Magnetostrictive torque sensor

Abstract

To provide a magnetostrictive torque sensor with which downsizing is possible.SOLUTION: A magnetostrictive torque sensor 1 comprises: a plastic holder 2 having a cylindrical part 21 through which a revolving shaft 9 having magnetostrictive effects is inserted; a flexible substrate 4 having a signal line part 400 in which a detection part 40 in which coil groups composed by combining a plurality of detection coils juxtaposed in a prescribed direction are formed by a wiring pattern and a plurality of signal lines 491-494 for electrically connecting the coil groups and an external device 8 together are formed by a wiring pattern; and a cylindrical magnetic ring 5 located on the outer circumference of the cylindrical part 21 of the holder 2 and formed from a soft magnetic material. The detection part 40 is located between the cylindrical part 21 of the holder 2 and the magnetic ring 5, and the signal line part 400 is led out to the outside of the holder 2. The holder 2 has an annular wall 23 surrounding the outer circumference of an axial edge of the magnetic ring 5, with the holder 2 and the magnetic ring 5 secured by a shaft-like fastener 6 which is inserted into a stop hole 510 of the magnetic ring 5, penetrating the annular wall 23.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a magnetostrictive torque sensor that detects torque transmitted by a rotating shaft having a magnetostrictive effect.

Background Art

[0002] Conventionally, for example, a magnetostrictive torque sensor has been used to detect torque of an output rotating shaft of an automobile engine or the like. The magnetostrictive torque sensor utilizes the magnetostrictive effect in which the magnetic permeability of a rotating shaft changes due to stress, and is configured to detect the torque applied to the rotating shaft based on a change in inductance of a detection coil disposed around the rotating shaft. The present applicant has proposed a magnetostrictive torque sensor in which a flexible substrate formed with a plurality of detection coils is disposed around a rotating shaft, and the torque applied to the rotating shaft is detected based on changes in inductance of the plurality of detection coils (see Patent Document 1).

[0003] The magnetostrictive torque sensor described in Patent Document 1 houses a flexible substrate formed with a plurality of detection coils in a resin housing. A plurality of terminal portions are provided at an end of the flexible substrate, and signal lines of a cable are connected to these terminal portions in the resin housing. The cable is led out from the resin housing and connected to a control device.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In some cases, it is difficult to secure space for installing a torque sensor around a rotating shaft, and there is a demand for miniaturized torque sensors. This invention was made to meet this demand, and its objective is to provide a magnetostrictive torque sensor that can be miniaturized. [Means for solving the problem]

[0006] To achieve the above objective, the present invention provides a magnetostrictive torque sensor that is mounted around a rotating shaft having a magnetostrictive effect and detects torque transmitted by the rotating shaft, comprising: a resin holder having a cylindrical portion with a cavity formed in the center through which the rotating shaft is inserted; a detection unit having a coil group formed by a wiring pattern of a plurality of detection coils arranged in a predetermined direction, and a signal line unit having a plurality of signal lines formed by a wiring pattern of a plurality of signal lines electrically connecting the coil group to an external device; and a cylindrical magnetic ring made of a soft magnetic material arranged on the outer circumference of the cylindrical portion of the holder, wherein the detection unit is arranged in a curve between the cylindrical portion of the holder and the magnetic ring, a part of the signal line unit is led out to the outside of the holder, the holder has an annular wall surrounding the outer circumference of one axial end of the magnetic ring, and the magnetic ring has a fastening hole formed on the outer circumference facing the inner circumference of the annular wall, and the holder and the magnetic ring are fixed together by an axial fastener that penetrates the annular wall and is inserted into the fastening hole of the magnetic ring. We provide magnetostrictive torque sensors. [Effects of the Invention]

[0007] According to the present invention, the magnetostrictive torque sensor can be miniaturized, making it possible to save installation space. [Brief explanation of the drawing]

[0008] [Figure 1] A perspective view showing a magnetostrictive torque sensor according to an embodiment of the present invention, along with the rotating shaft to be detected. [Figure 2] This is an exploded perspective view of a magnetostrictive torque sensor. [Figure 3] Figure 2 shows an exploded perspective view of a magnetostrictive torque sensor, viewed from a different direction. [Figure 4] This is a cross-sectional view of a magnetostrictive torque sensor. [Figure 5] (a) is a plan view showing a single flexible substrate. (b) is a plan view showing a base material from which multiple flexible substrates are chamfered. [Figure 6] This is a cross-sectional view showing the layer structure of a flexible substrate. [Figure 7] (a) to (d) are plan views showing the first to fourth wiring layers. [Figure 8] This is a schematic circuit diagram illustrating an example of an electrical circuit consisting of a flexible circuit board, an oscillator, and a voltmeter. [Figure 9] (a) is a diagram showing the holder with the cover member and flexible substrate attached, viewed from the axial direction. (b) is a diagram showing the state in (a) with the cover member omitted from the illustration. [Figure 10] (a) is a diagram showing the recess of the holder as viewed from the axial direction. (b) is a perspective view showing the peripheral part of the recess. [Figure 11] (a) and (b) are perspective views showing the cover member. [Figure 12] (a) is a perspective view showing the fastener. (b) is a cross-sectional view of the fastener in a section perpendicular to the longitudinal direction. [Figure 13] This is a perspective view showing the holder and magnetic ring together with the fasteners. [Figure 14] This is an explanatory diagram showing a magnetostrictive torque sensor mounted on a housing. [Modes for carrying out the invention]

