JP3094879B2 - Relative displacement detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a relative displacement detecting device, and more particularly, to a detecting device for detecting a displacement of a magnet movably provided along a magnetostriction line.

[0002]

2. Description of the Related Art Conventionally, for example, Japanese Patent Application Laid-Open No. 7-18100
As disclosed in Japanese Unexamined Patent Publication No. 3 (1994), a magnetostrictive line, a magnet movable along the magnetostrictive line, a signal processing unit for supplying a pulse signal to the magnetostrictive line and receiving and processing a distortion signal generated in the magnetostrictive line. There has been known a relative displacement amount detecting device including the above.

That is, when a pulse-like signal is supplied to the magnetostrictive wire from the above-described signal processing unit, a circumferential magnetic field is generated around the magnetostrictive wire along with the flow of the pulse signal. On the other hand, the magnetic field generated by the magnet acts on the magnetostrictive wire in the axial direction. Therefore, when the pulse signal supplied to the magnetostrictive wire flows in the vicinity of the magnet, the magnetic field generated by the magnet and the magnetic field generated by the pulse signal overlap and act on the magnetostrictive wire.

When the superimposed magnetic field acts on the magnetostrictive wire, a torsional distortion is generated in the portion of the magnetostrictive wire by a so-called Biedemann effect, and a distortion signal composed of ultrasonic vibration is generated. This distortion signal is generated at a position near the magnet on the magnetostrictive line, and then propagates toward both ends of the magnetostrictive line at a predetermined propagation speed.

Therefore, in the above-described conventional apparatus, if the time required for the distortion signal to propagate to a predetermined portion on the magnetostriction line after the pulse signal is supplied to the magnetostriction line is detected, the propagation speed of the distortion signal is determined. In this relation, it is possible to calculate the distance between the position where the magnet exists and the position where the distortion signal is detected, and if the distance can be calculated, it is possible to detect the displacement of the magnet.

When such a relative displacement detecting device is used for measuring the vehicle height, it is conceivable to dispose the detecting device in a shock absorber. However, when the damping force of the shock absorber is switched by an electromagnetic actuator. In this case, the magnetic field of the magnetostrictive line is affected by the magnetic field generated by the electromagnetic actuator, and the relative displacement amount, that is, the detection accuracy of the vehicle height value is reduced.

For this reason, the relative displacement amount detection device described in the above publication does not use the propagation time of the distortion signal detected during the operation of the electromagnetic actuator in the calculation of the relative displacement amount, thereby reducing the relative displacement amount detection accuracy. Preventing.

[0008]

However, there is no problem when the electromagnetic actuator is not operated. However, in recent shock absorbers, the switching of the damping force is continuously performed with a small switching width. If all the propagation times during operation are not used, there is a problem that the relative displacement amount, that is, the vehicle height value can hardly be obtained during the operation of the electromagnetic actuator.

Further, the propagation time of the distortion signal is also affected by a magnetic field due to a road heating current for preventing road surface freezing and a magnetic field due to the magnetization of the main body components. The present invention has been made in view of the above points, even when the magnetic information is affected by an external magnetic field, by judging the degree of the influence from the magnetic information, by controlling the adoption of the magnetic information, An object of the present invention is to provide a relative displacement amount detection device that can obtain a highly reliable relative displacement amount.

[0010]

According to a first aspect of the present invention, there is provided a magnetic detection apparatus for detecting magnetic information whose propagation time changes in accordance with a displacement of a relative position between a first member and a second member which are relatively movable. Means, a propagation time detecting means for detecting a propagation time of the magnetic information detected by the magnetic detecting means, and a relative displacement detecting means for calculating a relative displacement between the first member and the second member from the propagation time. in the relative displacement amount detecting apparatus having, when the waveform of the magnetic information is within a predetermined level range
If the detection time is out of the predetermined time range
And a determination unit for prohibiting the propagation time from being employed in the calculation of the relative displacement when the determination is made that there is an abnormality.

Therefore, even when the electromagnetic actuator of the shock absorber is operating, a reliable relative displacement can be calculated from the normal propagation time of magnetic information without being affected by the magnetic field generated by the electromagnetic actuator. Active use of highly reliable magnetic information.

