Magnetostrictive torque measurement device

Abstract

Provided is a magnetostrictive torque measurement device that makes it easy to ensure accuracy of torque measurement, sensitivity of torque measurement, or both. A magnetostrictive torque measurement device 1 comprises: a rotary shaft 2 that has a detected part 4 that has magnetostrictive characteristics at a portion in the axial direction of an outer circumferential surface; and a magnetostrictive torque sensor 3. The magnetostrictive torque sensor 3 includes: a holder 5 that is formed from a synthetic resin, has an inner circumferential surface 7 that is loosely fitted in the radial direction onto the outside of the detected part 4 so as not to rattle, and does not rotate even during use; and a coil unit 6 that is held by the holder 5 and has a detection part 12 that includes a plurality of detection coils 11 (11a–11d).

Description

Magnetostrictive torque measuring device

[0001] The present disclosure relates to a magnetostrictive torque measurement device that measures torque applied to a rotating shaft.

[0002] A magnetostrictive torque measuring device is comprised of a rotating shaft having magnetostrictive properties and a magnetostrictive torque sensor that measures the torque applied to the rotating shaft by utilizing the inverse magnetostrictive effect that occurs in the rotating shaft when torque is applied. Such a magnetostrictive torque measuring device has been known for some time, for example as disclosed in Japanese Patent Laid-Open No. 2023-127315.

[0003] In the conventional magnetostrictive torque measuring device disclosed in Japanese Patent Application Laid-Open No. 2023-127315, the magnetostrictive torque sensor includes a holder and a coil unit.

[0004] The holder is made of synthetic resin and has an annular shape. It is placed around the rotating shaft and is supported by structural elements such as a housing or frame so that it does not rotate even during use. The coil unit has a detection section including multiple detection coils and is held in the holder. The magnetostrictive torque sensor measures the torque applied to the rotating shaft based on changes in the inductance of the multiple detection coils.

[0005] Japanese Patent Application Laid-Open No. 2023-127315

[0006] In applications where the rotating shaft is stationary or rotates at low speeds, such as in electrically assisted bicycles including e-bikes, torque measuring devices are required to detect smaller torques than torque measuring devices for measuring the transmission torque of the rotating shaft that constitutes the transmission of an automobile.

[0007] In the conventional magnetostrictive torque measuring device described in JP 2023-127315 A, a certain radial gap (for example, approximately 0.75 mm to 1.0 mm) is provided between the outer peripheral surface of the rotating shaft and the inner peripheral surface of the holder to prevent contact between the outer peripheral surface of the rotating shaft and the inner peripheral surface of the holder even when the rotating shaft is wobbled (tilted) or bent. The radial distance between the outer peripheral surface of the rotating shaft and the detection unit of the coil unit needs to be equal to or larger than this radial gap.

[0008] If the radial distance between the outer surface of the rotating shaft and the detection part of the coil unit is large, a large amount of the magnetic flux generated by the detection part of the coil unit will not pass through the outer surface of the rotating shaft, making it difficult to improve the accuracy and sensitivity of torque measurement.

[0009] An object of the present disclosure is to provide a magnetostrictive torque measurement device that can easily ensure torque measurement accuracy, torque measurement sensitivity, or both.

[0010] A magnetostrictive torque measurement device according to one aspect of the present disclosure includes a rotating shaft having a detection portion having magnetostrictive properties on a part of the outer peripheral surface in the axial direction, and a magnetostrictive torque sensor.

[0011] In particular, in one aspect of the magnetostrictive torque measuring device of the present disclosure, the magnetostrictive torque sensor comprises: a holder made of synthetic resin, having an inner circumferential surface that is fitted onto the detected portion with a clearance fit that does not cause any radial play, and that does not rotate during use; and a coil unit that has a detecting portion including a plurality of detecting coils and is held by the holder.

[0012] In the magnetostrictive torque measuring device according to one aspect of the present disclosure, the radial dimension of the gap between the inner peripheral surface of the holder and the portion to be detected is 0.05 mm or more and 0.2 mm or less, preferably 0.1 mm or more and 0.15 mm or less.

[0013] In the magnetostrictive torque measuring device according to one aspect of the present disclosure, the maximum rotation speed of the rotating shaft is 300 min -1 (rpm) or less, preferably 200 min -1 The following is the result.

[0014] In one aspect of the magnetostrictive torque measurement device of the present disclosure, grease is provided to lubricate the gap between the inner circumferential surface of the holder and the part to be detected.

