WO1991004474A1

WO1991004474A1 - Temperature compensation apparatus for torque measuring apparatus

Info

Publication number: WO1991004474A1
Application number: PCT/JP1990/001177
Authority: WO
Inventors: Akiyoshi Hanazawa
Original assignee: Kubota Corporation
Priority date: 1989-09-18
Filing date: 1990-09-13
Publication date: 1991-04-04
Also published as: JPH03183924A; JPH0739974B2

Abstract

A temperature compensation apparatus in a torque measuring apparatus, which is provided with a detection coil in order to determine the magnitude of a torque by detecting the change of permeability at a magnetically anisotropic portion of the outer periphery of a shaft when the torque is applied. The change of an excitation current of an excitation coil for exciting the detection coil is correlated with the temperature of a torque detection portion. Therefore, the temperature of the torque detection portion is detected by detecting the excitation current. Sensitivity and zero point of the torque detection output are subjected to temperature compensation on the basis of the detection result of temperature.

Description

Specification

Title of invention

G Temperature compensator for geometry measuring device

Technical field

The present invention relates to a temperature compensator for a torque measuring device.

Background art

As a well-known torque measuring device, a pair of magnetically anisotropic parts are formed on the outer circumference of a torque transmitting shaft, and each magnetic anisotropy when torque is applied to this axis. The change in the magnetic permeability of the magnetic part is detected by a pair of detection coils placed near these magnetic anisotropic parts, and the torque acting on the shaft is determined from the difference between the two detection signals. In this case, the size of the detection coil is converted into an electric signal, and an excitation coil for exciting the detection coil is provided, for example, in Japanese Patent Application Publication No. It is proposed in 1-1 73843.

In this type of torque measuring device, a temperature change occurs in the shaft portion where the magnetically anisotropic portion is formed, and in the torque detecting portion equipped with a detection coil and an excitation coil. As a result, the magnetic and electrical characteristics change, the impedance of the exciting coil changes, and the exciting current changes. As a result, torque detection accuracy fluctuates, for example, a change in zero point output, a change in sensitivity, and an increase in hysteresis. This poses a problem when measuring the torque of equipment that gets relatively hot during operation, such as industrial machinery, motors, engines, and automobiles.

Therefore, in the above-mentioned No. 11 1 73843, the change of the exciting current and the temperature change The excitation current is controlled by the constant voltage control, which keeps the sum of the voltages of the output signals of the detection coil, that is, the value twice the average of both signals, constant. O to prevent this from happening.

It is said that simply performing such a constant voltage control is not enough to prevent fluctuations in the torque detection accuracy, especially when the temperature change is large. Disclosure of inventions with problems

It is an object of the present invention to maintain the detection accuracy even when the temperature of the torque detecting section changes greatly.

To achieve this objective, the temperature compensator for the torque measuring device of the present invention is:

Means for detecting the temperature of the torque detecting section by detecting the exciting current of the exciting coil;

Means for temperature-compensating the electric signal for the magnitude of the torque based on the detection result by the temperature detecting means.

In such a configuration, the exciting current does not react to the torque applied to the shaft, but only to the temperature of the torque detector. For this reason, if the excitation current is detected, the temperature of the torque detector can be detected independently of the state of the applied torque. Since the torque signal is temperature-compensated based on the result of this temperature detection, it is possible to reliably prevent the occurrence of a detection error due to a temperature change, and even at a high temperature. Be able to measure torque accurately BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a circuit diagram of a temperature compensator for a child measuring device according to a first embodiment of the present invention,

2 to 8 are diagrams for explaining the operation of the circuit in FIG. 1,

Figures 9 and 10 show the measured values of the torque detection output at room temperature and at high temperature, respectively.

FIGS. 11 to 14 are circuit diagrams of a temperature compensator for the torque measuring device according to the second to fifth embodiments of the present invention, and FIGS.

FIGS. 15 and 16 are circuit diagrams of examples in which the temperature compensator according to the present invention is applied to a differential transformer.

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 shows a first embodiment of the present invention. Reference numeral 1 denotes a torque transmission shaft, which is made of a soft magnetic and magnetostrictive material. On the outer circumference of the shaft 1, magnetic anisotropic parts 2, 3 which are inclined in the opposite directions at an angle of about 15 ° with the direction of the axis of the shaft 1 and a number of grooves, etc. It is formed by. Around the magnetic anisotropic parts 2 and 3, the detection coils 4 and 5 corresponding to the magnetic anisotropic parts 2 and 3 and the detection coils 4 and 5 are excited. And an excitation coil 6 are provided. The excitation coil 6 is connected to an AC power supply 7, and between the AC power supply 7 and the excitation coil 6, an auto-gain controller 8 and an excitation current detection resistor 9 are connected. Are provided. Rectifier filters 10 and 11 are connected to both ends of the detection resistor 9, respectively. These rectifier filters 10 and 11 are connected to the human-powered side of the differential detector 12 respectively. ing. difference The motion detector 12 detects the exciting current IeX flowing through the exciting coil 6 by taking the difference between the signals from the two rectifying filters 10 and 11. I do.

