Electric braking system

Abstract

Provided is an electric brake device with which ease of mounting in a vehicle is improved by achieving both a reduction in the size of a speed reduction mechanism for reducing the rotational speed from an electric motor, and a reduction in the size of a parking brake mechanism. The parking brake mechanism comprises a lock wheel that is rotated by the drive of an electric motor, a lock nut capable of moving in an axial direction of the lock wheel while rotating, and the electric motor, for driving the lock nut, wherein, in a state in which a clutch surface of the lock nut is in contact with the lock wheel, the lock nut presses against the lock wheel by way of the clutch surface, concomitant with the rotation of the lock wheel in a direction releasing a braking force, thereby suppressing the rotation of the lock wheel and maintaining the braking force. This makes it possible to achieve both a reduction in the size of the speed reduction mechanism and a reduction in the size of the parking brake mechanism, thereby improving the ease of mounting in a vehicle.

Description

Technical Field

[0001] The present invention relates to an electric brake device used for braking a vehicle, and more particularly to an electric brake device with a parking brake.

Background Art

[0002] Patent Document 1 discloses an electric brake device including an electric motor, an electric brake mechanism unit including a speed reducer and a rotary-linear motion conversion mechanism that converts the rotational motion of the electric motor to generate a braking force, and a parking brake mechanism that holds the braking force. The parking brake mechanism described in Patent Document 1 is configured as a so-called ratchet mechanism. More specifically, the ratchet mechanism mainly includes a pawl wheel integrally attached to a motor rotor, an engagement pawl member that can engage with or disengage from a plurality of pawl portions formed at regular intervals on the pawl wheel, and a solenoid that operates the engagement pawl member.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] According to the parking brake mechanism (ratchet mechanism) described in Patent Document 1, as mentioned above, the reverse torque generated by the reaction force of the parking braking force is applied to the engaging part of the ratchet mechanism via the electric brake mechanism. For this reason, rotational torque is continuously applied to the reduction mechanism, which is one of the components of the electric brake mechanism, and there are limitations on miniaturizing the reduction mechanism from the standpoint of suppressing creep deformation of the resin material. On the other hand, since the ratchet mechanism is subjected to impact load by the inertia of the motor rotor, etc., the engaging part requires a corresponding level of strength and durability. In other words, if the parking brake mechanism is to be placed after the reduction, where the rotational torque is greater, in order to suppress the rotational torque applied to the reduction mechanism, there is a risk that the engaging part will become so large that it greatly impairs the vehicle's mountability.

[0005] Furthermore, one of the objectives of the present invention is to provide an electric braking device that improves vehicle mountability by achieving both miniaturization of the reduction mechanism for reducing rotation from the electric motor and miniaturization of the parking brake mechanism. [Means for solving the problem]

[0006] As a means to solve the above problems, the first electric brake device of the present invention comprises an electric motor, an electric brake mechanism that generates a braking force by pressing a braking member against a member to be braked by driving the electric motor, and a parking brake mechanism that holds the braking force generated by the electric brake mechanism, wherein the parking brake mechanism Rotational motion transmitted to the electric brake mechanism A rotating body that rotates, a rotation-to-linear motion conversion mechanism including a rotation-to-linear motion member that can move in the axial direction of the rotating body while rotating, and a mechanism that drives the rotation-to-linear motion conversion mechanism. , separate from the aforementioned electric motor The system comprises a drive device, and the rotary linear motion member has a clutch portion that contacts or separates from the rotating body. The aforementioned drive device activates the rotation-to-linear motion conversion mechanism, thereby controlling the rotation-to-linear motion member. In the state in which the clutch portion is in contact with the rotating body, The electric brake mechanism transmitted The rotation of the rotating body is suppressed by the rotational linear motion member pressing against the rotating body via the clutch portion as the rotating body rotates in a direction that releases the braking force.

[0007] Furthermore, the second electric brake device of the present invention comprises an electric motor, an electric brake mechanism that generates a braking force by pressing a braking member against a member to be braked by the drive of the electric motor, and a parking brake mechanism that maintains the braking force generated by the electric brake mechanism, wherein the parking brake mechanism Rotational motion transmitted to the electric brake mechanism A rotating body that rotates, a rotary linear motion member that is movable in the axial direction of the rotating body while rotating and has a clutch portion that contacts the rotating body, and a mechanism that drives the rotary linear motion member , separate from the aforementioned electric motor Equipped with a drive unit, The drive device moves the rotary linear member toward the rotating body, When the clutch portion is in contact with the rotating body, the rotational linear motion member is applied to the rotating body. The electric brake mechanism transmitted The rotation of the rotating body is suppressed by a torque reaction force against the rotational torque in the direction of release of the braking force.

[0008] In an electric brake device according to one embodiment of the present invention, it is possible to achieve both miniaturization of the reduction mechanism that reduces the rotation from the electric motor and miniaturization of the parking brake mechanism, thereby improving vehicle mountability. [Brief explanation of the drawing]

[0009] [Figure 1] A perspective view of the disc brake according to this embodiment. [Figure 2] A view of the disc brake according to this embodiment, seen from one end. [Figure 3] A cross-sectional view of the disc brake according to this embodiment. [Figure 4] Enlarged view of section A in Figure 3. [Figure 5] Enlarged view of section B in Figure 3. [Figure 6] Enlarged view of section C in Figure 3. [Figure 7] Enlarged view of section D in Figure 3. [Figure 8] An operation diagram showing the activation of the parking brake by the parking brake mechanism according to the first embodiment. [Figure 9] An operation diagram showing the activation of the parking brake by the parking brake mechanism according to the first embodiment. [Figure 10]Operation diagram when the parking brake is actuated by the parking brake mechanism according to the first embodiment. [Figure 11] Operation diagram when the parking brake is released by the parking brake mechanism according to the first embodiment. [Figure 12] Operation diagram when the parking brake is released by the parking brake mechanism according to the first embodiment. [Figure 13] Diagram showing the transition of the braking force (F), the current value (Iclp) to the electric motor for generating the braking force, and the current value (Ipkb) to the electric motor for holding the braking force over time when the parking brake is actuated and released by the parking brake mechanism according to the first embodiment. [Figure 14] Diagram showing the relationship between the braking force (F) and the current value (Iclp) to the electric motor for generating the braking force. [Figure 15] Cross-sectional view of the parking brake mechanism according to the second embodiment. [Figure 16] Cross-sectional view of the parking brake mechanism according to the third embodiment.

Mode for Carrying Out the Invention

[0010] Hereinafter, this embodiment will be described in detail based on FIGS. 1 to 16. The disc brake 1 according to the embodiment of the present invention is an electric brake device that generates a braking force by driving an electric motor 50 during normal driving. In the following description, the inner side of the vehicle (inner side) is referred to as one end side (housing cover 92 side), and the outer side of the vehicle (outer side) is referred to as the other end side (disc rotor D side) for appropriate explanation.

[0011] Referring to FIGS. 1 to 3, the disk brake 1 according to the present embodiment includes a pair of inner brake pads 2 and outer brake pads 3 disposed on both axial sides of a disk rotor D attached to a rotating part of a vehicle, sandwiching the disk rotor D, and a caliper 4. The present disk brake 1 is configured as a caliper floating type. The pair of inner brake pads 2 and outer brake pads 3 and the caliper 4 are supported by a carrier 5 fixed to a non-rotating part such as a knuckle of the vehicle so as to be movable in the axial direction of the disk rotor D with respect to the carrier 5. The pair of inner brake pads 2 and outer brake pads 3 correspond to braking members. On the other hand, the disk rotor D corresponds to a braked member. In FIGS. 1 and 2, the illustration of the disk rotor D is omitted.

[0012] Referring to FIG. 1, the carrier 5 includes a pair of pin support portions 12A and 12B on which slide pins 10A and 10B are respectively supported, and inner and outer support portions 14 and 15 that are integrally connected to the pair of pin support portions 12A and 12B and independently support the inner and outer brake pads 2 and 3 respectively. The pair of pin support portions 12A and 12B are arranged at intervals along the rotation direction of the disk rotor D and both extend along the axial direction of the disk rotor D. Each pin support portion 12A and 12B is formed in a substantially cylindrical shape. The slide pins 10A and 10B integrally extend from the inner end faces of the respective pin support portions 12A and 12B toward one end side. The inner side support portion 14 is integrally connected to the inner side of the pin support portions 12A and 12B. The outer side support portion 15 is integrally connected to each of the pin support portions 12A and 12B at an interval on the outer side along the axial direction of the disk rotor D from the inner side support portion 14.

[0013] The inner support portion 14 consists of a pair of inner arm portions 20, 20 (only one is shown in Figure 1) extending in substantially perpendicular directions from each pin support portion 12A, 12B, and an inner beam portion 21 connecting the ends of the pair of inner arm portions 20, 20. The inner brake pad 2 is supported inside the pair of inner arm portions 20, 20 so as to be movable along the axial direction of the disc rotor D. Through holes 22, 22 are formed at both ends of the inner beam portion 21 in the rotational direction of the disc rotor D, respectively, passing through along the axial direction of the disc rotor D (only one is shown in Figure 1).

[0014] The carrier 5 is attached to the non-rotating part of the vehicle via through holes 22, 22 provided in the inner support portion 14 (inner beam portion 21). The outer support portion 15 consists of a pair of outer arm portions 23, 23 extending in substantially perpendicular directions from the pin support portions 12A, 12B, and an outer beam portion 24 connecting the ends of the pair of outer arm portions 23, 23. The outer brake pad 3 is supported inside the pair of outer arm portions 23, 23 so as to be movable along the axial direction of the disc rotor D.

[0015] Referring to Figures 1 and 3, the caliper 4 comprises a caliper body 30, which is the main body of the caliper 4, a drive mechanism 31, and a parking brake mechanism 32A according to the first embodiment. The caliper body 30 is integrally formed with a cylindrical cylinder portion 34 which is located on the base end side facing the inner brake pad 2 on the inside of the vehicle and opens facing the inner brake pad 2, a pair of claw portions 35, 35 which extend from the cylinder portion 34 across the disc rotor D to the outer side and are located on the tip side facing the outer brake pad 3 on the outer side, and a pair of caliper arm portions 36A, 36B which extend radially outward from the cylinder portion 34.

[0016] Referring to Figure 2, a piston 40 is supported within the cylinder bore of the cylinder section 34 so as to be movable along the axial direction. During braking, the driving force from the drive mechanism 31 is transmitted to the piston 40, causing the piston 40 to advance toward the disc rotor D and press against the inner brake pad 2. On the other hand, when braking is released, the driving force from the drive mechanism 31 is also transmitted to the piston 40, causing the piston 40 to retract away from the inner brake pad 2.

