Electric brake device

Abstract

Provided is an electric brake device equipped with a parking brake mechanism which exhibits excellent controllability, and achieves miniaturization with a simple structure. The parking brake mechanism provided to a disk brake is equipped with a solenoid actuator that serves as a switch mechanism for moving a first reduction gear and a large-diameter gear of a second reduction gear relative to each other along the axial direction thereof, and is configured to generate or not to generate a gap between a thick tooth part of the large-diameter gear of the second reduction gear and each tooth part of the first reduction gear 34 by the operation of the solenoid actuator. With this configuration, said parking brake mechanism is capable of exhibiting excellent controllability and achieving miniaturization with a simple structure.

Description

Electric brake device

[0001] The present invention relates to an electric brake device used for braking a vehicle.

[0002] For example, in a disc brake (electric brake device) described in Patent Document 1, when the parking brake is activated, a solenoid actuator is energized, causing a plunger of the solenoid actuator to retract, and the claws of the holding member move toward the outer circumferential surface of the ratchet gear against the biasing force of the compression coil spring, engaging with the gear portion thereof and maintaining the braked state. At this time, the gear portion of the ratchet gear and the claws of the holding member may not engage with each other because their respective apexes interfere with each other, so to align them with each other, the electric motor is rotated in the brake release direction to reliably engage the gear portion of the ratchet gear and the claws of the holding member.

[0003] Patent No. 7220281

[0004] However, in the disc brake described in the above-mentioned Patent Document 1, when the parking brake is activated, the solenoid actuator and the electric motor must be operated in stages to align the gear portion of the ratchet gear with the claw portion of the retaining member, which makes the control thereof complicated and poses a problem in controllability. Moreover, in the disc brake described in the above-mentioned Patent Document 1, the parking brake mechanism must include a ratchet gear, a retaining member, a locking member, a compression coil spring, etc., which makes the structure and layout very complicated and also causes problems such as an increase in size.

[0005] In view of the above-mentioned problems, an object of the present invention is to provide an electric brake device having a parking brake mechanism that has good controllability, a simple structure, and a compact size.

[0006] As a means for solving the above-mentioned problems, the electric brake device of the present invention is an electric brake device comprising: 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 and maintains a pressing force that presses a braking member toward a member to be braked, wherein the reduction mechanism has a first gear and a second gear that meshes with the first gear, and a gap is formed along the rotational direction between the teeth of the first gear and the teeth of the second gear, and the parking brake mechanism comprises a switch mechanism that moves the first gear and the second gear relatively along their axial direction, and operation of the switch mechanism determines whether or not the gap exists.

[0007] The parking brake mechanism provided in the electric brake device according to one embodiment of the present invention has good controllability, a simple structure, and can be made compact.

[0008] 7 is a partial cross-sectional view of the disc brake according to the present embodiment; an enlarged cross-sectional view of a main portion of the disc brake according to the present embodiment; an exploded perspective view of a parking brake mechanism employed in the disc brake according to the present embodiment; a perspective view of the parking brake mechanism employed in the disc brake according to the present embodiment; a cross-sectional view showing a state in which a plunger of a solenoid actuator is attached to a second reduction gear employed in the disc brake according to the present embodiment; a cross-sectional view perpendicular to the radial direction of each tooth portion, including a thick tooth portion, of the large diameter gear of the ..., in 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 according to the present embodiment is meshed with each tooth portion of the first reduction gear; a cross-sectional view perpendicular to the radial direction of a state in which the second reduction gear has moved axially relative to the first reduction gear due to operation of the solenoid actuator from the state in FIG. 7; a cross-sectional view of a switch mechanism according to the second embodiment; a cross-sectional view perpendicular to the radial direction of each tooth portion, including a thick tooth portion according to another embodiment, of the large diameter gear of the second reduction gear, in a state in which each tooth portion of the first reduction gear is meshed with each tooth portion of the first reduction gear. 10 , a cross-sectional view perpendicular to the radial direction showing a state in which the second reduction gear has moved axially relative to the first reduction gear due to activation of the solenoid actuator; a cross-sectional view perpendicular to the radial direction showing a state in which tooth portions, including thick-tooth portions according to yet another embodiment, of the large-diameter gear of the second reduction gear are meshed with tooth portions of the first reduction gear; a cross-sectional view perpendicular to the radial direction showing a state in which the second reduction gear has moved axially relative to the first reduction gear due to activation of the solenoid actuator from the state in FIG. 12 ; a cross-sectional view perpendicular to the radial direction showing a state in which tooth portions, including thick-tooth portions according to yet another embodiment, of the large-diameter gear of the second reduction gear are meshed with tooth portions of the first reduction gear; a cross-sectional view perpendicular to the radial direction showing a state in which the second reduction gear has moved axially relative to the first reduction gear due to activation of the solenoid actuator from the state in FIG.

