Method for acquiring correction value for torque sensor and method for measuring torque of rotary shaft

Abstract

[Problem] To shorten the time required for a test for acquiring a correction value while ensuring accuracy of torque measurement. [Solution] An output value Es1 (temporary correction value Cts1) at a first reference temperature ts1 and an output value Es2 (temporary correction value Cts2) at a second reference temperature are actually measured for a torque sensor for which a correction value is to be acquired, and a temporary correction function f which is a linear function indicating a relationship between the temperature t and a temporary correction value Ct is obtained. At least one non-reference temperature tn other than the first reference temperature and the second reference temperature is substituted into the temporary correction function f to obtain a temporary correction value Ctn for at least one non-reference temperature tn. A correction value Cn for least at one non-reference temperature tn is obtained by correcting the temporary correction value Ctn for least at one non-reference temperature tn by a correction amount ∆Cn for at least one non-reference temperature tn obtained in advance.

Description

Method for obtaining correction values ​​for torque sensors and method for measuring torque on rotating shafts

[0001] The present disclosure relates to a method for acquiring a correction value for a torque sensor disposed around a detection target portion of a rotating shaft, and a method for measuring torque of the rotating shaft.

[0002] A known device for measuring torque applied to a rotating shaft is a magnetostrictive torque measuring device that measures the torque applied to a rotating shaft by utilizing the inverse magnetostrictive effect that occurs in the rotating shaft when torque is applied to the rotating shaft. The magnetostrictive torque measuring device is configured to measure the torque applied to the rotating shaft by detecting a change in the magnetic permeability of the rotating shaft when torque is applied as a change in inductance of a detection coil.

[0003] Generally, the change in magnetic permeability of the part to be detected due to torque fluctuations is minute, so measures are usually taken to improve measurement sensitivity. One such measure is a conventional method using a bridge circuit 100 as shown in Fig. 8. In this method, four detector coils, namely a first detector coil 103, a second detector coil 104, a third detector coil 105, and a fourth detector coil 106, are arranged around a cylindrical detector part 102, which is a portion of a rotating shaft 101 in the axial direction, as shown in Fig. 9, and the four detector coils are arranged on the four sides of the bridge circuit 100.

[0004] When torque T is applied to the rotating shaft 101, stresses σ with opposite signs (+σ) act on the outer circumferential surface of the detection target 102 in two directions: one tilted at a predetermined angle (for example, +45 degrees) relative to the axial direction and the other tilted at a predetermined angle (for example, -45 degrees) in the opposite direction relative to the axial direction. Due to the inverse magnetostriction 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.

[0005] In bridge circuit 100, first detection coil 103 and third detection coil 105, located on one pair of opposite sides constituting the four sides, are detection coils for detecting changes in magnetic permeability on the outer surface of detection target 102 in a direction inclined at a predetermined angle relative to the axial direction. Second detection coil 104 and fourth detection coil 106, located on the other pair of opposite sides, are detection coils for detecting changes in magnetic permeability on the outer surface of detection target 102 in a direction inclined at a predetermined angle relative to the axial direction in the opposite direction. In bridge circuit 100, when an AC voltage (input voltage) Vi is applied between two end points, points A and C, an output value (output voltage) Vo corresponding to the direction and magnitude of torque T applied to rotating shaft 101 is obtained as a voltage between two midpoints, points B and D. Therefore, torque T can be calculated based on this output value Vo.

[0006] By using the bridge circuit 100 as described above, the output value Vo can be doubled compared to when detecting only the change in magnetic permeability in either one of a direction inclined at a predetermined angle in a predetermined direction relative to the axial direction and a direction inclined at a predetermined angle in the opposite direction relative to the axial direction, thereby improving the measurement sensitivity of the torque T.

[0007] It is preferable that the four detection coils 103 to 106 that make up the bridge circuit 100 all have the same impedance. However, in reality, variations occur in the impedance of the detection coils 103 to 106 due to manufacturing errors and the like. Due to the influence of such impedance variations, an offset voltage is inevitably output even when no torque T is being applied to the rotating shaft 101.

[0008] It is also known that the impedance of the four detection coils 103 to 106 changes with temperature. Therefore, the offset voltage also changes with temperature. As a result, the relationship between the torque T applied to the rotating shaft 101 and the output voltage Vo is also affected by temperature changes.

[0009] Japanese Patent Application Laid-Open Publication No. 2018-048956 describes a magnetostrictive torque measuring device (torque sensor) that can accurately detect torque regardless of temperature changes.

[0010] In a conventional torque measuring device described in JP 2018-048956 A, an output value (sine and cosine components of the output voltage) at a preset reference temperature is stored, and a relationship between the amount of change in the output value relative to a temperature change from the reference temperature (amount of change in the sine component and amount of change in the cosine component) is also stored when no torque is being applied to the rotating shaft. When calculating the torque applied to the rotating shaft, the amount of change in the output value corresponding to the temperature detected by the temperature detection means at that time is calculated from the relationship, the output value output from the torque sensor (sensor unit) at that time is corrected by the amount of change, and the torque is calculated based on the corrected output value.

[0011] In the conventional torque measurement device described in JP 2018-048956 A, in order to determine the relationship between the amount of change in output value and the temperature change from a reference temperature when no torque is applied to the rotating shaft, it is necessary to conduct tests to acquire output values ​​at multiple temperatures for each torque sensor. Specifically, output values ​​are acquired at regular temperature intervals (for example, 10°C) within the temperature range in which the torque sensor is normally used (for example, a range of approximately -40°C to 120°C).

[0012] More specifically, the torque sensor is placed in a test chamber, the temperature (room temperature) of the test chamber is set to a predetermined temperature, and the torque sensor is left for a certain period of time until the temperature of the torque sensor reaches the predetermined temperature, and then the output value at that temperature is obtained. This procedure is repeated while changing the temperature of the test chamber by a certain amount within the temperature range in which the torque sensor is normally used.

[0013] Such testing requires a considerable amount of time and effort, which may result in problems such as reduced productivity of torque sensors and increased manufacturing costs.

[0014] Japanese Patent Application Laid-Open No. 2023-127315 describes a manufacturing method that can reduce the manufacturing time of a torque measuring device having a function of correcting the influence of temperature.

