Magnetostrictive torque sensor

Abstract

This magnetostrictive torque sensor offers enhanced reliability through redundancy while minimizing the need for additional installation space, resulting in a highly mountable sensor. [Solution] The magnetostrictive torque sensor 1, which is mounted around a rotating shaft 5 having a magnetostrictive effect and detects the torque transmitted by the rotating shaft 5, comprises a resin holder 31 having a cylindrical portion 311 with a cavity 310 formed in the center through which the rotating shaft 5 is inserted, a flexible substrate 2 arranged in a curved manner around the outer circumference of the cylindrical portion 311, and a cylindrical magnetic ring 32 made of a soft magnetic material arranged on the outer circumference of the flexible substrate 2. The flexible substrate 2 forms redundant first detection coils 201 and second detection coils 202, and each of the first detection coils 201 and second detection coils 202 is composed of a plurality of coil elements formed by the wiring pattern of the flexible substrate 2.

Description

[Technical Field]

[0001] The present invention relates to a magnetostrictive torque sensor for detecting torque applied to a rotating shaft having magnetostrictive properties. [Background technology]

[0002] Conventionally, a magnetostrictive torque sensor, such as the one described in Patent Document 1, is known for detecting torque applied to a rotating shaft having magnetostrictive properties, which is mounted on a vehicle. This magnetostrictive torque sensor has a resin holder with a cylindrical portion having a cavity in the center through which the rotating shaft is inserted, a cylindrical magnetic ring made of a soft magnetic material arranged on the outer circumference of the cylindrical portion of the holder, and a flexible substrate arranged between the cylindrical portion of the holder and the magnetic ring. A detection coil, to which an AC voltage is supplied from an oscillator, is formed on the flexible substrate by a wiring pattern. When torque is applied to the rotating shaft, the magnetic flux on the rotating shaft changes due to the inverse magnetostrictive effect, and the torque of the rotating shaft can be detected by detecting this change in magnetic flux with the detection coil. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2024-136748 [Overview of the project] [Problems that the invention aims to solve]

[0004] Incidentally, in case the wiring pattern of the flexible substrate is disconnected due to some cause such as vibration, it is conceivable to arrange two assemblies each consisting of a holder, a magnetic ring, and a flexible substrate side by side along the axial direction of the rotation axis to duplicate the magnetostrictive torque sensor. However, if two assemblies are arranged along the axial direction of the rotation axis, the installation space of the torque sensor will increase as a whole, and the mountability to a vehicle or the like will deteriorate. Therefore, an object of the present invention is to provide a magnetostrictive torque sensor that suppresses an increase in the installation space while enhancing reliability by redundancy and has excellent mountability.

Means for Solving the Problems

[0005] The present invention is a magnetostrictive torque sensor attached around a rotation axis having a magnetostrictive effect and detecting the torque transmitted by the rotation axis, comprising a resin holder having a cylindrical portion with a cavity through which the rotation axis is inserted formed at the center, one or two flexible substrates curved and arranged around the cylindrical portion on the outer periphery of the cylindrical portion, and a cylindrical magnetic ring made of a soft magnetic material arranged on the outer periphery of the flexible substrate. The flexible substrate forms redundant first and second detection coils, and each of the first and second detection coils is constituted by a plurality of coil elements formed by the wiring pattern of the flexible substrate. A magnetostrictive torque sensor is provided.

Effects of the Invention

[0006] According to the magnetostrictive torque sensor of the present invention, it is possible to provide a magnetostrictive torque sensor that suppresses an increase in the installation space while enhancing reliability by redundancy and has excellent mountability.

Brief Description of the Drawings

[0007] [Figure 1] It is a perspective view showing the magnetostrictive torque sensor according to the first embodiment of the present invention together with the rotation axis to be detected. [Figure 2]This is an exploded perspective view of the detection unit of a magnetostrictive torque sensor. [Figure 3] This is a cross-sectional view of the detection section of the magnetostrictive torque sensor along line AA in Figure 1. [Figure 4] This is a cross-sectional view of a flexible circuit board. [Figure 5] (a) is a pattern diagram showing the conductor pattern on the surface side of the substrate in a flexible substrate according to the first embodiment. (b) is an enlarged view of part B in (a). (c) is an enlarged view of part C in (a). [Figure 6] (a) is a pattern diagram showing the conductor pattern on the back side of the substrate in a flexible substrate according to the first embodiment. (b) is an enlarged view of section D in (a). (c) is an enlarged view of section E in (a). [Figure 7] This is a diagram showing the circuit configuration of a magnetostrictive torque sensor. [Figure 8] (a) is a schematic diagram showing an example of the relationship between the torque of the rotating shaft and the output signal of the second detection coil when the frequency of the AC voltage supplied to the first detection coil is 200 kHz and the frequency of the AC voltage supplied to the second detection coil is 333 kHz. (b) is a schematic diagram showing an example of the relationship between the torque of the rotating shaft and the output signal of the second detection coil when the frequencies of the AC voltage supplied to both the first and second detection coils are 200 kHz, as a comparative example. [Figure 9] (a) is a pattern diagram showing a surface-side conductor pattern formed on the surface side of the substrate of the first flexible substrate according to the second embodiment. (b) is a pattern diagram showing a surface-side conductor pattern formed on the surface side of the substrate of the second flexible substrate according to the second embodiment. [Figure 10] (a) is a pattern diagram showing the back-side conductor pattern formed on the back side of the substrate of the first flexible substrate according to the second embodiment. (b) is a pattern diagram showing the back-side conductor pattern formed on the back side of the substrate of the second flexible substrate according to the second embodiment. [Figure 11]This is a cross-sectional view of the detection unit showing the state in which the first flexible substrate and the second flexible substrate according to the second embodiment are arranged overlapping in the radial direction of the cylindrical portion between the cylindrical portion of the holder and the magnetic ring. [Figure 12] This is a pattern diagram showing a surface-side conductive pattern formed on the surface side of the substrate of a flexible substrate according to the third embodiment. [Figure 13] This is a pattern diagram showing the back-side conductor pattern formed on the back side of the substrate of a flexible substrate according to the third embodiment. [Figure 14] This is a diagram showing the circuit configuration of the third embodiment. [Modes for carrying out the invention]

