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

Abstract

To reduce the time required for tests to acquire correction values while ensuring torque measurement accuracy.SOLUTION: For a torque sensor targeted for correction value acquisition, 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 measured to determine a temporary correction function f, which is a linear function showing the relation between temperature t and a temporary correction value Ct. At least one non-reference temperature tn1 to tn6, other than the first and second reference temperatures, is substituted into the temporary correction function f to obtain the temporary correction values Ctn1 to Ctn6 at least at one non-reference temperature tn1 to tn6. Then, the temporary correction values Ctn1 to Ctn6 at least at one non-reference temperature tn1 to tn6 are corrected using correction amounts ΔCn1 to ΔCn6 previously obtained for at least one non-reference temperature tn1 to tn6 to obtain the corrected values Cn1 to Cn6 at least at one non-reference temperature tn1 to tn6.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[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. [Background technology]

[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 method using a bridge circuit 100 as shown in Fig. 8. In this method, four detector coils, namely, first detector coil 103, second detector coil 104, third detector coil 105, and fourth detector coil 106, are arranged around a cylindrical detector part 102, which is a part 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 (+ and -) act on the outer circumferential surface of the detection target 102 in two directions: one tilted at a predetermined angle (for example, +45 degrees) in a predetermined direction 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. Then, 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 detector coil 103 and third detector coil 105, located on one pair of opposite sides of two pairs of opposite sides that make up the four sides, are detector coils for detecting changes in magnetic permeability on the outer peripheral surface of detection target 102 in a direction inclined at a predetermined angle relative to the axial direction. Second detector coil 104 and fourth detector coil 106, located on the other pair of opposite sides, are detector coils for detecting changes in magnetic permeability on the outer peripheral surface of detection target 102 in a direction inclined at a predetermined angle in a direction opposite to the predetermined direction relative to the axial direction. In bridge circuit 100, when an AC voltage (input voltage) Vi is applied between two end points, namely, 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 the voltage between two midpoints, namely, points B and D. Therefore, torque T can be calculated based on this output value Vo.

[0006] By using the bridge circuit 100 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 constituting 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 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. Therefore, 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. 2018-48956 describes a magnetostrictive torque measuring device (torque sensor) that can detect torque with high accuracy regardless of temperature changes.

[0010] In the conventional torque measuring device described in JP 2018-48956 A, an output value (sine component and cosine component) at a preset reference temperature is stored, and the 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 2018-48956 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 degrees) within the temperature range in which the torque sensor is normally used (for example, a range of approximately -40 degrees to 120 degrees).

[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 reaches the predetermined temperature, after which 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 Publication No. 2023-127315 describes a manufacturing method that can reduce the manufacturing time of a torque measuring device that has 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, the 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 part) 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, measure the resistance values ​​R1, R2, R3, and R4 of the four sides of the bridge circuit to obtain the coil balance C b 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. [Prior art documents] [Patent documents]

[0017] [Patent Document 1] Japanese Patent Application Publication No. 2018-48956 [Patent Document 2] Japanese Patent Application Publication No. 2023-127315 Summary of the Invention [Problem to be solved by the invention]

[0018] In the conventional manufacturing method described in Patent Publication No. 2023-127315, tests to obtain actual output values ​​are not performed 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. [Means for solving the problem]

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

[0021] A method for acquiring a correction value of a torque sensor according to a first aspect of the present disclosure includes: measuring an output value at a first reference temperature and an output value at a second reference temperature of the torque sensor from which a correction value is to be obtained; determining a provisional correction function, which is a linear function indicating a 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; 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 at the at least one non-reference temperature; correcting the provisional correction value at the at least one non-reference temperature by a correction amount at the at least one non-reference temperature that has been obtained in advance, to obtain a correction value at the at least one non-reference temperature; Equipped with.

[0022] A torque sensor correction value acquisition method according to a second aspect of the present disclosure is the torque sensor correction value acquisition method according to the first aspect of the present disclosure, further comprising: The correction amount at the at least one non-reference temperature is 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 from which a correction value is to be obtained; determining a reference function, which is a linear function that indicates the relationship between the temperature of the at least one test sample and the provisional output value, by setting 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; The output value is calculated based on the difference between the provisional output value at the at least one non-reference temperature obtained by substituting the at least one non-reference temperature into the reference function and the output value actually measured at the at least one non-reference temperature.

