Method for manufacturing a torque measuring device

Abstract

To provide a manufacturing method of a torque measurement device that can suppress a manufacturing time.SOLUTION: A manufacturing method of a torque measurement device comprises: a first step of, as for a plurality of test samples having the same configuration as a torque measurement device targeted for manufacturing, testing to check a coil balance Cb serving as a ratio (R1*R3) / (R2*R4) of a product R1*R3 of resistance values R1 and R3 of two opposite sides constituting one set of opposite sides of four sides of a bridge circuit 8, and a product R2*R4 of resistance values R2 and R4 of two opposite sides constituting other one set of opposite sides of the four sides, and a temperature change rate VT of an output voltage Vo by a temperature fluctuation of a sensor unit 4, and acquiring a relationship X between the coil balance Cb and the temperature change rate VT from a result of the test; and a second step of measuring respective resistance values R1, R2, R3 and R4 of the four sides as for the torque measurement device targeted for manufacturing to obtain the coil balance Cb, obtaining the temperature change rate VT from the relationship X acquired in the first step, using the obtained coil balance Cb.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a torque measuring device and a method for manufacturing the same. [Background technology]

[0002] In recent years, in the automotive field, there has been progress in the development of systems that measure the torque transmitted by the rotating shaft that constitutes the powertrain, i.e., the power transmission mechanism, and use the measurement results to control the output of the engine or electric motor that serves as the power source, or to control the speed change of the transmission.

[0003] Magnetostrictive torque measuring devices have been known as devices for measuring torque transmitted by a rotating shaft. Magnetostrictive torque measuring devices use a rotating shaft equipped with a magnetostrictive effect part whose magnetic permeability changes when torque is applied, and are configured to measure the torque transmitted by the rotating shaft by detecting the change in magnetic permeability of the magnetostrictive effect part when torque is applied as a change in inductance of a detection coil.

[0004] Generally, the change in magnetic permeability of the magnetostrictive effect part due to torque fluctuations is minute, so measures are usually taken to improve measurement sensitivity. One such measure is a conventionally known 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 magnetostrictive effect part 102 that is a part of the axial direction of a rotating shaft 101 as shown in Fig. 9, and the bridge circuit 100 is configured with the four detector coils arranged on the four sides.

[0005] When torque T is applied to the rotating shaft 101, stresses σ with opposite signs (+ and -) act on the outer circumferential surface of the magnetostrictive effect portion 102 in a direction inclined at +45° with respect to the axial direction and in a direction inclined at -45° with respect to the axial direction. Then, due to the inverse magnetostrictive effect, the magnetic permeability increases in the direction in which tensile stress (+σ) acts, and decreases in the direction in which compressive stress (-σ) acts.

[0006] In the bridge circuit 100, the first and third detection coils 103 and 105, which are arranged on one pair of opposite sides of the two pairs of opposite sides that make up the four sides, are detection coils for detecting changes in magnetic permeability on the outer circumferential surface of the magnetostrictive effect section 102 in a direction inclined at +45° with respect to the axial direction, and the second and fourth detection coils 104 and 106, which are arranged on the other pair of opposite sides, are detection coils for detecting changes in magnetic permeability on the outer circumferential surface of the magnetostrictive effect section 102 in a direction inclined at -45° with respect to the axial direction. In this bridge circuit 100, when an input voltage Vi is applied between two end points, namely, points A and C, an output voltage Vo corresponding to the direction and magnitude of torque T applied to the rotating shaft 101 is obtained as the voltage between two midpoints, namely, points B and D. Therefore, torque T can be measured based on this output voltage Vo.

[0007] By using the bridge circuit 100 described above, it is possible to measure torque T with twice the sensitivity compared to measuring torque T by detecting only the change in magnetic permeability in either a direction tilted at +45 degrees to the axial direction or a direction tilted at -45 degrees to the axial direction.

[0008] Incidentally, the resistance values ​​R1 to R4 of the detection coils 103 to 106 that make up the bridge circuit 100 change with temperature fluctuations. Therefore, from the viewpoint of improving the torque measurement accuracy, it is desirable to provide a temperature correction means.