[0017] A sealing member 37 is positioned on the inner circumferential surface of the other end of the cylinder bore of the cylinder section 34. The piston 40 is housed in the cylinder bore so as to be movable along the axial direction while in contact with this sealing member 37. A dust boot 38 is interposed between the outer circumferential surface of the bottom side of the piston 40 and the inner circumferential surface of the other end of the large-diameter cylinder bore. These sealing member 37 and dust boot 38 prevent foreign matter from entering the cylinder bore of the cylinder section 34. Referring to Figure 1, of the pair of caliper arms 36A and 36B, a bottomed cylindrical boss portion 42 is integrally provided protruding toward the inner side from the tip of one of the caliper arms 36A. The boss portion 42 extends along the axial direction of the disc rotor D. One slide pin 10A extending from one piston support portion 12A is slidably inserted into the boss portion 42 along the axial direction.

[0018] Furthermore, of the pair of caliper arms 36A and 36B, a through hole 44 is formed at the tip of the other caliper arm 36B, which penetrates the disc rotor D in the axial direction. The other slide pin 10B is made of a hexagonal bolt having a hexagonal head. The hexagonal bolt, which is the slide pin 10B, is inserted through the through hole 44 of the other caliper arm 36B and screwed into the inner end face of the other pin support 12B. An axial gap is provided between the inner end face around the through hole 44 of the other caliper arm 36B and the hexagonal head of the other slide pin 10B (hexagonal bolt), and a pin boot 45 with an expandable and contractible bellows section is provided to cover this gap. The pair of slide pins 10A and 10B allow the caliper body 30 to be slidably supported relative to the carrier 5 along the axial direction of the disc rotor D (wheel).

[0019] Referring to Figure 3, the drive mechanism 31 includes an electric motor 50, a reduction mechanism 51 that increases the rotational torque from the electric motor 50, and a thrust-generating mechanism 52 that converts the rotational motion from the reduction mechanism 51 into linear motion and imparts thrust to the piston 40. The thrust-generating mechanism 52 corresponds to the electric brake mechanism. The electric motor 50 is positioned so that the axial direction of its main body 53 is approximately parallel to the longitudinal direction of the cylinder portion 34 of the caliper body 30. The main body 53 of the electric motor 50 is housed in a housing 75, which will be described later. The reduction mechanism 51 is also housed in the housing 75.

[0020] Referring to Figure 1, the main body 53 of the electric motor 50 is positioned on an extension line along the axial direction with respect to a boss portion 42 provided on one caliper arm portion 36A. The main body 53 of the electric motor 50 is positioned parallel to the cylinder portion 34 along its radial direction. Referring to Figure 3, the main body 53 of the electric motor 50 is fixed to the housing 75 by a plurality of fastening members 56. The rotating shaft 54 ​​of the electric motor 50 extends to one end, that is, the side opposite to the inner and outer brake pads 2 and 3. Referring also to Figure 4, a ring-shaped magnetic member 59 constituting a rotation angle detection means 58 is attached to the tip of the rotating shaft 54.

[0021] Referring to Figures 3 and 4, the rotation angle detection means 58 detects the rotation angle of the rotation shaft 54 ​​of the electric motor 50. The rotation angle detection means 58 includes a magnetic member 59 and a magnetic detection IC chip (not shown). The magnetic detection IC chip is electrically connected to a control board 230 positioned opposite the tip surface of the rotation shaft 54. The magnetic detection IC chip detects changes in the magnetic field generated from the magnetic member 59. By detecting changes in the magnetic flux from the magnetic member 59, which rotates in conjunction with the rotation of the rotation shaft 54 ​​of the electric motor 50, the control board 230 calculates and detects the rotation angle of the rotation shaft 54 ​​of the electric motor 50. A terminal portion 55 extends from the main body portion 53 of the electric motor 50 toward one end. This terminal portion 55 is electrically connected to the control board 230. Power is supplied to the electric motor 50 based on commands from the control board 230.

[0022] Referring to Figures 3 and 4, the reduction mechanism 51 is composed of a multi-stage, multi-axis gear reduction mechanism. The gears are of the spur gear or helical gear type. The reduction mechanism 51 increases the rotational torque from the electric motor 50 and transmits it to the thrust-generating mechanism 52. The reduction mechanism 51 includes a pinion gear 62 fixed to the rotating shaft 54 ​​of the electric motor 50, a first reduction gear 63 that meshes with the pinion gear 62, and a second reduction gear 64 that meshes with the first reduction gear 63. These first reduction gear 63 and second reduction gear 64 are made of resin material.

[0023] Referring to Figure 4, the pinion gear 62 is press-fitted and fixed onto the rotating shaft 54 ​​of the electric motor 50. The first reduction gear 63 is rotatably supported by the first shaft 66. The first shaft 66 is fixed between the housing 75 and the inner plate 76, which will be described later. The first reduction gear 63 comprises a small gear 69 located at one end and a large gear 70 located at the other end, which is integrally connected concentrically to the small gear 69. The large gear 70 of the first reduction gear 63 meshes with the pinion gear 62. The first reduction gear 63 is positioned between the housing 75 and the inner plate 76, which will be described later, and its axial movement is restricted.

[0024] The second reduction gear 64 is rotatably supported by a second shaft 67. The second shaft 67 is fixed between the housing 75 and the inner plate 76, which will be described later. The second reduction gear 64 comprises a large gear 72 located at one end and a small gear 73 located at the other end, which is integrally connected concentrically to the large gear 72. The large gear 72 of the second reduction gear 64 meshes with the small gear 69 of the first reduction gear 63. The small gear 73 of the second reduction gear 64 meshes with the gear portion 94A of the gear plate 94, which will be described later. The second reduction gear 64 is positioned between the housing 75 and the inner plate 76, which will be described later, and its axial movement is restricted. In this embodiment, the reduction mechanism 51 is configured as a multi-stage multi-axis gear reduction mechanism, but other known reduction mechanisms such as friction drive wheels, belts and pulleys, chains and sprockets may be used.

[0025] Referring to Figures 3 and 5, the housing 75 is made of a metal such as cast iron or aluminum die-cast so as to receive the reaction force from the thrust-applying mechanism 52 (reaction force to the pressing force from the pair of inner and outer brake pads 2 and 3 to the disc rotor D) via the thrust detection sensor 215, which will be described later. The housing 75 mainly houses the electric motor 50 and reduction mechanism 51 of the drive mechanism 31, and the parking brake mechanism 32A. The space in the housing 75 that houses the electric motor 50 is hermetically sealed from the other end by a motor cover member 86.

[0026] An inner plate 76 is positioned at one end of the space within the housing 75 where the reduction gear mechanism 51 is located. The housing 75 supports the thrust detection sensor 215, which will be described later, and also houses the bearing plate 100 and the gear plate 94, etc. The housing 75 is fixed to the cylinder section 34 via a sealing member 90. Referring to Figure 3, the opening at one end of the housing 75 is hermetically closed by the housing cover 92 via a sealing member 91. As a result, the inside of the housing 75 is hermetically sealed.

[0027] Referring to Figure 5, the thrust-applying mechanism 52 comprises a gear plate 94, a center bolt 95, a sliding screw engagement portion 96, and a roller screw mechanism 97. The gear plate 94 is a component of the first thrust bearing 99. The first thrust bearing 99 comprises a bearing plate 100, the gear plate 94, a plurality of thrust balls 101, and a retainer 102. The bearing plate 100 is formed in an annular shape. The bearing plate 100 has an insertion hole 105 through which the center bolt 95 is inserted at its radial center. The bearing plate 100 is restricted from relative rotation with respect to the housing 75. An annular raceway 111 is formed on the other end face of the bearing plate 100, on which the plurality of thrust balls 101 roll.

[0028] Referring to Figure 4, the small gear 73 of the second reduction gear 64 of the reduction mechanism 51 meshes with the gear plate 94. Referring to Figure 5, the gear plate 94 is formed in an annular shape. A gear portion 94A is formed on the outer circumferential surface of the gear plate 94. The small gear 73 of the second reduction gear 64 of the reduction mechanism 51 meshes with the gear portion 94A of the gear plate 94. Rotation from the rotating shaft 54 ​​of the electric motor 50 is transmitted to the gear plate 94 via the reduction mechanism 51. Referring to Figures 5 and 6, a through hole 113 through which a center bolt 95 is inserted is formed in the radial center of the gear plate 94. An annular recess 114 is formed on the outer circumferential surface of the other end face of the gear plate 94. An annular raceway 115 on which a plurality of thrust balls 101 roll is formed on one end face of the gear plate 94.

[0029] Multiple thrust balls 101 are arranged to roll freely between the raceway 111 of the bearing plate 100 and the raceway 115 of the gear plate 94. The retainer 102 restricts the circumferential position of each thrust ball 101. As a result, the multiple thrust balls 101 are held at a constant interval in the circumferential direction by the retainer 102. A pin 118 is provided on the gear plate 94, protruding from the bottom surface of its annular recess 114 toward the other end. Referring to Figure 7, the gear portion 94A of the gear plate 94 also meshes with the gear portion 362 of the lock wheel 308, which will be described later. As described above, in the rotation transmission path from the electric motor 50, a reduction mechanism 51 is arranged between the electric motor 50 and the lock wheel 308.

[0030] Referring to Figures 5 and 6, a male threaded portion 124 is formed on the center bolt 95, extending from one end towards the other in the axial direction. The axial end of the center bolt 95 is housed in the insertion hole 105 of the bearing plate 100. The relative movement of the bearing plate 100 toward the one end relative to the center bolt 95 is restricted. The axial end of the center bolt 95 and the insertion hole 105 of the bearing plate 100 are engaged by splines, serrations, or press-fitted and fixed. As a result, the relative movement of the center bolt 95 and the bearing plate 100 along the axial direction is restricted, as is their relative rotation. Since the relative rotation of the bearing plate 100 with respect to the housing 75 is restricted, the relative rotation of the center bolt 95 with respect to the housing 75 is also restricted. The center bolt 95 is inserted through the insertion hole 113 of the gear plate 94 via a radial bearing 128. As a result, the center bolt 95 and the gear plate 84 can rotate relative to each other by the radial bearing 128.

[0031] Referring to Figure 5, a washer 130 is positioned on one end face of the cylinder portion 34. A spring 131 is positioned between the washer 130 and the other end face of the gear plate 94. The biasing force of this spring 131 biases the gear plate 94 toward one end relative to the cylinder portion 34, thereby suppressing the separation between the first thrust bearing 99, the axial end of the center bolt 95, and the thrust detection sensor 215.

