Electric brake device

Abstract

The invention provides an electric brake device having a parking brake mechanism which is good in controllability, simple in structure and small in size. A parking brake mechanism provided in the disc brake is provided with a solenoid actuator as a switching mechanism that moves a large-diameter gear of a second reduction gear and a first reduction gear relative to each other in the axial direction of the large-diameter gear and the first reduction gear. The presence or absence of a gap between a tooth thickness portion of the large-diameter gear of the second reduction gear and each tooth portion of the first reduction gear 34 is generated. As a result, the parking brake mechanism has good controllability and a simple structure, and can be reduced in size.

Description

Technical Field

[0001] The present disclosure relates to an electric brake device for braking a vehicle. Background Art

[0002] For example, in the disc brake (electric brake device) described in Patent Document 1, when the parking brake is applied, power is supplied to the solenoid actuator, causing the plunger of the solenoid actuator to sink, causing the claw of the retaining member to move toward the outer peripheral surface of the ratchet wheel against the force of the compression coil spring, engaging with the gear portion, and maintaining the brake state. At this time, since the tops of the ratchet wheel's gear portion and the retaining member's claw portion may interfere with each other and not engage, the electric motor is rotated in the brake release direction to ensure proper alignment, causing the ratchet wheel's gear portion and the retaining member's claw portion to reliably engage.

[0003] Prior art literature

[0004] Patent Document 1: (Japan) Patent No. 7220281 Summary of the Invention

[0005] Technical problem to be solved by the invention

[0006] However, in the disc brake described in Patent Document 1, actuating the parking brake requires the solenoid actuator and electric motor to be operated in stages to align the gear portion of the ratchet wheel with the claw portion of the retaining member, complicating control and creating controllability issues. Furthermore, the disc brake described in Patent Document 1 requires a ratchet wheel, a retaining member, a locking member, and a compression coil spring as the parking brake mechanism, leading to problems such as a highly complex structure and layout and an increased size.

[0007] Furthermore, in view of the above-mentioned problems, an object of the present invention is to provide an electric brake device including a parking brake mechanism having good controllability, a simple structure, and a downsizing.

[0008] Technical solutions to technical problems

[0009] As a solution to the above-mentioned problems, the electric brake device of the present invention comprises: an electric motor; a reduction mechanism that amplifies the rotational torque from the electric motor; and a parking brake mechanism that converts the rotation from the reduction mechanism into linear motion, maintaining a pressing force that presses the braking component toward the braked component, the reduction mechanism having a first gear and a second gear meshing with the first gear, and a gap between the teeth of the first gear and the teeth of the second gear along the rotation direction, and the parking brake mechanism having a switching mechanism that causes the first gear and the second gear to move relative to each other along their axial directions, and the presence or absence of the gap is generated by the action of the switching mechanism.

[0010] The parking brake mechanism included in the electric brake device according to one embodiment of the present invention has good controllability, a simple structure, and can be miniaturized. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a partial cross-sectional view of the disc brake according to this embodiment.

[0012] Figure 2 It is an enlarged cross-sectional view of a main part of the disc brake according to this embodiment.

[0013] Figure 3 This is an exploded perspective view of the parking brake mechanism employed in the disc brake of this embodiment.

[0014] Figure 4 It is a perspective view of a parking brake mechanism adopted in the disc brake of this embodiment.

[0015] Figure 5 This is a cross-sectional view showing a state in which a plunger of a solenoid actuator is mounted on a second reduction gear employed in the disc brake according to the present embodiment.

[0016] Figure 6 This is a cross-sectional view perpendicular to the radial direction of each tooth portion including a tooth thick portion of the large-diameter gear of the second reduction gear employed in the disc brake of the present embodiment.

[0017] Figure 7 This is a cross-sectional view perpendicular to the radial direction showing a state in which each tooth portion including a thick tooth portion of the large-diameter gear of the second reduction gear employed in the disc brake of the present embodiment is engaged with each tooth portion of the first reduction gear.

[0018] Figure 8 It is from Figure 7 A cross-sectional view perpendicular to the radial direction showing a state in which the second reduction gear moves axially relative to the first reduction gear by the action of the solenoid actuator starting from the state of

[0019] Figure 9 It is a cross-sectional view of the switch mechanism according to the second embodiment.

[0020] Figure 10 It is a cross-sectional view perpendicular to the radial direction, showing a state in which each tooth portion including a tooth thick portion of another embodiment of the large-diameter gear of the second reduction gear is meshed with each tooth portion of the first reduction gear.

[0021] Figure 11 It is from Figure 10 A cross-sectional view perpendicular to the radial direction showing a state in which the second reduction gear moves axially relative to the first reduction gear by the action of the solenoid actuator starting from the state of

[0022] Figure 12 It is a cross-sectional view perpendicular to the radial direction of a state in which each tooth portion including a tooth thick wall portion of another embodiment of the large-diameter gear of the second reduction gear is meshed with each tooth portion of the first reduction gear.

[0023] Figure 13 It is from Figure 12 A cross-sectional view perpendicular to the radial direction showing a state in which the second reduction gear moves axially relative to the first reduction gear by the action of the solenoid actuator starting from the state of

[0024] Figure 14 This is a cross-sectional view perpendicular to the radial direction, showing a state in which each tooth portion including a tooth thick portion according to another embodiment of the large-diameter gear of the second reduction gear is engaged with each tooth portion of the first reduction gear.

