JPH06241934A - Examination device for magnetostrictive torque sensor - Google Patents

Abstract

PURPOSE:To enable easy examination of process circuit's function based an the output signal of the process circuit by generating digital unbalanced signal with a control circuit, and with this, supplying a signal processing circuit with calibration signal. CONSTITUTION:After power is turned on, a calculation control circuit 23 reads, out of a memory 24, zero point correction and sensitivity correction data, and writes them in D/A convertors 16 and 20, and at the same time, based on the output of a temperature sensor 25, reads correction data for zero point shift and sensitivity fluctuation that follow temperature changes out of the memory 24, and then writes them in the D/A convertors 16 and 21, respectively. Based on the data of convertors 16, 20 and 21, zero point, sensitivity and temperature fluctuation are corrected. At inspection of a signal processing circuit, calibration signal is sent from a line 27 to the circuit 23, which generates digital unbalanced signal to be supplied to a differential amplifier 14 through the convertor 16. As a result, only when no abnormality exists with respective circuit elements, corresponding output appears at the signal processing circuit, and based on this, presence of abnormality is decided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetostrictive torque sensor inspection device.

[0002]

2. Description of the Related Art As a known magnetostrictive torque sensor, a pair of magnetic anisotropic portions are formed on the outer peripheral surface of a torque transmission shaft, and the magnetic permeability of each magnetic anisotropic portion when torque is applied to this shaft. Change is detected by a pair of coils arranged near these magnetic anisotropy parts, both detection signals are input to the signal processing circuit, and from the difference, the magnitude of the torque acting on the shaft is detected as an electric signal. It is known that the output is made in.

[0003]

When such a magnetostrictive torque sensor fails, malfunctions such as an output that does not correspond to the magnitude of the torque applied to the shaft or an output that exceeds the rated output will occur. There is a risk. But,
The known magnetostrictive torque sensor has a problem that it is difficult to determine whether or not a malfunction has occurred due to a failure, and it is difficult to identify the failure location even if it is recognized as a failure. .

Therefore, an object of the present invention is to solve such a problem and to make it possible to easily inspect the presence / absence of a failure in the magnetostrictive torque sensor and the failure location.

[0005]

In order to achieve this object, the present invention provides a magnetic anisotropic portion formed on the outer periphery of a torque detecting shaft and the magnetic anisotropy when a torque is applied to the torque detecting shaft. A coil capable of detecting a change in magnetic permeability of the anisotropic portion and outputting a signal according to the magnitude of the torque, and a signal processing circuit for processing an output signal from the coil to calculate the magnitude of the applied torque. And a control circuit capable of generating a digital unbalanced signal and supplying a calibration signal based on the digital unbalanced signal to the signal processing circuit, and the signal processing when the calibration signal is supplied. The function of this signal processing circuit can be inspected from the output signal of the circuit.

[0006]

In such a configuration, when the control circuit outputs the unbalanced signal and supplies the calibration signal to the signal processing circuit, if the function of the signal processing circuit is normal, the sensor output corresponding to the unbalanced signal is output. A signal will appear. However, when an abnormality occurs in the function of the signal processing circuit, a sensor signal corresponding to such an imbalance does not appear, so that it is detected that the signal processing circuit is out of order.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, 6 is a torque detecting shaft, which is made of a material having soft magnetism and magnetostriction. On the outer circumference of the shaft 6, a pair of magnetic anisotropic parts 7, 7 are formed by a large number of grooves, etc., which are inclined by ± 45 degrees with respect to the direction of the axis of the shaft 6 and are inclined in opposite directions. ing. The large number of grooves are formed, for example, by rolling the shaft 6, and the characteristics thereof are improved by performing heat treatment or shot peening after rolling.

Around the magnetic anisotropy portions 7 and 7, a pair of detection coils 8 and 8 corresponding to the magnetic anisotropy portions 7 and 7, and an exciting coil for exciting the detection coils 8 and 8. 9,
9 and are provided. The exciting coils 9, 9 are connected to an oscillating circuit 10 for supplying an alternating current.

