Disc brake

Abstract

To provide a disc brake that improves the degree of freedom in arrangement of its constituent members and also improves its detection accuracy in a rotation angle detection means for a motor.SOLUTION: A disc brake 1 includes: an electric motor 32; a piston 53 for pressing an inner brake pad 2 with rotation from the electric motor 32; a magnet member 141 to which rotation from the electric motor 32 is transmitted and rotates around an axis of rotation arranged at a position different from the axis of rotation of the electric motor 32; and a magnetic detection IC chip 142 arranged opposite the magnet member 141 and detecting a change in a magnetic flux caused by rotation of the magnet member 141. Thus, a degree of freedom increases for arrangement of the magnet member 141 and the magnetic detection IC chip 142, and a space in a gear housing 60 and on a control board 64 can be effectively utilized.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a disc brake used for braking a vehicle. [Background technology]

[0002] As a conventional technique, Patent Document 1 discloses a disc brake that reduces the number of parts and enables miniaturization, improving mountability on a vehicle. The disc brake described in Patent Document 1 is provided with a rotation angle detection means for detecting the rotation angle of the rotating shaft of an electric motor. The rotation angle detection means includes a magnet member and a magnetic detection IC chip. The magnet member is concentrically arranged on an extension line from the tip of the rotating shaft of the electric motor along the axial direction, and rotates with the rotation of the rotating shaft of the electric motor. Meanwhile, the magnetic detection IC chip is arranged on a control board so as to face the magnet member along the axial direction of the rotating shaft of the electric motor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-34045 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the disc brake described in the above-mentioned Patent Document 1, there is no freedom in the arrangement of components (such as magnet members and magnetic detection IC chips) that constitute the rotation angle detection means of the electric motor, and the space cannot be used effectively. Moreover, improving the detection accuracy of the rotation angle detection means has long been an issue.

[0005] It is an object of the present invention to provide a disk brake that improves the degree of freedom in the arrangement of components in a motor rotation angle detection means and improves the detection accuracy. [Means for solving the problem]

[0006] As a means for solving the above problems, the disc brake according to the present invention includes a motor, a pressing portion that presses a friction pad by rotation from the motor, a detected portion to which the rotation from the motor is transmitted and that rotates about a rotation axis that is disposed at a position different from the rotation axis of the motor, and a detection portion that is disposed opposite the detected portion and detects a change accompanying the rotation of the detected portion. The detection target portion has a gear on its outer circumferential surface, and rotation from the motor is transmitted through the gear. The detection target portion is disposed in a position where the gear meshes with a reduction gear that transmits the rotation from the motor to the pressing portion in the axial direction of the rotation shaft of the motor. It is characterized by the above. Effect of the Invention

[0007] According to the disk brake of the present invention, the motor rotation angle detection means can have an improved degree of freedom in terms of the arrangement of its components, and can also have an improved detection accuracy. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a perspective view of a disc brake according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a view of the disc brake according to the embodiment as viewed from the outer side. [Diagram 3] FIG. 2 is a cross-sectional view of the disc brake according to the embodiment. [Figure 4] FIG. 4 is an enlarged cross-sectional view of the inside of the gear housing in FIG. 3 . [Diagram 5] FIG. 2 is a diagram of the disc brake according to the embodiment as viewed from the inner side, with the cover member and the control board omitted. [Figure 6] FIG. 2 is a view of the disc brake according to the embodiment as viewed from the inner side, with the illustration of the cover member omitted. [Figure 7] FIG. 13 is a diagram showing changes in the mechanical angle of the rotating shaft and the sensor angle of the magnet member corresponding to the electrical angle (the phase of the output current to the electric motor) supplied to the electric motor when the electric motor is driven in the disc brake according to the embodiment of the present invention. [Figure 8]FIG. 11 is a view of a disc brake according to another embodiment as viewed from the inner side, with a cover member and a control board omitted. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, this embodiment will be described in detail with reference to FIGS. 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 32 during normal driving. In the following description, the inside of the vehicle is referred to as the inner side, and the outside of the vehicle is referred to as the outer side. As shown in Figs. 1 and 2, the disc brake 1 includes a pair of inner brake pads 2 (see Fig. 3) and outer brake pads 3 arranged on both sides in the axial direction of a disc rotor D (see Fig. 3) attached to a rotating part of the vehicle, and a caliper 4. The disc brake 1 is configured as a floating caliper type. The pair of inner brake pads 2 and outer brake pads 3, and the caliper 4 are supported by a bracket 5 fixed to a non-rotating part such as a knuckle of the vehicle so as to be movable in the axial direction of the disc rotor D. The pair of inner brake pads 2 and outer brake pads 3 correspond to friction pads.