[0015] In the magnetostrictive torque measuring device according to one aspect of the present disclosure, the detection target portion is configured by a shot peening-treated portion. Note that the shot peening-treated portion is a portion that has been subjected to shot peening.

[0016] According to the magnetostrictive torque measurement device of one aspect of the present disclosure, it is easy to ensure the accuracy of torque measurement, the sensitivity of torque measurement, or both.

[0017] Fig. 1 is a schematic cross-sectional view of a magnetostrictive torque measurement device according to an embodiment of the present disclosure, taken along an imaginary plane including the central axis of a rotation shaft. Fig. 2 is a schematic diagram showing a detection circuit including four detection coils. Fig. 3 is a plan view of a flexible substrate.

[0018] An example of an embodiment of the present disclosure will be described with reference to FIGS. 1 to 3. FIG.

[0019] The magnetostrictive torque measuring device 1 of this example includes a rotating shaft 2 and a magnetostrictive torque sensor 3 , and has the function of measuring the torque transmitted by the rotating shaft 2 .

[0020] The rotating shaft 2 broadly includes rotating shafts of various mechanical devices as long as it has a detection target 4 with magnetostrictive properties on a portion of the outer circumferential surface in the axial direction. The rotating shaft 2 is not limited to these, but may be applied to, for example, a crankshaft of a bicycle, a hub of a front or rear wheel, or a rotating shaft of an automobile transmission. The bicycle also includes electrically assisted bicycles, including e-bikes.

[0021] The rotating shaft 2 has a detection target 4 having magnetostrictive properties on a part of the outer peripheral surface in the axial direction. The detection target 4 is formed of a cylindrical surface whose outer diameter does not change in the axial direction from a macroscopic perspective (macroscopic perspective).

[0022] In the following description, unless otherwise specified, the axial, radial, and circumferential directions of the magnetostrictive torque measurement device 1 refer to the axial, radial, and circumferential directions of the rotating shaft 2. The axial, radial, and circumferential directions of the rotating shaft 2 coincide with the axial, radial, and circumferential directions of the holder 5 that constitutes the magnetostrictive torque sensor 3, and also coincide with the axial, radial, and circumferential directions of the coil unit 6 that constitutes the magnetostrictive torque sensor 3. In Figure 1, one axial side corresponds to the left side of Figure 1, and the other axial side corresponds to the right side of Figure 1.

[0023] The rotating shaft 2 is made of a material having magnetostrictive properties, in part or in whole, including at least the detection target portion 4. Specifically, the rotating shaft 2 can be made of an iron alloy such as, but not limited to, SC (carbon steel for mechanical construction), SUS (stainless steel), SCr (chromium steel), SCM (chromium molybdenum steel), or SNCM (nickel chromium molybdenum steel).

[0024] The rotating shaft 2 is rotatably supported via a bearing (not shown) on a structural element such as a housing or a frame that does not rotate even during use.

[0025] The detection target portion 4 can be configured with a shot peening-treated portion that has been subjected to shot peening, or can be configured with a non-shot peening-treated portion that has not been subjected to shot peening. When the detection target portion 4 is configured with a shot peening-treated portion, the detection target portion 4 can include fine irregularities formed by the shot peening treatment. Therefore, although the detection target portion 4 is configured with a cylindrical surface macroscopically (macroscopically), due to the presence of the fine irregularities, it is configured with a non-cylindrical surface microscopically (microscopically).

[0026] In this example, the detection target 4 is formed by a shot peening treatment. That is, by subjecting the detection target 4 to shot peening treatment, the magnetic properties of the detection target 4 are improved, thereby increasing the sensitivity of torque measurement and reducing hysteresis. In this case, the detection target 4 has many minute recesses (dimples) formed by the shot peening treatment. The recesses can function as grease retaining portions (grease reservoirs) for retaining grease that lubricates the space between the detection target 4 of the rotating shaft 2 and the inner peripheral surface 7 of the holder 5.

[0027] The maximum rotation speed of the rotating shaft 2 is, but is not limited to, 300 min -1 (rpm) or less, and -1 It is more preferable that the maximum rotation speed of the rotating shaft 2 is 300 min or less. -1If it is larger than this, there is a possibility that the wear between the detection target part 4 and the holder 5 will be significant.

