JPH03237328A - Torque detector - Google Patents

Abstract

PURPOSE:To speed up the response, to suppress the pulsation, and to enhance the torque detection performance by detecting a potential difference corresponding to a magnetostrictive component passing through a shaft to be measured, and detecting the loading ratio of torque and determining holding timing. CONSTITUTION:The shaft 3 to be measured has a magnetic coil 7 outside so that a magnetic circuit is formed as a part of a magnetic path, and the magnetostrictive component passing, through the shaft 3 is detected to detect torque applied to the shaft 3. At this time, a potential difference detecting means 13 detects the potential difference value corresponding to the magnetostrictive component and a sample-holding means 25 holds the potential difference value at specific timing. A detecting means 37, on the other hand, detects the loading ratio of the torque, a phase imparting means 55 imparts the specific timing to a phase corresponding to the signal from the detecting means 37 to output the value from the holding means 25, and then the torque applied to the shaft 3 is detected.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a torque detection device that detects torque using magnetostriction, and in particular has a fast response, suppresses pulsation, and detects torque. The present invention relates to a torque detection device that can obtain a stable output even when the torque varies.

(Prior Art) Examples of conventional magnetostrictive torque detection devices include those shown in FIGS. 10 and 11 (similar publicly known examples include Japanese Patent Laid-Open No. 1-213533).

The torque pickup section 101 of the torque detection device shown in FIG.
03, and on the surface of the shaft to be measured 103, concave portions 105a, 105b and convex portions 107a, 107b forming a predetermined angle with respect to the axial direction of the shaft to be measured 103 are formed. These concave portions 105a and 105b and convex portions 107a and 1107b provide shape magnetic anisotropy.

Then, the torque pickup section 101 operates on the shaft 1 to be measured.
03, one concave portion 105a and convex portion 107a formed on the measured shaft 103, and the other concave portion 105.
The coil 1 has a pair of coils 109a and 109b arranged opposite to each other and the convex portion 107b.
It has a structure in which a cylindrical yoke 113 made of a high magnetic permeability material is provided on the outside of 09a and 109b with a gap 111 between it and the shaft 103 to be measured.

In order to extract the value detected by the torque pickup section 101 having such a structure, as shown in FIG.
Coils 109a and 109b and resistors 115 and 117 are combined to form a bridge circuit, and this bridge circuit is provided with a variable resistor 119 for balance, and an excitation oscillator 121 is provided between connection points A and C of the bridge circuit. A differential amplifier 123 is connected between connection points B and D, and its output 125 is connected to a synchronous (synchronized by the excitation oscillator 121) detector 127. After half-wave rectification of the differential outputs of B and D, the smoother 12
9 converts it into a direct current, and the detection output can be taken out through output terminals 131 and 133.

Next, the torque detection device shown in FIG.
The operation when connected to the electric circuit shown in the figure will be explained.

First, during operation, the excitation oscillator 121 supplies the coils 109a and 109b with a constant amplitude (V) and frequency (
f) energize the alternating current. By this energization, the axis to be measured 1
03-Gap 1] 1-Yoke 113-Gap 111-Measurement axis 103 is the magnetic line of force that connects the coils 109a, 10
It occurs to surround 9b.

By the way, if the frequency (f) of the alternating current is increased,
Eddy current increases in the shaft 103 to be measured.

The distribution of eddy current is stronger closer to the center of the axis to be measured 103, and smaller at the surface. Therefore, even if the magnetic field at the surface can follow changes in the external magnetic field, changes in magnetization at the inside are blocked.

Therefore, the magnetic lines of force flow along the surface of the shaft 103 to be measured, and the shaft 103 to be measured has a concave portion 105g.

105b is formed to form a predetermined angle with the axial direction of the shaft to be measured 103, so this becomes magnetic resistance and flows mainly through the convex portions 107a and 107b. Therefore, the shape magnetic anisotropy effect due to the concave portions 105a, 105b and the convex portions 107a, 107b appears.