[0010] As shown in FIG. 1 and FIG. 2, the bracket 5 includes a pair of pin insertion portions 12, 12 into which the slide pins 10, 10 are respectively inserted, and inner and outer support portions 14, 15 that are integrally connected to the pair of pin insertion portions 12, 12 and independently support the inner and outer brake pads 2, 3, respectively. The pair of pin insertion portions 12, 12 are spaced apart along the rotation direction of the disc rotor D, and both extend along the axial direction of the disc rotor D. Each pin insertion portion 12 is formed in a cylindrical shape with a bottom. The slide pin 10 is inserted into each pin insertion portion 12. The opening side of each pin insertion portion 12 faces the inner side, and the bottom side faces the outer side. A cylindrical pin hole boss portion 16 is formed at the inner end of each pin insertion portion 12. The inner support portion 14 is integrally connected to the inner side of each pin insertion portion 12. An outer support portion 15 is connected to the inner support portion 14 of each pin insertion portion 12 along the axial direction of the disc rotor D at a distance from the inner support portion 14 to the outer side.

[0011] The inner support portion 14 is composed of a pair of inner arm portions 20, 20 extending from the pair of pin insertion portions 12, 12 in directions substantially perpendicular to each other, 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 23, 23 penetrating along the axial direction of the disc rotor D are formed at both ends of the inner beam portion 21 in the rotation direction of the disc rotor D. The bracket 5 is attached to a non-rotating portion of the vehicle via the through holes 23, 23 provided in the inner support portion 14 (inner beam portion 21). On the other hand, the outer support portion 15 is composed of a pair of outer arm portions 25, 25 extending in a direction substantially perpendicular to each other from the pin insertion portions 12, 12, and an outer beam portion 26 connecting the ends of the pair of outer arm portions 25, 25. The outer brake pad 3 is supported inside the pair of outer arm portions 25, 25 so as to be freely movable along the axial direction of the disc rotor D.

[0012] 1 to 3, the caliper 4 includes a caliper body 30 which is the main body of the caliper 4, and a drive mechanism 31 which applies a thrust to a piston 53 in a cylinder portion 34 of the caliper body 30. The caliper body 30 is provided with a cylindrical cylinder portion 34 which is disposed on a base end side facing the inner brake pad 2 and opens facing the inner brake pad 2, a pair of claw portions 35, 35 which extend from the cylinder portion 34 to the outer side across the disc rotor D and are disposed on a tip side facing the outer brake pad 3, and a pair of caliper arms 36, 36 which extend outward from the cylinder portion 34. Slide pins 10, 10 are fixed to each of the caliper arms 36, 36 by mounting bolts 38. The slide pins 10, 10 are slidably inserted into the pin insertion portions 12, 12, thereby supporting the caliper body 30 (caliper 4) relative to the bracket 5 so as to be slidable along the axial direction of the disc rotor D. Rubber pin boots 40, 40 having an expandable bellows portion covering the slide pins 10, 10 are provided between the caliper arms 36, 36 of the caliper body 30 and the pin insertion portions 12, 12 of the bracket 5.