[0012]

[0013]

[0014]

FIG. 1 shows an overall configuration diagram of a relative displacement detecting device according to an embodiment of the present invention. In FIG. 1, a magnetostrictive wire 10 is a linear member made of a magnetostrictive material that generates a strain in accordance with the intensity of a surrounding magnetic field. An annular permanent magnet 12 as a second member is inserted into the magnetostrictive wire 10 as a first member so as to be movable in the axial direction.

An annular coil 26 as a magnetic detecting means is fitted and fixed to a predetermined portion (hereinafter referred to as a detecting portion) 10a of the magnetostrictive wire 10. Permanent magnet 1 of magnetostrictive wire 10
A fixing member 11 is fitted and fixed at a position (hereinafter, referred to as a fixing portion) 10b adjacent to the detecting portion 10a on the opposite side to the position 2. The fixing member 11 functions to reflect the propagation of strain on the magnetostrictive wire 10.

The magnetostrictive wire 10 has one end grounded and the other end connected to the pulse generating circuit 14. The pulse generation circuit 14 is a circuit that supplies a predetermined pulse signal to the magnetostrictive line 10 and the reception circuit 16 at the same timing. The reception circuit 16 receives the pulse signal supplied from the pulse generation circuit 14 and the distortion signal detected by the detection coil 26 in the detection unit 10a of the magnetostriction wire 10 as described later, shapes the waveform, and shapes the waveform. And a circuit to be supplied to the determination circuit 19.

The propagation time detecting circuit 18 serving as a propagation time detecting means receives the pulse signal generated by the pulse generating circuit 14 by the receiving circuit 16 and then detects the magnetostrictive line 10 by the detecting section 10.
a (hereinafter referred to as “propagation time”) required to receive the distortion signal supplied from “a”.
9 is a circuit that outputs the propagation time to the displacement detection circuit 20 when the prohibition signal is not supplied from 9.

A determination circuit 19, which is a determination means, determines whether the distortion signal is deformed under the influence of a magnetic field generated by an electromagnetic actuator or the like of the shock absorber.
If it is deformed, a prohibition signal is supplied to the propagation time detection circuit 18. Then, based on the propagation time detected by the propagation time detection circuit 18, the displacement detection circuit 20, which is a relative displacement detection unit, detects the position of the detection unit 10 a set on the magnetostrictive line 10 and the position where the permanent magnet 12 exists. This circuit detects the distance L and detects the displacement of the permanent magnet 12 based on the distance L.

By the way, as described above, the magnetostrictive wire 10 is a member that produces distortion under the influence of an external magnetic field. On the other hand, the magnetic field generated by the permanent magnet 12 acts on the magnetostrictive wire 10 in the axial direction from the beginning, and when a pulse signal is supplied from the pulse generation circuit 14, the pulse signal flows through the pulse signal. Accordingly, a magnetic field also acts in the circumferential direction of the magnetostrictive wire 10.

Therefore, when the pulse signal flows in the vicinity of the permanent magnet 12, the magnetic field generated in the circumferential direction of the magnetostrictive wire 10 and the magnetic field generated in the axial direction of the magnetostrictive wire 10 Work in superposition. Then, as a result, a temporary torsional strain is generated at the relevant portion of the magnetostrictive wire 10.

This torsional distortion is caused by the permanent magnet 1 of the magnetostrictive wire 10.
The signal is instantaneously generated in the vicinity of 2 and generates an ultrasonic vibration-like signal, that is, the above-described distortion signal. Then, this distortion signal travels toward both ends thereof at a propagation speed according to the characteristics of the magnetostrictive wire 10, and is thereafter received by the receiving circuit 16 as described above.

Here, the magnetic field distribution of the permanent magnet 12 on the magnetostrictive wire 10 shown in FIG. 2A has a shape as shown in FIG. When a pulse signal is supplied from the pulse generating circuit 14 to the magnetostrictive wire 10 in a state where the fixing member 11 is not provided in FIG. 1, the signal waveform received by the receiving circuit 16 is as shown in FIG.
(A). In FIG. 3A, the pulse signal 21 is received at the same time as the supply of the pulse signal to the magnetostrictive wire 10, and the distortion signal 22 is received after a lapse of a predetermined time. FIG. 2B shows an enlarged view of the distortion signal 22. The distortion signal 22 has a waveform similar to the magnetic field distribution shown in FIG. 2B and has a positive polarity peak.

