JP2019211335A - Magnetostrictive torque sensor having rotating angle detection function - Google Patents

Abstract

To reduce the size of a sensor capable of detecting both the rotation angle and torque of the shaft.SOLUTION: The device includes: a shaft (10); a first magnetostrictive portion (11) and a second magnetostriction portion (12) having a magnetic anisotropic in the opposite direction to each other disposed at least along the outer periphery of the shaft (10) with a magnetostrictive portion in which the radial distance from the outer peripheral surface is non-circular and the radius distance from the shaft center axis (J) changes periodically in the circumferential direction; a first ejection magnetic pole (13a) arranged adjacently to the first magnetostrictive portion (11); a second ejection magnetic pole (14a) arranged adjacently arranged the second magnetostriction portion (12); a first detection coil (15) wound around the first detection coil (13a); and a second detection coil (16) wound around the second ejection magnetic pole (14a). It is possible to detect the rotation angle and torque of the shaft (10) based on a first detection signal (S1) obtained by the first detection coil (15) and a second detection signal(S2) obtained by the second detection coil (16).SELECTED DRAWING: Figure 1

Description

  The present invention relates to a magnetostrictive torque sensor having a rotation angle detection function.

  Generally, when a shaft is rotated, a function for detecting torque applied to the shaft and a function for detecting a rotation angle of the shaft may be required. Therefore, Patent Document 1 describes a technique in which a rotation angle sensor for detecting a rotation angle of a shaft is attached and a non-contact magnetostrictive torque sensor is disposed on the shaft in the vicinity of the angle sensor.

JP 2008-76066 A

  However, the technique described in Patent Document 1 has a problem in that the size of the entire sensor increases because the rotation angle sensor and the torque sensor have different structures.

  The present invention has been made in order to solve the above-described problems, and an object of the present invention is to provide a magnetostrictive type having a rotation angle detection function capable of downsizing a sensor capable of detecting both the rotation angle and torque of the shaft. It is to provide a torque sensor.

  The present invention provides a shaft and a magnetostrictive portion which is disposed on at least the outer periphery of the shaft, has a non-circular cross-sectional shape on the outer peripheral surface, and a radial distance from the shaft central axis periodically changes in the circumferential direction. A first magnetostrictive portion and a second magnetostrictive portion having magnetic anisotropies in opposite directions, a first projecting magnetic pole disposed in proximity to the first magnetostrictive portion, and in proximity to the second magnetostrictive portion. The second projecting magnetic pole arranged in the first direction, the first detection coil wound around the first projecting magnetic pole, and the same as the first detection coil in the circumferential direction while being wound around the second projecting magnetic pole. A rotation angle of the shaft based on a first detection signal obtained by the first detection coil and a second detection signal obtained by the second detection coil. Torque can be detected, A magnetostrictive torque sensor comprising a rotation angle detection function.

  In addition, the magnetostrictive torque sensor according to the present invention obtains the rotation angle of the shaft based on the sum of the first detection signal and the second detection signal, and calculates the first detection signal and the second detection signal. A signal processing unit for obtaining a torque applied to the shaft based on the difference is further provided.

  According to the present invention, it is possible to reduce the size of a sensor that can detect both the rotation angle and torque of the shaft.

It is a sectional side view which shows the structural example of the principal part of the magnetostrictive torque sensor which concerns on embodiment of this invention. It is a figure explaining the cross-sectional shape of a shaft. It is a figure which shows the relationship between the rotation angle of a shaft, and the impedance of a coil. It is a figure which shows the relationship between the torque added to a shaft, and the impedance of a coil. It is a figure explaining a signal processing part.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a side sectional view showing a configuration example of a main part of a magnetostrictive torque sensor according to an embodiment of the present invention.
The magnetostrictive torque sensor 1 is a torque sensor having a rotation angle detection function, and includes a shaft 10, a first magnetostrictive film 11 as a first magnetostrictive section, a second magnetostrictive film 12 as a second magnetostrictive section, A single annular stator core 13, a second annular stator core 14, a first detection coil 15, and a second detection coil 16 are provided.