[0032] Referring to Figures 5 and 6, the sliding screw engagement portion 96 is composed of a threaded portion between the male threaded portion 124 of the center bolt 95 and the female threaded portion 143 of the nut member 135, which will be described later. This sliding screw engagement portion 96 allows the nut member 135 to rotate relative to the center bolt 95 and move relative to the axial direction when the nut member 135 is rotated in the apply or release direction. The sliding screw engagement portion 96 is set to have a reverse efficiency greater than zero. As a result, the axial thrust acting on the nut member 135 allows it to move forward and backward while rotating. A roller screw mechanism 97 is arranged around the male threaded portion 124 of the center bolt 95 on the other end of the gear plate 94.

[0033] The roller screw mechanism 97 comprises a nut member 135, a plurality of planetary rollers 136, and a roller nut member 137. The nut member 135 is positioned around the male threaded portion 124 of the center bolt 95. The nut member 135 comprises a cylindrical body portion 140 and a frustoconical portion 141 integrally connected to the other end of the cylindrical body portion 140. A female threaded portion 143 is formed on the inner circumferential surface of the cylindrical body portion 140 of the nut member 135 near one end. As a result, as described above, a sliding screw engagement portion 96 is formed between the male threaded portion 124 of the center bolt 95 and the female threaded portion 143 of the nut member 135. Annular grooves 145 are formed at a predetermined pitch along the axial direction on the outer circumferential surface of the cylindrical body portion 140 of the nut member 135 near one end. Each of these annular grooves 145 engages with each annular peak 178 provided on the outer circumferential surface of each planetary roller 136.

[0034] The frustoconical portion 141 of the nut member 135 is constructed with its outer circumferential surface widening toward the other end. The second thrust bearing 147 comprises the frustoconical portion 141 of the nut member 135, a plurality of thrust balls 148, a push plate 149, and a retainer 150. An annular raceway 152 on which the plurality of thrust balls 148 roll is formed on the other end face of the frustoconical portion 141 of the nut member 135. A holder fitting hole 154 with a larger diameter than the female thread portion 143 is formed in the frustoconical portion 141. An annular locking groove 156 is formed on the inner circumferential surface of the holder fitting hole 154. The push plate 149 is positioned opposite the other end face of the frustoconical portion 141. The push plate 149 is formed in an annular shape with an insertion hole 158 through which the male thread portion 124 of the center bolt 95 is inserted.

[0035] The inner diameter of the insertion hole 158 of the push plate 149 is approximately the same as the inner diameter of the holder fitting hole 154 of the nut member 135. A locking recess 160 is formed on the other end face of the push plate 149 around the insertion hole 158. A retaining ring 162 is placed between the outer circumferential surface of the push plate 149 and the inner circumferential surface of the piston 40 to prevent it from coming loose. An annular raceway 164 is formed on one end face of the push plate 149 on which a plurality of thrust balls 148 roll. The plurality of thrust balls 148 are arranged to roll freely between the raceway 164 of the push plate 149 and the raceway 152 of the nut member 135. The retainer 150 restricts the circumferential position of each thrust ball 148. As a result, the plurality of thrust balls 148 are held by the retainer 150 at a constant interval in the circumferential direction.

[0036] Referring to Figures 5 and 6, the bearing holder 168 is inserted from the inner circumferential surface of the insertion hole 158 of the push plate 149 into the holder fitting hole 154 of the nut member 135 (frustoconical portion 141). The bearing holder 168 is formed in a cylindrical shape. An annular locking portion 170 is formed on the outer circumferential surface of the other end of the bearing holder 168, projecting radially outward. Multiple elastic pieces 172 are provided on the outer circumference of the bearing holder 168 at predetermined intervals along the circumferential direction. Each elastic piece 172 is formed by cutting into the outer circumferential wall of the bearing holder 168. Each elastic piece 172 elastically deforms so as to retract radially inward from its outer circumferential wall. A locking claw portion 174 is provided at the tip of each elastic piece 172, projecting radially outward.

[0037] The locking claw portion 174 can extend and retract radially from the outer circumferential surface of the bearing holder 168 by the elastic deformation of the elastic piece 172. The bearing holder 168's annular locking portion 170 engages with the locking recess 160 of the push plate 149, and the locking claw portions 174 of each elastic piece 172 engage from the inside with the locking groove portion 156 of the frustoconical portion 141 of the nut member 135. As a result, the bearing holder 168 can integrally hold the push plate 149 together with the thrust ball 148 including the retainer 150 at the other end of the frustoconical portion 141 of the nut member 135.

[0038] Referring to Figures 5 and 6, a plurality of planetary rollers 136 are engaged with the outer circumference of the cylindrical body portion 140 of the nut member 135 at intervals along the circumferential direction. The planetary rollers 136 have annular ridges 178 formed on their outer circumferential surface at a predetermined pitch along the axial direction. Each annular ridge 178 of the planetary roller 136 engages with each annular groove portion 145 provided on the outer circumferential surface of the nut member 135 (cylindrical body portion 140). As a result, the relative movement of the nut member 135 and each planetary roller 136 in the axial direction is restricted. These planetary rollers 136 are held by a roller holding unit 180.

[0039] The roller holding unit 180 holds each planetary roller 136, which engages with the outer circumferential surface of the cylindrical body portion 140 of the nut member 135, together with the cover member 182 and the compression coil spring 184, integrated into the roller cage 186. The roller holding unit 180 is supported so as to be rotatable together with the nut member 135 and so as to be movable in the axial direction together with the nut member 135. The roller holding unit 180 comprises the roller cage 186, the cover member 182, and the compression coil spring 184. The roller cage 186 is formed in a cylindrical shape as a whole. Multiple roller housing holes 190 for housing each planetary roller 136 are formed in the circumferential wall of the roller cage 186 at intervals along the circumferential direction. Each roller housing hole 190 is formed in a roughly rectangular shape in plan view, elongated in the axial direction. The circumferential length (width) of each roller housing hole 190 is such that it can accommodate a planetary roller 136, and is approximately equal to the outer diameter of the planetary roller 136. The axial length of each roller housing hole 190 is slightly larger than the length of the planetary roller 136.

[0040] A cover member 182 is positioned radially outward of the roller cage 186. The cover member 182 comprises a cylindrical cover body portion 193 and a plurality of spring support portions 194 protruding from the cover body portion 193 to the other end. The axial length of the cover body portion 193 is approximately equal to the axial length of the roller cage 186. Multiple roller insertion holes 196 are formed in the peripheral wall portion of the cover body portion 193 at intervals along the circumferential direction, into which each planetary roller 136 is inserted. Each roller insertion hole 196 is formed corresponding to each roller housing hole 190 provided in the roller cage 186. Each roller insertion hole 196 is formed in a roughly rectangular shape in plan view, with an elongated axial direction. The circumferential length (width) of each roller insertion hole 196 is slightly greater than the circumferential length (width) of each roller housing hole 190 provided in the roller cage 186. The axial length of each roller insertion hole 196 is slightly greater than the length of the planetary roller 136.

[0041] Multiple spring support portions 194 are provided projecting from the other end face of the cover body portion 193 toward the other end. These spring support portions 194 are provided at intervals in the circumferential direction. A spring receiving portion 195 projecting inward is formed at the tip (other end) of each spring support portion 194. A compression coil spring 184 is positioned within each spring support portion 194 of the cover member 182 at the other end of the roller cage 186. One end of the compression coil spring 184 abuts against the other end face of the roller cage 186, and the other end abuts against the spring receiving portion 195 of each spring support portion 194 of the cover member 182.

[0042] The roller cage 186 and the cover member 182 are connected so that they cannot rotate relative to each other. At this time, the compression coil spring 184 is compressed so that each roller insertion hole 196 of the cover member 182 and each roller housing hole 190 of the roller cage 186 face each other, and one end of the compression coil spring 184 is brought into contact with the other end face of the roller cage 186. The planetary rollers 136 are housed in the opposing roller insertion holes 196 of the cover member 182 and each roller housing hole 190 of the roller cage 186, and each annular peak 178 of each planetary roller 136 is engaged with each annular groove 145 of the nut member 135.

[0043] Furthermore, due to subtle misalignments in the placement of the roller insertion holes 196 of the cover member 182 and the roller housing holes 190 of the roller cage 186, and differences in their sizes, at the engagement points between the annular peaks 178 of half of the planetary rollers 136 and the annular grooves 145 of the nut member 135, a load (contact pressure, frictional force) directed toward one end is applied by the biasing force of the compression coil spring 184. On the other hand, at the engagement points between the annular peaks 178 of the remaining half of the planetary rollers 136 and the annular grooves 145 of the nut member 135, an axial load (contact pressure, frictional force) directed toward the other end is applied by the biasing force of the compression coil spring 184.

[0044] Referring to Figures 5 and 6, the roller nut member 137 is constructed by integrally connecting a large-diameter roller nut portion 200 opening at one end and a small-diameter roller nut portion 201 opening at the other end. An engagement recess 203 is formed on one end face of the large-diameter roller nut portion 200. An engagement groove portion 205 is formed on the large-diameter roller nut portion 200, extending from an axial intermediate position toward the other end. The engagement projection 133 of the washer 130 engages with the engagement groove portion 205 of the large-diameter roller nut portion 200, thereby restricting their relative rotation. In short, the washer 130 is allowed to move along the axial direction relative to the roller nut member 137, but its relative rotation is restricted. One end face of the large-diameter roller nut portion 200 abuts against the bottom surface of the annular recess 114. The outer circumferential surface of the large-diameter roller nut portion 200 abuts against the inner circumferential surface of the annular recess 114. Furthermore, the pin 118 of the gear plate 94 engages with the engagement recess 203 of the large-diameter roller nut portion 200.

[0045] As a result, the relative rotation of the roller nut member 137 and the gear plate 94 is restricted. A retaining ring 207 is interposed between the outer circumferential surface of one end of the large-diameter roller nut portion 200 and the inner circumferential surface of the annular recess 114 of the gear plate 94. This retaining ring 207 functions to prevent the roller nut member 137 from coming loose after being assembled into the annular recess 114 of the gear plate 94. In addition, a retaining ring 209 is provided on the outer circumferential surface of the other end of the large-diameter roller nut portion 200. This retaining ring 209 allows the thrust-applying mechanism 52 to be sub-assembled with the addition of a washer 130 and a spring 131, improving ease of assembly to the cylinder portion 34.