The output lines from the detection coils 8 and 8 are
They are connected to the differential amplifier 12 via the rectifier circuits 11 and 11, respectively. A differential amplifier 14 is provided between the coil 8 and the rectifying circuit 11. In this differential amplifier 14,
The output side of the D / A converter 16 for zero point correction and correction of zero point variation due to temperature change is connected. This D / A
A constant voltage generation circuit 15 is connected to the converter 16. The output line from the differential amplifier 12 is passed through the filter 13
It is connected to the D / A converter 20 for sensitivity correction. Also D
The output line from the / A converter 20 is connected to the D / A converter 21 for correcting the sensitivity variation due to the temperature change.
The torque signal line 3 is connected to the output side of the D / A converter 21.

An output line from a digital arithmetic control circuit 23 provided in the torque sensor is connected to each D / A converter 16, 20, 21. The arithmetic control circuit 23 is provided with a memory 24, and is connected with the data input / output line 4 and the calibration request signal line 27. A temperature sensor 25 can detect the temperature of the torque sensor. The output line from this temperature sensor 25 is
It is connected to the arithmetic and control circuit 23 through the A / D converter 26. With the above, a signal processing circuit that processes the output signals from the detection coils 8 and calculates the magnitude of the applied torque is configured.

In such a structure, the torque sensor can be selectively switched between the measurement mode and the correction mode. First, the correction mode will be described. For zero point correction, that is, zero balance correction, at room temperature, for example, 25
The output signal V1 when the torque is not applied to the shaft 6 is output to the torque signal line 3 as it is at ° C and measured by an appropriate means. Then, the zero-point correction data for the sensor is obtained from the measured data, and this is written in the memory 24 in the sensor from the data input / output line 4 via the arithmetic control circuit 23. The arithmetic control circuit 23 stores the zero correction data in the memory 24.
Read from and write to the D / A converter 16. Then, the output signal is corrected by the correction based on the output of the D / A converter 16.
V1 becomes 0, and the zero point correction is performed.

Next, the correction of the zero point variation due to the temperature change will be described. First, put the torque sensor in the constant temperature bath,
The temperature in the tank is changed without applying torque to the shaft 6, and the sensor output V5 at this time is measured. At the same time, the output V6 of the temperature sensor 25 of the torque sensor is measured by the data input / output line 4 via the arithmetic control circuit 23. And
From these measurement data, data for correcting the zero-point fluctuation due to temperature change is calculated, and the calculation result is written from the data input / output line 4 to the memory 24 in the sensor via the calculation control circuit 23.

When the ambient temperature of the torque sensor changes, the output V6 of the temperature sensor 25 changes accordingly. Then, the arithmetic control circuit 23 stores, in accordance with the output V6, data for correcting the zero-point fluctuation associated with the temperature change in the memory 24.
Read out and write the data to the D / A converter 16. As a result, even if the ambient temperature of the sensor changes, the sensor output V5 in the state where the torque is not applied to the shaft 6 is always 0.

Similarly, the arithmetic control circuit 23 reads the sensitivity correction data from the memory 24 and writes it in the D / A converter 20 so that the output V4 of the D / A converter 20 is constant corresponding to the rated torque. It becomes a voltage, and the sensitivity is corrected by this. Similarly, when the ambient temperature of the torque sensor changes and the output V6 of the temperature sensor 25 changes, the arithmetic control circuit 23 outputs data for correcting the sensitivity variation due to the temperature change according to the output V6. The data is read from the memory 24 and the data is written in the D / A converter 21. As a result, even if the ambient temperature of the sensor changes, it is possible to perform correction so that the sensor sensitivity is always constant.

The measurement mode will be described. When the power of the circuit is turned on, the arithmetic control circuit 23 reads the zero point correction data and the sensitivity correction data from the memory 24, and D and D respectively.
Write to the A / A converter 16 and the D / A converter 20. Further, the arithmetic control circuit 23, immediately after the power is turned on, based on the output V6 of the temperature sensor 25, the data for correcting the zero point variation due to the temperature change, and the data for correcting the sensitivity variation due to the temperature change. Read from memory 24, D
Write to the A / A converter 16 and the D / A converter 21.