[0009] This embodiment will be described in detail below with reference to Figures 1 to 15. The electric brake device according to this embodiment, specifically the disc brake 1, generates a braking force by driving an electric motor 27 during normal driving. In the following description, the inside of the vehicle (inner side) will be referred to as one end side, and the outside of the vehicle (outer side) will be referred to as the other end side, where appropriate. That is, in Figures 1 and 2, the right side will be referred to as one end side, and the left side will be referred to as the other end side, where appropriate.

[0010] Referring to Figure 1, a disc brake 1 according to this embodiment includes a pair of inner brake pads 2 and an outer brake pad 3, and a caliper 4, which are arranged on either side of a disc rotor D attached to a rotating part of a vehicle in the axial direction. The disc brake 1 is configured as a floating caliper. The pair of inner brake pads 2, outer brake pad 3, and caliper 4 are supported by a bracket 5 fixed to a non-rotating part of the vehicle, such as a knuckle, so as to be movable in the axial direction of the disc rotor D. The disc rotor D corresponds to the member to be braked. The pair of inner brake pads 2 and outer brake pad 3 correspond to the braking member.

[0011] 1 , the caliper 4 includes a caliper body 8 that is the main body of the caliper 4, and a transmission mechanism 9 that transmits rotation from an electric motor 27 to a piston 18 in a cylinder portion 13 of the caliper body 8 and applies thrust to the piston 18. The caliper body 8 includes a cylindrical cylinder portion 13 that is disposed on the base end side facing the inner brake pad 2 and opens facing the inner brake pad 2, and a pair of claw portions 14, 14 that extend from the cylinder portion 13 to the outer side across the disc rotor D and are disposed on the tip end side facing the outer brake pad 3.

[0012] A piston 18 is housed in the cylinder portion 13 of the caliper body 8, i.e., in the cylinder bore 16 of the cylinder portion 13, so as to be non-rotatable relative to the cylinder portion 13 and to be movable in the axial direction. The piston 18 presses against the inner brake pad 2 and is formed in a cup shape with a bottom. The piston 18 is housed in the cylinder bore 16 of the cylinder portion 13 so that its bottom faces the inner brake pad 2. The piston 18 is supported so as to be non-rotatable relative to the cylinder bore 16, and ultimately to the caliper body 8, by the anti-rotation engagement between the bottom and the inner brake pad 2.

[0013] A seal member (not shown) is disposed on the inner peripheral 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 and is axially movable while in contact with the seal member. A dust boot 20 is interposed between the outer peripheral surface of the bottom of the piston 18 and the inner peripheral surface of the other end of the cylinder bore 16. The seal member and the dust boot 20 prevent foreign matter from entering the cylinder bore 16 of the cylinder portion 13. A gear housing 25 is integrally connected to the bottom wall 23 (one end) of the cylinder portion 13 of the caliper body 8. An electric motor 27, a spur gear multi-stage reduction mechanism 29, and a planetary gear reduction mechanism 30 (described later) are disposed within the gear housing 25. An opening on one end of the gear housing 25 is closed by a cover member (not shown). The cover member is attached to the gear housing 25 in an airtight manner.

[0014] Rotation from the electric motor 27 is transmitted to the piston 18 via a transmission mechanism 9. The transmission mechanism 9 includes a spur gear multi-stage reduction mechanism 29 and a planetary gear reduction mechanism 30 that amplify the rotational torque from the electric motor 27, and a rotary-to-linear motion conversion mechanism 31 that converts the rotation from the planetary gear reduction mechanism 30 into linear motion and applies thrust to the piston 18. The electric motor 27 is disposed within a gear housing 25, and its rotation shaft 27A extends toward one end. Referring to FIG. 2 , the spur gear 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. The first reduction gear 34 corresponds to the first gear.

[0015] Referring to FIGS. 2 to 5, the first reduction gear 34 is cylindrical and press-fitted onto the rotary shaft 27A of the electric motor 27. The second reduction gear 35 is a stepped gear. The second reduction gear 35 includes a large-diameter gear 38 that meshes with the first reduction gear 34 and a small-diameter gear 39 that extends axially concentrically from the large-diameter gear 38 toward one end. The large-diameter gear 38 of the second reduction gear 35 corresponds to the second gear. The following describes the configuration of a parking brake mechanism 60 including a switch mechanism 43A (solenoid actuator 45) according to the first embodiment. Referring to FIGS. 3 and 5, a mounting hole 41 is provided in the radial center of the second reduction gear 35. The mounting hole 41 penetrates the second reduction gear 35 along the axial direction. A plunger 48 of the solenoid actuator 45 serving as the switch mechanism 43A according to the first embodiment is rotatably inserted into the mounting hole 41 of the second reduction gear 35.