[0046] A female threaded portion 212 is formed on the inner circumferential surface of the roller nut member 137. This female threaded portion 212 is provided over substantially the entire axial area of ​​the roller nut member 137. This female threaded portion 212 of the roller nut member 137 engages with (meets) each annular peak 178 of each planetary roller 136. The female threaded portion 212 of the roller nut member 137 and each annular peak 178 of the planetary roller 136 are meshed with each other by having the same pitch for the female threaded portion 212 and the same pitch (axial spacing) for each annular peak 178, and by setting the number of threads in the female threaded portion 212 to an integer multiple of the number of planetary rollers 136.

[0047] Referring to Figure 5, the thrust detection sensor 215 detects the reaction force to the thrust (pressure) from the piston 40 to the inner and outer brake pads 2 and 3. The thrust detection sensor 215 is composed of a solid load cell. The thrust detection sensor 215 is supported by the housing 75. The tip of the terminal portion 222 extending from one end of the thrust detection sensor 215 is electrically connected to the control board 230.

[0048] Referring to Figure 3, the electric motor 50 is electrically connected to the control board 230 by terminals 55, and the drive of the electric motor 50 is controlled by commands from the control board 230. The control board 230 is positioned close to the housing cover 92. The control board 230 is fixed to the inner plate 76 by fastening members 231. The control board 230 is electrically connected to a plurality of terminals 234 provided on one end of the connector 233. A harness (not shown) used for power supply from the vehicle and communication such as braking commands is hermetically connected to the control board 230 via the connector 233. The connector 233 is hermetically fixed to the housing 75 via a sealing member 235. Note that the connector 233 is not shown in Figures 1 and 2.

[0049] Furthermore, for communication such as braking commands, the control board 230 is electrically connected via harnesses and connectors 233 to various detection sensors that detect driver requests, such as a stroke sensor that detects the stroke of a brake pedal (not shown), and to various situations where braking is required without a driver request. The control board 230 is electrically connected to the magnetic detection IC chip of the rotation angle detection means 58. The control board 230 is electrically connected to the thrust detection sensor 215.

[0050] During braking in normal driving, the control board 230 controls the drive of the electric motor 50 based on detection signals from various detection sensors that detect various situations requiring braking, such as detection sensors that respond to the driver's requests, detection signals from the magnetic detection IC chip of the rotation angle detection means 58, and detection signals from the thrust detection sensor 215. The control board 230 is also electrically connected to a parking brake switch (not shown) and a brake pedal (not shown) that is operated to instruct the operation of the parking brake, and the operation of the electric motor 300 of the parking brake mechanism 32A according to the first embodiment is controlled by commands from the control board 230.

[0051] Referring to Figures 3 and 7, the parking brake mechanism 32A according to the first embodiment is located within the housing 75. Referring to Figures 1 and 2, the parking brake mechanism 32A is located on the opposite side from the electric motor 50 with respect to the cylinder bore (piston 40) of the cylinder portion 34. The parking brake mechanism 32A is located between one through hole 22 provided in the inner support portion 14 (inner beam portion 21) and the other slide pin 10B, which is a hexagonal bolt having a hexagonal head. Referring to Figure 7, the parking brake mechanism 32A according to the first embodiment includes an electric motor 300, a reduction mechanism 304, a rotary-to-linear motion conversion mechanism 306, and a lock wheel 308. The lock wheel 308 corresponds to a rotating body. Also referring to Figure 3, the axial direction of the main body 301 of the electric motor 300 coincides with the axial direction of the main body 53 of the electric motor 50. In short, the main body 301 of the electric motor 300 and the main body 53 of the electric motor 50 are located parallel to each other. The rotating shaft 302 from the main body 301 of the electric motor 300 extends in the same direction as the rotating shaft 54 ​​from the main body 53 of the electric motor 50, and they extend parallel to each other.

[0052] Referring to Figure 7, a sub-housing 250 is provided inside the housing 75 to house an electric motor 300, a reduction mechanism 304, a rotary-to-linear motion conversion mechanism 306, and a lock wheel 308, etc. The sub-housing 250 is made of molded resin. One end opening of the sub-housing 250 is closed by a mount base 253. The mount base 253 is made of molded resin. The other end of the mount base 253 is fixed to the housing 75 via a collar member 257 by a fastening member 255. The other end opening of the cylindrical portion 251 of the sub-housing 250 is closed by a motor cover member 259. In short, one end of the motor cover member 259 is snap-fitted to the outer circumferential surface of the other end of the cylindrical portion 251 of the sub-housing 250. The motor cover member 259 is made of molded resin.

[0053] Meanwhile, the other end of the mount base 253 is snap-fitted to the outer circumferential surface of one end of the cylindrical portion 251 of the sub-housing 250. The main body 301 of the electric motor 300 is then housed and supported within the cylindrical portion 251 of the sub-housing 250 via a pair of support members 314, 314. The support members 314 are made of rubber, elastomer, or the like. In this embodiment, the motor cover member 259 and the mount base 253 are snap-fitted to the cylindrical portion 251 of the sub-housing 250, but they may be joined by other known techniques such as ultrasonic welding.

[0054] Referring to Figure 7, a terminal portion 310 extends from the main body portion 301 of the electric motor 300 toward one end. This terminal portion 310 is electrically connected to a terminal portion 311 that is insert-molded into the sub-housing 250. A terminal portion 312 at one end of the terminal portion 311 is electrically connected to the control board 230. In this embodiment, the electric motor 300 is a DC brush motor, but other known rotary motors such as brushless motors may be used. The rotation from the rotating shaft 302 of the electric motor 300 is transmitted to the reduction mechanism 304. The reduction mechanism 304 is composed of a multi-stage multi-axis gear reduction mechanism. The gears are of the spur gear or helical gear type. The reduction mechanism 304 includes a pinion gear 315 that is press-fitted and fixed onto the rotating shaft 302 of the electric motor 300, and a reduction gear 317 that meshes with the pinion gear 315. The reduction gear 317 is made of resin material.

[0055] The reduction gear 317 is rotatably supported by a shaft 319. The shaft 319 is fixed to the sub-housing 250 and the mount base 253. The reduction gear 317 comprises a large gear 321 located at one end and a small gear 322 located at the other end, which is integrally connected concentrically to the large gear 321. The large gear 321 of the reduction gear 317 meshes with the pinion gear 315. The reduction gear 317 is positioned between the sub-housing 250 and the mount base 253, and its axial movement is restricted. In this embodiment, the reduction mechanism 304 is configured as a multi-stage multi-axis gear reduction mechanism, but other known reduction mechanisms such as friction drive wheels, belts and pulleys, chains and sprockets may be used.

[0056] The small gear 322 of the reduction gear 317 of the reduction mechanism 304 meshes with the lock nut 330 of the rotary-to-linear motion conversion mechanism 306. The rotary-to-linear motion conversion mechanism 306 is a screw mechanism 325. The screw mechanism 325 comprises a center shaft 328 and a lock nut 330 that screws onto the male threaded portion 338 of the center shaft 328. The lock nut 330 corresponds to the rotary-to-linear motion member. The center shaft 328 comprises a disc-shaped head 333, a screw-type large-diameter shaft portion 334 integrally connected from the head 333 to the other end and having a male threaded portion 338 formed on its outer circumference, and a small-diameter shaft portion 335 integrally connected from the screw-type large-diameter shaft portion 334 to the other end. The head 333 of the center shaft 328 is insert-molded into the mount base 253. As a result, the relative movement (including rotation) of the center shaft 328 with respect to the housing 75, including the sub-housing 250, is restricted. Furthermore, a projection 340 is provided on the other end face of the head 333 of the center shaft 328, extending toward the other end.

[0057] The lock nut 330 has a circular outer shape and has an axially extending female thread portion 342 formed in the radial center. A gear portion 344 is formed on one end of the outer circumferential surface of the lock nut 330. The small gear 322 of the reduction gear 317 of the reduction mechanism 304 meshes with the gear portion 344 of the lock nut 330. The other end of the lock nut 330 is rotatably supported by the sub-housing 250. The female thread portion 342 of the lock nut 330 is screwed onto the male thread portion 338 of the large diameter threaded shaft portion 334 of the center shaft 328. A clutch surface 346 is formed on the other end of the lock nut 330, which gradually decreases in diameter towards the other end. The clutch surface 346 corresponds to the clutch portion. A projection 348 is provided on one end face of the lock nut 330, extending toward the end.

[0058] When the rotation from the electric motor 300 is transmitted to the lock nut 330 via the reduction mechanism 304, the lock nut 330 rotates clockwise when viewed from one end and moves forward toward the other end. When the lock nut 330 rotates and moves backward due to the rotation from the electric motor 300, if it moves backward too far, the projection 348 on the lock nut 330 interferes with the projection 340 on the center shaft 328, thereby suppressing excessive backward movement of the lock nut 330 and preventing the screw from jamming.

[0059] A lock wheel 308 is positioned on the other end of the lock nut 330. The lock wheel 308 has a circular outer shape and a through hole 352 extending axially is formed in the radial center. A recess 353 is formed on the other end face of the lock wheel 330. The inner circumferential surface of the recess 353 coincides with the inner circumferential surface of the annular plate portion 357, which will be described later. The small diameter shaft portion 335 of the center shaft 328 is inserted through the through hole 352 of the lock wheel 308. The lock wheel 308 is then rotatably supported on the center shaft 328.

[0060] Furthermore, a thrust plate 355 is fixed with an insert to close the opening in the sub-housing 250 that faces the other end face of the lock wheel 308. The small-diameter shaft portion 335 of the center shaft 328 is inserted through a through hole 356 in the thrust plate 355 that closes the opening in the sub-housing 250 and is supported by the housing 75. An annular plate portion 357 is provided on the outer circumference of one end face of the lock wheel 308, projecting toward the one end and having a larger diameter than the outer diameter of the lock wheel 308. A clutch surface 358 is formed on the inner circumferential surface of one end of the annular plate portion 357, with the opening diameter gradually increasing toward the one end.

[0061] As the lock nut 330 rotates and moves forward toward the lock wheel 308, the clutch surface 346 of the lock nut 330 and the clutch surface 358 of the annular plate portion 357 of the lock wheel 308 come into contact. In other words, the clutch surface 346 of the lock nut 330 and the clutch surface 358 of the annular plate portion 357 of the lock wheel 308 engage in frictional engagement with each other through their tapered surfaces. Rotation is transmitted between the lock nut 330 and the lock wheel 308 only when the clutch surface 346 of the lock nut 330 and the clutch surface 358 of the annular plate portion 357 of the lock wheel 308 are in contact.

