JP4867278B2 - Tension sensor and electric parking brake - Google Patents

Description

  The present invention relates to a tension sensor and an electric parking brake using the same.

  Conventionally, a tension sensor described in Patent Document 1 is known. This tension sensor includes a housing that holds a coil spring, and a movable plate that moves relative to the housing while deforming the coil spring by receiving tension. A magnet is fixed to the movable plate, and a Hall IC is fixed to the housing. In this tension sensor, the magnetic field in the vicinity of the Hall IC changes according to the relative displacement between the housing and the movable plate, thereby changing the output voltage from the Hall IC. Therefore, according to this tension sensor, the tension applied to the movable plate can be detected by the output voltage from the Hall IC.

An electric parking brake comprising an electric motor, a conversion mechanism that converts the rotational driving force of the electric motor into a linear driving force, and a cable that transmits the linear driving force generated by the conversion mechanism to the parking brake. This tension sensor can be employed to detect.
JP 2000-21002 A

  However, in the conventional tension sensor described above, the direction of the movable plate relative to the housing is not necessarily constant because there are not enough restrictions on the movement of the movable plate in directions other than the tension direction. For this reason, in this tension sensor, even if the tension is the same, the relative displacement between the housing and the movable plate may vary, so that the detection accuracy is not sufficient.

  Further, when the parking brake is released, the electric parking brake is released by releasing the cable until the output of the tension sensor becomes a predetermined value or less, and when the parking brake is braked, the output of the tension sensor becomes a predetermined value or more. The cable is pulled until it is in a braking state. At this time, in order to ensure that the parking brake is released and braked when the parking brake is released and during braking, each predetermined value must be determined in consideration of variations in detection accuracy of the tension sensor. Don't be. For this reason, when this tension sensor is used for a parking brake, the tension sensor output may still be larger than the predetermined value even though it is actually released. It will be released excessively. In addition, there is a case where the output of the tension sensor is still smaller than a predetermined value even though the braking state is actually set. In this case, the cable is excessively pulled. Therefore, if this tension sensor is used for a parking brake, the responsiveness when the parking brake is brought into a braking state or a released state is deteriorated.

  The present invention has been made in view of the above-described conventional problems, and provides a tension sensor with high detection accuracy and an electric parking brake with good responsiveness in a braking state or a release state.

  In order to solve the above-described problem, the tension sensor according to claim 1 is characterized in that a first member that holds an elastic body and a first member that deforms the elastic body by receiving tension. A tension sensor comprising a second member that performs relative movement, and a displacement detection means that detects a relative displacement amount between the first member and the second member;

Supported by the second member (23), said third member capable idler (24) relative to the second member axially and perpendicular to the axial direction (23), said third member (24) A rear end side stop member (31) fixed to the second member (23) for restricting movement of the second member (23) in the axial direction toward the first member (21); Provided between the front end side stop member (30) fixed to the second member and the third member (24), and the third member (24) is supported by the second member (23) so as to be freely movable. A compression spring (28), a guide groove (26d) recessed in one of the first member (21) and the third member (24) and extending in the direction in which the tension acts, and the first member (21) and the other of the third member (24), and is slidable in the guide groove (26d). Comprising such a ridge (24d), said displacement detecting means (25, 27) is a tension by detecting a relative displacement between said first member (21) and said third member (24) Is to detect .

  The tension sensor according to claim 2 is characterized in that, in claim 1, the displacement detecting means includes a magnet and a Hall IC, the Hall IC is provided in the first member, and the third member is provided with the Hall IC. A magnet is provided.

  The characteristics of the tension sensor according to claim 3 are an electric motor, a conversion mechanism for converting the rotational driving force of the electric motor into a linear driving force, a cable for transmitting the linear driving force by the conversion mechanism to a parking brake, In the electric parking brake with

    The cable is provided with the tension sensor according to claim 1 or 2.

In the tension sensor according to claim 1, a rear end side stop member fixed to the second member to restrict the third member from moving in the axial direction of the second member toward the first member, The third member is movable in the axial direction of the second member and the direction perpendicular to the axial direction by the compression spring provided between the front end side stopper member fixed to the two members and the third member. It is supported by two members. One of the first member and the third member has a guide groove extending in the direction in which the tension acts, and the other of the first member and the third member has a ridge that can slide in the guide groove. Therefore, the movement of the first member and the third member in directions other than the tension direction is restricted. Therefore, the relative displacement between the first member and the third member is less likely to vary with the same tension. And a displacement detection means detects tension | tensile_strength by detecting the relative displacement amount between a 1st member and a 3rd member. Here, since the third member is supported by the second member, the relative displacement amount between the first member and the third member can be considered as the relative displacement amount between the first member and the second member. Therefore, according to the tension sensor of the first aspect, high detection accuracy can be obtained.