[0008] [First Embodiment] Figure 1 is a perspective view showing a magnetostrictive torque sensor 1 according to a first embodiment of the present invention, together with the rotating shaft 5 to be detected. Figure 2 is an exploded perspective view of the detection unit 10 of the magnetostrictive torque sensor 1. Figure 3 is a cross-sectional view of the detection unit 10 of the magnetostrictive torque sensor 1 along line AA in Figure 1.

[0009] The magnetostrictive torque sensor 1 is mounted around the rotating shaft 5 and detects the torque transmitted by the rotating shaft 5. The rotating shaft 5 is, for example, a shaft that transmits the driving force of a drive source such as a vehicle engine or electric motor. The torque detection result obtained by the magnetostrictive torque sensor 1 is used for controlling the drive source, automatic transmission, etc.

[0010] The rotating shaft 5 is a ferromagnetic material with magnetostrictive properties and transmits torque by rotating around the rotation axis O. Here, magnetostrictive properties refer to the characteristic that a distortion in shape appears when a magnetic field is applied to a ferromagnetic material and it is magnetized. By using this characteristic in reverse, the torque applied to the rotating shaft 5 can be measured by detecting the change in magnetostrictive properties caused by the distortion in shape. As the rotating shaft 5, for example, a shaft made of chromium steel containing chromium, such as chromium steel, chromium-molybdenum steel, or nickel-chromium-molybdenum steel, can be suitably used, which has been subjected to carburizing, quenching, and tempering treatments, and further shot peening.

[0011] The magnetostrictive torque sensor 1 comprises a detection unit 10 provided to surround the rotating shaft 5, and a circuit unit 4 connected to the detection unit 10. The detection unit 10 comprises a flexible substrate 2 and a housing 3 that houses the flexible substrate 2. The housing 3 has a holder 31 that holds the flexible substrate 2 and a magnetic ring 32 made of a soft magnetic material that is arranged on the outer circumference of the flexible substrate 2. As shown in Figure 2, the flexible substrate 2 has a rectangular coil forming section 2A in which the first and second detection coils, described later, are formed by a conductor pattern, and a linear lead-out section 2B that is led out from the housing 3. The flexible substrate 2 is curved so that the longitudinal direction of the coil forming section 2A is aligned with the circumferential direction of the rotating shaft 5 and is arranged around the rotating shaft 5.

[0012] The holder 31 is made of resin, such as PPS (polyphenylene sulfide), and is formed by injection molding. The holder 31 integrally includes a cylindrical portion 311 with a cavity 310 formed in the center through which the rotating shaft 5 is inserted, a holding portion 312 that protrudes radially outward from the cylindrical portion 311 and holds the lead-out portion 2B of the flexible substrate 2, and an outer ring portion 313 that holds the magnetic ring 32 between itself and the cylindrical portion 311. The coil forming portion 2A of the flexible substrate 2 is arranged around the outer circumference of the cylindrical portion 311 of the holder 31 in a curved manner so as to surround the cylindrical portion 311.

[0013] The magnetic ring 32 is made of, for example, steel or a sintered magnetic material, and has a cylindrical portion 321 that is placed on the outer circumference of the flexible substrate 2, and a flange portion 322 that is held by the outer ring portion 313 of the holder 31. The inner diameter of the cylindrical portion 321 of the magnetic ring 32 is larger than the outer diameter of the cylindrical portion 311 of the holder 31, and the flexible substrate 2 is placed between the cylindrical portion 311 of the holder 31 and the cylindrical portion 321 of the magnetic ring 32.

[0014] The circuit unit 4 includes redundant first drive detection circuits 41 and second drive detection circuits 42, and an arithmetic control circuit 43. The first drive detection circuit 41 is provided corresponding to the first detection coil of the flexible substrate 2, and the second drive detection circuit 42 is provided corresponding to the second detection coil of the flexible substrate 2. The first drive detection circuit 41 has a first drive circuit section 411, a first differential amplifier circuit section 412, and a first detection circuit section 413, and detects the torque transmitted by the rotating shaft 5 based on the output of the first detection coil. The second drive detection circuit 42 has a second drive circuit section 421, a second differential amplifier circuit section 422, and a second detection circuit section 423, and detects the torque transmitted by the rotating shaft 5 based on the output of the second detection coil. The arithmetic control circuit 43 integrally calculates the torque detection result to be output from the magnetostrictive torque sensor 1 based on the torque detection result from the first drive detection circuit 41 and the torque detection result from the second drive detection circuit 42. Details of the configuration and operation of the first drive detection circuit 41 and the second drive detection circuit 42 will be described later.

