JPH0452535A - Distortion detecting apparatus - Google Patents

Abstract

PURPOSE:To detect abnormality of a detecting circuit by synchronously detecting outputs of two detecting coils with driving timings in a positive and a negative directions of an alternating current driving circuit, respectively, and then smoothing/amplifying the outputs thereby obtaining two distortion detecting outputs. CONSTITUTION:An output between two terminals of detecting coils 3a, 3b is input to differential amplifier circuits 5a, 5b, respectively. Outputs from the circuits 5a, 5b are input to synchronous detecting circuits 8a, 8b through capacitors 12a, 12b, where the outputs are synchronously detected by a first and a second synchronous detecting signals synchronized with the driving timing in a positive and a negative directions of an alternating current driving circuit 7. Inductances of the coils 3a, 3b are differentially processed in the detected outputs, and the thermal stress or bending stress when both of the inductances are changed in the same direction is cancelled. Therefore, when the detected outputs are smoothed and amplified at 9a, 9b to be generated as outputs Vout 1, Vout 2, these outputs are reverse in polarity to the impressed torque. If the circuits are turned defective or abnormal, one of the outputs becomes abnormal, thereby making it possible to detect the abnormality of the circuits.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a distortion detection device.

[Conventional technology]

Figure 2 shows a conventional device of this type (Japanese Patent Application No. 63-309217).
1 is a passive shaft to which an external force is applied, and 2a is a passive shaft to which an external force is applied.
, 2b are magnetic layers formed on the passive shaft 1, and the magnetic layer 2a
has a magnetic anisotropy of +45°, and the magnetic layer 2b has a magnetic anisotropy of +45°.
It has magnetic anisotropy of 3a, 3b are magnetic layers 2a, 2b
The detection coils 4 are respectively wound around the detection coils 3a connected in series.

3b is an intermediate potential output terminal; 7 is an AC drive circuit that applies an AC voltage to both ends of the detection coil 3a3b; 5a and 5b are the detection coils 3a with the voltage of the intermediate potential output terminal 4 as a reference;
, 3b, a differential amplifier circuit that detects the potential difference between the voltages at both ends of the differential amplifier circuits 5a and 3b; 6, an adder circuit that adds the outputs of the differential amplifier circuits 5a and 5b; 8, based on the synchronous detection signal from the AC drive circuit 7;
A synchronous detection circuit synchronously detects the output of the adder circuit 6, 9 is an AC-DC conversion circuit that smooths and amplifies the pulsating current signal output from the synchronous detection circuit 8, and 10 is an output terminal.

FIG. 3 shows the specific configuration of the AC drive circuit 7, with Q, ~Q
, is a transistor,■. ~■2 are detection coils 3a, 3b
31 to S4 are transistors Q
, -Q, is the timing signal for the operation. FIG. 4 shows a timing chart of the operation, in which S+, S2 are L and Sx,
If S- is H, then Q,,Q.

is on, Qz and Q are off, and Vl=VCiv2-
0, and a positive current flows through the detection coils 3a and 3b. Conversely, S,,S,is H and S3. When S4 is L, V z = V c c and V + = O, and a negative current flows through the detection coils 3a and 3b.

FIG. 5 shows the configuration of the synchronous detection circuit 8, in which Q5 is a transistor, 12 is an input terminal to which the output of the adder circuit 6 is input,
3 is an output terminal, and 14 is a resistor. FIG. 6 shows a timing chart of the operation, and (a) shows a synchronous detection signal, which is transmitted from the AC drive circuit 7 to the transistor Qs.
It has a certain phase difference with the AC drive signal output from the AC drive circuit 7. ■) shows the output waveform of the adder circuit 6, (C) shows the transistor Q
, (b) shows the output waveform from the output terminal 13. Transistor Q shows the on/off operation of the synchronous detection signal.
During this period, it is on, and the output of the adder circuit 6 is not output from the output terminal 13. On the other hand, when the phase detection signal becomes L, the transistor Q is turned off, and the output of the adder circuit 6 is outputted from the output terminal 13 as it is. Therefore, noise components in the output of the adder circuit 6 are removed by the synchronous detection circuit 8.