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

[0024] A fourth aspect of the present disclosure provides a method for measuring torque on a rotating shaft, which 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 the fourth aspect of the present disclosure, the correction value is acquired by the torque sensor correction value acquisition method according to any one of the first to third aspects of the present disclosure. [Effects of the Invention]

[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. [Brief explanation of the drawings]

[0027] [Figure 1] FIG. 1 is a perspective view schematically illustrating an example of a torque sensor to which a correction value acquisition method for a torque sensor according to an embodiment of the present disclosure is applied. [Figure 2] FIG. 2 is a schematic cross-sectional view of the torque sensor taken along an imaginary plane including the central axis. [Figure 3] FIG. 3 is a diagram of the first, second, third, and fourth detector coils that constitute the torque sensor, viewed from the outside in the radial direction. [Figure 4] Figure 4(a) is an expanded view of the first detection coil when viewed from the radial outside in a standalone state, Figure 4(b) is an expanded view of the second detection coil when viewed from the radial outside in a standalone state, Figure 4(c) is an expanded view of the third detection coil when viewed from the radial outside in a standalone state, and Figure 4(d) is an expanded view of the fourth detection coil when viewed from the radial outside in a standalone state. [Figure 5] FIG. 5 is a diagram schematically showing a torque measuring device including the torque sensor. [Figure 6] FIG. 6(A) is a diagram schematically showing the results when the relationship between temperature and output value was measured for a test sample, and FIG. 6(B) is a diagram schematically showing the amount of correction at each temperature. [Figure 7] Figure 7(A) is a diagram that schematically shows the results when the output value at a first reference temperature and the output value at a second reference temperature are measured for a torque sensor from which a correction value is to be obtained, and Figure 7(B) is a diagram that explains a method for determining a correction value at a non-reference temperature from the relationship shown in Figure 7(A). [Figure 8] FIG. 8 is a diagram showing a bridge circuit of a conventional torque measuring device. [Figure 9] FIG. 9 is a perspective view of a rotating shaft for explaining the direction of stress that occurs when torque is applied to the rotating shaft. DETAILED DESCRIPTION OF THE INVENTION

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

[0029] Below, we will first explain the structure of the torque measuring device 1, which is configured to include the torque sensor 4 that is the subject of this example, then explain a method for obtaining a correction value for the torque sensor 4, and further explain a method for detecting the torque T applied to the rotating shaft 2 using the torque measuring 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 with 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 has 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 formed of a cylindrical surface whose outer diameter does not change in the axial direction. In this case, a modified layer whose magnetostriction characteristics 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 part 3, is made of a material having magnetostrictive properties. As a material having magnetic properties, either a material having a positive magnetostrictive constant or a material having a negative magnetostrictive constant can be used. 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 mechanical structures), SUS (stainless steel), SCr (chrome steel), SCM (chrome molybdenum steel), or SNCM (nickel chrome molybdenum steel). Alternatively, a part or all of the rotating shaft 2, including the detected part 3, can be covered with a magnetostrictive film such as a nickel alloy.

[0037] Alternatively, when the torque sensor 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 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 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 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 rotation 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 partially cut cylindrical shape.

[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 arranged coaxially around the detection target portion 3 of the rotation 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 between them.

[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 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, and / or a wiring accommodating portion for accommodating cables and / or signal lines that electrically connect the detection coils 10a to 10d to an external device.

[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 10a to 10d arranged around the bobbin portion .

[0050] The number, configuration, and arrangement of the multiple detection coils 10a to 10d 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 10a to 10d can be arranged overlapping each other in the radial direction and / or arranged side by side in the axial direction.

[0051] In this example, the multiple detector coils 10a to 10d are configured by four detector coils 10a to 10d arranged to overlap one another in the radial direction. Specifically, the four detector coils 10a to 10d are arranged to overlap one another 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] However, when implementing the present disclosure, the multiple detection coils may also 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 having 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] However, when implementing the present disclosure, each detection coil can also be configured 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 detector coils 10a to 10d, the first detector coil 10a and the third detector coil 10c are detector coils for detecting 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 detected part 3. In other words, the first detector coil 10a and the third detector coil 10c are detector coils that 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 detector coils 10a to 10d, the second detector coil 10b and the fourth detector coil 10d are detector coils for detecting 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 detected part 3. In other words, the second detector coil 10b and the fourth detector coil 10d are detector coils that change their own inductance in response to 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 formed 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 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 relative to the axial direction.

[0059] 4(a) to 4(d), the coil pieces 12a to 12d are shown schematically. In reality, the wiring pattern that makes up the coil pieces 12a to 12d has a discontinuous portion, and the coil pieces 12a to 12d have two ends sandwiching the discontinuous portion. Circumferentially adjacent coil pieces 12a to 12d have one end connected to the other by a conductor such as a wiring pattern (not shown), and are connected in series.