[0025] Figure 15 It is from Figure 14 A cross-sectional view perpendicular to the radial direction showing a state in which the second reduction gear moves axially relative to the first reduction gear by the action of the solenoid actuator starting from the state of DETAILED DESCRIPTION

[0026] The following is based on Figures 1 to 15 This embodiment will be described in detail.

[0027] The electric brake device of this embodiment, specifically the disc brake 1, generates braking force by driving the electric motor 27 during normal driving. It should be noted that in the following description, the vehicle inner side (inside) is referred to as one end side, and the vehicle outer side (outside) is referred to as the other end side. Figure 1 and Figure 2 In the description, the right side is referred to as one end side, and the left side is referred to as the other end side, and appropriate description is given.

[0028] Reference Figure 1 The disc brake 1 of this embodiment includes a pair of inner and outer brake pads 2 and 3, and a brake caliper 4, arranged axially on opposite sides of a disc rotor D mounted on a rotating part of a vehicle. This disc brake 1 is a floating caliper type. The inner and outer brake pads 2 and 3, along with the brake caliper 4, are supported so as to be movable axially along the disc rotor D relative to a bracket 5 fixed to a non-rotating part of the vehicle, such as a steering knuckle. The disc rotor D represents the braked component, while the inner and outer brake pads 2 and 3 represent the braking component.

[0029] Reference Figure 1The brake caliper 4 includes a caliper body 8, which is the main body of the caliper 4; a transmission mechanism 9, which transmits the rotation from the electric motor 27 to the piston 18 in the cylinder portion 13 of the caliper body 8, thereby applying thrust to the piston 18. The caliper body 8 includes a cylindrical cylinder portion 13, which is located at the base end facing the inner brake pad 2 and is open to face the inner brake pad 2; and a pair of claws 14, 14, which extend outward from the cylinder portion 13 across the disc rotor D and are located at the front end facing the outer brake pad 3.

[0030] A piston 18 is housed within the cylinder portion 13 of the caliper body 8, specifically within the bore 16 of the cylinder portion 13, in a manner that prevents relative rotation relative to the cylinder portion 13 but allows axial movement. The piston 18 presses against the inner brake pad 2 and is formed into a bottomed, cup-shaped structure. The piston 18 is housed within the bore 16 of the cylinder portion 13, with its bottom facing the inner brake pad 2. The piston 18 is supported in a manner that prevents relative rotation relative to the cylinder bore 16, and thus the caliper body 8, due to a non-rotatable engagement between its bottom and the inner brake pad 2.

[0031] A sealing member (not shown) is disposed on the inner circumferential surface of the other end of the cylinder bore 16 of the cylinder portion 13. The piston 18 is housed in the cylinder bore 16, axially movable, in contact with the sealing member. A dust cover 20 is interposed between the outer circumferential surface of the bottom side of the piston 18 and the inner circumferential surface of the other end of the cylinder bore 16. These sealing members and the dust cover 20 prevent foreign matter from entering the cylinder bore 16 of the cylinder portion 13. Furthermore, a gear box 25 is integrally connected to the bottom wall 23 (one end) of the cylinder portion 13 of the caliper body 8. Inside this gear box 25, an electric motor 27, a spur gear multi-stage reduction mechanism 29, and a planetary gear reduction mechanism 30 (described later) are housed. The opening at one end of the gear box 25 is sealed by a cover member (not shown). This cover member is airtightly attached to the gear box 25.

[0032] The rotation from the electric motor 27 is transmitted to the piston 18 via the transmission mechanism 9. The transmission mechanism 9 includes: a spur gear multi-stage reduction mechanism 29 and a planetary gear reduction mechanism 30, which amplify the rotation torque from the electric motor 27; and a rotation-to-linear conversion mechanism 31, which converts the rotation from the planetary gear reduction mechanism 30 into linear motion, thereby applying thrust to the piston 18. The electric motor 27 is arranged in the gear box 25, and its rotation shaft 27A extends toward one end side. Figure 2 The spur multi-stage reduction mechanism 29 includes a first reduction gear 34, a second reduction gear 35, and a third reduction gear 36. The second reduction gear 35 and the third reduction gear 36 are made of metal or resin such as fiber-reinforced resin. It should be noted that the first reduction gear 34 is equivalent to the first gear.

[0033] Reference Figures 2 to 5, the first reduction gear 34 is formed in a cylindrical shape and is pressed into and fixed to the rotating shaft 27A of the electric motor 27. The second reduction gear 35 is composed of a stepped gear. The second reduction gear 35 includes: a large diameter gear 38 with a large diameter, which meshes with the first reduction gear 34; and a small diameter gear 39 with a small diameter, which extends axially from the large diameter gear 38 in a concentric shape toward one end side. It should be noted that the large diameter gear 38 of the second reduction gear 35 is equivalent to the second gear. The structure of the parking brake mechanism 60 having the switch mechanism 43A (solenoid actuator 45) of the first embodiment is described below. Refer to Figure 3 and Figure 5 A mounting hole 41 is provided in the radial center of the second reduction gear 35. The mounting hole 41 extends axially therethrough. A plunger 48 of a solenoid actuator 45 serving as the switch mechanism 43A of the first embodiment is rotatably inserted into the mounting hole 41 of the second reduction gear 35.