The concave portions 105a, 105b and the convex portion 107a,
The angle of 107b with respect to the axial direction is - Generally speaking, the angle between concave portion 105a and convex portion 107a on one side and concave portion 1 on the other side is
05b and the convex portion 107b are in opposite directions and at equal angles, but the most desirable direction is the principal stress direction when torque is applied to the shaft to be measured 103, that is, the right 4
5'' direction and left 45@ direction.The reason for this is that the magnetic lines of force mainly flow in the principal stress direction, and the convex portions 107a and 107b are the outermost surface portions of the shaft 103 to be measured. This is because this is the place where the strain is the largest, and the change in magnetic permeability of the magnetic material due to this strain can be brought out most effectively.

When a torque is applied to the shaft to be measured 103 in the T direction shown in FIG.
Since the convex portion 107b is formed in the 5° direction, the maximum tensile stress +δ acts on it, and on the other hand, since the other convex portion 107b is formed 45″ to the left, the maximum compressive stress ~δ acts on it.

Here, if the shaft to be measured 103 has a positive magnetostrictive effect, the magnetic permeability of one convex portion 107a increases compared to when the torque is zero, and conversely, the permeability of the other convex portion 107b increases. The magnetic flux decreases compared to when the torque is zero.

Therefore, the inductance of one coil 109a increases and the inductance of the other coil 109b decreases, causing the bridge circuit shown in FIG. 11 to become unbalanced, and an output corresponding to the torque is generated between output terminals 131 and 133.

Furthermore, when torque is applied in the opposite direction, the inductance of one coil 109a decreases and the inductance of the other coil 109b increases due to the opposite effect to that described above, so that the bridge circuit of FIG. The balance is disrupted, and an output corresponding to the torque is generated between the output terminals 131 and 133.

More specifically, the coil 109a.

When the inductance of 109b is L2, the resistance value of resistor 115 and 117 is R, the voltage of the excitation oscillator 121 is V, and the frequency is f, the current flowing through the bridge circuit A-B-C is 11 % circuit A-D-C
If the current flowing through is 12, it becomes ■, and the potential at point B is V+-i+ ・The potential at point RD is V2
becomes V2-i2 ・R.

Therefore, the potential difference between points B and D is lV+ That is, 2 This is expressed by the differential amplifier 123.

Furthermore, a synchronous detector 127 determines whether the torque T is in the forward or reverse direction.
Through this, a smoother 129 extracts positive and negative outputs corresponding to the positive and negative torques.

(Problem to be Solved by the Invention) By the way, such conventional torque detection devices output AC power proportional to torque and are smoothed before being extracted. It takes some time to do this, and it is difficult to increase the speed, and when the speed is increased, pulsating currents remain, making accurate detection impossible. Also, since synchronous detection is performed as described above, the output is V rl −eO
There was a problem that the filter output was 8θ (7 m is the peak value), and the so-called "sharpness" was poor.

Therefore, the applicant of the present application has developed a system that can suppress pulsating flow with high response speed.
We previously proposed a torque detection device that does not fluctuate in output due to changes in the environment.

This is, for example, as shown in FIGS. 5 and 6.

FIG. 6 shows an electrical circuit diagram of this torque detection device, which outputs the torque detected by the torque pickup section 1 shown in FIG. The torque pickup section 1 shown in FIG. 5 has concave portions 4a, 4b and convex portions 5a, 5b formed on the surface of a shaft 3 to be measured, and a magnetic coil 7 on the outer periphery thereof.
A s 7 b is provided, and a cylindrical yoke 11 is further provided on the outside thereof with a gap 9 between it and the shaft 3 to be measured. The windings of the coils 7a and 7b are connected in such a way that the magnetic fields of one coil 7a and the other coil 7b are in the same direction, sharing the excitation magnetic field and increasing the output sensitivity. I'm trying to be able to do that.

