JP2008164111A - Electric disc brake - Google Patents

Abstract

A reduction in pressing force caused by thermal contraction of a brake pad can be compensated mechanically without increasing piston thrust.
An electric disc brake including a rotation-linear motion conversion mechanism that converts rotation of a motor into linear motion and transmits it to a piston, and a parking brake mechanism that can lock / unlock the rotation of the motor in the braking release direction. , A planetary gear speed reduction mechanism is provided between the motor and the rotation-linear motion conversion mechanism, and the outer periphery of the internal gear 55 of the speed reduction mechanism can be moved within the range of the moving path 59 provided in the caliper body 10. During normal braking, the position of the internal gear 55 is fixed by a gear lever 64 that engages with the protruding piece 56, and during parking braking, the gear lever 64 is disengaged to rotate the internal gear 55, The torsion spring 60 connected to the piece 56 stores the force in the piston propulsion direction, and the torsion spring 60 receives the displacement of the heat shrinkage of the brake pad. Make Hama.
[Selection] Figure 1

Description

  The present invention relates to an electric disc brake that generates a braking force by a torque of a motor, and more particularly to an electric disc brake with a parking brake to which a parking brake function is added.

  The electric disc brake with a parking brake includes a piston that presses a brake pad, a motor, a rotation-linear motion conversion mechanism that converts rotation of the motor into linear motion and transmits the linear motion, and braking of the rotor of the motor. Some have a parking brake mechanism that can lock and unlock rotation in the release direction (see, for example, Patent Document 1). In such an electric disc brake, the piston is propelled according to the rotation of the rotor of the motor, the brake pad is pressed against the disc rotor to generate a braking force, and the braking force (pressing force) is generated by the operation of the parking brake mechanism. It comes to hold.

  By the way, in the electric disc brake with parking brake described above, when the parking brake is operated at a high temperature when the brake pad is thermally expanded, the pressing force of the piston is reduced due to the contraction of the brake pad accompanying the subsequent temperature decrease. . Therefore, in the past, taking measures to increase the thrust of the piston in anticipation of a decrease in the pressing force due to the temperature drop, or taking measures to re-clamp the parking brake by starting up the control unit and stopping the vehicle after the vehicle stops (For example, refer to Patent Document 2).

JP 2003-42199 A JP 2006-232263 A

  However, the above-described measures for increasing the thrust of the piston in advance have a problem in that the strength of the component parts must be increased from the viewpoint of durability, and there is a disadvantage in terms of size and weight. On the other hand, with the measures to unclamp, it is necessary to start up the control unit even after the vehicle stops, so an increase in power consumption is inevitable, and in addition, the control unit becomes complicated and uneasy in terms of reliability remains. There was a problem.

  The present invention has been made in view of the above-described conventional problems, and the problem is that the lowering of the pressing force due to the thermal contraction of the brake pad during parking brake is not increased so much as the thrust of the piston is not increased. It is an object of the present invention to provide an electric disc brake which can be mechanically compensated for, and contributes greatly to reduction of power consumption and simplification of a control unit as well as reduction in size and weight.

  In order to solve the above problems, the present invention provides a piston that presses a brake pad, a motor, a rotation-linear motion conversion mechanism that converts rotation of the motor into linear motion and transmits the linear motion, and a rotor of the motor. A parking brake mechanism capable of locking and unlocking the rotation in the braking release direction, propelling the piston according to the rotation of the rotor of the motor, and pressing the brake pad against the disc rotor to generate a braking force In the electric disc brake that holds the rotor of the motor in the braking position by the parking brake mechanism, a speed reduction mechanism including three basic shafts is provided between the motor and the rotation-linear motion conversion mechanism, A third shaft that is free with respect to both the motor and the rotation-linear motion conversion mechanism of the speed reduction mechanism is rotatable within a predetermined range; and Serial parking brake mechanism is characterized in accordance with the rotation of said third axis of engaging the third to the axis providing the spring means for storing a force on the piston propulsion direction when operating.