[0034] A pair of retaining rings 42 are provided on the plunger 48 of the solenoid actuator 45 at positions that clamp the second reduction gear 35 in the axial direction of the second reduction gear 35. The axial movement of the plunger 48 relative to the second reduction gear 35 is restricted by the pair of retaining rings 42, 42. In addition, the second reduction gear 35 is rotatably supported on the plunger 48 of the solenoid actuator 45. The solenoid actuator 45 adopts a bidirectional holding type in which the position of the plunger 48 can be maintained by a permanent magnet after the plunger 48 moves forward and backward. As a result, after the parking brake is actuated, the parking state can be maintained even if the power to the solenoid actuator 45 is released. Refer to Figure 1 and Figure 2 The main body 47 of the solenoid actuator 45 is arranged on one end side.

[0035] Reference Figure 5 as well as Figure 6 Each tooth portion 50 of the large diameter gear 38 of the second reduction gear 35 is formed with a tooth thick wall portion 53A, and the tooth thick wall portion 53A is formed so that the chordal tooth thickness is larger on one end side in the tooth line direction. Figure 2 One end side in the tooth trace direction is the same as one end side of the disc brake 1 and becomes the main body 47 side of the solenoid actuator 45. Figure 5 and Figure 6 The tooth thickness wall portion 53A is configured such that tapered surfaces 55, 55 are formed on both tooth surfaces, wherein the chordal tooth thickness increases toward one end in the tooth line direction. Figure 8 The maximum chordal tooth thickness of the tooth thick wall portion 53A is set to be larger than the distance (tooth groove width) between adjacent tooth portions 51, 51 of the first reduction gear 34. Figure 7 and Figure 8The tooth width (length in the tooth trace direction) of each tooth portion 50 of the large diameter gear 38 of the second reduction gear 35 is set to be larger than the tooth width (length in the tooth trace direction) of the tooth portion 51 of the first reduction gear 34 by an amount corresponding to the tooth width of the tooth thick wall portion 53A.

[0036] And, refer to Figure 7 During normal operation, when the solenoid actuator 45 is not actuated, the teeth 50 including the thick tooth portion 53A of the large diameter gear 38 of the second reduction gear 35 mesh with the teeth 51 of the first reduction gear 34, creating gaps 58 between the teeth 50 of the large diameter gear 38 of the second reduction gear 35 and the teeth 51 of the first reduction gear 34. As a result, the teeth 50 including the thick tooth portion 53A of the large diameter gear 38 of the second reduction gear 35 and the teeth 51 of the first reduction gear 34 can slide relative to each other, thereby enabling transmission of rotational torque therebetween.

[0037] On the other hand, refer to Figure 8 When the parking brake is applied, the solenoid actuator 45 operates, causing the plunger 48 to advance (protrude) toward the other end, causing the second reduction gear 35 to advance axially relative to the first reduction gear 34. Consequently, the tooth thickening portions 53A of the large-diameter gear 38 of the second reduction gear 35, specifically the tapered surfaces 55, 55 of each tooth thickening portion 53A, come into contact with the teeth 51 of the first reduction gear 34, eliminating the gap 58. As a result, the rotation of the second reduction gear 35 and the first reduction gear 34 is restricted, maintaining the parking brake state.

[0038] In addition, when the parking brake is released, the solenoid actuator 45 is actuated to retract the plunger 48 to the initial state, causing the second reduction gear 35 to retract axially relative to the first reduction gear 34. Figure 7 As shown, the teeth 50 including the thick tooth portion 53A of the large diameter gear 38 of the second reduction gear 35 and the teeth 51 of the first reduction gear 34 return to their initial state with a gap 58 formed therebetween. As a result, the teeth 50 including the thick tooth portion 53A of the large diameter gear 38 of the second reduction gear 35 and the teeth 51 of the first reduction gear 34 are able to rotate.

[0039] Furthermore, in this embodiment, the tooth thickening portions 53A are formed on each tooth portion 50 of the large-diameter gear 38 of the second reduction gear 35. However, the tooth thickening portions 53A may also be formed on each tooth portion 51 of the first reduction gear 34. In short, the tooth thickening portions 53A may be provided on either the tooth portions 50 of the large-diameter gear 38 of the second reduction gear 35 or the tooth portions 51 of the first reduction gear 34. Furthermore, in this embodiment, the solenoid actuator 45 (switching mechanism 43A) is provided on the second reduction gear 35 to advance or retract the second reduction gear 35 relative to the first reduction gear 34. However, the solenoid actuator 45 may also be provided on the first reduction gear 34 to advance or retract the first reduction gear 34 relative to the second reduction gear 35.

[0040] Alternatively, the thickened tooth portion 53A may be formed on the teeth of either of the meshing gears other than the large-diameter gear 38 (first reduction gear 34) of the second reduction gear 35, thereby allowing the solenoid actuator 45 to be located on either one or the other gear. In this embodiment, the thickened tooth portion 53A is formed on one end of each tooth portion 50 of the large-diameter gear 38 of the second reduction gear 35 in the tooth trace direction. However, the thickened tooth portion 53A may also be located on the other end in the tooth trace direction. In this embodiment, when the parking brake is applied, the plunger 48 of the electromagnetic actuator 45 moves in the retracting direction (one end), and when the parking brake is released, the plunger 48 of the electromagnetic actuator 45 moves in the protruding direction (the other end). The above is the structure of the parking brake mechanism 60 including the switch mechanism 43A (solenoid actuator 45) of the first embodiment.