[0015] In the manufacturing method described in JP 2023-127315 A, first, for a plurality of test samples, a coil balance C is calculated, which is the ratio (R1×R3) / (R2×R4) of the product R1×R3 of the resistance values ​​R1 and R3 of two opposing sides that make up one pair of opposing sides of the four sides of the bridge circuit to the product R2×R4 of the resistance values ​​R2 and R4 of two opposing sides that make up the other pair of opposing sides of the four sides. ｂ , and the temperature change rate V of the output value (output voltage) Vo due to temperature fluctuations of the torque sensor (sensor section) Ｔ From the results of the test, the coil balance C ｂ and the temperature change rate V Ｔ Next, for the torque sensor to be manufactured, the resistance values ​​R1, R2, R3, and R4 of the four sides of the bridge circuit are measured to obtain the coil balance C ｂ and calculate the coil balance C ｂ Using the above relationship X, the temperature change rate V of the torque sensor to be manufactured is calculated. Ｔ Ask for.

[0016] According to the conventional manufacturing method described in JP 2023-127315 A, there is no need to conduct tests to obtain output values ​​at multiple temperatures for each individual torque sensor to be manufactured, which significantly reduces manufacturing time.

[0017] JP 2018-048956 A JP 2023-127315 A

[0018] In the conventional manufacturing method described in JP 2023-127315 A, no tests are conducted to obtain actual output values ​​for each individual torque measuring device to be manufactured, which may make it difficult to ensure torque measurement accuracy.

[0019] The present disclosure aims to provide a method for obtaining a correction value for a torque sensor that can shorten the time required for testing to obtain the correction value while ensuring torque measurement accuracy.

[0020] The torque sensor that is the target of the torque sensor correction value acquisition method according to one aspect of the present disclosure is arranged around the detection target portion of the rotating shaft.

[0021] A torque sensor correction value acquisition method according to one aspect of the present disclosure includes the steps of: actually measuring an output value at a first reference temperature and an output value at a second reference temperature for the torque sensor from which a correction value is to be acquired; determining a provisional correction function, which is a linear function that indicates a relationship between the temperature and the provisional correction value for the torque sensor from which a correction value is to be acquired, by setting the output value at the first reference temperature as a provisional correction value for the first reference temperature and the output value at the second reference temperature as a provisional correction value for the second reference temperature; substituting at least one non-reference temperature other than the first reference temperature and the second reference temperature into the provisional correction function to obtain a provisional correction value for the at least one non-reference temperature; and correcting the provisional correction value at the at least one non-reference temperature with a correction amount for the at least one non-reference temperature that has been determined in advance, to obtain a correction value for the at least one non-reference temperature.

[0022] In one aspect of the method for acquiring a correction value for a torque sensor according to the present disclosure, the correction amount at the at least one non-reference temperature is calculated by: actually measuring output values ​​at the first reference temperature, the second reference temperature, and the at least one non-reference temperature for at least one test sample having the same configuration as the torque sensor for which the correction value is to be acquired; determining a reference function, which is a linear function that shows the relationship between the temperature and the provisional output value for the at least one test sample, using the output value at the first reference temperature as a provisional output value and the output value at the second reference temperature as a provisional output value; and substituting the at least one non-reference temperature into the reference function, based on the difference between the provisional output value at the at least one non-reference temperature and the actually measured output value at the at least one non-reference temperature.

[0023] In the torque sensor correction value acquisition method according to one aspect of the present disclosure, the absolute value of the difference between the first reference temperature and the second reference temperature is 10° C. or more and 190° C. or less. The absolute value of the difference between the first reference temperature and the second reference temperature is preferably 60° C. or more and 130° C. or less.

[0024] A torque measurement method for a rotating shaft according to one aspect of the present disclosure corrects the output value of a torque sensor arranged around a detected portion of the rotating shaft with a correction value determined in advance in accordance with the temperature of the torque sensor, and calculates the torque applied to the rotating shaft based on the corrected output value of the torque sensor.

[0025] In particular, in the torque measurement method for a rotating shaft according to one aspect of the present disclosure, the correction value is acquired by the torque sensor correction value acquisition method according to one aspect of the present disclosure.

[0026] According to the torque sensor correction value acquisition method of one aspect of the present disclosure, it is possible to ensure torque measurement accuracy while shortening the time required for testing to acquire the correction value.

[0027] FIG. 1 is a perspective view schematically illustrating an example of a torque sensor that is a target of a torque sensor correction value acquisition method according to an embodiment of the present disclosure. FIG. 2 is a schematic cross-sectional view of the torque sensor taken along an imaginary plane including the central axis. FIG. 3 is a view of a first, second, third, and fourth detector coils constituting the torque sensor, viewed from the radially outer side. FIG. 4(a) is a development view of the first detector coil alone, viewed from the radially outer side. FIG. 4(b) is a development view of the second detector coil alone, viewed from the radially outer side. FIG. 4(c) is a development view of the third detector coil alone, viewed from the radially outer side. FIG. 4(d) is a development view of the fourth detector coil alone, viewed from the radially outer side. FIG. 5 is a schematic view of a torque measurement device including the torque sensor. Fig. 6(A) is a diagram showing the results of measuring the relationship between temperature and output value for a test sample, and Fig. 6(B) is a diagram showing the correction amount at each temperature. Fig. 7(A) is a diagram showing the results of measuring the output value at a first reference temperature and the output value at a second reference temperature for a torque sensor from which a correction value is to be obtained, and Fig. 7(B) is a diagram explaining a method for calculating a correction value at a non-reference temperature from the relationship shown in Fig. 7(A). Fig. 8 is a diagram showing a bridge circuit of a conventional torque measuring device. Fig. 9 is a perspective view of a rotating shaft to explain the direction of stress generated when torque is applied to the rotating shaft.

[0028] An example of an embodiment of the present disclosure will be described with reference to FIGS. 1 to 7B.