[0009] For this reason, a conventional technology is known in which an amplification correction circuit is provided to convert the output voltage of the bridge circuit into a torque value, and sensor temperature information estimated from the amount of current in the entire bridge circuit is provided to this amplification correction circuit, and temperature correction is performed using this sensor temperature information and correction parameters obtained in advance by a calibration test (see, for example, JP 2018-048956 A). [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Japanese Patent Application Publication No. 2018-048956 Summary of the Invention [Problem to be solved by the invention]

[0011] In order to mass-produce and ship torque measuring devices equipped with conventional temperature compensation means, a calibration test must be performed on each torque measuring device during the manufacturing process to determine the compensation parameters, for example, in the case of the torque measuring device described in JP 2018-048956 A, a calibration test must be performed to identify the curve of the diagram shown in Figure 6 of that publication, i.e., the curve representing the relationship between temperature and ΔVcos and ΔVsin. The reason why such a calibration test must be performed on each torque measuring device is that the resistance values ​​of the resistors on the four sides of the bridge circuit differ from one torque measuring device to another.

[0012] For example, referring to Figure 6 of Japanese Patent Application Laid-Open No. 2018-048956, the calibration test is performed over a temperature range of -60°C to 140°C. In this case, since it is not possible to directly measure the temperature of the bridge circuit of the torque measuring device, it is considered necessary to place the torque measuring device in a test chamber, regard the test chamber temperature as the temperature of the torque measuring device, and perform the calibration test by changing the temperature of the test chamber.

[0013] For efficiency reasons, the temperature used for calibration testing is not changed in 1°C increments, but in 10°C or 50°C increments, with the voltage (ΔVcos, ΔVsin) measured at each temperature change and the correction parameters supplemented on the assumption that the measured values ​​in between change linearly. In any case, it takes a certain amount of time to stabilize the temperature in the testing room at each stage, making this a time-consuming and laborious process.

[0014] Furthermore, since it would be difficult for workers to enter a test room where temperatures exceed 100°C, workers would likely have to wear protective clothing with thermal insulation before entering the room to measure the voltage, or they would have to measure the voltage using a remote-controlled manipulator, which would be a very difficult task either way.

[0015] It is conceivable to perform calibration tests on several torque measuring devices at once, but if you try to do this on a large number of devices, the test room will become larger and temperature control will become more difficult. Also, if many torque measuring devices are crammed into a small test room, it will be difficult to maintain a uniform temperature for each torque measuring device. This limits the number of devices that can be calibrated at once, making it difficult to ensure a sufficient daily production volume.

[0016] An object of the present invention is to provide a method for manufacturing a torque measuring device that can simplify the calibration test for determining the correction parameters and reduce the manufacturing time. [Means for solving the problem]

[0017] In a method for manufacturing a torque measuring device according to one aspect of the present invention, the torque measuring device to be manufactured includes a sensor unit, an oscillator, a voltage measuring unit, and a torque calculating unit.

[0018] The sensor section has a bridge circuit in which four detection coils are arranged on the four sides around the magnetostrictive effect section of the rotating shaft.

[0019] The oscillator applies an input voltage to the two terminals of the bridge circuit.

[0020] The voltage measurement unit measures an output voltage, which is a voltage between two midpoints of the bridge circuit.

[0021] The torque calculation unit calculates the torque applied to the rotating shaft by using the output voltage measured by the voltage measurement unit.

[0022] Furthermore, the torque calculation unit has a temperature measurement function for measuring the temperature of the sensor unit, and a temperature change rate V of the output voltage, which is a correction parameter stored in advance in the torque calculation unit, based on the temperature of the sensor unit measured by the temperature measurement function. T and a function of calculating the torque applied to the rotating shaft based on the output voltage after temperature correction.

[0023] A method for manufacturing a torque measuring device according to one aspect of the present invention includes a first step and a second step.

[0024] The first step is to calculate a coil balance C, 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 out of the four sides to the product R2×R4 of the resistance values ​​R2 and R4 of two opposing sides that make up another pair of opposing sides out of the four sides, for a plurality of test samples that have the same configuration as the torque measuring device to be manufactured. b , and the temperature change rate V T From the results of the test, the coil balance C b and the temperature change rate V T This is the process of obtaining the relationship X.

[0025] In the second step, the resistance values ​​R1, R2, R3, and R4 of the four sides of the torque measuring device to be manufactured are measured to determine the coil balance C b and calculate the coil balance C b Using the above, the temperature change rate V is calculated from the relationship X obtained in the first step. T This is the process of determining the following.

