Electric braking system

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

Technical Field

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

Background Art

[0002] For example, in the disk brake (electric brake device) described in Patent Document 1, when the parking brake is actuated, by energizing the solenoid actuator, the plunger of the solenoid actuator is immersed, and the claw portion of the holding member moves toward the outer peripheral surface of the ratchet gear so as to oppose the biasing force of the compression coil spring, engages with the gear portion thereof, and holds the braking state. At this time, since the gear portion of the ratchet gear and the claw portion of the holding member may not engage with each other with their respective tops interfering with each other, the electric motor is rotated in the brake release direction for alignment of the two, so that the gear portion of the ratchet gear and the claw portion of the holding member are surely engaged.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the disk brake described in Patent Document 1 mentioned above, when actuating the parking brake, it is necessary to operate the solenoid actuator and the electric motor step by step for alignment of the gear portion of the ratchet gear and the claw portion of the holding member, and its control becomes complicated and there are problems in controllability. Moreover, in the disk brake described in Patent Document 1 mentioned above, as a parking brake mechanism, it is necessary to include a ratchet gear, a holding member, a locking member, a compression coil spring, etc., and its structure and layout become very complicated, and moreover, problems such as enlargement occur.

[0005] In view of the above-mentioned problems, the present invention aims to provide an electric brake device equipped with a parking brake mechanism that has good controllability, a simple structure, and is miniaturized. [Means for solving the problem]

[0006] As a means to solve the above problems, the electric brake device according to the present invention comprises an electric motor, a reduction mechanism that increases 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 there is a gap between the teeth of the first gear and the teeth of the second gear along the direction of rotation, and the parking brake mechanism is characterized in that it has a switch mechanism that moves the first gear and the second gear relative to each other along their axial direction, and the presence or absence of the gap is created by the operation of the switch mechanism.

[0007] A parking brake mechanism provided in an electric brake device according to one embodiment of the present invention has good controllability, a simple structure, and can be miniaturized. [Brief explanation of the drawing]

[0008] [Figure 1] Partial cross-sectional view of the disc brake according to this embodiment. [Figure 2] Enlarged cross-sectional view of the main part of the disc brake according to this embodiment. [Figure 3] An exploded perspective view of the parking brake mechanism used in the disc brake according to this embodiment. [Figure 4] A perspective view of the parking brake mechanism used in the disc brake according to this embodiment. [Figure 5] This is a cross-sectional view showing the state in which the plunger of a solenoid actuator is attached to the second reduction gear used in the disc brake according to this embodiment. [Figure 6] A cross-sectional view perpendicular to the radial direction of each tooth portion, including the tooth thickness portion, of the large-diameter gear of the second reduction gear used in the disc brake according to this embodiment. [Figure 7] A cross-sectional view perpendicular to the radial direction showing the teeth of the large-diameter gear of the second reduction gear used in the disc brake according to this embodiment, including the tooth thickness portion, meshing with the teeth of the first reduction gear. [Figure 8] Figure 7 shows a cross-sectional view perpendicular to the radial direction, where the second reduction gear has moved axially relative to the first reduction gear due to the operation of the solenoid actuator. [Figure 9] A cross-sectional view of the switch mechanism according to the second embodiment. [Figure 10] A cross-sectional view perpendicular to the radial direction showing the teeth of the large-diameter gear of the second reduction gear, including the tooth-thickened portion according to another embodiment, meshing with the teeth of the first reduction gear. [Figure 11] Figure 10 shows a cross-sectional view perpendicular to the radial direction, where the second reduction gear has moved axially relative to the first reduction gear due to the operation of the solenoid actuator. [Figure 12] A cross-sectional view perpendicular to the radial direction showing the teeth of the large-diameter gear of the second reduction gear, including the tooth-thickened portion according to yet another embodiment, meshed with the teeth of the first reduction gear. [Figure 13] Figure 12 shows a cross-sectional view perpendicular to the radial direction, where the second reduction gear has moved axially relative to the first reduction gear due to the operation of the solenoid actuator. [Figure 14] A cross-sectional view perpendicular to the radial direction showing the teeth of the large-diameter gear of the second reduction gear, including the tooth-thickened portion according to yet another embodiment, meshed with the teeth of the first reduction gear. [Figure 15] Figure 14 shows a cross-sectional view perpendicular to the radial direction, where the second reduction gear has moved axially relative to the first reduction gear due to the operation of the solenoid actuator. [Modes for carrying out the invention]

[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 braking force during normal driving by driving the electric motor 27. In the following description, the inner side of the vehicle will be referred to as one end, and the outer side of the vehicle will be referred to as the other end, as appropriate. That is, in Figures 1 and 2, the right side will be referred to as one end, and the left side as the other end, as appropriate.