The shaft 10 is a metal shaft and has a cross-sectional shape as shown in FIG. FIG. 2 shows a shape when the shaft 10 is sectioned in a direction orthogonal to the shaft central axis J.
As can be seen from FIG. 2, the cross-sectional shape of the shaft 10 is a non-circular shape, and the radial distance from the shaft central axis (hereinafter, also simply referred to as “central axis”) J is periodically in the circumferential direction. It has changed. Specifically, in the circumferential direction around the central axis J of the shaft 10, a convex cross-sectional shape portion 10a having a radial distance from the central axis J having a maximum distance Ra and a concave cross-section having a minimum distance Rb. The shape portion 10b exists. The cross-sectional shape portions 10 a and the cross-sectional shape portions 10 b are alternately arranged at 45 ° intervals in the circumferential direction of the shaft 10. Further, the radial distance from the central axis J continuously changes between the cross-sectional shape portion 10a and the cross-sectional shape portion 10b.

  The shaft 10 shown in FIG. 1 is a shaft that faces at least the first annular stator core 13, the second annular stator core 14, the first detection coil 15, and the second detection coil 16 in the shaft central axis direction (vertical direction in FIG. 1). The portion has a non-circular cross-sectional shape as shown in FIG. Therefore, the cross-sectional shape of the shaft portion that does not face the first annular stator core 13 or the like may be a perfect circle. In the present embodiment, as an example, it is assumed that the cross-sectional shape of the portion of the shaft 10 in the range shown in FIG. 1 is uniformly as shown in FIG. For this reason, in the following description, the shaft portion including the shaft portion having a non-circular circular cross-sectional shape is referred to as the shaft 10.

  The first magnetostrictive film 11 is formed on the outer periphery of the shaft 10 so as to cover the outer peripheral surface of the shaft 10 over the entire periphery. The first magnetostrictive film 11 is formed with a uniform thickness over the entire circumference of the shaft 10 in the circumferential direction. Therefore, the first magnetostrictive film 11 covers the shaft 10 following the shaft cross-sectional shape so as to be similar to the above-described shaft cross-sectional shape. Therefore, the cross-sectional shape of the outer peripheral surface of the first magnetostrictive film 11 is non-circular like the outer peripheral surface of the shaft 10 and the radial distance from the shaft center axis (J) changes periodically in the circumferential direction. Yes. The first magnetostrictive film 11 is previously provided with magnetic anisotropy in a predetermined direction.

  The second magnetostrictive film 12 is formed at a position adjacent to the first magnetostrictive film 11 in the shaft central axis J direction. The second magnetostrictive film 12 is formed on the outer periphery of the shaft 10 so as to cover the outer peripheral surface of the shaft 10 over the entire periphery. The thickness of the second magnetostrictive film 12 is equal to the thickness of the first magnetostrictive film 11 and is uniform over the entire circumference of the shaft 10 in the circumferential direction. Therefore, the second magnetostrictive film 12 covers the shaft 10 following the shaft cross-sectional shape so as to be similar to the shaft cross-sectional shape described above. Therefore, the cross-sectional shape of the outer peripheral surface of the second magnetostrictive film 12 is non-circular like the outer peripheral surface of the shaft 10, and the radial distance from the shaft central axis (J) is periodically changed in the circumferential direction. Yes.

  The second magnetostrictive film 12 is previously provided with magnetic anisotropy. The second magnetostrictive film 12 is provided with magnetic anisotropy in the direction opposite to the first magnetostrictive film 11 with respect to the shaft center axis J. In the present embodiment, as one preferable example, the first magnetostrictive film 11 is provided with magnetic anisotropy at an inclination angle of 45 ° on one side with respect to the shaft center axis J, and the second magnetostrictive film 12 is Is provided with magnetic anisotropy at an inclination angle of 45 ° on the other side with respect to the shaft central axis J. The first magnetostrictive film 11 and the second magnetostrictive film 12 can be formed on the outer peripheral surface of the shaft 10 by, for example, plating using a magnetostrictive material.