[0013] In the following description, for convenience, the inner side (the cover member 78 side) will be referred to as one end and the outer side (the disc rotor D side) as the other end. As shown in Figs. 3 and 4, the cylinder portion 34 of the caliper body 30 has a bottomed cylinder bore 50 that is open at the other end side on the inner brake pad 2 side and closed at one end side by a bottom wall 46 having an insertion hole 47. A main rod portion 151 of a spindle 150 described later is rotatably supported in the insertion hole 47 provided in the bottom wall 46 of the cylinder portion 34. A piston 53 is accommodated in the cylinder bore 50 of the cylinder portion 34 so as to be unable to rotate relative to the cylinder portion 34 and to be movable in the axial direction. The piston 53 presses the inner brake pad 2 and is formed in a bottomed cup shape consisting of a bottom portion 54 and a cylindrical portion 55. The piston 53 is accommodated in the cylinder bore 50 of the cylinder portion 34 so that the bottom portion 54 faces the inner brake pad 2. The piston 53 corresponds to a pressing portion.

[0014] A plurality of recesses 58 are provided on the outer circumferential side of the other end surface of the bottom 54 of the piston 53, which faces the inner brake pad 2. A protrusion (not shown) formed on the back surface of the inner brake pad 2 engages with these recesses 58. This engagement makes the piston 53 unable to rotate relative to the cylinder bore 50 and, by extension, the caliper body 30. A seal member 57 is disposed on the inner circumferential surface of the other end of the cylinder bore 50. The piston 53 is accommodated in the cylinder bore 50 so as to be movable in the axial direction while in contact with the seal member 57. A dust boot 56 is interposed between the outer circumferential surface of the bottom 54 side of the piston 53 and the inner circumferential surface of the other end of the cylinder bore 50. The seal member 57 and the dust boot 56 prevent foreign matter from entering the cylinder bore 50.

[0015] A gear housing 60 is disposed on the bottom wall 46 side of the cylinder portion 34 of the caliper body 30. A motor gear assembly 63 and a control board 64 are housed inside the gear housing 60. A support recess 67 is formed on the surface on the other end side of the bottom wall of the gear housing 60, in which the bottom wall 46 of the cylinder portion 34 (cylinder bore 50) is supported. The bottom wall 46 of the cylinder portion 34 (cylinder bore 50) is airtightly supported by the support recess 67 of the gear housing 60 by a seal member 68. A first opening 71 is formed on the bottom wall of the support recess 67, through which a small diameter cylindrical portion 153 of a carrier 117 including a spindle 150, which will be described later, is inserted. A second opening 72 is formed on the bottom wall of the gear housing 60, through which a main body portion of the electric motor 32 is inserted and fixed.

[0016] Connectors 76, 76 electrically connected to the control board 64 are provided on a side wall of the gear housing 60 adjacent to the electric motor 32. One end opening of the gear housing 60 is closed by a cover member 78, and the cover member 78 is air-tightly attached to the gear housing 60 via a seal member 79. With reference to Fig. 1, the gear housing 60 including the cover member 78 is connected to the cylinder portion 34 of the caliper body 30 by a plurality of mounting bolts 86 (only one is shown in Fig. 1).

[0017] 3 and 4, the drive mechanism 31 includes an electric motor 32, a spur gear reduction mechanism 88 and a planetary gear reduction mechanism 89 that amplify the rotational torque from the electric motor 32, and a rotary-to-linear motion conversion mechanism 90 to which rotation from the spur gear reduction mechanism 88 and the planetary gear reduction mechanism 89 is transmitted and which applies thrust to the piston 53. The electric motor 32 is disposed approximately parallel to the cylinder portion 34. The main body of the electric motor 32 is inserted and fixed in the second opening 72 of the gear housing 60. The rotating shaft 33 of the electric motor 32 extends into the gear housing 60 along the axial direction of the disc rotor D.

[0018] The spur gear reduction mechanism 88 has a first reduction gear 93 and a second reduction gear 94. The first reduction gear 93 corresponds to the reduction gear. The first reduction gear 93 is formed cylindrically and has a hole 98 into which the rotating shaft 33 of the electric motor 32 is press-fitted and fixed, and a gear 99 formed on the outer circumferential surface. The second reduction gear 94 includes a large-diameter gear 105 that extends to the other end side and meshes with the gear 99 of the first reduction gear 93, and a cylindrical sun gear 106 that extends from the inside of the gear 105 toward the other end side concentrically with the gear 105. The sun gear 106 has a smaller diameter than the gear 105. One end of the gear 105 and one end of the sun gear 106 are integrally connected to each other by an annular wall portion 108.