  In the electric disc brake configured as described above, a force corresponding to the pressing force corresponding to the thermal expansion of the brake pad is engaged with the third shaft by rotating the third shaft of the speed reduction mechanism during parking brake. It is stored in the spring means to compensate for the decrease in the pressing force due to the heat shrinkage of the brake pad during parking brake. Further, it becomes possible to keep the piston thrust low, and as a result, there is no need to increase the strength of the component parts.

  In the present invention, the spring means may be a torsion spring disposed with a set torque. Further, the reduction mechanism composed of the three basic shafts can be a planetary gear reduction mechanism.

  The present invention may be configured to include locking means for locking and unlocking the third shaft in conjunction with the operation of the parking brake mechanism. In such a configuration, by fixing the position of the third shaft by the locking means, it is possible to obtain a braking characteristic similar to that of a conventional electric disk brake during normal braking, and there is no sense of incongruity. In this case, it is desirable to share the solenoid that is the drive source of the upper parking brake mechanism as the drive source of the locking means, thereby achieving high functionality without increasing the cost.

  According to the electric disk brake of the present invention, it is possible to compensate for the pressing force decrease due to the thermal contraction of the brake pad without increasing the piston thrust so much, so that it is possible to achieve a reduction in size and weight. Further, since reclamping is not performed, power consumption can be reduced, and the control unit can be simplified, improving the reliability of the apparatus.

  In addition, when a locking means for locking and unlocking the third shaft of the deceleration mechanism is provided in conjunction with the operation of the parking brake mechanism, the same braking characteristics as those of the conventional electric disk brake can be obtained during normal braking. So there is no sense of incongruity.

  The best mode for carrying out the present invention will be described below in detail with reference to the drawings.

  1 to 6 show the overall structure of an electric disc brake with a parking brake as one embodiment of the present invention. The electric disc brake according to the present embodiment is configured as a caliper floating type, and includes a disc rotor 1 that rotates together with wheels, a carrier 2 that is fixed to a non-rotating portion on the vehicle body side such as a suspension member, and the disc rotor 1. A pair of brake pads 3, 4 that are positioned on both sides and supported by the carrier 2; and an electric caliper 6 that is supported by the pair of slide pins 5, 5 so as to be movable in the axial direction of the disk rotor 1 with respect to the carrier 2. It has.

  The electric caliper 6 converts the rotation of the caliper body 10, the piston 11 that can contact the back of the brake pad (inner pad) 4 inside the vehicle, the motor 12, and the rotation of the motor 12 into a linear motion and transmits it to the piston 11. A ball screw mechanism (rotation-linear motion conversion mechanism) 13, a multi-axis reduction mechanism 14 that decelerates the rotation of the motor to amplify the torque, and further decelerates the rotation of the multi-axis deceleration mechanism 14 to amplify the torque. A planetary gear mechanism (from three basic shafts to a speed reduction mechanism) 15 that transmits to the screw mechanism 13, a parking brake mechanism 16, and a drive control device 17 that controls the operation of the motor 12 and the parking brake mechanism 16 are schematically configured.

  The caliper body 10 includes a bore portion 20 in which the piston 11 and the ball screw mechanism 13 are housed, and a storage portion 21 in which the multi-axis speed reduction mechanism 14, the planetary gear speed reduction mechanism 15, the parking brake mechanism 16 and the drive control device 17 are housed. And a claw portion 23 extending from the cylinder portion 22 across the disk rotor 1 to the outside of the vehicle body. The cylinder portion 22 is integrally formed with a pair of boss portions 24 for slidably fitting the pair of slide pins 5, and a cover 25 is covered at the rear end of the cylinder portion 22. ing.

  As shown well in FIG. 2, the piston 11 has a bottomed cylindrical shape, and is slidably fitted into the bore portion 15 of the cylinder portion 22 so that the bottom portion faces the inner pad 4. . The piston 11 and the bore portion 15 are sealed with a seal ring 26 and a dust seal 27 to prevent foreign matter from entering the inside.