[0062] The lock wheel 308 is restricted from axial relative movement with respect to the center shaft 328 by a pair of retaining rings 360, 360 provided at both ends in the axial direction. A gear portion 362 is formed on the outer circumferential surface of the lock wheel 308. This gear portion 362 is formed over the entire axial area of ​​the lock wheel 308. This gear portion 362 of the lock wheel 308 meshes with the gear portion 94A of the gear plate 94 of the thrust-applying mechanism 52. In the parking brake mechanism 32A according to the first embodiment, a two-stage reduction mechanism 304 via a reduction gear 317 is employed, but a pinion gear 315, which is press-fitted and fixed to the rotating shaft 302 of the electric motor 300, may be directly meshed with the gear portion 344 of the lock nut 330 of the rotary-to-linear motion conversion mechanism 306 to configure a single-stage reduction mechanism.

[0063] Furthermore, in the parking brake mechanism 32A according to the first embodiment, a lock wheel 308 is provided separately as a component. However, the parking brake mechanism 32A may be arranged to lock a component during reduction, for example, by configuring the second reduction gear 64 (see Figure 4) of the reduction mechanism 51 as the lock wheel. In this embodiment, a clutch surface can be provided on one end of the second reduction gear 64, and a rotation-to-linear motion conversion mechanism 306 can be provided on the other end. Moreover, in the parking brake mechanism 32A according to the first embodiment, the clutch surface 358 of the annular plate portion 357 of the lock wheel 308 and the clutch surface 346 of the lock nut 330 are configured as a friction clutch. However, a clutch according to other known technologies, such as a dog clutch with a grooved engagement portion, may be used.

[0064] Next, the operation of the disc brake 1 according to this embodiment during braking in normal driving will be explained. During braking in normal driving, detection signals from detection sensors that respond to the driver's requests and detection sensors that detect various situations requiring braking are input to the control board 230 via the harness and connector 233. The control board 230 also receives detection signals from a rotation angle detection means 58 that detects the rotation angle of the rotation shaft 54 ​​of the electric motor 50, and detection signals from a thrust detection sensor 215 that detects the thrust (reaction force against pressing force) from the inner and outer brake pads 2 and 3 to the disc rotor D. Furthermore, power is supplied to the electric motor 50 from a power supply unit (not shown) via the harness and connector 233 and through the control board 230.

[0065] The control board 230 operates the drive mechanism 31 based on these detection signals. Specifically, the electric motor 50 is rotationally driven based on a braking command from the vehicle and power supplied from the control board 230. When the electric motor 50 is rotationally driven, its rotation in the forward direction, i.e., the braking direction, is transmitted to the gear plate 94 via the reduction mechanism 51. In this way, the rotation from the electric motor 50 is reduced and amplified at a predetermined reduction ratio by passing through the reduction mechanism 51 and then transmitted to the gear plate 94.

[0066] Next, as the gear plate 94 rotates, the roller nut member 137 rotates. Also, referring to Figure 8, as the gear plate 94 rotates, the lock wheel 308 of the parking brake mechanism 32A also rotates (it rotates counterclockwise when viewed from one end), but since the clutch surface 358 of the lock wheel 308 and the clutch surface 346 of the lock nut 330 are separated, the lock wheel 308 simply remains in a state of rotation. The rotational torque transmitted to the roller nut member 137 is then transmitted to each planetary roller 136 via the engagement portion (meshing portion) between each annular peak 178 of each planetary roller 136 and each female thread portion 212 of the roller nut member 137. The rotational torque transmitted to each planetary roller is then transmitted to the nut member 135 via the engagement portion between each annular peak 178 of each planetary roller 136 and each annular groove portion 145 of the nut member 135.

[0067] The rotational torque transmitted to the nut member 135 is transmitted to the center bolt 95 via the sliding screw engagement portion 96 between the female thread portion 143 of the nut member 135 and the male thread portion 124 of the center bolt 95. However, since the center bolt 95 is supported so as to be unable to rotate relative to the cylinder portion 34 (caliper body 30), the nut member 135 rotates and moves to the other end. At this time, each planetary roller 136 rotates on its own axis of rotation and revolves in the apply direction around the axis of the roller nut member 137, moving to the other end together with the nut member 135. The roller holding unit 180, including each planetary roller 136, also moves to the other end together with the nut member 135.

[0068] Then, as the nut member 135 moves to the other end, the push plate 149 is pressed against the bottom of the piston 40 via multiple thrust balls 148. The piston 40 then moves from its original position when not braking to the other end, while elastically deforming the seal member 37, and presses the inner brake pad 2 against the disc rotor D. Almost simultaneously, the caliper 4 moves to one end relative to the carrier 5 due to the reaction force against the pressing force on the inner brake pad 2 by the piston 40, and the outer brake pad 3, which is in contact with the claw portions 35, 35, is pressed 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 friction and creating braking force for the vehicle.

[0069] Furthermore, during braking, the reaction force to the pressing force from the pair of inner and outer brake pads 2 and 3 onto the disc rotor D due to the movement of the piston 40 is applied to the thrust detection sensor 215 in the order of push plate 149 → each thrust ball 148 → nut member 135 → sliding screw engagement part 96 → center bolt 95, while the thrust detection sensor 215 is also applied in the order of push plate 149 → each thrust ball 148 → nut member 135 → each planetary roller 136 → roller nut member 137 → gear plate 94 → each thrust ball 101 → bearing plate 100 → center bolt 95.The detection result from the thrust detection sensor 215 is then transmitted to the control board 230, which controls the power supply to the electric motor 50 so that the detection result from the thrust detection sensor 215 reaches a target value.

[0070] Next, the operation of the parking brake in the disc brake 1 according to this embodiment will be described. When the parking brake switch or brake pedal is operated to engage the parking brake, the electric motor 50 is driven by power supplied from the control board 230, just as during normal braking as described above. Ultimately, the disc rotor D is clamped between the pair of inner and outer brake pads 2 and 3, generating friction and creating braking force for the vehicle. When this braking force reaches the target value, the control board 230 activates the parking brake mechanism 32A based on this signal. That is, based on the signal that the braking force has reached the target value, the electric motor 300 is rotated by power supplied from the control board 230 (time t2 in Figure 13).

[0071] Here, the electric motor 50 is controlled by the control board 230 to maintain its position. Referring to Figures 13 and 14, the drive mechanism 31 can maintain a constant pressing force Fa even when the current value to the electric motor 50 is reduced from Ia to Ib. Therefore, at time t2, the current value to the electric motor 50 is reduced from Ia to Ib to maintain the position of the piston 40. The relationship between the currents Ia and Ib to the electric motor 50 for any pressing force is determined using map settings written to the control board 230. Alternatively, the amount of current supplied to the electric motor 50 may be controlled so that the pressing force detected by the thrust detection sensor 215 decreases by a predetermined value, and then the piston 40 may be controlled to maintain that position.

[0072] Next, referring to Figure 9, when the electric motor 300 rotates due to power supplied from the control board 230, the lock nut 330 of the rotary-to-linear motion conversion mechanism 306 rotates clockwise when viewed from one end via the reduction gear 317 of the reduction mechanism 304. As a result, because the movement of the center shaft 328, including rotation, is restricted relative to the housing 75, the lock nut 330 moves forward toward the other end while rotating in the same direction. Subsequently, the clutch surface 346 of the lock nut 330 comes into contact with the clutch surface 358 of the annular plate portion 357 of the lock wheel 308, generating a pressing force.

[0073] As this pressing force increases, referring to Figure 13, the current to the electric motor 300 of the parking brake mechanism 32A increases, and after detecting that the current value has exceeded a predetermined value Ic, the current to the electric motor 50 is reduced (times t3 to t4 in Figure 13). Then, referring to Figure 10, the rotation direction of the lock wheel 308 begins to coincide with the rotation direction of the lock nut 330 by the electric motor 300 (clockwise when viewed from one end), causing the lock nut 330 to advance further toward the other end, which increases the pressing force between the clutch surface 346 of the lock nut 330 and the clutch surface 358 of the annular plate portion 357 of the lock wheel 308.

[0074] Next, after the power supply to the electric motor 50 is stopped by the control board 230, the power supply to the electric motor 300 of the parking brake mechanism 32A is also stopped (time t4 in Figure 13). At this time, the thrust-applying mechanism 52 starts reverse operation in the direction of releasing the pressing force due to the reaction force received from the piston 40. Then, referring to Figure 10, the reaction force converted into rotational torque by the thrust-applying mechanism 52 is transmitted to the lock wheel 308 via the gear plate 94 as rotational torque in a clockwise direction when viewed from one end. This rotational torque to the lock wheel 308 is then transmitted from the lock wheel 308 to the lock nut 330 as rotational torque in a clockwise direction when viewed from one end, via the clutch surface 358 of the annular plate portion 357 of the lock wheel 308 and the clutch surface 346 of the lock nut 330, which are in contact with each other. As a result, the lock nut 330 moves further forward to the other end, further increasing the pressing force between the clutch surface 346 of the lock nut 330 and the clutch surface 358 of the annular plate portion 357 of the lock wheel 308.

[0075] Subsequently, the drive mechanism 31 and the parking brake mechanism 32A stop and are held in place at a position where the reverse rotational torque in the direction of releasing the pressing force from the gear plate 94 to the lock wheel 308 balances the torque reaction force due to the pressing force between the clutch surface 346 of the lock nut 330 and the clutch surface 358 of the lock wheel 308, and the parking brake lock is completed.

[0076] In the parking brake mechanism 32A according to the first embodiment, the lock wheel 308, including the rotation-to-linear motion conversion mechanism 306 and the clutch surface 358, undergoes slight axial elastic deformation until the pressing force necessary to maintain braking force is reached. This deformation can be easily modified by adjusting the diameter of the male threaded portion 338 of the center shaft 328 and the female threaded portion 342 of the lock nut 330, which is advantageous for reducing rigidity compared to conventional ratchet mechanisms. In other words, since no impact load like that of a ratchet mechanism is applied, and it can be structurally advantageous, the parking brake mechanism 32A can be placed between the reduction mechanism 51 and the thrust-applying mechanism 52 in the rotation transmission path.

[0077] Therefore, since the reduction mechanism 51 is not subjected to rotational torque, which is a reaction force from the braking force, sufficient strength and durability to prevent creep deformation of the resin material are not required, and the reduction mechanism 51 can be made smaller. Furthermore, as shown in Figure 2, the parking brake mechanism 32A can be positioned in the empty space on the opposite side of the electric motor 50, relative to the cylinder bore (piston 40) of the cylinder section 34, thus improving vehicle mountability.