[0028] The magnetostrictive torque sensor 3 includes a holder 5 and a coil unit 6 .

[0029] The holder 5 is made of synthetic resin and has an inner circumferential surface 7 that is fitted onto the detection target 4 with a clearance fit that leaves no play in the radial direction, and does not rotate during use. The inner circumferential surface 7 of the holder 5 has a cylindrical shape whose inner diameter does not change in the axial direction, and is disposed opposite the detection target 4.

[0030] The synthetic resin constituting the holder 5 is not limited to, but may be, for example, an epoxy resin or a thermoplastic resin such as PPS (polyphenylene sulfide), PA (polyamide), or PPA (polyphthalamide). Furthermore, reinforcing fibers may be mixed into the synthetic resin constituting the holder 5 as needed.

[0031] The holder 5 has an inner surface 7 that fits snugly around the detected part 4 without any radial play, and its shape is not limited as long as it is configured to hold the coil unit 6.

[0032] The structure for holding the coil unit 6 in the holder 5 can be a structure in which the coil unit 6 is assembled to the holder 5 that is made separately from the coil unit 6, or a structure in which the coil unit 6 is embedded in the holder 5 at the same time that the holder 5 is manufactured by injection molding of synthetic resin. In this example, a structure in which the coil unit 6 is assembled to the holder 5 that is made separately from the coil unit 6 is employed.

[0033] In a configuration in which the coil unit 6 is assembled to the holder 5, the holder 5 has a cylindrical bobbin portion 8 that is arranged around the rotation shaft 2. The detection portion 12 of the coil unit 6 can be held around the bobbin portion 8. In this configuration, the inner peripheral surface 7 of the holder 5 is formed by the inner peripheral surface of the bobbin portion 8.

[0034] The holder 5 is positioned radially relative to the detection target 4 by fitting the inner circumferential surface 7 onto the detection target 4 with a clearance fit that does not cause any radial play.

[0035] The radial dimension of the gap between inner circumferential surface 7 of holder 5 and detected portion 4 can be set to a size similar to the radial dimension of the gap between a shaft having an outer diameter similar to that of rotating shaft 2 and a sliding bearing arranged around said shaft. Specifically, the radial dimension of the gap between inner circumferential surface 7 of holder 5 and detected portion 4, i.e., the difference between the inner diameter of inner circumferential surface 7 of holder 5 and the outer diameter of detected portion 4, is not limited to, but can be 0.05 mm or more and 0.2 mm or less, and preferably 0.1 mm or more and 0.15 mm or less, at room temperature (for example, 25°C).

[0036] With the inner peripheral surface 7 of the holder 5 fitted onto the detection target portion 4 with a clearance fit that leaves no radial play, the holder 5 is prevented from rotating relative to a structural element that does not rotate during use, such as a housing or a frame, and from displacing relative axially. Specifically, the holder 5 is positioned axially and circumferentially relative to the structural element by engaging an engaging portion provided on a part of the holder 5 with the structural element, or by bridging an engaging member such as a pin between the holder 5 and the structural element.

[0037] The magnetostrictive torque measurement device 1 is radially positioned with respect to the rotating shaft 2 by externally fitting the inner circumferential surface 7 of the holder 5 onto the detection target 4 with a clearance fit that leaves no radial play, so there is no need to radially position the holder 5 with respect to the structural element. In the magnetostrictive torque measurement device 1 of this example, a radial gap is provided between the structural element and the back yoke 21 that is externally fitted and fixed to the holder 5. Therefore, even if the rotating shaft 2 wobbles (tilts) or bends while driving an electrically assisted bicycle incorporating the magnetostrictive torque measurement device 1, the magnetostrictive torque sensor 3 arranged around the rotating shaft 2 can be prevented from strongly hitting the structural element in the radial direction.

[0038] In this example, the holder 5 optionally or additionally includes a first outward flange portion 9 extending radially outward from the end on one axial side of the bobbin portion 8 around the entire circumference, and a second outward flange portion 10 extending radially outward from the end on the other axial side of the bobbin portion 8 around the entire circumference.

[0039] The first outward flange portion 9 has an engaging portion that engages with the structural element, an engaging member such as the pin, or both when supporting the holder 5 on the structural element, and a wiring accommodating portion that accommodates cables, signal lines, or both that electrically connect the detection coils 11a to 11d that constitute the coil unit 6 to the external device 16.