[0019] A hole 110 is formed in the second reduction gear 94 along the axial direction at its radial center. A support rod 153 of a spindle 150 (described later) is inserted into the hole 110. As a result, the second reduction gear 94 is supported by the support rod 153 of the spindle 150 so as to be rotatable relative to the gear housing 60. The sun gear 106 has a gear 107 on its outer circumferential surface. The sun gear 106 is configured as a part of a planetary gear reduction mechanism 89 (described later). The rotation from the rotating shaft 33 of the electric motor 32 is transmitted to the second reduction gear 94 via the gear 99 of the first reduction gear 93.

[0020] The planetary gear reduction mechanism 89 has the sun gear 106 of the second reduction gear 94 described above, a plurality of (four in this embodiment) planetary gears 115, an internal gear 116, and a carrier 117. Each planetary gear 115 has a gear 120 that meshes with the gear 107 of the sun gear 106 of the second reduction gear 94, and a hole 121 through which a pin 148 erected from the carrier 117 is rotatably inserted. Each planetary gear 115 is disposed around the sun gear 106 at equal intervals in the circumferential direction.

[0021] The internal gear 116 is disposed inside the large gear 105 of the second reduction gear 94. The internal gear 116 includes internal teeth 135 with which the gears 120 of the planetary gears 115 mesh, and an annular wall portion 136 that extends continuously from one end of the internal teeth 135 toward the radial center and restricts axial movement of each planetary gear 115. The internal gear 116 is restricted from moving radially and axially with respect to the gear housing 60, and is supported so as to be non-rotatable relative to the gear housing 60.

[0022] The carrier 117 is formed with a polygonal hole 124 penetrating in the axial direction at approximately the center in the radial direction. The polygonal hole 124 has an inner peripheral surface formed, for example, in a hexagonal shape. The carrier 117 is composed of a large-diameter annular plate portion 125 and a small-diameter cylindrical portion 126 that protrudes concentrically from the large-diameter annular plate portion 125 toward the other end. The small-diameter cylindrical portion 126 of the carrier 117 is inserted into the first opening 71 of the gear housing 60. On the outer periphery side of the large-diameter annular plate portion 125 of the carrier 117, a plurality of pins 129 extend toward one end at intervals along the circumferential direction so as to correspond to each planetary gear 115. Each pin 129 is rotatably inserted into the hole portion 121 of each planetary gear 115. The rotation from the rotating shaft 33 of the electric motor 32 is transmitted to the sun gear 106 of the planetary gear reduction mechanism 98 via the spur gear reduction mechanism 88 (first reduction gear 93 and second reduction gear 94). As the sun gear 106 of the planetary gear reduction mechanism 89 rotates, each planetary gear 115 rotates about its own rotational axis while revolving around the rotational axis of the sun gear 106, causing the carrier 117 to rotate about its own rotational axis.

[0023] Furthermore, the polygonal hole 124 of the carrier 117 is fitted into a polygonal rod portion 152 of a spindle 150 of the rotary-linear motion conversion mechanism 90 described later, so that the rotational torque can be transmitted between the carrier 117 and the spindle 150. A wave washer 131 and a washer 132 are inserted into the small diameter cylindrical portion 126 of the carrier 117. The washer 132 is abutted against one end surface of the bottom wall 46 of the cylinder portion 34. The cylinder portion 34 and the carrier 117 are biased in a direction away from each other by the biasing force of the wave washer 131. In this embodiment, the spur gear reduction mechanism 88 and the planetary gear reduction mechanism 89 are used as a reduction mechanism for increasing the rotational torque from the electric motor 32 to obtain a rotational force for propelling the piston 53, but the planetary gear reduction mechanism 89 alone may be used. Moreover, a reducer based on other known techniques, such as a cycloid reduction mechanism or a wave reduction mechanism, may be combined with the planetary gear reduction mechanism 89.

