Electric brake device

Abstract

Provided is an electric brake device capable of suppressing increases in size and cost, and ameliorating the generation of operating noise. A brake mechanism adopted in a disc brake of the present invention comprises: an input gear to which rotation from an electric motor is input; a rotation-to-linear motion conversion mechanism that has a nut member which moves linearly in conjunction with the rotation of the input gear, and that presses inner and outer brake pads against a disc rotor via a piston by means of the nut member; a wave washer that biases the rotation-to-linear motion conversion mechanism together with the input gear toward a thrust detection sensor; and a radial ball bearing that is disposed between the input gear and the rotation-to-linear motion conversion mechanism. Thus, while suppressing increases in size and cost, generation of operating noise from the radial ball bearing can be suppressed and ameliorated.

Description

Electric brake device

[0001] The present invention relates to an electric brake device.

[0002] Patent Document 1 discloses an electric brake device including an electric motor, a caliper body equipped with the electric motor, a nut member that moves linearly along the axial direction of the disc when driven by the electric motor to move a friction pad, a center bolt that threads onto the nut member, whose relative rotation with respect to the caliper body is restricted, and extends along the axial direction of the disc, and a thrust detection sensor that is provided at one of both axial ends of the center bolt opposite the friction pad side and that detects a reaction force against a pressing force on the disc.

[0003] JP 2024-6640 A

[0004] In the electric brake device described in the aforementioned Patent Document 1, a radial bearing is disposed between the outer peripheral surface of the center bolt and the inner peripheral surface of the insertion hole in the gear plate, supporting the gear plate rotatably relative to the center bolt. However, the radial bearing has a gap inside. In addition, the gear plate is large in diameter and heavy due to the reduction in speed (increased torque). As a result, there is a risk of operating noise due to rattle of the radial bearing, which needs to be improved. Furthermore, if a new biasing means or the like is added to address this issue, it would increase the size and cost.

[0005] An object of the present invention is to provide an electric brake device that reduces the generation of operating noise while suppressing increases in size and cost.

[0006] As a means for solving the above-mentioned problems, the electric brake device of the present invention is an electric brake device comprising: an electric motor; a brake mechanism that presses a braking member against a member to be braked by rotation from the electric motor; and a thrust detection sensor that detects the pressing force of the braking member against the member to be braked by the brake mechanism, wherein the brake mechanism comprises: an input member to which rotation from the electric motor is input; a rotary-to-linear motion conversion mechanism having a linear-acting member that moves linearly in conjunction with the rotation of the input member, the linear-acting member pressing the braking member against the member to be braked via an output member; an elastic member that urges the rotary-to-linear motion conversion mechanism together with the input member toward the thrust detection sensor; a radial bearing arranged between the input member and the rotary-to-linear motion conversion mechanism; and a thrust bearing arranged between the rotary-to-linear motion conversion mechanism and the output member.

[0007] In the electric brake device according to one embodiment of the present invention, it is possible to reduce the generation of operating noise while suppressing an increase in size and cost.

[0008] 6 is a perspective view of a disc brake according to a first embodiment; FIG. 6 is a cross-sectional view of a disc brake according to a first embodiment; FIG. 6 is an enlarged view of a portion A in FIG. 2; FIG. 6 is an enlarged view of a portion B in FIG. 2; FIG. 6 is an enlarged view of a portion C in FIG. 2; FIG. 6 is a cross-sectional view of a disc brake according to a second embodiment; FIG. 6 is an enlarged view of a portion D in FIG. 6; FIG. 6 is an enlarged view of a portion E in FIG.

[0009] This embodiment will be described in detail below with reference to Figures 1 to 8. Disc brakes 1A and 1B according to first and second embodiments of the present invention are electric brake devices that generate braking force by driving an electric motor 65 during normal driving. In the following description, the inside of the vehicle (inner side) will be referred to as one end side (housing cover 74 side) and the outside of the vehicle (outer side) will be referred to as the other end side (disc rotor D side), as appropriate.

[0010] First, a disc brake 1A according to the first embodiment will be described in detail with reference to Figures 1 to 5. Referring to Figure 1, the disc brake 1A according to the first embodiment is provided with a pair of inner and outer brake pads 2 and 3, and a caliper 4, which are arranged on both axial sides of a disc rotor D attached to a rotating part of a vehicle. This disc brake 1A is configured as a floating caliper. The pair of inner and outer brake pads 2 and 3, and the caliper 4 are supported by a carrier 5 fixed to a non-rotating part of the vehicle, such as a knuckle, so as to be movable in the axial direction of the disc rotor D relative to the carrier 5.

[0011] 1 , the carrier 5 includes a pair of pin support portions 12A, 12B that support slide pins 10A, 10B, respectively, and inner and outer support portions 14, 15 that are integrally connected to the pair of pin support portions 12A, 12B and independently support the inner and outer brake pads 2, 3, respectively. The pair of pin support portions 12A, 12B are spaced apart along the rotational direction of the disc rotor D and extend along the axial direction of the disc rotor D. Each pin support portion 12A, 12B is formed in a substantially cylindrical shape. The slide pins 10A, 10B extend integrally from one end surface of each pin support portion 12A, 12 toward the one end. The inner support portion 14 is integrally connected to the inner side of the pin support portions 12A, 12B. An outer support portion 15 is integrally connected to the inner support portion 14 of each pin support portion 12A, 12B along the axial direction of the disc rotor D at a distance from the inner support portion 14 to the outer side.

[0012] The inner support portion 14 is composed of a pair of inner arm portions 20, 20 (only one of which is shown in FIG. 1 ) extending in directions substantially perpendicular to each other from the pin support portions 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 in the inner beam portion 21 at both ends in the rotational direction of the disc rotor D, respectively, and extend along the axial direction of the disc rotor D (only one of which is shown in FIG. 1 ). A female thread is formed on the inner peripheral surface of each through hole 22.

[0013] The carrier 5 is attached to a non-rotating portion of the vehicle via through holes 22, 22 provided in the inner support portion 14 (inner beam portion 21) using, for example, mounting bolts (not shown). The outer support portion 15 is composed of a pair of outer arms 23, 23 extending in directions substantially perpendicular to each other from the pin support portions 12A, 12B, and an outer beam portion 24 connecting the ends of the pair of outer arms 23, 23. The outer brake pad 3 is supported inside the pair of outer arms 23, 23 so as to be movable along the axial direction of the disc rotor D.

[0014] 1, the caliper 4 includes a caliper body 27, which is the main body of the caliper 4, and a drive mechanism 28. The caliper body 27 is integrally formed with a cylindrical cylinder portion 31 that is disposed on the base end side facing the inner brake pad 2 on the vehicle inside and opens facing the inner brake pad 2, a pair of claw portions 32, 32 that extend from the cylinder portion 31 to the outer side across the disc rotor D and are disposed on the tip side facing the outer brake pad 3 on the outer side, and a pair of caliper arms 33A, 33B that extend radially outward from the cylinder portion 31.

[0015] Referring to FIG. 1 , a cylindrical boss 47 with a bottom is integrally formed on the tip of one of the pair of caliper arms 33A, 33B, protruding toward the inner side. The boss 47 extends along the axial direction of the disc rotor D. One slide pin 10A is slidably inserted into the boss 47 along the axial direction. A through hole 48 is formed in the tip of the other of the pair of caliper arms 33A, 33B, penetrating the disc rotor D in the axial direction. The other slide pin 10B is formed by a hexagonal bolt with a hexagonal head. The hexagonal bolt, which is the slide pin 10B, is inserted into the through hole 48 of the other caliper arm 33B and is screwed into the inner end of the other pin support portion 12B. An axial gap is provided between the inner end surface around the through hole 48 of the other caliper arm 33B and the hexagonal head of the other slide pin 10B (hexagonal bolt), and a pin boot 49 having an expandable bellows portion is provided to cover this gap. The pair of slide pins 10A, 10B can support the caliper body 27 slidably along the axial direction of the disc rotor D (wheel) relative to the carrier 5.