  The first annular stator core 13 is disposed around the shaft 10. The first annular stator core 13 is formed in an annular shape so as to surround the shaft 10. The first annular stator core 13 is disposed so as to be close to and opposed to the first magnetostrictive film 11 through a predetermined gap. The first annular stator core 13 is provided with a plurality of teeth 13a. Each of the plurality of teeth 13a constitutes a first protruding magnetic pole. The plurality of teeth 13 a are arranged at predetermined angular intervals in the circumferential direction of the first annular stator core 13. Each of the teeth 13a is provided so as to protrude from the core body of the first annular stator core 13 inward (to the shaft central axis J side). Further, the protruding end of each tooth 13a is close to and faces the first magnetostrictive film 11 through a predetermined gap.

  The second annular stator core 14 is disposed around the shaft 10 at a position different from the first annular stator core 13 in the shaft central axis J direction. Specifically, the first annular stator core 13 is disposed above the boundary between the first magnetostrictive film 11 and the second magnetostrictive film 12, and the second stator core 14 is formed between the first magnetostrictive film 11 and the second magnetostrictive film 12. It is arranged below the boundary. The second annular stator core 14 is formed in an annular shape so as to surround the shaft 10. The second annular stator core 14 is disposed so as to be close to and opposed to the second magnetostrictive film 12 through a predetermined gap. The second annular stator core 14 is provided with a plurality of teeth 14a. Each of the plurality of teeth 14a constitutes a second protruding magnetic pole. The same number of teeth 14a as the teeth 13a are provided. The plurality of teeth 14 a are arranged at predetermined angular intervals in the circumferential direction of the second annular stator core 14. Further, the plurality of teeth 14a are arranged at the same position (same phase) as the plurality of teeth 13a described above in the circumferential direction. Each of the teeth 14a is provided so as to protrude from the core body of the second annular stator core 14 inward (to the shaft central axis J side). Further, the protruding end of each tooth 14a is close to and faces the second magnetostrictive film 12 through a predetermined gap. Further, the separation distance from the shaft center axis J to the inner end portion of each tooth 14a is set equal to the separation distance from the shaft center axis J to the inner end portion of each tooth 13a.

  The first detection coil 15 is wound around a predetermined part of the first annular stator core 13. Each tooth 13 a of the first annular stator core 13 is covered with an insulating member 17, and the first detection coil 15 is wound around each tooth 13 a via the insulating member 17. A first excitation coil 18 is wound around each tooth 13 a of the first annular stator core 13 together with the first detection coil 15.

  The second detection coil 16 is wound around a predetermined portion of the second annular stator core 14. Each tooth 14 a of the second annular stator core 14 is covered with an insulating member 19, and the second detection coil 16 is wound around each tooth 14 a via the insulating member 19. A second excitation coil 20 is wound around each tooth 14 a of the second annular stator core 14 together with the second detection coil 16. Here, the teeth 13a forming the first protruding magnetic pole and the teeth 14a forming the second protruding magnetic pole are arranged at the same position in the circumferential direction. For this reason, the first detection coil 15 wound around the tooth 13a and the second detection coil 16 wound around the tooth 14a are also arranged at the same position in the circumferential direction and are wound around the tooth 13a. The 1 excitation coil 18 and the 2nd excitation coil 20 wound by the teeth 14a are also arrange | positioned in the mutually same position in the circumferential direction.

  The set of the first annular stator core 13 and the first detection coil 15 and the combination of the second annular stator core 14 and the second detection coil 16 having the above-described configuration are the first excitation coil 18 and the second excitation coil 20 belonging to the respective groups. Including the same characteristics both electrically and magnetically.

  The magnetostrictive torque sensor 1 according to the present embodiment includes a bearing 25, a housing 26, and an example of a configuration for holding the first annular stator core 13 and the second annular stator core 14 in addition to the components described above. The spacer 27 and the pressing member 28 are provided.

  The bearing 25 is attached to the housing 26. The inner ring side of the bearing 25 is fitted to the shaft 10, and the bearing 25 rotatably supports the shaft 10 in this fitted state.

  The housing 26 is formed in a cylindrical shape as a whole. The first annular stator core 13 and the second annular stator core 14 are attached to the inside of the housing 26 using a spacer 27 and a pressing member 28. The first annular stator core 13 and the second annular stator core 14 are fixed together with the housing 16, while the shaft 10 is rotatably supported by a bearing 25 inside the housing 16.

