JPH04116434A - Torque detecting circuit - Google Patents

Abstract

PURPOSE:To improve the measuring accuracy by providing a torque detecting part which outputs a corresponding signal when receiving signals both from a detecting coil to which an object to be measured is attached and from a torque measuring signal source, and an outputting means for outputting a predetermined phase shifted signal when receiving the latter signal. CONSTITUTION:The size of the torque impressed on a shaft 1 to be measured is detected by a detecting coil 4a. A corresponding signal is output from a torque detecting part 7. At this time, even when the output signal of the detecting part 7 includes errors due to the mechanical wear of the shaft 1 or the temperature change of the shaft 1 and the coil 4a, a phase shifting signal means 8 reduces the error signal remarkably with use of a phase signal the phase of which is shifted by the angle of the phase shift of the error signal to a torque measuring signal. Accordingly, the measuring accuracy is improved.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention is used to detect the torque applied to a shaft used as a spindle of a machine tool, an electric motor, or a rotating shaft of a construction machine. The present invention relates to a torque detection circuit.

[Conventional technology]

As shown in FIG. 10, two detection coils 3 are configured to generate output signals having mutually different correlations with respect to the torque applied to the shaft 3o to be measured.

32 is attached, and the output signals of each detection coil 3L 32 are rectified and then subtracted from each other in the subtraction circuit 34, thereby obtaining a signal corresponding to the magnitude of the torque as the output signal of the subtraction circuit. There is a torque detection circuit that does this.

[Problem to be solved by the invention]

In this conventional torque detection circuit, if there is mechanical play in the axis to be measured or if there is a temperature change in the α1 constant axis to be measured or the detection coil, the error signal due to these is included in the output signal of the above-mentioned subtraction circuit. Therefore, there was a problem that the detection accuracy of the torque value decreased.

The present invention has been made in order to solve the above-mentioned problems and technical problems of the prior art, and makes it possible to reduce the error signal to an alarming level by using the phase difference between the torque corresponding signal and the error signal. Therefore, it is an object of the present invention to provide a torque detection circuit that can improve the accuracy of measuring the magnitude of torque.

[Means to solve problems]

In order to achieve the above object, the torque detection circuit of the present invention includes a signal source that outputs an AC signal for torque measurement, and a signal source attached to the shaft to be measured so as to detect the magnitude of the torque applied to the shaft to be measured. a detection coil installed, receiving a signal from the shaft to be measured through the detection coil and from the signal source.

a torque detection unit that receives the AC signal and outputs a signal corresponding to the signal received through the detection coil L; and a torque detection unit that receives the AC signal from the signal source and outputs a signal corresponding to the signal received through the detection coil L; and phase shifting means for outputting a phase shifted signal.

[Effect]

When a torque is applied to the shaft to be measured, the torque detection section outputs a signal corresponding to the magnitude of the I/Lux. In this case, the covered a
If there is a play in one fixed axis or a change in the temperature of the shaft to be measured or the temperature of the detection coil, the output signal of the torque detecting section will not include an error signal due to this. On the other hand, in the above case, the phase shift means outputs a phase shift signal whose phase is shifted by an angle corresponding to the phase shift of the error signal with respect to the AC signal for torque detection. By phase-detecting the output signal of the torque detection section using the phase-shifted signal, a highly accurate torque-corresponding signal with the error signal removed can be obtained.

〔Example〕

The drawings showing the embodiments of the present application will be described below.

In FIG. 1, J indicates a shaft to be measured made of magnetic metal or the like. This shaft is a No. 1 shaft provided in each machine for the above-mentioned uses, or is shipped from a metal material manufacturer for use in those uses, or is manufactured for use in those uses. There are shafts and the like that are used as test pieces to inspect the characteristics of the shaft. 2 indicates a magnetically anisotropic portion formed on the circumferential surface of a part of the shaft 1 to be measured. This magnetically anisotropic part 2 has a striped part 3 spirally formed on the surface of the shaft 1, and when a torque is applied to this shaft to be measured, the magnetic properties change more than other parts. The striped portions 3 have magnetic properties such as magnetic permeability and magnetostriction that are different from the surrounding surfaces. The inclination of the striped portion 3 with respect to the axis of the shaft 1 is preferably 45 degrees.When the shaft 1 is made of steel, the striped portion 3 as shown in 6I- It is formed by locally changing the structure of the shaft 1 through heat treatment, carburizing, or nitriding, or
If the shaft 1 is made of steel or plastic deck, it may be formed by pasting a ribbon (high magnetostrictive material) with a higher magnetic permeability than the shaft 1 on the surface of the shaft 1, or a recess or groove may be formed on the surface of the shaft 1. It is formed by providing a convex portion. Next, 4a,
Reference numeral 4b denotes a cylindrical detection coil disposed around the region 2, which is used to detect changes in the magnetic properties of the axis to be measured, as is well known.

