JP2018099985A - Vehicular brake - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vehicular brake in which brake torque in the brake state can be set smaller under such a condition that the displacement amount of a linear motion member corresponding to the drive current becomes the largest, for example, in the vehicular brake stopping a motor on the basis of the drive current of the motor.SOLUTION: A vehicular brake, for example, includes a control unit which stops a motor on the basis of the change rate of the current value of the motor. In such a state that a linear motion member is arranged at the release position, an elastic member is in the free state. The linear motion member starts compression of the elastic member between a housing and itself before it reaches the brake position and compresses the elastic member until it reaches the brake position when heading from the release position to the brake position.SELECTED DRAWING: Figure 9

Description

  The present disclosure relates to a vehicle brake.

  2. Description of the Related Art Conventionally, a vehicular brake that obtains a braking state by converting the rotation of a motor into a linear motion of a cable in a motion conversion mechanism and moving a brake shoe with the linearly moving cable is known (for example, Patent Document 1). In Patent Document 1, for example, the disc spring is compressed between the rotating member of the motion conversion mechanism and the housing, so that the rotational load of the motor is increased. In this case, the control device can detect, for example, that the linear motion member and the cable are at a predetermined position, for example, the boundary position of the movable range, by the drive current corresponding to the rotational load of the motor.

Special table 2014-504711 gazette

  In the braking control based on the detection of the driving current of the motor, the amount of displacement of the linear motion member corresponding to a predetermined threshold of the driving current, that is, the brake is taken into consideration that the amount of displacement of the linear motion member with respect to the driving current varies depending on environmental conditions. The drive current threshold is set so that the brake torque necessary to maintain the stop of the vehicle can be obtained even under the condition where the torque is the smallest.

  However, in that case, under the condition that the displacement amount of the linear motion member corresponding to the predetermined threshold value of the drive current becomes the largest, the brake torque that greatly exceeds the brake torque necessary to maintain the stop of the vehicle acts. For example, it may be necessary to wastefully increase the rigidity and strength of the brake device.

  Accordingly, one of the problems of the present invention is that, for example, in a vehicle brake that stops the motor based on the drive current of the motor, even in a condition where the amount of displacement of the linear motion member corresponding to the drive current is the largest, the braking state Is to obtain a vehicle brake capable of setting a smaller brake torque.

  The vehicle brake of the present disclosure is connected to, for example, a housing, a motor, a rotating member that is accommodated in the housing and rotated by the motor, and a braking member that is accommodated in the housing and brakes the wheel. As the rotating member rotates, the brake member linearly moves between a braking position at which the braking member brakes the wheel and a release position at which the braking member releases the wheel braking. Based on a moving member, an elastic member that applies elastic force to the linear motion member by elastic expansion and contraction according to the movement of the linear motion member, and changes the rotational load of the motor, and a rate of change in the current value of the motor A controller that stops the motor, and the elastic member is in a free state when the linear motion member is disposed at the release position, and the linear motion member is at the release position. If toward the braking position, between said housing before reaching the braking position to start the compression of the elastic member compressing said elastic member to reaching the braking position.

  In the vehicle brake, the linear motion member starts compression of the elastic member with the housing before reaching the braking position from the release position. Before and after the start of compression, the rate of change of the elastic repulsion force applied from the elastic member to the linear motion member, and hence the rate of change of the drive current of the motor changes. Further, the position at which the compression of the elastic member is started does not depend on the change in the displacement amount of the linear motion member with respect to the drive current. Therefore, the control unit stops the linear motion member at a position near the predetermined position regardless of the change in the displacement amount of the linear motion member with respect to the drive current by stopping the motor based on the rate of change in the current value of the motor. can do. Therefore, even under the condition that the displacement amount of the linear motion member corresponding to the drive current is the largest, the brake torque in the braking state can be set smaller.

  In the vehicle brake, for example, one end of the elastic member is fixed to one of the housing and the linear motion member, and the other end of the elastic member is releasably connected to the other of the housing and the linear motion member. The other end is connected to the other in a tensioned state within a predetermined length of the elastic member, and the other member is disconnected from the other in a tensioned state exceeding the predetermined length. When the elastic member moves from the braking position to the release position, the elastic member is pulled between the housing and the elastic member exceeds the predetermined length before the linear motion member reaches the release position. Thus, the connection between the other end and the other of the housing and the linear motion member is released. Therefore, for example, since the load torque of the motor at the time of entering the release state is reduced, it is possible to reduce the load torque of the motor when starting the rotation of the motor from the release state.

  In the vehicle brake, for example, the other end and the other of the housing and the linear motion member are connected by magnetic force. Therefore, for example, the releasable connection structure between the other end and the other can be realized as a relatively simple configuration with a magnet.

  In the vehicle brake, for example, the connected state and the separated state of the other end and the other are switched with elastic deformation of at least one of the other end and the other of the housing and the linear motion member. Composed. Therefore, for example, the releasable connection structure between the other end and the other can be realized as a relatively simple configuration by a configuration involving elastic deformation.