[0041] Reference Figure 2 , the small diameter gear 39 of the second reduction gear 35 is meshed with the third reduction gear 36. The third reduction gear 36 includes a large diameter gear 62 of large diameter that is meshed with the small diameter gear 39 of the second reduction gear 35 and a small diameter sun gear 63 that is concentrically arranged on the inner side of the large diameter gear 62. The sun gear 63 constitutes a part of the planetary gear reduction mechanism 30. An annular space 64 is formed between the inner peripheral surface of the large diameter gear 62 of the third reduction gear 36 and the outer peripheral surface of the sun gear 63. One end of the large diameter gear 62 is connected to one end of the sun gear 63 by a circular plate-shaped wall portion 65. On the surface of the other end side of the circular plate-shaped wall portion 65, an annular stopper 66 protruding toward the other end side is formed near its outer peripheral portion.

[0042] The planetary gear reduction mechanism 30 has a sun gear 63 of the third reduction gear 36, a plurality of (five in this embodiment) planetary gears 70, and an internal gear 71. Each planetary gear 70 has a gear 75 that meshes with the sun gear 63 and the internal gear 71, and a hole portion 76 through which a pin 90 to be described later is rotatably inserted. Each planetary gear 70 is arranged at equal intervals in the circumferential direction around the sun gear 63. In detail, each planetary gear 70 is arranged at equal intervals in the circumferential direction in the annular space 64 between the inner peripheral surface of the large-diameter gear 62 of the third reduction gear 36 and the outer peripheral surface of the sun gear 63, and inside the internal teeth 78 of the internal gear 71 to be described later. The gear 75 of each planetary gear 70 meshes with the sun gear 63 and the internal teeth 78 of the internal gear 71.

[0043] The internal gear 71 has internal teeth 78 that respectively mesh with the gears 75 of the planetary gears 70, a circular ring-shaped wall portion 79 that is continuous from one end of the internal teeth 78 and extends toward the radial center to restrict the axial movement of the planetary gears 70, and a cylindrical wall portion 80 that extends from the other end surface of the periphery of the internal teeth 78 toward the other end side. The positions of the internal teeth 78 of the internal gear 71 are arranged between the inner peripheral surface of the large-diameter gear 62 of the third reduction gear 36 and each planetary gear 70. Further, the third reduction gear 36 is supported so as to be rotatable with respect to the internal gear 71. The circular ring-shaped wall portion 79 of the internal gear 71 is arranged between each planetary gear 70 and the circular plate-shaped wall portion 65 of the third reduction gear 36. The internal gear 71 is supported so as not to be rotatable with respect to the gear case 25, using the cylindrical wall portion 80 thereof and the like, and using the annular position-limiting portion 66 of the circular plate-shaped wall portion 65 of the third reduction gear 36 that abuts against the one end surface of the internal gear 71, and the like, thereby restricting movement in the radial and axial directions.

[0044] Rotation from the planetary gear reduction mechanism 30, that is, rotation from each planetary gear 70 is transmitted to the planetary carrier 72. The planetary carrier 72 is formed in a circular plate shape. In the outer peripheral portion of the planetary carrier 72, a plurality of pin hole portions 89 are formed at intervals in the circumferential direction corresponding to each planetary gear 70. The pin 90 is press-fitted and fixed in each pin hole portion 89. Each pin 90 is rotatably inserted in the hole portion 76 of each planetary gear 70. The main shaft 93 is linked to the planetary carrier 72 so as not to be rotatable with respect to each other. The main shaft 93 is transmitted with rotation from the planetary carrier 72, and transmits the rotational torque thereof to the rotary linear conversion mechanism 31.

[0045] Reference Figure 1The rotary linear motion conversion mechanism 31 converts the rotary motion from the straight-tooth multi-stage reduction mechanism 29 and the planetary gear reduction mechanism 30, i.e., the rotary motion of the main shaft 93, into linear motion (hereinafter, referred to as linear motion for convenience) and exerts a pushing force on the piston 18 by the movement of the linear motion member (omitted from the drawing). The rotary linear motion conversion mechanism 31 is disposed in the cylinder bore 16 between the bottom surface thereof and the piston 18. Moreover, if the main shaft 93 rotates with the rotation of the carrier 72, the linear motion member advances toward the other end side by the rotary linear motion conversion mechanism 31, so that the piston 18 advances, and the inner brake pad 2 can be pressed against the disc rotor D by the piston 18. Note that the rotary linear motion conversion mechanism employs a screw mechanism, a ball screw mechanism, a ball ramp mechanism, or the like.