[0009] [Embodiment] Figure 1 is a perspective view showing a magnetostrictive torque sensor 1 according to an embodiment of the present invention together with the rotating shaft 9 to be detected. Figure 2 is an exploded perspective view of the magnetostrictive torque sensor 1. Figure 3 is an exploded perspective view of the magnetostrictive torque sensor 1 viewed from a different direction than in Figure 2. Figure 4 is a cross-sectional view of the magnetostrictive torque sensor 1.

[0010] The magnetostrictive torque sensor 1 is mounted around the rotating shaft 9 and detects the torque transmitted by the rotating shaft 9. The rotating shaft 9 is, for example, a shaft that transmits the driving force of a drive source such as an automobile engine or an electric motor. The torque detection result obtained by the magnetostrictive torque sensor 1 is used for controlling the drive source, automatic transmission, etc.

[0011] The rotating shaft 9 is a ferromagnetic material exhibiting the magnetostrictive effect and transmits torque by rotating around the rotation axis O. Here, the magnetostrictive effect is a phenomenon in which distortion of shape occurs when a magnetic field is applied to a ferromagnetic material and it is magnetized. By utilizing this phenomenon in reverse and detecting the change in magnetic properties caused by the distortion of shape, the torque applied to the rotating shaft 9 can be detected. As the rotating shaft 9, 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. Hereinafter, the direction parallel to the rotation axis O of the rotating shaft 9 will be referred to as the axial direction.

[0012] The magnetostrictive torque sensor 1 comprises a holder 2, a cover member 3, a flexible substrate 4, a cylindrical magnetic ring 5 made of soft magnetic material, an axial fastener 6 for fixing the holder 2 and the magnetic ring 5, a lip seal 7 positioned between the holder 2 and the magnetic ring 5, and an external device 8 positioned outside the holder 2. The external device 8 has an oscillator 81 and a voltmeter 82, and the oscillator 81 and voltmeter 82 are electrically connected to the flexible substrate 4. The operation of the external device 8 will be described later.

[0013] The holder 2 is made of a resin material such as PPS (polyphenylene sulfide). The holder 2 is formed, for example, by injection molding, but is not limited thereto, and the holder 2 may be formed using a 3D modeling device such as a 3D printer. The holder 2 has a cylindrical portion 21 in which a cavity 20 through which the rotation shaft 9 is inserted is formed at the center, a recess 22 that houses a part of the flexible substrate 4, and an annular wall 23 that surrounds the outer periphery of one axial end of the magnetic ring 5. The central axis C of the cylindrical portion 21 coincides with the rotation axis O of the rotation shaft 9. The recess 22 is provided on the outer periphery of the cylindrical portion 21. The annular wall 23 is provided on the outer periphery of the cylindrical portion 21 other than the portion where the recess 22 is formed. An annular groove 230 for housing one axial end of the magnetic ring 5 is formed between the cylindrical portion 21 and the annular wall 23. The recess 22 and the annular groove 230 both open to one side in the axial direction.

[0014] The cover member 3 is made of a resin material similar to that of the holder 2, for example, and integrally has a plate portion 31 that covers one axial side of the recess 22 and a convex portion 32 that fits into the recess 22. Details of the shapes of the cover member 3 and the recess 22 will be described later.

[0015] The magnetic ring 5 is made of, for example, a steel material or a sintered magnetic body, is formed in a cylindrical shape having an inner diameter larger than the outer diameter of the cylindrical portion 21 of the holder 2, and is disposed on the outer periphery of the cylindrical portion 21. When the magnetic ring 5 is made of a steel material, a magnetic steel material such as electromagnetic stainless steel can be preferably used, and as its molding method, for example, deep drawing can be used. Also, a long pipe-shaped steel material may be cut out to a predetermined length to form the magnetic ring 5. The magnetic ring 5 is arranged axially with the cover member 3 and restricts the movement of the cover member 3 in the direction in which the convex portion 32 detaches from the recess 22 of the holder 2.