[0026] In one aspect of the present invention, the method for manufacturing a torque measuring device further comprises: T and a third step of storing the result in the torque calculation unit of the torque measuring device to be manufactured.

[0027] In the torque measuring device according to one aspect of the present invention, in the torque measuring device to be manufactured, the temperature change rate V T A recording of the above is attached. [Effects of the Invention]

[0028] According to the method for manufacturing a torque measuring device of one aspect of the present invention, the manufacturing time can be reduced. [Brief explanation of the drawings]

[0029] [Figure 1] FIG. 1 is a cross-sectional view of a sensor portion constituting a torque measuring device according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a perspective view of a sensor unit of the torque measuring device of the first example. [Figure 3] FIG. 3(a) is a development view of a flexible substrate that constitutes the coil unit of the torque measuring device of the first example, and FIG. 3(b) is a view of the flexible substrate as seen from below in FIG. 3(a). [Figure 4] FIG. 4 is a development view of the first, second, third, and fourth detector coils that constitute the coil unit of the torque measuring device of the first example, as viewed from the outside in the radial direction. [Figure 5] Figures 5(a) to 5(d) are development views of the first detection coil, second detection coil, third detection coil, and fourth detection coil that make up the coil unit of the torque measuring device of the first example, each viewed individually from the radially outer side. [Figure 6] FIG. 6 is a schematic circuit diagram of the torque measuring device of the first example. [Figure 7] FIG. 7 is a diagram showing the relationship between the coil balance Cb and the temperature change rate VT of the output voltage. [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

[0030] [Example 1] A first embodiment of the present invention will be described with reference to FIGS.

[0031] 1 and 2 are diagrams showing the structure of a sensor unit 4 constituting a torque measuring device 1 of this embodiment. The torque measuring device 1 of this embodiment is a device for measuring torque transmitted by a rotating shaft 2 and can be incorporated into various mechanical devices. Specific examples of mechanical devices incorporating the torque measuring device 1 of this embodiment include mechanical devices constituting an automobile powertrain, such as automatic transmissions (ATs), belt-type continuously variable transmissions, toroidal continuously variable transmissions, automatic manual transmissions (AMTs), and dual clutch transmissions (DCTs), which change gears under vehicle control, as well as transfers and manual transmissions (MTs). The drive system of the target vehicle, i.e., FF, FR, MR, RR, 4WD, etc., is not particularly important. Specific examples of mechanical devices incorporating the torque measuring device 1 of this embodiment include devices that change the rotation speed of a power shaft using gears, such as reducers and speed increasers constituting wind turbines, railway vehicles, and steel rolling mills.

[0032] In this example, the rotating shaft 2 is a rotating shaft incorporated into a mechanical device that constitutes the powertrain as described above, and is rotatably supported by a rolling bearing (not shown) in a case (not shown) that does not rotate even when in use, and has a magnetostrictive effect part whose magnetic permeability changes depending on the torque being transmitted.

[0033] The rotating shaft 2 has an intermediate shaft portion 3 shown in FIG. 1 at its axially intermediate portion. The outer peripheral surface of the intermediate shaft portion 3 is formed of a cylindrical surface. In this example, the intermediate shaft portion 3 of the rotating shaft 2 functions as a magnetostrictive effect portion. For this purpose, the rotating shaft 2 is made of a magnetic metal. As the magnetic metal constituting the rotating shaft 2, various magnetic steels such as carburizing steels such as SCr420 and SCM420, and carbon steels such as S45C, as specified in JIS, can be used.

[0034] When torque T is applied to the rotating shaft 2, stresses σ with opposite signs act on the outer circumferential surface of the intermediate shaft portion 3, in a direction inclined at +45 degrees to the axial direction and in a direction inclined at -45 degrees 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.

[0035] When implementing the present invention, a compression-hardened layer can be formed by shot peening a portion of the outer circumferential surface of the intermediate shaft portion 3 that is located radially inward of the sensor portion 4, thereby improving the mechanical and magnetic properties of that portion. In this way, the sensitivity and hysteresis of the torque measurement by the torque measuring device 1 can be improved.

[0036] When carrying out the present invention, instead of making the intermediate shaft portion 3 function as the magnetostrictive effect portion, it is also possible to fix a magnetostrictive material that functions as the magnetostrictive effect portion to the outer circumferential surface of the intermediate shaft portion 3. Specifically, it is possible to fit a magnetostrictive material formed in an annular shape onto the outer circumferential surface of the intermediate shaft portion 3, or to fix a magnetostrictive material formed by a coating such as plating or a film-like magnetostrictive material to the outer circumferential surface of the intermediate shaft portion 3.