[0016] Referring to FIG. 2 , one end of the cylinder portion 31 is hermetically housed within the cylinder housing portion 78 (recessed portion) of the motor gear housing 73 by a seal member 81. The portion of the cylinder portion 31 housed within the cylinder housing portion 78 of the motor gear housing 73 (the portion closer to the one end than the seal member 81) where a gear portion 93 of the input gear 83 (described later) meshes with the reduction mechanism 66 is open. A large-diameter cylinder bore 40 is formed at one end of the cylinder portion 31, and a small-diameter cylinder bore 41 is formed at the other end. Referring also to FIG. 5 , an annular bore step portion 43 is formed between the inner circumferential surfaces of the large-diameter cylinder bore 40 and the small-diameter cylinder bore 41. Referring to FIG. 2 , a first pin member 45 extends from the inner circumferential surface of one end of the large-diameter cylinder bore 40 toward the inside of the large-diameter cylinder bore 40. A piston 52 is supported within the large-diameter cylinder bore 40 of the cylinder portion 31 so as to be movable along the axial direction.

[0017] 2, the piston 52 presses against the inner brake pad 2 and is formed in the shape of a cylinder with a bottom. More specifically, the piston 52 is formed with a large-diameter recess 54, an intermediate-diameter recess 55, and a small-diameter recess 56, in this order, from one end to the other. The piston 52 is housed in the large-diameter cylinder bore 40 of the cylinder portion 31 so that its bottom faces the inner brake pad 2. Referring also to FIG. 3, the inner circumferential surface of the large-diameter recess 54 of the piston 52 is formed with a concave-convex groove 58, in which concave-convex portions along the circumferential direction extend along the axial direction. Meanwhile, the outer circumferential surface of the first washer 60 is also formed with a concave-convex groove 61, in which concave-convex portions along the circumferential direction extend along the axial direction.

[0018] 2 and 3, a first washer 60 is disposed near the other end of the large diameter recess 54 of the piston 52 so that a concave-convex groove 58 provided on the inner circumferential surface of the large diameter recess 54 of the piston 52 and a concave-convex groove 61 provided on the inner circumferential surface of the first washer 60 fit together. The first washer 60 is disposed so as to protrude inward from the inner circumferential surface of the large diameter recess 64 of the piston 52. A retaining ring 63 is disposed on one end face of the first washer 60. This restricts the relative rotation between the first washer 60 and the piston 52, and restricts movement of one end of the first washer 60 relative to the piston 52. The piston 52 corresponds to an output member.

[0019] 2, a seal member 35 is disposed on the inner peripheral surface of the other end of the large-diameter cylinder bore 40 of the cylinder portion 31. The piston 52 is housed in the large-diameter cylinder bore 40 and is movable axially while in contact with the seal member 35. A dust boot 36 is interposed between the outer peripheral surface of the bottom side of the piston 52 and the inner peripheral surface of the other end of the large-diameter cylinder bore 40. The seal member 35 and dust boot 36 prevent foreign matter from entering the large-diameter cylinder bore 40 and the small-diameter cylinder bore 41 of the cylinder portion 31.

[0020] 1 and 2 , the drive mechanism 28 includes an electric motor 65, a speed reduction mechanism 66 that reduces the speed of rotation from the electric motor 65 and increases the power thereof, and a brake mechanism 67 that converts the rotational motion from the speed reduction mechanism 66 into linear motion to apply thrust to the piston 52 and press the inner and outer brake pads 2, 3 against the disc rotor D. The disc brake 1A according to the first embodiment also includes a thrust detection sensor 70 that detects the pressing force of the inner and outer brake pads 2, 3 against the disc rotor D by the brake mechanism 67.

[0021] The electric motor 65 and reduction mechanism 66 of the drive mechanism 28, and a portion of one end of the cylinder portion 31 are housed in a motor gear housing 73. The motor gear housing 73 is connected to the cylinder portion 31 with bolts (not shown) or the like. An opening on one end of the motor gear housing 73 is airtightly closed by a housing cover 74. As a result, the interior of the motor gear housing 73 is airtightly closed. The motor gear housing 73 includes a motor housing portion 76, a gear housing portion 77, and a cylinder housing portion 78. The motor housing portion 76 and the gear housing portion 77 are arranged to overlap along the axial direction of the disc rotor D.

[0022] The gear housing portion 77 is disposed closer to one end than the motor housing portion 76. A cylinder housing portion 78 is formed so as to be aligned longitudinally with the gear housing portion 77. The cylinder housing portion 78 is configured by being deeply recessed from the other end. The main body of the electric motor 65 is housed in the motor housing portion 76. The rotating shaft (not shown) of the electric motor 65 is located on the one end side and extends into the gear housing portion 77. The reduction mechanism 66 is housed in the gear housing portion 77. As described above, referring to FIG. 2 , one end of the cylinder portion 31 is housed in the cylinder housing portion 78 via a seal member 81. This seal member 81 maintains airtightness within the cylinder portion 31 and the motor gear housing 73. The reduction mechanism 66 is configured, although a detailed description of the mechanism will be omitted, by using a multi-stage multi-shaft gear reduction mechanism, a planetary gear reduction mechanism, or the like.

[0023] 1 and 2 , the brake mechanism 67 is disposed between the large-diameter cylinder bore 40 and the small-diameter cylinder bore 41 of the cylinder portion 31 and the piston 52. The brake mechanism 67 includes: an input gear 83 to which rotation from the electric motor 65 is input via a reduction mechanism 66; a rotary-to-linear motion conversion mechanism 85A according to the first embodiment, which has a nut member 127 that moves linearly while rotating in response to the rotation from the input gear 83 and presses the inner and outer brake pads 2, 3 against the disc rotor D via the piston 52 using the nut member 127; a wave washer 86 that, together with the input gear 83, urges the rotary-to-linear motion conversion mechanism 85A according to the first embodiment (described in detail later) toward the thrust detection sensor 70; a thrust bearing 87 that is provided on the other end of the rotary-to-linear motion conversion mechanism 85A according to the first embodiment and supports the rotary-to-linear motion conversion mechanism 85A; and a radial ball bearing 88 that is disposed between the input gear 83 and the rotary-to-linear motion conversion mechanism 85A according to the first embodiment.

[0024] Referring to FIG. 2, the input gear 83 is disposed within the cylinder portion 31. The input gear 83 is formed in a stepped cylindrical shape. The input gear 83 includes a large-diameter gear portion 90 disposed at one end thereof and a small-diameter support portion 91 provided continuously from the large-diameter gear portion 90 to the other end thereof. A gear portion 93 is formed on the outer peripheral surface of the large-diameter gear portion 90 at one end thereof. The gear portion 93 of the large-diameter gear portion 90 meshes with the reduction mechanism 66 (see FIG. 1). As a result, rotation from the reduction mechanism 66 is transmitted to the input gear 83. The input gear 83 corresponds to an input member. Referring to FIG. 5, an annular step portion 95 is formed between the outer peripheral surface of the large-diameter gear portion 90 and the outer peripheral surface of the small-diameter support portion 91.

[0025] 2 and 4 , a radial ball bearing 88 is disposed between the inner peripheral surface of one end of the input gear 83, i.e., the inner peripheral surface in the range where the large-diameter gear portion 90 is formed, and the outer peripheral surface of the other end of a large-diameter disc portion 132 of a center bolt 126, which will be described later. As a result, the input gear 83 is supported so as to be rotatable relative to the center bolt 126. An engaging portion 97 is formed on the inner peripheral surface of the input gear 83 over the entire other end thereof, excluding the range where the radial ball bearing 88 abuts, and is axially slidable with a nut member 127, which will be described later, and which restricts relative rotation. An annular step portion 99 is formed between the inner peripheral surface of one end of the input gear 83 and the engaging portion 97. The radial ball bearing 88 is disposed so as to abut against this step portion 99.

[0026] 2 and 5 , a second washer 102 is disposed so as to abut against a step 95 between the large-diameter gear portion 90 and the small-diameter support portion 91 of the input gear 83. The inner peripheral surface of the second washer 102 abuts against the outer peripheral surface of the small-diameter support portion 91 of the input gear 83. The second washer 102 is guided in the radial direction by the input gear 83. The step 95 restricts relative movement of the second washer 102 toward one end with respect to the input gear 83. An angular contact ball bearing 104 is disposed between the inner peripheral surface at the other end of the large-diameter cylinder bore 40 of the cylinder portion 35 and the outer peripheral surface of the small-diameter support portion 91 of the input gear 83. The input gear 83 is rotatably supported by the angular contact ball bearing 104. The raceway ring on one end of the angular contact ball bearing 104 does not abut against the inner peripheral surface of the large diameter cylinder bore 40 , and its radial movement is restricted by the small diameter support portion 91 of the input gear 83 .