[0016] In this embodiment, the magnetic ring 5 integrally comprises a large-diameter portion 51 and a small-diameter portion 52 with different outer diameters. The inner diameters of the large-diameter portion 51 and the small-diameter portion 52 are the same. The large-diameter portion 51 is provided at one axial end of the magnetic ring 5 and is housed in the annular groove 230 of the holder 2. The annular wall 23 of the holder 2 surrounds the outer circumference of the large-diameter portion 51. The magnetic ring 5 is positioned radially perpendicular to the central axis C relative to the holder 2 by the large-diameter portion 51 being fitted into the annular groove 230. More specifically, the relative position between the holder 2 and the magnetic ring 5 in the radial direction is determined by the fact that the outer circumferential surface 51a of the large-diameter portion 51 faces the inner circumferential surface 23a of the annular wall 23.

[0017] As shown in Figure 3, a notch 500 is formed on the axial end face 51b of the large-diameter portion 51 of the magnetic ring 5, in the portion facing the plate portion 31 of the cover member 3, recessing axially from the end face 51b. When the cover member 3 and the magnetic ring 5 are assembled to the holder 2, a part of the plate portion 31 of the cover member 3 is accommodated in the notch 500, and the end face 51b of the large-diameter portion 51 abuts against the bottom surface 230a of the annular groove 230.

[0018] Figure 5(a) is a plan view showing a single flexible substrate 4. Figure 5(b) is a plan view showing a base material 100 from which multiple flexible substrates 4 are chamfered. The flexible substrates 4 are manufactured by cutting them from the base material 100.

[0019] The flexible substrate 4 integrally includes a detection unit 40 having multiple detection coils for detecting the magnetic field of the rotating shaft 9, and a signal line unit 400 formed by a wiring pattern with multiple signal lines that electrically connect the external device 8 and the detection unit 40. In Figure 5, the multiple detection coils and multiple signal lines are omitted from the illustration. The flexible substrate 4 has the detection unit 40 arranged in a curved manner between the cylindrical part 21 of the holder 2 and the magnetic ring 5, and a part of the signal line unit 400 is led out to the outside of the holder 2. The detection unit 40 has a coil group formed by a wiring pattern, which is made up of multiple detection coils arranged in a predetermined direction. The detection unit 40 is rectangular in shape, with the direction in which the multiple detection coils are arranged being the longer side direction.

[0020] The signal line section 400 has a protruding portion 401 that projects from the detection section 40 in a direction perpendicular to the long side direction, and a linear portion 402 that extends from the protruding portion 401 in the direction of the long side. Due to the shape of this flexible substrate 4, as shown in Figure 5(b), the unnecessary area of ​​the base material 100 can be reduced and multiple flexible substrates 4 can be cut out, thereby improving the yield. The length of the linear portion 402 is, for example, 50 mm to 100 mm.

[0021] The linear portion 402, except for the base end which is near the protruding portion 401, has a portion including the tip that is led out to the outside of the holder 2. First to fourth electrodes 402a to 402d are formed on the tip of the linear portion 402, as shown in an enlarged view in Figure 1. The linear portion 402 of the flexible substrate 4 may be directly connected to the external device 8, or it may be connected to the external device 8 via a cable having multiple wires. Next, an example of the configuration of the detection unit 40 will be described in detail with reference to Figures 6 to 8.

[0022] Figure 6 is a cross-sectional view showing the layer structure of the flexible substrate 4. The flexible substrate 4 has a multilayer structure having first to fourth wiring layers 41 to 44, and in order from one side 4a which is on the outside of the curve when wrapped around the outer circumference of the cylindrical portion 21 to the other side 4b which is on the inside of the curve, a coverlay film 451, an adhesive layer 461, a first wiring layer 41, a first base film 471, a second wiring layer 42, an adhesive layer 462, a coverlay film 452, double-sided tape 48, a coverlay film 453, an adhesive layer 463, a third wiring layer 43, a second base film 472, a fourth wiring layer 44, an adhesive layer 464, and a coverlay film 454 are laminated.

[0023] The first wiring layer 41 and the second wiring layer 42 are wiring patterns formed by etching copper foil and are formed on the front surface 471a and back surface 471b of the first base film 471, respectively. Similarly, the third wiring layer 43 and the fourth wiring layer 44 are wiring patterns formed by etching copper foil and are formed on the front surface 472a and back surface 472b of the second base film 472, respectively. Coverlay films 451, 452, 453, and 454 are protective films attached to the first to fourth wiring layers 41 to 44 by adhesive layers 461, 462, 463, and 464. The first and second base films 471 and 472, and the coverlay films 451, 452, 453, and 454 are made of an insulating resin such as polyimide.