FIG. 1 is an exemplary and schematic rear view of a vehicle brake according to an embodiment from the rear of the vehicle. FIG. 2 is an exemplary schematic side view of the vehicle brake according to the embodiment from the outside in the vehicle width direction. FIG. 3 is an exemplary schematic side view of the operation of the braking member by the vehicle brake moving mechanism of the embodiment, and is a diagram in a released state. FIG. 4 is an exemplary and schematic side view of the operation of the braking member by the vehicle brake moving mechanism of the embodiment, and is a diagram in a braking state. FIG. 5 is an exemplary and schematic cross-sectional view of the drive mechanism included in the vehicle brake of the first embodiment, and is a diagram in a released state. FIG. 6 is an exemplary schematic sectional view of a drive mechanism included in the vehicle brake according to the first embodiment, and is a diagram in a braking state. FIG. 7 is an exemplary schematic cross-sectional view of the drive mechanism included in the vehicle brake according to the first embodiment, and the compression of the elastic member is started when the linear motion member moves from the release position to the braking position. FIG. FIG. 8 is an exemplary schematic cross-sectional view of a drive mechanism included in the vehicle brake according to the first embodiment. When the linear motion member moves from the braking position to the release position, the elastic member is a linear motion member. It is a figure which shows the state pulled between housings. FIG. 9 is an exemplary and schematic graph showing changes over time in the brake torque and the motor drive current value when shifting from the vehicle brake release state to the braking state of the first embodiment. FIG. 10 is an exemplary schematic graph showing a change over time in the drive current value of the motor when the vehicle brake according to the first embodiment shifts from the braking state to the released state. FIG. 11 is an exemplary schematic cross-sectional view of a drive mechanism included in the vehicle brake of the second embodiment. FIG. 12 is an exemplary schematic cross-sectional view of a drive mechanism included in a vehicle brake according to a modification. FIG. 13 is an exemplary and schematic cross-sectional view of a drive mechanism included in a vehicle brake according to a modified example different from FIGS.

  Hereinafter, exemplary embodiments of the present invention are disclosed. The configuration of the embodiment shown below, and the operation and result (effect) brought about by the configuration are examples. The present invention can be realized by configurations other than those disclosed in the following embodiments. According to the present invention, it is possible to obtain at least one of various effects (including derivative effects) obtained by the configuration.

  The following embodiments and modifications include similar components. Therefore, in the following, the same reference numerals are given to the same components, and redundant description may be omitted. Moreover, in this specification, the ordinal number is given for convenience in order to distinguish parts, parts, and the like, and does not indicate priority or order.

  1 to 4, for the sake of convenience, the front in the vehicle front-rear direction is indicated by an arrow X, the outer side in the vehicle width direction (axle direction) is indicated by an arrow Y, and the upper side in the vehicle vertical direction is indicated by an arrow Z. .

  In the following, a case where the brake device 2 which is an example of a vehicle brake is applied to the left rear wheel (non-drive wheel) will be exemplified, but the present invention can be similarly applied to other wheels. It is.

(First embodiment)
(Brake device configuration)
FIG. 1 is a rear view of the brake device 2 from the rear of the vehicle. FIG. 2 is a side view of the brake device 2 from the outside in the vehicle width direction. FIG. 3 is a side view showing the operation of the brake shoe 3 (braking member) by the moving mechanism 8 of the brake device 2, and is a view in a released state (non-braking state). FIG. 4 is a side view showing the operation of the brake shoe 3 by the moving mechanism 8 of the brake device 2 and is a diagram in a braking state.

  As shown in FIG. 1, the brake device 2 is accommodated inside the peripheral wall 1 a of the cylindrical wheel 1. The brake device 2 is a so-called drum brake. As shown in FIG. 2, the brake device 2 includes two brake shoes 3 that are separated from each other in the front-rear direction. As shown in FIGS. 3 and 4, the two brake shoes 3 extend in an arc shape along the inner peripheral surface 4 a of the cylindrical drum 4. The drum 4 rotates integrally with the wheel 1 around the rotation center C along the vehicle width direction (Y direction). The brake device 2 moves the two brake shoes 3 so as to contact the inner peripheral surface 4 a of the cylindrical drum 4. Thereby, the drum 4 and the wheel 1 are braked by the friction between the brake shoe 3 and the drum 4. The brake shoe 3 is an example of a braking member.

  The brake device 2 includes a wheel cylinder 51 (see FIG. 2) that operates by hydraulic pressure, and a motor 120 (see FIG. 5) that operates by energization as an actuator that moves the brake shoe 3. Each of the wheel cylinder 51 and the motor 120 can move the two brake shoes 3. The wheel cylinder 51 is used, for example, for braking while traveling, and the motor 120 is used, for example, for braking during parking. That is, the brake device 2 is an example of an electric parking brake. The motor 120 may be used for braking during traveling.