[0040] The second outward flange portion 10 has a function of holding the back yoke 21 when the back yoke 21 is provided.

[0041] The first outward flange portion 9 and the second outward flange portion 10 can each have any outer diameter depending on their function. In this example, the outer diameter of the first outward flange portion 9 is larger than the outer diameter of the second outward flange portion 10. However, the outer diameter of the first outward flange portion 9 can also be the same as or smaller than the outer diameter of the second outward flange portion 10. Furthermore, depending on the structure and arrangement of the engaging portions for engaging the holder 5 with the structural elements and engaging members, the arrangement of cables and signal lines, etc., it is also possible to omit the first outward flange portion 9, the second outward flange portion 10, or both.

[0042] The coil unit 6 has a detection section 12 including a plurality of detection coils 11 and is held by a holder 5 .

[0043] The magnetostrictive torque measuring device 1 uses multiple detection coils 11 to detect changes in the magnetic permeability of the rotating shaft 2 that occur when the rotating shaft 2 transmits torque based on the inverse magnetostrictive effect, and measures the torque transmitted by the rotating shaft 2.

[0044] The configuration of the coil unit 6 is not particularly limited as long as it can have a detection section 12 made up of a plurality of detection coils 11. For example, the coil unit 6 can be made up of a flexible substrate 13, and the plurality of detection coils 11 can be made up of a wiring pattern formed on a wiring layer. Alternatively, the coil unit 6 can be made up of a coil holder (bobbin) made of synthetic resin and a plurality of detection coils made by winding insulated wire around the coil holder.

[0045] In this example, the coil unit 6 is configured by a flexible substrate 13, and the plurality of detection coils 11 are configured by wiring patterns formed on a wiring layer.

[0046] The flexible substrate 13 includes a detection section 12 on which a plurality of detection coils 11 are arranged, and the detection section 12 is configured in a cylindrical or partially cylindrical shape.

[0047] In the unfolded state of the flexible substrate 13 as shown in Fig. 3, the detection unit 12 is configured in a strip-like or rectangular plate-like shape. The detection unit 12 is configured in a cylindrical shape or a notched cylindrical shape having a discontinuous portion at one location in the circumferential direction by wrapping the detection unit 12 in a strip-like or rectangular plate-like shape as shown in Fig. 3 around the bobbin portion 8 of the holder 5.

[0048] Any means may be used to hold the coil unit 6 in the holder 5. In this example, the coil unit 6 is held in the holder 5 by fixing the inner circumferential surface of the detection portion 12 to the outer circumferential surface of the bobbin portion 8 with an adhesive. However, the coil unit 6 can also be held in the holder 5 by joining both circumferential ends of the detection portion 12 of the flexible substrate 13 wrapped around the bobbin portion 8 with an adhesive or adhesive tape, or by wrapping a restraining band around the detection portion 12 of the flexible substrate 13 wrapped around the bobbin portion 8.

[0049] The detection unit 12 may have any structure as long as it can form a bridge circuit together with the oscillator 17 and voltmeter 18 of the external device 16. Furthermore, the bridge circuit itself formed by the detection unit 12, oscillator 17, and voltmeter 18 may also have any structure. In this example, although not limited thereto, the detection unit 12 has four detection coils 11a to 11d as the multiple detection coils 11. As shown in FIG. 2 , each of the detection coils 11a to 11d is formed by arranging multiple coil pieces 14a to 14d, 15a to 15d in the circumferential direction (the direction of the long sides of the detection unit 12 when the flexible substrate 13 is in the unfolded state).

[0050] Specifically, the first detection coil 11a is constructed by connecting in series a plurality of coil pieces 14a, 15a arranged in the circumferential direction, the second detection coil 11b is constructed by connecting in series a plurality of coil pieces 14b, 15b arranged in the circumferential direction, the third detection coil 11c is constructed by connecting in series a plurality of coil pieces 14c, 15c arranged in the circumferential direction, and the fourth detection coil 11d is constructed by connecting in series a plurality of coil pieces 14d, 15d arranged in the circumferential direction.

[0051] Of the coil pieces 14a to 14d and 15a to 15d, the coil pieces 14a to 14d located at both ends in the circumferential direction are configured by arranging the wiring pattern so as to be wound in an approximately triangular shape when viewed from the radial direction, and the remaining coil pieces 15a to 15d are configured by arranging the wiring pattern so as to be wound in an approximately parallelogram shape when viewed from the radial direction.