[0029] The torque sensor correction value acquisition method and rotating shaft torque measurement method of this embodiment can be widely applied to magnetostrictive torque measurement devices (torque sensors) that are affected by temperature changes. Below, we will explain the structure of a torque measurement device 1 that includes a torque sensor 4 to which the torque sensor correction value acquisition method of this embodiment can be suitably applied, then we will explain the correction value acquisition method for the torque sensor 4, and finally we will explain a method for detecting torque T applied to a rotating shaft 2 using the torque measurement device 1.

[0030] <Structure of Torque Measuring Device> The torque measuring device 1 determines the magnitude and direction (CW or CCW) of the torque T transmitted by the rotating shaft 2 by utilizing the inverse magnetostriction effect that occurs in the rotating shaft 2. The torque measuring device 1 has a function of correcting the output value Vo of the torque sensor 4 arranged around the detection target 3 of the rotating shaft 2 by a correction value C that corresponds to the temperature of the torque sensor 4.

[0031] In the following description, unless otherwise specified, the axial, radial, and circumferential directions of the torque measuring 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 and also coincide with the axial, radial, and circumferential directions of the magnetic ring 6. Furthermore, one axial side refers to the left side in Fig. 2, and the other axial side refers to the right side in Fig. 2.

[0032] The rotating shaft 2 has a detection target portion 3 on a part of the outer circumferential surface in the axial direction.

[0033] The magnetic permeability of the detection target 3 changes in response to the torque T applied to the rotating shaft 2. In other words, the detection target 3 exhibits an inverse magnetostriction effect as the torque T is applied to the rotating shaft 2.

[0034] The configuration of the detected part 3 is not particularly limited as long as the magnetic permeability changes as torque T is applied to the rotating shaft 2 and the change in magnetic permeability can be detected by the torque sensor 4. In other words, the detected part 3 can have a configuration corresponding to the configuration of the torque sensor 4.

[0035] In this example, all four detection coils 10a to 10d constituting the torque sensor 4 are stacked in the radial direction. Therefore, the detected part 3 is configured with a cylindrical surface whose outer diameter does not change in the axial direction. In this case, a modified layer whose magnetostrictive properties are improved by shot peening may be provided on the surface layer of the rotating shaft 2 including the detected part 3.

[0036] Furthermore, a part or all of the rotating shaft 2, including at least the detected portion 3, is made of a material having magnetostrictive properties. The material having magnetostrictive properties can be either a material having a positive magnetostrictive constant or a material having a negative magnetostrictive constant. Specifically, a part or all of the rotating shaft 2 can be made of a steel material such as, but not limited to, SC (carbon steel for machine construction), SUS (stainless steel), SCr (chromium steel), SCM (chromium molybdenum steel), or SNCM (nickel chromium molybdenum steel). Alternatively, a part or all of the rotating shaft 2, including the detected portion 3, can be covered with a magnetostrictive film such as a nickel alloy.

[0037] Alternatively, when the torque sensor 4 has two detection coils arranged side by side in the axial direction, the detected portion can be composed of a first magnetic change portion constituted by alternately arranging first magnetic portions having magnetic anisotropy and first non-magnetic portions having no magnetic anisotropy in the circumferential direction, each formed so as to extend in a direction inclined at a predetermined angle (for example, +45 degrees) relative to the axial direction, and a second magnetic change portion constituted by alternately arranging second magnetic portions having magnetic anisotropy and second non-magnetic portions having no magnetic anisotropy in the circumferential direction, each formed so as to extend in a direction inclined at a predetermined angle (for example, -45 degrees) relative to the axial direction in the opposite direction to the predetermined direction.

[0038] The rotating shaft 2 is rotatably supported via a bearing (not shown) on a fixed portion that does not rotate even during use.

[0039] The torque measuring device 1 includes a torque sensor 4 arranged around a detection target portion 3 of a rotating shaft 2. The basic configuration of the torque measuring device 1 including the torque sensor 4 is not particularly limited as long as it can detect a change in the magnetic permeability of the detection target portion 3 that accompanies the application of torque T to the rotating shaft 2.

[0040] For example, the torque measuring device 1 can have the same basic configuration as the torque measuring device (torque sensor) described in Japanese Patent Application Laid-Open No. 2018-48956 or the basic configuration of the torque measuring device described in Japanese Patent Application Laid-Open No. 2023-127315.

[0041] In this example, the torque sensor 4 includes a holder 5 and a magnetic ring 6 in addition to the plurality of detection coils 10a to 10d.

[0042] The holder 5 has a bobbin portion 7 that is arranged around the detection target portion 3 of the rotary shaft 2 .

[0043] In this example, the bobbin portion 7 is cylindrical. That is, the bobbin portion 7 has a cylindrical inner peripheral surface whose inner diameter does not change in the axial direction and a cylindrical outer peripheral surface whose outer diameter does not change in the axial direction. However, the bobbin portion may also be configured as a notched cylinder.

[0044] The holder 5 is supported and fixed to a fixed portion that does not rotate during use, such as a housing, with the bobbin portion 7 disposed coaxially around the detection target portion 3 of the rotating shaft 2. With the holder 5 supported and fixed to the fixed portion, the inner peripheral surface of the bobbin portion 7 faces the detection target portion 3 with a radial gap therebetween.

[0045] The holder 5 is made of synthetic resin, which is a non-magnetic and non-conductive (insulating) material. Specifically, the holder 5 is made of a thermoplastic resin such as epoxy resin, polyphenylene sulfide (PPS), PA (polyamide), or PPA (polyphthalamide). In this example, the holder 5 is integrally formed by injection molding of synthetic resin. However, the holder can also be formed by combining multiple parts.

[0046] In this example, the holder 5 has, as optional elements, a first outward flange portion 8 extending radially outward from the end on one axial side of the bobbin portion 7 around the entire circumference, and a second outward flange portion 9 extending radially outward from the end on the other axial side of the bobbin portion 7 around the entire circumference.

[0047] The first outward flange portion 8 has an attachment portion for supporting and fixing the holder 5 to the fixed portion, a cable for electrically connecting the detection coils 10a to 10d to an external device, or a wiring accommodating portion for accommodating signal lines.

[0048] In this example, the outer diameter of the first outward flange portion 8 is larger than the outer diameter of the second outward flange portion 9. However, the outer diameter of the first outward flange portion 8 can be the same as the outer diameter of the second outward flange portion 9, or can be smaller than the outer diameter of the second outward flange portion 9.