[0016] A pair of retaining rings 42, 42 are provided on the plunger 48 of the solenoid actuator 45 at positions that sandwich the second reduction gear 35 in the axial direction. These retaining rings 42, 42 restrict axial movement of the plunger 48 relative to the second reduction gear 35. The second reduction gear 35 is rotatably supported by the plunger 48 of the solenoid actuator 45. The solenoid actuator 45 is a two-way retaining type that can retain the position of the plunger 48 using a permanent magnet after it has advanced or retreated. As a result, after the parking brake has been applied, the parking state can be maintained even if power to the solenoid actuator 45 is released. Referring to FIGS. 1 and 2, the solenoid actuator 45 has a main body 47 located at one end.

[0017] 5 and 6, each tooth portion 50 of the large diameter gear 38 of the second reduction gear 35 has a tooth thick portion 53A formed at one end in the tooth trace direction, where the chordal tooth thickness is increased. Referring also to FIG. 2, this end in the tooth trace direction is the same as one end of the disc brake 1, and is on the side of the main body 47 of the solenoid actuator 45. Referring to FIGS. 5 and 6, the tooth thick portion 53A has tapered surfaces 55, 55 formed on both tooth flanks, each of which has a chordal tooth thickness that increases toward one end in the tooth trace direction. Referring to FIG. 8, the maximum chordal tooth thickness of the tooth thick portion 53A is set to be greater than the distance (tooth space width) between adjacent tooth portions 51, 51 of the first reduction gear 34. 7 and 8, the 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 equivalent to the tooth width of the thick tooth portion 53A.

[0018] 7, during normal operation when the solenoid actuator 45 is not activated, the toothed portions 50 including the thick toothed portions 53A of the large diameter gear 38 of the second reduction gear 35 mesh with the toothed portions 51 of the first reduction gear 34, creating gaps 58 between the toothed portions 50 of the large diameter gear 38 of the second reduction gear 35 and the toothed portions 51 of the first reduction gear 34. As a result, the toothed portions 50 including the thick toothed portions 53A of the large diameter gear 38 of the second reduction gear 35 and the toothed portions 51 of the first reduction gear 34 can slide against each other, allowing the transmission of rotational torque between them.

[0019] 8, when the parking brake is applied, the solenoid actuator 45 is operated, causing the plunger 48 to move forward (project) toward the other end, causing the second reduction gear 35 to move forward in the axial direction relative to the first reduction gear 34. This causes the thick-tooth portions 53A of the large-diameter gear 38 of the second reduction gear 35, more specifically the tapered surfaces 55, 55 of the thick-tooth portions 53A, to come into contact with the tooth portions 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, and the parking brake state is maintained.

[0020] Furthermore, when the parking brake is released, the solenoid actuator 45 is actuated to retract the plunger 48 to its initial state, causing the second reduction gear 35 to retract axially relative to the first reduction gear 34. As a result, as shown in Figure 7, the toothed portions 50 including the thick tooth portions 53A of the large diameter gear 38 of the second reduction gear 35 and the toothed portions 51 of the first reduction gear 34 return to their initial states in which gaps 58 are formed between them. As a result, the toothed portions 50 including the thick tooth portions 53A of the large diameter gear 38 of the second reduction gear 35 and the toothed portions 51 of the first reduction gear 34 become rotatable.

[0021] In this embodiment, the thick tooth portions 53A are formed on each tooth portion 50 of the large diameter gear 38 of the second reduction gear 35, but the thick tooth portions 53A may also be formed on each tooth portion 51 of the first reduction gear 34. In other words, it is sufficient to provide the thick tooth portions 53A 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. In this embodiment, the second reduction gear 35 is provided with a solenoid actuator 45 (switch mechanism 43A) to move the second reduction gear 35 forward or backward relative to the first reduction gear 34, but the first reduction gear 34 may also be provided with a solenoid actuator 45 to move the first reduction gear 34 forward or backward relative to the second reduction gear 35.

[0022] Furthermore, the thick tooth portion 53A may be formed on the tooth portion of one of the meshing gears other than the large-diameter gear 38 (first reduction gear 34) of the second reduction gear 35, and the solenoid actuator 45 may be provided on either one or the other gear. Furthermore, in this embodiment, the thick tooth portion 53A is formed on one end side in the tooth trace direction of each tooth portion 50 of the large-diameter gear 38 of the second reduction gear 35. However, the thick tooth portion 53A may be provided on the other end side in the tooth trace direction. In this embodiment, when the parking brake is activated, the plunger 48 of the solenoid actuator 45 moves in the retracted direction (toward one end), and when the parking brake is released, the plunger 48 of the solenoid actuator 45 moves in the protruding direction (toward the other end). The above is the configuration of the parking brake mechanism 60 having the switch mechanism 43A (solenoid actuator 45) according to the first embodiment.