[0027] 2 and 5, the other end raceway of the angular ball bearing 104 abuts against the inner circumferential surface of the large-diameter cylinder bore 40 of the cylinder portion 31 and also abuts against the bore step 43 between the large-diameter cylinder bore 40 and the small-diameter cylinder bore 41. A wave washer 86 is disposed between the one end raceway of the angular ball bearing 104 and the second washer 102. The wave washer 86 corresponds to an elastic member. Note that although the angular ball bearing 104 is used in this embodiment, a thrust ball bearing, a thrust ball roller bearing, or a washer serving as a plain bearing with a contact angle of 90 degrees may also be used. Furthermore, the input gear 83 is rotatably supported by the center bolt 126 (described later) via a radial ball bearing 88, and is rotatably supported by the cylinder portion 31 via the angular ball bearing 104, thereby enabling stable rotation of the input gear 83. Although the wave washer 86 is used in this embodiment, other known biasing means such as a disc spring or a coil spring may also be used. The initial position of the piston 52 when not braking is the position shown in FIG. 2, where one end face of the piston 52 abuts against the angular contact ball bearing 104.

[0028] Referring to FIG. 2 , an end plate 106 is disposed at one end of the large-diameter cylinder bore 40 of the cylinder portion 31. The end plate 106 corresponds to a support member. The end plate 106 is formed in an annular shape. The end plate 106 has a main through hole 109 located at one end and a tapered through hole 110 that gradually increases in diameter from the main through hole 109 toward the other end. The thrust detection sensor 70 is supported by the end plate 106. A press-fit recess 111 having a circular outer shape is recessed in the other end surface of the end plate 106 around the tapered through hole 110. Referring to FIGS. 2 and 4 , an annular fitting groove 112 is formed on the other end surface of the end plate 106 outside the press-fit recess 111. An annular protrusion 113 is formed on the other end surface of the end plate 106, continuing from the outside of the annular fitting groove 112 and protruding toward the other end. The annular engagement groove 112 and the annular protrusion 113 are provided continuously via their respective engagement surfaces 115. A second pin member 118 extends from a predetermined position along the circumferential direction within the annular engagement groove 112 toward the other end.

[0029] 2, a large chamfered portion 120 is formed on the outer peripheral edge of one end of the end plate 106. A retaining ring 122, which is a C-ring, provided on the inner peripheral surface of one end of the large-diameter cylinder bore 40 abuts against the chamfered portion 120 of the end plate 106. As a result, movement of the end plate 106 toward the one end with respect to the cylinder portion 31 is restricted. An anti-rotation groove 124 is formed on the outer peripheral surface of the end plate 106. A first pin member 45 protruding from the inner peripheral surface of the large-diameter cylinder bore 40 of the cylinder portion 31 engages in the anti-rotation groove 124 of the end plate 106. As a result, the end plate 106 is supported so as not to rotate relative to the cylinder portion 31.

[0030] 2 , the rotary-to-linear motion conversion mechanism 85A according to the first embodiment is configured with a ball screw mechanism 129 including a center bolt 126, a nut member 127, and a plurality of balls 128 interposed between the center bolt 126 and the nut member 127. The center bolt 126 corresponds to the fixed member, and the nut member 127 corresponds to the rotary-to-linear motion member. The center bolt 126 is concentrically disposed inside the large-diameter cylinder bore 40 and the small-diameter cylinder bore 41 of the cylinder portion 31. The center bolt 126 includes a large-diameter disc portion 132 disposed at one end thereof and a small-diameter threaded shaft portion 133 extending continuously from the large-diameter disc portion 132 toward the other end thereof. The large-diameter disc portion 132 is disposed within the large-diameter cylinder bore 40.

[0031] 2, a reaction force transmitting recess 135 is recessed into one end surface of the large-diameter disk portion 132. A reaction force transmitting surface 136 is formed on the bottom surface of the reaction force transmitting recess 135, which abuts against a detection surface 172 of the thrust detection sensor 70, which will be described later. The reaction force transmitting surface 136 of the reaction force transmitting recess 135 and the detection surface 172 of the thrust detection sensor 70 abut against each other's spherical surfaces. In this embodiment, the detection surface 172 of the thrust detection sensor 70 is formed as a convex spherical surface that protrudes toward the other end, while the reaction force transmitting surface 136 is formed as a concave spherical surface that is recessed toward the other end. The curvature of the concave spherical surface on the reaction force transmitting surface 136 side is set to be approximately the same as or larger than the curvature of the convex spherical surface on the detection surface 172 side of the thrust detection sensor 70. This makes it possible to absorb assembly play due to the tolerances of the components and tilt of the center bolt 126 relative to the thrust detection sensor 70 caused by, for example, elastic deformation of the pair of claws 32, 32 when thrust is generated, thereby improving the thrust detection accuracy. At least one of the reaction force transmission surface 136 of the reaction force transmission recess 135 and the detection surface 172 of the thrust detection sensor 70 may be formed as a spherical surface, and the other may be formed as a flat surface.

[0032] An annular support protrusion 138 is formed around the reaction force transmission recess 135. The outer peripheral surface of the large-diameter disk portion 132 and the outer peripheral surface of the support protrusion 138 are located on the same plane. The outer peripheral surface of the support protrusion 138 (large-diameter disk portion 132) corresponds to the engagement surface with the end plate 106. An anti-rotation groove 140 is formed at a predetermined position in the circumferential direction on one end face of the support protrusion 138. Referring to FIG. 4 , the outer peripheral surface of the support protrusion 138 (large-diameter disk portion 132) of the center bolt 126 abuts against the engagement surface 115 between the annular engagement groove 112 and the annular protrusion 113 of the end plate 106, so that the large-diameter disk portion 132 of the center bolt 126 is fitted into the annular engagement groove 112 of the end plate 106. The outer peripheral surface of the support protrusion 138 of the center bolt 126 corresponds to the engagement surface with the end plate 106. 2, a second pin member 118 protruding from within the annular engagement groove 112 of the end plate 106 engages with an anti-rotation groove 140 provided in the support protrusion 138 of the center bolt 126. As a result, radial and axial movement and relative rotation of the center bolt 126 with respect to the end plate 106 are restricted.

[0033] 2 and 4 , the radial ball bearing 88 is disposed between the outer peripheral surface at the other end of the large-diameter disc portion 132 of the center bolt 126 and the inner peripheral surface at one end of the input gear 83 (the inner peripheral surface within the range where the large-diameter gear portion 90 is formed). That is, the outer peripheral surface of the large-diameter disc portion 132 of the center bolt 126 (which is flush with the outer peripheral surface of the support protrusion 138) serves as a support surface for the radial ball bearing 88. A retaining ring 142 is provided on the outer peripheral surface of the large-diameter disc portion 132 of the center bolt 126, on one end side of the radial ball bearing 88. As a result, the radial ball bearing 88 is disposed so as to be sandwiched in the axial direction between the stepped portion 99 provided on the inner peripheral surface of the input gear 83 and the retaining ring 142 provided on the outer peripheral surface of the large-diameter disc portion 132 of the center bolt 126, and axial movement of the radial ball bearing 88 relative to the input gear 83 and the center bolt 126 is restricted.

[0034] The radial ball bearing 88 is a deep groove ball bearing, and can support the radial pressing force from the input gear 83 and the axial pressing force from the wave washer 86 at one location. In this embodiment, a deep groove ball bearing is used for the radial ball bearing 88, but other known ball bearings such as angular bearings and four-point contact ball bearings may also be used. Referring to Figure 2, the small diameter threaded shaft portion 133 of the center bolt 126 is disposed in a range from the large diameter cylinder bore 40 of the cylinder portion 31 to the bottom of the small diameter recess 56 of the piston 52. A thread groove 145 is formed over substantially the entire axial area of ​​the small diameter threaded shaft portion 133.

[0035] A nut member 127 is disposed around the small-diameter threaded shaft portion 133 of the center bolt 126. A thread groove 146 is formed on the inner peripheral surface of the nut member 127. An engagement portion 148 is formed on the outer peripheral surface at one end of the nut member 127, which is axially slidable with respect to the input gear 83 and restricts relative rotation. The nut member 127 and the input gear 83 are engaged with each other via the respective engagement portions 97, 148 so as to be axially slidable relative to each other but not rotatable relative to each other. In this embodiment, the mutual engagement portions 97, 148 of the input gear 83 and the nut member 127 are configured by spline engagement. Other known techniques, such as serrations or hexalobular grooves, may also be used for the mutual engagement portions 97, 148 of the input gear 83 and the nut member 127.