[0024] As shown in Figs. 4 to 6, the disc brake 1 according to this embodiment is provided with a rotation angle detection means 140 that detects the rotation angle of the rotating shaft 33 of the electric motor 32. The rotation angle detection means 140 includes a magnet member 141 and a magnetic detection IC chip 142. The magnet member 141 corresponds to a detected part. The magnetic detection IC chip 142 corresponds to a detection part. The magnet member 141 is formed in a cylindrical shape having an insertion hole 144. The magnet member 141 is rotatably supported with respect to the gear housing 60 by a support pin 145 that is inserted into the insertion hole 144. A gear 143 is formed on the outer circumferential surface of the magnet member 141.

[0025] The gear 143 of the magnet member 141 meshes with the gear 99 of the first reduction gear 93 of the spur gear reduction mechanism 88. The magnet member 141 is formed to have a diameter considerably smaller than the outer diameter of the first reduction gear 93. The magnet member 141 is formed to be thinner than the thickness (length in the axial direction) of the first reduction gear 93. With reference to FIG. 5, the magnet member 141 is disposed in the gear housing 60 on the side away from the connectors 76 and closer to the center of the disc rotor D. In other words, the magnet member 141 is disposed on the side away from the connectors 76 with respect to the rotation axis of the rotating shaft 33 of the electric motor 32, that is, on the side closer to the piston 53. Note that, as shown in FIG. 8, the magnet member 141 may be disposed in the gear housing 60 on the side closer to the connectors 76 and closer to the center of the disc rotor D. In other words, the magnet member 141 may be disposed on the side closer to the connectors 76 with respect to the rotation axis of the rotating shaft 33 of the electric motor 32, that is, on the opposite side to the piston 53. The outer diameter of the magnet member 141 shown in FIG. 8 is smaller than the outer diameter of the magnet member 141 shown in FIG.

[0026] In short, as can be seen from Fig. 5, the rotation axis of the magnet member 141 (the center of the support pin 145) and the rotation axis of the rotation shaft 33 of the electric motor 32 are parallel to each other, and are disposed at different positions within the gear housing 60. As can be seen from Fig. 4, the magnet member 141 is disposed at a position overlapping the first reduction gear 93 of the spur gear reduction mechanism 88 in the axial direction of the rotation shaft 33 of the electric motor 32. Specifically, the magnet member 141 is disposed at a position overlapping the first reduction gear 93 in the axial direction of the rotation shaft 33 of the electric motor 32 such that one end face of the magnet member 141 and one end face of the first reduction gear 93 of the spur gear reduction mechanism 88 are located on the same plane. The magnet member 141 may be disposed such that a portion along the axial direction overlaps with the first reduction gear 93 of the spur gear reduction mechanism 88 in the axial direction of the rotation shaft 33 of the electric motor 32. The magnet member 141 rotates at a predetermined reduction ratio with respect to the rotation of the rotary shaft 33 of the electric motor 32. The reduction ratio is set by the relationship of a natural number (N):the number of motor pole pairs (P).

[0027] In this embodiment, as shown in Fig. 7, the number of motor pole pairs (P) = 3, the natural number (N) = 2, and the reduction ratio is set to a relationship of 2:3 (speed ratio 3 / 2). In other words, the magnet member 141 rotates at an increased speed relative to the rotating shaft 33 of the electric motor 32, that is, at a speed 3 / 2 times faster. Note that Fig. 7 is a diagram showing the transition of the mechanical angle θm of the rotating shaft 33 and the sensor angle θs of the magnet member 141 corresponding to the electrical angle θe (phase of the output current to the electric motor 32) supplied to the electric motor 32 when the electric motor 32 is driven. In Fig. 7, the transition of the electrical angle θe is indicated by a two-dot chain line, the mechanical angle θm is indicated by a solid line, and the sensor angle θs is indicated by a one-dot chain line.