  The motor 12 is provided in a housing 28 fixed to the caliper body 10 as well shown in FIGS. The motor 12 includes a stator 29 fitted and fixed to the inner peripheral portion of the housing 28, and a rotor 30 disposed in the stator 29. Both ends of the rotor 30 are rotatably supported by the housing 22 by bearings 31, 31, and one end thereof is inserted into the storage portion 21 of the caliper body 10.

  As shown in FIG. 2, the ball screw mechanism 13 includes a nut 31 fixed to the rear end of the piston 11, a rotatable spindle 32 fitted to the nut 31, and a mutual connection between them. And a plurality of balls (rolling elements) 34 inserted between the ball grooves 33 formed on the fitting surface. The nut 31 is attached with a key 36 slidably fitted in an axial key groove 35 formed in a part of the bore portion 20, so that the nut 31 is non-rotatable and moves in the axial direction. The caliper body 10 is supported as possible. On the other hand, a thrust bearing (needle thrust bearing) 37 is attached to the spindle 32, and the spindle 32 is abutted against an annular flange 20 a that defines the rear end of the bore portion 20 via the thrust bearing 37. . In the ball screw mechanism 13, the ball 34 rolls in the ball groove 33 according to the rotation of the spindle 32, whereby the nut 32 moves linearly, and the piston 11 follows the movement. The inner pad 4 is pressed against the disc rotor 1 by the piston 11 propelled integrally with the nut 32. On the other hand, the reaction force from the piston 11 is transmitted from the nut 32 to the caliper body 10 via the ball 34, the spindle 32 and the thrust bearing 37.

  As shown in FIG. 2, the multi-axis reduction mechanism 14 includes a first gear 41 provided on a first shaft 40 that is coaxially connected to the rear end portion of the rotor 30 of the motor 12 so as not to be relatively rotatable. The second gear 42 meshed with the first gear 41 and the third gear 43 meshed with the second gear 42 are provided. The rear end of the first shaft 40 is supported by a bearing 44 (FIG. 3) attached to the cover 25, and rotates together with the rotor 30. The second gear 42 is supported at both ends by a pair of bearings 45, 45 attached to the caliper body 10 and the cover 25, and the third gear 43 is coaxial with the ball screw mechanism 13 and the planetary gear reduction mechanism 15. Is press-fitted and fixed to the second shaft 46 disposed in the position. One end of the second shaft 46 is coupled to the spindle 32 of the ball screw mechanism 13 via a bearing 47, while the other end is supported by the cover 25 via a bearing 48. In the multi-axis reduction mechanism 38, the first gear 41 rotates according to the rotation of the first shaft 40, so that the rotation is transmitted to the second shaft 46 via the second gear 42 and the third gear 43. The second shaft 46 is rotated at a predetermined reduction ratio.

  As shown in FIG. 2, the planetary gear speed reduction mechanism 15 includes a sun gear 50 provided in the middle of the second shaft 46 and a plurality of (here, three) gears arranged around the sun gear 50. ) Planetary gear 51, planetary carrier 53 that rotatably supports each planetary gear 51 via a bearing 52, and an internal gear that is rotatably supported by the caliper body 10 via a bearing 54 and meshes with each planetary gear 51. A gear (third shaft) 55 is included. One end of the planetary carrier 53 is press-fitted and fixed to the small-diameter end of the spindle 32 constituting the ball screw mechanism 13. In the planetary gear reduction mechanism 15, the planetary gear 51 revolves while rotating on the internal gear 55 by the rotation of the sun gear 50, whereby the planetary carrier 53 rotates and the spindle 32 rotates at a predetermined reduction ratio.

  Thus, as shown in FIG. 1, a fan-shaped projecting piece 56 projecting radially outward is integrally formed on the outer periphery of the internal gear 55 constituting the planetary gear speed reduction mechanism 15. On the other hand, both ends of the caliper body 10 are defined by a first stopper surface 57 that contacts one side end 56a of the protruding piece 56 and a second stopper surface 58 that contacts the other end 56b of the protruding piece 56. An arcuate movement path 59 is formed. Therefore, the internal gear 55 can be rotated within a range in which the projecting piece 56 can move in the moving path 59.