An electric circuit for extracting the value detected by the torque pickup section 1 is shown in FIG. As a potential difference detection means 13 for detecting a potential difference corresponding to the magnetostrictive component detected by the torque pickup section 1, a bridge circuit is constructed by introducing a coil 7a17b and a 50Ω resistor 15.17. The variable resistor 19 is provided for balancing the bridge circuit, and
A 30 kHz excitation oscillator 21 is connected between connection points A and C of the bridge circuit, and the oscillator 21 is excited by the AC voltage.
A differential amplifier 23 is connected between connection points B and D. As a result, the voltage at point B due to the voltage applied between ASC
1 and the voltage V2 at point D so that the difference ΔV is output between the BSDs and amplified. Further, the potential difference detection means 13
A semiconductor switch 27 for sampling and a sample hold device 29 are provided as a sample hold section 25 for sampling and holding the potential difference value from the sample and hold device 29 at a predetermined timing, and terminals 31 and 33 for taking out the output of the sample hold device 29 are provided. In addition, a phase shifter 35 is provided to create the sampling timing of the two sample-and-hold devices. Furthermore, a control unit 3 for controlling sampling.
6, a buffer amplifier 39, a zero-cross comparator 41, a window comparator 43, and one-shot multivibrators 45 and 47 as timers for setting sample times are provided.

Then, the 30kHz AC voltage (Fig. 7a) oscillated from the oscillator 21 is input between A1C of the bridge circuit, excites the coil 7a%7b, and produces an output △ corresponding to the torque between B and 0. V is obtained. This output ΔV is amplified by the differential amplifier 23 and input in the form of torque to the next sample and hold section 25 (FIG. 7b). This input terminal is divided into a semiconductor switch 27 and a buffer amplifier 39. The buffer amplifier 39 outputs the torque signal t as it is, and inputs it to the zero cross comparator 41. The zero cross comparator 41 compares the torque signal t and O volts, and if the torque signal t is greater than O volts, the zero cross comparator 41
Outputs 4 volts, and +14 volts in the opposite case (7th
Figure C). The output of the zero cross comparator 41 is then input to the window comparator 43. The window comparator 43 outputs 0 volts when the output of the zero cross comparator 41 is included in the window width (portion α between the dashed lines of the zero cross comparator output in FIG. 7C), and outputs +5 volts otherwise. Output (7th
Figure d). The output of the window comparator 43 has a time constant T1
One-shot multi-by-break 45 with -5μs
is man-powered. Then, the one-shot multivibrator 45 is triggered by the falling edge of the window comparator 43, and +5 volts is output for a time constant T1 time (FIG. 7e). One shot multi vibrator 45
The output of is input to the one-shot multi-vibrator 47 having a time constant T2-4 μs, and the multi-vibrator 47 is connected to the one-shot multi-vibrator 4.
Triggered by the falling edge of 5, the time constant T2 time +
5 volts are output (Figure 7f).

In this way, the output of the one-shot multivibrator 47 is input to the control side terminal of the semiconductor switch 27, and the semiconductor switch 27 is turned on for T2 - 4 μs, which is the output of the seven-shot multivibrator 47, and only during that time is the differential The value of the torque signal t, which is the output of the amplifier 23, is input to the sample-and-hold device 29 (FIG. 7g). On the other hand, the phase shifter 35 generates a sample and hold signal based on the signal from the oscillator 21. That is, oscillator 2
1 output, a pulse signal is output at a timing with a predetermined phase and is used as a sample hold signal (7th
Figure h). According to this timing, the two sample and hold devices output the peak value of the torque signal t that has passed through the semiconductor switch 27 to the terminal 31 as a sample and hold output.
．． 33 (Fig. 7g).

However, in such a torque detection device,
Subsequent research revealed that the phase of the torque t output (FIG. 7b) with respect to the output of the oscillator 21 (FIG. 7a) is not always constant. That is, as shown in FIG. 8, the phase is constant for torques of ±25% or more of the rated torque, but the phase of the torque changes in other cases.

FIGS. 9(a) to 9(d) show waveforms when torque is applied from 0 to 30% (the reference is the output of the oscillator). Note that the phase is not changed when the torque is 30% or more, so it is omitted.

Therefore, in order to perform more reliable torque detection, there is a problem in detecting at a constant torque phase.