[0028] In this way, by adopting a form in which the rotation of the magnet member 141 is speeded up (deceleration ratio 2:3 (speed ratio 3 / 2)) compared to the rotation of the rotation shaft 33 of the electric motor 32 (N < P), when the electric motor 32 is driven, the sensor angle θs of the magnet member 141 becomes larger with respect to the mechanical angle θm of the rotation shaft 33 of the electric motor 32, so that a finer angle can be detected. As a result, the resolution when detecting the rotation angle of the rotation shaft 33 of the electric motor 32 can be improved compared to the constant speed (prior art), and the detection accuracy can be improved. In this embodiment, if the natural number (N) = 1 and the deceleration ratio is set to 1:3 (speed ratio 3 / 1), the resolution can be improved the most.

[0029] As shown in FIGS. 3 and 4, a magnetic detection IC chip 142 is arranged so as to face the magnet member 141 along the axial direction of the rotation shaft 33 of the electric motor 32. The magnetic detection IC chip 142 is arranged to face one end side of the magnet member 141. The magnetic detection IC chip 142 detects a change in magnetic flux (magnetic flux density) generated as the magnet member 141 rotates. The magnetic detection IC chip 142 is attached to one end face of the control board 64. The configuration of the control board 64 will be described later. Specifically, referring to FIGS. 5 and 6, the magnetic detection IC chip 142 is on the control board 64, and is arranged on the side away from each connector 76 and on the side closer to the center of the disk rotor D so as to face the magnet member 141. In other words, the magnetic detection IC chip 142 is arranged on the side away from each connector 76, that is, on the side closer to the piston 53, than the rotation axis of the rotation shaft 33 of the electric motor 32 so as to face the magnet member 141.

[0030] 8, the magnetic detection IC chip 142 is disposed on the control board 64, on the side closer to the connectors 76 and closer to the center of the disc rotor D, so as to face the magnet member 141. In other words, the magnetic detection IC chip 142 is disposed on the side closer to the connectors 76, i.e., on the opposite side to the piston 53, with respect to the rotation axis of the rotating shaft 33 of the electric motor 32, so as to face the magnet member 141. The magnetic detection IC chip 142 detects a change in magnetic flux accompanying the rotation of the magnet member 141, and the control board 64 calculates and detects the rotation angle of the rotating shaft 33 of the electric motor 32.

[0031] 3, the rotary-linear motion conversion mechanism 90 converts the rotational motion from the spindle 15, i.e., the rotational motion of the electric motor 32, into linear motion (hereinafter, referred to as linear motion for convenience) and applies thrust to the piston 53. The rotary-linear motion conversion mechanism 90 is disposed in the cylinder bore 50 of the cylinder section 34. The spindle 150 includes a main rod section 151 rotatably supported in an insertion hole 47 provided in a bottom wall 46 of the cylinder section 34 from the axial center toward one end, a polygonal rod section 152 extending integrally from the main rod section 151 toward the one end and engaging with a polygonal hole section 124 provided in approximately the radial center of the carrier 117, and a support rod section 153 extending integrally from the polygonal rod section 152 toward the one end, inserted into a hole section 110 of the second reduction mechanism 126, and rotatably supporting the sun gear 106.

[0032] The rotary-to-linear motion conversion mechanism 90 is configured by, for example, a ball and ramp mechanism, a ball screw mechanism, a screw mechanism, etc., each of which may be configured alone or in combination. Here, a detailed description of the rotary-to-linear motion conversion mechanism 90 is omitted. As shown in FIG. 3, a thrust sensor 155 is disposed between the rotary-to-linear motion conversion mechanism 90 and the bottom wall 46 of the cylinder portion 34. The thrust sensor 155 is formed in a cylindrical shape. The thrust sensor 155 detects a reaction force against the thrust from the piston 53 to the inner and outer brake pads 2 and 3. The main rod portion 151 of the spindle 150 is inserted into the thrust sensor 155. When the carrier 117 of the planetary gear reduction mechanism 89 and the spindle 150 rotate via the spur gear reduction mechanism 88 in accordance with the rotation of the electric motor 32, the piston 53 advances due to the action of the rotary-to-linear motion conversion mechanism 90, and the piston 53 can press the inner brake pad 2 against the disc rotor D.