[0015] Figure 4 is a cross-sectional view showing an example of the configuration of the flexible substrate 2. In this embodiment, the flexible substrate 2 is a two-layer substrate having a pair of conductive layers, and comprises a film-like substrate (base film) 20 made of a flexible dielectric such as polyimide, a surface-side conductor pattern 21 as a conductive layer formed on the front surface 20a of the substrate 20, a back-side conductor pattern 22 as a conductive layer formed on the back surface 20b of the substrate 20, a plurality of vias (also called through-hole vias or vias, etc.) 23 connecting the surface-side conductor pattern 21 and the back-side conductor pattern 22, and a coverlay 25 bonded with adhesive 24 to cover the surface-side and back-side conductor patterns 21 and 22. The conductor patterns 21 and 22 are, for example, plated copper foil and are formed into a predetermined shape by etching. The flexible substrate 2 is arranged such that the surface 20a of the substrate 20 faces the cylindrical portion 311 (inside the curve) of the holder 31, and the back surface 20b faces the magnetic ring 32 (outside the curve).

[0016] Figure 5(a) is a pattern diagram showing the conductor pattern 21 on the surface side of the substrate 20 in the flexible substrate 2. Figure 5(b) is an enlarged view of section B in Figure 5(a). Figure 5(c) is an enlarged view of section C in Figure 5(a). Figure 6(a) is a pattern diagram showing the conductor pattern 22 on the back side of the substrate 20 as seen from the surface 20a side through the substrate 20. Figure 6(b) is an enlarged view of section D in Figure 6(a). Figure 6(c) is an enlarged view of section E in Figure 6(a).

[0017] In Figures 5(a) and 6(a), the left-right direction in the drawings, which corresponds to the longitudinal direction of the coil forming section 2A of the flexible substrate 2, corresponds to the rotation direction of the rotation axis 5, and the up-down direction in the drawings, which corresponds to the short direction of the coil forming section 2A of the flexible substrate 2, corresponds to the axial direction of the rotation axis 5.

[0018] A redundant first detection coil 201 and a second detection coil 202 are formed in the coil formation section 2A of the flexible substrate 2. In this embodiment, the first detection coil 201 and the second detection coil 202 are aligned in the axial direction of the rotation shaft 5 and the cylindrical portion 311 of the holder 31. The first detection coil 201 is formed on one side in the short direction (upper side in the drawing) from the center position in the short direction of the coil formation section 2A, and the second detection coil 202 is formed on the other side in the short direction (lower side in the drawing) from the center position in the short direction of the coil formation section 2A.

[0019] On the surface 20a side of the base material 20, 20 coil elements 21A to 21T are formed by the surface-side conductor pattern 21, arranged in the longitudinal direction of the coil forming section 2A. Of these, 10 coil elements 21A to 21J are formed to one side in the short direction from the center position in the short direction of the coil forming section 2A, and the other 10 coil elements 21K to 21T are formed to the other side in the short direction from the center position in the short direction of the coil forming section 2A. Each coil element 21A to 21J has an inclined portion that is tilted at a 45° angle to one side with respect to the longitudinal direction of the coil forming section 2A. Coil elements 21A, 21J, 21K, and 21T are right-angled triangles, while coil elements 21B-21I and 21L-21S are parallelograms.

[0020] Furthermore, on the back surface 20b of the base material 20, 20 coil elements 22A to 22T are formed by the conductor pattern 22 on the back surface, arranged in the longitudinal direction of the coil forming section 2A. Of these, 10 coil elements 22A to 22J are formed to one side in the short direction from the center position in the short direction of the coil forming section 2A, and the other 10 coil elements 22K to 22T are formed to the other side in the short direction from the center position in the short direction of the coil forming section 2A. Each coil element 22A to 22J has an inclined portion that is tilted at a 45° angle to the other side with respect to the longitudinal direction of the coil forming section 2A. Coil elements 22A, 22J, 22K, and 22T are right-angled triangles, while coil elements 22B-22I and 22L-22S are parallelograms.

[0021] The first detection coil 201 is composed of coil elements 21A to 21J formed by the conductor pattern 21 on the front side, and coil elements 22A to 22J formed by the conductor pattern 22 on the back side. The first detection coil 201 also has four lines 201a, 201b, 201c, and 201d, as shown in Figures 5(b) and 6(b). Two of these lines, 201a and 201b, extend parallel to each other in close proximity and form coil elements 21A to 21J. The other two lines, 201c and 201d, extend parallel to each other in close proximity and form coil elements 22A to 22J.

[0022] Lines 201a and 201b are mainly formed by the conductor pattern 21 on the front side, with a portion between coil elements 21A to 21J being formed by the conductor pattern 22 on the back side. Lines 201c and 201d are mainly formed by the conductor pattern 22 on the back side, with a portion between coil elements 22A to 22J being formed by the conductor pattern 21 on the front side.

