JP4305271B2 - Magnetostrictive torque sensor - Google Patents

Description

  The present invention relates to a non-contact magnetostrictive torque sensor, and more particularly to a non-contact magnetostrictive torque sensor that detects, in a non-contact manner, a torque applied to a rotating shaft having magnetostrictive characteristics from a change in inductance of a detection coil caused by a change in permeability.

  In a power steering mechanism, an engine control mechanism, a power transmission mechanism, and the like of an automobile, there is a high need to detect torque applied to a handle shaft that is a rotating shaft and other passive shafts.

  In general, when a force is applied to a material having magnetostrictive characteristics, the relative permeability changes, the relative permeability decreases in the compressive force direction, and the relative permeability increases in the tension direction. A magnetostrictive torque detection device using this principle is described in Patent Document 1, for example.

  FIG. 11A shows a schematic diagram of a magnetostrictive torque detection device described in Patent Document 1. FIG. In the magnetostrictive torque detection apparatus of FIG. 11A, a plurality of magnetostrictive films 13 and 13 are fixed to the outer periphery of the rotary shaft 11 that is a passive shaft at ± 45 ° with respect to the rotary shaft 11, and ± 45 to the outer periphery thereof. The ring-shaped detection coils 12 and 12 are disposed corresponding to the magnetostrictive films 13 and 13, respectively. When torque is applied to the rotating shaft 11 from the outside, a tension is generated in one of the magnetostrictive films 13 and 13 and a compressive force is generated in the other, resulting in distortion, and the magnetic permeability of the magnetostrictive films 13 and 13 changes. Changes in the inductance of the ring-shaped detection coils 12 and 12 due to changes in the magnetic permeability of the magnetostrictive films 13 and 13 are detected and output.

In addition to the magnetostrictive torque detector described above, there is one shown in FIG. The magnetostrictive torque detecting device of FIG. 11B uses the detection coils 12 and 12 wound on the U-shaped magnetic core 14 disposed opposite to the magnetostrictive rotating shaft 11 to change the permeability of the magnetostrictive rotating shaft 11. It is detected and output.
JP-A-1-94230

  However, according to the magnetostrictive torque detecting device of FIG. 11A, there is a problem that the rotating shaft 11 needs to be processed because the ± 45 ° magnetostrictive films 13 and 13 are fixed to the rotating shaft 11.

  Further, according to the magnetostrictive torque detecting device of FIG. 11B, it is not necessary to process the rotating shaft 11 and it can be easily mounted on the rotating shaft 11, but the U-shaped magnetic core 14 around which the detection coil 12 is wound is rotated. Since there is a portion that is not rotationally symmetric like the ring-shaped magnetic core with respect to the shaft 11 and the rotating shaft 11 does not face the U-shaped magnetic core 14, the sensitivity of the output signal is low, and the zero point of the output signal is the rotating shaft 11. There is a problem that it fluctuates greatly with the rotation of.

  Accordingly, the object of the present invention is to improve the sensitivity of the output signal without applying a process such as fixing a ± 45 ° magnetostrictive film to the rotating shaft, and to reduce the zero point fluctuation of the output signal accompanying the rotation of the rotating shaft. Accordingly, it is an object of the present invention to provide a non-contact magnetostrictive torque sensor that accurately detects torque applied to the magnetostrictive rotating shaft.

  A further object of the present invention is to provide a non-contact magnetostrictive torque sensor that detects changes in magnetic flux in the compression direction and tension direction of the rotating shaft.

  Another object of the present invention is to provide a non-contact magnetostrictive torque sensor with high coil detection sensitivity.

  Another object of the present invention is to provide a non-contact magnetostrictive torque sensor that can be easily mounted on a rotating shaft.

  It is still another object of the present invention to provide a non-contact magnetostrictive torque sensor that is easy to wind a coil and assemble and manufacture a detection circuit.

According to the present invention, a rotating shaft having a magnetostrictive characteristic that rotates around a central axis, and a distortion of the rotating shaft that is arranged coaxially with the rotating shaft while having a predetermined distance from an outer periphery of the rotating shaft are detected. In a magnetostrictive torque sensor having a magnetic ring around which a coil is wound,
The magnetic ring is formed of a ferromagnetic portion and a non-magnetic portion that are alternately arranged in a circumferential direction inclined by 45 ° with respect to the central axis,
The coil provides a magnetostrictive torque sensor, wherein the coil is wound in a direction orthogonal to the inclination direction of the ferromagnetic part and the nonmagnetic part.