Then, the zero point correction and the sensitivity correction are performed based on the data written in the D / A converters 16 and 20. Further, based on the data written in the D / A converters 16 and 21, even if the ambient temperature of the torque sensor changes, it is corrected so that the zero point and the sensitivity of the sensor become constant.

When the signal processing circuit is inspected, the calibration control signal line 27 is used to check the operation control circuit.
Send a digital calibration request signal to 23. Then, the arithmetic control circuit 23 generates a digital unbalanced signal and writes it in the D / A converter 16. D / A converter
16 supplies the corresponding analog calibration signal to the differential amplifier 14. Then, an unbalanced signal is input to the signal processing circuit, so if there is no abnormality in the signal processing circuit configured by each circuit element,
The corresponding output V5 appears. If the expected output does not appear, it can be determined that some failure has occurred in the signal processing circuit.

As described above, the D / A converter 16 is used not only as a circuit element for correcting the zero point but also as a circuit element for correcting the zero point variation due to the temperature change, and further includes a signal processing circuit. It is also used as a circuit element for inspection.

FIG. 2 shows the structure of a torque sensor of the type that digitally corrects the zero point correction and the sensitivity correction in the signal processing circuit. Here, the output line from the filter 13 provided on the output side of the differential amplifier 12 is connected to the arithmetic control circuit 23 via the A / D converter 31. The torque signal line 3 is derived from the arithmetic control circuit 23 via the D / A converter 32.

In this digital correction type torque sensor, the same zero point correction as in the analog type, sensitivity correction, correction of zero point variation due to temperature change, and correction of sensitivity variation due to temperature change are arithmetically controlled. It is performed by digital calculation in the circuit 23.

When the signal processing circuit is inspected, FIG.
Calibration request signal line 27
A digital calibration request signal is supplied to the arithmetic and control circuit 23 by.

FIG. 3 shows a torque sensor of a modified example of the analog correction method. Here, only one magnetic anisotropic portion 7 is formed on the outer peripheral surface of the torque detection shaft 6 so as to be inclined with respect to the shaft center. A coil 41 is arranged around the magnetic anisotropic portion 7.

The coil 41 is shown by a solid line in the figure, and is connected to the oscillation circuit 10 via a temperature sensitive resistor 42 and a resistor 43 for roughly adjusting the zero-point fluctuation due to temperature change. The temperature-sensitive resistor 42 can be installed between the resistor 43 and the coil 41 as shown by a broken line in the figure, or can be installed in another place. resistance
43 has a resistance value approximately equal to the impedance of the coil 41. A rectifier circuit is provided between the oscillator circuit 10 and the temperature sensitive resistor 42.
45 are connected in parallel, and the low-pass filter 46 is connected to the output side of the rectifier circuit 45, so that the excitation voltage detection circuit 47
Are configured.

The differential amplifier 14, the rectifier circuit 48, and the low-pass filter 49 are connected in this order to the output line from the coil 41, that is, the line in parallel with the temperature-sensitive resistor 42 shown by the broken line in the figure. It constitutes the torque detection circuit 50. The output side of the low-pass filter 49 in the torque detection circuit 50 and the output side of the low-pass filter 46 in the excitation voltage detection circuit 47 are both connected to the input side of the differential amplifier 51. The output side of the differential amplifier 51 is connected to the amplifier 52.

The output side of the amplifier 52 is connected to a polarity judgment circuit 53 for detecting the direction of the torque applied to the torque detection shaft 1 by a known method, and a gain switching circuit 54. By these circuits 53 and 54, the gain of the torque detection signal from the amplifier 52 can be switched based on the direction of the torque applied to the torque detection shaft 6. Reference numeral 59 is a feedback line, which is connected to the arithmetic and control circuit 23 via the A / D converter 60.