[0078] Furthermore, in the parking brake mechanism 32A according to the first embodiment, the pressing force generated between the clutch surface 346 of the lock nut 330 and the clutch surface 358 of the annular plate portion 357 of the lock wheel 308 utilizes a reverse torque in the direction that releases the braking force from the thrust-applying mechanism 52. Therefore, the electric motor 300 of the parking brake mechanism 32A only needs to bring the clutch surface 346 of the lock nut 330 into contact with the clutch surface 358 of the annular plate portion 357 of the lock wheel 308, making the electric motor 300 smaller and reducing current consumption.

[0079] Furthermore, in the parking brake mechanism 32A according to the first embodiment, the thrust-applying mechanism 52 operates slightly in reverse until the braking position is maintained by the parking brake mechanism 32A, causing the braking force from the piston 40 to decrease from Fa to Fb, as shown in Figure 13. Therefore, this decrease in braking force may be written to the control board 230 as a map setting value, and the target value Fa may be set higher in anticipation of this decrease.

[0080] Next, when the parking brake switch or brake pedal is operated to release the parking brake, the electric motor 50 is driven by power supplied from the control board 230. At this time, referring to Figure 11, the direction of rotation of the electric motor 50 is the same as the direction of rotation when the parking brake is activated, and it is the direction in which the braking force by the piston 40 increases. In other words, as the electric motor 50 rotates, the lock wheel 308 of the parking brake mechanism 32A rotates counterclockwise when viewed from one end. Subsequently, after detecting that the current value to the electric motor 50 has become greater than or equal to a predetermined Id (referring to Figure 13), the parking brake mechanism 32A starts supplying power to the electric motor 300 (time t6 in Figure 13). At this time, the direction of rotation of the electric motor 300 is the opposite direction to when the parking brake is activated, and its rotation is transmitted to the lock nut 330 via the reduction mechanism 304, causing the lock nut 330 to rotate counterclockwise when viewed from one end and move backward toward the one end. The control board 230 controls the power supply to the electric motor 50 to continue increasing during this time.

[0081] By supplying power to the electric motors 50 and 300, the lock wheel 308 and lock nut 330 rotate counterclockwise when viewed from one end, causing the lock nut 330 to retract toward the one end. As a result, the clutch surface 346 of the lock nut 330 and the clutch surface 358 of the annular plate portion 357 of the lock wheel 308 separate. As this rotation occurs, the current flowing to the electric motor 300 decreases, and after detecting that it has fallen below a predetermined value Ie, the power supply is controlled so that the electric motor 50 maintains its position (time t7 in Figure 13). Subsequently, after detecting that the current value to the electric motor 300 is the predetermined value Ie, power is continued to be supplied to the electric motors 300 and 50 for a predetermined time Ta to ensure that the pressing force applied to the lock nut 330 of the parking brake mechanism 32A is reliably released (times t7-t8 in Figure 13).

[0082] Next, in order to ensure that the clutch surface 346 of the lock nut 330 and the clutch surface 358 of the annular plate portion 357 of the lock wheel 308 are separated and a predetermined gap is secured, power is supplied to the electric motor 300 for a predetermined time Tb, and then the power supply is stopped (Figure 13, time t8~t9). Meanwhile, at the time it is determined that the pressing force applied to the lock nut 330 of the parking brake mechanism 32A has been released (time t8 in Figure 13), the electric motor 50 is controlled to rotate in the direction in which the piston 40 retracts due to the reaction force from the holding state (time t8 in Figure 13). At this time, referring to Figure 12, the lock wheel 308 has already begun to separate from the lock nut 330, so the lock wheel 308 can rotate freely in the direction in which the braking force by the piston 40 decreases (clockwise when viewed from one end), regardless of the rotation state of the lock nut 330. Then, the braking force from the piston 40 is released, and after the vehicle has moved to a predetermined reversing distance to prevent brake drag, the power supply to the electric motor 50 is stopped (time t10 in Figure 13). In this way, the parking brake is released.

[0083] Thus, in the parking brake mechanism 32A according to the first embodiment, the release of the parking brake can be determined from the change in the current value of the electric motor 300, thus improving reliability. Note that the ratchet mechanism described in Patent Document 1 does not have a means to directly detect whether or not the engaging pawl member has disengaged. In contrast, in the parking brake mechanism 32A according to the first embodiment, the release of the pressing force on the rotational-to-linear motion conversion mechanism 306 (lock nut 330) and the securing of the gap between the clutch surface 346 of the lock nut 330 and the clutch surface 358 of the annular plate portion 357 of the lock wheel 308 can be determined by whether or not predetermined times Ta and Tb have elapsed. However, these determinations may also be made by estimating the rotational speed based on the applied voltage and current value to the electric motor 300, and further determining the amount of rotation from the power supply time information, and then determining whether or not a predetermined amount of rotation has been reached. Furthermore, according to the parking brake mechanism 32A of the first embodiment, the predetermined current value used to determine whether or not the rotation direction of the electric motor 50 can be reversed is set to a value close to the maximum value Ia (see Figure 13) during parking operation stored in the RAM of the control board 230, but it may be adjusted to other values.

[0084] As described above, the parking brake mechanism 32A according to the first embodiment, provided in the disc brake 1 according to this embodiment, includes a lock wheel 308 that rotates when driven by an electric motor 50, a rotation-to-linear motion conversion mechanism 306 including a lock nut 330 that can move in the axial direction of the lock wheel 308 while rotating, and an electric motor 300 that drives the rotation-to-linear motion conversion mechanism 306. The lock nut 330 has a clutch surface 346 that contacts or separates from the lock wheel 308. When the clutch surface 346 of the lock nut 330 is in contact with the lock wheel 308, as the lock wheel 308 rotates in the direction that releases the braking force, the lock nut 330 presses against the lock wheel 308 via the clutch surface 346, thereby suppressing the rotation of the lock wheel 308 and maintaining the braking force.

[0085] In other words, when the clutch surface 346 of the lock nut 330 is in contact with the lock wheel 308, the lock nut 330 can maintain braking force by suppressing the rotation of the lock wheel 308 with a torque reaction force against the rotational torque in the direction of release of the braking force applied to the lock wheel 308. As a result, the parking brake mechanism 32A according to the first embodiment does not employ a ratchet mechanism as in the conventional, making it easier to ensure strength and durability and enabling miniaturization.

[0086] Furthermore, according to the parking brake mechanism 32A of the first embodiment, rotational alignment is not required to engage the pawl member and the pawl wheel, as is the case with conventional ratchet mechanisms. In other words, the parking brake can be activated regardless of the rotational position of the lock wheel 308, so the pressing force can be adjusted steplessly rather than discretely. In addition, operation control to prevent incomplete engagement between the pawl member and the pawl gear and to ensure reliable engagement is not required, which simplifies the control algorithm and improves reliability.

[0087] Furthermore, conventional ratchet mechanisms have difficulty ensuring strength and durability, and the vast majority of them lock at a position with low rotational torque, namely the electric motor 50 or the first stage of the multi-stage reduction gear. As a result, conventional ratchet mechanisms have the problem of requiring larger gears because the reduction gear mechanism is subjected to a continuous torque load while parked.

[0088] In contrast, in the parking brake mechanism 32A according to the first embodiment, the rotary-to-linear motion conversion mechanism 306 employs a screw mechanism 325, which ensures the strength and durability of the rotary-to-linear motion conversion mechanism 306, and allows the rotational torque to be locked even after deceleration when the rotational torque is large.

[0089] Furthermore, in the parking brake mechanism 32A according to the first embodiment, a reduction mechanism 51 is provided between the electric motor 50 and the lock wheel 308 in the rotation transmission path from the electric motor 50. As a result, while parked, the reduction mechanism 51 is not subjected to rotational torque, which is a reaction force due to the braking force. Therefore, sufficient strength and durability to prevent creep deformation of the resin material are not required, and the reduction mechanism 51 can be miniaturized. In other words, while parked, the reaction force due to the braking force is not continuously applied to the reduction mechanism 51, and there is no need to consider creep deformation of the resin material, so the reduction mechanism 51 can be miniaturized. In this way, the parking brake mechanism 32A and the reduction mechanism 51 can be miniaturized, which improves vehicle mountability.

[0090] Next, the parking brake mechanism 32B according to the second embodiment will be described based on Figure 15, with reference to Figure 13 as appropriate. When describing the parking brake mechanism 32B according to the second embodiment, only the differences from the parking brake mechanism 32A according to the first embodiment will be described. The parking brake mechanism 32B according to the second embodiment includes an electric motor 300, a reduction mechanism 304, a screw mechanism 325 and a ball ramp mechanism 400 which are rotation-to-linear motion conversion mechanisms 306, and a lock wheel 308. The rotating shaft 302 of the electric motor 300 extends in a direction perpendicular to the rotating shaft 54 ​​of the electric motor 50. Specifically, in Figure 15, the rotating shaft 302 of the electric motor 300 extends toward the foreground of the paper. The reduction mechanism 304 is composed of a worm gear reducer 409 consisting of a worm gear 405 and a worm wheel section 406.

[0091] A worm gear 405 is press-fitted and fixed onto the rotating shaft 302 of the electric motor 300. The rotary-to-linear motion conversion mechanism 306 includes a screw mechanism 325 and a ball ramp mechanism 400. The screw mechanism 325 consists of a nut member 412 and a center shaft 414. A female threaded portion 342 is formed in the radial center of the nut member 412. The center shaft 414 consists of a disc-shaped head 333, a screw-type large-diameter shaft portion 334 integrally connected from the head 333 to the other end and having a male threaded portion 338 formed on its outer circumference, a small-diameter shaft portion 335 integrally connected from the screw-type large-diameter shaft portion 334 to the other end, and a minimum-diameter shaft portion 336 integrally connected from the small-diameter shaft portion 335 to the other end. A groove 416 extending in the axial direction is formed on the outer circumference of the small-diameter shaft portion 335 of the center shaft 414. Furthermore, a projection 340 is provided on the other end face of the head 333 of the center shaft 414, similar to the center shaft 328 in the first embodiment, projecting toward the other end.

[0092] The female thread portion 342 of the nut member 412 is screwed onto the male thread portion 338 of the threaded large-diameter shaft portion 334 of the center shaft 414. A projection 348 is provided on one end face of the nut member 412, similar to the lock nut 330 of the first embodiment, projecting toward the end. A worm wheel portion 406 is formed on the other end of the outer circumferential surface of the nut member 412. A worm gear 405, which is press-fitted and fixed onto the rotating shaft 302 of the electric motor 300, meshes with the worm wheel portion 406 of the nut member 412. The worm wheel portion 406 of the nut member 412 is formed as a helical gear. This allows the nut member 412 to mesh with the worm gear 405 even if it moves axially. Note that if the tooth profile has an arc-shaped recess, it cannot slide axially. The worm reducer 409 has an irreversible direction of rotational torque transmission. In other words, the worm gear reducer 409 can transmit rotation from the rotating shaft 302 of the electric motor 300 to the nut member 412, but it does not transmit rotation from the nut member 412 to the rotating shaft 302 of the electric motor 300. This worm gear reducer 409 corresponds to an irreversible rotation drive mechanism.