[0010] The disc brake 1 according to this embodiment, as shown in Figure 1, comprises a pair of inner brake pads 2 and outer brake pads 3, and a caliper 4, which are arranged on both axial sides of a disc rotor D mounted on a rotating part of the vehicle. This disc brake 1 is configured as a floating caliper type. The pair of inner brake pads 2 and outer brake pads 3 and the caliper 4 are supported by a bracket 5 fixed to a non-rotating 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 braked member. The pair of inner brake pads 2 and outer brake pads 3 correspond to the braking members.

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

[0012] Inside the cylinder portion 13 of the caliper body 8, that is, in the cylinder bore 16 of the cylinder portion 13, the piston 18 is accommodated so as not to be relatively rotatable with respect to the cylinder portion 13 and to be axially movable. The piston 18 presses the inner brake pad 2 and is formed in a bottomed cup shape. The piston 18 is accommodated in the cylinder bore 16 of the cylinder portion 13 such that its bottom faces the inner brake pad 2. The piston 18 is supported so as not to be relatively rotatable with respect to the cylinder bore 16, and thus the caliper body 8, by a non-rotation engagement between its bottom and the inner brake pad 2.

[0013] A seal member (not shown) is disposed on the inner peripheral surface of the other end side of the cylinder bore 16 of the cylinder portion 13. The piston 18 is accommodated in the cylinder bore 16 so as to be axially movable while contacting this seal member. A dust boot 20 is interposed between the outer peripheral surface of the bottom side of the piston 18 and the inner peripheral surface of the other end side of the cylinder bore 16. These seal member and dust boot 20 prevent foreign matter from entering the cylinder bore 16 of the cylinder portion 13. Further, a gear housing 25 is integrally connected to the bottom wall 23 side (one end side) of the cylinder portion 13 of the caliper body 8. Inside this gear housing 25, an electric motor 27, a spur multi-stage reduction mechanism 29, and a planetary gear reduction mechanism 30, which will be described later, are disposed. Note that the one end side opening 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] 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 multi-stage reduction gear mechanism 29 and a planetary gear reduction mechanism 30 that increase the rotational torque from the electric motor 27, and a rotary-linear motion conversion mechanism 31 that converts the rotation from the planetary gear reduction mechanism 30 into linear motion and applies a thrust to the piston 18. The electric motor 27 is disposed within the gear housing 25, and its rotating shaft 27A extends toward one end side. Referring to FIG. 2, the spur multi-stage reduction gear 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 formed in a cylindrical shape and is press-fitted 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 having a large diameter that meshes with the first reduction gear 34, and a small-diameter gear 39 having a small diameter that extends axially concentrically from the large-diameter gear 38 toward one end side. The large-diameter gear 38 of the second reduction gear 35 corresponds to the second gear. Hereinafter, the configuration of the parking brake mechanism 60 having the switch mechanism 43A (solenoid actuator 45) according to the first embodiment will be described. Referring to FIGS. 3 and 5, a mounting hole 41 is provided at the radial center of the second reduction gear 35. The mounting hole 41 penetrates along the axial direction. The plunger 48 of the solenoid actuator 45 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] The plunger 48 of the solenoid actuator 45 is provided with a pair of retaining rings 42, 42 positioned to clamp the second reduction gear 35 from its axial direction. These retaining rings 42, 42 restrict the 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 employs a two-way holding type, which can maintain the position of the plunger 48 after it has moved forward and backward using a permanent magnet. As a result, it is possible to maintain the parking state even after the power supply to the solenoid actuator 45 is released after the parking brake has been activated. Referring to Figures 1 and 2, the main body 47 of the solenoid actuator 45 is located at one end.