[0037] 1 is configured in an annular shape as a whole, and is supported and fixed to the case while being coaxially disposed around the intermediate shaft portion 3. In this example, the sensor portion 4 includes a coil unit 13, a back yoke 14, and a holder 15.

[0038] In this example, the coil unit 13 is cylindrically configured and made of a flexible printed circuit board (FPC) 16 (see FIGS. 3(a) and 3(b)) that includes a base film and printed wiring (conductors) held by the base film, and is arranged coaxially around the intermediate shaft portion 3 of the rotating shaft 2. The flexible printed circuit board (FPC) 16 has a first detector coil 9, a second detector coil 10, a third detector coil 11, and a fourth detector coil 12, as shown in FIGS. 4 and 5.

[0039] Specifically, in this example, coil unit 13 is constructed by rolling a strip-shaped flexible substrate 16 as shown in Figures 3(a) and 3(b) into a cylindrical shape and joining both longitudinal ends of flexible substrate 16, for example, by adhesive bonding. Flexible substrate 16 has four wiring layers stacked in the thickness direction, and a first detector coil 9, a second detector coil 10, a third detector coil 11, and a fourth detector coil 12, each formed by printed wiring, are arranged on these wiring layers. These detector coils 9 to 12 are arranged in this order from the radially inner side when strip-shaped flexible substrate 16 is rolled into a cylindrical shape, i.e., when cylindrical coil unit 13 is constructed.

[0040] Fig. 4 shows a development of the first, second, third, and fourth detector coils 9, 10, 11, and 12 as seen from the radially outer side of the coil unit 13. Figs. 5(a) to 5(d) show developments of these detector coils 9 to 12 as individual coils as seen from the radially outer side of the coil unit 13.

[0041] The first detection coil 9 is a detection coil for detecting changes in magnetic permeability on the outer peripheral surface of the intermediate shaft portion 3 in a direction inclined +45° relative to the axial direction. In other words, it is a detection coil that changes its own inductance L1 in response to changes in magnetic permeability in that direction. As shown in FIG. 5(a), the first detection coil 9 includes multiple coil segments 17 arranged at equal intervals in the circumferential direction. These coil segments 17 have a parallelogram shape when viewed radially and include wiring inclined -45° relative to the axial direction of the intermediate shaft portion 3. Adjacent coil segments 17 in the circumferential direction are connected in series by a conductor such as a printed wiring (not shown). That is, although the coil segments 17 are shown schematically in FIG. 5(a) as if they are connected all around, in reality, there is a discontinuity in part of the circumferential direction of the coil segments 17. The coil segments 17 have two ends separated by this discontinuity. Circumferentially adjacent coil pieces 17 are connected in series by connecting one end of each piece to a conductor such as a printed wiring (not shown). This also applies to the second to fourth detection coils 10 to 12 described below.

[0042] The second detection coil 10 is a detection coil for detecting changes in magnetic permeability in a direction inclined at -45° with respect to the axial direction on the outer peripheral surface of the intermediate shaft portion 3; in other words, it is a detection coil that changes its own inductance L2 in response to changes in magnetic permeability in that direction. As shown in FIG. 5(b), the second detection coil 10 has a plurality of coil pieces 18 arranged at equal intervals in the circumferential direction. These coil pieces 18 have a parallelogram shape when viewed in the radial direction and are configured to include wiring inclined at +45° with respect to the axial direction of the intermediate shaft portion 3. Coil pieces 18 adjacent in the circumferential direction are connected in series by a conductor such as a printed wiring (not shown).

[0043] The third detection coil 11 is a detection coil for detecting changes in magnetic permeability in a direction inclined at +45° with respect to the axial direction on the outer peripheral surface of the intermediate shaft portion 3; in other words, it is a detection coil that changes its own inductance L3 in response to changes in magnetic permeability in that direction. As shown in FIG. 5(d), the third detection coil 11 has a plurality of coil pieces 19 arranged at equal intervals in the circumferential direction. These coil pieces 19 have a parallelogram shape when viewed in the radial direction and are configured to include wiring inclined at -45° with respect to the axial direction of the intermediate shaft portion 3. Adjacent coil pieces 19 in the circumferential direction are connected in series by a conductor such as a printed wiring (not shown).