[0049] The torque sensor 4 has a plurality of detection coils 10 arranged around the bobbin portion 7 .

[0050] The number, configuration, and arrangement of the multiple detection coils 10 are not particularly limited as long as they can detect changes in the magnetic permeability of the rotating shaft 2. For example, the multiple detection coils 10 can be arranged overlapping each other in the radial direction, arranged side by side in the axial direction, or arranged overlapping each other in the radial direction and side by side in the axial direction.

[0051] In this example, the multiple detector coils 10 are configured by four detector coils 10a to 10d arranged to overlap in the radial direction. Specifically, the four detector coils 10a to 10d are arranged to overlap in the order of the first detector coil 10a, the second detector coil 10b, the third detector coil 10c, and the fourth detector coil 10d from the inside in the radial direction.

[0052] Alternatively, the plurality of detection coils 10 may be configured from two detection coils arranged side by side in the axial direction.

[0053] In this example, the four detection coils 10a to 10d are formed on four wiring layers that make up the flexible substrate 11. The flexible substrate 11 has a laminated structure with four wiring layers. Each wiring layer is made up of a wiring pattern formed by etching a conductor such as copper foil. That is, in this example, each of the detection coils 10a to 10d is made up of a wiring pattern.

[0054] Alternatively, each detection coil 10 can be constructed by winding an insulated wire along a groove formed on the outer circumferential surface of the bobbin portion of the holder.

[0055] Of the four detection coils 10a to 10d, the first detection coil 10a and the third detection coil 10c detect a change in magnetic permeability in a direction inclined at a predetermined angle (for example, +45 degrees) in a predetermined direction with respect to the axial direction in the detection target 3. In other words, the first detection coil 10a and the third detection coil 10c change their own inductance in accordance with a change in magnetic permeability in a direction inclined at a predetermined angle in a predetermined direction with respect to the axial direction.

[0056] Of the four detection coils 10a to 10d, the second detection coil 10b and the fourth detection coil 10d detect a change in magnetic permeability in a direction inclined at a predetermined angle (for example, −45 degrees) in a direction opposite to the predetermined direction with respect to the axial direction in the detection target 3. In other words, the second detection coil 10b and the fourth detection coil 10d change their own inductance in accordance with a change in magnetic permeability in a direction inclined at a predetermined angle in a direction opposite to the predetermined direction with respect to the axial direction.

[0057] As shown schematically in Figures 4(a) to 4(d), each of the detection coils 10a to 10d is configured by arranging a plurality of coil pieces 12a to 12d, each of which has a wiring pattern arranged in the shape of a parallelogram when viewed from the radial direction, at equal intervals in the circumferential direction.

[0058] The coil pieces 12a constituting the first detector coil 10a and the coil pieces 12c constituting the third detector coil 10c have straight portions inclined at a predetermined angle in a direction opposite to a predetermined direction with respect to the axial direction. The coil pieces 12b constituting the second detector coil 10b and the coil pieces 12d constituting the fourth detector coil 10d have straight portions inclined at a predetermined angle in a predetermined direction with respect to the axial direction.

[0059] 4(a) to 4(d), the coil pieces 12a to 12d are shown schematically. In reality, the wiring patterns constituting the coil pieces 12a to 12d have discontinuous portions, and the coil pieces 12a to 12d have two ends sandwiching the discontinuous portion. Circumferentially adjacent coil pieces 12a to 12d are connected in series by connecting one end of each other via a conductor such as a wiring pattern (not shown).

[0060] 5, the four detection coils 10a to 10d are connected in a circular shape to form a bridge circuit 13. The four detection coils 10a to 10d are connected in a circular shape.

[0061] The magnetic ring 6 is also called a back yoke and has the function of preventing the magnetic flux generated by the detection coil 10 from leaking to the outside. The magnetic ring 6 is made of a magnetic material and is integrally formed as a whole. The magnetic material that can be used to form the magnetic ring 6 is, for example, an iron-based alloy such as an alloy steel for mechanical structures or stainless steel.

[0062] The magnetic ring 6 has a cylindrical shape. The magnetic ring 6 is disposed around the detection coil 10 coaxially with the detection coil 10, and is fixedly coupled to the holder 5. In this example, the other axial end of the magnetic ring 6 is externally fitted and fixed to the second outward flange portion 9, thereby fixing the magnetic ring 6 to the holder 5.

[0063] The torque measuring device 1 further includes an oscillator 14, a voltmeter 15, a temperature measuring unit 16, and a torque calculating unit 17. In this example, the oscillator 14, the voltmeter 15, the temperature measuring unit 16, and the torque calculating unit 17 are provided in the torque measuring device 1 as external devices of the torque sensor 4. Alternatively, some or all of the oscillator 14, the voltmeter 15, the temperature measuring unit 16, and the torque calculating unit 17 may be provided inside or around the torque sensor 4.

[0064] In this example, the oscillator 14 applies an AC voltage (input voltage) Vi between a contact A between the first detection coil 10a and the second detection coil 10b and a contact C between the third detection coil 10c and the fourth detection coil 10d.

[0065] The voltmeter 15 detects an output value (output voltage) Vo between a junction B between the second detection coil 10b and the third detection coil 10c and a junction D between the first detection coil 10a and the fourth detection coil 10d.

[0066] The temperature measurement unit 16 has a function of measuring the temperature of the torque sensor 4, more specifically, the temperature of the detection coils 10 (10a to 10d). The temperature measurement unit 16 can be configured to measure the temperature t of the torque sensor 4 based on the AC voltage Vi applied to the bridge circuit 13, or can be configured as a contact thermometer such as a thermocouple or a non-contact thermometer such as a radiation thermometer.

[0067] In this example, the temperature measurement unit 16 is configured to measure the temperature t of the torque sensor 4 based on the AC voltage Vi applied to the bridge circuit 13 .

[0068] The AC voltage Vi applied to the bridge circuit 13 is divided by the internal impedance of the oscillator 14 and the impedance between the contacts A and C. Therefore, when the impedance of the detection coils 10 (10a to 10d) changes in accordance with a change in the temperature of the torque sensor 4, the AC voltage Vi applied to the bridge circuit 13 also changes. Based on the AC voltage Vi applied to the bridge circuit 13, the temperature measurement unit 16 calculates the temperature of the torque sensor 4 at an arbitrarily set reference temperature t ０ The temperature change amount Δt is calculated from the temperature change amount Δt.