[0023] 2 , the small diameter gear 39 of the second reduction gear 35 meshes with the third reduction gear 36. The third reduction gear 36 includes a large diameter gear 62 that meshes with the small diameter gear 39 of the second reduction gear 35, and a small diameter sun gear 63 that is concentrically disposed inside the large diameter gear 62. The sun gear 63 is configured as 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 and one end of the sun gear 63 are connected by a disk-shaped wall portion 65. An annular stopper portion 66 that protrudes toward the other end is formed on the surface of the other end of the disk-shaped wall portion 65 near the outer periphery.

[0024] The planetary gear reduction mechanism 30 includes a sun gear 63 of the third reduction gear 36, a plurality of planetary gears 70 (five in this embodiment), and an internal gear 71. Each planetary gear 70 has a gear 75 that meshes with the internal teeth 78 of the sun gear 63 and the internal gear 71, and a hole 76 through which a pin 90 extending from a carrier 72 (described later) is rotatably inserted. The planetary gears 70 are arranged at equal intervals around the sun gear 63 in the circumferential direction. More specifically, the planetary gears 70 are arranged at equal intervals around the circumferential direction in the annular space 64 between the inner circumferential surface of the large-diameter gear 62 of the third reduction gear 36 and the outer circumferential surface of the sun gear 63, inside the internal teeth 78 of the internal gear 71 (described later). The gear 75 of each planetary gear 70 meshes with the internal teeth 78 of the sun gear 63 and the internal gear 71.

[0025] The internal gear 71 includes internal teeth 78 that mesh with the gears 75 of each planetary gear 70, an annular wall portion 79 that extends continuously from one end of the internal teeth 78 toward the radial center and restricts axial movement of each planetary gear 70, and a cylindrical wall portion 80 that extends from the other end face around the internal teeth 78 toward the other end. The internal teeth 78 of the internal gear 71 are disposed between the inner circumferential surface of the large-diameter gear 62 of the third reduction gear 36 and each planetary gear 70. The third reduction gear 36 is supported rotatably relative to the internal gear 71. The annular wall portion 79 of the internal gear 71 is disposed between each planetary gear 70 and the disk-shaped wall portion 65 of the third reduction gear 36. The internal gear 71 has a cylindrical wall portion 80 and a configuration in which an annular stopper portion 66 provided on the disk-shaped wall portion 65 of the third reduction gear 36 abuts against one end face of the internal gear 71, thereby restricting radial and axial movement and supporting the gear housing 25 so that it cannot rotate relative to the gear housing 25.

[0026] Rotation from the planetary gear reduction mechanism 30, i.e., rotation from each planetary gear 70, is transmitted to the carrier 72. The carrier 72 is formed in a disk shape. A plurality of pin holes 89 are formed at intervals along the circumferential direction on the outer periphery of the carrier 72 so as to correspond to each planetary gear 70. Pins 90 are press-fitted and fixed into each pin hole 89. Each pin 90 is rotatably inserted into a hole 76 of each planetary gear 70, respectively. A spindle 93 is connected to the carrier 72 so as not to rotate relative to the carrier 72. The spindle 93 receives the rotation from the carrier 72 and transmits the rotational torque to the rotary-to-linear motion conversion mechanism 31.

[0027] 1 , the rotary-to-linear motion conversion mechanism 31 converts the rotational motion from the spur gear multi-stage reduction mechanism 29 and the planetary gear reduction mechanism 30, i.e., the rotational motion of the spindle 93, into linear motion (hereinafter referred to as linear motion for convenience), and applies thrust to the piston 18 by movement of its linear motion member (not shown). The rotary-to-linear motion conversion mechanism 31 is disposed within the cylinder bore 16, between the bottom surface of the cylinder bore 16 and the piston 18. When the spindle 93 rotates in conjunction with the rotation of the carrier 72, the rotary-to-linear motion conversion mechanism 31 causes the linear motion member to advance toward the other end, thereby advancing the piston 18, and the piston 18 can press the inner brake pad 2 against the disc rotor D. The rotary-to-linear motion conversion mechanism may be a screw mechanism, a ball screw mechanism, a ball and ramp mechanism, or the like.

[0028] 1 is controlled by commands from a control board (not shown). During braking during normal driving, the control board controls the driving of the electric motor 27 based on detection signals from a detection sensor (not shown) that responds to driver requests, various detection sensors (not shown) that detect various situations where braking is required, and the like, as well as detection signals from a rotation angle detection means (not shown), a thrust sensor (not shown), and the like. The control board is also electrically connected to a parking brake switch (not shown), and the operation of a solenoid actuator 45 is controlled by commands from the control board.