  On the other hand, a torsion spring (spring means) 60 as a torsion spring is disposed around the bore portion 20 of the caliper body 10 as shown in FIG. It is fixed to a through hole 61 provided in the projecting piece 56 of the internal gear 55. The torsion spring 60 is set to have a screw direction so that a biasing force is applied to the internal gear 55 in the counterclockwise direction (piston propulsion direction) as shown in FIG. The original position where the one side end 56a of the projecting piece 56 abuts against the stopper surface 57 on one end side is maintained. The set torque of the torsion spring 60 is set so that the protruding piece 56 is pressed against the stopper surface 57 with a predetermined load.

  In the present embodiment, an engagement hole 62 is formed in the projecting piece 56 of the internal gear 55, and a gear lever 64 constituting a locking means 63 (FIG. 7) described later is formed in the engagement hole 62. The hook part 64a at one end is engaged and disengaged. The internal gear 55 maintains the original position shown in FIG. 1 by inserting the hook portion 64a into the engagement hole 62 during normal braking.

  As shown in FIG. 7, the parking brake mechanism 16 includes a ratchet 70 fitted and fixed to a first shaft 40 that rotates integrally with the rotor 30 of the motor 12, and a ratchet lever that restricts the rotation of the ratchet 70. 71 and a solenoid (drive source) 72 for driving the ratchet lever 71. FIG. 7 shows only the portion related to the parking brake mechanism 16 for convenience of explanation.

  A plurality of teeth 73 are formed on the outer periphery of the ratchet 70. The interval between the plurality of teeth 73 is set such that a columnar engagement protrusion 71 a provided at the tip of the ratchet lever 71 can pass therethrough. The ratchet lever 71 is rotatably supported at its intermediate portion in the longitudinal direction by a pin 75 with respect to a bracket 74 bolted to the caliper body 10. A torsion spring 76 that urges the ratchet lever 71 in a direction in which the engagement protrusion 71 a is detached from the tooth 73 of the ratchet 70 is wound around the pin 75. On the other hand, the bracket 74 is provided with a stopper portion 77 that restricts the rotation of the ratchet lever 71 in the disengagement direction. The ratchet lever 71 is provided on the stopper portion 77 when the parking brake mechanism 16 is not operated. The standby state for contact is maintained.

  Further, the other end portion of the ratchet lever 71 is positioned in the moving range of the plunger 78 of the solenoid 72. When the solenoid 72 is not energized, the plunger 78 of the solenoid 72 is positioned at a shortened end that slightly contacts the other end of the ratchet lever 71. In this state, the ratchet lever 71 is engaged with the tip of the ratchet lever 71. The standby state shown in FIG. 7 (FIG. 7) in which the protrusion 71a is detached from the tooth 73 of the ratchet 70 is maintained. On the other hand, when the solenoid 72 is energized from this standby state, as shown in FIG. 8, the plunger 78 protrudes and the ratchet lever 71 tilts around the pin 75, and the engagement protrusion 71 a at the tip thereof is on the tooth 73 of the ratchet 70. Enter the engageable position.

  Here, inclined relief surfaces 73a and recesses 73b are formed on the mutually opposing surfaces of the plurality of teeth 73 of the ratchet 70. When the first shaft 40 is rotated in the piston propulsion direction by the motor 12 from the state shown in FIG. 8, the engagement protrusion 71a of the ratchet lever 71 slides on the inclined relief surface 73a as shown in FIG. Thus, the rotation of the first shaft 40 is allowed. On the other hand, when the first shaft 40 rotates in the reverse direction from the state of FIG. 8, the engagement protrusion 71a of the ratchet lever 71 engages with the recess 73b of the tooth 73 as shown in FIG. The rotation of one shaft 40 is restricted.