[0024] Figure 7(a) is a plan view showing the wiring pattern of the first wiring layer 41 formed on the surface 471a of the first base film 471. Figure 7(b) is a plan view showing the wiring pattern of the second wiring layer 42 as seen from the surface 471a side of the first base film 471. Figure 7(c) is a plan view showing the wiring pattern of the third wiring layer 43 formed on the surface 472a of the second base film 472. Figure 7(d) is a plan view showing the wiring pattern of the fourth wiring layer 44 as seen from the surface 472a side of the second base film 472.

[0025] In the first wiring layer 41, the first to tenth detection coils 410 to 419 are formed by a wiring pattern, aligned along the long side of the detection unit 40. The first and tenth detection coils 410 and 419 are triangular in shape, while the second to ninth detection coils 411 to 418 are parallelograms. Similarly, in the second wiring layer 42, the first to tenth detection coils 420 to 429 are formed by a wiring pattern, aligned along the long side of the detection unit 40. The first and tenth detection coils 420 and 429 are triangular in shape, while the second to eighth detection coils 421 to 428 are parallelograms.

[0026] In the third wiring layer 43, the first to tenth detection coils 430 to 439 are formed by a wiring pattern, aligned along the long side of the detection unit 40. The first and tenth detection coils 430 and 439 are triangular in shape, while the second to ninth detection coils 431 to 438 are parallelograms. Similarly, in the fourth wiring layer 44, the first to tenth detection coils 440 to 449 are formed by a wiring pattern, aligned along the long side of the detection unit 40. The first and tenth detection coils 440 and 449 are triangular in shape, while the second to ninth detection coils 441 to 448 are parallelograms.

[0027] The first to tenth detection coils 410 to 419 of the first wiring layer 41 and the first to tenth detection coils 440 to 449 of the fourth wiring layer 44 each have straight sections 410a to 419a and 440a to 449a, respectively, that are inclined at a predetermined angle (+45°) to one side with respect to the short side direction of the detection unit 40. The first to tenth detection coils 420 to 429 of the second wiring layer 42 and the first to tenth detection coils 430 to 439 of the third wiring layer 43 each have straight sections 420a to 429a and 430a to 439a, respectively, that are inclined at a predetermined angle (-45°) to the other side with respect to the short side direction of the detection unit 40.

[0028] Figure 8 is a schematic circuit diagram showing an example of an electrical circuit configuration consisting of a flexible circuit board 4, an oscillator 81, and a voltmeter 82. The first to tenth detection coils 410 to 419 of the first wiring layer 41 are connected in series to form the first coil group 4A, and the first to tenth detection coils 420 to 429 of the second wiring layer 42 are connected in series to form the second coil group 4B. Furthermore, the first to tenth detection coils 430 to 439 of the third wiring layer 43 are connected in series to form the third coil group 4C, and the first to tenth detection coils 440 to 449 of the fourth wiring layer 44 are connected in series to form the fourth coil group 4D.

[0029] The first coil group 4A and the third coil group 4C, as well as the second coil group 4B and the fourth coil group 4D, are connected in series between the first electrode 402a and the second electrode 402b, respectively. One end of each of the first coil group 4A and the second coil group 4B is connected to the first electrode 402a by the first signal line 491. One end of each of the third coil group 4C and the fourth coil group 4D is connected to the second electrode 402b by the second signal line 492.

[0030] A third signal line 493, which connects the other end of the first coil group 4A and the other end of the third coil group 4C in series, is connected to the third electrode 402c. A fourth signal line 494, which connects the other end of the second coil group 4B and the other end of the fourth coil group 4D in series, is connected to the fourth electrode 402d. The first to fourth signal lines 491 to 494 are formed in the signal line section 400 by a wiring pattern. The oscillator 81 applies an AC voltage between the first electrode 402a and the second electrode 402b. The voltmeter 82 measures the voltage between the third electrode 402c and the fourth electrode 402d.

[0031] When torque is applied to the rotating shaft 9, the permeability in the direction of +45 degrees relative to the axial direction decreases (or increases), and the permeability in the direction of -45 degrees relative to the axial direction increases (or decreases). Therefore, when torque is applied to the rotating shaft 9 while an AC voltage is applied from the oscillator 81, the inductance of the first coil group 4A and the fourth coil group 4D decreases (or increases), and the inductance of the second coil group 4B and the third coil group 4C increases (or decreases). As a result, the voltage measured by the voltmeter 82 changes, and the torque applied to the rotating shaft 9 can be detected based on this change in voltage.