In order to detect a change in magnetic flux in the tension direction of the rotating shaft, the magnetic ring is inclined in the tension direction of the rotating shaft and alternately arranged in the circumferential direction and tension detecting ferromagnetic portions. In order to detect a change in magnetic flux in the compression direction of the rotating shaft, the first magnetic ring formed from a non-magnetic portion is alternately arranged in the circumferential direction inclining in the compressing direction of the rotating shaft. A second magnetic ring formed from a compression detecting ferromagnetic portion and a compression detecting non-magnetic portion;
The coil includes a first coil wound around the first magnetic ring in a compression direction, and a second coil wound around the second magnetic ring in a tension direction. It is characterized by including.

  The magnetic ring is characterized in that an area of the nonmagnetic part is smaller than an area of the ferromagnetic part.

  The magnetic ring includes a semi-cylindrical magnetic core that is divided into two at the position of the nonmagnetic portion along the inclination direction of the nonmagnetic portion.

  A coil is independently wound around each of the two half-cylindrical magnetic cores.

  According to the non-contact magnetostrictive torque sensor of the present invention, the magnetic flux generated by the coil inclined by 45 ° with respect to the rotation axis is concentrated in the inclination direction of the ferromagnetic part and the non-magnetic part, so that the sensitivity of the output signal is increased. be able to. Further, since the coil is wound around the magnetic ring and is rotationally symmetric with respect to the rotation axis, the output signal does not depend on the rotation angle of the rotation axis. That is, the zero point fluctuation of the output signal accompanying the rotation of the rotating shaft can be reduced.

  Further, according to the present invention, the first magnetic ring formed of the tension detecting ferromagnetic portion and the tension detecting nonmagnetic portion which are inclined in the tension direction of the rotating shaft and are alternately arranged in the circumferential direction thereof. A first coil wound in the compression direction, and a ferromagnetic part for compression detection and a non-magnetic part for compression detection which are inclined in the compression direction of the rotating shaft and alternately arranged in the circumferential direction. Since it includes the second coil that is wound around the formed second magnetic ring while being inclined in the tension direction, it is possible to detect a change in magnetic flux in the tension direction and the compression direction of the rotating shaft.

  According to the present invention, the magnetic ring can increase the detection sensitivity of the coil because the area of the nonmagnetic portion is smaller than the area of the ferromagnetic portion.

  Furthermore, according to the present invention, since the torque sensor is divided into two semi-cylindrical magnetic cores, it can be easily attached to the magnetostrictive rotating shaft.

  In addition, according to the present invention, since the coils are wound independently around the half-cylindrical magnetic core divided into two, it is easy to wind the coils and to assemble and manufacture the detection circuit.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows a first embodiment of a magnetostrictive torque sensor according to the present invention. The magnetostrictive torque sensor includes a rotating shaft 10 having magnetostrictive characteristics, and a coil 21 (hereinafter simply referred to as a “+ 45 ° coil”) tilted by + 45 ° with respect to the axis O of the rotating shaft 10. The magnetic ring 31 is composed of a ring 31 and has a structure in which a magnetic ring 31 around which a + 45 ° coil 21 is wound is concentrically arranged through the rotary shaft 10. The magnetic ring 31 around which the + 45 ° coil 21 is wound includes a nonmagnetic portion 31a and a ferromagnetic portion 31b (hereinafter simply referred to as “−45 ° nonmagnetic portion”) and an inclined portion of −45 ° with respect to the axis O of the rotating shaft 10, respectively. As shown in FIG. 1, the magnetic ring 31 has a circumference of a −45 ° nonmagnetic portion 31a and a −45 ° ferromagnetic portion 31b. It has a structure that is alternately arranged in the direction. Here, the −45 ° nonmagnetic portion 31a desirably has a low relative permeability, and the −45 ° ferromagnetic portion 31b desirably has a high relative permeability. The number of the −45 ° nonmagnetic portion 31a and the −45 ° ferromagnetic portion 31b is 4 to 2N (N = 2, 3, 4,...). In order to increase the detection sensitivity of the + 45 ° coil 21, the area of the −45 ° nonmagnetic portion 31a is preferably smaller than the area of the −45 ° ferromagnetic portion 31b.