  As shown in FIG. 7, the gear lever 64 constituting the locking means 63 for fixing the internal gear 55 in its original position is rotatably supported by the caliper main body 10 by a pin 65 at its middle portion in the longitudinal direction. Has been. The other end portion of the gear lever 64 opposite to the side where the hook portion 64a is provided is extended to a position where it can engage with the plunger 78 of the solenoid 72, and the plunger 78 is inserted into the other end portion. An allowable bifurcated engaging portion 64b is formed. The plunger 78 of the solenoid 72 is provided with a collar portion 78a that comes into contact with the engaging portion 64a from below. When the plunger 78 is extended by energizing the solenoid 72, the collar portion 78a is engaged. The gear lever 64 is swung by applying a pressing force to the portion 64a. As a result, as shown in FIG. 8, the hook portion 64 a of the gear lever 64 is detached from the engagement hole 62 of the internal gear 55, and the internal gear 55 can be freely rotated. The caliper body 10 is provided with a biasing means 65 that biases the gear lever 64 in a direction in which the hook portion 64a of the gear lever 64 is normally engaged with the engagement hole 62 (FIG. 7).

 As shown in FIG. 3, the drive control device 7 is disposed in the recess 25 a of the cover 25, and a control signal is transmitted via a cable 80 from an in-vehicle controller (not shown) mounted on the vehicle body side. It is supposed to be sent. The drive control device 7 and the stator 29 of the motor 12 and the solenoid 72 of the parking brake mechanism 16 are connected by signal lines 81 and 82 (FIG. 1), respectively. Further, a rotation sensor 85 for detecting the rotation position of the rotor 30 of the motor 12 is installed adjacent to the drive control device 7, and a signal line 83 (see FIG. 3) is connected between the rotation sensor 85 and the drive control circuit 7. ). The rotation sensor 85 includes a resolver stator 86 fixed to the cover 25 and a resolver rotor 87 attached to the first shaft 40. In the drive control device 7, the operation of the motor 21 and the parking brake mechanism 16 is controlled based on the braking command signal from the in-vehicle controller and the rotational position signal from the rotation sensor 85.

  The operation of the electric disc brake configured as described above will be described below.

  When operating as a normal electric brake, the energization to the solenoid 72 of the parking brake mechanism 16 is cut off, and the ratchet lever 71 has its engaging projection 71a connected to the teeth 73 of the ratchet 70, as shown in FIG. On the other hand, the gear lever 64 maintains the state in which the hook portion 64a at one end thereof is engaged with the engagement hole 62 of the projecting piece 56 of the internal gear 55. Further, as shown in FIG. 1, the internal gear 55 maintains the original position in which the one side end 56 a is brought into contact with the stopper surface 57 on one end side of the moving path 59.

  Then, based on a signal (pedal pedaling force signal or pedal displacement signal) corresponding to the driver's braking operation, the in-vehicle controller sends a braking force signal to the disk brake drive control device 17 of each wheel. Then, the drive control device 17 outputs a drive current to the stator 29 of the motor 12 and rotates the rotor 30 of the motor 12 by a desired rotation angle by a desired torque. The rotation of the rotor 30 is reduced at a predetermined reduction ratio by the multi-axis reduction mechanism 14 and the planetary gear reduction mechanism 15, converted into a linear motion by the ball screw mechanism 13, and transmitted to the piston 11. As a result, the piston 11 moves forward (promotes) and presses the inner pad 4 against the disc rotor 1. On the other hand, the caliper body 10 is moved (retracted) along the slide pin 5 of the carrier 2 by the reaction force at that time, and the claw portion 23 of the caliper body 10 presses the outer brake pad 3 against the disc rotor 1, thereby the motor. A desired braking force corresponding to the torque of 12 is generated. Further, when the brake is released, the rotor 30 of the motor 12 is rotationally driven in the opposite direction to that during the braking, and the piston 11 moves backward by the motion conversion by the ball screw mechanism 13, whereby the brake pads 3 and 4 are separated from the disk rotor 1. Then, braking is released.