[0032] Note that in Figures 7(a) to (d), the wiring patterns of the first to tenth detection coils 410 to 419, 420 to 429, 430 to 439, and 440 to 449 in the first to fourth wiring layers 41 to 44, as well as the wiring patterns of the first to fourth signal lines 491 to 494, are not shown.

[0033] The detection unit 40 is wrapped around the outer circumference of the cylindrical portion 21 of the holder 2, and the other side 4b is bonded to the outer surface 21a of the cylindrical portion 21 of the holder 2 with adhesive. The magnetic ring 5 is positioned to surround the outer circumference of the detection unit 40. The magnetic ring 5 increases the magnetic flux linked to each detection coil 410~419, 420~429, 430~439, 440~449, thereby increasing the sensitivity of the magnetostrictive torque sensor 1. A space is formed between one side 4a of the detection unit 40 and the inner surface 5a of the magnetic ring 5, preventing contact between the flexible substrate 4 and the magnetic ring 5. The entry of foreign matter into this space is prevented by the lip seal 7.

[0034] As shown in an enlarged view in Figure 4, the lip seal 7 has a core metal 71 and a rubber material 72 that is vulcanized and bonded to the core metal 71, with a portion of the rubber material 72 forming a lip portion 721 that elastically contacts the cylindrical portion 21 of the holder 2. On the inner circumferential surface 5a of the magnetic ring 5, a stepped portion 50 into which the lip seal 7 is fitted is formed at the end of the small diameter portion 52 opposite to the large diameter portion 51.

[0035] Figure 9(a) is a configuration diagram showing the holder 2 with the cover member 3 and flexible substrate 4 attached, viewed from the axial direction. Figure 9(b) is a configuration diagram showing the state in Figure 9(a) with the cover member 3 omitted. Figure 10(a) is a configuration diagram showing the recess 22 of the holder 2, viewed from the axial direction. Figure 10(b) is a perspective view showing the peripheral part of the recess 22. Figures 11(a) and (b) are perspective views showing the cover member 3 from different directions. Figure 10(b) shows a state in which a part of the annular wall 23 on the front side in the direction of illustration of the recess 22 has been cut off.

[0036] The recess 22 accommodates a portion of the linear portion 402 in the vicinity of the protruding portion 401. The holder 2 has a plate portion housing portion 24 formed on one axial side of the recess 22 for housing the plate portion 31 of the cover member 3. The cover member 3 is prevented from the plate portion 31 coming out of the plate portion housing portion 24 by the magnetic ring 5. The recess 22 is formed between the first wall portion 221 and the second wall portion 222 of the holder 2. The first wall portion 221 and the second wall portion 222 are provided protruding axially from the bottom surface 22a of the recess 22. The plate portion 31 of the cover member 3 abuts against the top surface 221a of the first wall portion 221 and the top surface 222a of the second wall portion 222. The linear portion 402 is bent inside the recess 22 and led out to the outside of the holder 2 so as to extend in a radial direction perpendicular to the circumferential direction of the cylindrical portion 21.

[0037] The first wall portion 221 and the second wall portion 222 face each other via a recess 22. The surface 221b of the first wall portion 221 facing the second wall portion 222, and the surface 222b of the second wall portion 222 facing the first wall portion 221, are the inner surfaces of the recess 22. The linear portion 402 of the flexible substrate 4 is curved along the surface 221b of the first wall portion 221 and is sandwiched between the surface 221b of the first wall portion 221 and the outer peripheral surface 32a of the convex portion 32 of the cover member 3. The surfaces of the linear portion 402 within the recess 22 (one surface 4a and the other surface 4b) are parallel to the central axis C of the cylindrical portion 21, and the linear portion 402 is curved in the thickness direction within the recess 22.

[0038] Because the linear portion 402 is curved in this way, it is possible to prevent a part of the detection portion 40 from lifting up from the cylindrical portion 21 due to the restoring force of the curved linear portion 402. In other words, if the linear portion 402 were to extend in a direction perpendicular to the long side direction of the detection portion 40, curving the linear portion 402 near the detection portion 40 would cause the detection portion 40 near the base of the linear portion 402 to lift up from the cylindrical portion 21 due to the restoring force of the linear portion 402, which could reduce the detection accuracy. However, in this embodiment, since the signal line portion 400 extends from the protruding portion 401 along the long side direction of the detection portion 40, such lifting can be suppressed.

[0039] The opposing surface 221b of the first wall portion 221 includes an outlet-side guide surface 221c that contacts the linear portion 402 near the exit of the recess 22, which is on the outer peripheral end side of the holder 2, an inlet-side guide surface 221d that contacts the linear portion 402 near the entrance of the recess 22 in the vicinity of the cylindrical portion 21, and an inclined guide surface 221e between the outlet-side guide surface 221c and the inlet-side guide surface 221d. The linear portion 402 extends within the recess 22 along the inlet-side guide surface 221d, the inclined guide surface 221e, and the outlet-side guide surface 221c.