Next, the operation principle of the magnetostrictive torque sensor of the present invention will be described. As shown in FIG. 2, when viewed from the axial direction X, a torque T is applied to the rotary shaft 10 so that the left side is counterclockwise in the drawing and the right side is clockwise in the drawing. Hereinafter, the torque T in this direction is defined as the positive direction. At this time, when viewed from the front side of the rotating shaft 10 (the front surface of the drawing), a compressive force is applied to the rotating shaft 10 in the + 45 ° direction and a tension is applied to the −45 ° direction. The principal stress σ is proportional to the torque T, and is given by the following equation, where D is the diameter of the rotating shaft 10.
σ = 16T / (πD ³ ) (1)
At this time, if the rotating shaft 10 has a magnetostrictive effect, axial magnetic anisotropy Ku is induced by the main stress σ.
Ku = 2 · (3/2) λsσ = 48λsT / (πD ³ ) (2)
Here, λs is a saturation magnetostriction constant of the rotating shaft 10. Due to this axial magnetic anisotropy Ku, the + σ direction becomes the easy magnetization direction, the −σ direction becomes the magnetization difficult direction, and the relative permeability in the magnetization easy direction + σ direction increases due to the magnetostatic energy, and conversely the magnetization difficult direction. The relative permeability in the −σ direction decreases. Therefore, when a current is passed through a coil inclined in the hard magnetization direction-σ direction (compressive force direction), the magnetic flux formed by the coil is inclined in the easy magnetization direction + σ direction (tensile direction) and the relative permeability in the tension direction increases. Since the sensitive current flows in the direction of decreasing the magnetic flux in the tension direction and the sensitive voltage is induced by the sensitive current, the inductance of this coil increases. Conversely, when a current is passed through a coil inclined in the easy magnetization direction + σ direction (tensile direction), the magnetic flux formed by the coil is inclined in the difficult magnetization direction−σ direction (compressive force direction) and the relative permeability in the compressive force direction is increased. Since the sensitivity current flows in the direction of increasing the magnetic flux in the compressive force direction and the sensitivity voltage is induced by the sensitivity current, the inductance of the coil is reduced.

  As shown in FIGS. 1 and 2, the magnetic ring 31 is made of a composite magnetic material having both a −45 ° nonmagnetic portion 31a and a −45 ° ferromagnetic portion 31b, and the −45 ° nonmagnetic portion 31a and −45 °. The ferromagnetic portions 31b are alternately arranged in the circumferential direction. The + 45 ° coil 21 is wound around the magnetic ring 31 at an angle of + 45 ° with respect to the axis O of the rotating shaft 10 and orthogonal to the −45 ° nonmagnetic portion 31a and the −45 ° ferromagnetic portion 31b. . Accordingly, the magnetic flux Φ generated by the + 45 ° coil 21 when the current I flows through the + 45 ° coil 21 is −45 ° nonmagnetic portion 31a of the magnetic ring 31 (the nonmagnetic portion 31a is weakly magnetized in the −45 ° direction). Further, since it passes through the −45 ° ferromagnetic portion 31b, the magnetic flux Φ is forced to pass through the rotating shaft 10 with an inclination of −45 ° with respect to the axis O of the rotating shaft 10 as shown in FIG. Therefore, the magnetic flux Φ passing through the rotating shaft 10 is concentrated in the easy magnetization direction + σ direction (tensile direction) and the relative permeability in the tension direction is increased, so that the inductance of the + 45 ° coil 21 is increased.

FIG. 3 is a detection circuit for detecting the torque applied to the magnetostrictive rotating shaft 10 from the electrical characteristics of the + 45 ° coil 21 described above. A bridge circuit as shown in FIG. 3 is configured by using the + 45 ° coil 21 and the three resistors R ₁ , R ₂ , and R ₃ (R ₁ = R ₂ = R ₃ = 10Ω). Then, an oscillator 70 for driving a circuit is connected to both ends of the + 45 ° detection coil 21 and the resistor R ₃ connected in series and the series connected resistors R ₁ and R _2, and the + 45 ° detection coil 21 and the resistor R ₃ are connected. And between the series-connected resistors R ₁ and R ₂ , a lock-in amplifier 80 that detects and amplifies and outputs a differential signal generated from the bridge circuit when torque is applied is connected.

Next, the operation of the detection circuit of FIG. 3 will be described. High frequency current I generated from the oscillator 70 flows to the resistor _{R 1} and + 45 ° detection coil 21, flows out of the resistor _{R 2} and the resistor _{R 3.} When torque is not applied, zero point adjustment is performed so that the detection circuit is in an equilibrium state. As shown in FIG. 2, when a positive torque T is applied, the inductance L of the + 45 ° detection coil 21 increases by ΔL, and the output V from the lock-in amplifier 80 increases in the positive direction. On the other hand, when a negative torque is applied, the inductance L of the + 45 ° detection coil 21 decreases by ΔL, and the output V from the lock-in amplifier 80 decreases in the negative direction. From this, the direction and magnitude of the torque T are detected.