  The in-vehicle controller determines the vehicle state based on the detection values taken from various sensors, for example, the rotational speed of each wheel, the vehicle speed, the vehicle acceleration, the steering angle, the vehicle lateral acceleration, etc., and controls the rotation of the motor 12. By the boost control. Automatic brake control such as unlock control, traction control, and vehicle stabilization control is executed.

  When operating the parking brake, the drive controller 17 energizes the solenoid 72 of the parking brake mechanism 13 from the state shown in FIG. 7 (the state where no thrust is generated in the piston 11). Then, as shown in FIG. 8, the plunger 78 extends, the ratchet lever 71 tilts, and the engagement protrusion 71a at the tip thereof enters between the teeth 73 of the ratchet 70. At the same time, the gear lever 64 also swings. Thus, the hook portion 64 a at the tip is detached from the engagement hole 62 of the projecting piece 56 of the internal gear 55.

  Under the above-described state, the rotor 30 of the motor 12 is rotated by a command from the drive control device 17. At this time, depending on the initial rotation position of the rotor 30, the engagement protrusion 71 a of the ratchet lever 71 may not be able to enter between the teeth 73 of the ratchet 70. It smoothly enters between the teeth 73. Then, as shown in FIG. 9, the rotation of the rotor 30 causes the engagement protrusion 71a of the ratchet lever 71 to slide on the inclined relief surface 73a and get over the teeth 73, thereby allowing the rotation of the first shaft 40. Is done. When the engaging protrusion 71a gets over the teeth 73, the ratchet lever 71 is tilted away from the plunger 78 of the solenoid 72 as shown in FIG.

  On the other hand, when the torque applied to the internal gear 55 exceeds the set torque of the torsion spring 60 engaged with the internal gear 55, the internal gear 55 moves in the clockwise direction of FIG. 1 (the direction in which the piston thrust is reduced). Start spinning. The rotation of the internal gear 55 continues until the other end 56b of the projecting piece 56 abuts against the stopper surface 58 on the other end of the moving path 59. During this time, the torsion spring 60 has a force in the piston propulsion direction. Is stored. In the present embodiment, the rotation of the rotor 30 of the motor 12 is stopped when the projecting piece 56 of the internal gear 55 comes into contact with the stopper surface 58 on the other end side of the moving path 59, whereby the brake pads 3, 4 Piston pressing force (piston thrust) with a size that allows for the thermal expansion of is secured. This will be described in detail later.

  Next, the current to the motor 12 is decreased while the energization to the solenoid 72 is continued. Then, the first shaft 40 is slightly rotated in the braking release direction by the reaction force from the piston 11, whereby the engagement protrusion 71 a at the tip of the ratchet lever 71 is moved to the teeth 73 of the ratchet 70 as shown in FIG. 10. Engages with the recess 73b. Subsequently, the current supply to the motor 12 is interrupted, and the energization to the solenoid 72 is stopped. Then, the ratchet lever 71 tries to return to the standby state shown in FIG. 7 by the urging force of the torsion spring 76. However, since the engaging protrusion 71a is locked by the recess 73b of the tooth 73, the ratchet lever 71 maintains the state shown in FIG. 10, thereby rotating the first shaft 40, that is, the rotor 30 of the motor 12. Is prevented and the parking brake is established. On the other hand, when the energization of the solenoid 72 is stopped, the gear lever 64 receives the urging force of the urging means 65 and returns to the initial state shown in FIG. 7, but at this time, the projecting piece 56 of the internal gear 55 moves toward the moving path 59. Since it is displaced to the stopper surface 58 side, it is positioned outside the protruding piece 56 of the hook portion 64a at the tip of the gear lever 64 as shown in FIG.

  During the parking brake described above, the brake pads 3 and 4 are contracted due to a temperature drop, and the pressing force of the piston 11 is reduced. At this time, the internal gear 55 rotates in the braking direction by the force stored in the torsion spring 60 when the parking brake is operated, and the projecting piece 56 of the internal gear 55 returns to the original position. Thus, the original position of the internal gear 56 is a position for maintaining a desired piston thrust (braking force) required at the time of parking brake, so that the parking brake is not loosened. On the other hand, during the return of the internal gear 55, the gear lever 64 is pushed up by the projecting piece 56 against the urging force of the urging means 65, and finally the hook portion 56 a is engaged with the engagement hole 62 of the projecting piece 56. Returning to the original state (the state shown in FIG. 7), the internal gear 55 is fixed in position.