[0044] The fourth detection coil 12 is a detection coil for detecting changes in magnetic permeability in a direction inclined at -45° with respect to the axial direction on the outer peripheral surface of the intermediate shaft portion 3; in other words, it is a detection coil that changes its own inductance L4 in response to changes in magnetic permeability in that direction. As shown in FIG. 5(c), the fourth detection coil 12 has a plurality of coil pieces 20 arranged at equal intervals in the circumferential direction. These coil pieces 20 have a parallelogram shape when viewed in the radial direction and are configured to include wiring inclined at +45° with respect to the axial direction of the intermediate shaft portion 3. Adjacent coil pieces 20 in the circumferential direction are connected in series by a conductor such as a printed wiring (not shown).

[0045] However, when implementing the present invention, the specific shapes and arrangements of the first, second, third, and fourth detection coils are not limited to the configurations in this example, and various conventionally known configurations can be adopted.

[0046] Returning to FIG. 1 , the back yoke 14 is a component that serves as a magnetic path for the magnetic flux generated by the first detector coil 9, the second detector coil 10, the third detector coil 11, and the fourth detector coil 12. The back yoke 14 is made of a magnetic material such as mild steel and is cylindrical in its entirety. The back yoke 14 is arranged coaxially around the coil unit 13. In this example, in this state, a radial clearance is provided between the coil unit 13 and the back yoke 14 in the axial direction. That is, the outer peripheral surface of the coil unit 13 and the inner peripheral surface of the back yoke 14 are spaced apart in the radial direction.

[0047] The holder 15 is a member that holds the coil unit 13 and the back yoke 14, and is made of a non-magnetic material and has an overall annular shape. In this example, the holder 15 has a cylindrical holder cylindrical portion 21, a first outward flange 22 that extends radially outward from the end of one axial side (the left side in FIG. 1 ) of the holder cylindrical portion 21 all the way around, and a second outward flange 23 that extends radially outward from the end of the other axial side (the right side in FIG. 1 ) of the holder cylindrical portion 21 all the way around. The outer diameter of the first outward flange 22 is larger than the outer diameter of the second outward flange 23. The holder 15 is supported and fixed to the case in a state where it is coaxially arranged around the intermediate shaft portion 3.

[0048] In this example, the coil unit 13 is fitted onto the axially intermediate portion of the holder cylindrical portion 21, i.e., onto a portion of the holder cylindrical portion 21 that is located axially between the first outward flange 22 and the second outward flange 23. An end face on one axial side of the back yoke 14 abuts against a radially intermediate portion of a side face on the other axial side of the first outward flange 22, and the inner peripheral surface of the end portion on the other axial side of the back yoke 14 is fitted onto the outer peripheral surface of the second outward flange 23 by interference fitting or the like.

[0049] When implementing the present invention, a configuration different from that of this example can be adopted for the coil unit including the first detection coil 9, the second detection coil 10, the third detection coil 11, and the fourth detection coil 12, the back yoke arranged around the coil unit, the holder that holds the coil unit and the back yoke, etc.

[0050] Fig. 6 is a schematic circuit diagram of the torque measuring device 1 of this example. As shown in Fig. 6, the torque measuring device 1 of this example includes the above-mentioned sensor unit 4, oscillator 5, voltage measuring unit 6, and torque calculation unit 7. In this example, of the elements of the schematic circuit diagram shown in Fig. 6, elements other than the detection coils 9 to 12 can be fixed to, for example, a flexible substrate 16, or fixed to another substrate (not shown), such as a substrate installed on the vehicle body side.

[0051] The sensor unit 4 configures a bridge circuit 8 in which four detector coils, a first detector coil 9, a second detector coil 10, a third detector coil 11, and a fourth detector coil 12, are arranged on four sides. That is, the bridge circuit 8 has two end points, point A and point C, and two midpoints, point B and point D. The first detector coil 9 is arranged on the side between point D and point A. The second detector coil 10 is arranged on the side between point A and point B. The third detector coil 11 is arranged on the side between point B and point C. The fourth detector coil 12 is arranged on the side between point C and point D.