According to the detection circuit of FIG. 3, noise is removed by the lock-in amplifier 80 by balancing the bridge circuit of the + 45 ° coil 21 and the three resistors R ₁ , R ₂ , and R ₃ . Stable and accurate zero point adjustment can be easily performed, and the sensitivity of the output voltage can be increased.

  Furthermore, according to the structure of the magnetostrictive torque sensor described above, the magnetic flux Φ generated by the + 45 ° coil 21 is concentrated in the −45 ° direction, so that the sensitivity of the output signal can be increased. Further, since the + 45 ° coil 21 is wound around the magnetic ring 31 and is rotationally symmetric with respect to the magnetostrictive rotating shaft 10, the output signal does not depend on the rotational angle of the magnetostrictive rotating shaft 10. That is, the zero point fluctuation of the output signal accompanying the rotation of the magnetostrictive rotating shaft 10 can be reduced.

  In the first embodiment described above, the detection coil is inclined + 45 ° with respect to the axis O of the rotating shaft 10, and the nonmagnetic portion and the ferromagnetic portion of the magnetic ring are inclined −45 ° with respect to the axis O of the rotating shaft 10. However, conversely, the detection coil may be inclined by −45 ° with respect to the axis O of the rotating shaft 10, and the nonmagnetic portion and the ferromagnetic portion of the magnetic ring may be inclined by + 45 ° with respect to the axis O of the rotating shaft 10. .

  FIG. 4 shows a second embodiment of the magnetostrictive torque sensor of the present invention. The magnetostrictive torque sensor of the second embodiment has a rotating shaft 10 having magnetostrictive characteristics. However, unlike the first embodiment, a coil 21 tilted by + 45 ° with respect to the axis O of the rotating shaft 10 (hereinafter simply referred to as “ A magnetic ring 31 wound around (around + 45 ° coil) and a coil 22 tilted at −45 ° with respect to the axis O of the rotating shaft 10 (hereinafter simply referred to as “−45 ° coil”) The wound magnetic rings 32 are respectively concentrically arranged on the rotating shaft 10 through both ends of the rotating shaft 10. Further, one magnetic ring 31 includes a nonmagnetic portion 31a and a ferromagnetic portion 31b (hereinafter simply referred to as “−45 ° nonmagnetic portion” and “−45 °, respectively” inclined by −45 ° with respect to the axis O of the rotating shaft 10, respectively. As shown in FIG. 4, the magnetic ring 31 includes a −45 ° nonmagnetic portion 31 a and a −45 ° ferromagnetic portion 31 b alternately in the circumferential direction. It has an arranged structure. The other magnetic ring 32 includes a non-magnetic portion 32a and a ferromagnetic portion 32b (hereinafter simply referred to as “+ 45 ° non-magnetic portion” and “+ 45 ° ferromagnetic”, respectively) inclined + 45 ° with respect to the axis O of the rotating shaft 10. As shown in FIG. 4, the magnetic ring 32 has a structure in which + 45 ° nonmagnetic portions 32a and + 45 ° ferromagnetic portions 32b are alternately arranged in the circumferential direction. Have. Here, the −45 ° nonmagnetic portion 31a and the + 45 ° nonmagnetic portion 32a desirably have low relative permeability, and the −45 ° ferromagnetic portion 31b and the + 45 ° ferromagnetic portion 32b desirably have high relative permeability. . The number of −45 ° nonmagnetic portions 31a and −45 ° ferromagnetic portions 31b, and + 45 ° nonmagnetic portions 32a and + 45 ° ferromagnetic portions 32b is 4 to 2N (N = 2, 3, 4,...). is there. In order to increase the detection sensitivity of the + 45 ° coil 21 and the −45 ° coil 22, the areas of the −45 ° nonmagnetic portion 31a and the + 45 ° nonmagnetic portion 32a are −45 ° ferromagnetic portion 31b and + 45 ° ferromagnetic portion, respectively. It is preferable that it is smaller than the area of the part 32b.