The output lines 13 and U of the detection coils 4 and 5 are connected to the input sides of the rectifying fins 15 and 16, respectively. The output sides of the filters 15 and 16 are connected to the input side of a computing unit 17 for subtraction. The output side of the arithmetic unit 17 is connected to the output terminal 21 via the automatic gain controller 18, the arithmetic unit 19 for addition, and the V / I converter 20. It is being led. 22 is a load resistance.

'The output side of the differential detector 12 is connected to one input side of a comparator 23, and the other input side of the comparator 23 is connected to a constant voltage generator 24. The output side of the comparator 23 is connected to this automatic gain controller 18 in order to adjust the amplification factor of the automatic gain controller 18. Also, is connected to the input side of the computing unit 19.

The output sides of the rectifier filters 15 and 16 are also connected to the input side of a computing unit 25 for addition. The output side of the computing unit 25 is connected to one input side of the comparator 26, and the other input side of the comparator 26 is connected to the constant voltage generator 24. The output side of the comparator 26 is connected to the automatic gain controller 8 in order to adjust the gain of the automatic gain controller 8. According to this configuration, the change in the magnetic permeability in each of the magnetically anisotropic parts 2 and 3 based on the torque acting on the axis 1 is detected by the detection coils 4 and 5. Detected. At this time, the magnetically anisotropic parts 2 and 3 Are inclined in opposite directions, so that a tensile force acts on one magnetically anisotropic part and a compressive force acts on the other. For this reason, the detection voltage V of one detection Coil g 4 For example other force, increasing by Tsu was the increase in preparative Torque detection voltage V ₂ of the other detection Coil le 5 Decrease with it. In its This arithmetic unit 1 7 by Ri both detection voltage V,, the difference between V 2 V, - if the V ₂ Ru determined, signal or an output corresponding to the change of the bets Torque Remind as in FIG. 5 Appears at terminal 21.

The sum V, + V ₂ of the detection voltages appearing on the output side of the computing unit 25 is compared in the comparator 26 with the reference voltage V ref from the constant voltage generator 24. Then, a control signal is sent from the comparator 26 to the auto gain controller 8, and the excitation is controlled by adjusting the gain of the auto gain controller 8. By controlling the exciting current I ex of the coil 6, the sum V and the value of + V 2 are controlled to be constant. As a result, variations in the characteristics of the device due to temperature changes are roughly compensated.

The exciting current I ex is detected by the detection resistor 9, the rectifying filters 10 and 11, and the differential detector 12. In the configuration of the present torque measuring device, the excitation current Iex does not react to the torque, but only to the temperature of the torque detector. Therefore, if the exciting current lex is detected, the temperature of the torque detecting section is detected independently of the state of the torque applied to the shaft 1. According to the temperature detection result, the differential detector 12 outputs the temperature compensation reference voltage Vt. This voltage Vt is compared with the reference voltage Vref from the constant voltage generator 24 in the comparator 23, and the corresponding torque detection sensitivity is determined. The correction signal voltage V s is output from the comparator 23. At a high temperature, a detection output with a value larger than the torque actually applied to the axis 1 appears, but the correction signal voltage Vs causes an auto gain. The gain of the controller 18 is adjusted, and the auto gain controller 18 outputs a torque detection signal compensated for the sensitivity change due to temperature. You.

FIG. 2 shows a change in the excitation current I ex when the temperature of the torque detector changes. As the temperature rises, the exciting current I ex decreases. Figure 3 shows the change in the temperature compensation reference voltage Vt based on the change in the excitation current Iex, that is, the change in the temperature compensation reference voltage Vt when the temperature of the torque detector changes. As the voltage rises, the temperature compensation reference voltage Vt decreases. FIG. 4 shows the relationship between the temperature compensation reference voltage Vt and the amplification factor of the automatic gain controller 18. As the temperature compensation reference voltage Vt decreases, that is, as the temperature rises, the amplification factor of the auto gain controller 18 decreases.