  As shown in FIGS. 1 and 2, the brake device 2 includes a disk-shaped back plate 6. The back plate 6 is provided in a posture intersecting with the rotation center C. That is, the back plate 6 extends substantially along the direction intersecting the rotation center C, specifically, substantially along the direction orthogonal to the rotation center C. As shown in FIG. 1, the components of the brake device 2 are provided on both the outer side and the inner side of the back plate 6 in the vehicle width direction. The back plate 6 supports each component of the brake device 2 directly or indirectly. That is, the back plate 6 is an example of a support member. The back plate 6 is connected to a connection member (not shown) with the vehicle body. The connection member is, for example, a part of the suspension (for example, an arm, a link, an attachment member, etc.). The opening 6b provided in the back plate 6 shown in FIG. 2 is used for coupling with the connection member. The brake device 2 can be used for both driving wheels and non-driving wheels. When the brake device 2 is used for driving wheels, an axle shaft (not shown) passes through an opening 6c provided in the back plate 6 shown in FIG.

<Brake shoe operation by wheel cylinder>
The wheel cylinder 51 and the brake shoe 3 shown in FIG. 2 are arranged on the outer side of the back plate 6 in the vehicle width direction. The brake shoe 3 is movably supported on the back plate 6. Specifically, as shown in FIG. 3, the lower end 3a of the brake shoe 3 is supported by the back plate 6 (see FIG. 2) so as to be rotatable around the rotation center C11. The rotation center C11 is substantially parallel to the rotation center C of the wheel 1. Further, as shown in FIG. 2, the wheel cylinder 51 is supported by the upper end portion of the back plate 6. The wheel cylinder 51 has two movable parts (pistons) (not shown) that can project in the vehicle front-rear direction (left-right direction in FIG. 2). The wheel cylinder 51 causes the two movable parts to protrude in response to the pressurization. The two projecting movable parts push the upper end 3b of the brake shoe 3, respectively. Due to the protrusion of the two movable parts, the two brake shoes 3 rotate around the rotation center C11 (see FIGS. 3 and 4) and move so that the upper end parts 3b are separated from each other in the vehicle front-rear direction. As a result, the two brake shoes 3 move outward in the radial direction of the rotation center C of the wheel 1. A belt-like lining 31 along the cylindrical surface is provided on the outer periphery of each brake shoe 3. Therefore, the lining 31 and the inner peripheral surface 4a of the drum 4 come into contact with each other as shown in FIG. The drum 4 and thus the wheel 1 (see FIG. 1) are braked by the friction between the lining 31 and the inner peripheral surface 4a. As shown in FIG. 2, the brake device 2 includes a return member 32. When the operation of pushing the brake shoe 3 by the wheel cylinder 51 is released, the return member 32 moves from the position where the two brake shoes 3 come into contact with the inner peripheral surface 4a of the drum 4 (braking position Pb, see FIG. 4). The drum 4 is moved to a position not in contact with the inner peripheral surface 4a (non-braking position Pn, release position, initial position, see FIG. 3). The return member 32 is an elastic member such as a coil spring, for example, and gives each brake shoe 3 a force in a direction approaching the other brake shoe 3, that is, a force in a direction away from the inner peripheral surface 4 a of the drum 4. .

(Configuration of moving mechanism and operation of brake shoe by moving mechanism)
Moreover, the brake device 2 includes a moving mechanism 8 shown in FIGS. The moving mechanism 8 moves the two brake shoes 3 from the non-braking position Pn to the braking position Pb based on the operation of the driving mechanism 100 including the motor 120 (see FIG. 5). The moving mechanism 8 is provided outside the back plate 6 in the vehicle width direction. The moving mechanism 8 includes a lever 81, a cable 82, and a strut 83. The lever 81 is located between one of the two brake shoes 3, for example, the left brake shoe 3 </ b> L in FIGS. 3 and 4, and the back plate 6. It is provided so as to overlap in the axial direction. The lever 81 is supported by the brake shoe 3L so as to be rotatable around the rotation center C12. The rotation center C12 is located at the end of the brake shoe 3L on the side away from the rotation center C11 (upper side in FIGS. 3 and 4), and is substantially parallel to the rotation center C11. The cable 82 moves the lower end portion 81a of the lever 81 on the side farther from the rotation center C12, for example, in a direction approaching the right brake shoe 3R in FIGS. The cable 82 moves substantially along the back plate 6. The strut 83 is interposed between the lever 81 and the brake shoe 3R different from the brake shoe 3L on which the lever 81 is supported, and stretches between the lever 81 and the other brake shoe 3R. The connection position P1 between the lever 81 and the strut 83 is set between the rotation center C12 and the connection position P2 between the cable 82 and the lever 81. The cable 82 is an example of an operating member that moves the brake shoe 3.