  Next, the operation of the magnetostrictive torque sensor of FIG. 4 will be described with reference to FIG. When the current I is supplied to the + 45 ° coil 21, the magnetic flux Φ generated by the + 45 ° coil 21 is −45 ° nonmagnetic portion 31a of the magnetic ring 31 (the nonmagnetic portion 31a is weakly magnetized in the −45 ° direction) and −45. The magnetic flux Φ is forced to pass through the rotating shaft 10 by being inclined by −45 ° with respect to the axis O of the rotating shaft 10 as shown in FIG. Therefore, the magnetic flux Φ passing through the rotating shaft 10 is concentrated in the easy magnetization direction + σ direction (tensile direction) and the relative permeability in the tension direction is increased, so that the inductance of the + 45 ° coil 21 is increased. Similarly, when the current I is supplied to the −45 ° coil 22, the magnetic flux Φ generated by the −45 ° coil 22 is the + 45 ° nonmagnetic portion 32a of the magnetic ring 32 (the nonmagnetic portion 32a is weakly magnetized in the + 45 ° direction). Since the magnetic flux passes through the + 45 ° ferromagnetic portion 32b, the magnetic flux Φ is forced to pass through the rotating shaft 10 with an inclination of + 45 ° with respect to the axis O of the rotating shaft 10, as shown in FIG. Therefore, the magnetic flux Φ passing through the rotating shaft 10 is concentrated in the magnetization difficult direction −σ direction (compression direction) and the relative permeability in the compression direction is reduced, so that the inductance of the −45 ° coil 22 is reduced.

FIG. 6 shows a detection circuit for detecting the torque applied to the magnetostrictive rotating shaft 10 from the electrical characteristics of the + 45 ° coil 21 and the −45 ° coil 22 of the second embodiment described above. A bridge circuit as shown in FIG. 6 is configured by using the + 45 ° coil 21 and the −45 ° coil 22 and the two resistors R ₁ and R ₂ (R ₁ = R ₂ = 10Ω). Then, a + 45 ° detection coil 21 and a resistor R ₁ connected in series, an oscillator 70 for driving a circuit is connected to both ends of the −45 ° detection coil 22 and the resistor R ₂ connected in series, and a + 45 ° detection coil. A lock-in that detects and amplifies and outputs a differential signal generated from the bridge circuit when torque is applied between the resistor 21 and the resistor R ₁ and between the -45 ° detection coil 22 and the resistor R ₂ connected in series. An amplifier 80 is connected.

Next, the operation of the detection circuit of FIG. 6 will be described. Flowing high frequency current I + 45 ° detection coil 21 generated from the oscillator 70 and the -45 ° detection coil 22, flows out resistor _{R 1} from the resistor _{R 2.} When torque is not applied, zero point adjustment is performed so that the detection circuit is in an equilibrium state. As shown in FIG. 6, when a positive torque T is applied, the inductance L of the + 45 ° detection coil 21 increases by ΔL, the inductance L of the −45 ° detection coil 22 decreases by ΔL, and the output from the lock-in amplifier 80. V increases in the positive direction. On the other hand, when a negative torque is applied, the inductance L of the + 45 ° detection coil 21 decreases by ΔL, the inductance L of the −45 ° detection coil 22 increases by ΔL, and the output V from the lock-in amplifier 80 is in the negative direction. To decrease. From this, the direction and magnitude of the torque T are detected.

According to the detection circuit of FIG. 6, noise is removed by the lock-in amplifier 80 by balancing the bridge circuit of the + 45 ° coil 21 and the −45 ° coil 22 and the two resistors R ₁ and R _2. Therefore, stable and accurate zero point adjustment can be easily performed, and the sensitivity of the output voltage can be increased.

  Further, according to the structure of the magnetostrictive torque sensor of the second embodiment, the magnetic flux Φ generated by the + 45 ° coil 21 and the −45 ° coil 22 is concentrated in the −45 ° direction and the + 45 ° direction, respectively. Sensitivity can be increased. Since the + 45 ° coil 21 and the −45 ° coil 22 are wound around the magnetic rings 31 and 32 respectively and are rotationally symmetric with respect to the magnetostrictive rotating shaft 10, the output signal is at the rotational angle of the magnetostrictive rotating shaft 10. There is no dependence. That is, the zero point fluctuation of the output signal accompanying the rotation of the magnetostrictive rotating shaft 10 can be reduced.