[0052] The coil pieces 14a and 15a constituting the first detector coil 11a and the coil pieces 14c and 15c constituting the third detector coil 11c have straight line portions inclined at a predetermined angle (for example, +45 degrees) in a predetermined direction with respect to the axial direction of the rotation shaft 2 (the direction of the short side of the detector 12 when the flexible substrate 13 is in the unfolded state). The coil pieces 14b and 15b constituting the second detector coil 11b and the coil pieces 14d and 15d constituting the fourth detector coil 11d have straight line portions inclined at a predetermined angle (for example, −45 degrees) in a direction opposite to the predetermined direction with respect to the axial direction of the rotation shaft 2.

[0053] The four detection coils 11 a to 11 d are electrically connected to an external device 16 .

[0054] The external device 16 includes an oscillator 17 that applies a voltage between two points and a voltmeter 18 that detects the voltage between the two points. The oscillator 17 and the voltmeter 18, together with the detector 12 of the coil unit 6 of this example, form a bridge circuit.

[0055] There are no particular limitations on the manner in which the detection coils 11a to 11d are electrically connected to the external device 16. In this example, the detection coils 11a to 11d are electrically connected to the external device 16 by signal lines 19a to 19d (see FIG. 2) formed on the wiring layer of the flexible substrate 13 and a cable connected to the external device 16.

[0056] The flexible substrate 13 of this example includes a band-shaped signal line portion 20 that is drawn out in the radial direction, the axial direction, or both directions from the detection portion 12. The signal line portion 20 has four stacked signal lines 19a to 19d.

[0057] Of the four signal lines 19a to 19d, the first signal line 19a connects one end of the first detection coil 11a and one end of the second detection coil 11b in series, and is electrically connected to one terminal of the oscillator 17 via the cable.

[0058] The second signal line 19b connects one end of the third detection coil 11c and one end of the fourth detection coil 11d in series, and is electrically connected to the other terminal of the oscillator 17 via the cable.

[0059] The third signal line 19c connects the other end of the first detection coil 11a and the other end of the third detection coil 11c in series, and is electrically connected to one terminal of the voltmeter 18 via the cable.

[0060] The fourth signal line 19d connects the other end of the second detection coil 11b and the other end of the fourth detection coil 11d in series, and is electrically connected to the other terminal of the voltmeter 18 via the cable.

[0061] The oscillator 17 applies an AC voltage between a contact A between one end of the first detection coil 11a and one end of the second detection coil 11b, and a contact B between one end of the third detection coil 11c and one end of the fourth detection coil 11d. The voltmeter 18 detects the voltage between a contact C between the other end of the first detection coil 11a and the other end of the third detection coil 11c, and a contact D between the other end of the second detection coil 11b and the other end of the fourth detection coil 11d. That is, in this example, a bridge circuit is formed by the four detection coils 11a to 11d that make up the detection unit 12, the oscillator 17, and the voltmeter 18.

[0062] When torque T is applied to the rotating shaft 2, stresses σ with opposite signs act on the outer circumferential surface of the rotating shaft 2 in a direction inclined at +45° with respect to the axial direction and in a direction inclined at -45° with respect to the axial direction. Due to the inverse magnetostrictive effect, the magnetic permeability increases in the direction in which tensile stress (+σ) acts, and decreases in the direction in which compressive stress (-σ) acts. In the magnetostrictive torque sensor 3 of this example, the voltage of the bridge circuit, which changes in accordance with the change in magnetic permeability of the rotating shaft 2, is detected by the voltmeter 18, and the direction and magnitude of the torque transmitted by the rotating shaft 2 are determined based on this detected value.

[0063] The magnetostrictive torque sensor 3 of this example includes, as an optional component, a back yoke 21 arranged around the detection section 12 of the coil unit 6 .

[0064] The back yoke 21 has the function of preventing the magnetic flux generated by the detection coils 11a to 11d from leaking to the outside. The back yoke 21 is integrally formed from a magnetic material. The back yoke 21 can be formed from, for example, a powder magnetic core obtained by applying an insulating coating to soft magnetic metal powder and then compression molding it, or a ferromagnetic material such as SUS (stainless steel), although the back yoke 21 is not limited to this.