  In such a moving mechanism 8, when the cable 82 is pulled and moves to the right in FIG. 4, when the lever 81 moves in a direction approaching the brake shoe 3 </ b> R (arrow a), the lever 81 passes through the strut 83. Press the brake shoe 3R (arrow b). As a result, the brake shoe 3R rotates around the rotation center C11 from the non-braking position Pn (FIG. 3) (arrow c in FIG. 4) and moves to the braking position Pb (FIG. 4) in contact with the inner peripheral surface 4a of the drum 4. Move. In this state, the connection position P2 between the cable 82 and the lever 81 corresponds to the power point, the rotation center C12 corresponds to the fulcrum, and the connection position P1 between the lever 81 and the strut 83 corresponds to the action point. Furthermore, when the brake shoe 3R is in contact with the inner peripheral surface 4a and the lever 81 moves to the right in FIG. 4, that is, in the direction in which the strut 83 pushes the brake shoe 3R (arrow b), the strut 83 is stretched. Accordingly, the lever 81 rotates in the direction opposite to the direction in which the lever 81 moves, that is, counterclockwise in FIGS. 3 and 4 with the connection position P1 with the strut 83 as a fulcrum (arrow d). Thereby, the brake shoe 3L rotates around the rotation center C11 from the non-braking position Pn (FIG. 3) and moves to the braking position Pb (FIG. 4) in contact with the inner peripheral surface 4a of the drum 4. Thus, the brake shoes 3L and 3R are both moved from the non-braking position Pn (FIG. 3) to the braking position Pb (FIG. 4) by the operation of the moving mechanism 8. In the state after the brake shoe 3R contacts the inner peripheral surface 4a of the drum 4, the connection position P1 between the lever 81 and the strut 83 serves as a fulcrum. The amount of movement of the brake shoes 3L, 3R is very small, for example, 1 mm or less.

(Drive mechanism)
FIG. 5 is a cross-sectional view of the driving mechanism 100 in a released state. FIG. 6 is a cross-sectional view of the driving mechanism 100 in a braking state.

  The drive mechanism 100 shown in FIGS. 1, 5 and 6 moves the two brake shoes 3 from the non-braking position Pn (release position) to the braking position Pb via the moving mechanism 8 described above. The drive mechanism 100 is positioned inward in the vehicle width direction of the back plate 6 and is fixed to the back plate 6. The cable 82 shown in FIGS. 2 to 4 passes through an opening (not shown) provided in the back plate 6.

  As shown in FIG. 5, the drive mechanism 100 includes a housing 110, a motor 120, a speed reduction mechanism 130, and a motion conversion mechanism 140.

  The housing 110 supports the motor 120, the speed reduction mechanism 130, and the motion conversion mechanism 140. The housing 110 includes a plurality of members. The plurality of members are coupled and integrated by a coupling tool (not shown) such as a screw. A housing chamber R surrounded by a wall 111 is provided in the housing 110. The motor 120, the speed reduction mechanism 130, and the motion conversion mechanism 140 are accommodated in the accommodation chamber R and covered with the wall portion 111. The housing 110 may be referred to as a base, a support member, a casing, or the like. In addition, the structure of the housing 110 is not limited to what was illustrated here.

  The motor 120 is an example of an actuator, and includes a housing 121 and a housing component housed in the housing 121. The housing components include, for example, a stator, a rotor, a coil, and a magnet (not shown) in addition to the shaft 122. The shaft 122 protrudes from the housing 121 in the D1 direction (rightward in FIG. 5) along the first rotation center Ax1 of the motor 120. The motor 120 is driven by driving power based on the control signal, and rotates the shaft 122. The shaft 122 may be referred to as an output shaft. In the following, for convenience of explanation, the right side in FIG. 5 is referred to as the front in the D1 direction, and the left side in FIG. 5 is referred to as the rear in the D1 direction or the opposite direction to the D1 direction.

  Deceleration mechanism 130 includes a plurality of gears rotatably supported by housing 110. The plurality of gears are, for example, a first gear 131, a second gear 132, and a third gear 133. Deceleration mechanism 130 can be referred to as a rotation transmission mechanism.

  The first gear 131 rotates integrally with the shaft 122 of the motor 120. The first gear 131 can be referred to as a drive gear.

  The second gear 132 rotates around a second rotation center Ax2 parallel to the first rotation center Ax1. The second gear 132 includes an input gear 132a and an output gear 132b. The input gear 132a meshes with the first gear 131. The number of teeth of the input gear 132a is larger than the number of teeth of the first gear 131. Therefore, the second gear 132 is decelerated to a lower rotational speed than the first gear 131. The output gear 132b is located behind the input gear 132a in the direction D1 (leftward in FIG. 5). The second gear 132 can be referred to as an idler gear.

  The third gear 133 rotates around a third rotation center Ax3 that is parallel to the first rotation center Ax1. The third gear 133 meshes with the output gear 132b of the second gear 132. The number of teeth of the third gear 133 is larger than the number of teeth of the output gear 132b. Therefore, the third gear 133 is decelerated to a lower rotational speed than the second gear 132. The third gear 133 can be referred to as a driven gear. Note that the configuration of the speed reduction mechanism 130 is not limited to that illustrated here. The speed reduction mechanism 130 may be a rotation transmission mechanism other than a gear mechanism, such as a rotation transmission mechanism using a belt, a pulley, or the like.

  The motion conversion mechanism 140 includes a rotating member 141 and a linear motion member 142.

  The rotating member 141 rotates around the third rotation center Ax3. The rotating member 141 includes a hub 141a, a flange 141e projecting radially outward from the hub 141a, and a peripheral wall 141d extending in the axial direction from the flange 141e. The hub 141a is configured in a cylindrical shape extending in the D1 direction, and penetrates the flange 141e in the D1 direction. The flange 141e protrudes in a disk shape from the center position in the D1 direction of the hub 141a in the radial direction of the third rotation center Ax3. The peripheral wall 141d extends in a cylindrical shape in the D1 direction from the outer edge of the flange 141e.