Therefore, an object of the present invention is to provide a torque detection device that is further improved and can further improve torque detection performance.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention includes a shaft to be measured 3 and a shaft to be measured 3 as part of a magnetic path, as shown in FIG. In a torque detection device that has a magnetic coil 7 forming a magnetic circuit and detects a torque applied to the shaft 3 to be measured by detecting a magnetostrictive component passing through the shaft 3 to be measured, a potential difference according to the magnetostrictive component is provided. Potential difference detection means 13 for detecting
, a sample hold means 25 for sampling and holding the potential difference value at a predetermined timing, a detecting means 37 for detecting the torque load ratio, and a phase according to the signal from the detecting means 37 at the predetermined timing. The configuration includes a phase imparting means 55 for imparting the phase.

(Function) The shaft to be measured 3 has a magnetic coil 7 outside thereof so as to form a magnetic circuit with the shaft to be measured 3 as part of the magnetic path, and detects the magnetostrictive component passing through the shaft to be measured 3. As a result, a torque detection device for detecting the torque applied to the shaft 3 to be measured is formed.

Then, the potential difference detection means 13 detects a potential difference value corresponding to the magnetostrictive component, and the sample hold means 25 holds the potential difference value at a predetermined timing.

On the other hand, the detection means 37 detects the torque load ratio,
The phase applying means 55 applies a phase corresponding to the signal from the detecting means 37 to the predetermined timing, and outputs from the sample hold means 25 to detect the torque applied to the shaft 3 to be measured.

(Example) Hereinafter, embodiments of the invention will be described based on the drawings.

FIG. 2 shows an electric circuit diagram of a torque detecting device according to an embodiment of the present invention, and similar to the circuit shown in FIG.
It outputs the torque detected by a torque pickup section 1 similar to that shown in the figure. Therefore, the same elements as in FIG. 6 are given the same reference numerals.

As a potential difference detection means 13 for detecting a potential difference corresponding to the magnetostrictive component detected by the torque pickup section 1, a bridge circuit is constructed by combining the coils 7g and 7b and 50Ω resistors 15 and 17, and the variable resistor 1 One is provided for balancing the bridge circuit, and a 30kHz excitation oscillator 21 is installed between connection points A and C of the bridge circuit.
connected and excited by the AC voltage, connecting points B and D
A differential amplifier 23 is connected between them. As a result, A, C
The difference ΔV between the voltage V1 at point B and the voltage v2 at point D due to the voltage applied between them is outputted between the BSDs and amplified. Further, as a sample and hold means 25 that samples and holds the potential difference value from the potential difference detection means 13 at a predetermined timing, two sample and hold devices for sampling, a semiconductor switch 51 that controls the output of the two sample and hold devices, and Terminals 31 and 33 from which the output is taken out are provided, and a phase shifter 35 is also provided to create the sampling timing of the sample and hold device 29. Further, as a detection means 37 for detecting the torque load ratio, a zero cross comparator 41, a window comparator 43, and one-shot multivibrators 45, 45', 4 as timers for setting a sample time are used.
7.47'' and a semiconductor switch 49, and a window comparator 53 that further controls the semiconductor switch 49.
has been established. Further, a D-type flip-flop 57 is provided as a phase imparting means 55 for imparting a phase corresponding to the signal from the detection means 37 at the predetermined timing, and the semiconductor switch 51 is controlled by the output signal of this D-type flip-flop 57. .

Next, the operation will be explained with reference to FIGS. 2 and 3.

30kHz AC voltage (third
Figure a) is input between bridge circuits A and C, and the coil is 7m long.
7b is excited, and an output ΔV corresponding to the torque is obtained between B and D. This ΔV is amplified by the differential amplifier 23 and input to the sample hold means 25 and the detection means 37 in the form of torque t (FIG. 3b). That is, this input voltage is input to the sample-and-hold device 29 and the zero-cross comparator 41. The zero cross comparator 41 compares the torque signal t with 0 volts, and when the torque signal t is O
If it is larger than volts, use -14 volts, or vice versa.
Outputs 14 volts (Figure 3C). The output of the zero cross comparator 41 is output from the window comparator 4.
Enter 3.

The window comparator 43 outputs 0 volts when the output of the zero cross comparator 41 is included in the window width (portion α between the two-dot chain line of the zero cross comparator output in FIG. 3C), and outputs +5 volts otherwise. Output (Figure 3 d). The output of the window comparator 43 is inputted to a one-shot multivibrator 45 having a time constant T of -7 μs and a one-shot multivibrator 45' having a time constant Tt of −13 μs.