  When releasing the parking brake, the rotor 30 of the motor 12 is slightly rotated in the braking direction. Then, the engagement protrusion 71a at the tip of the ratchet lever 71 is disengaged from the recess 73b of the tooth 73 of the ratchet 70, and the ratchet lever 71 returns to the standby state shown in FIG. Thereafter, the rotor 30 of the motor 12 is rotated in the braking release direction, the piston 11 is retracted by the motion conversion by the ball screw mechanism 13, and the brake pads 3 and 4 are separated from the disc rotor 1, thereby releasing the parking brake. . When the parking brake is released, when the internal gear 55 is in a rotational position where the projecting piece 56 is in contact with the stopper surface 58, the internal gear 55 is rotated according to the rotation of the rotor 30 in the braking release direction. Returns to the original position and is fixed again by the gear lever 64.

  FIG. 11 shows the relationship between the propulsion position (piston position) of the piston 11 and the pressing force (piston thrust) of the piston 11 during the normal braking and parking brake (PKB) described above. Line A indicates normal braking and line B indicates PKB. Thus, during normal braking, the piston thrust increases almost linearly as the piston position increases. On the other hand, at the time of PKB, the piston thrust increases along the same line A as during normal braking until the piston position P1 at which the internal gear 55 begins to rotate, but when the internal gear 55 begins to rotate, the piston thrust increases. The rising gradient of the internal gear 55 becomes gentle, and this tendency continues until the piston position P2 where the projecting piece 56 of the internal gear 55 abuts against the stopper surface 58 (FIG. 1) on the other end side of the moving path 59 and stops moving. After the internal gear 55 stops moving, the piston thrust increases again with the same gradient as during normal braking.

  In FIG. 11, the piston position P <b> 1 is determined by the magnitude of the set torque of the torsion spring 60 acting on the internal gear 55, and the piston position P <b> 2 is the movement of the projecting piece 56 of the internal gear 55 within the moving path 59. Determined by range. The magnitude of the piston thrust F1 corresponding to the piston position P2 is determined by the spring constant of the torsion spring 60.

  Here, the minimum required piston thrust during PKB not considering the thermal expansion of the brake pads 3 and 4 is F0, and the thermal expansion of the brake pads 3 and 4 is made equal to the difference between the piston positions P2 and P1. Think about the case. At this time, if it is intended to obtain the necessary piston thrust (without unclamping) in consideration of the thermal expansion of the brake pads 3 and 4, the electric disk brake according to the prior art requires the piston thrust of F2. However, in this embodiment, since the increasing tendency of the piston thrust is moderate between the P1 position where the internal gear 55 starts to rotate and the P2 position where rotation stops as described above, F1 which is much lower than F2 The piston thrust is sufficient.

  That is, according to the electric disc brake according to the present invention, the piston thrust does not increase so much even if the parking brake is applied in anticipation of the thermal expansion of the brake pads 3 and 4 during the parking brake. There is no need to raise the special. This means that it is advantageous in terms of size and weight, and is much smaller and lighter than the conventional electric disc brake when the pressing force for the thermal expansion of the brake pads 3 and 4 is expected. Can be achieved. Further, since reclamping is not performed, power consumption can be reduced, and the control unit is simplified and the reliability of the apparatus is improved. Further, during normal braking, the position of the internal gear 55 is fixed and the relationship between the piston position and the piston thrust similar to that of the electric disk brake of the prior art is maintained, so that the minimum piston thrust F0 required for the parking brake is maintained. The responsiveness described above is not impaired, and the reliability is also improved in this aspect.