[0029] Next, the braking and brake release actions during normal driving of the disc brake 1 according to this embodiment will be described. During braking during normal driving, the electric motor 27 is driven by a command from the control board, and its rotation in the forward direction, i.e., the braking direction, is transmitted to the sun gear 63 of the planetary gear reduction mechanism 30 via the spur multi-stage reduction mechanism 29. The rotation of the sun gear 63 of the planetary gear reduction mechanism 30 causes each planetary gear 70 to rotate about its own rotation axis while revolving around the rotation axis of the sun gear 63, thereby rotating the carrier 72. In other words, the rotation from the electric motor 27 is reduced and increased at a predetermined reduction ratio by passing through the spur multi-stage reduction mechanism 29 and the planetary gear reduction mechanism 30, and then transmitted to the carrier 72. The rotation from the carrier 72 is then transmitted to the spindle 93.

[0030] Next, when the spindle 93 rotates in conjunction with the rotation of the carrier 72, the linear motion member thereof advances due to the action of the rotary-linear motion conversion mechanism 31, thereby advancing the piston 18. As the piston 18 advances, it presses the inner brake pad 2 against the disc rotor D. Then, due to a reaction force against the pressing force of the piston 18 on the inner brake pad 2, the caliper body 8 moves toward the inner side (one end side) relative to the bracket 5, and the claws 14, 14 press the outer brake pad 3 against the disc rotor D. As a result, the disc rotor D is sandwiched between the pair of inner and outer brake pads 2, 3, generating a frictional force, which in turn generates a braking force for the vehicle.

[0031] On the other hand, when braking is to be released, the electric motor 27 is driven by a command from the control board, and rotation in the reverse direction, i.e., the brake release direction, is transmitted to the spindle 93 via the spur gear multi-stage reduction mechanism 29, the planetary gear reduction mechanism 30, and the carrier 72. As a result, as the spindle 93 rotates in the reverse direction, the linear motion member moves backward and returns to its initial state due to the action of the rotary-linear motion conversion mechanism 31, and the braking force applied to the disc rotor D by the pair of inner and outer brake pads 2, 3 is released.

[0032] Next, the operation of the parking brake of the disc brake 1 according to this embodiment will be described. When the parking brake switch is operated, as in normal braking, the electric motor 27 is driven by a command from the control board, and rotation in the forward direction, i.e., the braking direction, is transmitted to the carrier 72 via the spur gear multi-stage reduction mechanism 29 and the planetary gear reduction mechanism 30. Next, when the spindle 93 rotates in conjunction with the rotation from the carrier 72, the piston 18 moves forward due to the action of the rotary-to-linear motion conversion mechanism 31, and the disc rotor D is clamped between the pair of inner and outer brake pads 2, 3, generating a braking force.

[0033] In this state, by supplying current to the solenoid actuator 45 in response to a command from the control board, the plunger 48 of the solenoid actuator 45 advances. As a result, the second reduction gear 35 advances axially relative to the first reduction gear 34, and the thick-tooth portions 53A (respective tapered surfaces 55, 55) of the large-diameter gear 38 of the second reduction gear 35 come into contact with the tooth portions 51 of the first reduction gear 34 without any gaps, i.e., without any gaps 58. As a result, 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, 3 after a braking force is generated, the second reduction gear 35 and the first reduction gear 34 do not rotate. Then, the electric motor 27 is de-energized, and the pressing force of the pair of inner and outer brake pads 2, 3 against the disc rotor D is confirmed. Then, the solenoid actuator 45 is de-energized.

[0034] Furthermore, the solenoid actuator 45 is a two-way holding type that can hold the position of the plunger 48 by a permanent magnet, so even when the power supply to the solenoid actuator 45 is cut off, the thick-tooth portions 53A of the large-diameter gear 38 of the second reduction gear 35 and the tooth portions 51 of the first reduction gear 34 are kept in contact with each other so that no gaps 58 are formed, and the rotation of the second reduction gear 35 and the first reduction gear 34 is kept restricted. As a result, the braking state can be maintained even when the power supply to the electric motor 27 and the solenoid actuator 45 is cut off, and the operation of the parking brake is completed.

[0035] Next, to release the parking brake, 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 retract to its initial position. As a result, the initial state is restored, where gaps 58 are formed between the toothed portions 50, including the thick-toothed portions 53A, of the large-diameter gear 38 of the second reduction gear 35 and the toothed portions 51 of the first reduction gear 34. Thereafter, in response to 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, and this reverse rotation is transmitted to the spindle 93 via the multi-stage spur gear reduction mechanism 29, the planetary gear reduction mechanism 30, and the carrier 72. As a result, the linear motion member of the rotary-to-linear motion conversion mechanism 31 retracts and returns to its initial position, releasing the braking force exerted on the disc rotor D by the pair of inner and outer brake pads 2, 3.