[0069] For this purpose, the temperature measurement unit 16 measures the reference temperature t ０ The magnitude of the AC voltage at Vi ０ The temperature measurement unit 16 measures the temperature change Δt and the AC voltage change ΔVi input through a lock-in amplifier or the like, and stores the temperature change Δt and the AC voltage change ΔVi in advance. ０ The magnitude of the AC voltage at Vi ０ The change amount ΔVi from the reference temperature t is calculated based on the change amount ΔVi and the above relationship. ０ The amount of change (temperature change) Δt from the reference temperature t ０ By adding the change amount Δt to the temperature of the torque sensor 4, the current temperature t (= t ０ +Δt) can be obtained.

[0070] When the lock-in amplifier outputs the sine and cosine components of the AC voltage, the temperature change can be calculated based on the magnitude of the AC voltage calculated by taking the root mean square of the sine and cosine components. However, the temperature change can also be calculated based on only the sine or cosine component of the AC voltage.

[0071] In this example, the temperature t of the torque sensor 4 is measured based on the AC voltage Vi applied to the bridge circuit 13, so there is no need to provide a temperature sensor just to determine the temperature t of the torque sensor 4, which makes it easier to reduce the manufacturing cost and size of the torque measuring device 1.

[0072] The torque calculation unit 17 calculates the torque T applied to the rotating shaft 2. The torque calculation unit 17 has a correction function that corrects the output value Vo of the torque sensor 4 with a correction value C that corresponds to the temperature of the torque sensor 4, and a calculation function that calculates the torque T applied to the rotating shaft 2 based on the output value Vc of the torque sensor 4 after the correction.

[0073] In this example, the correction function corrects the output value Vo of the torque sensor 4 detected by the voltmeter 15 with a correction value C determined in advance in accordance with the temperature t of the torque sensor 4 measured by the temperature measurement unit 16. A method for determining the correction value C at the temperature t in advance will be described later.

[0074] In this example, the calculation function determines the magnitude T and direction (CW or CCW) of the torque applied to the rotating shaft 2 based on the output value Vc of the torque sensor 4 corrected by the correction function, and the relationship between the output value V, which has been determined in advance by calculation, experiment, etc., and the magnitude T and direction (CW or CCW) of the torque applied to the rotating shaft 2.

[0075] The temperature measurement unit 16 and the torque calculation unit 17 can be implemented on, for example, a single microcomputer (MCU). However, the temperature measurement unit 16 and the torque calculation unit 17 may also be implemented on different microcomputers.

[0076] <Method for Obtaining Torque Sensor Correction Value> A correction value obtaining method for obtaining the correction value C used to correct the output value Vo of the torque sensor 4 will be described with reference to FIGS. 6(A) to 7(B).

[0077] In the correction value acquisition method for the torque sensor 4 of this example, in order to obtain a correction value C for correcting the output value Vo of the torque sensor 4 from which the correction value is to be acquired, first, a first reference temperature t ｓ１ Output value Vo at ｓ１ , and the second reference temperature t ｓ２ Output value Vo at ｓ２ A process of actually measuring the above is carried out.

[0078] Output value Vo ｓ１ , and Vo ｓ２ The measurement is performed before the torque sensor 4 is placed around the rotating shaft 2, or after the torque sensor 4 is placed around the rotating shaft 2 but no torque is being applied to the rotating shaft 2.

[0079] First reference temperature t ｓ１ and the second reference temperature t ｓ２ are two different temperatures appropriately selected from the temperature range in which the torque sensor 4 is normally used. ｓ１ and second reference temperature t ｓ２ Absolute value of the difference between |t ｓ１ -t ｓ２ is set appropriately depending on the application or the environment in which the torque sensor 4 is used. ｓ１ and second reference temperature t ｓ２ Absolute value of the difference between |t ｓ１ -t ｓ２ Although not limited thereto, | can be set to 10° C. or higher and 190° C. or lower, and preferably 60° C. or higher and 130° C. or lower. The temperature range in which the torque sensor 4 is normally used is, for example, a range of about −20° C. to 120° C., although not limited thereto. In this case, for example, the first reference temperature t ｓ１ is set to the temperature at which the torque sensor 4 starts to be used, for example, room temperature, and the second reference temperature t ｓ２can be set to any temperature in the high temperature range that the torque sensor 4 reaches during normal use. ｓ１ is set to 20°C, and the second reference temperature t ｓ２ is set to 80°C.

[0080] Specifically, the torque sensor 4 from which the correction value is to be obtained is connected to a test device having the same configuration as the external devices (oscillator 14, voltmeter 15, temperature measurement unit 16, and torque calculation unit 17) of the torque measurement device 1. The torque sensor 4 is placed in a test room, and the temperature (room temperature) in the test room is set to a first reference temperature t ｓ１ Then, when the temperature of the torque sensor 4 reaches the first reference temperature t ｓ１ After the predetermined time has elapsed, a predetermined AC voltage Vi is applied between contacts A and C by the oscillator 14, and the voltage between contacts B and D is measured by the voltmeter 15 as an output value Vo. ｓ１ Next, the room temperature is detected as a second reference temperature t ｓ２ and the temperature of the torque sensor 4 is set to the second reference temperature t ｓ２ After the predetermined time has elapsed, a predetermined AC voltage Vi is applied between contacts A and C by the oscillator 14, and the voltage between contacts B and D is measured by the voltmeter 15 as an output value Vo. ｓ２ However, the order of measurements is not particularly limited, and the second reference temperature t ｓ２ Output value Vo at ｓ２ After measuring the first reference temperature t ｓ１ Output value Vo at ｓ１ may be measured.

[0081] Next, the first reference temperature t ｓ１ Output value Vo at ｓ１ , the first reference temperature t ｓ１ Provisional correction value Ct ｓ１ and the second reference temperature t ｓ２ Output value Vo at ｓ２ , the second reference temperature t ｓ２ Provisional correction value Ct ｓ２ Then, a step of calculating a provisional correction function f, which is a linear function showing the relationship between the temperature t of the torque sensor 4 and the provisional correction value v, is performed.

