or the like may be used for the screwing portion for braking the rotating shaft.

[0142] In addition, in the above-described first to third embodiments, although an example in which a trapezoidal thread is used for the screwing portion for parking the rotating shaft is shown, the present invention is not limited thereto. In the present invention, a sliding thread, a ball screw, or the like may be used for the screwing portion for parking the rotating shaft.

[0143] In addition, in the above-described first to third embodiments, although an example in which the driving force of the motor is indirectly transmitted to the rotating shaft via a plurality of transmission gears is shown, the present invention is not limited thereto. In the present invention, the driving force of the motor may be directly transmitted to the rotating shaft without passing through the transmission gears.

[0144] In addition, in the above-described first and second embodiments, although an example in which a biasing member that biases the rotating shaft is constituted by a disc spring is shown, the present invention is not limited thereto. In the present invention, a biasing member that biases the rotating shaft may be constituted by a coil spring, a rubber member, or the like.

[0145] In addition, in the above-described first to third embodiments, although an example in which the parking piston portion moves in the A1 direction when the motor rotates forward is shown, the present invention is not limited thereto. In the present invention, the parking piston portion may be configured to move in the A2 direction when the motor rotates forward.

[0146] In addition, in the above-described first and second embodiments, although an example in which the parking piston portion is formed in an annular shape is shown, the present invention is not limited thereto. In the present invention, the parking piston portion may be formed in a C-shaped or the like.

[0147] In addition, in the above-described first to third embodiments, although an example in which the electric braking device includes a biasing member that biases the rotating shaft is shown, the present invention is not limited thereto. In the present invention, the electric braking device may not include a biasing member that biases the rotating shaft.

Claims

1. An electric braking device, wherein, Comprising: A motor; A rotating shaft which is provided such that a parking engagement portion and a braking engagement portion have a common central axis and is rotated by the above motor; and A piston which includes: a parking piston portion that presses a brake pad by moving axially in the direction of the central axis when the rotating shaft rotates in one rotational direction in a state of being engaged with the parking engagement portion; and a braking piston portion that presses the brake pad by moving axially together with the parking piston portion moving in a direction separating from the brake pad in the axial direction when the rotating shaft rotates in another rotational direction opposite to the one rotational direction in a state of being engaged with the braking engagement portion.

2. The electric braking device according to claim 1, wherein The piston includes a single pad contact member which is provided as a common structure for the parking piston portion and the braking piston portion so as to cover the parking piston portion and the braking piston portion from the brake pad side and contacts the brake pad, The parking piston portion and the braking piston portion are configured to press the brake pad by contacting the brake pad via the pad contact member.

3. The electric braking device according to claim 1, wherein The parking engagement portion is a parking external thread provided on the outer peripheral surface of the rotating shaft and engaged with the parking piston portion, The braking engagement portion is a ball screw provided on the inner peripheral surface of the rotating shaft and engaged with the braking piston portion.

4. The electric braking device according to claim 1, wherein, It further includes a housing that houses the rotating shaft, the parking piston portion, and the braking piston portion, The rotating shaft is configured to move in a direction opposite to the pressing direction of the parking piston portion on the brake pad when receiving a reaction force caused by the parking piston portion pressing the brake pad against a disc rotor, The rotating shaft includes an abutting portion that abuts against the housing when the rotating shaft moves in a direction opposite to the pressing direction.

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