[0036] Note that, in response to a command from the control board, the parking brake is activated by operating the electric motor 27 and the solenoid actuator 45, and after a certain time has elapsed, if necessary, control (also referred to as a reclamping operation) may be executed to activate the parking brake again by the electric motor 27 while releasing the activation of the parking brake by the solenoid actuator 45. This makes it possible to prevent a decrease in the thrust of the parking brake that occurs due to thermal contraction of the inner and outer brake pads 2, 3 and the disc rotor D caused by a drop in temperature when the parking brake is activated under high temperatures immediately after braking.

[0037] As described above, the parking brake mechanism 60 provided in the disc brake 1 according to this embodiment is provided with a solenoid actuator 45 as a switch mechanism 43A that moves the second reduction gear 35 and the first reduction gear 34 relative to each other along their axial direction, more specifically, that moves the second reduction gear 35 along its axial direction relative to the first reduction gear 34, and operation of the solenoid actuator 45 determines whether or not there is a gap 58 between the thick-tooth portion 53A of the large-diameter gear 38 of the second reduction gear 35 and each tooth portion 51 of the first reduction gear 34.

[0038] As a result, in the parking brake mechanism 60 provided in the disc brake 1 according to this embodiment, it is not necessary to operate the solenoid actuator and the electric motor in stages to align the gear portion of the ratchet gear with the claw portion of the retaining member, as in the conventional device (disclosed in Patent Document 1), and the parking brake can be operated continuously, resulting in good controllability. Moreover, it is not necessary to include a ratchet gear, retaining member, locking member, compression coil spring, etc. as a parking brake mechanism, as in the conventional device, and the structure and layout are greatly simplified, allowing for miniaturization.

[0039] Furthermore, while conventional parking brakes use frictional force generated by a clutch mechanism, the frictional force is subject to many variations due to factors such as the surface roughness, deformation, and condition of the contact area, as well as environmental conditions and deterioration over time, making it difficult to ensure robust reliability. In contrast, the parking brake mechanism 60 according to this embodiment is configured such that, when the solenoid actuator 45 is activated, the thick-toothed portion 53A of the large-diameter gear 38 of the second reduction gear 35 comes into contact with the teeth 51 of the first reduction gear 34 without creating gaps 58, thereby improving safety and reliability without relying on uncertain factors such as frictional force, which are difficult to control.

[0040] Furthermore, the parking brake mechanism 60 provided in the disc brake 1 according to this embodiment has a solenoid actuator 45 as a switch mechanism 43A that moves the second reduction gear 35 in its axial direction, and the solenoid actuator 45 is a two-way holding type that can hold the position of the plunger 48 using a permanent magnet even when the power supply is stopped after operation, thereby preventing the parking brake from being accidentally activated due to vibrations during driving, etc.

[0041] Next, a switch mechanism 43B according to a second embodiment will be described with reference to Figure 9. The switch mechanism 43B according to the second embodiment includes an electric motor 100 having a rotating shaft 100A, and a pair of first and second nut members 101, 102 that are each threadedly engaged with the rotating shaft 100A and that sandwich and position the second reduction gear 35 from both axial sides. More specifically, the first nut member 101 is disposed on one end side of the small diameter gear 39 of the second reduction gear 35. Meanwhile, the second nut member 102 is disposed on the other end side of the large diameter gear 38 of the second reduction gear 35. The rotation of the first and second nut members 101, 102 is restricted.

[0042] A support hole 105 is provided in the radial center of the second reduction gear 35. The support hole 105 penetrates the second reduction gear 35 along the axial direction. The rotating shaft 100A of the electric motor 100 is rotatably inserted into the support hole 105 of the second reduction gear 35. When the electric motor 100 is operated to rotate the rotating shaft 100A in the forward or reverse direction, the first and second nut members 101, 102 each move forward or backward, and accordingly, the second reduction gear 35 moves forward or backward along the axial direction. In this embodiment, the first and second nut members 101, 102 and the rotating shaft 100A are engaged with each other by a screw mechanism. However, other known rotary-linear conversion mechanisms, such as a ball screw mechanism or a roller screw mechanism, may also be used.