[0036] A plurality of balls 128 are rollably disposed between a thread groove 146 provided on the inner peripheral surface of the nut member 127 and a thread groove 145 provided on the outer peripheral surface of the small-diameter screw shaft 133 of the center bolt 126. As a result, when rotation from the input gear 83 is transmitted to the nut member 127 via the respective engaging portions 97, 148, the action of the ball screw mechanism 129 allows the nut member 127 to move axially while rotating relative to the center bolt 126. Note that a circulation path (not shown) through which the balls 128 circulate is provided on the outer peripheral surface of the nut member 127 from the engaging portion 148 to the other end side, and a cylindrical cover member 150 is disposed to cover the circulation path.

[0037] 2 and 3, a groove 153 is formed on the outer peripheral surface at the other end of the nut member 127, with circumferentially extending concave and convex portions extending in the axial direction. Meanwhile, a groove 157 is formed on the inner peripheral surface of a third washer 155, with circumferentially extending concave and convex portions extending in the axial direction. The third washer 155 is disposed on the other end of the nut member 127 so that the groove 153 on the outer peripheral surface at the other end of the nut member 127 and the groove 157 on the inner peripheral surface of the third washer 155 fit together. The third washer 155 is disposed so as to protrude outward from the outer peripheral surface at the other end of the nut member 127. The relative rotation between the third washer 155 and the nut member 127 is restricted. A retaining ring 159 is disposed on the other end surface of the third washer 155. As a result, movement of the other end of the third washer 155 relative to the nut member 127 is restricted.

[0038] A first washer 60 protruding from the inner circumferential surface of the small diameter recessed portion 56 of the piston 52 is disposed on one end side, and a third washer 155 protruding from the outer circumferential surface of the nut member 127 is disposed on the other end side, with the first and third washers 60, 155 arranged to overlap along the axial direction. As a result, particularly when the electric motor 65 is rotated in the release direction and the nut member 127 retracts toward the one end while rotating, the first and third washers 60, 155 cause the piston 52 to retract so as to follow the retracting nut member 127. Referring to Figure 2, a first washer 162, a thrust bearing 87, and a second washer 163 are disposed in this order from one end side to the other end side around the small diameter threaded shank 133 of the center bolt 126 between the other end face of the nut member 127 and the bottom surface of the intermediate diameter recessed portion 55 of the piston 52.

[0039] The first bearing washer 162 is formed in an annular shape. The outer peripheral surface of the first bearing washer 162 abuts against the inner peripheral surface of one end of the intermediate diameter recessed portion 55 of the piston 52. The radial movement of the first bearing washer 162 is restricted by the piston 52. The first bearing washer 162 is rotatably supported within the intermediate diameter recessed portion 55 of the piston 52. An abutment surface 165, which is the other end surface of the nut member 127, and an abutment surface 166, which is one end surface of the first bearing washer 162, abut against each other at their spherical surfaces. In this embodiment, the abutment surface 165, which is the other end surface of the nut member 127, is formed as a convex spherical surface that protrudes toward the other end, while the abutment surface 166, which is one end surface of the first bearing washer 162, is formed as a concave spherical surface that is recessed toward the other end. The curvature of the concave spherical surface that is the abutment surface 166 of the first washer 162 is set to be approximately the same as or larger than the curvature of the convex spherical surface that is the abutment surface 165 of the nut member 127 .

[0040] This absorbs assembly play due to the tolerances of the components and tilt of the piston 52 relative to the nut member 127 when thrust is generated, improving the efficiency of thrust transmission from the nut member 127. At least one of the abutment surface 166, which is one end surface of the first washer 162, and the abutment surface 165, which is the other end surface of the nut member 127, may be formed into a spherical surface. The second washer 163 is formed in an annular shape. The outer peripheral surface of the second washer 163 abuts against the inner peripheral surface at the other end of the intermediate diameter recessed portion 55 of the piston 52. The second washer 163 is supported in the intermediate diameter recessed portion 55 of the piston 52. A thrust bearing 87 is arranged between the first washer 162 and the second washer 163.

[0041] 2, the thrust detection sensor 70 detects the pressing force of the inner and outer brake pads 2, 3 against the disc rotor D by the brake mechanism 67. In other words, the thrust detection sensor 70 detects the reaction force against the thrust (pressing force) from the piston 52 to the inner and outer brake pads 2, 3 by the brake mechanism 67. The thrust detection sensor 70 is formed in a solid shape that detects the pressing force on the central axis. Therefore, compared to known hollow thrust detection sensors, the thrust detection sensor 70 is less susceptible to the influence of unbalanced loads caused by deformation of the claws 32, etc., and can achieve good detection accuracy. The thrust detection sensor 70 is press-fitted and fixed to an end plate 106 located on one end side of the rotary-to-linear motion conversion mechanism 85A according to the first embodiment. The thrust detection sensor 70 comprises a cylindrical portion 168, a truncated cone portion 170 that continues from the cylindrical portion 168 toward the other end and gradually becomes larger in diameter toward the other end, and a large-diameter disk portion 171 that continues from the truncated cone portion 170 toward the other end.

[0042] A plurality of terminals 173 extend from one end surface of the columnar portion 168. These terminals 173 pass through insertion holes 177 formed in a wall 176 that defines the cylinder housing portion 78 and are connected to a control board disposed in the space between the wall 176 and the housing cover 74. Note that a reaction force against the thrust (pressing force) from the piston 52 to the inner and outer brake pads 2 and 3 causes the end plate 106 to bend, changing the axial distance between the end plate 106 and the control board. Therefore, the terminals 173 extending from the thrust detection sensor 705 may be provided with a deformable portion, or a deformable lead wire or an electrically conductive coil spring may be connected to the terminals 173 to absorb this change in distance. This reduces stress generated at the connection between the tips of the terminals 173 and the control board, preventing breakage.

[0043] 2 , a detection surface 172 is provided on the other end surface of the large-diameter disk-shaped portion 171 of the thrust detection sensor 70, protruding toward the other end. The detection surface 172 is formed as a convex spherical surface protruding toward the other end. The thrust detection sensor 70 has its columnar portion 168 and truncated conical portion 170 inserted into the main through-hole 109 and tapered through-hole 110 of the end plate 106, respectively, and the large-diameter disk-shaped portion 171 is press-fitted and fixed in the press-fit recess 111 of the end plate 106. At this time, the detection surface 172 of the thrust detection sensor 70 abuts against the reaction force transmission surface 136 of the reaction force transmission recess 135 of the center bolt 126 of the rotary-to-linear motion conversion mechanism 85A according to the first embodiment.

[0044] The electric motor 65 is electrically connected to a control board (not shown), and its drive is controlled by commands from the control board. The control board is disposed so as to straddle the gear housing portion 77 and the space extending from the wall portion 176 to the housing cover 74. A harness (not shown) used for supplying power from the vehicle and for communicating braking commands and the like is airtightly connected to the control board. For communicating braking commands and the like, the control board is electrically connected to detection sensors (not shown) that detect driver requests, such as a stroke sensor that detects the stroke of the brake pedal (not shown), and various other detection sensors (not shown) that detect various situations in which braking is required without a driver request.

[0045] The control board is also fitted with a magnetic detection IC chip (not shown) of a rotation angle detection means (not shown). The control board is electrically connected to the thrust detection sensor 70 via the terminals 173, 173. During braking during normal driving, the control board controls the driving of the electric motor 65 based on detection signals from detection sensors that respond to driver requests and various detection sensors that detect various situations where braking is required, detection signals from the magnetic detection IC chip of the rotation angle detection means, and detection signals from the thrust detection sensor 70.

[0046] Next, the operation of the disc brake 1A according to the first embodiment will be described. During braking during normal driving, detection signals from detection sensors that respond to driver requests and detection sensors that detect various situations in which braking is necessary are input to the control board. The control board also receives detection signals from a rotation angle detection means that detects the rotation angle of the rotary shaft of the electric motor 65, and a thrust detection sensor 70 that detects the thrust (reaction force against the pressing force) from the inner and outer brake pads 2, 3 to the disc rotor D.