[0093] The ball ramp mechanism 400 comprises a nut member 412, which is also part of the screw mechanism 325, a locking member 419, and a plurality of balls 421 interposed between the nut member 412 and the locking member 419. The locking member 419 corresponds to a rotational linear motion member. The other end face of the nut member 412 is provided with a plurality of ball grooves 425 on which the balls 421 roll, extending in an arc shape with a predetermined inclination angle along the circumferential direction and having an arc-shaped cross section in the radial direction. In this embodiment, the ball grooves 425 of the nut member 412 are provided in three equally spaced locations in the circumferential direction. The locking member 419 is formed of an annular plate, and an insertion hole 420 is formed in the radial center through which the small-diameter shaft portion 335 of the center shaft 414 is inserted. By inserting the small-diameter shaft portion 335 of the center shaft 414 into the insertion hole 420 of the locking member 419, the locking member 419 is rotatably supported on the center shaft 414.

[0094] The locking member 419 has a plurality of ball grooves 426 on one end face, each having a predetermined inclination angle along the circumferential direction and extending in an arc shape, and having an arc-shaped cross-section in the radial direction, on which balls 421 roll. In this embodiment, the ball grooves 426 of the locking member 419 are provided in three equally spaced locations along the circumferential direction. The balls 421 are interposed between each ball groove 425 of the nut member 412 and each ball groove 426 of the locking member 419. When the locking member 419 and the nut member 412 rotate relative to each other, each ball 421 between each ball groove 425 of the nut member 412 and each ball groove 426 of the locking member 419 rolls, causing the relative axial distance between the locking member 419 and the nut member 412 to change due to the rotational difference between them.

[0095] In short, when the rotation of the nut member 412 is restricted and the lock member 419 rotates relative to the nut member 412 in a clockwise direction when viewed from one end, the lock member 419 moves forward toward the other end. A clutch surface 346 is formed on the outer circumferential surface of the other end of the lock member 419, which gradually decreases in diameter toward the other end. In the parking brake mechanism 32B according to the second embodiment, a ball ramp mechanism 400 is used, but other known technologies with good efficiency, such as a roller ramp mechanism using rollers as rolling elements, or a ball screw mechanism, may also be used. A lock wheel 308 is positioned on the other end side of the lock member 419.

[0096] The lock wheel 308 has an insertion hole 429 through which the smallest diameter shaft portion 336 of the center shaft 414 is inserted. The lock wheel 308 is rotatably supported by the center shaft 414 when the smallest diameter shaft portion 336 of the center shaft 414 is inserted through the insertion hole 429 of the lock wheel 308. The outer circumference of one end face of the lock wheel 308 has an annular plate portion 357, similar to the lock wheel 308 of the first embodiment. A clutch surface 358 is formed on the inner circumferential surface of the annular plate portion 357 at one end, with the opening diameter gradually increasing toward the end. The axial length (thickness) of the annular plate portion 357 of the lock wheel 308 is larger than the axial length (thickness) of the annular plate portion 357 of the lock wheel 308 according to the first embodiment.

[0097] The other end face of the lock wheel 308 is provided with a large-diameter recess 431 and a small-diameter recess 432 which is smaller in diameter than the large-diameter recess 431. The inner circumferential surface of the large-diameter recess 431 coincides with the inner circumferential surface of the annular plate portion 357. A pair of washers 435, 435 are placed on the other end face of the lock member 419 and on the bottom surface of the large-diameter recess 431 of the lock wheel 308, respectively. A spring 437 is placed between the pair of washers 435, 435. The biasing force of the spring 437 biases the lock member 419 toward the nut member 412 via one of the washers 435 (the washer on one end). As a result, it is possible to prevent each ball 421 of the ball ramp mechanism 400 from separating from each ball groove 425 of the nut member 412 and each ball groove 426 of the lock member 419. The locking member 419, the spring 437, and the pair of washers 435, 435 are axially slidable along the small diameter shaft portion 335 of the center shaft 414, and their radial movement is restricted.

[0098] Each of the pair of washers 435 has a projection 440 extending inward from its inner circumferential surface. Each projection 440 of the pair of washers 435 engages with a groove 416 provided in the small-diameter shaft portion 335 of the center shaft 414, thereby preventing the pair of washers 435 from rotating relative to the center shaft 414. In this embodiment, rotation is prevented between the pair of washers 435 and the center shaft 414 by this projection engagement; however, other known anti-rotation means, such as D-cut sections or spline engagement, may be employed. The other washer 435 (the washer at the other end) is restricted from moving at its other end by a retaining ring 442 that engages with the groove 416 in the small-diameter shaft portion 335 of the center shaft 414. A thrust plate 355 is positioned at the other end of the lock wheel 308.

[0099] The thrust plate 355 has a through hole 356 formed in its radial center through which the smallest diameter shaft portion 336 of the center shaft 414 is inserted. On the inner circumferential surface of the other end of the through hole 356 of the thrust plate 355, a tapered surface 447 is formed, the opening diameter of which gradually increases toward the other end. The smallest diameter shaft portion 336 of the center shaft 414 is inserted through the through hole 356 of the thrust plate 355, and a retaining ring (C-ring) 444 supported near the other end of the center shaft 414 comes into contact with the tapered surface 447 of the thrust plate 355. The relative axial movement of the lock wheel 308 is then restricted by the other washer 435 (the washer on the other end 435) and the thrust plate 355.

[0100] During assembly, the screw mechanism 325 and the ball ramp mechanism 400 are moved to one end, and the gap between the clutch surface 358 of the lock wheel 308 and the clutch surface 346 of the lock member 419 is made sufficiently large, and the lock wheel 308 is pushed to one end. Subsequently, the spring 437 is compressed via the other washer 435 (the washer on the other end 435), and the thrust plate 355 and retaining ring 444 are assembled. Then, when the lock wheel 308 is released, the reaction force of the spring 437 moves the lock wheel 308 and thrust plate 355 to the other end, and the retaining ring 444 comes into contact with the tapered surface 447 of the thrust plate 355, completing the assembly.

[0101] Next, the operation of the parking brake mechanism 32B according to the second embodiment will be explained. When the parking brake is activated, as described above, a braking force is generated in the vehicle, and when that braking force reaches a target value, the control board 230 activates the parking brake mechanism 32B based on this signal. That is, power is supplied to the electric motor 300, causing the nut member 412 to rotate clockwise when viewed from one end via the worm gear reducer 409. Subsequently, the nut member 412 moves forward toward the other end while rotating due to the action of the screw mechanism 325. At this time, because of the operating resistance due to the pre-pressure of the spring 437, the ball ramp mechanism 400 does not operate, and the lock member 419 also moves forward toward the other end while rotating integrally with the nut member 412 in the same direction.

[0102] Next, the clutch surface 346 of the locking member 419 contacts the clutch surface 358 of the lock wheel 308, generating a pressing force. Then, similar to the parking brake mechanism 32A according to the first embodiment, the current to the electric motor 50 is reduced while continuing to supply power to the electric motor 300, until finally the power supply to the electric motor 50 is stopped, and the power supply to the electric motor 300 is also stopped (times t3 to t4 in Figure 13). Subsequently, similar to the parking brake mechanism 32A according to the first embodiment, the thrust-applying mechanism 52 starts reverse operation in the direction of releasing the braking force, and transmits it to the lock wheel 308 via the gear plate 94 as a rotational torque in the clockwise direction when viewed from one end.

[0103] The rotational torque applied to the lock wheel 308 is transmitted to the lock member 419 as a rotational torque in a clockwise direction when viewed from one end, via the clutch surface 358 of the annular plate portion 357 of the lock wheel 308 and the clutch surface 346 of the lock member 419. As a result, the ball ramp mechanism 400 overcomes the operating resistance caused by the biasing force of the spring 437 and begins to operate, causing the lock member 419 to rotate and advance toward the other end, increasing the pressing force. In other words, in the screw mechanism 325, the worm reducer 409 is irreversible and does not operate, so the nut member 412 does not rotate and remains in its position, and the ball ramp mechanism 400 is activated.

[0104] Subsequently, similar to the parking brake mechanism 32A according to the first embodiment, the drive mechanism 31 and the parking brake mechanism 32B stop and are held in that position when the reverse rotational torque in the direction that releases the braking force from the gear plate 94 to the lock wheel 308 balances out with the torque reaction force due to the pressing force between the clutch surface 346 of the lock member 419 and the clutch surface 358 of the lock wheel 308, and the parking brake lock is completed.

[0105] Next, the operation of releasing the parking brake in the parking brake mechanism 32B according to the second embodiment will be explained. Note that the power supply control to the electric motor 50 and electric motor 300 during this release is the same as that of the parking brake mechanism 32A according to the first embodiment, and therefore the explanation will be omitted. When releasing, at the moment when the clutch surface 346 of the lock member 419 and the clutch surface 358 of the annular plate portion 357 of the lock wheel 308 are separated (time t8 in Figure 13), the ball ramp mechanism 400 is reversed by the biasing force from the spring 437, and the lock member 419 returns to its original position relative to the nut member 412. In this way, the parking brake is released.

[0106] According to the parking brake 32B of the second embodiment described above, the parking brake can be reactivated after being activated once without supplying power to the electric motor 300. That is, when power is supplied to the electric motor 50 in a direction that increases the braking force by the piston 40, the lock wheel 308 rotates counterclockwise when viewed from one end. Subsequently, due to the action of the ball ramp mechanism 400, the lock member 419 also rotates together in a counterclockwise direction and retracts toward one end. Subsequently, when the lock member 419 retracts, the pressing force applied to the clutch surface 346 of the lock member 419 and the clutch surface 358 of the annular plate portion 357 of the lock wheel 308 decreases to an amount equivalent to that generated by the electric motor 300 during activation. Because this pressing force is small, the frictional resistance torque between the clutch surface 346 of the lock member 419 and the clutch surface 358 of the annular plate portion 357 of the lock wheel 308 is small enough that the electric motor 50 can continue to rotate and the braking force by the piston 40 can be increased.