In such a configuration, the oscillation circuit 10
The excitation voltage Vex is supplied to the coil 41. At this time, when torque is applied to the torque detection shaft 6, the magnetic permeability of the magnetic anisotropic portion 7 changes, which changes the impedance of the coil 41. At this time, the torque detection voltage corresponding to the impedance change of the coil 41, that is, the change in the coil output, becomes maximum and the torque detection sensitivity becomes maximum because the resistance value of the resistor 43 connected in series to the coil 41. Is equal to the impedance of the coil 41. Therefore, as described above, the resistance value of the resistor 43 is set to the coil value.
By making it almost equal to the impedance of 41, the torque detection sensitivity becomes large.

When the excitation voltage Vex changes for some reason, the output of the detection voltage also changes accordingly, but the rate of change is equal to the rate of change of the excitation voltage Vex. On the other hand, in the differential amplifier 51, the output of the filter 46 of the excitation voltage detection circuit 47 is subtracted from the output of the filter 49 of the torque detection circuit 50. Therefore, there is an advantage that the torque output does not change no matter how the exciting voltage Vex changes.

The temperature characteristic of the torque detection output is measured in advance, and the temperature sensing resistor 42 is adjusted so that the output V1 of the differential amplifier 51 becomes zero when the torque is not acting on the torque detection shaft 6 and the torque is zero. The resistance value, that is, the correction constant is determined. In this way, even if the torque sensor changes in temperature, the output V1 whose output fluctuation is roughly compensated for appears in the differential amplifier 51 in response to the temperature change. After all, the output V1 of the differential amplifier 51 appears to prevent the occurrence of an error due to the fluctuation of the excitation voltage Vex of the oscillator circuit 10 and the occurrence of an error due to the temperature change.

The output V1 of the differential amplifier 51 appears as zero-corrected by the differential amplifier 14 as in the case of the embodiment of FIG. That is, the zero-point variation due to the temperature change is roughly adjusted by the temperature-sensitive resistor 42 and then finely adjusted by the differential amplifier 14. Further, the D / A converter 16 and the differential amplifier 14 of this embodiment not only perform the zero point correction but also finely adjust the zero point variation due to the temperature change. Further, as in the case of FIG. 1, by sending a digital calibration request signal to the arithmetic control circuit 23 through the calibration request signal line 27,
The signal processing circuit can be inspected.

FIG. 4 shows a modified embodiment of the present invention in which only one magnetic anisotropic portion 7 is provided corresponding to FIG. 3, but its correction method is the digital correction method as in the case of FIG. The following is an example. The operation is the same as that of the embodiment shown in FIGS. 2 and 3, respectively.

[0031]

As described above, according to the present invention, it is possible to supply a calibration signal based on a digital unbalanced signal to a signal processing circuit, forcibly creating an unbalanced state, and the signal processing circuit at that time. Since the function of this signal processing circuit can be inspected from the output signal of, the reliability of the signal processing circuit of the magnetostrictive torque sensor can be improved, and if there is a faulty part, that part can be easily checked. Can be specified.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a magnetostrictive torque sensor inspection device of the present invention.

FIG. 2 is a circuit diagram showing another embodiment of the inspection apparatus.

FIG. 3 is a circuit diagram showing still another embodiment of the inspection device.

FIG. 4 is a circuit diagram showing still another embodiment of the inspection device.

[Explanation of symbols]

 6 torque detection axis 7 magnetic anisotropy section 8 detection coil 14 differential amplifier 16 D / A converter 23 arithmetic control circuit 27 calibration signal line

Claims (1)

[Claims] 1. A magnetic anisotropy portion formed on the outer circumference of a torque detection shaft and a change in magnetic permeability of the magnetic anisotropy portion when torque is applied to the torque detection shaft are detected, A coil that can output a signal according to the magnitude of torque, a signal processing circuit that processes the output signal from this coil to calculate the magnitude of the applied torque, and a digital unbalance signal that generates the digital unbalance signal. A control circuit capable of supplying a calibration signal based on a balance signal to the signal processing circuit, and inspects the function of the signal processing circuit from the output signal of the signal processing circuit when the calibration signal is supplied. An inspection device for a magnetostrictive torque sensor, which is characterized in that it is made possible.