  In the tension sensor according to the second aspect, since the displacement is detected by the magnet and the Hall IC, the displacement can be reliably detected. In addition, a printed circuit board, wiring, and the like are required for the Hall IC, but they are not required for the magnet. Therefore, the magnet is smaller and easier to handle than the Hall IC. Here, since the third member moves together with the second member, the third member is smaller than the first member, and it is desirable in terms of reliability to make the third member simpler than the first member. In this tension sensor, since the magnet is provided on the third member, it is difficult to break down and higher reliability can be obtained.

  In the electric parking brake according to the third aspect, since the tension sensor having high detection accuracy is used, it is possible to prevent the cable from being excessively released when the parking brake is released. Further, it is possible to prevent the cable from being pulled excessively during braking of the parking brake. Therefore, it is possible to improve responsiveness when the parking brake is brought into a braking state or a released state.

  DESCRIPTION OF EMBODIMENTS Embodiments embodying a tension sensor and an electric parking brake of the present invention will be described below with reference to the drawings. FIG. 1 is a partially cutaway plan view of an electric parking brake for automobiles of this embodiment. The electric parking brake includes an electric motor 1, a conversion mechanism 2 that converts the rotational driving force of the electric motor 1 into a linear driving force, and a pair of cables that transmit the linear driving force of the conversion mechanism 2 to the parking brakes 5 and 6. 3 and 4. Further, a speed reduction mechanism 7 is provided between the electric motor 1 and the conversion mechanism 2, and an equalizer mechanism 8 is provided between the conversion mechanism 2 and the cables 3 and 4. Further, a tension sensor 20 is provided between the equalizer mechanism 8 and the one cable 3. The electric motor 1, the conversion mechanism 2, the equalizer mechanism 8, and the tension sensor 20 are accommodated in the housing 10. The housing 10 houses an electric control unit ECU that controls the rotational drive of the electric motor 1.

  The electric motor 1 is controlled by the electric control unit ECU, and is driven to rotate in the forward direction by the driver operating a brake switch (not shown), and reversely operated by the driver operating a release switch (not shown). Are driven to rotate. The reduction mechanism 7 decelerates the rotational driving force of the electric motor 1 and transmits it to the conversion mechanism 2, and is constituted by a reduction gear (not shown) including an input gear and an output gear. The speed reduction mechanism 7 is assembled in a casing 11 assembled to the housing 10, the input gear is fixed to the output shaft (not shown) of the electric motor 1, and the output gear is one end of the screw shaft 2a (inside the casing 11) described later. Is fixed to the protruding end).

  The conversion mechanism 2 converts the rotational driving force of the electric motor 1 transmitted through the speed reduction mechanism 7 into a linear driving force, and a screw shaft 2a and a nut that is screwed and assembled to the screw shaft 2a. 2b. When the screw shaft 2a is rotationally driven in the forward direction, the nut 2b is moved in the axial direction of the screw shaft 2a from the release position indicated by the broken line toward the braking position indicated by the phantom line. Further, when the screw shaft 2a is rotationally driven in the reverse direction, the nut 2b is moved in the axial direction of the screw shaft 2a from the braking position indicated by the phantom line toward the release position indicated by the broken line. Yes. The screw shaft 2a is assembled to the housing 10 via a pair of bearings 12 and 13 so as to be rotatable and immovable in the axial direction.

  The equalizer mechanism 8 equally distributes the linear driving force acting on the nut 2b to the two outputs, and is configured by a lever 9 that is swingably assembled to the nut 2b. The lever 9 is assembled to the nut 2b at a central portion thereof so as to be able to swing a predetermined amount. An inner wire 3a of one cable 3 is rotatably connected to an arm portion 9a which is one output portion of the lever 9 via a tension sensor 20, and an arm portion 9b which is the other output portion is connected to the other arm portion 9b. The inner wire 4a of the cable 4 is connected so as to be directly rotatable.

  As described above, the tension sensor 20 is interposed in the connecting portion between the inner wire 3a of one cable 3 and the arm portion 9a which is one output portion of the equalizer mechanism 8, and detects the tension applied to the inner wire 3a. To do. As shown in FIGS. 2 and 3, the tension sensor 20 includes a spring case 21, a compression coil spring 22, a shaft 23, a magnet case 24, a magnet 25, a cover 26, and a Hall IC 27. Here, the spring case 21 and the cover 26 are the first members of claim 1. The shaft 23, the magnet case 24, and the compression coil spring 22 are the second member, the third member, and the elastic body of the first aspect, respectively.