[0023] The second detection coil 202 is composed of coil elements 21K to 21T formed by the conductor pattern 21 on the front side and coil elements 22K to 22T formed by the conductor pattern 22 on the back side. The second detection coil 202 also has four lines 202a, 202b, 202c, and 202d, as shown in Figures 5(c) and 6(c). Two of these lines, 202a and 202b, extend parallel to each other in close proximity and form coil elements 21K to 21T. The other two lines, 202c and 202d, extend parallel to each other in close proximity and form coil elements 22K to 22T.

[0024] The lines 202a and 202b are mainly formed by the conductor pattern 21 on the front surface side, and a part between the coil elements 21K to 21T is formed by the conductor pattern 22 on the back surface side. The lines 202c and 202d are mainly formed by the conductor pattern 22 on the back surface side, and a part between the coil elements 22K to 22T is formed by the conductor pattern 21 on the front surface side.

[0025] FIG. 7 is a configuration diagram showing the circuit configuration of the magnetostrictive torque sensor 1. In FIG. 7, the coil elements 21A to 21T and the coil elements 22A to 22T are schematically shown. The lines 201a, 201b, 201c, and 201d of the first detection coil 201 form impedance portions Z 11 ~Z 14 respectively. The impedance portion Z 11 formed by the line 201a of the first detection coil 201 and the impedance portion Z 13 formed by the line 201c are connected in series at the node 201e. The impedance portion Z 14 formed by the line 201d and the impedance portion Z 12 formed by the line 201b are connected in series at the node 201f.

[0026] The lines 201a, 201b, 201c, and 201d of the first detection coil 201 constitute an impedance bridge circuit C1 as shown in FIG. 7. In other words, the first detection coil 201 has four impedance portions Z 11 ,Z 12 ,Z 13 ,Z 14 that constitute the impedance bridge circuit C1. The impedance of the impedance portion Z 11 formed by the line 201a is the combined impedance of the DC resistance of the line 201a and the inductance of the coil elements 21A to 21J. The impedance portion Z 12The impedance is the combined impedance of the DC resistance of line 201b and the inductance of coil elements 21A to 21J. The impedance section Z formed by line 201c 13 The impedance is the combined impedance of the DC resistance of line 201c and the inductance of coil elements 22A~22J. The impedance section Z formed by line 201d 14 The impedance is the combined impedance of the DC resistance of the transmission line 201d and the inductance of the coil elements 22A to 22J.

[0027] AC voltage is supplied from the first drive circuit section 411 to the series circuits of lines 201a and 201c, and the series circuits of lines 201d and 201b in the impedance bridge circuit C1. As a result, the magnetic flux generated in the coil elements 21A~21T and 22A~22T is linked with the rotating shaft 5. When torque is applied to the rotating shaft 5, the magnetostrictive effect increases the permeability in the direction of +45 degrees to the axial direction (the direction in which it is pulled by torsion) and decreases the permeability in the direction of -45 degrees to the axial direction (the direction in which it is compressed by torsion). Therefore, when torque is applied to the rotating shaft 5 while an AC voltage is supplied from the first drive circuit 411, the inductance in lines 201a and 201b increases (or decreases), and the inductance in lines 201c and 201d decreases (or increases), and the voltage between nodes 201e and 201f, which is the output signal of the first detection coil 201, changes in accordance with the torque of the rotating shaft 5.

[0028] The voltage between node 201e and node 201f is amplified by the first differential amplifier circuit 412. The first differential amplifier circuit 412 selectively amplifies the output signal of the first detection coil 201, which is synchronized with the frequency signal of the AC voltage supplied to the first detection coil 201 by the first drive circuit 411. More specifically, the first differential amplifier circuit 412 is a lock-in amplifier that amplifies the voltage between node 201e and node 201f using a reference signal with the same frequency as the AC voltage output by the first drive circuit 411.

[0029] The output signal of the first detection coil 201, amplified by the first differential amplifier circuit 412, is input to the first detection circuit 413. The first detection circuit 413 detects the change in the permeability of the rotating shaft 5 due to the torque applied to the rotating shaft 5 by the change in impedance generated in the first detection coil 201, based on the signal input from the first differential amplifier circuit 412. The detection result of the first detection circuit 413 is output to the arithmetic control circuit 43.

[0030] The lines 202a, 202b, 202c, 202d of the second detection coil 202 and the second drive detection circuit 42 are configured in the same way as the lines 201a, 201b, 201c, 201d of the first detection coil 201 and the first drive detection circuit 41. The lines 202a, 202b, 202c, 202d of the second detection coil 202 have an impedance section Z 21 ~Z 24 Each of these constitutes an impedance section Z formed by the transmission line 202a of the second detection coil 202. 21 The impedance section Z formed by the line 202c 23 The two are connected in series at node 202e, and the impedance section Z is formed by the transmission line 202d. 24 The impedance section Z formed by the line 202b 22 The two are connected in series at node 202f.