The one-shot multivibrator 45.45'' is triggered by the falling edge of the window comparator 43, and the one-shot multivibrator 45 has a time constant of 71.
Only time and one-shot multivibrator 45'
is the time constant T, +5 volts are output for - time (3rd
Figure e). Funshot Multivibrator 45.45-
The output of is input to a one-shot multivibrator 47.47= with a time constant T2-2μs, and the one-shot multivibrator 47.47'' is triggered by the falling edge of the one-shot multivibrator 45.45', with a time constant of 72 +5 volts are output for the time (3rd
Figure f).

In this way, the output of the one-shot multivibrator 47, 47- as the output of the detection means 37 is input to the selector terminal of the semiconductor switch 49, and the semiconductor switch 49 is connected to the window comparator 53 according to the output of the sample and hold device 29. is 0N-OFFL, its output is Hi
One-shot multivibrator 45- 47-
is selected, and when it is Low, one-shot multivibrator 45.47 is selected.

On the other hand, the phase shifter 35 generates a sample and hold signal based on the signal from the oscillator 21. That is, oscillator 2
1 output, a pulse signal is output at a timing with a predetermined phase, and is used as a sample and hold signal (Fig. 3g). Then, the sample and hold device 29 outputs the peak value of the torque signal t as a sample and hold output to the terminal 3 via the semiconductor switch 51 according to this timing.
1.33 (Figure 3h). semiconductor switch 5
1 is controlled by a D-type flip-flop 57 as a phase imparting means 55, and controls whether to pass the output of the sample-and-hold device 29 as is or to pass 0 volt.

Furthermore, the functions of the main parts in this embodiment will be specifically explained.

As shown in FIG. 3 above, the peak value of the output from the potential difference detection means 13 is sampled and held by two sample and hold devices, and the timing of the sample and hold is created by the oscillator 21, so the peak value of the output from the potential difference detection means 13 is always sampled at a constant timing. will be held.

Incidentally, if the phase of torque is always constant, the timing of sampling and holding may be always constant, but the phase of torque changes.

In order to cope with this change, it is possible to change the timing of sample and hold according to the phase of the torque, but this will deteriorate the linearity of the sensor, so the timing of sample and hold should always be changed. Must be constant.

Therefore, in this embodiment, a semiconductor switch 51 is provided to select whether to output the torque output from the potential difference detection means 13 as is or to set it to 0 volt.

This allows the output of the sample and hold device 29 to be output when torque is applied, and not to output otherwise. The sample-and-hold device 29 samples and holds this output, but at this time, the sample-and-hold device 2
Let the output of 9' be O volts. The selection by the semiconductor switch 51 is performed by the zero cross comparator 41, the window comparator 43, and the one-shot multivibrators 45.45' and 47.47-, which serve as the detection means 37 for detecting the torque load ratio. Here, the one-shot multivibrators are arranged in parallel to correspond to the torque phase.
In this example, two pieces were used to simplify the explanation, but
In reality, a large number of them are arranged in parallel.

In this embodiment, one of the one-shot multivibrators 45" 47- is used for the time constant when the torque is small, and as described above, one of the one-shot multivibrators 45" 47- is used for the time constant when the torque is small.
5'' has a time constant T''-13 μs, and the one-shot multivibrator 47' has a time constant T2-2 μs. The other one-shot multivibrator 45 and 47 are for the time constant when the torque is large, and as mentioned above, the one-shot multivibrator 45 has a time constant Tl-7 μS, and the one-shot multivibrator 47 has a time constant T
It has 2-2 μs. Now consider the case where the torque is small. In this case, the phase characteristic is shown by the broken line in FIG. 3, and the phase changes compared to when the torque is high (shown by the solid line in FIG. 3).

Then, the zero-cross comparator 41 is turned 0N-OFF, aiming at the time when the phase shown by the broken line in FIG. 3 crosses zero.
Repeat (dashed line in Figure 3C).