Next, in FIG. 2 showing the torque detection circuit, 6 is a signal source which outputs an alternating current signal for torque measurement.

The frequency of the above AC signal is, for example, 10 K tl z ~
Values within the frequency range of 200 K tl z culmosity are preferred. 7 is a torque detection section, which includes the detection coils 4a and 4b.
The device is equipped with an AC signal from the signal source 6 and generates an output signal corresponding to a magnetic change in the axis to be measured. Reference numeral 8 denotes a phase shifter as an example of phase shifting means, which receives the alternating current signal from the signal source and outputs a phase shifted signal whose phase is shifted by a predetermined angle with respect to the alternating current signal. be. The angle is predetermined in accordance with the phase shift of the error signal described later with respect to the AC signal, and the angle can be finely adjusted within a range of, for example, about ±10°. Reference numeral 9 denotes a phase detector exemplified as a detection means, which receives the output signal from the torque detector 7 and the phase shift signal from the phase shifter 8, performs phase detection on the former using the latter, and outputs the detected signal. This is how it was done. Next, the torque detection section 7 will be explained. 10 is a bridge circuit, and the detection coils 4a, 4
b is connected to a bridge together with bridge resistors 10a and 10b. 11 is a well-known differential amplifier circuit,
Differential amplifier 12, input resistance 13.14, feedback resistance 15,
It consists of a grounding resistor 16, etc., and a bridge circuit 10.
It is designed to differentially amplify the signals from the Reference numeral 18 denotes a normal amplifier circuit, which includes an amplifier 19, an input resistor 20, a feedback resistor 21, a ground resistor 22, and the like.

Next, the operation of the torque detection circuit having the above configuration will be explained based on the waveform diagram shown in FIG. When the signal source 6 outputs an alternating current signal as shown in a, the signal is applied to the detection coils 4a and 4b of the torque detection section 7, and the magnetic flux caused by them is applied to the shaft 1 to be measured. When twisting torque is applied to the shaft 1 to be measured in this state, the magnetic properties of each magnetically anisotropic portion 22 to which each coil 4a, 4b is attached changes. The torque detection section 7 receives the change through detection coils 4a and 4b. That is, the voltage across each of the detection coils 4a, 4b changes due to the change in the magnetic properties. In this case, if the measured shaft 1 has mechanical play in the axial or radial direction, the positional relationship between the measured shaft 1 and each of the detection coils 4a, 4b changes. If such a change occurs, the voltage appearing at both ends of each detection coil 4a, 4b will include an error due to a change in their positional relationship.

Changes in voltage appearing at both ends of the detection coils 4a and 4b are output as output signals of the bridge circuit 10, sequentially amplified by the differential amplifier circuit 11 and the amplifier circuit 18, and output from the output terminals 7a to 7b of the torque detection section 7. It is output as an output signal as shown. This signal includes a torque corresponding signal C corresponding to the magnitude of the torque and an error signal d corresponding to the error. There is a phase difference, for example 90°, between the torque corresponding signal C and the error signal d, which is indicated by δ. Note that even if the temperature of the shaft 1 to be measured changes and its magnetic properties change, or the temperature of the detection coils 4a and 4b changes and their characteristics fluctuate, the output terminal of the torque detection section 7 7a similarly includes an error signal.

On the other hand, in the above case, the phase shifter 8 outputs a phase shift signal as shown in e. This phase-shifted signal e is the above-mentioned AC signal a.
The phase shift α (for example, 135°) of the error signal d with respect to
This is a signal whose phase is shifted from the AC signal a by an angle corresponding to . In this example, as is clear from the comparison between d and e, both the positive state and the negative state of the phase shift signal e are states that equally extend before and after the O-cross point of the error signal d, respectively. It is a rectangular wave signal whose phase is shifted by an angle of . The angle of the deviation varies depending on the frequency of the AC signal, the material of the shaft 1 to be measured, the characteristics of the magnetically anisotropic portion 2, the number of turns of the detection coils 4a, 4b, etc., and is therefore preferably determined experimentally. That is, after those conditions are determined, the phase difference between the torque corresponding signal C and the error signal d is determined by the same method as in the embodiment shown in FIG. It is preferable to find the angle at which the error signal can be suppressed to the greatest extent from the obtained values.

The output signal S of the torque detector 7 and the phase shift signal e from the phase shifter 8 as described above are input to the detector 9.

In the detector 9, the torque corresponding signal C among the output signals of the torque detecting section 7 is phase-detected to become a signal as shown in f, and this signal is further integrated to become a signal as shown in g. This is a torque-compatible signal. On the other hand, the above error signal d undergoes phase detection to become a signal with the waveform shown in h, and when this signal is further integrated, the signal part shown in i becomes a signal with almost O. . As a result, the detector 9 outputs only the torque corresponding signal indicated by g.