[0046] Figure 1 The driving of the electric motor 27 is controlled by an instruction from a control substrate (omitted from the drawing). At the time of braking in normal running, the control substrate controls the driving of the electric motor 27 on the basis of a detection signal from a detection sensor (omitted from the drawing) that detects a request corresponding to the request of the driver, various detection sensors (omitted from the drawing) that detect various conditions of the brake, and the like, a detection signal from a rotation angle detection mechanism (omitted from the drawing) and a thrust sensor (omitted from the drawing), and the like. In addition, the control substrate is electrically connected to a parking brake switch (omitted from the drawing), and the operation of the solenoid actuator 45 is controlled in accordance with an instruction from the control substrate.

[0047] Next, in the disc brake 1 of the present embodiment, the operation of braking and brake release in normal running is described.

[0048] At the time of braking in normal running, the electric motor 27 is driven in accordance with an instruction from the control substrate, and the rotation in the positive direction, i.e., the braking direction, is transmitted to the sun gear 63 of the planetary gear reduction mechanism 30 via the straight-tooth multi-stage reduction mechanism 29. By the rotation of the sun gear 63 of the planetary gear reduction mechanism 30, each planetary gear 70 revolves around the rotation axis of the sun gear 63 while self-rotating around its own rotation axis, so that the carrier 72 rotates. That is, the rotation from the electric motor 27 is reduced at a predetermined reduction ratio, amplified, and transmitted to the carrier 72 via the straight-tooth multi-stage reduction mechanism 29 and the planetary gear reduction mechanism 30. Moreover, the rotation from the carrier 72 is transmitted to the main shaft 93.

[0049] Next, as the main shaft 93 rotates with the rotation of the planetary carrier 72, the rotation-to-linear motion conversion mechanism 31 causes the linear motion member to advance, causing the piston 18 to advance. This advancement of the piston 18 presses the inner brake pad 2 against the disc rotor D. Furthermore, the reaction force to the pressing force of the piston 18 on the inner brake pad 2 causes the caliper body 8 to move inward (toward one end) relative to the bracket 5, pressing the outer brake pad 3 against the disc rotor D via the claws 14, 14. As a result, the disc rotor D is clamped between the pair of inner and outer brake pads 2, 3, generating frictional force, which in turn generates braking force for the vehicle.

[0050] On the other hand, when the brake is released, the electric motor 27 is driven in response to a command from the control board, and its rotation in the reverse direction, i.e., the brake release direction, is transmitted to the main shaft 93 via the spur gear multi-stage reduction mechanism 29, the planetary gear reduction mechanism 30, and the planetary carrier 72. As a result, as the main shaft 93 rotates in the reverse direction, the rotation-to-linear motion conversion mechanism 31 operates to cause the direct-acting member to retract and return to its initial state, releasing the braking force on the disc rotor D exerted by the pair of inner brake pads 2 and outer brake pads 3.

[0051] Next, the operation of the parking brake in the disc brake 1 of the present embodiment will be described.

[0052] When the parking brake switch is operated, the electric motor 27 is driven according to a command from the control board, similar to normal braking. Its rotation in the positive direction, i.e., the braking direction, is transmitted to the planetary carrier 72 via the spur gear multi-stage reduction mechanism 29 and the planetary gear reduction mechanism 30. Subsequently, as the main shaft 93 rotates in response to the rotation of the planetary carrier 72, the rotation-to-linear motion conversion mechanism 31 causes the piston 18 to advance, and the disc rotor D is clamped between the pair of inner and outer brake pads 2 and 3, generating braking force.

[0053] In this state, the solenoid actuator 45 is energized in response to a command from the control board, causing the plunger 48 of the solenoid actuator 45 to advance. As a result, the second reduction gear 35 advances axially relative to the first reduction gear 34, and the thick tooth portions 53A (the tapered surfaces 55, 55) of the large-diameter gear 38 of the second reduction gear 35 come into contact with the teeth 51 of the first reduction gear 34 without any gaps, i.e., without any gaps 58. As a result, even after a braking force is generated, even if a rotational torque in the brake release direction is transmitted to the second reduction gear 35 as a reaction force between the disc rotor D and the inner and outer brake pads 2 and 3, the second reduction gear 35 and the first reduction gear 34 do not rotate. Then, power to the electric motor 27 is de-energized, and after confirming the pressing force of the inner and outer brake pads 2 and 3 against the disc rotor D, power to the solenoid actuator 45 is de-energized.

[0054] Furthermore, the solenoid actuator 45 employs a bidirectional holding type that can maintain the position of the plunger 48 via a permanent magnet. Therefore, even when power to the solenoid actuator 45 is stopped, the thick tooth portions 53A of the large-diameter gear 38 of the second reduction gear 35 and the teeth 51 of the first reduction gear 34 remain in contact with each other without creating a gap 58, thereby maintaining the rotation of the second reduction gear 35 and the first reduction gear 34 in a restricted state. Consequently, the braking state can be maintained even when power to the electric motor 27 and the solenoid actuator 45 is stopped, completing the actuation of the parking brake.

[0055] Next, to release the parking brake, the solenoid actuator 45 is energized based on a command from the control board, causing the plunger 48 of the solenoid actuator 45 to retract to its initial position. This results in a return to the initial state, where gaps 58 are created between the teeth 50 of the large-diameter gear 38, including the thick-walled portion 53A, of the second reduction gear 35, and the teeth 51 of the first reduction gear 34. Subsequently, based on a command from the control board, the rotating shaft 27A of the electric motor 27 rotates in the reverse direction, i.e., the brake release direction. This reverse rotation is transmitted to the main shaft 93 via the spur gear multi-stage reduction mechanism 29, the planetary gear reduction mechanism 30, and the planetary carrier 72. As a result, the direct-acting components of the rotation-to-direct motion conversion mechanism 31 retract and return to their initial positions, releasing the braking force exerted on the disc rotor D by the pair of inner and outer brake pads 2 and 3.