[0017] Referring to Figures 5 and 6, each tooth portion 50 of the large-diameter gear 38 of the second reduction gear 35 has a tooth thickness portion 53A formed on one end in the tooth trace direction, where the chordal tooth thickness is larger. Referring to Figure 2, one 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 Figures 5 and 6, the tooth thickness portion 53A is constructed by forming tapered surfaces 55, 55 on both tooth surfaces, where the chordal tooth thickness increases toward one end in the tooth trace direction. Referring to Figure 8, the maximum chordal tooth thickness of the tooth thickness portion 53A is set to be greater than the distance between adjacent teeth 51, 51 of the first reduction gear 34 (tooth groove width). Referring to Figures 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 the amount equivalent to the tooth width of the tooth thickness portion 53A.

[0018] Referring to Figure 7, under normal conditions when the solenoid actuator 45 is not activated, each tooth 50 of the large-diameter gear 38 of the second reduction gear 35, including the thick-walled portion 53A, meshes with each tooth 51 of the first reduction gear 34, creating a gap 58 between each tooth 50 of the large-diameter gear 38 of the second reduction gear 35 and each tooth 51 of the first reduction gear 34. As a result, each tooth 50 of the large-diameter gear 38 of the second reduction gear 35, including the thick-walled portion 53A, and each tooth 51 of the first reduction gear 34 can slide against each other, thereby transmitting rotational torque to each other.

[0019] On the other hand, referring to Figure 8, when the parking brake is applied, the solenoid actuator 45 is activated, and the plunger 48 moves forward (protrudes) to the other end, causing the second reduction gear 35 to move forward axially relative to the first reduction gear 34. As a result, the thick-walled portions 53A of the large-diameter gear 38 of the second reduction gear 35, more specifically the tapered surfaces 55, 55 of each thick-walled portion 53A, come into contact with the teeth 51 of the first reduction gear 34, eliminating the gap 58. Consequently, 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 activated, retracting the plunger 48 to its initial position and retracting the second reduction gear 35 axially relative to the first reduction gear 34. As a result, as shown in Figure 7, each tooth 50 of the large-diameter gear 38 of the second reduction gear 35, including the thick-walled portion 53A, and each tooth 51 of the first reduction gear 34 return to their initial positions with a gap 58 between them. Consequently, each tooth 50 of the large-diameter gear 38 of the second reduction gear 35, including the thick-walled portion 53A, and each tooth 51 of the first reduction gear 34 become rotatable.

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

[0022] Furthermore, the tooth-thickened 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, and the solenoid actuator 45 may be provided on either one or the other gear. Moreover, in this embodiment, the tooth-thickened portion 53A is formed on one end side in the tooth trace direction of each tooth 50 of the large-diameter gear 38 of the second reduction gear 35, but the tooth-thickened portion 53A may also 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 retraction direction (towards one end), and when the parking brake is released, the plunger 48 of the solenoid actuator 45 moves in the protruding direction (towards the other end). The above describes the configuration of the parking brake mechanism 60 having the switch mechanism 43A (solenoid actuator 45) according to the first embodiment.

[0023] Referring to Figure 2, the small-diameter gear 39 of the second reduction gear 35 meshes with the third reduction gear 36. The third reduction gear 36 comprises 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 provided 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 circumferential surface of the large-diameter gear 62 of the third reduction gear 36 and the outer circumferential 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 disc-shaped wall portion 65. An annular stopper portion 66 is formed on the other end surface of this disc-shaped wall portion 65, protruding towards the other end, closer to its outer circumference.

[0024] The planetary gear reduction mechanism 30 comprises 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 erected from the carrier 72 (described later) is rotatably inserted. Each planetary gear 70 is arranged at equal intervals along the circumferential direction around the sun gear 63. More specifically, each planetary gear 70 is arranged at equal intervals along the circumferential direction inside 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 comprises internal teeth 78 that mesh with the gears 75 of each planetary gear 70, an annular wall portion 79 that extends radially from one end of the internal teeth 78 and restricts the 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 portion of the internal teeth 78 of the internal gear 71 is positioned 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 rotatably supported relative to the internal gear 71. The annular wall portion 79 of the internal gear 71 is positioned between each planetary gear 70 and the disc-shaped wall portion 65 of the third reduction gear 36. The internal gear 71 employs a cylindrical wall portion 80, etc., and a configuration in which an annular stopper portion 66 provided on the disc-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 in a manner that prevents relative rotation.