[0043] Next, a thick tooth portion 53B according to another embodiment, which is provided on each tooth portion 50 of the large-diameter gear 38 of the second reduction gear 35, will be described with reference to Figures 10 and 11. The thick tooth portion 53B is configured such that, on both tooth flanks, a tapered surface 55 whose chordal thickness increases toward one end in the tooth trace direction is formed, and a base surface 56 that extends along the tooth trace direction and continues from one end in the tooth trace direction of the tapered surface 55. The maximum chordal tooth thickness of the thick tooth portion 53B, i.e., the distance between the pair of base surfaces 56, 56 provided on both tooth flanks of the thick tooth portion 53B, is approximately equal to the distance (tooth space width) between adjacent tooth portions 51, 51 of the first reduction gear 34.

[0044] 11 , when the parking brake is applied, the solenoid actuator 45 is activated, and the second reduction gear 35 moves forward in the axial direction relative to the first reduction gear 34, so that 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, come into contact with the teeth 51 of the first reduction gear 34 without creating a gap 58. As a result, even when the power supply to the solenoid actuator 45 is stopped, 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 with each other without creating a gap 58, and the rotation of the second reduction gear 35 and the first reduction gear 34 is maintained in a restricted state. This makes it possible to maintain the braking state even when the power supply to the electric motor 27 and the solenoid actuator 45 is stopped.

[0045] 6 to 8, many variation factors, such as changes over time and deformation due to wear at the contact portions between the tapered surfaces 55 of the tooth thick portion 53A and the tooth portions 51 of the first reduction gear 34, environmental conditions, and deterioration over time, make it somewhat complicated to control the stroke amount of the plunger 48 of the solenoid actuator 45 for engaging the parking brake. In contrast, the tooth thick portion 53B shown in FIGS. 10 and 11 has a pair of base surfaces 56, 56, which reduces the influence of the variation factors described above, thereby simplifying control of the stroke amount of the plunger 48 of the solenoid actuator 45 for engaging the parking brake. Furthermore, the tooth thick portion 53B shown in FIGS. 10 and 11 has a pair of base surfaces 56, 56, which reduces the influence of the variation factors described above, thereby reducing the thrust required for the solenoid actuator 45 and enabling it to be made more compact.

[0046] Next, a thick tooth portion 53C according to another embodiment, which is provided on each tooth portion 50 of the large-diameter gear 38 of the second reduction gear 35, will be described with reference to Figures 12 and 13. One surface of the entire tooth portion 50, including the thick tooth portion 53C, to which rotation from the electric motor 27 is transmitted when the parking brake is activated, is formed by a base surface 56 extending along the tooth trace direction. The other surface of the thick tooth portion 53C is formed by a tapered surface 55 whose chordal thickness increases toward one end in the tooth trace direction. The maximum chordal thickness of the thick tooth portion 53C is set to be greater than the distance between adjacent tooth portions 51, 51 of the first reduction gear 34 (the width of the tooth gap).

[0047] 13 , when the parking brake is applied, the solenoid actuator 45 is activated, and the second reduction gear 35 is advanced in the axial direction relative to the first reduction gear 34, so that the thick-tooth portions 53C of the large-diameter gear 38 of the second reduction gear 35, specifically the base surface 56 and tapered surface 55 of each thick-tooth portion 53C, come into contact with the teeth 51 of the first reduction gear 34 without creating a gap 58. As a result, even when the power supply to the solenoid actuator 45 is stopped, 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 with each other without creating a gap 58, and the rotation of the second reduction gear 35 and the first reduction gear 34 is maintained in a restricted state. This makes it possible to maintain the braking state even when the power supply to the electric motor 27 and the solenoid actuator 45 is stopped.

[0048] Next, a thick tooth portion 53D according to another embodiment, which is provided on each tooth portion 50 of the large-diameter gear 38 of the second reduction gear 35, will be described with reference to FIGS. 14 and 15 . One surface of the entire tooth portion 50, including the thick tooth portion 53D, to which rotation from the electric motor 27 is transmitted when the parking brake is activated, is formed by a base surface 56 extending along the tooth trace direction. The other surface of the thick tooth portion 53D is formed by a tapered surface 55 whose chordal thickness increases toward one end in the tooth trace direction, and a base surface 56 that extends along the tooth trace direction and continues from one end of the tapered surface 55 in the tooth trace direction. The maximum chordal tooth thickness of the thick tooth portion 53D, i.e., the distance between a pair of base surfaces 56, 56 provided on both tooth surfaces of the thick tooth portion 53D, is approximately equal to the distance (width of the tooth gap) between adjacent tooth portions 51, 51 of the first reduction gear 34.

[0049] 15 , when the parking brake is applied, the solenoid actuator 45 is activated, and the second reduction gear 35 is advanced in the axial direction relative to the first reduction gear 34, so that 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, come into contact with the tooth portions 51 of the first reduction gear 34 without creating a gap 58. As a result, even when the power supply to the solenoid actuator 45 is stopped, the thick-tooth portions 53D of the large-diameter gear 38 of the second reduction gear 35 and the tooth portions 51 of the first reduction gear 34 remain in contact with each other without creating a gap 58, and the rotation of the second reduction gear 35 and the first reduction gear 34 is maintained in a restricted state. This makes it possible to maintain the braking state even when the power supply to the electric motor 27 and the solenoid actuator 45 is stopped.