  The spring case 21 has a cylindrical shape, and a storage chamber 21a is formed therein. Further, a shaft hole 21c is provided in the tip end surface 21b of the spring case 21 in the axial direction. Further, a wall portion 21d is provided on the rear end side of the spring case 21, and the inner wire 3a of the cable 3 can be connected. A shaft 23 extending through the shaft hole 21c and extending to the front end side is stored in the storage chamber 21a of the spring case 21. The shaft 23 is moved in the rear end direction by a compression coil spring 22 wound in the storage chamber 21a. It is energized. The shaft 23 is restricted from moving in the rear end direction by the wall 21d. Further, a large tension is applied to the shaft 23 via the arm portion 9a, and the tension includes a component perpendicular to the axial direction. Therefore, a gap is provided between the shaft 23 and the shaft hole 21c so that a smooth operation between the shaft 23 and the spring case 21 can be ensured.

  The magnet case 24 includes a cylindrical case main body 24a and a case portion 24b that protrudes integrally from the case main body 24a in the radial direction. A shaft 23 passes through the case body 24a, and four spring holes 24c are recessed at a position that divides the outer periphery of the case body 24a into four equal parts in the axial direction from the tip side. A compression spring 28 is embedded in each spring hole 24 c, and a Teflon spacer 29 is provided on the distal end side of the case body 24 a in contact with one end of the compression spring 28. Retaining rings 30 and 31 are fixed to the front end side of the spacer 29 and the rear end side of the case main body 24a. For this reason, the magnet case 24 is supported on the shaft 23 so as to be freely movable while its axial movement is restricted. Accordingly, even when a large tension including a component perpendicular to the axial direction is applied to the shaft 23 via the arm portion 9a, the smooth operation of the magnet case 24 is ensured. Further, the case portion 24b accommodates a magnet 25 therein, and has a protrusion 24d protruding in the axial direction on the side surface.

  The cover 26 includes a cover body 26a, a first guide 26b, and a second guide 26c. The cover main body 26 a is fixed to the spring case 21. The first guide 26b and the second guide 26c project from the front end side of the cover body 26a with a U-shaped cross-sectional shape, and the hall IC 27 faces the magnet 25 of the case portion 24b in the first guide 26b. Is provided. Further, the case portion 24b is fitted into the first guide 26b and the second guide 26c, and a guide groove 26d that fits with the protrusion 24d of the case portion 24b is recessed in the axial direction on the inner surface of the second guide 26c. Has been. As a result, when the shaft 23 and the spring case 21 move relative to each other, the magnet case 24 moves together with the shaft 23 due to the protrusion 24d sliding in the guide groove 26d. At this time, the rotation of the magnet case 24 can be prevented by fitting the protrusion 24d into the guide groove 26d, but the case portion 24b itself is fitted into the first guide 26b and the second guide 26c. Therefore, the rotation of the magnet case 24 can be reliably prevented. Even when a large tension including a component perpendicular to the axial direction is applied to the shaft 23 via the arm portion 9a, smooth operation between the case portion 24b and the first guide 26b and the second guide 26c is ensured. A gap is provided between the upper surface of the case portion 24b and the second guide 26c so as to be able to do so.

Next, the operation of the electric parking brake for automobiles configured as described above will be described. When the driver operates the brake switch, the output shaft of the electric motor 1 is rotationally driven in the forward direction by the electric control unit ECU. The rotational driving force of the output shaft of the electric motor 1 is decelerated by a reduction gear composed of an input gear and an output gear of the reduction mechanism 7, and is transmitted to the screw shaft 2a. As a result, the screw shaft 2a is driven to rotate in the forward direction, and the nut 2b and the lever 9 assembled to the nut 2b move from the release position shown by the broken line toward the braking position shown by the phantom line. Moved to. Then, the arm portion 9a, the inner wire 3a which is connected to 9b, 4 a of the lever 9 is pulled, the cable 3, 4 is pulled. At this time, since the tension sensor 20 is interposed at the connecting portion between the inner wire 3a and the arm portion 9a, the shaft 23 is pulled in the distal direction. While the parking brakes 5 and 6 are not sufficiently braked, the inner wire 3a is not applied with such a large tension. Therefore, the shaft 23 and the spring case 21 move together, and the magnet case 24 and the cover 26 are moved together. Also move together. However, when braking is applied to the parking brakes 5 and 6, the movement of the spring case 21 connected to the inner wire 3a is restricted, so that a large tension is applied to the inner wire 3a. The shaft 23 moves relative to the spring case 21 while compressing the compression coil spring 22 against the repulsive force of the compression coil spring 22. As a result, the magnet case 24 also moves relative to the cover 26, and this displacement is detected as a tension by the magnet 25 and the Hall IC 27. When the output of the tension sensor 20 becomes equal to or higher than a predetermined value, the electric control unit ECU determines that the parking brakes 5 and 6 are in a braking state and stops the rotation of the electric motor 1. Thus, the parking brakes 5 and 6 are brought into a braking state.