Figure 5 shows the relationship between torque and output voltage at room temperature. Figure 6 shows the relationship between the two at high temperatures. In FIG. 6, the dashed line indicates that the output of the arithmetic unit 17, that is, only the control in which the values of V and + V 2 are constant, is executed, but the temperature compensation based on the exciting current I e .x is not performed. Indicates output voltage when not performed. The solid line indicates the output voltage of the output of the auto-gain controller 18, that is, the output voltage when temperature compensation based on the excitation current Iex is also performed. V, + a value of V ₂ is the case where only a certain value and name Ru control, inclined or suddenly Tsu Na line shifts to a higher sensitivity than that in the normal temperature Although errors due to variations in sensitivity occur, when temperature compensation is also performed based on the excitation current I ex, the slope becomes almost the same as that at room temperature and almost the same. Sensitivity characteristics have been achieved. Specifically, when only the control in which the values of V and + V2 are constant values is performed, the variation in the torque detection sensitivity due to the temperature change is about +1000 ppm / ^oC. Is equivalent to a 10% measurement error when the temperature of the detector changes by 100 ° C. On the other hand, when temperature compensation based on the detection of the excitation current Iex is also performed, the sensitivity fluctuation can be improved to ± 20 to 30 ppm / ° C at most. .

The correction signal voltage V s from the comparator 23 is also used to correct the output at the zero point. The signal voltage V s for this correction and the output voltage from the auto-gain controller 18 for which the sensitivity correction has been achieved as described above are both used by the arithmetic unit. Entered in 19. Although the arithmetic unit 19 adds and subtracts these two voltages, the degree to which the zero-point output increases or decreases when the temperature of the detection unit fluctuates is measured in advance, and it is determined in advance. By determining the corresponding circuit constant (correction coefficient), the arithmetic unit 19 outputs a signal in which the error due to the fluctuation of the zero point output is compensated.

FIG. 7 shows how the correction signal voltage Vs changes when the temperature compensation reference voltage Vt from the differential detector 12 fluctuates with the temperature change of the detection unit. . The inclination angle of the graph changes according to the degree of fluctuation of the zero point output, and the direction of the inclination is not only in the case of the lower right as shown in the figure but also in the case of the upper right. is there. Figure 8 shows the relationship between torque and output voltage at high temperatures. The solid line indicates the output voltage when temperature compensation based on the output of the computing unit 19, that is, the excitation current Iex, is performed, and the dashed line indicates the output voltage when temperature compensation is not performed. Show. It explains how the error E based on the fluctuation of the zero point output is eliminated by performing the temperature compensation. Specifically, the fluctuation of the zero point output due to the temperature change of the detection unit is about ± 500 ppm / ° C. This means that there is no applied torque when the temperature of the detection unit changes by 100 ° C. This means that an output signal of ± 5% of full scale is generated. On the other hand, when temperature compensation is performed based on the excitation current l ex, the fluctuation of the zero point output can be improved to about 20 to 30 ppm / ° C at most.

Fig. 9 shows the measured values of the relationship between the torque and the output voltage at room temperature (detector temperature: 25 ° C). Figure 10 shows the measured values of the relationship between the torque and the output voltage when the temperature was compensated for the sensitivity and the zero point at high temperatures (detector temperature 125 V). In both cases, the measured values and are shown in. In this Figure 10,

The graph “with sensitivity and zero correction” is a plot of the output appearing at output terminal 21 in FIG. Similarly, the graph “with sensitivity correction only” plots the output of the auto-gain controller 18, and the graph “without correction” plots the output of the calculator 17, respectively. It is a thing that has been dropped.

FIG. 11 shows a second embodiment of the present invention. Here, the computing unit 19 in FIG. 1 is omitted. According to such a configuration, only the temperature compensation of the sensitivity is performed, and the temperature compensation of the zero point is performed. No compensation is made. Therefore, the circuit of Fig. 11 has the characteristic that the fluctuation of sensitivity with temperature change is a problem, but the fluctuation of zero is negligibly small. Suitable for torque measurement equipment.

FIG. 12 shows a third embodiment of the present invention. Here, the automatic gain controller 18 in FIG. 1 is omitted, and only temperature compensation of the zero point is performed, and temperature compensation of the sensitivity is not performed. Therefore, in the circuit of Fig. 12, contrary to the circuit of Fig. 11, the fluctuation of the zero point due to the temperature change is a problem, but the fluctuation of the sensitivity is negligible. It is suitable for a torque measuring device having such a small characteristic.