The window comparator 43 which receives the signal from the zero cross comparator 41 also changes as shown by the broken line in FIG. 3d. The one-shot multivibrator 45' receiving the signal from the window comparator 43 has a time constant TI -1.
It is turned on for 3 μs (Fig. 3e), and after time-up, a one-shot multi-bye break 47' occurs. The one-shot multivibrator 47' has a time constant of T2-2μs.
(Fig. 3 f). Here, looking at the waveform of the sample-and-hold timing shown in FIG. 3g, the sample-and-hold signal is output while the one-shot multivibrator 47' is ON. Based on the relationship between the ON time of the one-shot multivibrator 47' and the sample hold signal of the phase shifter 35, it is determined whether or not torque is applied. That is, the phase changes depending on the magnitude of the torque, but when the torque is constant, the phase is also constant. Therefore, if the phase to be sampled and held is known, the one-shot multi-bye break can be adjusted so that it is ON for only that time.

Next, a D type flip-flop 57 serving as a phase imparting means 55 uses the sample and hold signal shown in FIG. 3g as a clock source, and uses the outputs of the four semiconductor switches as data. That is, the D type flip-flop 57 latches data at the rising edge of the clock, outputs a Hi-fold signal when the outputs of the four semiconductor switches are Hi, and outputs a Low signal when the output of the semiconductor switch 49 is Low. Then, this output signal causes the semiconductor switch 5 to
Control 1.

With the above configuration, measures are taken against fluctuations in the phase of the torque from the potential difference detection means 13 due to temperature rise of the torque pickup section. For example, as shown in FIG. 4, when the temperature of the torque pickup section 1 rises, the torque from the potential difference detection means 13 increases with respect to the output S of the oscillator 21 according to the difference in inductance between the coils 7a and 7b. The phase of changes. In contrast, in this embodiment, as described above, detection is performed only when torque is applied to determine whether the phase change from the potential difference detection means 13 is due to a torque change or a temperature rise. This makes it possible to suppress fluctuations due to temperature.

In addition, since switching noise was generated in the past,
Although it was not possible to reduce the sampling time to 4 μs or less, in this example, the semiconductor switch 51 is provided on the downstream side of the two sample and hold devices that output DC components, so switching noise does not occur, and the sample time can be reduced to 2 μs. Can be set. Further, sample and hold is performed according to changes in the phase of the torque on the low-frequency side. Therefore, the effects shown in Table 1 can be obtained.

Table 1 As shown, compared to the conventional torque detection device, the temperature fluctuation is 1/10th that of the conventional torque detection device. Further, there is an effect that rotational fluctuations are reduced to about 1/2.

[Effects of the Invention] As is clear from the above description, according to the configuration of the present invention, the response is fast, pulsation is suppressed, torque changes can be reliably detected, and torque detection performance is further improved. be able to.

[Brief explanation of drawings]

Fig. 1 is a purchasing diagram of this invention, Fig. 2 is a circuit diagram of a torque detection device according to an embodiment of this invention, Fig. 3 is a time chart based on the circuit of Fig. 2, and Fig. 4 is a temperature change. 5 is a sectional view of a conventional torque pickup section, FIG. 6 is a circuit diagram of the same as above, and FIG. 7 is a time chart based on the circuit of FIG. 6. ,
Fig. 8 is a diagram showing the relationship between rated torque and phase, Fig. 9 is a diagram showing the relationship between torque load ratio and waveform, and Fig. 10 is a cross-sectional view of a torque victor knob according to another conventional example. , 1st
Figure 1 is a circuit diagram of the same as above. 3...Pongee to be measured 7 (7a, 7b)...Magnetic coil 13...Potential difference detection means 25...Sample holding means

Claims (1)

[Claims] It has an axis to be measured and a magnetic coil that forms a magnetic circuit with the axis to be measured as part of a magnetic path, and by detecting a magnetostrictive component passing through the axis to be measured, the torque applied to the axis to be measured can be calculated. A torque detection device for detecting includes a potential difference detection means for detecting a potential difference according to the magnetostrictive component, a sample hold means for sampling and holding the potential difference value at a predetermined timing, and a detection means for detecting a torque load ratio. , and a phase imparting means for imparting a phase corresponding to a signal from the detecting means at the predetermined timing.