[0082] The provisional correction function f is a linear function expressed as v=a×t+b (a and b are constants) as shown in FIG.

[0083] Next, the first reference temperature t ｓ１ and the second reference temperature t ｓ２ At least one non-reference temperature t other than ｎ into the provisional correction function f, and ｎ Provisional correction value Ct ｎ The process of obtaining the above is carried out.

[0084] At least one non-reference temperature t ｎ is the temperature range in which the torque sensor 4 is normally used, and the first reference temperature t ｓ１ and the second reference temperature t ｓ２ The non-reference temperature t ｎ The number of non-reference temperatures t can be set appropriately depending on the application or environment of the torque sensor 4, or the torque measurement accuracy required of the torque sensor 4. ｎ When the number of the first reference temperature t ｓ１ and second reference temperature t ｓ２ It can be set to an intermediate temperature between

[0085] Non-reference temperature t ｎ is the temperature range in which the torque sensor 4 is normally used, and the first reference temperature t ｓ１ and the second reference temperature t ｓ２ It is preferable to set multiple values ​​for each constant temperature except for the non-reference temperature t ｎ The more the number of non-reference temperatures t ｎ The number of non-reference temperatures t is preferably 3 or more, and more preferably 6 or more. ｎ When the number of the first reference temperature t is three, but is not limited to this, for example, ｓ１ Any temperature lower than (for example, the lowest temperature in the range of use) t ｎ１ , first reference temperature t ｓ１ and second reference temperature t ｓ２ The intermediate temperature t ｎ２ , and the second reference temperature t ｓ２Any temperature higher than (for example, the highest temperature in the operating range) t ｎ３ can be set to.

[0086] Non-reference temperature t ｎ There is no upper limit to the number of non-reference temperatures t ｎ The number is preferably 10 or less, and more preferably 8 or less.

[0087] In this example, at least one non-reference temperature t ｎ from the range of −20° C. to 120° C. to the first reference temperature t ｓ１ 20°C, and the second reference temperature t ｓ２ A total of six (t ｎ１ ~t ｎ６ ) is set.

[0088] Then, at least one non-reference temperature t ｎ Provisional correction value Ct ｎ is calculated based on at least one non-reference temperature t ｎ Correction amount ΔC in ｎ By correcting the temperature by at least one non-reference temperature t ｎ Correction value C in ｎ Specifically, a process of obtaining the provisional correction value Ct ｎ Correction amount ΔC ｎ By adding, the correction value C ｎ (= Ct ｎ +ΔC ｎ ) is obtained.

[0089] In this example, six non-reference temperatures t ｎ１ ~t ｎ６ Provisional correction value Ct ｎ１ ~Ct ｎ６ is calculated based on the six non-reference temperatures t ｎ１ ~t ｎ６ Correction amount ΔC in ｎ１ ~ΔC ｎ６ As shown in FIG. 7B, the six non-reference temperatures t ｎ１ ~t ｎ６ Correction value C in ｎ１ ~C ｎ６[C ｎ１ (= Ct ｎ１ +ΔC ｎ１ ) ~ C ｎ６ (= Ct ｎ６ +ΔC ｎ６ ) has been obtained.

[0090] First reference temperature t ｓ１ Correction value C in ｓ１ is the provisional correction value Ct ｓ１ That is, the first reference temperature t ｓ１ Output value Vo at ｓ１ In addition, the second reference temperature t ｓ２ Correction value C in ｓ２ is the provisional correction value Ct ｓ２ That is, the first reference temperature t ｓ２ Output value Vo at ｓ２ That is, the first reference temperature t ｓ１ Correction amount ΔC in ｓ１ and the second reference temperature t ｓ２ Correction amount ΔC in ｓ２ are all 0.

[0091] The correction value (C ｓ１ , C ｓ２ , C ｎ (C ｎ１ ~C ｎ６ )) are stored in the memory of a microcomputer having the torque calculation unit 17. When the torque calculation unit 17 is configured as an external device, the correction value Ct for each temperature t of the torque sensor 4 can be recorded on a recording medium 18 such as a two-dimensional code or an IC tag before the torque sensor 4 is shipped from a manufacturing factory, and the recording medium 18 can be attached to the surface of the torque sensor 4 (holder 5 or magnetic ring 6).

[0092] At least one non-reference temperature t ｎ Provisional correction value Ct ｎ At least one non-reference temperature t ｎ Correction amount ΔC in ｎ It is necessary to calculate the correction amount ΔC in advance.ｎ The means for determining the above in advance is arbitrary, but is usually carried out by conducting a preparatory test as advance preparation. The means for the preparatory test are also arbitrary, but for example, the preparatory test can be carried out as follows.

[0093] <Preparatory Test> As a preliminary test, a preparatory test is performed using at least one test sample having the same configuration as the torque sensor 4 from which the correction value is to be obtained. The number of test samples is not limited to this, but can be 1 to 10.

[0094] In the preliminary test, first, the test sample is heated to a first reference temperature t ｓ１ , second reference temperature t ｓ２ , and at least one non-reference temperature t ｎ The output value E of the torque sensor 4 at ｓ１ , E ｓ２ , E ｎ In this example, the first reference temperature t ｓ１ , second reference temperature t ｓ２ , and six non-reference temperatures t ｎ１ ~t ｎ６ The output value E of the torque sensor 4 at ｓ１ , E ｓ２ , E ｎ１ ~E ｎ６ We have actually measured the following.

[0095] Output value E ｓ１ , E ｓ２ , E ｎ１ ~E ｎ６ The measurement is performed when the torque sensor 4 of the test sample is not placed around the rotating shaft 2, or when the torque sensor 4 of the test sample is placed around the rotating shaft 2 but no torque T is applied to the rotating shaft 2.

[0096] First reference temperature t in the preliminary test ｓ１ , second reference temperature t ｓ２ , and at least one non-reference temperature t ｎ is set in the same manner in accordance with the method for obtaining the correction value of the torque sensor. ｎ１ ~t ｎ６is a temperature range of −20° C. to 120° C., and is set to the first reference temperature t ｓ１ 20°C, and the second reference temperature t ｓ２ A total of six temperatures are set every 20°C, excluding 80°C.