  The teeth of the third gear 133 are provided on the outer periphery of the peripheral wall 141d. That is, the rotating member 141 is also the third gear 133. By providing the third gear 133 on the peripheral wall 141d extending in the axial direction, the surface pressure of the output gear 132b of the third gear 133 and the second gear 132 can be reduced. The part where the teeth of the third gear 133 are provided is an example of a driven part.

  At least the teeth or all of the first gear 131, the second gear 132, and the third gear 133 can be made of a synthetic resin material. However, the present invention is not limited to this, and at least one of the first gear 131, the second gear 132, and the third gear 133 may be partially or entirely made of a metal material.

  A thrust bearing 143 is positioned between the front end surface of the flange 141e in the D1 direction and the rear end portion 112a of the cylindrical portion 112 provided in the housing 110 in the D1 direction. The thrust bearing 143 receives a load in the axial direction of the third rotation center Ax3. The thrust bearing 143 is a thrust roller bearing in the example of FIG. 5, but is not limited to this. The flange 141e and thus the rotating member 141 are rotatably supported by the housing 110 via a thrust bearing 143.

  The hub 141 a is inserted into a cylindrical radial bearing 144 housed at the tip of the cylindrical portion 112. The hub 141a and the rotating member 141 are rotatably supported by the housing 110 via a radial bearing 144. Although the radial bearing 144 is a metal bush in the example of FIG. 5, it is not limited to this.

  The rotating member 141 is provided with a through hole 141c having a circular cross section that passes through the hub 141a and the flange 141e. A female screw part 145a is provided in the through hole 141c.

  The linear motion member 142 extends along the third rotational center Ax3 and penetrates the rotational member 141. The linear motion member 142 includes a rod-like portion 142a, a connecting portion 142b, and a flange 142c.

  The rod-like portion 142 a is inserted into the first hole 113 a of the housing 110, the through hole 141 c of the rotating member 141, and the second hole 113 b provided in the cylindrical portion 112 of the housing 110. The cross section of the second hole 113b is substantially circular. The second hole 113b is positioned in front of the direction D1 with respect to the first hole 113a, and extends along the axial direction of the third rotation center Ax3. The rod-like portion 142a has a substantially circular cross section. The rod-like portion 142 a is provided with a male screw portion 145 b that meshes with the female screw portion 145 a of the rotating member 141.

  The cylindrical portion 112 is provided with a cylindrical inner surface 113c facing the second hole 113b. The cross section of the inner surface 113c has a shape along the long hole cross section of the second hole 113b. The inner surface 113c has two planar guide surfaces 113ca (only one guide surface 113ca is shown in FIG. 5) extending in a direction orthogonal to the third rotation center Ax3. The two guide surfaces 113ca are positioned with a space therebetween, and the linear motion member 142 is positioned between the two guide surfaces 113ca. On the other hand, a flange 142c protrudes from the rod-like portion 142a of the linear motion member 142 toward the outside in the radial direction of the third rotation center Ax3. The outer periphery of the flange 142c is formed in a shape along the inner surface 113c. A gap is provided between the flange 142c and the inner surface 113c, and grease is provided in the gap. When the flange 142c and the guide surface 113ca are in contact with each other, the rotation of the flange 142c and thus the linear motion member 142 around the third rotation center Ax3 is limited. Further, in a state where the flange 142c and the guide surface 113ca are in contact with each other, the guide surface 113ca guides the flange 142c and thus the linear motion member 142 in the axial direction of the third rotation center Ax3.

  In such a configuration, the rotation of the shaft 122 of the motor 120 is transmitted to the rotating member 141 via the speed reduction mechanism 130, and when the rotating member 141 rotates, the female screw portion 145 a of the rotating member 141 and the male screw portion of the linear motion member 142. Due to the meshing with 145b and the limitation on the rotation of the linear motion member 142 by the guide surface 113ca, the linear motion member 142 moves along the axial direction of the third rotation center Ax3 with the non-braking position Pn (FIG. 5) and the braking position ( (Not shown).

(Stop control of linear motion member)
When the movement resistance of the linear motion member 142 increases due to a mechanical restriction of the movement of the linear motion member 142 while the linear motion member 142 is moving forward or backward in the D1 direction by the rotation of the motor 120. The rotation of the rotating member 141 is limited, and consequently the load torque of the motor 120 increases.

  On the other hand, when the linear movement member 142 is moved forward or backward in the D1 direction by the rotation of the motor 120, the movement of the linear movement member 142 is canceled by, for example, releasing the mechanical restriction on the movement of the linear movement member 142. When the resistance decreases, the limitation on the rotation of the rotating member 141 is released, and as a result, the load torque of the motor 120 decreases.

  Further, the load torque of the motor 120 can be detected by a current (drive current) applied to the motor 120.