FIG. 13 shows a fourth embodiment of the present invention. This is a modification of the embodiment shown in FIG. In the circuit of FIG. 11, the comparator 23 compares the temperature compensation reference voltage Vt from the differential detector 12 with the reference voltage Vref from the constant voltage generator 24. In the circuit of FIG. 13, the exciting current lex detected by the detecting resistor 9 and the output of the computing unit 25 are compared by the comparator 23. In both circuits, the sum of the detection voltages V and + V2 appearing on the output side of the computing unit 25 is compared with the reference voltage Vref from the constant voltage generator 24, and this circuit Sum V, +

They agree on the fact that the feedback control is performed so that the value of V 2 becomes constant. Therefore, it is not merely a matter of design matter which signal of the fixed loop is used as the input of the comparator 23, but this is just a matter of design. There is no substantial difference between the circuit in Fig. 11 and the circuit in Fig. 13. No. In the circuit shown in FIG. 13, the automatic gain controller 18 is composed of a resistor 27 and an FET 28.

FIG. 14 shows a fifth embodiment of the present invention. In each of the above embodiments, the sum V of the detected voltage, + V ₂ and the comparison reference voltage V ref to the sum of this V, off I in earthenware pots by ing to a certain value of + V 2 - Dubai Tsu In the circuit of Fig. 14, the excitation voltage V ex of the excitation coil 6 is controlled to be constant.

In FIG. 14, reference numeral 29 denotes a detection unit for the excitation voltage V ex at both ends of the excitation coil 6, and the detection signal is input to the comparator 26 and is compared with the reference voltage V ref from the constant voltage generator 24. Are compared. According to the comparison result, the amplification factor of the auto-gain controller 8 is adjusted so that the excitation voltage Vex becomes a constant value. In this way, even when the excitation voltage V ex of the excitation coil 6 is controlled to be a constant value, the sensitivity and the sensitivity are controlled in the same manner as when controlling the sum V and + V 2 of the detection voltages. Zero compensation is possible.

FIGS. 15 and 16 show examples in which a temperature compensator according to the present invention is applied to a differential trans- former. As shown in the figure, the differential transformer 31 is also generally provided with an excitation coil 6 and a pair of detection coils 4 and 5 similar to the torque measuring device. Therefore, by using exactly the same circuit configuration as that of the torque measuring device, the sensitivity of the detection output when this differential transformer 31 is used under high temperature conditions is improved. Fig. 15 shows a circuit for controlling the sum V and + V2 of the detection power E to be constant, as in Fig. 1. Show. FIG. 16 shows a circuit for controlling the value of the excitation voltage V ex of the excitation coil 6 to be constant, as in the case of FIG. 14. The differential transformer 31 whose temperature is compensated can be used as a displacement detector, a magnetic amplifier, and the like.

Claims

The scope of the claims

A pair of magnetically anisotropic parts are formed on the outer periphery of the torque transmission shaft, and when a torque is applied to this axis, the change in the magnetic permeability of each magnetically anisotropic part is determined by the magnetic field. Detection is performed by a pair of detection coils placed near the anisotropic part, and from the difference between the two detection signals, the magnitude of the torque acting on the shaft is converted to an electric signal. A temperature compensating device in the torque measuring device described above, which has an exciting coil for exciting the detection coil,

A means for controlling the exciting current of the exciting coil so that the sum of the detection signals of the detecting coil becomes a constant value, which is a temperature compensator in the torque measuring device according to claim 1. And means for controlling the exciting current so that the exciting voltage of the exciting coil becomes a constant value.

The temperature compensating device in the torque measuring device according to claim 2, wherein the temperature compensating means includes means for compensating for the sensitivity of the torque signal and means for compensating for the zero point of the torque signal. It has at least one of them.

4. The temperature compensator in the torque measuring device according to claim 3, wherein the means for compensating for the sensitivity of the torque signal is torque. Means for amplifying the signal and means for adjusting the amplification factor of the torque signal amplifying means in accordance with the detected exciting current. 5. A temperature compensating device for a torque measuring device according to claim 4, wherein the means for converting the detected value of the exciting current into a temperature compensating reference voltage corresponding thereto, and the temperature compensating reference voltage as a constant value reference. Means for comparing the voltage and adjusting the gain of the torque signal amplifying means based on the comparison result.

4. A temperature compensator in a torque measuring device according to claim 3, wherein the means for compensating for a zero point of the torque signal converts a detected value of the excitation current into a temperature correction signal corresponding to the exciting current. Means for adding a torque signal and the temperature correction signal.

The temperature compensation device according to any one of claims 1 to 6, further comprising: an excitation coil and a pair of detection coils, instead of the torque measurement device. Applies to differential transformers.