  A step portion 26 a is formed on the inner peripheral side of the housing 26. The first annular stator core 13 is abutted against the step portion 26 a of the housing 26. The spacer 27 is formed in an annular shape. The spacer 27 is disposed between the first annular stator core 13 and the second annular stator core 14 in the shaft central axis J direction.

  The upper part of the pressing member 28 is inserted into the housing 26 from the side opposite to the bearing 25. Inside the housing 16, the end 28 a of the pressing member 28 is abutted against the second annular stator core 14 from the side opposite to the spacer 27. Thereby, inside the housing 26, the first annular stator core 13 is sandwiched between the step portion 26 a of the housing 26 and the spacer 27, and the second annular stator core is interposed between the end portion 28 a of the pressing member 28 and the spacer 27. 14 is sandwiched. In the shaft central axis J direction, the distance between the first annular stator core 13 and the second annular stator core 14 is uniquely determined by the spacer 27. That is, the spacer 27 functions as a positioning member that positions the first annular stator core 13 and the second annular stator core 14 in the shaft central axis J direction. The pressing member 28 functions as a misalignment prevention member that prevents misalignment of the first annular stator core 13 and the second annular stator core 14 about the shaft center axis J. A gap (not shown) is formed between the inner peripheral surface of the pressing member 28 and the outer surface of the second magnetostrictive film 12, whereby the pressing member 28 and the second magnetostrictive film 12 are arranged in a non-contact manner.

Next, the operation of the magnetostrictive torque sensor 1 having the above configuration and the detection of the rotation angle and torque of the shaft 10 will be described.
First, when the shaft 10 rotates, the gap between the first annular stator core 13 and the first magnetostrictive film 11 (hereinafter referred to as “first gap”), the second annular stator core 14, the second magnetostrictive film 12, and the like. (Hereinafter referred to as “second gap”) periodically changes as the shaft 10 rotates. Specifically, with respect to the first annular stator core 13, when the cross-sectional shape portion 10a of the shaft 10 faces the teeth 13a, the first gap is minimized, and the cross-sectional shape portion 10b of the shaft 10 faces the teeth 13a. Sometimes the first gap is maximal. Similarly, regarding the second annular stator core 14, when the cross-sectional shape portion 10a of the shaft 10 faces the teeth 14a, the second gap is minimized, and when the cross-sectional shape portion 10b of the shaft 10 faces the teeth 14a. The second gap is maximized.

  Therefore, when an alternating current having the same phase is supplied to the first excitation coil 18 and the second excitation coil 20, the level of the signal output from the first detection coil 15 and the second detection coil 16 is in accordance with the rotation of the shaft 10. Due to the change of the gap and the change of the magnetic permeability depending on the size of the gap, it changes periodically like a sine curve. This means that the radial distance defining the cross-sectional shape of the shaft 10 shown in FIG. 2 continuously changes with periodicity like a sine curve.

Thereby, the impedance of the first detection coil 15 wound around the first annular stator core 13 and the impedance of the second detection coil 16 wound around the second annular stator core 14 are shown in accordance with the rotation angle of the shaft 10. It changes like 3.
In FIG. 3, the vertical axis represents the impedance, the horizontal axis represents the rotation angle of the shaft, the impedance of the first detection coil 15 is indicated by Z1, and the impedance of the second detection coil 16 is indicated by Z2.

  As can be seen from FIG. 3, the impedance Z <b> 1 of the first detection coil 15 and the impedance Z <b> 2 of the second detection coil 16 show the same changes according to the rotation angle of the shaft 10. For this reason, with respect to the rotation of the shaft 10, the difference (Z1-Z2) between the impedance Z1 of the first detection coil 15 and the impedance Z2 of the second detection coil 16 is always a constant value (zero). On the other hand, the sum (Z1 + Z2) of the impedance Z1 of the first detection coil 15 and the impedance Z2 of the second detection coil 16 is twice the value of the respective impedance Z1 or Z2. Therefore, the impedance difference (Z1−Z2) does not change with respect to the change in the rotation angle of the shaft 10, and the sum of the impedances (Z1 + Z2) is equal to 2 of the impedance Z1 or Z2 in the same cycle as the impedance Z1 or Z2. It changes with double value. That is, the change in the rotation angle of the shaft 10 does not appear as a change in the impedance difference (Z1−Z2) but only as a change in the sum of impedances (Z1 + Z2).