On the other hand, when a pulse signal is supplied from the pulse generation circuit 14 to the magnetostrictive wire 10 with the fixing member 11 provided, the signal waveform received by the reception circuit 16 is shown in FIG. Like that. In the figure, magnetostriction line 1 of the pulse signal
The pulse signal 23 is received at the same time as the supply to 0, and the distortion signal 24 is received a predetermined time after that. As for the distortion signal 24 as magnetic information, the distortion is detected from the position of the permanent magnet 12 to the detection unit 1.
The positive peak 24a detected when propagating to the position 0a and the distortion are reflected by the fixed portion 10b, propagated to the permanent magnet 12 side, and the negative peak 24b detected at the detecting portion 10a are synthesized. It is a thing.

In the received signal waveform shown in FIG. 3 when the fixing member 11 is provided, the positive peak 24a of the distortion signal 24 is shown.
The generation timing of the midpoint 24c between the peak 24b and the negative polarity peak 24b does not change even when the levels of the peaks 24a and 24b change, and is detected at a substantially constant position.

When the electromagnetic actuator of the shock absorber is not operated, the waveform of the distortion signal 24 is not deformed as shown in FIG. 4A, but when the electromagnetic actuator is operated, for example, as shown in FIG. Signal 24
May be deformed under the influence of the magnetic field generated by the electromagnetic actuator. FIG. 4 (A)
Relative obtained a received signal to a normal state without deformation of the distortion signal 24 is compared with the threshold value V _th magnetostrictive propagation time Delta] t ₁ as shown in, the abnormal distortion signal 24, as shown in (B) is deformed The sometimes obtained magnetostriction propagation time Δt ₂ becomes long, and an accurate magnetostriction propagation time cannot be measured.

The middle point 24c corresponds to the point in time when the propagated distortion is reflected by the fixed portion 10b. The time from when the pulse signal 23 is detected to when the midpoint 24c of the distortion signal 24 is detected is a propagation time t at which the distortion signal generated at the position of the permanent magnet 12 propagates through the magnetostrictive wire 10 and reaches the fixed part 10b. .

The speed at which the distortion signal propagates through the magnetostrictive wire 10 is a speed uniquely determined according to the physical properties of the magnetostrictive wire 10. Therefore, assuming that the propagation speed is V, the distance L between the permanent magnet 12 and the fixed portion 10b can be obtained by L = t · V. FIG. 5 shows a circuit diagram of the receiving circuit 16. In the figure, a coil 26 is a pickup coil that detects a change in magnetic flux generated in the magnetostrictive wire 10 around the detection unit 10a. A capacitor 28 and a resistor 30 are connected in parallel to the coil 26 to form an LCR parallel resonance circuit. An amplifier 32 is connected to the LCR parallel resonance circuit.

Here, the resonance frequency of the LCR parallel resonance circuit is determined by the change in magnetic flux detected by the coil 26 when the pulse signal circulates in the vicinity of the magnetostrictive wire detecting section 10a and when the distortion signal reaches the detecting section 10a. Frequency is set.
Therefore, the amplifier 32 is supplied with only a signal caused by a change in magnetic flux at that frequency.

The output terminal of the amplifier 32 is connected to the comparator 3
4 and the negative terminal of the comparator 36. That is, FIG. 6 (C) shows that when the LCR resonance circuit receives the reception signal V _IN shown in FIG.
2 shows the signal waveform output from the comparator 2, and the comparators 34 and 36 are supplied with a signal obtained by amplifying the pulse signal 23 and the distortion signal 24 as shown in FIG. Become. In the following description, these amplified signals are also simply referred to as pulse signals 23 or distortion signals 24 for simplicity.

The negative terminal of the comparator 34 has a resistor 3
Predetermined voltage formed using the 8 is supplied as the threshold TH _B. This threshold value TH _B is set to a value lower than the positive peak value 24a of the distortion signal 24, as shown in FIG. The output terminal of the comparator 34 is connected to a power supply voltage via a pull-up resistor 40. Therefore, the output of the comparator 34 is as shown in FIG.
As shown in (D), when the pulse signal 22 and the positive peak 24a appear, a signal that changes from a low level to a high level appears.