[0047] The control board operates the drive mechanism 28 based on these detection signals. That is, the electric motor 65 is driven to rotate based on a command from the control board. The rotation in the apply direction from the electric motor 65 is transmitted to the input gear 83 of the brake mechanism 67 via the speed reduction mechanism 66. In this way, the rotation from the electric motor 65 is reduced and increased at a predetermined reduction ratio by passing through the speed reduction mechanism 66, and then transmitted to the input gear 83 of the brake mechanism 67.

[0048] Next, as the input gear 83 of the brake mechanism 67 rotates, the nut member 127 of the rotary-to-linear motion conversion mechanism 85A according to the first embodiment rotates. The rotation of the nut member 127 is transmitted to the center bolt 126 via a ball screw mechanism 129 between the nut member 127 and the center bolt 126. Since the center bolt 126 is supported so as not to rotate relative to the cylinder portion 31 (caliper body 27), the nut member 127 moves toward the other end while rotating from the initial position shown in FIG. 2. As the nut member 127 moves toward the other end, the piston 52 advances (moves toward the other end) together with the first bearing washer 162, thrust bearing 87, and second bearing washer 163.

[0049] In this way, the piston 52 moves forward (toward the other end) from the initial non-braking position shown in FIG. 2 while elastically deforming the seal member 35, pressing the inner brake pad 2 against the disc rotor D. At substantially the same time, the caliper 4 moves toward one end relative to the carrier 5 due to a reaction force against the pressing force of the piston 52 against the inner brake pad 2, and the outer brake pad 3 abutting against the claws 32, 32 is pressed against the disc rotor D. As a result, the disc rotor D is sandwiched between the pair of inner and outer brake pads 2, 3, generating a frictional force and ultimately a braking force for the vehicle. Thereafter, when the thrust detection sensor 70 detects that a predetermined braking force has been reached, the control board issues a command to stop power supply to the electric motor 65.

[0050] Therefore, during braking, a reaction force against the pressing force from the pair of inner and outer brake pads 2, 3 by the piston 52 onto the disc rotor D is applied to the thrust detection sensor 70 in the following order: piston 52 → second washer 163 → thrust bearing 87 → first washer 162 → nut member 127 → ball screw mechanism 129 → center bolt 126 → thrust detection sensor 70. In addition, the biasing force of the wave washer 86 is applied to the thrust detection sensor 70 in the following order: second washer 102 → input gear 83 → stepped portion 99 of the input gear 83 → radial ball bearing 88 → retaining ring 142 → center bolt 126 → thrust detection sensor 70. In short, during braking, the biasing force of the wave washer 86 is applied to the thrust detection sensor 70 in addition to the reaction force against the pressing force from the pair of inner and outer brake pads 2, 3 by the piston 52 onto the disc rotor D.

[0051] In other words, even in a no-load state where no braking force is being applied by the brake mechanism 67, the biasing force of the wave washer 86 is applied to the thrust detection sensor 70 in the following order: second washer 102 → input gear 83 → step portion 99 of the input gear 83 → radial ball bearing 88 → retaining ring 142 → center bolt 126. The biasing force that reaches the thrust detection sensor 70 is applied in the following order: thrust detection sensor 70 → end plate 106 → retaining ring 122 → cylinder portion 31 (caliper body 27) → angular contact ball bearing 104.

[0052] On the other hand, when releasing the brake, the electric motor 65 of the drive mechanism 28 is driven to rotate in the release direction based on a command from the control board. Then, the rotation in the release direction from the electric motor 65 is transmitted to the input gear 83 of the brake mechanism 67 via the speed reducer 66. Next, as the input gear 83 of the brake mechanism 67 rotates in the release direction, the nut member 127 moves backward while rotating in the release direction due to the action of the ball screw mechanism 129. As the nut member 127 moves backward, the first and third washers 60, 155 move the piston 52 together with the nut member 127 back to the initial position where one end face of the piston 52 abuts against the angular contact ball bearing 104. As a result, the braking force applied to the disc rotor D by the pair of inner and outer brake pads 2, 3 is released.

[0053] When the electric motor 65 retracts the piston 52 via the nut member 127 beyond the initial position, the angular ball bearing 104 is also moved toward one end together with the piston 52 and separated from the bore step portion 43 of the cylinder portion 31, compressing the wave washer 86. The biasing force of the wave washer 86 is then dispersed in two directions: toward the other end of the center bolt 126 in the order of the angular ball bearing 104, piston 52, retaining ring 63, first washer 60, third washer 155, retaining ring 159, nut member 127, and ball screw mechanism 129; and toward the one end of the center bolt 126 in the order of the second washer 102, input gear 83, radial ball bearing 88, and retaining ring 142. Therefore, when the piston 52 retracts beyond the initial position, the biasing force on the thrust detection sensor 70 decreases.

[0054] As a result, the control board can detect that the piston 52 has reached its initial position based on a change in the output value of the thrust detection sensor 70, and can stop the supply of electricity to the electric motor 65. Because it is possible to detect that the piston 52 has retracted to its initial position based on the output value of the thrust detection sensor 70, there is no need to provide an end stopper (a concave-convex portion that abuts along the circumferential direction) or the like to prevent excessive relative rotation of the nut member 127 with respect to the center bolt 126 in the release direction.

[0055] As described above, in the disc brake 1A according to the first embodiment, the brake mechanism 67 is particularly equipped with a wave washer 86 that, together with the input gear 83, urges the center bolt 126 of the rotary-to-linear motion conversion mechanism 85A according to the first embodiment toward the thrust detection sensor 70, and a radial ball bearing 88 that is arranged between the input gear 83 and the center bolt 126 of the rotary-to-linear motion conversion mechanism 85A according to the first embodiment.

[0056] That is, conventionally, an elastic member has been provided to keep the surface transmitting the reaction force against the braking force and the detection surface 172 of the thrust detection sensor 70 in constant contact with each other to prevent vibrations caused by vehicle travel from causing the surface transmitting the reaction force to separate and the detection surface 172 of the thrust detection sensor 70 from striking the detection surface 172 of the thrust detection sensor 70. That is, in the device described in Patent Document 1, the biasing force of a spring (elastic member) biases the gear plate toward one end of the cylinder portion, thereby suppressing separation between the first thrust bearing, the large diameter shaft portion of the center bolt, and the thrust detection sensor.

[0057] In this embodiment, the radial ball bearing 88 for rotatably supporting the input gear 83 relative to the center bolt 126 is arranged along the biasing force transmission path (pressurizing path) of the wave washer 86 serving as an elastic member, i.e., wave washer 86 → second washer 102 → input gear 83 → stepped portion 99 of the input gear 83 → radial ball bearing 88 → retaining ring 142 → center bolt 126 → thrust detection sensor 70. This allows internal rattle of the radial ball bearing 88 to be constantly suppressed by the biasing force of the wave washer 86 without the need for a new biasing means or the like. As a result, it is possible to suppress and improve the generation of operating noise from the radial ball bearing 88 while preventing the disc brake 1A from becoming larger and further preventing an increase in cost.

[0058] Furthermore, in the disc brake 1A according to the first embodiment, the thrust bearing 87 and ball screw mechanism 129, which are provided at the other end of the rotary-linear motion conversion mechanism 85A according to the first embodiment and are located between the first washer 162 and the second washer 163, are not constantly subjected to a spring force from the wave washer 86, thereby improving durability, suppressing a decrease in lifespan, and improving reliability.

[0059] Furthermore, in the disc brake 1A according to the first embodiment, the radial ball bearing 88 is a ball bearing, more specifically a deep groove ball bearing, which is effective in supporting the radial pressure from the input gear 83 and the axial pressure from the wave washer 86 at one location.

[0060] Furthermore, in the disc brake 1A according to the first embodiment, the rotary-to-linear motion conversion mechanism 85A according to the first embodiment is configured as a ball screw mechanism 129 having a center bolt 126, a nut member 127, and a plurality of balls 128 interposed between the center bolt 126 and the nut member 127, thereby simplifying the structure and facilitating assembly, thereby improving the ease of assembly.

[0061] Furthermore, in the disc brake 1A according to the first embodiment, the center bolt 126 has the outer peripheral surface of the support protrusion 138 as the engagement surface with the end plate 106, and the outer peripheral surface of the support protrusion 138 and the support surface of the radial ball bearing 88, which is the outer peripheral surface of the large diameter disc portion 132, are flush with each other, so that the cost of processing parts can be reduced and processing accuracy can be improved.