[0031] The lines 202a, 202b, 202c, and 202d of the second detection coil 202 constitute an impedance bridge circuit C2. In other words, the second detection coil 202 consists of four impedance sections Z that make up the impedance bridge circuit C2. 21 ,Z 22 ,Z 23 ,Z 24 It has an impedance section Z formed by the transmission line 202a. 21 The impedance is the combined impedance of the DC resistance of line 202a and the inductance of the coil elements 21K~21T. The impedance section Z formed by line 202b 22The impedance is the combined impedance of the DC resistance of line 202b and the inductance of the coil elements 21K~21T. The impedance section Z formed by line 202c 23 The impedance is the combined impedance of the DC resistance of line 202c and the inductance of the coil elements 22K~22T. The impedance section Z formed by line 202d 24 The impedance is the combined impedance of the DC resistance of the transmission line 202d and the inductance of the coil element 22K~22T.

[0032] The second drive circuit section 421 of the second drive detection circuit 42 supplies AC voltage to the series circuits of lines 202a and 202c, and lines 202d and 202b in the second detection coil 202. The second differential amplifier section 422 is a lock-in amplifier that selectively amplifies the output signal of the second detection coil 202 (voltage between nodes 202e and 202f) synchronized with the frequency signal of the AC voltage supplied to the second detection coil 202 by the second drive circuit section 421. Based on the signal input from the second differential amplifier section 422, the second detection circuit section 423 detects the change in the permeability of the rotating shaft 5 due to the torque applied to the rotating shaft 5 by the change in impedance generated in the second detection coil 202. The detection result of the second detection circuit section 423 is output to the arithmetic control circuit 43.

[0033] The arithmetic control circuit 43 integrates the torque detection results from the first drive detection circuit 41 and the second drive detection circuit 42, and outputs the calculation result to, for example, the control device of the power source that applies torque to the rotating shaft 5. When the arithmetic control circuit 43 determines that both the detection results from the first drive detection circuit 41 and the detection results from the second drive detection circuit 42 are normal, it calculates the torque applied to the rotating shaft 5 based, for example, on the average value of both detection results.

[0034] Furthermore, if a failure occurs in the first detection coil 201 or the first drive detection circuit 41 and a detection result from the first drive detection circuit 41 cannot be obtained, or if the detection result from the first drive detection circuit 41 is determined to contain a large error, the arithmetic control circuit 43 calculates the torque applied to the rotating shaft 5 based on the detection result from the second drive detection circuit 42 and stops the operation of the first drive detection circuit 41. Also, if a failure occurs in the second detection coil 202 or the second drive detection circuit 42 and a detection result from the second drive detection circuit 42 cannot be obtained, or if the detection result from the second drive detection circuit 42 is determined to contain a large error, the arithmetic control circuit 43 calculates the torque applied to the rotating shaft 5 based on the detection result from the first drive detection circuit 41 and stops the operation of the second drive detection circuit 42.

[0035] The arithmetic control circuit 43 may also be configured to use either the first drive detection circuit 41 or the second drive detection circuit 42 as the primary system and the other as the standby system. Under normal circumstances, it may calculate the torque applied to the rotating shaft 5 using the detection result of the primary system (e.g., the first drive detection circuit 41), and when it is determined that the primary system (e.g., the first drive detection circuit 41) has failed, it may calculate the torque applied to the rotating shaft 5 using the detection result of the standby system (e.g., the second drive detection circuit 42).

[0036] The frequency of the AC voltage supplied by the first drive circuit 411 to the first detection coil 201 is different from the frequency of the AC voltage supplied by the second drive circuit 421 to the second detection coil 202. When the larger of the two frequencies of the AC voltage supplied by the first drive circuit 411 to the first detection coil 201 and the smaller of the two frequencies of the AC voltage supplied by the second drive circuit 421 to the second detection coil 202 is denoted as f1 and f2 as f2, f1 is at least 1.25 times f2. Because f1 and f2 are different, magnetic interference between the first detection coil 201 and the second detection coil 202 is suppressed, and the torque detection accuracy of the magnetostrictive torque sensor 1 is improved. For example, f1 is 200 kHz and f2 is 333 kHz. When f1 is 200 kHz and f2 is 333 kHz, f2 is 1.665 times f1.

[0037] Figure 8(a) is a schematic diagram showing an example of the relationship between the torque of the rotating shaft 5 and the output signal of the second detection coil 202 when the frequency of the AC voltage supplied to the first detection coil 201 is 200 kHz and the frequency of the AC voltage supplied to the second detection coil 202 is 333 kHz. Figure 8(b) is a schematic diagram showing an example of the relationship between the torque of the rotating shaft 5 and the output signal of the second detection coil 202 when the frequencies of the AC voltage supplied to both the first detection coil 201 and the second detection coil 202 are 200 kHz, as a comparative example.

[0038] As shown in Figure 8(b), if the frequency of the AC voltage supplied to the first detection coil 201 and the frequency of the AC voltage supplied to the second detection coil 202 are the same, magnetic interference between the first detection coil 201 and the second detection coil 202 disrupts the output signal of the second detection coil 202, reducing the torque detection accuracy. In contrast, if the frequencies of the AC voltage supplied to the first detection coil 201 and the AC voltage supplied to the second detection coil 202 are different, as shown in Figure 8(a), magnetic interference is suppressed and the torque detection accuracy is improved.