[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 coils 10a to 10d 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 coils 10a to 10d coaxially with the detection coils 10a to 10d, 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. However, when implementing the present disclosure, some or all of the oscillator, the voltmeter, the temperature measuring unit, and the torque calculating unit may also be provided inside or around the torque sensor.

[0064] The oscillator 14 applies an AC voltage (input voltage) Vi between a junction A between the first detection coil 10a and the second detection coil 10b and a junction 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 temperatures of the detection coils 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 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. The temperature measurement unit 16 is configured to determine the amount of change (amount of temperature change) Δt in the current temperature of the torque sensor 4 from an arbitrarily set reference temperature t0, based on the AC voltage Vi applied to the bridge circuit 13.

[0069] For this purpose, the temperature measurement unit 16 previously calculates, experiments, or the like to determine the magnitude Vi0 of the AC voltage at the reference temperature t0, and the relationship between the temperature change Δt and the change ΔVi of the AC voltage magnitude, and stores these in memory. The temperature measurement unit 16 determines the change ΔVi of the AC voltage magnitude Vi input via a lock-in amplifier or the like from the pre-stored AC voltage magnitude Vi0 at the reference temperature t0, and determines the change (temperature change) Δt of the current temperature t of the torque sensor 4 from the reference temperature t0 based on the change ΔVi and the above relationship. Then, the current temperature t of the torque sensor 4 (= t0 + Δt) can be determined by adding the change Δt to the reference temperature t0.

[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 / or 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 and the magnitude T and direction (CW or CCW) of the torque applied to the rotating shaft 2, which has been determined in advance by calculation, experiment, etc.

[0075] The temperature measurement unit 16 and the torque calculation unit 17 can be implemented on one microcomputer, for example, but the temperature measurement unit 16 and the torque calculation unit 17 may also be implemented on different microcomputers.

[0076] <How to obtain torque sensor correction values> A correction value acquisition method for acquiring 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] As a preliminary preparation, 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.

[0078] In the preliminary test, first, the test sample is heated to the first reference temperature t s1 , second reference temperature t s2, at least one non-reference temperature t n1 ~t n6 The output value E of torque sensor 4 at s1 , E s2 , E n1 ~E n6 Measure the actual value.

[0079] 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.

[0080] 1st 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 the second reference temperature t s2 The absolute value of the difference between |t s1 -t s2 Although not limited thereto, the first reference temperature t can be set to 10 degrees or more and 190 degrees or less, and preferably 60 degrees or more and 130 degrees or less. The temperature range in which the torque sensor 4 is normally used is, for example, a range of about -20 degrees to 120 degrees, although not limited thereto. In this example, the first reference temperature t s1 is set to 20 degrees, and the second reference temperature t s2 is set to 80 degrees.

[0081] At least one non-reference temperature t n1 ~t n6 is a temperature range in which the torque sensor 4 is normally used, and a first reference temperature t s1 and the second reference temperature t s2 At least one non-reference temperature t n1 ~t n6 Although not limited to this, the first reference temperature t s1 and the second reference temperature t s2In this example, it is preferable to set at least one non-reference temperature t n1 ~t n6 is the first reference temperature t from the range of -20 to 120 degrees. s1 20 degrees, and the second reference temperature t s2 There are a total of six settings, each at 20 degrees, except for 80 degrees.

[0082] Output value E s1 , E s2 , E n1 ~E n6 In order to measure the torque sensor 4 of the test sample, for example, the torque sensor 4 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 room, and the temperature (room temperature) in the test room is set to a predetermined test temperature (first reference temperature t s1 , second reference temperature t s2 , or non-reference temperature t n1 ~t n6 ) and leave it for a certain time until the temperature of the torque sensor 4 reaches the test temperature. After the certain time has passed, 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 n1 ~E n6 By repeating this process 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 n1 ~t n6 The output value E of torque sensor 4 at s1 , E s2 , E n1 ~E n6 Measure the actual value.

[0083] The order of measurements is not particularly limited, and may be, for example, from low temperature to high temperature.

[0084] Next, the first reference temperature t s1Output value E at s1 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 f0:Et=a0×t+b0 (a0 and b0 are constants) is calculated, which is a linear function that indicates the relationship between the temperature t and the provisional output value Et for the test sample.