  FIG. 7A shows a half in which coils 21 (hereinafter simply referred to as “+ 45 ° coils”) inclined by + 45 ° with respect to the axis O (not shown) of the rotary shaft 10 having magnetostrictive characteristics are wound. A third embodiment of the magnetostrictive torque sensor according to the present invention in which cylindrical magnetic core pairs 41 and 41 are mounted on the magnetostrictive rotating shaft 10 will be described. Here, each of the semi-cylindrical magnetic cores 41 and 41 includes a non-magnetic portion 41a and a ferromagnetic portion 41b (hereinafter simply referred to as “a”) inclined by −45 ° with respect to the axis O (not shown) of the rotating shaft 10 having magnetostrictive characteristics. It is made of a composite magnetic material having both “−45 ° nonmagnetic part” and “−45 ° ferromagnetic part”. FIG. 7B is a partially enlarged plan view seen from a direction perpendicular to the axis of the semi-cylindrical core pairs 41 and 41 including the −45 ° cut portion 41A in the −45 ° nonmagnetic portion 41a of FIG. In the third embodiment, unlike the first embodiment, the cutting direction of the magnetic ring is the same as the tilting direction of the −45 ° nonmagnetic portion 41a and the −45 ° ferromagnetic portion 41b as shown by the cutting portion 41A. As shown in the figure, the semi-cylindrical magnetic cores 41 and 41 are divided by the −45 ° nonmagnetic part 41a on the diameter. The + 45 ° coil 21 is orthogonal to the −45 ° nonmagnetic portion 41a and the −45 ° ferromagnetic portion 41b from each of the two semi-cylindrical magnetic cores 41 and 41 from the 45 ° corner of one cut end surface thereof. Then, wrap up to the 45 ° corner of the other cut end face. The two semi-cylindrical magnetic cores 41 and 41 are arranged concentrically and closely around the magnetostrictive rotating shaft 10 to constitute a magnetostrictive torque sensor.

  The operation principle of the magnetostrictive torque sensor in FIG. 7 is the same as the operation principle described in FIG.

FIG. 8 shows a detection circuit for detecting the torque applied to the magnetostrictive rotating shaft 10 from the electrical characteristics of the two + 45 ° coils 21 and 21 of the third embodiment. A bridge circuit as shown in FIG. 8 is configured by using two + 45 ° coils 21 and 21 and two resistors R ₁ and R ₂ (R ₁ = R ₂ = 10Ω). Then, two + 45 ° coils 21 and 21 connected in series and an oscillator 70 for driving a circuit are connected to both ends of the series connected resistors R ₁ and R _2, and between the two + 45 ° coils 21 connected in series. The lock-in amplifier 80 is connected between the series-connected resistors R ₁ and R ₂ for detecting and amplifying a differential signal generated from the bridge circuit when torque is applied.

Next, the operation of the detection circuit of FIG. 8 will be described. High frequency current I generated from the oscillator 70 flows to the upper of + 45 ° detection coil 21 to the resistor R _1, flows out below the + 45 ° detection coil 21 from the resistor R _2. When torque is not applied, zero point adjustment is performed so that the detection circuit is in an equilibrium state. As shown in FIG. 8, when a positive torque T is applied, the inductance L of the upper + 45 ° detection coil 21 increases by ΔL, and the inductance L of the lower + 45 ° detection coil 21 decreases by ΔL. The output V from 80 increases in the positive direction. On the other hand, when a negative torque is applied, the inductance L of the upper + 45 ° detection coil 21 decreases by ΔL, the inductance L of the lower + 45 ° detection coil 21 increases by ΔL, and the output from the lock-in amplifier 80 V decreases in the negative direction. From this, the direction and magnitude of the torque T are detected.

According to the detection circuit of FIG. 8, noise is further removed by the lock-in amplifier 80 by balancing the bridge circuit of the two + 45 ° coils 21 and 21 and the two resistors R ₁ and R _2. Therefore, stable and accurate zero point adjustment can be easily performed, and the sensitivity of the output voltage can be increased.

  Furthermore, according to the structure of the magnetostrictive torque sensor of the third embodiment, since the magnetic flux Φ generated by the two + 45 ° coils 21 and 21 connected in series is concentrated in the −45 ° direction, the sensitivity of the output signal is increased. can do. Further, since the two + 45 ° coils 21 and 21 connected in series function in the same manner as the ring-shaped axial rotation symmetry detection coil with respect to the magnetostrictive rotating shaft 10 as in the first embodiment, they are the same as in the first embodiment. The output signal does not depend on the rotation angle of the magnetostrictive rotating shaft 10 because it is rotationally symmetric with respect to the magnetostrictive rotating shaft 10. That is, the zero point fluctuation of the output signal accompanying the rotation of the magnetostrictive rotating shaft 10 can be reduced. Moreover, since the magnetostrictive torque sensor of the third embodiment is divided into two semi-cylindrical cores 41, 41, the magnetostrictive torque sensor can be easily attached to the magnetostrictive rotating shaft 10 as compared with the first embodiment.