When the driver operates the release switch, the output shaft of the electric motor 1 is rotationally driven in the reverse direction by the electric control unit ECU. The rotational driving force of the output shaft of the electric motor 1 is decelerated by a reduction gear composed of an input gear and an output gear of the reduction mechanism 7, and is transmitted to the screw shaft 2a. As a result, the screw shaft 2a is rotationally driven in the opposite direction, and the nut 2b and the lever 9 assembled to the nut 2b move from the braking position indicated by the phantom line toward the release position indicated by the broken line. Moved to. Then, the arm portion 9a, the inner wire 3a which is connected to 9b, 4 a of the lever 9 is released, the cable 3, 4 is released. At this time, since the tension sensor 20 is interposed at the connecting portion between the inner wire 3a and the arm portion 9a, the shaft 23 is pulled in the rear end direction. While the parking brakes 5 and 6 are not fully released, a certain amount of tension is applied to the inner wire 3a, so that the spring case 21 resists the repulsive force of the compression coil spring 22 and causes the compression coil spring 22 to move. It moves relative to the shaft 23 in a compressed state. As a result, the magnet case 24 also moves relative to the cover 26, and this displacement is detected as a tension by the magnet 25 and the Hall IC 27. However, when the parking brakes 5 and 6 start to be released, a relatively large tension is not applied to the inner wire 3a, so that the relative movement between the shaft 23 and the spring case 21 becomes small. When the output of the tension sensor 20 becomes equal to or less than the predetermined value, the electric control unit ECU determines that the parking brakes 5 and 6 are in the released state and stops the rotation of the electric motor 1. Thus, the parking brakes 5 and 6 are released.

  In the present embodiment, the guide groove 26d is provided on the inner surface of the second guide 26c and the protrusion 24d is provided on the side surface of the case portion 24b. However, the protrusion 24d is provided on the inner surface of the second guide 26c, and the case portion 24b. A guide groove 26d may be provided on the side surface.

  In the above description, the tension sensor and the electric parking brake of the present invention have been described based on the electric parking brake for automobiles. However, the present invention is not limited to the above-described embodiment, and is contrary to the technical idea of the present invention. Needless to say, as long as it is not applied, it can be changed and applied as appropriate.

The partially broken top view of the electric parking brake for motor vehicles concerning embodiment. A sectional view of a tension sensor concerning an embodiment. II sectional view taken on the line in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Electric motor, 2 ... Conversion mechanism, 3, 4 ... Cable, 5, 6 ... Parking brake, 20 ... Tension sensor, 21 ... 1st member (spring case), 23 ... 2nd member (shaft), 24 ... 1st 3 members (magnet case), 22 ... elastic bodies (compression coil springs) 25, 27 ... displacement detection means (25 ... magnets, 27 ... Hall IC), 24d ... ridges, 26d ... guide grooves.

Claims (3)

A first member (21) that holds the elastic body (22) and a second member that moves relative to the first member (21) while deforming the elastic body (22) by receiving tension. 23) and a tension sensor (20) comprising a displacement detection means (25, 27) for detecting a relative displacement amount between the first member (21) and the second member (23),
Supported by the second member (23), said third member capable idler (24) relative to the second member axially and perpendicular to the axial direction (23), said third member (24) A rear end side stop member (31) fixed to the second member (23) for restricting movement of the second member (23) in the axial direction toward the first member (21); Provided between the front end side stop member (30) fixed to the second member and the third member (24), and the third member (24) is supported by the second member (23) so as to be freely movable. A compression spring (28), a guide groove (26d) recessed in one of the first member (21) and the third member (24) and extending in the direction in which the tension acts, and the first member (21) and the other of the third member (24), and is slidable in the guide groove (26d). Comprising such a ridge (24d), said displacement detecting means (25, 27) is a tension by detecting a relative displacement between said first member (21) and said third member (24) A tension sensor (20) characterized by detecting .   In Claim 1, the displacement detection means (25, 27) has a magnet (25) and a Hall IC (27), the Hall IC (27) is provided in the first member (21), A tension sensor (20), wherein the third member (24) is provided with the magnet (25). An electric motor (1), a conversion mechanism (2) for converting the rotational driving force of the electric motor (1) into a linear driving force, and the linear driving force by the conversion mechanism (2) is converted into a parking brake (5, 6) In an electric parking brake comprising cables (3, 4) for transmitting to
An electric parking brake, wherein the cable (3, 4) is provided with a tension sensor (20) according to claim 1 or 2.

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