[0052] That is, in bridge circuit 8, a first detector coil 9 and a third detector coil 11 are disposed on one of two pairs of opposite sides that make up the four sides, namely, the side between points D and A and the side between points B and C, which are detector coils for detecting changes in magnetic permeability in a direction inclined at +45° with respect to the axial direction on the outer peripheral surface of intermediate shaft portion 3. Furthermore, a second detector coil 10 and a fourth detector coil 12 are disposed on the other of the two pairs of opposite sides, namely, the side between points A and B and the side between points C and D, which are detector coils for detecting changes in magnetic permeability in a direction inclined at -45° with respect to the axial direction on the outer peripheral surface of intermediate shaft portion 3.

[0053] The oscillator 5 is capable of applying an input voltage Vi, which is an AC voltage, between the two end points A and C of the bridge circuit 8.

[0054] The voltage measuring unit 6 is capable of measuring the output voltage Vo, which is the voltage between the two midpoints of the bridge circuit 8, namely, points B and D.

[0055] That is, when the torque measuring device 1 of this example is used, when the oscillator 5 applies an input voltage Vi between the two end points A and C of the bridge circuit 8 and an AC current flows through the first detector coil 9, the second detector coil 10, the third detector coil 11, and the fourth detector coil 12, currents flow in opposite directions in the circumferentially adjacent coil pieces 17, 18, 19, and 20, as shown by arrows α1, α2, α3, and α4 in Figures 5(a) to 5(d), through the first detector coil 9, the second detector coil 10, the third detector coil 11, and the fourth detector coil 12. In other words, the circumferentially adjacent coil pieces 17, 18, 19, and 20 are connected to each other so that currents flow in these directions. As a result, an AC magnetic field is generated around the first detection coil 9, the second detection coil 10, the third detection coil 11, and the fourth detection coil 12, and part of the magnetic flux of this AC magnetic field passes through the surface layer of the intermediate shaft portion 3.

[0056] In this state, when a torque T is applied to the intermediate shaft portion 3 in the direction indicated by the arrow CW in Fig. 1, a tensile stress (+σ) in the +45° direction with respect to the axial direction and a compressive stress (-σ) in the -45° direction with respect to the axial direction act on the rotating shaft 2. Then, due to the inverse magnetostriction effect, the magnetic permeability of the intermediate shaft portion 3 increases in the +45° direction where the tensile stress (+σ) acts, and decreases in the -45° direction where the compressive stress (-σ) acts.

[0057] On the other hand, the first detector coil 9 and the third detector coil 11 are configured to include wiring that is inclined at -45° with respect to the axial direction of the intermediate shaft section 3, and part of the magnetic flux of the AC magnetic field generated around the wiring passes through the surface layer portion of the intermediate shaft section 3 in the +45° direction, which is the direction in which magnetic permeability increases. As a result, the inductances L1 and L3 of the first detector coil 9 and the third detector coil 11 each increase. Also, the second detector coil 10 and the fourth detector coil 12 are configured to include wiring that is inclined at +45° with respect to the axial direction of the intermediate shaft section 3, and part of the magnetic flux of the AC magnetic field generated around the wiring passes through the surface layer portion of the intermediate shaft section 3 in the -45° direction, which is the direction in which magnetic permeability decreases. As a result, the inductances L2 and L4 of the second detector coil 10 and the fourth detector coil 12 each decrease.

[0058] In contrast, when a torque T is applied to the intermediate shaft 3 in the direction indicated by the arrow CCW in FIG. 1, the opposite effect occurs to the above-described case, causing the inductances L1 and L3 of the first and third detector coils 9 and 11 to decrease, and the inductances L2 and L4 of the second and fourth detector coils 10 and 12 to increase.

[0059] In either case, in the bridge circuit 8, an output voltage Vo corresponding to the direction and magnitude of the torque T applied to the rotating shaft 2 is obtained as the voltage between the two midpoints, points B and D. In this example, this output voltage Vo can be measured by the voltage measuring unit 6.

[0060] The torque calculation unit 7 has a function of calculating the torque T applied to the rotating shaft 2 using the output voltage Vo measured by the voltage measurement unit 6.

[0061] Torque calculation unit 7 has a temperature measurement function that measures the temperature of sensor unit 4, specifically, the temperature change ΔT in sensor unit 4 from a preset reference temperature Ta. When implementing the present invention, various conventionally known configurations can be used to realize this temperature measurement function, specifically, a configuration that measures the temperature change ΔT of sensor unit 4 by software processing the amount of current across bridge circuit 8 (see, for example, JP 2018-048956 A), or a configuration that includes a thermocouple or temperature sensor that physically measures the temperature change ΔT of sensor unit 4. Here, reference temperature Ta can be set to any temperature, for example, room temperature (approximately 20°C).