[0097] Output value E ｓ１ , E ｓ２ , E ｎ (E ｎ１ ~E ｎ６ ), the torque sensor 4 of the test sample is connected to a test device having the same configuration as the external devices (oscillator 14, voltmeter 15, temperature measurement unit 16, and torque calculation unit 17) of the torque measurement device 1. The torque sensor 4 of the test sample is placed in a test chamber, and the temperature (room temperature) in the test chamber is set to a predetermined test temperature (first reference temperature t ｓ１ , second reference temperature t ｓ２ , or non-reference temperature t ｎ (t ｎ１ ~t ｎ６ After the predetermined time has elapsed, a predetermined AC voltage Vi is applied between contacts A and C by the oscillator 14, and the voltage between contacts B and D is measured by the voltmeter 15 as an output value E ｓ１ , E ｓ２ , E ｎ (E ｎ１ ~E ｎ６ By repeating this procedure while changing the temperature in the test room, the first reference temperature t ｓ１ , second reference temperature t ｓ２ , at least one non-reference temperature t ｎ (t ｎ１ ~t ｎ６ ) the output value E of the torque sensor 4 ｓ１ , E ｓ２ , E ｎ (E ｎ１ ~E ｎ６ ) is measured.

[0098] In the preliminary test, the order of measurements is not particularly limited, and may be, for example, from low temperature to high temperature.

[0099] Next, the first reference temperature t ｓ１ Output value E atｓ１ The provisional output value Et ｓ１ and the second reference temperature t ｓ２ Output value E at ｓ２ The provisional output value Et ｓ２ As shown in FIG. 6A, a reference function f is a linear function that indicates the relationship between the temperature t and the provisional output value Et of the test sample. ０ : Et=a ０ ×t+b ０ (a ０ , b ０ is a constant).

[0100] Then, at least one non-reference temperature t ｎ is the basis function f ０ At least one non-reference temperature t ｎ Provisional output value Et ｎ and at least one actually measured non-reference temperature t ｎ Output value E at ｎ The difference ΔE ｎ (= Et ｎ -E ｎ ) is calculated. ｎ Based on at least one non-reference temperature t ｎ Correction amount ΔC in ｎ The first reference temperature t ｓ１ Correction amount ΔC in ｓ１ and the second reference temperature t ｓ２ Correction amount ΔC in ｓ２ are all 0.

[0101] In this example, as shown in FIG. 6B, six non-reference temperatures t ｎ１ ~t ｎ６ Provisional output value Et ｎ１ ~Et ｎ６ and the six measured non-reference temperatures t ｎ１ ~t ｎ６ Output value E at ｎ１ ~E ｎ６ The difference ΔE ｎ１ (= Et ｎ１ -E ｎ１ ) ~ ΔE ｎ６ (= Et ｎ６ -E ｎ６ ) and calculate the difference ΔE ｎ１ ~ΔEｎ６ Based on the six non-reference temperatures t ｎ１ ~t ｎ６ Correction amount ΔC in ｎ１ ~ΔC ｎ６ We are looking for...

[0102] When the at least one test sample is composed of one test sample, the difference ΔE obtained using the one test sample ｎ (ΔE ｎ１ ~ΔE ｎ６ ) is used as the correction amount ΔC ｎ (ΔC ｎ１ ~ΔC ｎ６ ) can be used as

[0103] When at least one test sample is composed of a plurality of test samples, the difference ΔE calculated for each test sample ｎ (ΔE ｎ１ ~ΔE ｎ６ ) is calculated by adding the correction amount ΔC ｎ (ΔC ｎ１ ~ΔC ｎ６ ) can be used as

[0104] The above preparatory test does not need to be performed individually for each torque sensor 4 from which a correction value is to be obtained, but only needs to be performed once. ｎ (t ｎ１ ~t ｎ６ ) Correction amount ΔC ｎ (ΔC ｎ１ ~ΔC ｎ６ ) can be commonly used for torque sensors 4 having the same configuration as the test sample.

[0105] <Method of calculating torque applied to rotating shaft> When calculating the torque T applied to the rotating shaft 2 using the torque measuring device 1 equipped with the torque sensor 4 of this example, the output value Vo of the torque sensor 4 arranged around the detection target portion 3 of the rotating shaft 2 is calculated in accordance with the temperature of the torque sensor 4 by multiplying the output value Vo by the correction value C (C ｓ１ , C ｓ２ , C ｎ (C ｎ１ ~C ｎ６)) and calculates the torque T of the rotating shaft 2 based on the corrected output value Vc.

[0106] Specifically, first, the output value Vo of the torque sensor 4 is detected by the voltmeter 15 , and the temperature t of the torque sensor 4 is measured by the temperature measuring unit 16 .

[0107] Next, the torque calculation unit 17 calculates the output value Vo by adding a correction value C (C ｓ１ , C ｓ２ , C ｎ (C ｎ１ ~C ｎ６ )) to obtain the corrected output value Vc (=Vo+C).

[0108] The temperature t of the torque sensor 4 is equal to or higher than the first reference temperature t ｓ１ , second reference temperature t ｓ２ , and at least one non-reference temperature t ｎ (In this example, six non-reference temperatures t ｎ１ ~t ｎ６ ), the first reference temperature t ｓ１ , second reference temperature t ｓ２ , and at least one non-reference temperature t ｎ (t ｎ１ ~t ｎ６ ), the output value Vo can be corrected using the correction value C at the closest temperature. ｓ１ , second reference temperature t ｓ２ , and at least one non-reference temperature t ｎ (t ｎ１ ~t ｎ６ ), the output value Vo may be corrected using an average or weighted average of two temperatures that are close to the temperature t of the torque sensor 4.