[0026] Rotation from the planetary gear reduction mechanism 30, that is, rotation from each planetary gear 70, is transmitted to the carrier 72. The carrier 72 is formed in a disc shape. Multiple pin holes 89 are formed on the outer circumference of the carrier 72 at intervals along the circumferential direction, corresponding 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. A spindle 93 is connected to the carrier 72 in a manner that prevents relative rotation. The spindle 93 receives rotation from the carrier 72 and transmits its rotational torque to the rotary-to-linear motion conversion mechanism 31.

[0027] Referring to Figure 1, the rotation-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 imparts thrust to the piston 18 by the movement of its linear motion member (not shown). The rotation-to-linear motion conversion mechanism 31 is located inside the cylinder bore 16 and is positioned between its bottom surface and the piston 18. When the spindle 93 rotates in conjunction with the rotation of the carrier 72, the linear motion member of the rotation-to-linear motion conversion mechanism 31 moves forward toward the other end, causing the piston 18 to move forward, and the piston 18 to press the inner brake pad 2 against the disc rotor D. The rotation-to-linear motion conversion mechanism may employ a screw mechanism, a ball screw mechanism, a ball and ramp mechanism, etc.

[0028] The electric motor 27 shown in Figure 1 is controlled by commands from a control board (not shown). During braking in normal driving, the control board controls the drive of the electric motor 27 based on detection signals from various detection sensors (not shown) that detect various situations requiring braking, such as detection sensors (not shown) that respond to the driver's requests, and detection signals from rotation angle detection means (not shown) and thrust sensors (not shown). This control board is also electrically connected to a parking brake switch (not shown), and the operation of the solenoid actuator 45 is controlled by commands from the control board.

[0029] Next, the braking and brake release functions of the disc brake 1 according to this embodiment will be described during normal driving. During braking in normal operation, 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 gear 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 on its own axis of rotation and revolve around the axis of rotation of the sun gear 63, thereby causing the carrier 72 to rotate. In other words, the rotation from the electric motor 27 is reduced and amplified at a predetermined reduction ratio via the spur gear multi-stage reduction mechanism 29 and the planetary gear reduction mechanism 30 and transmitted to the carrier 72. Then, the rotation from the carrier 72 is transmitted to the spindle 93.

[0030] Next, as the spindle 93 rotates in conjunction with the rotation of the carrier 72, the linear motion member of the rotation-to-linear motion conversion mechanism 31 moves forward, causing the piston 18 to move forward. This forward movement of the piston 18 presses the inner brake pad 2 against the disc rotor D. Then, due to the 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) relative to the bracket 5, and the claw portions 14, 14 press the outer brake pad 3 against the disc rotor D. 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.

[0031] On the other hand, when the brake is 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 of the rotation-to-linear motion conversion mechanism 31 retracts and returns to its initial state, and the braking force applied to the disc rotor D by the pair of inner and outer brake pads 2 and 3 is released.

[0032] Next, the operation of the parking brake in the disc brake 1 according to this embodiment will be described. When the parking brake switch is operated, the electric motor 27 is driven by a command from the control board, just as during normal braking, and its 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. Subsequently, as the spindle 93 rotates in conjunction with the rotation from the carrier 72, the piston 18 moves forward due to the action of the rotation-to-linear motion conversion mechanism 31, and the disc rotor D is clamped between the pair of inner and outer brake pads 2 and 3, generating braking force.

[0033] In this state, a command from the control board energizes the solenoid actuator 45, causing the plunger 48 of the solenoid actuator 45 to move forward. As a result, the second reduction gear 35 moves forward axially relative to the first reduction gear 34, and the thick-walled portions 53A (each tapered surface 55, 55) of the large-diameter gear 38 of the second reduction gear 35 and the teeth 51 of the first reduction gear 34 come into contact without any gaps, i.e., no gaps 58 are created. As a result, even if a rotational torque in the braking 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 after the braking force has been generated, the second reduction gear 35 and the first reduction gear 34 will not rotate. Then, the power supply to the electric motor 27 is stopped, and after confirming the pressing force of the pair of inner and outer brake pads 2 and 3 against the disc rotor D, the power supply to the solenoid actuator 45 is stopped.