[0085] Then, at least one non-reference temperature t n1 ~t n6 At least one non-reference temperature t obtained by substituting into the reference function f0 n1 ~t n6 The provisional output value Et n1 ~Et n6 and at least one measured non-reference temperature t n1 ~t n6 Output value E at n1 ~E n6 Difference ΔE n1 (=Et n1 -E n1 )~ΔE n6 (=Et n6 -E n6 ) is calculated. This difference ΔE n1 ~ΔE n6 Based on at least one non-reference temperature t n1 ~t n6 The correction amount ΔC n1 ~ΔC n6 (See FIG. 6(B)). s1 The correction amount ΔC s1 and the second reference temperature t s2 The correction amount ΔC s2 are both 0.

[0086] Specifically, when at least one test sample is composed of one test sample, the difference ΔE obtained using the one test sample n1 ~ΔE n6 The correction amount ΔC n1 ~ΔC n6 It can be used as.

[0087] If at least one test sample is composed of multiple test samples, the difference ΔE calculated for each test sample n1 ~ΔE n6 The average value of the correction amount ΔC n1 ~ΔC n6 It can be used as.

[0088] 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. n1 ~t n6 The correction amount ΔC n1 ~ΔC n6 can be commonly used for torque sensors 4 having the same configuration as the test sample.

[0089] Correction value C for correcting the output value Vo of torque sensor 4, which is the object of correction value acquisition n1 ~C n6 To obtain the correction value, first, the 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.

[0090] Output value Vo s1 , Vo s2 The measurement of the output value E in the preliminary test is basically s1 , E s2 , E n1 ~E n6 This can be done in the same manner as in the measurement of

[0091] Output value Vo s1 , 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.

[0092] 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 given time has elapsed, a predetermined AC voltage Vi is applied between contacts A and C by oscillator 14, and the voltage between contacts B and D is measured by voltmeter 15 as an output value Vo. s1 Then, the room temperature is detected as the second reference temperature t s2 and the temperature of the torque sensor 4 is set to the second reference temperature t s2 After the given time has elapsed, a predetermined AC voltage Vi is applied between contacts A and C by oscillator 14, and the voltage between contacts B and D is measured by 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.

[0093] 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 is performed to obtain a provisional correction function f:v=a×t+b (a and b are constants), which is a linear function showing the relationship between the temperature t of the torque sensor 4 and the provisional correction value v, as shown in FIG. 7(A).

[0094] Then, at least one non-reference temperature t n1 ~t n6 is substituted into the provisional correction function f, and the at least one non-reference temperature t n1 ~t n6Provisional correction value Ct n1 ~Ct n6 The process of obtaining the above is carried out.

[0095] Then, at least one non-reference temperature t n1 ~t n6 Provisional correction value Ct n1 ~Ct n6 is calculated in advance by performing a preliminary test at least one non-reference temperature t n1 ~t n6 The correction amount ΔC n1 ~ΔC n6 By correcting the temperature by at least one non-reference temperature t n1 ~t n6 Correction value C in n1 ~C n6 Specifically, a process of obtaining the provisional correction value Ct n1 ~Ct n6 Correction amount ΔC n1 ~ΔC n6 By adding n1 (=Ct n1 +ΔC n1 )~C n6 (=Ct n6 +ΔC n6 ) is obtained (see Figure 7(B)).

[0096] 1st reference temperature t s1 Correction value C in s1 is the provisional correction value Ct s1 That is, the first reference temperature t measured before the torque sensor 4 is disposed around the rotating shaft 2. 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 measured before the torque sensor 4 is disposed around the rotating shaft 2. s2 Output value Vo at s2 is.

[0097] The correction value Ct calculated as described above is 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 the manufacturing factory, and the recording medium 18 can be attached to the surface of the torque sensor 4 (holder 5 or magnetic ring 6).

[0098] <How to calculate the torque applied to the rotating shaft> When the torque T applied to the rotating shaft 2 is determined 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 3 of the rotating shaft 2 is converted into the correction value C (C s1 , C s2 , C n1 ~C n6 ) and calculates the torque T of the rotating shaft 2 based on the corrected output value Vc.

[0099] 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.

[0100] Next, the torque calculation unit 17 calculates the output value Vo by adding a correction value C (C s1 , C s2 , C n1 ~C n6 ) to obtain the corrected output value Vc (=Vo+C).

[0101] 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 the non-reference temperature t n1 ~t n6 If the temperature is outside of the first reference temperature t s1 , second reference temperature t s2 , and at least the non-reference temperature t n1 ~tn6 The output value Vo can be corrected using the correction value C at the closest temperature among the first reference temperature t s1 , second reference temperature t s2 , and at least the non-reference temperature t n1 ~t n6 The output value Vo may be corrected using an average or weighted average of two temperatures among these that are closest to the temperature t of the torque sensor 4.