[0056] It should be noted that, based on a command from the control board, after a certain period of time has elapsed since the parking brake was applied by the operation of the electric motor 27 and the electromagnetic actuator 45, control (also referred to as a tilting operation) can be performed as needed to release the parking brake application by the electromagnetic actuator 45 and re-apply the parking brake application by the electric motor 27. This prevents a reduction in the thrust of the parking brake due to thermal contraction of the inner and outer brake pads 2 and 3 and the disc rotor D caused by a drop in temperature when the parking brake is applied at a high temperature immediately after braking.

[0057] As described above, the parking brake mechanism 60 of the disc brake 1 of this embodiment includes a solenoid actuator 45 as a switching mechanism 43A that causes the second reduction gear 35 and the first reduction gear 34 to move relative to each other in their axial directions, specifically, causes the second reduction gear 35 to move relative to the first reduction gear 34 in its axial direction. Through the action of the solenoid actuator 45, the presence or absence of a gap 58 between the tooth thick wall portion 53A of the large diameter gear 38 of the second reduction gear 35 and the respective tooth portions 51 of the first reduction gear 34 is generated.

[0058] As a result, the parking brake mechanism 60 included in the disc brake 1 of this embodiment eliminates the need for stepwise operation of a solenoid actuator and an electric motor to align the gear portion of the ratchet wheel with the pawl portion of the retaining member, as in the conventional configuration (described in Patent Document 1). This allows for stepless actuation of the parking brake, resulting in improved controllability. Furthermore, the parking brake mechanism eliminates the need for a ratchet wheel, retaining member, locking member, and compression coil spring, as required in the prior art. This significantly simplifies its structure and layout, enabling miniaturization.

[0059] Conventional parking brakes utilize frictional forces from clutch mechanisms. However, frictional forces are subject to numerous variations due to factors such as surface roughness, deformation, surface conditions, environmental conditions, and aging degradation at the contacting points, making robust reliability a challenge. In contrast, the parking brake mechanism 60 of this embodiment is configured so that the thick tooth portion 53A of the large-diameter gear 38 of the second reduction gear 35 and the teeth 51 of the first reduction gear 34 are brought into contact without creating gaps 58 through the operation of the solenoid actuator 45. This eliminates reliance on difficult-to-manage uncertainties such as frictional forces, resulting in improved safety and reliability.

[0060] Moreover, the parking brake mechanism 60 of the disc brake 1 of this embodiment includes a solenoid actuator 45 as a switching mechanism 43A that moves the second reduction gear 35 in its axial direction. The solenoid actuator 45 adopts a bidirectional holding type that can maintain the position of the plunger 48 by a permanent magnet even when the power is stopped after the operation, thereby avoiding erroneous operation of the parking brake due to driving vibration, etc.

[0061] Next, based on Figure 9 The switch mechanism 43B of the second embodiment will be described. The switch mechanism 43B of the second embodiment includes: an electric motor 100 having a rotating shaft 100A; and a pair of first and second nut components 101 and 102, each of which is screwed onto the rotating shaft 100A and sandwiches the second reduction gear 35 from both axial sides for positioning. Specifically, the first nut component 101 is positioned on one end of the small-diameter gear 39 of the second reduction gear 35. On the other hand, the second nut component 102 is positioned on the other end of the large-diameter gear 38 of the second reduction gear 35. The rotation of the first nut component 101 and the second nut component 102 is restricted.

[0062] A support hole 105 is provided in the radial center of the second reduction gear 35. The support hole 105 penetrates along the axial direction of the second reduction gear 35. The rotating shaft 100A of the electric motor 100 is freely rotatably inserted into the support hole 105 of the second reduction gear 35. Furthermore, when the electric motor 100 is operated to rotate the rotating shaft 100A in the positive direction or the reverse direction, the first nut component 101 and the second nut component 102 respectively move forward or backward, and accordingly, the second reduction gear 35 moves forward or backward along the axial direction. It should be noted that in the present embodiment, the first and second nut components 101 and 102 are screwed together with the rotating shaft 100A through a screw mechanism, but other well-known rotation-to-direct motion conversion mechanisms such as a ball screw mechanism and a roller screw mechanism may also be used.

[0063] Next, based on Figure 10 and Figure 11 Another embodiment of the tooth thickness wall 53B provided on each tooth portion 50 of the large-diameter gear 38 of the second reduction gear 35 will be described. This tooth thickness wall 53B is configured such that, on each of its two tooth flanks, a tapered surface 55 is formed, whose chordal tooth thickness increases toward one end in the tooth trace direction, and a base surface 56 is formed, extending continuously from one end of the tapered surface 55 in the tooth trace direction. The maximum chordal tooth thickness of the tooth thickness wall 53B, i.e., the distance between the pair of base surfaces 56, 56 provided on each tooth flank of the tooth thickness wall 53B, is substantially equal to the distance (tooth groove width) between adjacent teeth 51, 51 of the first reduction gear 34.