[0034] Furthermore, since the solenoid actuator 45 employs a two-way holding type that can maintain the position of the plunger 48 by a permanent magnet, even when the power supply to the solenoid actuator 45 is stopped, the thick-walled portion 53A of each tooth of the large-diameter gear 38 of the second reduction gear 35 and the teeth 51 of the first reduction gear 34 are kept in contact without any gap 58, and the rotation of the second reduction gear 35 and the first reduction gear 34 is 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 stopped, and the operation of the parking brake is completed.

[0035] Next, to release the parking brake, a command from the control board energizes the solenoid actuator 45, causing the plunger 48 of the solenoid actuator 45 to retract to its initial position. As a result, the system returns to its initial state where a gap 58 is created between each tooth portion 50, including the thick-walled 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. Subsequently, a command from the control board causes the rotating shaft 27A of the electric motor 27 to rotate in the reverse direction, i.e., the brake release direction, and this reverse rotation 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, the linear motion member of the rotation-to-linear motion conversion mechanism 31 retracts and returns to its initial position, releasing the braking force applied to the disc rotor D by the pair of inner and outer brake pads 2 and 3.

[0036] Furthermore, based on a command from the control board, the parking brake may be activated by the operation of the electric motor 27 and the solenoid actuator 45, and after a certain period of time, a control (also called a re-clamp operation) may be performed to release the operation of the parking brake by the solenoid actuator 45 while simultaneously activating the parking brake again by the aforementioned electric motor 27, if necessary. This prevents a decrease in the thrust of the parking brake that occurs when the parking brake is activated at high temperatures immediately after braking, due to thermal contraction of the inner and outer brake pads 2 and 3 and the disc rotor D as the temperature drops.

[0037] As described above, the parking brake mechanism 60 provided in the disc brake 1 according to this embodiment includes 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, moves the second reduction gear 35 relative to the first reduction gear 34 along its axial direction, and the operation of the solenoid actuator 45 creates the presence or absence of a gap 58 between the tooth thickness 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 electric motor in stages to align the gear portion of the ratchet gear with the pawl portion of the retaining member, as in the conventional (described in Patent Document 1), and the parking brake can be operated steplessly, resulting in improved controllability. Moreover, as in the conventional, it is not necessary to provide a ratchet gear, retaining member, locking member, and compression coil spring as a parking brake mechanism, and its structure and layout are greatly simplified, enabling miniaturization.

[0039] Furthermore, conventional parking brakes employ frictional force through a clutch mechanism, but frictional force is subject to many variability factors such as surface roughness of the contact area, deformation and surface condition, environmental conditions, and deterioration over time, making it challenging to ensure highly robust reliability. In contrast, the parking brake mechanism 60 according to this embodiment is configured such that the thick-walled 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 come into contact without any gap 58 due to the operation of the solenoid actuator 45. This improves 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 includes a solenoid actuator 45 as a switch mechanism 43A for moving the second reduction gear 35 in its axial direction. The solenoid actuator 45 employs a two-way holding type that can maintain the position of the plunger 48 by permanent magnet even after the power supply is stopped after operation, thus preventing malfunctions such as the parking brake being accidentally activated due to driving vibrations.

[0041] Next, the switch mechanism 43B according to the 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 and 102 that are screwed onto the rotating shaft 100A and position the second reduction gear 35 by sandwiching it from both axial sides. Specifically, the first nut member 101 is positioned on one end side of the small-diameter gear 39 of the second reduction gear 35. On the other hand, the second nut member 102 is positioned 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 and 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 its axial direction. The rotating shaft 100A of the electric motor 100 is rotatably inserted through the support hole 105 of the second reduction gear 35. When the electric motor 100 is operated and the rotating shaft 100A is rotated in the forward or reverse direction, the first and second nut members 101 and 102 move forward or backward, and consequently, the second reduction gear 35 moves forward or backward along its axial direction. In this embodiment, the first and second nut members 101 and 102 are screwed together with the rotating shaft 100A by a screw mechanism, but other known rotary-to-linear motion conversion mechanisms such as a ball screw mechanism or a roller screw mechanism may be used.