[0040] The outlet-side guide surface 221c is a plane aligned perpendicular to the central axis C of the cylindrical portion 21. The inlet-side guide surface 221d is a plane parallel to the outlet-side guide surface 221c and is offset from the outlet-side guide surface 221c in a direction away from the second wall portion 222. The inclined guide surface 221e is an inclined surface inclined perpendicular to the central axis C of the cylindrical portion 21 and forms an obtuse angle with the inlet-side guide surface 221d and the outlet-side guide surface 221c.

[0041] As shown in Figure 11(a), the protrusion 32 of the cover member 3 has a plurality of projections 321, 322 that are pressed against the opposing surface 222b of the second wall portion 222. When the plurality of projections 321, 322 are pressed against the opposing surface 222b of the second wall portion 222, the protrusion 32 elastically deforms, and the restoring force biases the protrusion 32 toward the first wall portion 221.

[0042] Because the linear portion 402 is held within the recess 22, even if the linear portion 402 outside the holder 2 is pulled, the tensile force is prevented from reaching the detection portion 40 via the protruding portion 401, thereby suppressing a decrease in the detection accuracy of the magnetostrictive torque sensor 1. Furthermore, since the linear portion 402 is led out to the outside of the holder 2 so as to extend in the radial direction perpendicular to the circumferential direction of the cylindrical portion 21, even if the linear portion 402 is pulled in the direction of extension of the linear portion 402 shown by arrow A in Figure 9(b), the generation of a rotational moment in the holder 2 due to that tensile force is suppressed.

[0043] Next, we will describe the fixing structure of the holder 2 and the magnetic ring 5 using multiple fasteners 6. Here, we will describe the case where the fasteners 6 are spring pins. The holder 2 and the magnetic ring 5 are fixed together by the fasteners 6, which penetrate the annular wall 23 of the holder 2 and are inserted into the fastening holes 510 of the magnetic ring 5.

[0044] Figure 12(a) is a perspective view showing the fastener 6. Figure 12(b) is a cross-sectional view of the fastener 6 in a section perpendicular to the longitudinal direction. The fastener 6 has a C-shaped cross-section with a slit 60 extending in the longitudinal direction. Tapered portions 61 are formed at both ends of the fastener 6. The fastener 6 is made of metal, such as spring steel or stainless steel.

[0045] Figure 13 is a perspective view showing the holder 2 and magnetic ring 5 together with the fastener 6. The annular wall 23 of the holder 2 has a plurality of through holes 231 that penetrate radially between the outer circumferential surface 23b and the inner circumferential surface 23a of the annular wall 23. The large diameter portion 51 of the magnetic ring 5 has a plurality of fastening holes 510 that open to the outer circumferential surface 51a. The inner diameter D1 of the through holes 231 and the inner diameter D2 of the fastening holes 510 are formed to be smaller than the outer diameter D3 of the fastener 6 before it is inserted into the through holes 231 and fastening holes 510.

[0046] When the large-diameter portion 51 of the magnetic ring 5 is fitted into the annular groove 230, the multiple through holes 231 and the retaining holes 510 communicate with each other. The fastener 6 elastically shrinks in diameter as the width of the slit 60 narrows, and is inserted into the through holes 231 and the retaining holes 510. As shown in Figure 4, the retaining holes 510 are blind holes that do not penetrate the magnetic ring 5 radially, and the fastener 6 is inserted to the deepest part of the retaining holes 510. Once the fastener 6 is inserted into the through holes 231 and the retaining holes 510, the restoring force of the elastically deformed fastener 6 causes the outer circumferential surface 6a of the fastener 6 to elastically contact the inner surface 231a of the through holes 231 and the inner circumferential surface 510a of the retaining holes 510.

[0047] In this embodiment, the holder 2 and the magnetic ring 5 are fixed to each other by five fasteners 6. In this embodiment, two of the five fasteners 6 are longer than the other three fasteners 6 and protrude radially from the outer circumferential surface 23b of the annular wall 23. The length of the other three fasteners 6 is equivalent to the combined length of the through hole 231 and the fastening hole 510. The two fasteners 6 that protrude radially from the outer circumferential surface 23b of the annular wall 23 also function as anti-rotation members that prevent the holder 2 and the magnetic ring 5 from rotating relative to the mounting object.