[0033] The driving of the electric motor 32 is controlled by a command from the control board 64. The control board 64 controls the rotation (rotation direction, rotation speed, etc.) of the electric motor 32 based on various detection signals during braking in normal driving, such as detection signals from detection sensors corresponding to the driver's request and detection sensors that detect various situations in which braking is necessary, detection signals from wheel speed detection sensors that detect wheel speeds, detection signals from rotation angle detection means 140 that detects the rotation angle of the rotating shaft 33 of the electric motor 32, and detection signals from a thrust sensor 155 that detects thrust (pressing force) from the inner and outer brake pads 2 and 3 to the disc rotor D. As shown in Figs. 3 and 4, the control board 64 is disposed on one end side from the electric motor 32. In other words, the control board 64 is disposed on one end side from the electric motor 32 in the gear housing 60, between the spur gear reduction mechanism 88 and the planetary gear reduction mechanism 89, and the cover member 78.

[0034] Next, the braking and braking release actions during normal driving in the disc brake 1 according to this embodiment will be described. When braking in normal running, the electric motor 32 is driven by a command from the control board 64, and the rotation in the forward direction, i.e., the braking direction, is transmitted to the sun gear 106 of the planetary gear reduction mechanism 89 via the spur gear reduction mechanism 88 (the first reduction gear 93 and the second reduction gear 94). Due to the rotation of the sun gear 106 of the planetary gear reduction mechanism 89, each planetary gear 115 rotates about its own rotation axis while revolving about the rotation axis of the sun gear 106, and the carrier 117 rotates about its own rotation axis. That is, the rotation from the electric motor 32 is reduced and increased at a predetermined reduction ratio by passing through the spur gear reduction mechanism 88 and the planetary gear reduction mechanism 89, and is transmitted to the carrier 117. The rotation from the carrier 117 is then transmitted to the spindle 150. When the magnet member 141 rotates via the first reduction gear 93 of the spur gear reduction mechanism 88 in accordance with the rotation of the rotating shaft 33 of the electric motor 32, the magnetic detection IC chip 142 detects a change in the magnetic flux from the magnet member 141, and the control board 64 calculates and detects the rotation angle of the rotating shaft 33 of the electric motor 32.

[0035] Next, when the spindle 150 rotates in conjunction with the rotation of the carrier 117, the piston 53 advances due to the action of the rotary-linear motion conversion mechanism, pressing the inner brake pad 2 against the disc rotor D. Then, due to a reaction force against the pressing force of the piston 53 against the inner brake pad 2, the caliper body 30 moves toward the inner side relative to the bracket 5, and the claw portions 35, 35 press the outer brake pad 3 against the disc rotor D. The reaction force against the pressing force of the piston 53 against the inner brake pad 2 is detected by the thrust sensor 155. As a result, the disc rotor D is sandwiched between the pair of inner and outer brake pads 2, 3, generating a frictional force, which in turn generates a braking force for the vehicle.

[0036] On the other hand, when braking is released, the rotating shaft 33 of the electric motor 32 rotates in the reverse direction, i.e., in the braking release direction, in response to a command from the control board 64, and the rotation in the reverse direction is transmitted to the spindle 150 via the spur gear reduction mechanism 88 and the planetary gear reduction mechanism 89. As a result, the rotation of the spindle 150 in the reverse direction operates the rotary-to-linear motion conversion mechanism 90, causing the piston 53 to retreat and return to its initial state, and the braking force applied to the disc rotor D by the pair of inner and outer brake pads 2, 3 is released.

[0037] As described above, in the disc brake 1 according to this embodiment, the rotation axis of the magnet member 141 constituting the rotation angle detection means 140 and the rotation axis of the rotating shaft 33 of the electric motor 32 are disposed at different positions. This increases the degree of freedom in the arrangement of the magnet member 141 and the magnetic detection IC chip 142, and makes it possible to effectively utilize the space within the gear housing 60 and on the control board 64, thereby enabling the disc brake 1 to be made more compact.