  In the above-described embodiment, the so-called 2K-H-1 type planetary gear reduction mechanism 15 is used as the reduction mechanism composed of three basic shafts. Instead, other types of planetary gear mechanisms and ball reduction gears are used. A known speed reduction mechanism such as a mechanism, a cycloid speed reduction mechanism, or a wave speed reduction mechanism may be used.

  In the above embodiment, the torsion spring 60 is used as a spring means for applying a biasing force to the internal gear 55, instead of this. A compression spring may be attached to the projecting piece 56 of the internal gear 55.

FIG. 4 is a cross-sectional view showing the overall structure of the electric disc brake according to the present invention, taken along the line XX in FIG. 3. FIG. 7 is a cross-sectional view taken along the line YY of FIG. 6, showing the overall structure of the electric disk brake. FIG. 7 is a cross-sectional view taken along the line ZZ in FIG. 6, showing the overall structure of the electric disk brake. It is a front view which shows the whole structure of this electric disc brake. It is a top view which shows the whole structure of this electric disc brake. It is a rear view which shows the whole structure of this electric disc brake. The structure of the parking brake mechanism in this electric disc brake and the peripheral elements related thereto are schematically shown. (A) is a plan view showing a partial cross section, (B) is a front view, and (C) is a front view. It is a side view shown as a partial cross section. The operation state of the parking brake mechanism and related peripheral elements in this electric disk brake is schematically shown, (A) is a plan view showing a partial cross section, (B) is a front view, and (C). FIG. 3 is a side view showing a partial cross section. The operation state of the parking brake mechanism and related peripheral elements in this electric disk brake is schematically shown, (A) is a plan view showing a partial cross section, (B) is a front view, and (C). FIG. The operation state of the parking brake mechanism and related peripheral elements in this electric disk brake is schematically shown, (A) is a plan view showing a partial cross section, (B) is a front view, and (C). FIG. 3 is a side view showing a partial cross section. It is a graph which shows the braking characteristics of this electric disc brake.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Disc rotor, 2 Carrier 3, 4 Brake pad, 6 Electric caliper 10 Caliper main body, 11 Piston 12 Motor, 29 Motor stator, 30 Motor rotor 13 Ball ramp mechanism (rotation-linear motion conversion mechanism)
15 Planetary gear reduction mechanism (reduction mechanism consisting of three basic shafts)
55 Internal gear (third shaft)
56 Projection piece of internal gear 59 Movement path of projection piece 60 Torsion spring (spring means)
64 Gear lever (locking means)
70 Ratchet (parking brake mechanism)
71 Ratchet lever (parking brake mechanism)
72 Solenoid (drive source for parking brake mechanism)

Claims (5)

  A piston that presses the brake pad, a motor, a rotation-linear motion conversion mechanism that converts the rotation of the motor into a linear motion and transmits the linear motion to the piston, and locks and unlocks the rotation of the motor in the braking release direction. A lockable parking brake mechanism, propelling the piston according to rotation of the rotor of the motor, pressing a brake pad against a disc rotor to generate a braking force, and the parking brake mechanism to rotate the rotor of the motor In the electric disc brake that holds the motor at the braking position, a speed reduction mechanism including three basic shafts is provided between the motor and the rotation-linear motion conversion mechanism, and the motor and the rotation-linear motion of the speed reduction mechanism are provided. The third shaft, which is free with respect to both of the conversion mechanisms, can be rotated within a predetermined range, and before the parking brake mechanism is operated. Electric disc brake, characterized in that a spring means for storing the power of piston propulsion direction according to the rotation of the shaft of the engaging third the third axis.   2. The electric disc brake according to claim 1, wherein the spring means is a torsion spring disposed with a set torque.   The electric disk brake according to claim 1 or 2, wherein the speed reduction mechanism including the three basic shafts is a planetary gear speed reduction mechanism.   The electric disc brake according to any one of claims 1 to 3, further comprising a locking unit that locks and unlocks the third shaft in conjunction with an operation of the parking brake mechanism.   The electric disk brake according to claim 4, wherein the parking brake mechanism operates using a solenoid as a drive source, and the solenoid is shared as a drive source of the locking means.

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