[0062] The torque calculation unit 7 previously stores the correction parameter, ie, the temperature change rate V of the output voltage of the bridge circuit 8. T is stored. This temperature change rate V T is the rate of change of the output voltage due to temperature fluctuations of the sensor unit 4, and specifically, is a rate that indicates how many percent the output voltage deviates for every 1° C. change in temperature at the sensor unit 4.

[0063] The torque calculation unit 7 calculates the temperature change amount ΔT of the sensor unit 4 measured by the temperature measurement function and the temperature change rate V T In other words, when the current temperature of the sensor unit 4 deviates from the reference temperature Ta by a temperature change amount ΔT, the torque calculation unit 7 has a function of correcting the deviation amount (ΔV) of the output voltage of the bridge circuit 8 caused by this deviation. For this purpose, in this example, the torque calculation unit 7 multiplies the temperature change amount ΔT of the sensor unit 4 measured by the temperature measurement function by the temperature change rate V T Multiplying by △V=△T×V TThe deviation (ΔV) is calculated by subtracting the determined deviation (ΔV) from the output voltage Vo measured by the voltage measurement unit 6, thereby calculating the output voltage Va (=Vo-ΔV) that is estimated to be measured when the temperature of the sensor unit 4 is the reference temperature Ta. In other words, the torque calculation unit 7 corrects the output voltage Vo measured by the voltage measurement unit 6 to the output voltage Va.

[0064] The torque calculation unit 7 calculates the torque T applied to the rotating shaft 2 based on the temperature-corrected output voltage Va. That is, the torque calculation unit 7 stores in advance a relationship Y between the output voltage of the bridge circuit 8 at a reference temperature Ta and the torque T. The torque calculation unit 7 uses the relationship Y to calculate the torque T from the temperature-corrected output voltage Va.

[0065] As described above, in this example, the torque calculation unit 7 performs temperature compensation on the output voltage Vo of the bridge circuit 8 and calculates the torque T based on the temperature-compensated output voltage Va. Therefore, regardless of temperature fluctuations in the sensor unit 4, it is easy to ensure the measurement accuracy of the torque T.

[0066] Next, a method for manufacturing the torque measuring device 1 of this embodiment will be described.

[0067] The method for manufacturing the torque measuring device 1 of this example includes a first step and a second step.

[0068] The first step is to determine the relationship X, specifically the coil balance C, which is conceptually shown by a straight line in FIG. 7, for the torque measuring device 1 to be manufactured. b and the temperature change rate V of the output voltage of the bridge circuit 8 T Here, the coil balance C bis 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 out of the four sides that make up the bridge circuit 8 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 out of the four sides. That is, in the first step, each of the torque measuring devices 1 that are the manufacturing target and each of the coil balances C b A plurality (a large number) of test samples with different coil balances C are prepared. b , and the temperature change rate V T A test is performed to check the relationship X in FIG. 7, and the relationship X in FIG. 7 is obtained from the test result.

[0069] The second step is to determine the temperature change rate V T That is, in the second step, for the torque measuring device 1 to be manufactured, a measuring device such as an impedance analyzer is used to measure the resistance values ​​of each of the four sides constituting the bridge circuit 8, i.e., the resistance values ​​R1, R2, R3, and R4 of the first detector coil 9, the second detector coil 10, the third detector coil 11, and the fourth detector coil 12. Then, the coil balance C is calculated from the measured resistance values ​​R1, R2, R3, and R4. b Then, the calculated coil balance C b Using the relationship X of FIG. 7 obtained in the first step, the coil balance C b The temperature change rate V corresponding to T Ask for.

[0070] The relationship X in FIG. 7 obtained in the first step can be shared among the torque measuring devices 1 when the torque measuring devices 1 to be manufactured are mass-produced.

[0071] The method for manufacturing the torque measuring device 1 of this embodiment further includes a third step.

[0072] The third step is to calculate the temperature change rate V obtained in the second step. Tis stored in the torque calculation unit 7 of the torque measuring device 1 to be manufactured.