Next, the operation of the above configuration will be explained. When an external force such as torque is applied to the passive shaft 1, strain occurs in the magnetic layers 2a and 2b, and their magnetic permeabilities change in opposite directions. On the other hand, the AC drive circuit 7 outputs an AC voltage and an AC current as shown in FIG. 4, and applies this output to both ends of the detection coils 3a and 3b. The detection coils 3a, 3b detect the change in magnetic permeability of the magnetic layers 2a, 2b as a change in self-inductance, and the output between each end of the detection coils 3a, 3b is an induced voltage according to the change in inductance, and the intermediate potential is It is input as a reference potential to differential amplifier circuits 5a and 5b and differentially amplified. Differential amplifier circuit 5a.

The outputs of 5b are added by an adder 6, and then sent to a synchronous detection circuit 8.
, it is detected by a synchronous detection signal synchronized with either the positive or negative drive timing of the AC drive circuit 7, and noise components are removed. The pulsating signal resulting from this synchronous detection is smoothed and amplified by the AC-DC conversion circuit 9, and output as a distortion detection signal from the output terminal 1o.

In the conventional device described above, the detection coil 3a.

Since the excitation drive of the magnetic layer 3b and the detection of changes in permeability of the magnetic layers 2a and 2b are performed in separate paths, it is easy to adjust the characteristics.
Furthermore, the AC drive circuit 7 allows the drive IT current to flow in both directions with a large amplitude, thereby expanding the operating magnetic field range and reducing the influence of disturbance magnetic fields.

However, in the above-mentioned conventional device, synchronous detection is performed at one timing by either the forward drive or the reverse drive of the AC drive circuit, and the synchronous detection circuit is
The output of l8 now includes an error.

A conventional device that improves the above points (Patent Application No. 1-93720)
No.) is shown in Figure 7. In the figure, 8a and 8b are synchronous detection circuits that synchronously detect the output of the adder circuit 6, and the synchronous detection circuit 8a detects the output using a first synchronous detection signal that is synchronized with the positive drive timing of the AC drive circuit 7. The synchronous detection circuit 8b performs detection using a second synchronous detection signal synchronized with the negative drive timing of the AC drive circuit 7. Synchronous detection circuit 8a.

The circuit configuration of 8b is the same as that in FIG. 11 is a differential amplifier circuit that differentially amplifies the outputs of the synchronous detection circuits 8a and 8b.

Next, the operation of the conventional device shown in FIG. 7 will be explained using the time chart shown in FIG. The AC drive circuit 7 is shown in Fig. 8 (
As shown in FIG. 8(a), drive voltages are output at drive timings in both positive and negative directions, and the adder circuit 6 outputs distortion components as shown in FIG. 8(b). The first synchronous detection signal is the AC drive circuit 7
The second synchronous detection signal is output from the AC drive circuit 7 in synchronization with the positive drive timing as shown in FIG. 8(C), and the second synchronous detection signal is outputted from the AC drive circuit 7 in synchronization with the negative drive timing as shown in FIG. 8(d). Output. The synchronous detection circuits 8a and 8b are the first and second
The detection output shown in FIGS. 8(e) and 8(f) is output in response to the synchronous detection signal. The differential amplifier circuit 11 differentially amplifies the outputs of the respective synchronous detection circuits 8a and 8b to generate the output shown in FIG. 10 as a distortion detection signal.

In the conventional device shown in FIG. 7, the distortion output is detected at both positive and negative driving timings of the AC drive circuit 7, and the output after detection is differentially amplified, so the error is canceled out and the distortion detection accuracy is improved. The effects of disturbance magnetic fields are also canceled out.

[Problem to be solved by the invention] However, in the conventional device described above, the output is 1
Therefore, even if an abnormality occurred in the detection circuit, it could not be detected.