  On the other hand, when torsional torque is applied to the shaft 10, the first magnetostrictive film 11 and the second magnetostrictive film 12 are distorted. Then, the magnetic permeability of the first magnetostrictive film 11 and the second magnetostrictive film 12 changes due to the barrier effect. Specifically, when a torque in the first direction is applied to the shaft 10, the magnetic permeability of the first magnetostrictive film 11 increases and the magnetic permeability of the second magnetostrictive film 12 decreases. Further, when a torque in the second direction, that is, the direction opposite to the first direction is applied to the shaft 10, the magnetic permeability of the first magnetostrictive film 11 decreases and the magnetic permeability of the second magnetostrictive film 12 increases.

Therefore, the impedance of the first detection coil 15 wound around the first annular stator core 13 and the impedance of the second detection coil 16 wound around the second annular stator core 14 are shown in accordance with the input torque applied to the shaft 10. 4 will change.
In FIG. 4, the vertical axis represents impedance, the horizontal axis represents input torque to the shaft 10, the impedance of the first detection coil 15 is indicated by Z1, and the impedance of the second detection coil 16 is indicated by Z2. Further, regarding the numerical value of the input torque, the numerical value of the torque when the input torque is applied in one direction is represented by plus, and the numerical value of the torque when applied in the other direction is represented by minus.

  As can be seen from FIG. 4, the impedance Z <b> 1 of the first detection coil 15 and the impedance Z <b> 2 of the second detection coil 16 show different changes with respect to the input torque to the shaft 10. Specifically, the impedance Z1 of the first detection coil 15 increases when the input torque is applied in one direction (positive side) and decreases when the input torque is applied in the other direction (negative side). On the other hand, the impedance Z2 of the second detection coil 16 decreases when the input torque is applied in one direction and increases when the input torque is applied in the other direction.

  Impedances Z1 and Z2 change with the same gradient as the input torque changes, and take the same value when no torque is applied to the shaft 10, that is, when the input torque is zero. For this reason, regarding the torque applied to the shaft 10, the sum (Z1 + Z2) of the impedance Z1 of the first detection coil 15 and the impedance Z2 of the second detection coil 16 is always a constant value. On the other hand, the difference (Z1−Z2) between the impedance Z1 of the first detection coil 15 and the impedance Z2 of the second detection coil 16 is twice the value of each impedance Z1 or Z2. Therefore, the sum of impedance (Z1 + Z2) does not change with respect to the change in torque applied to the shaft 10, and the difference in impedance (Z1-Z2) is uniform with a gradient twice that of impedance Z1 or Z2. Change. That is, the change in the input torque to the shaft 10 does not appear as a change in the sum of impedance (Z1 + Z2), but only as a change in the impedance difference (Z1−Z2).

  Here, the first detection signal S1 obtained by the first detection coil 15 and the second detection signal S2 obtained by the second detection coil 16 are taken into the signal processing unit 30 as shown in FIG. The first detection signal S1 may be a signal whose signal level changes according to the change in the impedance Z1 of the first detection coil 15, and the second detection signal S2 corresponds to the change in the impedance Z2 of the second detection coil 16. Any signal whose signal level changes can be used. As an example, the detection voltage output from the first detection coil 15 can be used as the first detection signal S1, and the detection voltage output from the second detection coil 16 can be used as the second detection signal S2.