[0065] The shape of the back yoke 21 is not limited as long as it can be arranged around the detection section 12 of the coil unit 6, and it can be configured, for example, as a cylindrical or parted cylindrical shape. In this example, the back yoke 21 is configured as a cylindrical shape. The back yoke 21 is held by the holder 5 in a state where it is arranged around the detection section 12 of the coil unit 6 and coaxially with the detection section 12. In this example, the other axial end of the back yoke 21 is externally fitted and fixed to the second outward flange portion 10, thereby holding the back yoke 21 relative to the holder 5.

[0066] The inner peripheral surface of the back yoke 21 and the outer peripheral surface of the detection unit 12 of the coil unit 6 can be arranged to be spaced apart in the radial direction, or they can be arranged in close contact with each other without being spaced apart in the radial direction. In this example, the outer peripheral surface of the detection unit 12 and the inner peripheral surface of the back yoke 21 are arranged to be spaced apart in the radial direction. Note that when the inner peripheral surface of the back yoke 21 and the outer peripheral surface of the detection unit 12 are arranged to be spaced apart in the radial direction, a non-magnetic material such as synthetic resin can be interposed between the inner peripheral surface of the back yoke 21 and the outer peripheral surface of the detection unit 12.

[0067] The magnetostrictive torque sensor 3 of this example includes, as an optional component, grease for lubricating the gap between the inner circumferential surface 7 of the holder 5 and the portion to be detected 4 of the rotating shaft 2 .

[0068] This reduces the frictional resistance between the inner circumferential surface 7 of the holder 5 and the detection target 4, thereby suppressing the frictional heat and wear that occurs between them. In this example, the detection target 4 has many fine recesses formed by shot peening, and these recesses can function as grease retaining portions, so that the lubrication state between the inner circumferential surface 7 of the holder 5 and the detection target 4 can be maintained well for a long period of time.

[0069] In the magnetostrictive torque measurement device 1 of this example, the inner circumferential surface 7 of the holder 5 is fitted onto the detection target 4 with a clearance fit that eliminates radial play. That is, the radial gap between the inner circumferential surface 7 of the holder 5 and the detection target 4 is set to be significantly smaller than the radial gap in conventional structures. This allows the radial distance between the detection unit 12 of the coil unit 6 and the detection target 4 to be set smaller than in conventional structures. Therefore, the magnetostrictive torque measurement device 1 of this example can minimize leakage magnetic flux that does not pass through the detection target 4, making it easier to ensure torque measurement accuracy, torque measurement sensitivity, or both. Therefore, the magnetostrictive torque measurement device 1 of this example can be suitably applied to various machines equipped with a rotating shaft 2 that require torque measurement, particularly to electrically assisted bicycles, including e-bikes.

[0070] REFERENCE SIGNS LIST 1 Magnetostrictive torque measuring device 2 Rotating shaft 3 Magnetostrictive torque sensor 4 Detected portion 5 Holder 6 Coil unit 7 Inner peripheral surface 8 Bobbin portion 9 First outward flange portion 10 Second outward flange portion 11 Detector coil 11a First detector coil 11b Second detector coil 11c Third detector coil 11d Fourth detector coil 12 Detector portion 13 Flexible substrate 14a to 14d Coil pieces 15a to 15d Coil pieces 16 External device 17 Oscillator 18 Voltmeter 19a First signal line 19b Second signal line 19c Third signal line 19d Fourth signal line 20 Signal line portion 21 Back yoke

Claims

1. A magnetostrictive torque measuring device comprising: a rotating shaft having a detectable portion with magnetostrictive properties on a portion of its outer peripheral surface in the axial direction; a magnetostrictive torque sensor; the magnetostrictive torque sensor being made of synthetic resin and having an inner peripheral surface that is fitted onto the detectable portion with a clearance fit that leaves no radial play; a holder that does not rotate during use; and a coil unit held by the holder, the coil unit having a detector that includes multiple detector coils.

2. A magnetostrictive torque measuring device according to claim 1, wherein the radial dimension of the gap between the inner peripheral surface of the holder and the part to be detected is 0.05 mm or more and 0.2 mm or less.

3. The maximum rotation speed of the rotating shaft is 300 min. -1 3. The magnetostrictive torque measuring device according to claim 1, wherein:

4. A magnetostrictive torque measuring device according to any one of claims 1 to 3, further comprising grease for lubricating the space between the inner circumferential surface of the holder and the part to be detected.

5. A magnetostrictive torque measuring device according to any one of claims 1 to 4, wherein the detected part is formed by a shot peening treatment.

Images