Next, FIG. 4 shows the results of measuring the degree of error caused by mechanical play in the shaft 1 to be measured. The horizontal axis shows the frequency of the AC signal, and the vertical axis shows the error due to mechanical play. In the figure, A shows the degree of error of the torque detection circuit that performs phase detection using the phase-shifted signal as described above, and B shows the degree of error of the torque detection circuit that uses the subtraction circuit as in the prior art. This indicates the degree of error in the detection circuit. As is clear from this figure, the error can be extremely reduced in the torque detection circuit using the phase shift signal. Furthermore, errors due to mechanical play can be reduced over a wide frequency range of AC signals. In order to keep the error within 1%, the frequency of the AC signal must be 10 to 200 K II
A value of about z is preferable.

Next, the operation of removing the error signal from the output signal of the torque detection section 7 using the phase shift signal may be performed by a signal processing means using, for example, a combination detector instead of the detector.

In the above embodiment, an example is shown in which the torque detection section 7 includes two detection coils, but the torque detection section may include only one detection coil or three or more detection coils. In addition to the above-mentioned detection coil, the torque detection section is equipped with an excitation coil, and the shaft to be measured is excited by passing an alternating current signal from a signal source through the excitation coil, and the detection coil is connected to the excited target. It may also be possible to detect only magnetic changes in the measurement axis.

Next, different embodiments will be described. In place of the phase shifter 8, the phase shift means in the torque detection circuit shown in FIG. A signal generator that outputs a pulsed gate signal as shown in FIG. A gate circuit that passes the signal (see b in FIG. 5) and integrates it may also be used. In the torque detection circuit using these signal generators and gate circuits,
The error signal is removed as shown in the waveform diagram in the figure. That is, in FIG. 5, l bl cl dl
Similarly to the embodiments described above, denotes an alternating current signal, an output signal of the torque detection section 7, a torque corresponding signal, and an error signal, respectively. By performing the above operation in the gate circuit which is the detection means, the torque corresponding signal passing through the gate circuit becomes f
A waveform as shown in ゛ is obtained, and by integrating this, a torque corresponding signal as shown in l is obtained.

On the other hand, the error signal passing through the gate circuit becomes a waveform as shown in h', and when this is integrated, the error signal becomes a signal of almost 0 as shown in i'.Therefore, from the gate circuit, g' Only the torque corresponding signals shown in are output.

Next, FIG. 6 showing a further different embodiment of the present application will be described. In the figure, 25 is a phase divider which receives an AC signal from a signal source 6e and is synchronized with the AC signal, respectively.
In addition, a first phase-shifted signal and a second phase-shifted signal whose phases are different from each other by 90° are output. In this example, the first
A 0° signal having the same phase as the alternating current signal indicated by - is output as a phase shift signal, and a 90° signal shifted by 90° from the 0° signal is output as a second phase shift signal. 26.27
2 represents a well-known phase detector, and 28 represents a phase rotation circuit.

In such a circuit, the phase detection of the output signal from the torque detector 7e is performed in the detector 26 using the 0° multiplied signal from the phase divider 25, and the phase detection of the output signal from the torque detector 7e is performed in the detector 27 using the 90" signal. When the output signals from these detectors 2627 are plotted, for example, with the output signal of the detector 26 on the horizontal axis and the output signal of the detector 27 on the yi axis, as shown in FIG. 7(A). In other words, since the torque corresponding signal and the error signal are out of phase with each other as is clear from the comparison between c and d in Fig. 3, the torque corresponding signal is shown in Fig. 7 (8). The error signal appears as shown by C, and the error signal appears as shown by d.These detectors 2
The output signal of 627 is phase rotated in the phase rotation circuit 28 so that the error signal d substantially overlaps the vertical axis, that is, the horizontal axis component of the error signal is as small as possible, as shown in FIG. 7(B). , In this state, the horizontal axis component is extracted as an output signal. Therefore, the output signal of the phase rotation circuit 28 becomes a highly accurate torque-corresponding signal that contains almost no error signal, as shown by C''.

It should be noted that parts that are functionally the same or equivalent to those in the previous figure are given the same reference numerals as in the previous figure with an alpha bent e, and redundant explanations are omitted.

Next, FIG. 8 shows the torque corresponding signal C in the circuit of FIG. 6 when the frequency of the AC signal from the signal source 6e is different.
This shows the relationship between the error signal d and the error signal d. Even in the case of such a relationship, by performing phase rotation so that the error signal d substantially overlaps the vertical axis as in the case described above, it is possible to obtain a torque-corresponding signal in which the error signal is largely removed. However, as is clear from the explanation regarding FIG. 7(B), the angle of intersection between the torque corresponding signal and the error signal (
The closer the phase difference) is to 90°, the more the torque corresponding signal (signal indicated by C'') obtained as the output signal of the phase rotation circuit 28.
The level of is high. Therefore, it is preferable to select the frequency of the AC signal to achieve such a state.