  Therefore, in the present embodiment, the drive mechanism 100 causes the current of the motor 120 to change according to the position of the linear motion member 142 so that the resistance force acting on the linear motion member 142 changes according to the position of the linear motion member 142. Configured to change value. Accordingly, the control unit 123 can control the linear motion member 142 to stop at a predetermined position by executing stop control based on the current value of the motor 120 or a change in the current value. Here, the change of the current value is, for example, a time change rate of the current value, a time differentiation of the current value, a history of the current value, or a change rate of the current value with respect to the displacement of the linear motion member 142.

(Mechanism to change the load torque of the motor)
As shown in FIG. 5, an inward flange 112 b protrudes from the cylindrical portion 112 of the housing 110 inward in the radial direction of the third rotation center Ax3. The rod-like portion 142a of the linear motion member 142 passes through the opening (through hole) inside the flange 112b.

  A coil spring 151 is located in the cylindrical portion 112 between the flange 142 c of the linear motion member 142 and the flange 112 b of the housing 110. The winding center of the coil spring 151 is along the third rotation center Ax3, and the rod-like portion 142a passes through the coil of the coil spring 151. In other words, the coil spring 151 is formed in a spiral shape extending along the third rotation center Ax3, and is wound around the rod-shaped portion 142a with a gap. In the present embodiment, the drive mechanism 100 is configured such that the elastic force that acts on the linear motion member 142 from the coil spring 151 changes depending on the position of the linear motion member 142. The coil spring 151 is an example of an elastic member. The coil spring 151 can be referred to as a biasing member or a repulsion member. The elastic member is not limited to the coil spring 151, and may be an elastic member other than the coil spring, such as an elastomer. The flanges 112b and 142c may also be referred to as wall portions.

  As shown in FIG. 5, the first end portion 151a (front end) of the coil spring 151 is fixed to the flange 142c. The second end 151b and the flange 142c can be fixed by, for example, mechanical coupling or welding.

  As shown in FIG. 5, the second end portion 151b (rear end) of the coil spring 151 and the flange 112b are separated from each other in a state where the linear motion member 142 is located at the non-braking position Pn. That is, the length between the flange 142c and the flange 112b is longer than the length of the coil spring 151 in the free state Sf.

  FIG. 7 is a cross-sectional view of the drive mechanism 100, and shows a state in the middle of moving the linear motion member 142 from the non-braking position Pn toward the braking position Pb, and FIG. 8 is a cross-sectional view of the drive mechanism 100. The linear motion member 142 is a view in the middle of moving from the braking position Pb toward the non-braking position Pn. FIG. 9 is a diagram showing the relationship between the displacement of the linear motion member 142, the brake torque, and the drive current of the motor 120 when the linear motion member 142 moves from the non-braking position Pn toward the braking position Pb. FIG. 10 is a diagram illustrating a change with time of the drive current of the motor 120 when the linear motion member 142 moves from the braking position Pb toward the non-braking position Pn.

(Motor stop during braking)
As shown in FIG. 7, the second end portion 151b of the coil spring 151 in the free state contacts the flange 112b while the linear motion member 142 moves from the non-braking position Pn to the braking position Pb. The position of the linear motion member 142 in FIG. 7 can be referred to as a contact position Pc. The compression of the coil spring 151 starts when the linear motion member 142 reaches the contact position Pc, and the coil spring 151 thereafter moves, that is, the linear motion member 142 moves from the contact position Pc toward the braking position Pb. Until then, an elastic repulsion force (compression reaction force) in a direction away from each other is applied to the flange 112b and the flange 142c.

  In this case, before and after the linear motion member 142 reaches the contact position Pc, the axial force of the third rotation center Ax3 applied to the flange 142c, the movement resistance of the linear motion member 142, and the driving current of the motor 120 The rate of change changes. Specifically, the change rate of the drive current increases before and after reaching the contact position Pc.

  Therefore, as shown in FIG. 9, the control unit 123 controls the rotation of the motor 120 so that the linear motion member 142 moves from the non-braking position Pn toward the braking position Pb (in the moving rotation direction). The motor 120 is stopped using the detection of the sudden change Du (rapid increase) of the drive current as a trigger (first stop condition). Here, the sudden change Du of the drive current is a change rate of the drive current (for example, a time change rate of the current value, a time derivative of the current value, a history of the current value, or a change rate of the current value with respect to the displacement of the linear motion member 142. Etc.) is equal to or greater than a threshold value. Further, the control unit 123 stops the motor 120 with a trigger (second stop condition) that the drive current exceeds the threshold value Ith1. The control unit 123 stops the motor 120 when either one of the first stop condition and the second stop condition is satisfied.

  In the graph of the drive current in FIG. 9, the solid line indicates a case where the displacement amount of the linear motion member 142 with respect to the drive current becomes the largest in the range of variations due to individual differences of the drive mechanisms 100 and environmental conditions. In this case, the linear motion member 142 reaches the contact position Pc before the drive current reaches the threshold value Ith1, and a sudden change Du of the drive current appears. Therefore, the control unit 123 stops the motor 120 according to the first stop condition. The brake device 2 and the drive mechanism 100 are configured so that the brake torque Tb1 generated in the brake device 2 when the linear motion member 142 moves from the non-braking position Pn to the contact position Pc is equal to or higher than the necessary minimum brake torque. Yes.