[0043] Next, a tooth thickness portion 53B according to another embodiment, 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 tooth thickness portion 53B is constructed by forming a tapered surface 55 on both tooth surfaces, where the chordal tooth thickness increases toward one end in the tooth trace direction, and a base surface 56 that extends along the tooth trace direction, continuously from one end of the tapered surface 55 in the tooth trace direction. The maximum chordal tooth thickness of the tooth thickness portion 53B, that is, the distance between the pair of base surfaces 56, 56 provided on both tooth surfaces of the tooth thickness portion 53B, is approximately the same as the distance between adjacent teeth 51, 51 of the first reduction gear 34 (tooth groove width).

[0044] When the parking brake is applied, as shown in Figure 11, the solenoid actuator 45 is activated, and the second reduction gear 35 moves forward axially relative to the first reduction gear 34. This causes the thick-walled portions 53B of the large-diameter gear 38 of the second reduction gear 35, more specifically the pair of base surfaces 56, 56 of each thick-walled portion 53B, to come into contact with the teeth 51 of the first reduction gear 34 without any gap 58. As a result, even when the power supply to the solenoid actuator 45 is stopped, the contact between the thick-walled portions 53B of the large-diameter gear 38 of the second reduction gear 35 and the teeth 51 of the first reduction gear 34 is maintained without any gap 58, and the rotation of the second reduction gear 35 and the first reduction gear 34 is restricted. This allows the braking state to be maintained even when the power supply to the electric motor 27 and the solenoid actuator 45 is stopped.

[0045] In the thick-walled tooth section 53A shown in Figures 6 to 8, the control of the stroke amount of the plunger 48 of the solenoid actuator 45 for holding the parking brake becomes somewhat complicated due to the numerous variation factors, such as wear and deformation over time due to the contact between each tapered surface 55 of the thick-walled tooth section 53A and each tooth 51 of the first reduction gear 34, environmental conditions, and deterioration over time. In contrast, in the thick-walled tooth section 53B shown in Figures 10 and 11, the influence of the aforementioned variation factors can be reduced by providing a pair of base surfaces 56, 56, thus simplifying the control of the stroke amount of the plunger 48 of the solenoid actuator 45 for holding the parking brake. Moreover, in the thick-walled tooth section 53B shown in Figures 10 and 11, the influence of the aforementioned variation factors can be reduced by providing a pair of base surfaces 56, 56, so the thrust required for the solenoid actuator 45 can be reduced, making it possible to miniaturize it.

[0046] Next, a tooth thickness portion 53C provided on each tooth portion 50 of the large-diameter gear 38 of the second reduction gear 35, according to another embodiment, will be described with reference to Figures 12 and 13. One side of the entire tooth portion 50, including the tooth thickness 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 side of the tooth thickness 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 thickness portion 53C is set to be greater than the distance (width of the tooth groove) between adjacent teeth 51, 51 of the first reduction gear 34.

[0047] When the parking brake is applied, as shown in Figure 13, the solenoid actuator 45 is activated, and the second reduction gear 35 moves forward axially relative to the first reduction gear 34. This causes the thick-walled 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-walled portion 53C, to come into contact with the teeth 51 of the first reduction gear 34 without any gap 58. As a result, even when the power supply to the solenoid actuator 45 is stopped, the contact between the thick-walled portions 53C of the large-diameter gear 38 of the second reduction gear 35 and the teeth 51 of the first reduction gear 34 is maintained without any gap 58, and the rotation of the second reduction gear 35 and the first reduction gear 34 is restricted. This allows the braking state to be maintained even when the power supply to the electric motor 27 and the solenoid actuator 45 is stopped.

[0048] Next, a tooth thickness portion 53D provided on each tooth portion 50 of the large-diameter gear 38 of the second reduction gear 35, according to another embodiment, will be described with reference to Figures 14 and 15. One side of the entire tooth portion 50, including the tooth thickness 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 side of the tooth thickness 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 that extends continuously from one end of the tapered surface 55 in the tooth trace direction along the tooth trace direction. The maximum chordal tooth thickness of the tooth thickness portion 53D, that is, the distance between the pair of base surfaces 56, 56 provided on both tooth surfaces of the tooth thickness portion 53D, is approximately the same as the distance between adjacent teeth 51, 51 of the first reduction gear 34 (tooth groove width).