[0039] (Effects of the first embodiment) According to the embodiment described above, since the first detection coil 201 and the second detection coil 202 are formed on the flexible substrate 2 so as to be aligned along the axial direction of the rotating shaft 5 and the cylindrical portion 311 of the holder 31, it is possible to provide a magnetostrictive torque sensor that is easy to mount while suppressing an increase in installation space, while increasing reliability through redundancy.

[0040] In this embodiment, the first detection coil 201 and the second detection coil 202 are formed on a single flexible substrate 2. However, the first detection coil 201 and the second detection coil 202 may be formed on separate flexible substrates, and these flexible substrates may be arranged side by side along the axial direction of the rotating shaft 5 and the cylindrical portion 311 of the holder 31. Even with this configuration, the same effects as when the first detection coil 201 and the second detection coil 202 are formed on a single flexible substrate 2 as described above can be obtained.

[0041] [Second Embodiment] Next, a second embodiment will be described with reference to Figures 9 to 11. In the first embodiment, a first detection coil 201 and a second detection coil 202 were formed on a single flexible substrate 2, arranged in the axial direction of the rotating shaft 5 and the cylindrical portion 311 of the holder 31. In the second embodiment, however, the first flexible substrate on which the first detection coil is formed and the second flexible substrate on which the second detection coil is formed are arranged to overlap in the radial direction of the rotating shaft 5 and the cylindrical portion 311 of the holder 31.

[0042] Figure 9(a) is a pattern diagram showing the surface-side conductor pattern 61 formed on the surface 60a side of the base material 60 of the first flexible substrate 6 according to this embodiment. Figure 9(b) is a pattern diagram showing the surface-side conductor pattern 71 formed on the surface 70a side of the base material 70 of the second flexible substrate 7 according to this embodiment. Figure 10(a) is a pattern diagram showing the back-side conductor pattern 62 formed on the back surface 60b side of the first flexible substrate 6 according to this embodiment, as viewed from the surface 60a side through the base material 60. Figure 10(b) is a pattern diagram showing the back-side conductor pattern 72 formed on the back surface 70b side of the second flexible substrate 7 according to this embodiment, as viewed from the surface 70a side through the base material 70. Figure 11 is a cross-sectional view of the detection unit 10 showing the state in which the first flexible substrate 6 and the second flexible substrate 7 are arranged overlapping in the radial direction of the cylindrical portion 311 between the cylindrical portion 311 of the holder 31 and the magnetic ring 32. In this embodiment, the axial lengths of the cylindrical portion 311 of the holder 31 and the magnetic ring 32 are shorter than in the first embodiment.

[0043] The first flexible substrate 6 has a rectangular coil-forming portion 6A and a linear lead-out portion 6B extending from the coil-forming portion 6A. Similarly, the second flexible substrate 7 has a rectangular coil-forming portion 7A and a linear lead-out portion 7B extending from the coil-forming portion 7A. The first flexible substrate 6 and the second flexible substrate 7 have the same shape and structure. The lead-out portions 6B and 7B are connected to the circuit unit 4, similar to the first embodiment.

[0044] Multiple coil elements 61A to 61J are formed on the conductor pattern 61 on the front side of the first flexible substrate 6 by lines 601a and 601b that extend in close proximity and parallel to each other. Multiple coil elements 62A to 62J are formed on the conductor pattern 62 on the back side of the first flexible substrate 6 by lines 601c and 601d that extend in close proximity and parallel to each other. These coil elements 61A to 61J and coil elements 62A to 62J constitute the first detection coil 601 on the first flexible substrate 6. In addition, the impedance section Z of the first detection coil 601 is formed by lines 601a, 601b, 601c, and 601d. 11 ,Z 12 ,Z 13 ,Z 14 Each of these is formed.

[0045] Multiple coil elements 71A to 71J are formed on the conductor pattern 71 on the front side of the second flexible substrate 7 by lines 701a and 701b that extend in close proximity and parallel to each other. Multiple coil elements 72A to 72J are formed on the conductor pattern 72 on the back side of the second flexible substrate 7 by lines 701c and 701d that extend in close proximity and parallel to each other. These coil elements 71A to 71J and coil elements 72A to 72J constitute the second detection coil 701 on the second flexible substrate 7. In addition, the impedance section Z of the second detection coil 701 is formed by lines 701a, 701b, 701c, and 701d. 21 ,Z 22 ,Z 23 ,Z 24 Each of these is formed.

[0046] Impedance section Z of the first detection coil 601 11 ,Z 12 ,Z 13 ,Z 14Similar to the first embodiment described with reference to Figure 7, an impedance bridge circuit is configured, an AC voltage is supplied from the first drive circuit section 411, and the output signal of the first detection coil 601 is input to the first differential amplifier circuit section 412. Similarly, for the second detection coil 701, the impedance section Z 21 ,Z 22 ,Z 23 ,Z 24 This constitutes an impedance bridge circuit, to which an AC voltage is supplied from the second drive circuit section 421, and the output signal of the second detection coil 701 is input to the second differential amplifier circuit section 422. As a result, the torque of the rotating shaft 5 can be detected, similar to the first embodiment.

[0047] According to the second embodiment described above, in addition to the effects of the first embodiment, the housing 3 can be made smaller than in the first embodiment, and the increase in installation space can be suppressed.