[0050] 12 and 13 and the tooth thick portion 53D shown in FIGS. 14 and 15 , the surface of the entire tooth portion 50 (50) including the tooth thick portion 53C (53D), to which rotation from the electric motor 27 is transmitted when the parking brake is activated, is formed by the base surface 56 (56) extending along the tooth trace direction. Therefore, when the electric motor 27 is driven in the braking direction during parking brake activation, the base surface 56 of the entire tooth portion 50 (50) including the tooth thick portion 53C (53D) and the tooth portion 51 of the first reduction gear 34 can move linearly without any steps, thereby reducing the thrust of the solenoid actuator 45 for activating the parking brake. Furthermore, by operating the solenoid actuator 45 while rotating the electric motor 27, the thrust of the solenoid actuator 45 can be further reduced and the parking brake can be smoothly increased.

[0051] On the other hand, even when the parking brake is released, the base surface 56 of the entire tooth portion 50 (50), including the tooth thick portion 53C (53D), and the tooth portion 51 of the first reduction gear 34 are in a state where they can move linearly without any steps, so it is possible to reduce the thrust of the solenoid actuator 45 for releasing the parking brake. Also, 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 to smoothly reduce the parking brake force.

[0052] In the above description, this embodiment is employed in the disc brake 1 as an electric brake device that generates braking force by driving the electric motor 27 during braking in normal driving. However, this embodiment may also be employed in a disc brake as an electric brake device in which, during braking in normal driving, the piston 18 is advanced by the brake fluid pressure supplied into the cylinder bore 16 of the caliper body 8, thereby generating braking force through the pair of inner and outer brake pads 2, 3, and only during parking braking, such as when parking, 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 rotary-to-linear motion conversion mechanism 31, thereby advancing the piston 18, thereby generating braking force through the pair of inner and outer brake pads 2, 3.

[0053] The present invention is not limited to the above-described embodiments, but includes various modifications. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those including all of the described configurations. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, or to add the configuration of another embodiment to the configuration of one embodiment. Furthermore, it is possible to add, delete, or replace part of the configuration of each embodiment with other configurations.

[0054] This application claims priority to Japanese Patent Application No. 2023-102521, filed June 22, 2023. The entire disclosure of Japanese Patent Application No. 2023-102521, filed June 22, 2023, including the specification, claims, drawings, and abstract, is incorporated herein by reference in its entirety.

[0055] 1 Disc brake (electric brake device), 2 Inner brake pad (braking member), 3 Outer brake pad (braking member), 29 Spur tooth multi-stage reduction mechanism (reduction mechanism), 34 First reduction gear (first gear), 35 Second reduction gear, 38 Large diameter gear (second gear), 43A, 43B Switch mechanism, 50 Tooth portion, 45 Solenoid actuator (switch mechanism), 51 Tooth portion, 53A to 53D Tooth thick portion, 55 Tapered surface, 56 Base surface, 58 Gap, 60 Parking brake mechanism, D Disc rotor (braked member)

Claims

1. An electric brake device comprising: an electric motor; a reduction mechanism which amplifies the rotational torque from the electric motor; and a parking brake mechanism which converts rotation from the reduction mechanism into linear motion and maintains a pressing force which presses a braking member towards a member to be braked; wherein the reduction mechanism has a first gear and a second gear which meshes with the first gear, and a gap is provided along the rotational direction between the teeth of the first gear and the teeth of the second gear; and the parking brake mechanism comprises a switch mechanism which moves the first gear and the second gear relatively along their axial direction, and the electric brake device is configured such that the gap is present or absent depending on the operation of the switch mechanism.

2. An electric brake device as described in claim 1, wherein in the parking brake mechanism, a tooth thick portion is formed in the tooth portion of either the first gear or the second gear, where the chordal tooth thickness is large at the end in the tooth trace direction.

3. An electric brake device according to claim 2, wherein the tooth thick portion includes a tapered surface whose chordal tooth thickness gradually increases toward one end.

4. An electric brake device according to claim 3, wherein the tooth thick-walled portion includes a base surface that is continuous with one end of the tapered surface in the tooth trace direction and extends along the tooth trace direction.

5. An electric brake device as claimed in claim 3 or 4, characterized in that the surface of the entire tooth portion including the thick-walled tooth portion, to which rotation from the electric motor is transmitted when the parking brake is activated, is formed by a base surface extending along the tooth trace direction.