[0062] Furthermore, in the disc brake 1A according to the first embodiment, the abutment surface 165, which is the other end face of the nut member 127, and the abutment surface 166, which is one end face of the first washer 162, may abut against each other via their spherical surfaces, or at least one of the abutment surface 165 of the nut member 127 and the abutment surface 166 of the first washer 162 may be formed as a spherical surface and abut against each other. This makes it possible to absorb assembly play due to tolerances of the components and tilt of the piston 52 relative to the nut member 127 when thrust is generated, thereby improving the efficiency of thrust transmission from the nut member 127 to the piston 52.

[0063] Next, a disc brake 1B according to a second embodiment will be described with reference to FIGS. 6 to 8. When describing the disc brake 1B according to the second embodiment, only the differences from the disc brake 1A according to the first embodiment will be described. With reference to FIGS. 6 and 7, the disc brake 1B according to the second embodiment employs a rotary-to-linear motion conversion mechanism 85B according to the second embodiment. The rotary-to-linear motion conversion mechanism 85B according to the second embodiment includes a ball ramp mechanism 203 having a fixed ramp 200, a rotary-to-linear motion ramp 201, and a plurality of balls 202 interposed between the fixed ramp 200 and the rotary-to-linear motion ramp 201. The rotary-to-linear motion conversion mechanism 85B also includes a screw mechanism 208 formed by threaded engagement between a nut member 206 and an adjuster member 207. The fixed ramp 200 corresponds to the fixed member, and the rotary-to-linear motion ramp 201 and the nut member 206 correspond to the rotary-to-linear motion members.

[0064] The fixed ramp 200 is formed in the shape of an annular plate. The fixed ramp 200 has a large-diameter insertion hole 210 at one end, a small-diameter insertion hole 211 extending from the large-diameter insertion hole 210 to the other end, and an annular step portion 212 between the large-diameter insertion hole 210 and the small-diameter insertion hole 211. The fixed ramp 200 also has a small-diameter support portion 215 at one end, and a large-diameter ramp portion 216 extending from the small-diameter support portion 215 to the other end. One end surface of the small-diameter support portion 215 is recessed to form a sensor accommodating recess 218 that accommodates the large-diameter disk portion 171 of the thrust detection sensor 70. An annular support protrusion 220 is formed around the sensor accommodating recess 218. The outer peripheral surfaces of the small-diameter support portion 215 and the support protrusion 220 of the fixed ramp 200 are flush with each other. The outer peripheral surface of the support protrusion 220 (small diameter support portion 215 ) corresponds to the engagement surface with the end plate 106 .

[0065] An anti-rotation groove 222 is formed at a predetermined position in the circumferential direction on one end surface of the support protrusion 220. The outer peripheral surface of the support protrusion 220 (small diameter support portion 215) of the fixed ramp 200 abuts against the fitting surface 115, which is the inner peripheral surface of the annular mating groove 112 of the end plate 106, and the support protrusion 220 of the fixed ramp 200 is fitted into the annular mating groove 112 of the end plate 106. The outer peripheral surface of the support protrusion 220 of the fixed ramp 200 corresponds to the engagement surface with the end plate 106. Furthermore, a second pin member 118 protruding from within the annular mating groove 112 of the end plate 106 engages with the anti-rotation groove 222 formed on the support protrusion 220 of the fixed ramp 200. As a result, radial and axial movement and relative rotation of the fixed ramp 200 with respect to the end plate 106 are restricted.

[0066] 6 and 8 , the input gear 83 of the brake mechanism 67 employed in the disc brake 1B according to the second embodiment includes a large-diameter support hole 240 provided at one end, a small-diameter support hole 241 provided continuously from the large-diameter support hole 240 to the other end, and an annular step portion 242 provided between the large-diameter support hole 240 and the small-diameter support hole 241. A radial ball bearing 88 is disposed between the outer peripheral surface at the other end of the small-diameter support portion 215 of the fixed ramp 200 and the large-diameter support hole 240 of the input gear 83. That is, the outer peripheral surface of the small-diameter support portion 215 of the fixed ramp 200 (which is flush with the outer peripheral surface of the support protrusion 138) serves as a support surface for the radial ball bearing 88. A retaining ring 142 is provided on the outer peripheral surface of the small-diameter support portion 215 of the fixed ramp 200, at one end side of the radial ball bearing 88.

[0067] As a result, radial ball bearing 88 is disposed so as to be sandwiched in the axial direction between a step portion 242 provided on the inner peripheral surface of input gear 83 and a retaining ring 142 provided on the outer peripheral surface of small diameter support portion 215 of fixed ramp 200, and axial movement with respect to input gear 83 and fixed ramp 200 is restricted. Referring to Fig. 7, the other end face of large diameter ramp portion 216 of fixed ramp 200 is formed with a plurality of ball grooves 224 (three in this embodiment), which extend in an arc shape at a predetermined inclination angle along the circumferential direction and have an arc-shaped cross section in the radial direction. The inclination angle of the inclined surface along the circumferential direction of each ball groove 224 may be changed partway, or a recess may be formed in the middle or at the end of the inclined surface along the circumferential direction.

[0068] 6 and 7 , the rotary / linear motion ramp 201 is configured as a stepped cylinder having an insertion hole 225 in the radial center. The rotary / linear motion ramp 201 includes a large-diameter ramp portion 227 disposed at one end, an intermediate-diameter support portion 228 extending from the large-diameter ramp portion 227 to the other end, and a small-diameter support portion 229 extending from the intermediate-diameter support portion 228 to the other end. A plurality of ball grooves 231 (three in this embodiment) are formed on one end surface of the large-diameter ramp portion 227, each extending in an arc shape at a predetermined inclination angle along the circumferential direction and having an arc-shaped cross section in the radial direction. The inclination angle of the inclined surface along the circumferential direction of each ball groove 231 may be varied midway, or a recess may be formed midway or at the end of the inclined surface along the circumferential direction. Balls 202 are rollably interposed between the ball grooves 224 of the large diameter ramp portion 216 of the fixed ramp 200 and the ball grooves 231 of the large diameter ramp portion 227 of the rotary / linear ramp 201. In this embodiment, to stabilize operation, retainers 233 are provided to restrict relative movement of the balls 202 in the circumferential direction. Note that the retainers 233 may not be employed to reduce the number of parts.

[0069] When a rotational torque is applied to the rotary / linear ramp 201, the balls 202 roll between the ball grooves 224 of the large diameter ramp portion 216 of the fixed ramp 200 and the ball grooves 231 of the large diameter ramp portion 227 of the rotary / linear ramp 201, causing the difference in rotation between the fixed ramp 200 and the rotary / linear ramp 201 to vary the relative axial distance between the fixed ramp 200 and the rotary / linear ramp 201. An engaging portion 236 for engaging with an adjuster member 207 (described later) is provided on the outer peripheral surface of the small diameter support portion 229 of the rotary / linear ramp 201 over the entire axial area.

[0070] Referring to FIG. 6 , the nut member 206 is disposed inside the input gear 83, on the other end side of the large-diameter ramp portion 227 of the rotary-to-linear ramp 201. The input gear 83 has an engagement portion 245 for engaging with the nut member 206 formed on the inner circumferential surface at the other end of the small-diameter support hole 241. Referring to FIGS. 6 and 7 , an engagement portion 248 for engaging with the input gear 83 is formed on the outer circumferential surface of the nut member 206 over the entire axial direction. The input gear 83 and the nut member 206 are engaged with each other via the engagement portions 245, 248 so as to be slidable in the axial direction but with relative rotation restricted. In this embodiment, the engagement portions 245, 248 of the input gear 83 and the nut member 206 are configured by spline engagement. Other known techniques, such as serrations or hexalobular engagement, may also be used for the engagement portions 245, 248 of the input gear 83 and the nut member 206.

[0071] Referring to FIG. 7 , the nut member 206 has a large-diameter through hole 250 formed at one end thereof, a small-diameter through hole 251 formed continuously from the large-diameter through hole 250 to the other end thereof, and an annular step portion 252 formed between the large-diameter through hole 250 and the small-diameter through hole 251. A female thread portion 253 is formed on the inner circumferential surface of one end of the small-diameter through hole 251. Referring to FIG. 6 , an annular protrusion 254 having a trapezoidal cross section protrudes radially outward from the outer circumferential surface of the other end of the nut member 206. The nut member 206 is disposed such that the outer circumferential end of the annular protrusion 254 is adjacent to the inner circumferential surface of the intermediate-diameter recess 55 of the piston 52. A retaining ring 256 is provided on the inner circumferential surface of the intermediate-diameter recess 55 of the piston 52, on one end side of the annular protrusion 254 of the nut member 206. This restricts relative movement of the nut member 206 toward the one end thereof with respect to the piston 52. The intermediate diameter support portion 228 of the rotary / linear motion ramp 201 is disposed within the large diameter through-hole 250 of the nut member 206 .