  In the drive current graph of FIG. 9, the alternate long and short dash line indicates a case where the displacement amount of the linear motion member 142 with respect to the drive current is the smallest within the range of variations due to individual differences of the drive mechanisms 100 and environmental conditions. In this case, since the increase amount of the drive current per unit length of the displacement of the linear motion member 142 is relatively large, the sudden change Du of the drive current does not appear, that is, before the linear motion member 142 reaches the contact position Pc. In addition, the drive current reaches the threshold value Ith1. Therefore, the control unit 123 stops the motor 120 according to the second stop condition. The brake device 2 and the drive mechanism 100 are brakes that require a minimum brake torque Tb2 generated in the brake device 2 when the linear motion member 142 moves from the non-braking position Pn to a position (not shown) where the drive current becomes the threshold value Ith1. It is comprised so that it may become more than a torque. In FIG. 9, the brake torque Tb1 and the brake torque Tb2 are set to have substantially the same value, but the present invention is not limited to this.

  In the graph of FIG. 9, the broken line indicates that the motor 120 is triggered by the fact that the coil spring 151 is not compressed and the drive current reaches the threshold value Ith1 while the linear motion member 142 is moving from the non-braking position Pn to the braking position Pb. 6 shows the change with time of the drive current in the configuration in which is stopped (comparative example). As shown in FIG. 9, the brake torque Tb1 (Tb2) at the braking position Pb of the present embodiment is smaller by the difference ΔTb than the brake torque Tb0 at the braking position Pb of the comparative example. As described above, according to the present embodiment, for example, the brake torque in the braking state can be set smaller even under the condition that the displacement amount of the linear motion member 142 corresponding to the drive current is the largest.

  In the case of the solid line described above, the motor 120 is stopped by the second stop condition (the drive current has exceeded the threshold value Ith1) as a backup of the first stop condition or instead of the first stop condition. You may do it. According to this, the brake torque at the braking position Pb can be made smaller than in the case of the broken line described above (comparative example).

(Motor stop when releasing)
In the present embodiment, at least one of the second end 151b of the coil spring 151 and the flange 112b is magnetized, and the other is made of a magnetic material. That is, the second end 151b and the flange 112b are connected so as to be releasable (separable) by a magnetic force acting between them. Therefore, as shown in FIG. 8, the second end 151b and the flange 112b are coupled by magnetic force while the linear motion member 142 moves from the braking position Pb toward the non-braking position Pn, and the coil spring 151 is The flange 112b and the flange 142c are pulled beyond the free state Sf (see FIGS. 5 and 7) to become a tensile state Se. The position of the linear motion member 142 shown in FIG. 8 is the tension limit position Pe. That is, the coil spring 151 is pulled by the flanges 112b and 142c until the linear motion member 142 reaches the tension limit position Pe from the braking position Pb. In other words, the coil spring 151 has an elastic repulsive force (tensile reaction force in a direction in which the flange 112b and the flange 142c approach each other until the linear motion member 142 moves from the braking position Pb toward the tension limit position Pe. )give. The tension limit position Pe is a position where the elastic force of the coil spring 151 at the tension limit position Pe becomes equal to the magnetic force between the second end 151b and the flange 112b. When the linear motion member 142 exceeds the tensile limit position Pe, the second end 151b and the flange 112b are separated from each other, and the coil spring 151 is in the free state Sf.

  Also in this case, before and after the linear motion member 142 reaches the tension limit position Pe, the axial force of the third rotation center Ax3 applied to the flange 142c, the movement resistance of the linear motion member 142, and the driving of the motor 120 are thus achieved. The rate of change of current changes. Specifically, the change rate of the drive current decreases before and after reaching the tension limit position Pe.

  Therefore, as shown in FIG. 10, the control unit 123 controls the rotation of the motor 120 so that the linear motion member 142 moves from the braking position Pb toward the non-braking position Pn (in the rotational direction of movement). The motor 120 is stopped using the detection of the sudden change Dd (rapid decrease) of the drive current as a trigger (third stop condition).

  In the graph of FIG. 10, the solid line indicates the change over time of the drive current according to the present embodiment. A broken line indicates a change with time of drive current in a configuration (comparative example) that detects an increase in load torque of the motor 120 due to compression of the coil spring at the non-braking position Pn. As shown in FIG. 10, in the comparative example, the motor 120 is stopped at the time te when the drive current increases, whereas in the present embodiment, the motor at the time t1 when the drive current decreases due to the sudden change Dd of the drive current. Since 120 is stopped, the drive current is smaller by ΔIn than the comparative example. As the driving current of the motor 120 at the time of stopping, and thus the load torque of the motor 120, increases, the load torque when the linear motion member 142 starts to move from the non-braking position Pn toward the braking position Pb increases. That is, according to the present embodiment, the load torque of the motor 120 at the time of entering the released state is reduced, so that the load torque of the motor 120 when starting the rotation of the motor 120 from the released state can be reduced. . According to the present embodiment, for example, the releasable connection structure between the second end portion 151b and the flange 112b can be realized as a relatively simple configuration with a magnet.