Next, FIG. 9 shows how error signals due to temperature changes are removed in the circuit of FIG. 6. In FIG. 9(A), C is a torque corresponding signal, and d' is an error signal due to temperature change, respectively, as in the case of FIG. 7(A). Even in such a case, the outputs of the detectors 26 and 27 are subjected to phase rotation in the phase rotation circuit 28 so that the component in the horizontal axis direction of the error signal d" is minimized as shown in FIG. 9(B). By doing so, it is possible to obtain a highly accurate torque-corresponding signal with a large amount of error removed.

〔Effect of the invention〕

As described above, in the present invention, when torque is applied to the shaft 1 to be measured, the magnitude of the torque is detected by the detection coil 4a.
is detected, and a signal corresponding to the magnitude of the torque is output from the torque detection section 7, so it goes without saying that the magnitude of the torque applied to the shaft 1 to be measured can be determined from the output signal. In the above case, there may be mechanical rattling in the shaft 1 to be measured or temperature changes in the shaft 1 to be measured or the detection coil 4a, and errors caused by these may occur in the detection coil 4.
Even if the error signal d input through the torque sensor a and corresponding to those errors is included in the output signal of the torque detection section 7, it corresponds to the phase shift α of the error signal d with respect to the AC signal a for torque measurement. Since the phase shift means 8 outputs a phase-shifted signal e whose phase is shifted from the AC signal a by an angle equal to the angle, the torque-corresponding signal in the output signal can be changed by using the phase-shifted signal e. By using the phase difference δ between C and the error signal d, the error signal d can be significantly reduced, which has the effect of increasing the measurement accuracy of the torque magnitude.

[Brief explanation of drawings]

The drawings show examples of the present application; Fig. 1 is a diagram schematically showing the relationship between the axis to be measured and the detection coil, Fig. 2 is a circuit diagram of the torque detection circuit, and Fig. 3 is a waveform diagram for explaining operation. , Fig. 4 is a graph showing frequency characteristics and phase detection characteristics of errors due to mechanical play of the measured axis, Fig. 5 is a waveform diagram for explaining the operation of different embodiments, and Fig. 6 is a graph showing different implementations of the torque detection circuit. Circuit diagrams showing examples, Figures 7 (^) and (B) are diagrams explaining the operation of the torque detection circuit in Figure 6, and Figure 8 is different from Figure 7 (8) in that the frequency of the AC signal for torque measurement is A diagram showing the relationship between the torque corresponding signal and the error signal in different cases, FIG. 9(A) (
B) is an explanatory diagram of the operation when the error signal is an error signal due to temperature change. FIG. 10 is a circuit diagram of a conventional torque detection circuit. 1... Axis to be measured, 4a, 4b... Detection coil, 6
. . . signal source, 7 . . . torque detection unit, 8 . . . phase shift means, 9 . . . detection means.寞寞g臺面2蕩子× （△） Fig. Fig.(B) Fig.

Claims (1)

[Claims] 1. A signal source that outputs an alternating current signal for torque measurement, and a detection coil attached to the shaft to be measured so as to detect the magnitude of the torque applied to the shaft to be measured, a torque detection unit that receives a signal from the shaft to be measured through the detection coil, receives the AC signal from the signal source, and outputs a signal corresponding to the signal received through the detection coil;
A torque detection circuit comprising: a phase shifting means for receiving the alternating current signal from the signal source and outputting a phase shifted signal whose phase is shifted by a predetermined angle with respect to the alternating current signal. 2. The torque detection circuit according to claim 1, further comprising detection means for receiving the output signal from the torque detection section and the phase shift signal from the phase shift means, detecting the phase of the former using the latter, and outputting the detected signal. . 3. It is equipped with a signal source that outputs an AC signal for torque measurement, and a detection coil attached to the shaft to be measured so as to detect the magnitude of the torque applied to the shaft to be measured. a torque detection section that receives a signal through the detection coil, receives the AC signal from the signal source, and outputs a signal corresponding to the signal received through the detection coil;
a phase divider that receives the alternating current signal from the signal source and outputs first and second phase-shifted signals that are synchronized with the alternating current signal and have a phase difference of 90 degrees from each other; a first detector that receives an output signal and a first phase shift signal from the phase divider, performs phase detection on the former using the latter, and outputs the detected signal; and an output signal from the torque detector and the A torque detection circuit comprising: a second detector that receives a second phase shift signal from a phase divider, performs phase detection on the former using the latter, and outputs a detected signal.