[0038] Furthermore, in the disc brake 1 according to this embodiment, the magnet member 141 and the magnetic detection IC chip 142 are provided on the side opposite to the side on which the piston 53 is provided, with respect to the rotation axis of the rotating shaft 33 of the electric motor 32. As a result, the magnet member 141 can be disposed at a desired position in the gear housing 142, and the magnetic detection IC chip 142 can be disposed at a desired position on the control board 64, improving space efficiency.

[0039] Furthermore, in the disc brake 1 of this embodiment, the magnet member 141 has a gear 143, and rotation from the rotating shaft 33 of the electric motor 32 is transmitted to the magnet member 141 via the gear 143, so that the rotation from the electric motor 32 can be easily transmitted to the magnet member 141, and the structure can be simplified.

[0040] Furthermore, in the disc brake 1 according to this embodiment, the magnet member 141 is configured to rotate at a speed faster than the rotation of the rotating shaft 33 of the electric motor 32, so the rotation angle (sensor angle θs) of the magnet member 141 is larger than the rotation angle (mechanical angle θm) of the rotating shaft 33 of the electric motor 32. As a result, it is possible to detect a finer angle than the rotation angle of the rotating shaft 33 of the electric motor 32, and it is possible to improve the resolution when detecting the rotation angle of the rotating shaft 33 of the electric motor 32 compared to the constant speed (conventional technology). This makes it possible to improve the detection accuracy of the rotation angle of the rotating shaft 33 of the electric motor 32 by the rotation angle detection means 140.

[0041] Furthermore, in the disc brake 1 of this embodiment, the magnet member 141 is positioned in a position overlapping with the first reduction gear 93 of the spur gear reduction mechanism 88 in the axial direction of the rotating shaft 33 of the electric motor 32. Therefore, in the disc brake 1, the size can be reduced in the axial direction of the rotating shaft 33, thereby improving the mountability on a vehicle.

[0042] The above-described embodiment may also be adopted in a disc brake in which, during braking in normal driving, the brake fluid pressure supplied into the cylinder bore 50 of the caliper body 30 advances the piston 53, causing the disc rotor D to be sandwiched between a pair of inner and outer brake pads 2, 3 to generate a braking force, and, during parking braking such as when parking, rotation from the drive mechanism 31, i.e., the electric motor 32, is transmitted to the piston 53 via the spur gear reduction mechanism 88, the planetary gear reduction mechanism 89, and the rotary-to-linear conversion mechanism 90 to advance the piston 53, causing the disc rotor D to be sandwiched between the pair of inner and outer brake pads 2, 3 to generate a braking force. [Explanation of symbols]

[0043] 1 Disc brake, 2 Inner brake pad (friction pad), 3 Outer brake pad (friction pad), 32 Electric motor (motor), 53 Piston (pressure portion), 93 First reduction gear (reduction gear), 140 Rotation-to-linear motion conversion mechanism, 141 Magnet member (detected portion), 142 Magnetic detection IC chip (detection portion), 143 Gear, D Disc rotor

Claims

1. A motor; a pressing unit that presses the friction pad by rotation from the motor; a detection target portion to which rotation from the motor is transmitted and which rotates about a rotation axis that is disposed at a position different from the rotation axis of the motor; A detection section that is disposed opposite the detection target section and detects a change accompanying rotation of the detection target section; Equipped with a disc brake in which the detected part has a gear on its outer peripheral surface, rotation from the motor is transmitted via the gear, and the gear is disposed in an axial direction of the motor's rotation shaft at a position where it meshes with and overlaps a reduction gear that transmits the rotation from the motor to the pressing part.

2. The disk brake according to claim 1 , wherein the detected portion and the detector are provided on an opposite side to a side on which the pressing portion is provided, with respect to an axis of the rotating shaft of the motor.

3. The disk brake according to claim 1 or 2, wherein the detected portion rotates at a speed faster than the rotation speed of the motor.

Images