(Second Embodiment)
The drive mechanism 100A of the second embodiment shown in FIG. 11 has the same configuration as the drive mechanism 100 of the first embodiment. Therefore, also in this embodiment, the same result based on the same configuration as the first embodiment is obtained.

  However, in the present embodiment, the second end 151b of the coil spring 151 and the flange 112b are fixed by, for example, mechanical coupling or welding. On the other hand, the first end 151a (front end) of the coil spring 151 and the flange 142c can be switched between a connected state and a separated state with elastic deformation of at least one of the first end 151a and the flange 142c. It is connected via the mechanism 142d. The attaching / detaching mechanism 142d detachably holds the outer peripheral portion and the end portion of the first end portion 151a of the coil spring 151. The attachment / detachment mechanism 142d may also be referred to as a snap fastener or a snap fit mechanism. Therefore, according to the present embodiment, for example, the releasable connection structure between the first end portion 151a and the flange 142c can be realized as a relatively simple configuration by a configuration involving elastic deformation.

(First modification)
The drive mechanism 100B of the first modification shown in FIG. 12 has the same configuration as the drive mechanism 100A of the second embodiment. Therefore, also by this modification, the same result based on the same structure as the said 2nd Embodiment is obtained.

  However, in this modification, the attaching / detaching mechanism 142d detachably holds the inner peripheral portion and the end portion of the first end portion 151a of the coil spring 151. The attachment / detachment mechanism 142d may also be referred to as a snap fastener, a snap fit mechanism, or the like.

  According to the second embodiment and the first modification, the same effect as the first embodiment can be obtained without using a magnet.

(Second modification)
A drive mechanism 100C of the first modification shown in FIG. 13 has the same configuration as the drive mechanism 100 of the first embodiment. Therefore, also in this embodiment, the same result based on the same configuration as the first embodiment is obtained.

  However, in this modification, the second end portion 151b of the coil spring 151 is fixed to the flange 112b, and the first end portion 151a of the coil spring 151 and the flange 142c are releasably connected by magnetic force.

  As mentioned above, although embodiment of this invention was illustrated, the said embodiment is an example and is not intending limiting the range of invention. The above embodiment can be implemented in various other forms, and various omissions, replacements, combinations, and changes can be made without departing from the spirit of the invention. In addition, the specifications (structure, type, direction, shape, size, length, width, thickness, height, number, arrangement, position, material, etc.) of each configuration, shape, etc. are appropriately changed. Can be implemented.

  For example, in the above embodiment, the brake device 2 is configured as a leading trailing drum brake, but the present invention can also be configured as other types of brake devices. Further, the present invention can be implemented as a configuration corresponding to the other actuator of a brake device having a disc brake by one actuator and a drum brake by another actuator.

  In the above-described embodiment, the configuration in which the operating member that moves the braking member is the cable 82 is exemplified. However, the operating member may be other than the cable 82 such as a rod or a lever. The actuating member may move the braking member by pushing instead of pulling. Further, the elastic member and the housing may be releasably connected with elastic deformation of at least one of the elastic member and the housing.

  DESCRIPTION OF SYMBOLS 1 ... Wheel, 2 ... Brake device (brake for vehicles), 3 ... Brake shoe (braking member), 110 ... Housing, 120 ... Motor, 123 ... Control part, 141 ... Rotating member, 142 ... Direct acting member, 151 ... Coil Spring (elastic member), 151a ... first end (one end or the other), 151b ... second end (one end or the other), Pb ... braking position, Pn ... non-braking position (release position), Sf ... free State.

Claims (4)

A housing;
A motor,
A rotating member housed in the housing and rotated by the motor;
A braking position housed in the housing and connected to a braking member that brakes the wheel, and the braking member brakes the wheel as the rotating member rotates, and the braking member brakes the wheel. A linear motion member that linearly moves between a release position that is in a state of releasing
An elastic member that changes the rotational load of the motor by applying an elastic force to the linear motion member by elastic expansion and contraction according to the movement of the linear motion member;
A control unit for stopping the motor based on the rate of change of the current value of the motor;
With
In the state where the linear motion member is disposed at the release position, the elastic member is in a free state,
When the linear motion member moves from the release position to the braking position, the elastic member starts to compress the elastic member between the housing and the housing before reaching the braking position, until the elastic member reaches the braking position. A vehicle brake that compresses components. One end of the elastic member is fixed to one of the housing and the linear motion member, and the other end of the elastic member is releasably connected to the other of the housing and the linear motion member,
The other end is connected to the other in a tension state within a predetermined length of the elastic member, and the other end is disconnected from the other in a tension state exceeding the predetermined length,
The linear motion member pulls the elastic member between the housing and the housing when moving from the braking position to the release position;
Before the linear motion member reaches the release position, the elastic member enters a tension state exceeding the predetermined length, and the connection between the other end and the other of the housing and the linear motion member is released. The vehicle brake according to claim 1.   The vehicle brake according to claim 2, wherein the other end and the other of the housing and the linear motion member are connected by magnetic force.   The connected state and the separated state of the other end and the other are switched with elastic deformation of at least one of the other end and the other of the housing and the linear motion member. The brake for vehicles as described.

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