[0073] When carrying out the present invention, the third step can be carried out at a manufacturing plant for the torque measuring device 1, or at a manufacturing plant for the automobile in which the torque measuring device 1 is installed. When the third step is carried out at a manufacturing plant for the automobile, when the torque measuring device 1 is shipped from the manufacturing plant for the torque measuring device 1 to the automobile manufacturing plant, the temperature change rate V determined in the second step is applied to a part of the exterior of the torque measuring device 1, as shown by the solid line or the chain line in FIG. T The temperature change rate V recorded on the recording medium 24 can be attached to the vehicle. T and read the temperature change rate V T is stored in the torque calculation unit 7.

[0074] In the example shown by the solid line in Fig. 2, the recording medium 24 is attached to a portion of the circumferential direction of the outer circumferential surface of the back yoke 14, which is part of the exterior, and in the example shown by the chain line in Fig. 2, the recording medium 24 is attached to the axial side surface of the holder 15, which is part of the exterior. However, the location where the recording medium 24 is attached to the exterior must be determined based on the temperature change rate V recorded on the recording medium 24. T Any location can be used as long as it can be read.

[0075] According to the method for manufacturing the torque measuring device 1 of this embodiment, the manufacturing time can be reduced even though the torque measuring device 1 to be manufactured has a structure having a temperature correction function.

[0076] That is, in this example, among the first, second, and third steps included in the manufacturing method of the torque measuring device 1, the first step, which takes a relatively long time, does not need to be performed individually for each of the torque measuring devices 1 when mass-producing the torque measuring devices 1 to be manufactured. That is, the relationship X in FIG. 7 obtained in the first step can be shared by all of the torque measuring devices 1. Then, in the second step, the coil balance C is calculated from the resistance values ​​R1, R2, R3, and R4. bThe temperature change rate V T Therefore, the manufacturing time of the torque measuring device 1 can be significantly reduced compared to the prior art, which requires time-consuming and difficult calibration tests to be performed on each of these torque measuring devices. [Explanation of symbols]

[0077] 1 Torque measuring device 2 rotation axes 3 Intermediate shaft 4 Sensor section 5. Oscillators 6 Voltage measurement section 7 Torque calculation section 8 Bridge Circuit 9 First detection coil 10 Second detection coil 11 Third detection coil 12 Fourth detection coil 13 Coil unit 14 Back Yoke 15 Holder 16 Flexible PCB 17 Coil pieces 18 Coil pieces 19 Coil pieces 20 Coil pieces 21 Holder cylindrical part 22 First outward flange 23 Second outward flange 24 Records 100 Bridge circuit 101 Rotation axis 102 Magnetostrictive effect part 103 First detection coil 104 Second detection coil 105 Third detection coil 106 4th detection coil

Claims

1. a sensor unit having a bridge circuit in which four detection coils are arranged around the magnetostrictive effect part of the rotating shaft and are arranged on four sides; an oscillator that applies an input voltage to two terminals of the bridge circuit; a voltage measuring unit for measuring an output voltage, which is a voltage between two midpoints of the bridge circuit; a torque calculation unit that calculates a torque applied to the rotating shaft using the output voltage measured by the voltage measurement unit, The torque calculation unit has a temperature measurement function for measuring the temperature of the sensor unit, and a correction parameter stored in advance in the torque calculation unit, which is a temperature change rate V of the output voltage. T and a function of calculating a torque applied to the rotating shaft based on the output voltage after temperature correction. A method for manufacturing a torque measuring device, comprising: For a plurality of test samples having the same configuration as the torque measuring device to be manufactured, a coil balance C is calculated, which is the ratio (R1×R3) / (R2×R4) of the product R1×R3 of the resistance values ​​R1, R3 of two opposing sides constituting one pair of opposing sides out of the four sides to the product R2×R4 of the resistance values ​​R2, R4 of two opposing sides constituting another pair of opposing sides out of the four sides. b , and the temperature change rate V T From the results of the test, the coil balance C b and the temperature change rate V T a first step of obtaining a relationship X between For the torque measuring device to be manufactured, the resistance values ​​R1, R2, R3, and R4 of the four sides are measured to determine the coil balance C b and the calculated coil balance C b Using the above, the temperature change rate V is calculated from the relationship X obtained in the first step. T and a second step of determining Method for manufacturing a torque measuring device.

2. The temperature change rate V obtained in the second step T The method for manufacturing a torque measuring device according to claim 1 , further comprising a third step of storing the above-mentioned in the torque calculation unit of the torque measuring device to be manufactured.

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