[0064] Also, when the parking brake is activated, refer to Figure 11 The solenoid actuator 45 is activated, causing the second reduction gear 35 to advance axially relative to the first reduction gear 34. As a result, the thick tooth portions 53B of the large-diameter gear 38 of the second reduction gear 35, specifically the pair of base surfaces 56, 56 of each thick tooth portion 53B, contact the teeth 51 of the first reduction gear 34 without creating any gaps 58. As a result, even when power is removed from the solenoid actuator 45, the thick tooth portions 53B of the large-diameter gear 38 of the second reduction gear 35 and the teeth 51 of the first reduction gear 34 remain in contact without creating any gaps 58, maintaining the restricted rotation of the second and first reduction gears 35 and 34. This allows the electric motor 27 and the solenoid actuator 45 to maintain their braking state even when power is removed.

[0065] It should be noted that in Figures 6 to 8In the tooth thick wall portion 53A shown, there are many variations due to wear, deformation, environmental conditions, and deterioration over time at the contact portion between each tapered surface 55 of the tooth thick wall portion 53A and each tooth portion 51 of the first reduction gear 34. Therefore, the control of the stroke amount of the plunger 48 of the solenoid actuator 45 for holding the parking brake becomes somewhat complicated. Figure 10 and Figure 11 In the tooth thick wall portion 53B shown in FIG. 1 , by providing a pair of base surfaces 56, 56, the influence of the above-mentioned deviation factor can be reduced, thereby simplifying the control of the stroke amount of the plunger 48 of the solenoid actuator 45 for holding the parking brake. Figure 10 and Figure 11 In the tooth thick wall portion 53B shown, the provision of a pair of base surfaces 56 , 56 can reduce the influence of the above-mentioned variation factor, thereby also suppressing the thrust required for the solenoid actuator 45 and achieving miniaturization.

[0066] Next, based on Figure 12 and Figure 13 Another embodiment of the tooth thickening wall portion 53C provided on each tooth portion 50 of the large-diameter gear 38 of the second reduction gear 35 will be described. The surface of the entire tooth portion 50, including this tooth thickening wall portion 53C, to which the rotation from the electric motor 27 is transmitted when the parking brake is applied, is formed by a base surface 56 extending along the tooth trace direction. Furthermore, the other surface of this tooth thickening wall portion 53C is formed by a tapered surface 55, whose chordal tooth thickness increases toward one end in the tooth trace direction. The maximum chordal tooth thickness of the tooth thickening wall portion 53C is set to be greater than the distance (tooth groove width) between adjacent teeth 51 of the first reduction gear 34.

[0067] Also, when the parking brake is activated, refer to Figure 13 The solenoid actuator 45 is activated, causing the second reduction gear 35 to advance axially relative to the first reduction gear 34. As a result, the thick tooth portions 53C of the large-diameter gear 38 of the second reduction gear 35, specifically the base surfaces 56 and tapered surfaces 55 of each thick tooth portion 53C, contact the teeth 51 of the first reduction gear 34 without creating any gaps 58. As a result, even when power is removed from the solenoid actuator 45, the thick tooth portions 53C of the large-diameter gear 38 of the second reduction gear 35 and the teeth 51 of the first reduction gear 34 remain in contact without creating any gaps 58, maintaining the restricted rotation of the second and first reduction gears 35 and 34. This allows the electric motor 27 and the solenoid actuator 45 to maintain their braking state even when power is removed.

[0068] Next, based on Figure 14 and Figure 15Another embodiment of the tooth thickening wall portion 53D provided on each tooth portion 50 of the large-diameter gear 38 of the second reduction gear 35 will be described. The surface of the entire tooth portion 50, including the tooth thickening wall portion 53D, to which the rotation from the electric motor 27 is transmitted when the parking brake is applied, is formed by a base surface 56 extending along the tooth trace direction. Furthermore, the other surface of the tooth thickening wall portion 53D is formed by a tapered surface 55 whose chordal tooth thickness increases toward one end in the tooth trace direction, and a base surface 56 extending along the tooth trace direction, continuing from the tooth trace end of the tapered surface 55. The maximum chordal tooth thickness of the tooth thickening wall portion 53D, that is, the distance between the pair of base surfaces 56, 56 provided on the two tooth surfaces of the tooth thickening wall portion 53D, is substantially equal to the distance between adjacent teeth 51, 51 of the first reduction gear 34 (the width of the tooth groove).

[0069] Also, when the parking brake is activated, refer to Figure 15 The solenoid actuator 45 is activated, causing the second reduction gear 35 to advance axially relative to the first reduction gear 34. As a result, the thick tooth portions 53D of the large-diameter gear 38 of the second reduction gear 35, specifically the pair of base surfaces 56, 56 of each thick tooth portion 53D, contact the teeth 51 of the first reduction gear 34 without creating any gaps 58. As a result, even when power is removed from the solenoid actuator 45, the thick tooth portions 53D of the large-diameter gear 38 of the second reduction gear 35 and the teeth 51 of the first reduction gear 34 remain in contact without creating any gaps 58, maintaining the restricted rotation of the second and first reduction gears 35 and 34. This allows the electric motor 27 and the solenoid actuator 45 to maintain their braking state even when power is removed.