On the other hand, the positive terminal of the comparator 36
As shown in FIG. 6C, the distortion signal 2
The voltage set to a value higher than the negative peak value 24b of No. 4 is supplied as the threshold value TH _C. The output terminal of the comparator 36 is connected to a power supply voltage via a pull-up resistor 40.

Accordingly, the output of the comparator 36 is as shown in FIG.
As shown in (F), when the rising edge of the pulse signal 22 appears and when the negative peak of the distortion signal 24 appears, a signal that changes from low level to high level appears. Output terminals of the comparators 34 and 36 are connected to input terminals of inverters 50 and 52 via capacitors 46 and 48, respectively. An intermediate portion between the capacitor 46 and the inverter 50 is connected to a power supply voltage via a resistor 54 and a diode 56. Note that the diode 56 is arranged in a direction that allows only a flow toward the power supply voltage side.

In this case, if the output of the comparator 34 is stable at a low level, the capacitor 46 is charged and a voltage drop due to the resistor 54 does not occur, so that a high-level signal is input to the input terminal of the inverter 50. It will be in the supplied state. In addition, the comparator 3
When the four outputs go to the high level, the electric charge charged in the capacitor 46 is discharged to the power supply voltage side through the diode 56. In this case, almost no current flows through the resistor 54, so that the power supply voltage is still applied to the input terminal of the inverter 50.

When the output of the comparator 34 goes low again after the capacitor 46 has been discharged in this way, the resistance 5 is maintained until the charging of the capacitor 46 is completed.
Electric current flows through 4. For this reason, the input terminal of the inverter 50 is supplied with a voltage dropped according to the value of the current flowing through the resistor 54 until the charging of the capacitor 46 is completed.

That is, after the C terminal is inverted from the high level to the low level at the input terminal of the inverter 50,
A signal whose voltage drops transiently for a predetermined period is supplied. Therefore, the output terminal of the
As shown in FIG. 6 (E), a signal which temporarily becomes high level by capturing the falling edge of the output of the comparator 34 appears.

An intermediate portion between the capacitor 48 and the inverter 52 is grounded via a resistor 58 and a diode 60. Note that the diode 60 is arranged in a direction that allows only a flow from the ground side to the intermediate portion between the capacitor 48 and the inverter 52.

Therefore, if the output of the comparator 36 is stable at a low level, no potential difference occurs between both ends of the capacitor 48, and the capacitor 48 is discharged. When the output of the comparator 36 becomes high level from this state, charging of the capacitor 48 is started.

At this time, the diode 60 functions so as to prevent the flow of electric charge caused by charging, so that all the charging current flows through the resistor 58. Therefore, the voltage of the input terminal of the inverter 52 temporarily rises to a high level until the charging of the capacitor 48 is completed.

After the charging of the capacitor 48 is completed, when the output of the comparator 36 becomes low again, the discharging of the capacitor 48 is started. in this case,
A current flows from the ground side to the capacitor 48, and the current mainly flows through the diode 60.
Therefore, there is no potential difference between both ends of the resistor 58, and the input terminal of the inverter 52 is also supplied with the ground level voltage.

As described above, a high level signal is transiently supplied to the input terminal of the inverter 52 for a predetermined period after the output of the comparator 36 is inverted from the low level to the high level. Accordingly, at the output terminal of the impeller 52, a signal which temporarily captures the rising edge of the output of the comparator 36 and becomes high temporarily appears as shown in FIG. 6 (G).

The pulse generating circuit 14 is connected to the terminal 61.
The pulse signal shown in FIG. 6A supplied from the monostable multivibrator (monomulti) 63 shown in FIG.
As shown in (B), a negative pulse having a predetermined pulse width is supplied to the set terminals of the SR flip-flops 62 and 64.

Here, the flip-flops 62 and 64 are
When a rising edge is detected at the set terminal, the output Q is inverted from low level to high level, and when a rising edge is detected at the reset terminal when the set terminal is low level, the output Q is changed from high level. It has the function of inverting to low level.

Therefore, the output terminal of the flip-flop 62 is inverted from low level to high level after a predetermined period from the rise of the pulse signal 22, as shown in FIG.
Thereafter, the positive polarity peak 24a of the distortion signal 24 becomes the threshold T
So that the signal maintains the high level appears to below H _B.