[0109] The temperature t of the torque sensor 4 is equal to or higher than the first reference temperature t ｓ１ , second reference temperature t ｓ２ , and at least one non-reference temperature t ｎ (t ｎ１ ~t ｎ６), the output value Vo can be corrected using the correction value C at the lowest temperature. Alternatively, the correction value C at the lowest temperature can be obtained by substituting the temperature t of the torque sensor 4 into the provisional correction function f and adding the correction amount ΔC at the lowest temperature to the provisional correction value Ct. Also, when the temperature t of the torque sensor 4 is lower than the first reference temperature t, ｓ１ , second reference temperature t ｓ２ , and at least one non-reference temperature t ｎ (t ｎ１ ~t ｎ６ ), the output value Vo can be corrected using the correction value C at the maximum temperature. Alternatively, the correction value C at the maximum temperature t can be obtained by substituting the temperature t of the torque sensor 4 into the provisional correction function f to obtain a provisional correction value Ct, and adding the correction amount ΔC at the maximum temperature to the provisional correction value Ct.

[0110] Then, based on the corrected output value Vc, the torque calculation unit 17 calculates the magnitude T and direction (CW or CCW) of the torque applied to the rotating shaft 2 from the relationship between the output value V, which has been calculated in advance by calculation, experiment, etc., and the magnitude T and direction (CW or CCW) of the torque applied to the rotating shaft 2.

[0111] The torque measuring device 1 of this example has a function of correcting the effect of the temperature t of the torque sensor 4 on the output value Vo, and therefore can ensure good measurement accuracy of the torque T applied to the rotating shaft 2 regardless of the temperature t.

[0112] In particular, in the method for obtaining a correction value for the torque sensor 4 of this example, in order to obtain the correction value C, the torque sensor 4 for which the correction value is to be obtained is set to a first reference temperature t ｓ１ and second reference temperature t ｓ２ Output value Vo at two temperatures ｓ１ , Vo ｓ２ Therefore, compared to the conventional manufacturing method described in JP 2023-127315 A, in which a test to actually obtain an output value is not performed for each individual torque sensor to be manufactured, it is easier to ensure good measurement accuracy of the torque T applied to the rotating shaft 2.

[0113] Furthermore, according to the method for acquiring the correction value of the torque sensor 4 of this embodiment, the first reference temperature t ｓ１ and second reference temperature t ｓ２ Output value Vo at two temperatures ｓ１ , Vo ｓ２ By acquiring the first reference temperature t ｓ１ and the second reference temperature t ｓ２ Correction value C in ｓ１ , C ｓ２ as well as at least one non-reference temperature t ｎ Correction value C in ｎ can be obtained. In other words, according to the correction value acquisition method for the torque sensor 4 of this example, it is not necessary to acquire output values ​​at a plurality of (three or more) temperatures for each individual torque sensor while changing the temperature by a fixed amount within the temperature range in which the torque sensor is normally used, as is the case with the conventional torque sensor described in JP 2018-48956 A. Therefore, according to the correction value acquisition method for the torque sensor 4 of this example, it is possible to shorten the time required for testing to acquire the correction value C.

[0114] If the voltmeter 15 detects the sine component and cosine component of the output voltage of the torque sensor 4 as the output value thereof, and the torque calculation unit 17 is configured to calculate the torque T applied to the rotating shaft 2 based on the sine component and the cosine component, then the correction value C can also be determined separately for the sine component and the cosine component. If the torque calculation unit 17 is configured to calculate the torque T applied to the rotating shaft 2 based on only the sine component or only the cosine component of the output voltage of the torque sensor 4 as the output value thereof, then the correction value C can also be determined for only the sine component or only the cosine component.

[0115] REFERENCE SIGNS LIST 1 Torque measuring device 2 Rotating shaft 3 Part to be detected 4 Torque sensor 5 Holder 6 Magnetic ring 7 Bobbin part 8 First outward flange part 9 Second outward flange part 10 Detection coil 10a First detection coil 10b Second detection coil 10c Third detection coil 10d Fourth detection coil 11 Flexible substrate 12a to 12d Coil pieces 13 Bridge circuit 14 Oscillator 15 Voltmeter 16 Temperature measuring part 17 Torque calculating part 18 Recording medium 100 Bridge circuit 101 Rotating shaft 102 Part to be detected 103 First detection coil 104 Second detection coil 105 Third detection coil 106 Fourth detection coil

Claims

1. A method for obtaining a correction value for a torque sensor arranged around a detection portion of a rotating shaft, comprising: a step of actually measuring an output value at a first reference temperature and an output value at a second reference temperature for the torque sensor from which a correction value is to be obtained; a step of determining a provisional correction function, which is a linear function that indicates the relationship between the temperature and the provisional correction value for the torque sensor from which a correction value is to be obtained, by setting the output value at the first reference temperature as a provisional correction value for the first reference temperature and the output value at the second reference temperature as a provisional correction value for the second reference temperature; a step of substituting at least one non-reference temperature other than the first reference temperature and the second reference temperature into the provisional correction function to obtain a provisional correction value for the at least one non-reference temperature; and a step of obtaining a correction value for the at least one non-reference temperature by correcting the provisional correction value at the at least one non-reference temperature with a correction amount for the at least one non-reference temperature that has been obtained in advance.

2. The method for obtaining a correction value for a torque sensor according to claim 1, wherein the correction amount at the at least one non-reference temperature is obtained by: actually measuring output values ​​at the first reference temperature, the second reference temperature, and the at least one non-reference temperature for at least one test sample having the same configuration as the torque sensor for which the correction value is to be obtained; determining a reference function, which is a linear function that indicates the relationship between the temperature and the provisional output value for the at least one test sample, using the output value at the first reference temperature and the output value at the second reference temperature as a provisional output value; and substituting the at least one non-reference temperature into the reference function to obtain the provisional output value at the at least one non-reference temperature, and based on the difference between the actually measured output value at the at least one non-reference temperature.

3. The method for obtaining a correction value for a torque sensor according to claim 1, wherein the absolute value of the difference between the first reference temperature and the second reference temperature is 10°C or more and 190°C or less.

4. A method for measuring torque on a rotating shaft, which corrects the output value of a torque sensor placed around a detected part of the rotating shaft with a correction value determined in advance according to the temperature of the torque sensor, and calculates the torque applied to the rotating shaft based on the corrected output value of the torque sensor, wherein the correction value is obtained by a method for obtaining a correction value for a torque sensor as set forth in any one of claims 1 to 3.

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