[0070] As explained above, in Figure 12 and Figure 13 The thick wall portion 53C shown, and Figure 14 and Figure 15 In the tooth thick wall portion 53D shown, the surface of the entire tooth portion 50 (50) including the tooth thick wall portion 53C (53D) to which the rotation from the electric motor 27 is transmitted when the parking brake is actuated is formed by a base surface 56 (56) extending along the tooth line direction. Therefore, when the parking brake is actuated, if the electric motor 27 is driven in the braking direction, the base surface 56 of the entire tooth portion 50 (50) including the tooth thick wall portion 53C (53D) and the tooth portion 51 of the first reduction gear 34 can perform linear motion without steps, thereby reducing the thrust of the solenoid actuator 45 for actuating the parking brake. In addition, by actuating the electromagnetic actuator 45 while rotating the electric motor 27, it is possible to further reduce the thrust of the electromagnetic actuator 45 and increase the smoothness of the parking brake.

[0071] On the other hand, when the parking brake is released, the base surface 56 of the entire tooth portion 50 (50) including the tooth thick wall portion 53C (53D) and the tooth portion 51 of the first reduction gear 34 are also in a state where they can move linearly without steps, thereby reducing the thrust of the solenoid actuator 45 for releasing the parking brake. In addition, by operating the solenoid actuator 45 while rotating the electric motor 27, it is possible to further reduce the thrust of the solenoid actuator 45 and smoothly reduce the parking brake.

[0072] It should be noted that, in the above description, the present embodiment is adopted in a disc brake 1 as an electric brake device that generates braking force by driving an electric motor 27 during normal driving. However, the present embodiment can also be adopted in the following disc brake as an electric brake device: during normal driving, the brake fluid pressure supplied to the cylinder bore 16 of the brake caliper body 8 is used to advance the piston 18, thereby generating braking force through a pair of inner brake pads 2 and outer brake pads 3. Only during parking braking, such as when parking, the rotation from the electric motor 27 is transmitted to the piston 18 via the spur gear multi-stage reduction mechanism 29, the planetary gear reduction mechanism 30 and the rotation-to-direct motion conversion mechanism 31, thereby advancing the piston 18 and generating braking force through a pair of inner brake pads 2 and outer brake pads 3.

[0073] Furthermore, the present invention is not limited to the above-described embodiments and includes various variations. For example, the above-described embodiments are described in detail to facilitate understanding of the present invention and are not limited to necessarily having all the structures described. Furthermore, a portion of the structure of a certain embodiment can be replaced with the structure of another embodiment, and a portion of the structure of a certain embodiment can be supplemented with the structure of another embodiment. Furthermore, with respect to a portion of the structure of each embodiment, other structures can be added, deleted, or substituted.

[0074] This application claims the benefit of priority based on Japanese Patent Application No. 2023-102521 filed on June 22, 2023. The entire disclosure of Japanese Patent Application No. 2023-102521 filed on June 22, 2023 including the specification, claims, drawings, and abstract is incorporated herein by reference in its entirety.

[0075] Description of Reference Numerals

[0076] 1: Disc brake (electric brake device)

[0077] 2: Inner brake pad (brake component)

[0078] 3: External brake pad (brake component)

[0079] 29: Straight tooth multi-stage reduction mechanism (reduction mechanism)

[0080] 34: First reduction gear (first gear)

[0081] 35: Second reduction gear

[0082] 38: Large diameter gear (second gear)

[0083] 43A, 43B: Switch mechanism

[0084] 50: Tooth

[0085] 45: Solenoid actuator (switch mechanism)

[0086] 51: Tooth

[0087] 53A~53D: Thick wall part of tooth

[0088] 55: Conical surface

[0089] 56: Base surface

[0090] 58: Gap

[0091] 60: Parking brake mechanism

[0092] D: Disc rotor (braked part)

Claims

1. An electric brake device, characterized in that: The electric brake device has: electric motors; a speed reduction mechanism for amplifying the rotational torque from the electric motor; The parking brake mechanism converts the rotation from the reduction mechanism into linear motion, maintaining the pressing force of the braking member toward the braked member. The speed reduction mechanism includes a first gear and a second gear meshing with the first gear. There is a gap between the teeth of the first gear and the teeth of the second gear along the rotation direction, The parking brake mechanism includes a switch mechanism for relatively moving the first gear and the second gear in their axial directions. The presence or absence of the gap is determined by the operation of the switch mechanism.

2. The electric brake device according to claim 1, characterized in that In the parking brake mechanism, a tooth thick wall portion having a large chordal tooth thickness is formed at an end portion in a tooth trace direction on the tooth portion of either the first gear or the second gear.

3. The electric brake device according to claim 2, characterized in that The tooth thickness wall portion includes a tapered surface whose chordal tooth thickness gradually increases toward one end.

4. The electric brake device according to claim 3, characterized in that The tooth thick wall portion includes a base surface that is continuous from one end of the tapered surface in the tooth trace direction and extends along the tooth trace direction.

5. The electric brake device according to claim 3 or 4, characterized in that: The surface of the entire tooth portion including the tooth thick wall portion, to which the rotation from the electric motor is transmitted when the parking brake is actuated, is formed by a base surface extending along the tooth trace direction.

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