In addition, since the detection coils 3a and 3b are connected in series and the power supply voltage is divided by the inductance and internal resistance of the two detection coils 3a and 3b, no matter what post-processing is used, each detection coil The outputs of 3a and 3b include the inductance component of the other, and the behavior of each cannot be measured independently.Therefore, changes in inductance due to application of external force and changes in inductance due to missing magnetic layers 2a and 2b, etc. could not be separated, and abnormalities in the magnetic layers 2a, 2b or the detection circuit could not be detected.

The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a strain detection device that can easily detect abnormalities in a magnetic layer or a detection circuit.

[Means to solve the problem]

The strain detection device according to the present invention includes an AC drive circuit that applies an AC voltage to a series connection body of each detection coil, and an AC drive circuit that applies an AC voltage to a series connection body of each detection coil, and a first and second synchronous detection circuits that perform synchronous detection using first and second synchronous detection signals;
and a first and second smoothing amplifier circuit for smoothing and amplifying the outputs of the second synchronous detection circuit, respectively.

Further, the strain detection device according to the present invention is mounted on a passive shaft, and has first and second magnetic components whose magnetic permeability changes due to strain, and whose magnetic permeability is set to a maximum state in a state of no external stress. an AC drive circuit that applies an AC voltage to the parallel connection of the detection coils; and first and second synchronization circuits that synchronize the output of each detection coil with the positive and negative drive timings of the AC drive circuit, respectively. This device includes first and second synchronous detection circuits that perform synchronous detection using a detection signal, and first and second smoothing amplifier circuits that smooth and amplify the outputs of the first and second synchronous detection circuits, respectively.

[For production]

In this invention, the outputs of the first and second detection coils are synchronously detected by the positive and negative drive timings of the AC drive circuit, respectively, and then smoothed and amplified,
Two strain detection powers are obtained.

Furthermore, in the magnetic layer of this invention, the magnetic permeability is set to a maximum state in a state of no external stress, and the stress-sensitive region of the magnetic layer is one for tensile stress and one for compressive stress, and only one of the two forms of stress is generated. The output changes. Furthermore, an AC voltage is applied to the parallel connection of each detection coil, and the inductance of each detection coil is not included in the inductance of the other.

〔Example〕

A first embodiment of the present invention will be described below with reference to the drawings. 1st f! l indicates the configuration of the first embodiment of this invention,
9a and 9b are first and second smoothing amplifier circuits that smooth and amplify the outputs of the synchronous detection circuits 8a and 8b, respectively; 12a and 1;
2b is a differential amplifier circuit 5a, 5b and a synchronous detection circuit 8a, 1
31). The other configurations are the same as before.

Next, the operation of the first embodiment will be explained.

Here, the drive voltage of the AC drive circuit 7 is shown in FIG. 9(a).

(As shown in bl, let V, ,V, and V , = V
The current i flowing through the coils 3a and 3b during the interval ec is as follows. However, the inductances of the detection coils 3a and 3b are L+ and Lz, the resistance bones are rl and rz, and L=L, +
Let L, , R=r, 10r. At this time, if the voltages generated in each of the detection coils 3a, 3b are E, Eb, then the waveforms of E, Eb are shown in FIGS. 9(C) and 9(d).

Next, these voltages E- and Eb are applied to the synchronous detection circuit 8a.

8b and is detected by the first and second synchronous detection signals synchronized with V, , Vb, and the following is obtained. Next, V, =-V. In the interval of , if r=r =r as an ideal state, then the following is obtained. With the detection output shown in formulas ■ and ■,
A differential between Ll and L2 is achieved, and the thermal stress and bending stress that cause L+ and L2 to change in the same direction are canceled. Here, by applying torque, L++L! changes differentially (L + ”” Lo+Δl,, Lz=L.