[0072] 7 , an end stopper (a circumferentially uneven portion) 262 for preventing excessive relative rotation of the nut member 206 in the release direction relative to the rotary / linear ramp 201 is provided between a step portion 252 between the large-diameter through hole 250 and the small-diameter through hole 251 of the nut member 206 and a step portion 260 between the intermediate-diameter support portion 228 and the small-diameter support portion 229 of the rotary / linear ramp 201. This prevents the nut member 206 from retracting beyond its initial position (moving toward one end) relative to an adjuster member 207 (described later) when the brake is released. An adjuster member 207 is disposed inside the nut member 206. A thrust bearing 264 abutting against the other end surface of the nut member 206 is disposed around the adjuster member 207 within the small-diameter recess 56 of the piston 52. A washer 265 that abuts against the other end surface of the thrust bearing 264 is arranged around the adjuster member 207 within the small diameter recess 56 of the piston 52. The washer 265 abuts against the inner circumferential surface and the bottom surface of the small diameter recess 56 of the piston 52.

[0073] 7 , one end face of the adjuster member 207 abuts against an annular step portion 260 between the intermediate diameter support portion 228 and the small diameter support portion 229 of the rotary / linear ramp 201. The other end face of the adjuster member 207 is disposed near the bottom surface of the small diameter recess 56 of the piston 52. The adjuster member 207 includes an engagement recess 271 provided on one end face, an accommodating recess 272 provided on the other end face, and an annular partition wall portion 273 between the engagement recess 271 and the accommodating recess 272 and having an insertion hole 275 in the radial center. A male thread portion 277 is formed on the outer peripheral surface of the adjuster member 207 over the entire axial length. The male thread portion 277 provided on the outer peripheral surface of the adjuster member 207 and the female thread portion 253 provided on the inner peripheral surface of the small diameter through hole 251 of the nut member 206 are threadedly engaged to form a screw mechanism 208 (threaded portion 278).

[0074] An engagement portion 280 for engaging with the outer circumferential surface of the small diameter support portion 229 of the rotary / linear ramp 201 is formed over the entire axial length on the inner circumferential surface of the engagement recess 271 of the adjuster member 207. The small diameter support portion 229 of the rotary / linear ramp 201 is disposed within the engagement recess 271 of the adjuster member 207, and the adjuster member 207 and the rotary / linear ramp 201 (small diameter support portion 229) are engaged with each other via the respective engagement portions 280, 236, with relative rotation restricted. In this embodiment, the mutual engagement portions 280, 236 of the adjuster member 207 and the rotary / linear ramp 201 are configured by spline engagement. The mutual engagement portions 280, 236 of the adjuster member 207 and the rotary / linear ramp 201 may be formed by other known techniques, such as serrations or hexalobular projections.

[0075] A center rod 283 is inserted through the large-diameter insertion hole 210 and the small-diameter insertion hole 211 of the fixed ramp 200, the insertion hole 225 of the rotary-linear-motion ramp 201, and the interior of the adjuster member 207, including the insertion hole 275. The center rod 283 has a large-diameter head 285 located at one end and a small-diameter shaft portion 286 extending continuously from the large-diameter head 285 to the other end. The large-diameter head 285 of the center rod 283 is disposed within the large-diameter insertion hole 210 of the fixed ramp 200, and the other annular end face of the large-diameter head 285 abuts against a step portion 212 between the large-diameter insertion hole 210 and the small-diameter insertion hole 211. The small-diameter shaft portion 286 of the center rod 283 extends to near the bottom surface of the small-diameter recess 56 of the piston 52.

[0076] The reaction force transmission surface 136, which is one end surface of the large-diameter head 285 of the center rod 283, and the detection surface 172 of the thrust detection sensor 70 abut against each other at their spherical surfaces. In this embodiment, the detection surface 172 of the thrust detection sensor 70 is formed as a convex spherical surface that protrudes toward the other end, while the reaction force transmission surface 136 is formed as a concave spherical surface that recesses toward the other end. The curvature of the concave spherical surface on the reaction force transmission surface 136 side is set to be approximately the same as or greater than the curvature of the convex spherical surface on the thrust detection sensor 70 side. This absorbs assembly play due to component tolerances and tilt of the center bolt 126 relative to the thrust detection sensor 70 caused by, for example, elastic deformation of the pair of claws 32, 32 when thrust is generated, thereby improving thrust detection accuracy. Note that at least one of the reaction force transmission surface 136 of the large-diameter head 285 of the center rod 283 and the detection surface 172 of the thrust detection sensor 70 may be formed as a spherical surface, and the other may be formed as a flat surface.

[0077] Within the accommodation recess 272 of the adjuster member 207, from one end to the other, a thrust ball bearing 288, a plurality of disc springs 289, 289, and a washer 290 are arranged around the small diameter shaft portion 286 of the center rod 283 from one end to the other, from the partition wall portion 273 toward the other end. A retaining ring 292 is provided at the other end of the center rod 283. This retaining ring 292 is in contact with the inner circumferential surface of the washer 290, that is, a tapered surface 295 thereof.

[0078] The disc springs 289 are assembled with a predetermined biasing force, which prevents the rotary / linear ramp 201 from rotating until a predetermined rotational torque is applied to the rotary / linear ramp 201. The biasing force of the multiple disc springs 289 prevents the fixed ramp 200, the rotary / linear ramp 201, and the ball 202 from separating from each other, even if vibrations are applied while the vehicle is running. The multiple disc springs 289 can bend by an amount that causes the rotary / linear ramp 201 to move linearly while rotating. Although the present embodiment employs multiple disc springs 289, other known biasing means, such as a coil spring or a coil wave spring, may also be employed.

[0079] The thrust ball bearing 288 supports the biasing force of the plurality of disc springs 289, 289, and supports the plurality of disc springs 289, 289 and the adjuster member 207 so as to be relatively rotatable. Note that instead of the thrust ball bearing 288, other known technologies such as a thrust roller bearing or a washer (slide bearing) may be employed.

[0080] Next, the operation of the disc brake 1B according to the second embodiment will be described. During braking during normal driving, the electric motor 65 is driven to rotate in the apply direction in response to a command from the control board. As the electric motor 65 rotates in the apply direction, the rotation in the apply direction is transmitted to the input gear 83 of the brake mechanism 67 via the reduction gear 66. Subsequently, as the input gear 83 of the brake mechanism 67 rotates, the nut member 206 rotates. If there is an axial gap between the disc rotor D and the inner and outer brake pads 2, 3, almost no reaction force is applied in the axial direction to the threaded portion 278 between the female thread portion 253 of the nut member 206 and the male thread portion 277 of the adjuster member 207. Therefore, the threaded portion 278 between the adjuster member 207 and the nut member 206 cannot rotate together. Therefore, the adjuster member 207 does not rotate, and only the nut member 206 rotates and moves forward (toward the other end). As the nut member 206 advances, the piston 52 advances together with the thrust bearing 264 and the washer 265 , and as the piston 52 advances, the inner brake pad 2 is pressed against the disc rotor D.

[0081] Next, the caliper 4 moves toward one end relative to the carrier 5 due to a reaction force against the pressing force of the piston 52 against the inner brake pad 2, and the outer brake pad 3 abutting against the pair of claws 32, 32 begins to press against the disc rotor D. The reaction force against the pressing force of the inner and outer brake pads 2, 3 against the disc rotor D is applied to the threaded portion 278 between the nut member 206 and the adjuster member 207, and this time the nut member 206 and the adjuster member 207 rotate together, and the rotary / linear ramp 201 rotates. Then, due to the action of the ball ramp mechanism 203, the rotary / linear ramp 201 advances while rotating (moves toward the other end). Then, as the rotary / linear ramp 201 advances, the adjuster member 207 advances while rotating against the biasing force of the multiple disc springs 289, 289, and the nut member 206 advances while rotating via the threaded portion 278. This causes the piston 52 to move forward, increasing the pressing force of the inner and outer brake pads 2, 3 against the disc rotor D, thereby generating a braking force for the vehicle. Thereafter, when the thrust detection sensor 70 detects that a predetermined braking force has been reached, a command is sent from the control board to stop the supply of electricity to the electric motor 65.