  FIG. 9 shows a fourth embodiment of the magnetostrictive torque sensor of the present invention. In the fourth embodiment, as in the third embodiment, the magnetic rings 31 and 32 of the second embodiment are each −45 on the diameter as indicated by the −45 ° cut portion 41A and the + 45 ° cut portion 42A. At the positions of the nonmagnetic portion 41a and the + 45 ° nonmagnetic portion 42a, two semi-cylindrical magnetic core pairs 41, 41 and 42, 42 are formed along the inclination direction of the −45 ° nonmagnetic portion 41a and the + 45 ° nonmagnetic portion 42a. Dividing and winding the + 45 ° coils 21 and 21 and the −45 ° coils 22 and 22 around the semi-cylindrical cores 41, 41 and 42, 42, respectively.

  The operation principle of the magnetostrictive torque sensor in FIG. 9 is the same as the operation principle described in FIG.

  FIG. 10 is a detection circuit for detecting the torque applied to the magnetostrictive rotating shaft 10 from the electrical characteristics of the two + 45 ° coils 21 and 21 and the two −45 ° coils 22 and 22 of the fourth embodiment. is there. A bridge circuit as shown in FIG. 10 is configured by using the two + 45 ° coils 21 and 21 and the two −45 ° coils 22 and 22. Then, two series-connected + 45 ° coils 21 and 21 and two series-connected −45 ° coils 22 and 22 are connected to an oscillator 70 for driving the circuit, and two series-connected + 45 ° detections are made. A lock-in amplifier 80 that detects and amplifies and outputs a differential signal generated from the bridge circuit when torque is applied is connected between the coils 21 and 21 and between the two -45 ° coils 22 and 22 connected in series. To do.

  Next, the operation of the detection circuit of FIG. 10 will be described. The high frequency current I generated from the oscillator 70 flows into the upper + 45 ° detection coil 21 and −45 ° detection coil 22 and flows out from the lower + 45 ° detection coil 21 and −45 ° detection coil 22. When torque is not applied, zero point adjustment is performed so that the detection circuit is in an equilibrium state. As shown in FIG. 10, when a positive torque T is applied, the inductance L of the + 45 ° detection coil 21 on the upper left side and the −45 ° detection coil 22 on the lower right side increases by ΔL, and + 45 ° detection on the lower left side is detected. The inductance L of the coil 21 and the −45 ° detection coil 22 on the upper right side decreases by ΔL, and the output V from the lock-in amplifier 80 increases in the positive direction. On the other hand, when a negative torque is applied, the inductance L of the + 45 ° detection coil 21 on the upper left side and the −45 ° detection coil 22 on the lower right side decreases by ΔL, and the + 45 ° detection coil 21 on the lower left side and the upper right side. In this case, the inductance L of the −45 ° detection coil 22 increases by ΔL, and the output V from the lock-in amplifier 80 decreases in the negative direction. From this, the direction and magnitude of the torque T are detected.

  According to the detection circuit of FIG. 10, noise is removed by the lock-in amplifier 80 by balancing the bridge circuit of the two + 45 ° coils 21 and 21 and the two −45 ° coils 22 and 22. Thus, stable and accurate zero point adjustment can be easily performed, and the sensitivity of the output voltage can be increased.

  Furthermore, according to the structure of the magnetostrictive torque sensor of the fourth embodiment, the magnetic fluxes Φ generated by the two + 45 ° coils 21 and 21 connected in series and the −45 ° coils 22 and 22 connected in series are respectively Since the concentration is in the −45 ° direction and the + 45 ° direction, the sensitivity of the output signal can be increased. Further, the two + 45 ° coils 21 and 21 connected in series and the two −45 ° coils 22 and 22 connected in series are detected by the ring-shaped axis rotation symmetry with respect to the magnetostrictive rotation axis 10 as in the second embodiment. Since it functions in the same manner as the coil, it is rotationally symmetric with respect to the magnetostrictive rotating shaft 10 as in the second embodiment, so that the output signal does not depend on the rotational angle of the magnetostrictive rotating shaft 10. That is, the zero point fluctuation of the output signal accompanying the rotation of the magnetostrictive rotating shaft 10 can be reduced. Moreover, since the magnetostrictive torque sensor of the fourth embodiment is divided into two semi-cylindrical magnetic cores 41, 41 and 42, 42, it can be easily attached to the magnetostrictive rotating shaft 10 as compared with the second embodiment. . Furthermore, since there are four detection coils, the connection of the bridge circuit of the detection coil is easy, and the bridge circuit can be assembled without requiring an external circuit.