[0049] When the parking brake is applied, as shown in Figure 15, the solenoid actuator 45 is activated, causing the second reduction gear 35 to advance axially relative to the first reduction gear 34. This causes the thick-walled 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-walled portion 53D, to come into contact with the teeth 51 of the first reduction gear 34 without any gap 58. As a result, even when the power supply to the solenoid actuator 45 is stopped, the contact between the thick-walled portions 53D of the large-diameter gear 38 of the second reduction gear 35 and the teeth 51 of the first reduction gear 34 is maintained without any gap 58, and the rotation of the second reduction gear 35 and the first reduction gear 34 is restricted. This allows the braking state to be maintained even when the power supply to the electric motor 27 and the solenoid actuator 45 is stopped.

[0050] As explained above, in the tooth thickness portion 53C shown in Figures 12 and 13, and the tooth thickness portion 53D shown in Figures 14 and 15, the surface of the entire tooth portion 50(50), including the tooth thickness portion 53C(53D), to which rotation from the electric motor 27 is transmitted when the parking brake is activated is formed by a base surface 56(56) that extends along the tooth trace direction. Therefore, when the electric motor 27 is driven in the braking direction when the parking brake is activated, the base surface 56 of the entire tooth portion 50(50), including the tooth thickness portion 53C(53D), and the tooth portion 51 of the first reduction gear 34 can move in a straight line without any steps, thus 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, it is possible to further reduce the thrust of the solenoid actuator 45 and increase the force of the parking brake smoothly.

[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 thickness portion 53C (53D), and the tooth portion 51 of the first reduction gear 34 are in a state where they can move in a straight line without any step difference, so the thrust of the solenoid actuator 45 for releasing the parking brake can be reduced. Furthermore, 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 reduce the force of the parking brake smoothly.

[0052] In the above description, this embodiment is used in a disc brake 1 as an electric brake device that generates braking force by driving an electric motor 27 during braking in normal driving. However, this embodiment may also be used in a disc brake as an electric brake device in which, during braking in normal driving, the brake fluid pressure supplied to the cylinder bore 16 of the caliper body 8 advances the piston 18, generating braking force with a pair of inner and outer brake pads 2 and 3, and only when the parking brake is applied, such as when parking, the rotation from the electric motor 27 is transmitted to the piston 18 via a spur gear multi-stage reduction mechanism 29, a planetary gear reduction mechanism 30, and a rotation-to-linear motion conversion mechanism 31, thereby advancing the piston 18 and generating braking force with a pair of inner and outer brake pads 2 and 3.

[0053] Furthermore, the present invention is not limited to the embodiments described above, and various modifications are included. For example, the embodiments described above are described in detail to make the present invention easier to understand, and are not necessarily limited to those having all the configurations described. Also, it is possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. In addition, it is possible to add, delete, or replace parts of the configuration of each embodiment with other configurations.

[0054] This application claims priority under Japanese Patent Application No. 2023-102521, filed on 22 June 2023. The entire disclosure of Japanese Patent Application No. 2023-102521, filed on 22 June 2023, including the specification, claims, drawings, and abstract, is incorporated into this application by reference. [Explanation of symbols]

[0055] 1 Disc brake (electric braking 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~53D Tooth thickness portion, 55 Tapered surface, 56 Base surface, 58 Gap, 60 Parking brake mechanism, D Disc rotor (braked member)

Claims

1. An electric brake device, wherein the electric brake device is Electric motor and, A reduction mechanism that increases the rotational torque from the electric motor, A parking brake mechanism that converts rotation from the reduction mechanism into linear motion and maintains a pressing force that presses the braking member toward the braked member, Equipped with, The reduction mechanism comprises a first gear and a second gear that meshes with the first gear. There is a gap between the teeth of the first gear and the teeth of the second gear along the direction of rotation. The parking brake mechanism includes a switch mechanism that moves the first gear and the second gear relative to each other along their axial directions. An electric brake device characterized in that the operation of the switch mechanism causes the presence or absence of the aforementioned gap.

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

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

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

5. In the electric brake device according to claim 3 or 4, An electric brake device characterized in that the surface of the entire tooth portion, including the tooth thickness 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.

Images