[0102] 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 the non-reference temperature t n1 ~t n6 If the temperature t of the torque sensor 4 is lower than the lowest temperature among the above, the correction value C at the lowest temperature can be used to correct the output value Vo. Alternatively, the correction value C at the temperature t can be obtained by adding the correction amount ΔC at the lowest temperature to the provisional correction value Ct obtained by substituting the temperature t of the torque sensor 4 into the provisional correction function f. Also, if 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 the non-reference temperature t n1 ~t n6 If the temperature is higher than the maximum temperature among the temperatures above, the output value Vo can be corrected using the correction value C at the maximum temperature. Alternatively, the correction value C at the temperature t can be obtained by adding the correction amount ΔC at the maximum temperature to a provisional correction value Ct obtained by substituting the temperature t of the torque sensor 4 into the provisional correction function f.

[0103] 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.

[0104] 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.

[0105] In particular, in the method for obtaining a correction value for the torque sensor 4 of this embodiment, in order to obtain the correction value C, the torque sensor 4 for which the correction value is to be obtained is subjected to a first reference temperature t s1 and the second reference temperature t s2 and the 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.

[0106] Furthermore, according to the method for obtaining the correction value of the torque sensor 4 of this embodiment, the first reference temperature t s1 and the second reference temperature t s2 and the output value Vo at two temperatures s1 , Vo s2 By obtaining 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 n1 ~t n6 Correction value C in n1 ~C n6 can be obtained. That is, according to the correction value acquisition method for the torque sensor 4 of this example, unlike the conventional torque sensor described in JP 2018-48956 A, it is not necessary to acquire output values ​​for each torque sensor at multiple (three or more) temperatures while changing the temperature by a fixed amount within the temperature range in which the torque sensor is normally used. 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.

[0107] If the voltmeter 15 detects the sine and cosine components of the output value (output voltage) of the torque sensor 4 and the torque calculation unit 17 is configured to calculate the torque T applied to the rotating shaft 2 based on the sine and cosine components, the correction value C can also be determined separately for the sine and cosine components. If the torque calculation unit 17 is configured to calculate the torque T applied to the rotating shaft 2 based only on the sine or cosine component of the output value (output voltage) of the torque sensor 4, the correction value C can also be determined for only the sine or cosine component. [Explanation of symbols]

[0108] 1 Torque measuring device 2 rotation axes 3. Detected part 4 Torque Sensor 5 Holder 6 Magnetic ring 7 Bobbin section 8 First outward flange 9 Second outward flange 10a First detection coil 10b Second detection coil 10c Third detection coil 10d Fourth detection coil 11 Flexible PCB 12a~12d Coil pieces 13 Bridge Circuit 14 Oscillators 15 Voltmeter 16 Temperature measurement section 17 Torque calculation section 18 Records 100 Bridge circuit 101 Rotation axis 102 detection target 103 First detection coil 104 Second detection coil 105 Third detection coil 106 4th detection coil

Claims

1. A method for acquiring a correction value of a torque sensor disposed around a detection target portion of a rotating shaft, comprising: measuring an output value at a first reference temperature and an output value at a second reference temperature of the torque sensor from which a correction value is to be obtained; determining a provisional correction function, which is a linear function indicating a 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; 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 at the at least one non-reference temperature; correcting the provisional correction value at the at least one non-reference temperature by a correction amount at the at least one non-reference temperature that has been obtained in advance, to obtain a correction value at the at least one non-reference temperature; A method for obtaining a correction value of a torque sensor, comprising:

2. The correction amount at the at least one non-reference temperature is 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 from which a correction value is to be obtained; determining a reference function, which is a linear function that indicates a relationship between the temperature of the at least one test sample and the provisional output value, by setting 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; the output value is calculated based on a difference between the provisional output value at the at least one non-reference temperature obtained by substituting the at least one non-reference temperature into the reference function and an actually measured output value at the at least one non-reference temperature. The method for obtaining a correction value for a torque sensor according to claim 1 .

3. a difference between the first reference temperature and the second reference temperature is 10 degrees or more and 190 degrees or less; The method for obtaining a correction value for a torque sensor according to claim 1 .

4. A method for measuring torque on a rotating shaft, comprising: correcting an output value of a torque sensor disposed around a detection target portion of the rotating shaft with a correction value determined in advance in accordance with a temperature of the torque sensor; and calculating a torque applied to the rotating shaft based on the corrected output value of the torque sensor, A method for measuring torque of a rotating shaft, wherein the correction value is acquired by the method for acquiring a correction value of a torque sensor according to any one of claims 1 to 3.

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