1 shows a first embodiment of a magnetostrictive torque sensor of the present invention. It is a schematic diagram which shows the operation | movement principle of the magnetostrictive torque sensor of FIG. 2 is a detection circuit for detecting torque applied to a magnetostrictive rotating shaft by the magnetostrictive torque sensor of FIG. 1. 2 shows a second embodiment of the magnetostrictive torque sensor of the present invention. It is a schematic diagram which shows the operation | movement principle of the magnetostrictive torque sensor of FIG. 5 is a detection circuit for detecting torque applied to the magnetostrictive rotating shaft by the magnetostrictive torque sensor of FIG. 4. (A) shows a third embodiment of a magnetostrictive torque sensor according to the present invention in which a pair of semi-cylindrical magnetic cores each wound with a + 45 ° coil is mounted on a magnetostrictive rotating shaft. (B) is the elements on larger scale seen from the direction perpendicular | vertical to the axis | shaft of the semi-cylindrical magnetic core pair containing the -45 degree cut part in the -45 degree nonmagnetic part of (a). 8 is a detection circuit for detecting torque applied to the magnetostrictive rotating shaft by the magnetostrictive torque sensor of FIG. FIG. 10 is a schematic diagram of a magnetostrictive torque sensor having two semi-cylindrical magnetic core pairs mounted on a magnetostrictive rotating shaft according to a fourth embodiment of the present invention. 10 is a detection circuit for detecting torque applied to the magnetostrictive rotating shaft by the magnetostrictive torque sensor of FIG. 9. (A) And (b) is the schematic of the conventional magnetostrictive torque sensor, respectively.

Explanation of symbols

10 Magnetostrictive rotating shaft 21 + 45 ° coil 22 −45 ° coil 31, 32 Magnetic rings 41, 42 Semi-cylindrical magnetic core 31a, 41a −45 ° nonmagnetic part 31b, 41b −45 ° ferromagnetic part 32a, 42a + 45 ° nonmagnetic part 32b, 42b + 45 ° ferromagnetic part 41A, 42A cutting part 70 oscillator 80 lock-in amplifier

Claims (5)

A rotating shaft having magnetostrictive characteristics that rotates around a central axis, and a coil that is arranged coaxially with the rotating shaft while having a predetermined distance from the outer periphery of the rotating shaft, is wound. In a magnetostrictive torque sensor with a magnetic ring,
The magnetic ring is formed of a ferromagnetic portion and a non-magnetic portion that are alternately arranged in a circumferential direction inclined by 45 ° with respect to the central axis,
The magnetostrictive torque sensor according to claim 1, wherein the coil is wound in a direction orthogonal to an inclination direction of the ferromagnetic portion and the nonmagnetic portion. In order to detect a change in magnetic flux in the tension direction of the rotating shaft, the magnetic ring is inclined in the tension direction of the rotating shaft and alternately arranged in the circumferential direction and tension detecting ferromagnetic portions. In order to detect a change in magnetic flux in the compression direction of the rotating shaft, the first magnetic ring formed from a non-magnetic portion is alternately arranged in the circumferential direction inclining in the compressing direction of the rotating shaft. A second magnetic ring formed from a compression detecting ferromagnetic portion and a compression detecting non-magnetic portion;
The coil includes a first coil wound around the first magnetic ring in a compression direction, and a second coil wound around the second magnetic ring in a tension direction. The magnetostrictive torque sensor according to claim 1, further comprising:   The magnetostrictive torque sensor according to claim 1, wherein the magnetic ring has an area of the nonmagnetic portion smaller than an area of the ferromagnetic portion.   The said magnetic ring contains the semi-cylindrical magnetic core divided into 2 along the inclination direction of the said nonmagnetic part in the position of the said nonmagnetic part, The Claim 1 characterized by the above-mentioned. Magnetostrictive torque sensor.   5. The magnetostrictive torque sensor according to claim 4, wherein a coil is wound independently on each of the two half-cylindrical magnetic cores.

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