ΔL), the equation 0.0 becomes, and the change in E, , Et, has the opposite polarity with respect to ΔL. Therefore, the detection outputs are converted into smoothing amplifier circuits 9a and 9, respectively.
b, smooth amplification, output VautlIV0ut2
Output as Suru, Cono output V , , tl, V 0.
t2 has a polarity opposite to the applied torque as shown in FIGS. 10(a) and 10(c). In this way, two highly accurate outputs are obtained in which thermal stress and bending stress are canceled, and if a defect occurs in any part of the circuit other than the passive shaft 1 or the magnetic layers 2a and 2b, one of the outputs will become an abnormal output. Therefore, abnormality detection can be easily performed.

FIG. 11 shows a second embodiment of the present invention. In this embodiment, synchronous detection circuits 8a and 8 synchronously detect the output of the differential amplifier circuit 5a using first and second synchronous detection signals, respectively.
The signal is synchronously detected by c, differentially amplified by the differential amplifier circuit 13a, further smoothed and amplified by the smoothing amplifier circuit 9a, and outputted. Get atl.

Similarly, the output of the differential detection circuit 5b is synchronously detected by the synchronous detection circuits 8b and 8d, which synchronously detect the output using the first and second synchronous detection signals, respectively, and differentially amplified by the differential amplifier circuit 13b. The output V is smoothed and amplified by the smoothing amplifier circuit 9b. , we get 2.

In this way, the distorted output is detected at the positive/negative re-drive timing of the AC drive circuit 7, and the output after detection is differentially amplified.
As with the conventional device shown in FIG. 7, the distortion detection accuracy can be doubled, and the disturbance resistance can also be improved.

FIG. 12 shows a third embodiment of the invention, 14a, 1
4b is an amplifier, and 15a and 15b are current detection resistors.

Further, the detection coils 3a and 3b are connected in parallel to the AC drive circuit 7. When forming the magnetic layers 2a and 2b, a magnetostrictive material having a -H curve is directly plated on the passive shaft 1 as shown in FIG. (2) The magnetic layers 2a and 2b are bonded to the passive shaft 1 using an adhesive that exhibits a large volume change when bonded, and compressive strain is applied to the magnetic layers 2a and 2b. (2) Put the passive shaft 1 into a high or low temperature state to form the magnetic layer 2a.

2b is adhered and subjected to compressive strain or tensile strain. Use methods such as

In the above configuration, the magnetostriction constant λ of the magnetic layers 2a and 2b is λ
>0, the magnetic permeability increases due to tensile stress, and the magnetic permeability decreases due to compressive stress. ,′,〈0, the magnetic permeability decreases due to tensile stress, and the magnetic permeability increases due to compressive stress. Therefore, when the initial state is set as shown in FIG. 13 and the magnetic permeability is maximized, there is a possibility that the magnetic permeability will increase and will only change to the decreasing side. Therefore, the relationship between stress σ and magnetic permeability is as shown in Figure 14(a) when λ>0, and as shown in Figure 14(b) when λ<0. .

Therefore, the output for the torque of the magnetic layers 2a and 2b is the first
As shown in FIG. 5, only one output changes in response to positive or negative torque T.

Further, in this embodiment, the detection coils 3a and 3b are connected in parallel to the AC drive circuit 7, and the respective inductances are set as r, the resistance bones are set as r, and current detection resistors 15a and 15b are connected in parallel.
When the resistance value of R2τ (time constant) = is applied, and a pulse R+r width Δt is applied from the AC drive circuit 7, the voltage Er(t) of the current detection resistors 15a and 15b is equal to the voltage E of the detection coils 3a and 3b. , (t) is the resistance value smoothed voltage V,
, is the smoothed voltage on the coil side. Therefore, by measuring the voltage of either the detection coils 3a, 3b or the current detection resistors 15a', 15b, it is possible to detect the inductance L corresponding to the applied torque.

In the third embodiment described above, the magnetic layer 2a.

The magnetic permeability is set to the maximum state in a state of no external stress so that the sensitive area of 2b is either tensile stress or compressive stress, and each detection coil 3a, 3b is connected in parallel to the AC drive circuit 7. Connected, output V0utl in normal state.