[0048] [Third Embodiment] Next, a third embodiment will be described with reference to Figures 12 to 14. In the first embodiment, a first detection coil 201 and a second detection coil 202 were formed on a single flexible substrate 2, arranged in the axial direction of the rotating shaft 5 and the cylindrical portion 311 of the holder 31. In the third embodiment, redundant first and second detection coils are formed on a single flexible substrate, arranged along the circumferential direction of the cylindrical portion 311 of the holder 31.

[0049] Figure 12 is a pattern diagram showing the surface-side conductor pattern 81 formed on the surface 80a side of the base material 80 of the flexible substrate 8 according to this embodiment. Figure 13 is a pattern diagram showing the back-side conductor pattern 82 formed on the back surface 80b side of the base material 80 of the flexible substrate 8 according to this embodiment. Figure 14 is a configuration diagram showing the circuit configuration of this embodiment.

[0050] The flexible substrate 8 has a rectangular coil-forming portion 8A and a linear lead-out portion 8B extending from the coil-forming portion 8A. As described with reference to Figures 3 and 11 in the first and second embodiments, it is arranged in a curved manner to surround the cylindrical portion 311 of the holder 31.

[0051] Multiple coil elements 81A to 81E are formed on the conductor pattern 81 on the surface side of the flexible substrate 8 by lines 801a and 801b that extend in close proximity and parallel to each other. In addition, multiple coil elements 81F to 81J are formed on the conductor pattern 81 on the surface side of the flexible substrate 8 by lines 802a and 802b that extend in close proximity and parallel to each other.

[0052] Multiple coil elements 82A to 82E are formed on the conductor pattern 82 on the back side of the flexible substrate 8 by lines 801c and 801d that extend in close proximity and parallel to each other. In addition, multiple coil elements 82F to 82J are formed on the conductor pattern 82 on the back side of the flexible substrate 8 by lines 802c and 802d that extend in close proximity and parallel to each other.

[0053] As shown in Figure 14, coil elements 81A to 81E and coil elements 82A to 82E constitute the first detection coil 801 on the flexible substrate 8. Furthermore, the impedance section Z of the first detection coil 801 is determined by the lines 801a, 801b, 801c, and 801d. 11 ,Z 12 ,Z 13 ,Z 14 These are each formed. The first detection coil 801 detects the change in magnetic permeability over half a rotation of the rotating shaft 5.

[0054] The coil elements 81F~81J and 82F~82J constitute the second detection coil 802 on the flexible substrate 8. Furthermore, the lines 802c, 802d, 802c, 802d contribute to the impedance section Z of the second detection coil 802. 21 ,Z 22 ,Z 23 ,Z24 These are each formed. The second detection coil 802 detects a change in magnetic permeability over half a rotation of the axis 5 that is different from that of the first detection coil 801.

[0055] Impedance section Z of the first detection coil 801 11 ,Z 12 ,Z 13 ,Z 14 This constitutes an impedance bridge circuit, to which an AC voltage is supplied from the first drive circuit section 411, and the output signal of the first detection coil 801 is input to the first differential amplifier circuit section 412. Similarly, for the second detection coil 802, the impedance section Z 21 ,Z 22 ,Z 23 ,Z 24 This constitutes an impedance bridge circuit, to which an AC voltage is supplied from the second drive circuit section 421, and the output signal of the second detection coil 802 is input to the second differential amplifier circuit section 422. As a result, the torque of the rotating shaft 5 can be detected, similar to the first embodiment.

[0056] According to the third embodiment described above, in addition to the effects of the first embodiment, the housing 3 can be made smaller than in the first embodiment, and the increase in installation space can be suppressed. Furthermore, since the first detection coil 801 and the second detection coil 802 are formed side by side along the circumferential direction of the cylindrical portion 311 of the holder 31, the magnetostrictive torque sensor can be constructed at a lower cost compared to the case in which two flexible substrates 6 and 7 are stacked and arranged as in the second embodiment.

[0057] In this embodiment, the first detection coil 801 and the second detection coil 802 are formed on a single flexible substrate 8. However, the first detection coil 801 and the second detection coil 802 may be formed on separate flexible substrates, and these flexible substrates may be arranged side by side along the circumferential direction of the cylindrical portion 311 of the holder 31.

[0058] (Summary of the embodiments) Next, the technical concepts understood from each of the embodiments described above will be described using the reference numerals and other symbols from the embodiments. However, the reference numerals in the following description are not limited to the components in the claims that are specifically shown in the embodiments.

[0059] [1] A magnetostrictive torque sensor (1) is mounted around a rotating shaft having a magnetostrictive effect and detects torque transmitted by the rotating shaft (5), comprising: a resin holder (31) having a cylindrical portion (311) with a cavity (310) formed in the center through which the rotating shaft (5) is inserted; one or two flexible substrates (2,6,7,8) arranged around the outer circumference of the cylindrical portion (311) in a curved manner to surround the cylindrical portion (311); and a cylindrical magnetic ring (32) made of a soft magnetic material arranged around the outer circumference of the flexible substrates (2,6, A magnetostrictive torque sensor (1) is provided, wherein redundant first detection coils (201, 601, 801) and second detection coils (202, 701, 802) are formed by 7,8), and each of the first detection coils (201, 601, 801) and the second detection coils (202, 701, 802) is composed of a plurality of coil elements (21A~21T, 22A~22T, 61A~61J, 62A~62J, 71A~71J, 72A~72J, 81A~81J, 82A~82J) formed by the wiring pattern of the flexible substrate (2,6,7,8).