[0048] Figure 14 is an explanatory diagram showing the magnetostrictive torque sensor 1 mounted on the housing 90. The housing 90 has a fitting hole 91 into which the annular wall 23 of the holder 2 fits, and a plurality of slit holes 92 extending radially from the inner circumferential surface 91a of the fitting hole 91 along a direction perpendicular to the rotation axis O of the rotating shaft 9. Two fasteners 6 protruding from the annular wall 23 of the holder 2 engage with these slit holes 92, respectively, preventing the holder 2 and magnetic ring 5 from rotating relative to the housing 90. The other three fasteners 6 that do not protrude from the annular wall 23 are prevented from coming out of the through hole 231 by the inner circumferential surface 91a of the fitting hole 91. In Figure 14, these three fasteners 6 are shown with dashed lines.

[0049] Furthermore, only one of the five fasteners 6 may protrude from the annular wall 23 of the holder 2. Alternatively, all of the fasteners 6 may protrude from the annular wall 23. The fasteners 6 that protrude from the annular wall 23 can function as anti-rotation members.

[0050] Furthermore, while one fastener 6 may be used to secure the holder 2 and the magnetic ring 5, it is desirable to secure the holder 2 and the magnetic ring 5 with multiple fasteners 6 to ensure sufficient fixing strength. When securing the holder 2 and the magnetic ring 5 with a single fastener 6, it is desirable to position the fastener 6 on the opposite side of the recess 22 with respect to the central axis C.

[0051] (Effects of the embodiment) According to the embodiment described above, since the linear portion 402 of the flexible substrate 4 is led out to the outside of the holder 2, there is no need to connect the flexible substrate 4 to a cable inside the holder 2, and the magnetostrictive torque sensor 1 can be miniaturized. Therefore, even when the installation space around the rotating shaft 9 is narrow, it is easier to position the magnetostrictive torque sensor 1. In addition, the holder 2 and the magnetic ring 5 can be securely fixed by the fastener 6, and the holder 2 and magnetic ring 5 can be prevented from rotating relative to the housing 90. Here, since both the magnetic ring 5 and the fastener 6 are made of metal, compared to, for example, when a part of the holder 2 is engaged with the housing 90 to prevent rotation, wear can be suppressed even when subjected to vibration, and durability can be improved.

[0052] (Summary of the embodiments) Next, the technical concept understood from 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.

[0053] [1] A magnetostrictive torque sensor (1) is mounted around a rotating shaft (9) having a magnetostrictive effect and detects torque transmitted by the rotating shaft (9), comprising: a resin holder (2) having a cylindrical portion (21) with a cavity (20) formed in the center through which the rotating shaft (9) is inserted; a detection unit (40) having a coil group (4A~4D) formed by a wiring pattern, which is a combination of a plurality of detection coils (410~419, 420~429, 430~439, 440~449) arranged in a predetermined direction; and a flexible substrate (4) having a signal line portion (400) formed by a wiring pattern, which is a plurality of signal lines (491~494) that electrically connect the coil group (4A~4D) to an external device (8); and a flexible substrate (4) having a signal line portion (400) formed by a wiring pattern, which is a combination of a plurality of signal lines (491~494) that electrically connect the coil group (4A~4D) to an external device (8); and a flexible substrate (4) arranged on the outer circumference of the cylindrical portion (21) of the holder (2) A magnetostrictive torque sensor (1) comprises a cylindrical magnetic ring (5) made of a magnetic material, wherein the detection unit (40) is curved and positioned between the cylindrical portion (21) of the holder (2) and the magnetic ring (5), a portion of the signal line (400) is led out to the outside of the holder (2), the holder (2) has an annular wall (23) surrounding the outer circumference of one axial end of the magnetic ring (5), the magnetic ring (5) has a retaining hole (510) formed in its outer circumferential surface (51a) facing the inner circumferential surface (23a) of the annular wall (23), and the holder (2) and the magnetic ring (5) are fixed together by an axial fastener (6) that penetrates the annular wall (23) and is inserted into the retaining hole (510) of the magnetic ring (5).

[0054] [2] The magnetostrictive torque sensor (1) described in [1] above, wherein the detection unit (40) is rectangular in shape with the arrangement of the plurality of detection coils (410~419, 420~429, 430~439, 440~449) in the direction of the longer side, and the signal line unit (400) has a projection (401) that protrudes from the detection unit (40) in a direction perpendicular to the direction of the longer side, and a linear part (402) that extends from the projection (401) in the direction of the longer side, and a part of the linear part (402) is led out to the outside of the holder (2).

[0055] [3] The magnetostrictive torque sensor (1) according to [2] above, wherein the holder (2) has a recess (22) that accommodates a part of the linear portion (402), and the linear portion (402) is bent inside the recess (22) and led out to the outside of the holder (2) in a direction perpendicular to the circumferential direction of the cylindrical portion (21).