■. Only one of the outputs of ut2 changes, and two outputs change at the same time, so that the magnetic layer 2a.

It is possible to detect missing portions of 2b and abnormalities in the circuit.

In addition, in the third embodiment shown in FIG. 12, by adding synchronous detection circuits 8c, 8d, differential amplifier circuits 13a13b, etc., the accuracy can be doubled as in the second embodiment shown in FIG. The effect of this can be obtained. Further, the magnetic layers 2a and 2b having set magnetic properties as in the third embodiment may be used in the first and second embodiments.

[Effects of the Invention] As described above, according to the present invention, since two distortion detection signals are obtained, an abnormality in the detection circuit can be detected by comparing these two outputs.

Further, according to the present invention, the magnetic permeability of the magnetic layer is maximized in the initial state, and since the magnetic permeability changes only in the decreasing direction, only one output of the detection coil changes, and these outputs are independent of each other. Since the two strain output forces are obtained at the same time, abnormalities in the magnetic layer or the detection circuit can be detected.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a first embodiment of the inventive device, FIGS. 2 and 7 are block diagrams of a conventional device, and FIGS. 3 and 4 are circuit diagrams and operating waveform diagrams of an AC drive circuit. Fig. 5 is a circuit diagram of a synchronous detection circuit, Fig. 6 is an operating waveform diagram of a conventional synchronous detection circuit, Fig. 8 is an operating waveform diagram of the conventional device shown in Fig. 7, and Figs. 9 and 10 are An operating waveform diagram and an output characteristic diagram according to the first embodiment of this invention device, FIGS. 11 and 12 are configuration diagrams according to second and third embodiments of this invention device,
FIG. 13 is a magnetic characteristic diagram of the magnetic layer according to the third embodiment of the present invention, FIG. 14 is a magnetic permeability characteristic diagram of the magnetic layer according to the third embodiment of the present invention, and FIG. 15 is a diagram of the magnetic permeability characteristic of the magnetic layer according to the third embodiment of the present invention. 3 is an output characteristic diagram according to Example 3. FIG. l...Passive axis, 2a, 2b...Magnetic layer, 3a 3
b...Detection coil, 7...AC drive circuit, 8a-8
d... Synchronous detection circuit, 9a, 9b... Smoothing amplifier circuit, 13a, 13b... Differential amplifier circuit. Note that the same reference numerals in the figures indicate the same or equivalent parts. Agent Masu Oiwa Omachi Figure 3 Figure 4 Figure 6 Figure 5 Figure 8 o13 〉 C~ Figure 13 Heisei

Claims (2)

[Claims] (1) A passive shaft to which an external force is applied, first and second magnetic layers that are mounted on the passive shaft and whose magnetic permeability changes due to strain, and windings around the first and second magnetic layers, respectively. an AC drive circuit that applies an AC voltage to the series-connected bodies of the first and second detection coils;
first and second synchronous detection circuits that synchronously detect the outputs of the detection coils using first and second synchronous detection signals synchronized with the positive direction and negative direction drive timings of the AC drive circuit, respectively; A distortion detection device comprising first and second smoothing amplifier circuits that respectively smooth and amplify the outputs of the synchronous detection circuits. (2) A passive shaft to which an external force is applied, and first and second magnetic layers mounted on the passive shaft, whose magnetic permeability changes due to strain, and whose magnetic permeability is set to a maximum state in the absence of external stress. , first and second detection coils wound around the first and second magnetic layers, respectively, an AC drive circuit that applies an AC voltage to the parallel connection of each detection coil, and an AC drive circuit that applies an AC voltage to the parallel connection of each detection coil. First and second synchronous detection circuits that synchronously detect the output using first and second synchronous detection signals synchronized with the positive direction and negative direction drive timings of the AC drive circuit, respectively; and the first and second synchronous detection circuits. 1. A distortion detection device comprising first and second smoothing amplifier circuits that respectively smooth and amplify the outputs of the distortion detector.