[0060] [2] The magnetostrictive torque sensor (1) according to [1] above, wherein the first detection coil (201) and the second detection coil (202) are arranged side by side along the axial direction of the cylindrical portion (311).

[0061] [3] The magnetostrictive torque sensor (1) according to [1] above, wherein the first detection coil (601) and the second detection coil (701) are arranged to overlap in the radial direction of the cylindrical portion (311).

[0062] [4] The magnetostrictive torque sensor (1) according to [1] above, wherein the first detection coil (801) and the second detection coil (802) are arranged side by side along the circumferential direction of the cylindrical portion (311).

[0063] [5] The first drive detection circuit (41) is provided in correspondence with the first detection coil (201, 601, 801), and the second drive detection circuit (42) is provided in correspondence with the second detection coil (202, 701, 802), wherein the first drive detection circuit (41) has a first drive circuit section (411) that supplies an AC voltage to the first detection coil (201, 601, 801), and a first detection circuit section (413) that detects the change in the permeability of the rotating shaft (5) due to the torque by the change in impedance generated in the first detection coil (201, 601, 801), and the second drive detection circuit (42) has the second A magnetostrictive torque sensor (1) according to any one of [1] to [4] above, comprising: a second drive circuit section (421) that supplies an AC voltage to detection coils (202, 701, 802); and a second detection circuit section (423) that detects a change in the permeability of the rotating shaft (5) due to the torque by a change in impedance occurring in the second detection coils (202, 701, 802), wherein the frequency of the AC voltage supplied by the first drive circuit section (411) to the first detection coil (201, 601, 801) and the frequency of the AC voltage supplied by the second drive circuit section (421) to the second detection coil (202, 701, 802) are different.

[0064] Although embodiments of the present invention have been described above, the first to third embodiments described above do not limit the invention as defined in the claims. It should also be noted that not all combinations of features described in the first to third embodiments are necessarily essential for solving the problem of the invention. Furthermore, the present invention can be modified as appropriate without departing from its spirit, and can be modified as follows, for example.

[0065] In the first to third embodiments described above, the flexible substrate is described as a two-layer substrate having a pair of conductive layers (a conductive pattern on the front side and a conductive pattern on the back side). However, the flexible substrate is not limited to this, and may be a four-layer substrate having, for example, four conductive layers stacked on top of each other. In this case, the first detection coil and the second detection coil can be formed across the four conductive layers. [Explanation of symbols]

[0066] 1…Magnetostrictive torque sensor 2, 6, 7, 8… Flexible circuit board 201,601,801… First detection coil 202,701,802…Second detection coil 21A~21T, 22A~22T, 61A~61J, 62A~62J, 71A~71J, 72A~72J, 81A~81J, 82A~82J... Coil element 31... Holder 310...Cavity 311...Cylindrical section 41…First drive detection circuit 411...First drive circuit section 413...First detection circuit section 42...Second drive detection circuit 421...Second drive circuit section 423...Second detection circuit section 5…Rotation axis

Claims

1. A magnetostrictive torque sensor mounted around a rotating shaft having a magnetostrictive effect, for detecting torque transmitted by the rotating shaft, The holder comprises a resin holder having a cylindrical portion with a cavity formed in the center through which the rotating shaft is inserted, one or two flexible substrates arranged around the outer circumference of the cylindrical portion in a curved manner so as to surround the cylindrical portion, and a cylindrical magnetic ring made of a soft magnetic material arranged around the outer circumference of the flexible substrates. The flexible substrate has redundant first and second detection coils formed on it. Each of the first detection coil and the second detection coil is composed of a plurality of coil elements formed by the wiring pattern of the flexible substrate. Magnetostrictive torque sensor.

2. The first detection coil and the second detection coil are arranged side by side along the axial direction of the cylindrical portion. The magnetostrictive torque sensor according to claim 1.

3. The first detection coil and the second detection coil are arranged to overlap in the radial direction of the cylindrical portion. The magnetostrictive torque sensor according to claim 1.

4. The first detection coil and the second detection coil are arranged side by side along the circumferential direction of the cylindrical portion. The magnetostrictive torque sensor according to claim 1.

5. The system comprises a first drive detection circuit provided in correspondence with the first detection coil, and a second drive detection circuit provided in correspondence with the second detection coil, The first drive detection circuit includes a first drive circuit section that supplies an AC voltage to the first detection coil, and a first detection circuit section that detects the change in the permeability of the rotating shaft due to the torque by the change in impedance generated in the first detection coil. The second drive detection circuit includes a second drive circuit section that supplies an AC voltage to the second detection coil, and a second detection circuit section that detects the change in the permeability of the rotating shaft due to the torque by the change in impedance generated in the second detection coil. The frequency of the AC voltage supplied by the first drive circuit to the first detection coil is different from the frequency of the AC voltage supplied by the second drive circuit to the second detection coil. A magnetostrictive torque sensor according to any one of claims 1 to 4.

Images