[0056] [4] The magnetostrictive torque sensor (1) according to [3], further comprising a cover member (3) having a protrusion (32) that fits into the recess (22) of the holder (2), wherein the linear portion (402) is sandwiched between the inner surface (opposing surface 221b) of the recess (22) and the outer peripheral surface (32a) of the protrusion (32).

[0057] [5] The magnetostrictive torque sensor (1) according to [4] above, wherein the movement of the cover member (3) in the direction in which the protrusion (32) detaches from the recess (22) of the holder (2) is restricted by the magnetic ring (5).

[0058] [6] The magnetostrictive torque sensor (1) according to [5] above, wherein the detection portion (40) of the flexible substrate (4) is bonded to the cylindrical portion (21) of the holder (2), and a space is formed between the detection portion (40) and the magnetic ring (5).

[0059] [7] The magnetostrictive torque sensor (1) according to [1] above, wherein the fastener (6) protrudes from the outer peripheral surface (23b) of the annular wall (23), and the protruding portion of the fastener (6) engages with the mounting object (housing 90), thereby preventing the holder (2) and the magnetic ring (5) from rotating relative to the mounting object (90).

[0060] Although embodiments of the present invention have been described above, these embodiments do not limit the invention as defined in the claims. Furthermore, it should be noted that not all combinations of features described in the embodiments are necessarily essential for solving the problem of the invention.

[0061] Furthermore, the present invention can be implemented with appropriate modifications without departing from its spirit. For example, although the above embodiment describes the case where the fastener 6 is a spring pin, the invention is not limited to this, and the fastener 6 may be a bolt. In this case, the fastening hole 510 of the magnetic ring 5 is formed as a screw hole, and the male thread of the fastener 6 is screwed into this screw hole. [Explanation of symbols]

[0062] 1…Magnetostrictive torque sensor 2… Holder 20...Cavity 21...Cylindrical section 22…recess 23... Ring Wall 23a…Inner peripheral surface 231…Through hole 3…Cover component 32... protruding part 4… Flexible circuit board 40...Detection unit 400... Signal line section 401...Protrusion 402... Linear part 491-494...1st to 4th signal lines 410~419, 420~429, 430~439, 440~449… Detection coil 4A~4D...The first to fourth coil groups 5…Magnetic ring 51a...Outer surface 510… Fastening hole 6… Fasteners 8...External device 9…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, A resin holder having a cylindrical portion with a cavity formed in the center through which the aforementioned rotating shaft is inserted, A flexible substrate having a detection unit formed by a wiring pattern of a coil group consisting of multiple detection coils arranged in a predetermined direction, and a signal line unit formed by a wiring pattern of multiple signal lines that electrically connect the coil group to an external device, The holder comprises a cylindrical magnetic ring made of a soft magnetic material arranged on the outer circumference of the cylindrical portion of the holder, The flexible substrate has the detection unit arranged in a curved manner between the cylindrical portion of the holder and the magnetic ring, and a portion of the signal line is led out to the outside of the holder. The holder has an annular wall surrounding the outer circumference of one axial end of the magnetic ring, The magnetic ring has a retaining hole formed in its outer surface that opens to the inner surface of the annular wall, The holder and the magnetic ring are fixed together by an axial fastener that penetrates the annular wall and is inserted into the fastening hole of the magnetic ring. Magnetostrictive torque sensor.

2. The detection unit has a rectangular shape in which the direction in which the plurality of detection coils are arranged is the direction of the longer side. The signal line section has a projection that protrudes from the detection section in a direction perpendicular to the direction of the long side, and a linear section that extends from the projection in the direction of the long side. A portion of the linear portion is led out to the outside of the holder. The magnetostrictive torque sensor according to claim 1.

3. The holder has a recess that accommodates a part of the linear portion, The linear portion is bent inside the recess and led out to the outside of the holder in a direction perpendicular to the circumferential direction of the cylindrical portion. The magnetostrictive torque sensor according to claim 2.

4. The holder further comprises a cover member having a protrusion that fits into the recess, The linear portion is sandwiched between the inner surface of the recess and the outer surface of the protrusion. The magnetostrictive torque sensor according to claim 3.

5. The movement of the cover member in the direction in which the protrusion of the holder detaches from the recess is restricted by the magnetic ring. The magnetostrictive torque sensor according to claim 4.

6. The detection portion of the flexible substrate is bonded to the cylindrical portion of the holder, and a space is formed between the detection portion and the magnetic ring. The magnetostrictive torque sensor according to claim 1.

7. The fastener protrudes from the outer surface of the annular wall, The protruding portion of the fastener engages with the object to be attached, thereby preventing the holder and the magnetic ring from rotating relative to the object to be attached. The magnetostrictive torque sensor according to claim 1.

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