[0107] At this time, the nut member 412 does not rotate or move linearly due to the irreversible action of the worm gear reducer 409, as described above, and the pressing force applied to the screw mechanism 325 is maintained at a small level. Then, after the piston 40 reaches the target braking force, when the current to the electric motor 50 is reduced, the lock wheel 308 rotates clockwise when viewed from one end, due to the reverse action in the thrust application mechanism 52 in the direction of releasing the pressing force caused by the reaction force received from the piston 40, just as during operation, and the ball ramp mechanism 400 is activated again, that is, the lock member 419 rotates and moves to the other end, and the parking brake lock is completed. Furthermore, in the parking brake mechanism 32B according to the second embodiment, reliability is improved because even if the power supply is lost during restart, the braking force from the piston 40 is not released.

[0108] Next, the parking brake mechanism 32C according to the third embodiment will be described based on Figure 16, with reference to Figure 13 as appropriate. When describing the parking brake mechanism 32C according to the third embodiment, only the differences from the parking brake mechanism 32B according to the second embodiment will be described. In the parking brake mechanism 32C according to the third embodiment, a solenoid actuator 500 is employed in which a plunger 503 moves back and forth in one direction. The solenoid actuator 500 corresponds to the drive device. Note that a reduction mechanism 304 (worm gear reducer 409) is not employed. In addition, only a ball ramp mechanism 400 is employed for the rotary-to-linear motion conversion mechanism 306. The solenoid actuator 500 is electrically connected to the control board 230. The plunger 503 of the solenoid actuator 500 extends and retracts in a direction perpendicular to the rotation axis 54 of the electric motor 50. Specifically, in Figure 16, the plunger 503 of the solenoid actuator 500 extends and retracts toward the foreground of the paper.

[0109] In other words, when power is supplied, the solenoid actuator 500 moves so that the plunger 503 protrudes toward the front of the paper, and when power is stopped, it returns to its original position by a return spring (not shown). Note that the solenoid actuator 500 used here is not a bidirectional drive type, but energizes in only one direction, and the plunger 503 is driven only for the protruding action. The center shaft 505 comprises a disc-shaped head 333, a spline shaft portion 507 integrally connected from the head 333 to the other end, a small-diameter shaft portion 335 integrally connected from the spline shaft portion 507 to the other end, and a minimum-diameter shaft portion 336 integrally connected from the small-diameter shaft portion 335 to the other end.

[0110] The ball ramp mechanism 400 comprises a base member 510, a locking member 419, and a plurality of balls 421 interposed between the base member 510 and the locking member 419. The locking member 419 corresponds to a rotational linear motion member. The base member 510 is formed in the shape of an annular plate, with a spline hole 511 formed in its radial center. The spline shaft portion 507 of the center shaft 505 is inserted through the spline hole 511 of the base member 510, thereby restricting their relative rotation. The other end face of the base member 510 is provided with a plurality of ball grooves 425 on which the balls 421 roll, extending in an arc shape with a predetermined inclination angle along the circumferential direction and having an arc-shaped cross-section in the radial direction.

[0111] One end face of the base member 510 abuts against the head 333 of the center shaft 505, restricting the movement of the base member 510 toward one end. The locking member 419 is formed in the shape of an annular plate. The locking member 419 has a through hole 420 in its radial center through which the small-diameter shaft portion 335 of the center shaft 505 is inserted. By inserting the small-diameter shaft portion 335 of the center shaft 505 into the through hole 420 of the locking member 419, the locking member 419 is rotatably supported on the center shaft 505. One end face of the locking member 419 is provided with a plurality of ball grooves 426 on which balls 421 roll, each extending in an arc shape with a predetermined inclination angle along the circumferential direction and having an arc-shaped cross-section in the radial direction. The balls 421 are interposed between each ball groove 425 of the base member 510 and each ball groove 426 of the locking member 419.

[0112] When the locking member 419 and the base member 510 rotate relative to each other, the balls 421 between each ball groove 425 of the locking member 419 and each ball groove 426 of the base member 510 roll, causing the relative axial distance between the locking member 419 and the base member 510 to change due to the difference in rotation between them. Since the rotation of the base member 510 is restricted, when the locking member 419 rotates relative to the base member 510 in a clockwise direction when viewed from one end, the locking member 419 moves forward toward the other end. Arms 514 extend radially outward from the outer circumferential surface of the locking member 419. When the plunger 503 of the solenoid actuator 500 protrudes, the tip of the plunger 503 contacts the arm 514 of the locking member 419, causing the locking member 419 to rotate clockwise when viewed from one end.

[0113] Next, the operation of the parking brake mechanism 32C according to the third embodiment will be explained. When the parking brake mechanism 32C according to the third embodiment is activated, the plunger 503 protrudes due to the power supply to the solenoid actuator 500, causing the locking member 419 to rotate clockwise when viewed from one end. Then, the locking member 419 moves forward toward the other end due to the action of the ball ramp mechanism 400. Subsequently, the clutch surface 346 of the locking member 419 comes into contact with the clutch surface 358 of the lock wheel 308, generating a pressing force. Then, similar to the parking brake mechanisms 32A and 32B according to the first and second embodiments, the current to the electric motor 50 is reduced while continuing to supply power to the solenoid actuator 500, and finally the power supply to the electric motor 50 is stopped, as is the power supply to the solenoid actuator 500 (times t3 to t4 in Figure 13). As a result, the plunger 503 returns to its original position. The subsequent operations are the same as those of the parking brake mechanism 32B according to the second embodiment, so the explanation here is omitted.

[0114] On the other hand, when releasing the parking brake, power is not supplied to the solenoid actuator 500, and the plunger 503 remains stopped in its original position. Then, similar to the parking brake mechanisms 32A and 32B according to the first and second embodiments, power is supplied to the electric motor 50 in the direction that increases the braking force by the piston 40, causing the lock wheel 308 of the parking brake mechanism 32C to rotate counterclockwise when viewed from one end, and the lock member 419 to rotate in the same direction. Then, due to the reverse operation of the ball ramp mechanism 400, the lock member 419 retracts, creating a gap between the clutch surface 346 of the lock member 419 and the clutch surface 358 of the lock wheel 308. After that, power is supplied to the electric motor 50 in the direction that decreases the braking force (times t8 to t9 in Figure 13), and the release control is completed.

[0115] Then, when the clutch surface 346 of the locking member 419 and the clutch surface 358 of the locking wheel 308 separate, the biasing force from the spring 437 causes the ball ramp mechanism 400 to reverse, returning the locking member 419 to its original position. In this way, the parking brake is released.

[0116] Furthermore, according to the parking brake mechanism 32C of the third embodiment, the number of components can be reduced compared to the parking brake mechanisms 32A and 32B of the first and second embodiments, thereby reducing manufacturing and assembly costs. In addition, according to the parking brake mechanism 32C of the third embodiment, the drive circuit of the solenoid actuator 500 only needs to be able to turn the power supply ON / OFF, thus reducing the cost of the control board 230.

[0117] 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.

[0118] This application claims priority under Japanese Patent Application No. 2023-26429, filed on 22 February 2023. The entire disclosure of Japanese Patent Application No. 2023-26429, filed on 22 February 2023, including the specification, claims, drawings, and abstract, is incorporated into this application by reference. [Explanation of Symbols]

[0119] 1 Disc brake (electric braking device), 2 Inner brake pad (braking member), 3 Outer brake pad (braking member), 32A, 32B, 32C Parking brake mechanism, 51 Reduction mechanism, 52 Thrust application mechanism (electric braking mechanism), 308 Lock wheel (rotating body), 306 Rotation-to-linear motion conversion mechanism, 325 Screw mechanism, 330 Lock nut (rotation-to-linear motion member), 346 Clutch surface (clutch part), 358 Clutch surface, 400 Ball ramp mechanism, 409 Worm gear reducer (irreversible rotation drive mechanism), 419 Lock member (rotation-to-linear motion member), 500 Solenoid actuator, 503 Plunger, D Disc rotor (braked member)

Claims

1. An electric brake device, wherein the electric brake device is Electric motor and An electric brake mechanism that generates braking force by pressing a braking member against a member to be braked using the drive of the electric motor, The system includes a parking brake mechanism that maintains the braking force generated by the aforementioned electric brake mechanism, The aforementioned parking brake mechanism is A rotating body that rotates due to the rotational motion transmitted to the electric brake mechanism, A rotation-to-linear motion conversion mechanism including a rotation-to-linear motion member that can move in the axial direction of the rotating body while rotating, The rotary-to-linear motion conversion mechanism is driven by a drive device separate from the electric motor, The aforementioned rotary linear motion member has a clutch portion that contacts or separates from the rotating body, An electric brake device characterized in that the rotational-to-linear motion conversion mechanism is activated by the drive device, and when the clutch portion of the rotational-to-linear motion member is in contact with the rotating body, the rotational-to-linear motion member presses against the rotating body via the clutch portion as the rotating body rotates in a direction that releases the braking force transmitted from the electric brake mechanism, thereby suppressing the rotation of the rotating body.

2. In the electric brake device according to claim 1, The aforementioned rotary-to-linear motion conversion mechanism is characterized by being a screw mechanism.

3. In the electric brake device according to claim 1, The aforementioned rotary-to-linear motion conversion mechanism includes a screw mechanism and a ball ramp mechanism, The drive device is characterized by operating the rotation-to-linear motion conversion mechanism via an irreversible rotation drive mechanism.

4. In the electric brake device according to claim 1, The aforementioned rotation-to-linear motion conversion mechanism is a ball ramp mechanism, The drive device is a solenoid actuator in which a plunger moves back and forth in one direction, and the electric brake device is characterized in that the plunger acts on the rotary-to-linear motion conversion mechanism.

5. In the electric brake device according to any one of claims 1 to 4, An electric brake device characterized in that a reduction mechanism for increasing the rotational torque from the electric motor is provided between the electric motor and the rotating body in the rotation transmission path from the electric motor.

6. An electric brake device, wherein the electric brake device is Electric motor and An electric brake mechanism that generates braking force by pressing a braking member against a member to be braked using the drive of the electric motor, The system includes a parking brake mechanism that maintains the braking force generated by the electric brake mechanism, The aforementioned parking brake mechanism is A rotating body that rotates due to the rotational motion transmitted to the electric brake mechanism, A rotary linear motion member that is movable in the axial direction of the rotating body while rotating, and has a clutch portion that contacts the rotating body, The system includes a drive device separate from the electric motor for driving the rotating linear motion member, An electric brake device characterized in that the drive device moves the rotary linear member toward the rotating body, and when the clutch portion is in contact with the rotating body, the rotary linear member suppresses the rotation of the rotating body by a torque reaction force against the rotational torque in the release direction of the braking force transmitted from the electric brake mechanism applied to the rotating body.

Images