[0082] Therefore, during braking, a reaction force against the pressing force from the pair of inner and outer brake pads 2, 3 by the piston 52 onto the disc rotor D is applied to the thrust detection sensor 70 in the following order: piston 52 → washer 265 → thrust bearing 264 → nut member 206 → threaded portion 278 between the nut member 206 and adjuster member 207 → adjuster member 207 → ball ramp mechanism 203 → step portion 212 between the large diameter insertion hole 210 and the small diameter insertion hole 211 of the fixed ramp 200 → large diameter head 285 of the center rod 283 → thrust detection sensor 70. In addition, the force of the wave washer 86 is applied to the thrust detection sensor 70 in the following order: second washer 102 → input gear 83 → step portion 242 of the input gear 83 → radial ball bearing 88 → retaining ring 142 → fixed ramp 200 → step portion 212 between the large diameter insertion hole 210 and the small diameter insertion hole 211 of the fixed ramp 200 → large diameter head 285 of the center rod 283 → thrust detection sensor 70.

[0083] On the other hand, when releasing the brake, the electric motor 65 of the drive mechanism 28 is driven to rotate in the release direction based on a command from the control board. Then, the rotation in the release direction from the electric motor 65 is transmitted to the input gear 83 of the brake mechanism 67 via the speed reducer 66. Next, the nut member 206 rotates in conjunction with the rotation of the input gear 83 in the release direction. At this time, however, a reaction force against the pressing force of the inner and outer brake pads 2, 3 against the disc rotor D is still being applied to the threaded portion 278 between the nut member 206 and the adjuster member 207. Therefore, the nut member 206 and the adjuster member 207 rotate together in the release direction, and the rotation-to-linear ramp 201 also rotates in the release direction, returning the rotation-to-linear ramp 201 to its initial position relative to the fixed ramp 200.

[0084] Subsequently, as the electric motor 65 continues to rotate in the release direction, only the nut member 206 moves backward while rotating relative to the adjuster member 207, while the piston 52 also returns to a position where a predetermined pad clearance is ensured, and then power to the electric motor 65 is stopped. As a result, the braking force exerted by the pair of inner and outer brake pads 2, 3 on the disc rotor D is released. Note that when the piston 52 is returned to its initial position, for example, for pad replacement or pad remaining amount estimation control, the control board detects interference of an end stopper 262 provided between the nut member 206 and the rotary / linear ramp 201 based on a change in current of the electric motor 65, and power to the electric motor 65 is stopped.

[0085] The disc brake 1B according to the second embodiment described above includes the rotary-to-linear motion converting mechanism 85B according to the second embodiment, and therefore, in addition to the effects of the disc brake 1A according to the first embodiment described above, it is possible to reduce component costs. Furthermore, in the disc brake 1B according to the second embodiment, the washer 265 of the thrust bearing 264 and the bottom surface of the piston 52 may abut against each other via their spherical surfaces, or at least one of the washer 265 of the thrust bearing 264 and the bottom surface of the piston 52 may be formed as a spherical surface and abut against each other. This arrangement absorbs assembly play due to component tolerances and tilt of the piston 52 relative to the nut member 206 when thrust is generated, thereby improving the efficiency of thrust transmission from the nut member 206 to the piston 52.

[0086] Furthermore, in the rotary-to-linear motion conversion mechanism 85B according to the second embodiment, the threaded portion 278 between the adjuster member 207 and the nut member 206 and the ball ramp mechanism 203 have the same lead (axial movement amount per rotation), thereby improving controllability. On the other hand, if the lead of the threaded portion 278 between the adjuster member 207 and the nut member 206 is increased relative to the ball ramp mechanism 203, the movement speed in the pad clearance region can be increased, thereby improving responsiveness. Furthermore, by changing the inclination angles of the ball grooves 224, 231 of the fixed ramp 200 and the rotary-to-linear ramp 201 of the ball ramp mechanism 203 during operation, for example, the lead is set to the same as the lead of the threaded portion 278 between the adjuster member 207 and the nut member 206 immediately after the start of operation of the ball ramp mechanism 203, and then decreasing the lead as the rotational angle of the rotary-to-linear ramp 201 increases, the current required to generate a large pressing force can be reduced.

[0087] Although the disc brake 1B according to the second embodiment employs a ball ramp mechanism 203 as the rotary-to-linear motion converting mechanism 85B according to the second embodiment, a roller ramp mechanism using cylindrical rollers instead of the balls 128 may also be employed. In this roller ramp mechanism, the fixed ramp 200 and the rotary-to-linear motion ramp 201 need to be provided with rolling grooves formed in an inclined rectangular or trapezoidal cross section, rather than ball grooves 224, 231 formed in an inclined arc-shaped cross section.

[0088] The present invention is not limited to the above-described embodiments, but includes various modifications. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those including all of the described configurations. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, or to add the configuration of another embodiment to the configuration of one embodiment. Furthermore, it is possible to add, delete, or replace part of the configuration of each embodiment with other configurations.

[0089] This application claims priority to Japanese Patent Application No. 2024-98989, filed June 19, 2024. The entire disclosure of Japanese Patent Application No. 2024-98989, filed June 19, 2024, including the specification, claims, drawings, and abstract, is incorporated herein by reference in its entirety.

[0090] DESCRIPTION OF SYMBOLS 1A, 1B Disc brake (electric brake device), 2 Inner brake pad (braking member), 3 Outer brake pad (braking member), 52 Piston (output member), 65 Electric motor, 67 Brake mechanism, 70 Thrust detection sensor, 83 Input gear (input member), 85A Rotational-linear motion conversion mechanism according to first embodiment, 85B Rotational-linear motion conversion mechanism according to first embodiment, 86 Wave washer (elastic member), 87 Thrust bearing, 88 Radial ball bearing, 106 End plate (support member), 126 Center bolt (fixed member), 127 Nut member (rotational-linear motion member), 128 Ball, 129 Ball screw mechanism, 165 Contact surface (nut member), 166 Contact surface (first race), 200 Fixed ramp (fixed member), 201 Rotational-linear motion ramp (rotational-linear motion member), 202 Ball, 203 Ball ramp mechanism, 206 Nut member (rotary and linear motion member), 208 screw mechanism, 264 thrust bearing, D disk rotor (braked member)

Claims

1. An electric brake device comprising: an electric motor; a brake mechanism that presses a braking member against a member to be braked by rotation from the electric motor; and a thrust detection sensor that detects the pressing force of the braking member on the member to be braked by the brake mechanism, wherein the brake mechanism comprises: an input member to which rotation from the electric motor is input; a rotary-to-linear motion conversion mechanism having a linear motion member that moves linearly in conjunction with the rotation of the input member, the linear motion member pressing the braking member against the member to be braked via an output member; an elastic member that urges the rotary-to-linear motion conversion mechanism together with the input member toward the thrust detection sensor; a radial bearing arranged between the input member and the rotary-to-linear motion conversion mechanism; and a thrust bearing arranged between the rotary-to-linear motion conversion mechanism and the output member.

2. An electric brake device according to claim 1, wherein the radial bearing is a ball bearing.

3. An electric brake device according to claim 1, wherein the rotary-linear motion conversion mechanism comprises a ball screw mechanism including a fixed member whose relative movement and rotation with respect to a support member are restricted, and the linear motion member, and the linear motion member is a rotary-linear motion member that moves linearly while rotating in accordance with the rotation of the input member.

4. An electric brake device according to claim 1, wherein the rotary-linear motion conversion mechanism comprises a ball ramp mechanism or a roller ramp mechanism comprising a fixed member whose relative movement and rotation with respect to a support member are restricted, and the linear motion member, and the linear motion member is a rotary-linear motion member that moves linearly while rotating in accordance with the rotation of the input member.

5. An electric brake device according to claim 3 or 4, characterized in that the fixing member has a support surface for the radial bearing on the same plane as an engagement surface with the support member.

6. An electric brake device according to claim 1, characterized in that, when pressed, at least one of the contact surfaces with which the linear motion members of the rotary-to-linear motion conversion mechanism come into contact is formed into a spherical surface.

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