  The signal processing unit 30 has an arithmetic function for adding or subtracting signals and a function for amplifying signals. The signal processing unit 30 obtains the rotation angle of the shaft 10 and the torque applied to the shaft 10 by using the first detection signal S1 and the second detection signal S2 taken in. Specifically, the signal processing unit 30 obtains the rotation angle θ of the shaft 10 based on the sum of the first detection signal S1 and the second detection signal S2, that is, the addition value, and the first detection signal S1 and the second detection signal S2. The torque T applied to the shaft 10 is obtained based on the difference between the detection signals S2, that is, the subtraction value. In this case, the sum of the first detection signal S1 and the second detection signal S2 reflects the rotation angle of the shaft 10. For this reason, the rotation angle of the shaft 10 can be detected based on the same principle as the rotation angle detection in the known VR resolver. On the other hand, the difference between the first detection signal S1 and the second detection signal S2 reflects the torque applied to the shaft 10. For this reason, the torque applied to the shaft 10 can be detected by the same principle as the torque detection in the known magnetostrictive torque sensor. The signal processing unit 30 outputs the information about the rotation angle θ and the torque T of the shaft 10 thus obtained to, for example, a motor control circuit (not shown).

<Effect of embodiment>
As described above, according to the embodiment of the present invention, the rotation angle and torque of the shaft 10 using the first annular stator core 13, the second annular stator core 14, the first detection coil 15, the second detection coil 16, and the like. Both can be detected by one magnetostrictive torque sensor 1. In addition, the size of the entire sensor can be reduced as compared with the case where the rotation angle sensor and the torque sensor have different structures. Further, the number of parts can be reduced and the space required for sensor mounting can be saved.

<Modifications>
The technical scope of the present invention is not limited to the above-described embodiments, but includes forms to which various changes and improvements are added within the scope of deriving specific effects obtained by constituent elements of the invention and combinations thereof.

  For example, in the said embodiment, although the cross-sectional shape of the shaft which arranged four cross-sectional shape parts 10a and four cross-sectional shape parts 10b on the periphery of the shaft 10 was shown, this invention is not restricted to this, A cross-sectional shape part There may be at least two 10a and two cross-sectional shape portions 10b. Further, the shaft cross-sectional shape including two cross-sectional shape portions 10a and two cross-sectional shape portions 10b is an ellipse or a similar shape.

  In the above embodiment, an example in which the first annular stator core 13 is provided with a plurality of teeth 13a and the second annular stator core 14 is provided with a plurality of teeth 14a has been described. However, the present invention is not limited thereto, and the teeth 13a One tooth 14a may be provided.

  In the above embodiment, the first magnetostrictive portion and the second magnetostrictive portion are coated on the outer peripheral surface of the shaft by plating. However, the present invention is not limited to this, and the shaft may be directly formed of a magnetostrictive material. Good. Alternatively, the magnetostrictive portion may be disposed on the outer periphery of the shaft by press-fitting a magnetostrictive material having magnetic anisotropy in a preliminarily shaped shape into the shaft.

  DESCRIPTION OF SYMBOLS 1 Magnetostrictive type torque sensor, 10 shaft, 11 1st magnetostrictive film (1st magnetostrictive part), 12 2nd magnetostrictive film (2nd magnetostrictive part), 13 1st annular stator core, 14 2nd annular stator core, 15 1st detection coil , 16 Second detection coil, 30 Signal processing unit.

Claims (2)

A shaft (10);
The magnetostrictive portion is disposed on at least the outer periphery of the shaft (10), has a non-circular cross-sectional shape on the outer peripheral surface, and has a radial distance from the shaft central axis (J) that periodically changes in the circumferential direction. A first magnetostrictive portion (11) and a second magnetostrictive portion (12) having magnetic anisotropies in opposite directions,
A first projecting magnetic pole (13a) disposed close to the first magnetostrictive portion (11);
A second projecting magnetic pole (14a) disposed close to the second magnetostrictive portion (12);
A first detection coil (15) wound around the first protruding magnetic pole (13a);
A second detection coil (16) wound around the second protruding magnetic pole (14a) and disposed at the same position as the first detection coil (15) in the circumferential direction;
With
The rotation angle of the shaft (10) based on the first detection signal (S1) obtained by the first detection coil (15) and the second detection signal (S2) obtained by the second detection coil (16). And a magnetostrictive torque sensor with a rotation angle detection function.   Based on the sum of the first detection signal (S1) and the second detection signal (S2), the rotation angle of the shaft (10) is obtained, and the first detection signal (S1) and the second detection signal ( The magnetostrictive torque sensor having a rotation angle detection function according to claim 1, further comprising a signal processing unit (30) for obtaining a torque applied to the shaft (10) based on a difference of S2).

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