As shown in FIG. 6I, the output terminal of the flip-flop 64 inverts from a low level to a high level after a predetermined period from the rise of the pulse signal 22, and thereafter, the negative peak 24b of the distortion signal 24. Is the threshold TH
So that the signal maintains the high level appears to below _{C (TH C = -TH B)} .

Accordingly, since the pulse width of the mono-multi 63 is constant, the time during which the pulse signal appearing at the output Q of the flip-flop 62 maintains the high level,
If the average with the time during which the pulse signal appearing at the output Q of the flip-flop 64 maintains the high level is obtained, the time from when the pulse signal 23 rises to when the midpoint 24c of the distortion signal 24 is detected is almost accurately obtained. Can be requested.

Further, the comparator 34 shown in FIG.
The output is supplied to the set terminal of the SR flip-flop 66, and the output of the comparator 36 shown in FIG. The flip-flop 66 inverts the output Q from a low level to a high level when a rising edge is detected at the set terminal, and turns the output Q high when a falling edge is detected at the reset terminal when the set terminal is low. It has the function of inverting from level to low level.

Accordingly, the flip-flop 66 goes high when the output of the comparator 34 rises and goes low when the output of the comparator 36 falls.
A pulse signal shown in (J) is generated and output. Returning to FIG. 1, the receiving circuit 16 flip-flops 62, 6
The four output pulse signals are supplied to the propagation time detection circuit 18. The propagation time detection circuit 18 calculates the average of the time during which the pulse signal output from the flip-flop 62 maintains the high level and the time during which the pulse signal output from the flip-flop 64 maintains the high level. After rising, the propagation time until the midpoint 24c of the distortion signal 24 is detected is determined.

The flip-flop 6 of the receiving circuit 16
The pulse signal output from 6 is supplied to the determination circuit 19.
The determination circuit 20 determines whether the pulse width τ _{1 of the} pulse signal shown in FIG. 6 (J) satisfies the following expression and is within a predetermined time range. τ ₀ −α ₀ <τ ₁ <τ ₀ + α ₀ where τ ₀ is that the distortion signal 24 is equal to the threshold value TH _B during normal operation.
, And exceeds the threshold value TH _C , and α ₀ is a margin time for a minute value. That is, if the pulse width τ ₁ is within the range of τ ₀ ± α ₀ , it is assumed that the distortion signal 24 is normal without deformation and the pulse width τ ₁ is τ ₀ ± α ₀
If the distortion signal 24 is out of the range, the distortion signal 24 is deformed under the influence of the external magnetic field generated by the electromagnetic actuator or the like, and is regarded as abnormal.

Based on the above determination result, the determination circuit 19 supplies a prohibition signal to the propagation time detection circuit 18 when the pulse width τ ₁ is outside the range of τ ₀ ± α. Propagation time detection circuit 1
8 supplies the magnetostriction propagation time to the displacement detection circuit 20 only when the prohibition signal is not supplied from the determination circuit 19, and determines the propagation time displacement detection circuit 20 which is determined to be supplied with the prohibition signal.
Stop supply to.

Thus, the displacement detecting circuit 20 detects the detecting section 10a set on the magnetostrictive line 10 based on the supplied propagation time except when the distortion signal 22 is deformed under the influence of the external magnetic field. The distance L between the position and the position where the permanent magnet 12 exists is detected without error.

As described above, even when the electromagnetic actuator of the shock absorber is inactive as well as in operation,
A highly reliable relative displacement can be calculated from the propagation time of a normal distortion signal without being affected by the magnetic field generated by the electromagnetic actuator, and highly reliable magnetic information can be positively used.

In the above embodiment, the distortion signal 24 is
Current eagle as the pulse width of the output pulse signal of H _B from TH _C level range time in the flip-flop 66, the pulse width tau ₁ to determine whether a predetermined time range tau ₀ ± alpha within ₀ Thus, whether or not the waveform of the distortion signal 24 is deformed, that is, whether the waveform is normal or abnormal, is simply and accurately determined. Threshold TH _B, TH _C representing here
And the predetermined time range τ ₀ ± α ₀ is the condition which is not influenced by the external magnetic field, after having determined beforehand, and a value set, Ru various changeable der upon request detection accuracy.

[0053]

As described above, the first aspect of the present invention provides
When the shock absorber electromagnetic actuator is
Is affected by the magnetic field generated by the electromagnetic actuator.
A reliable phase from the propagation time of magnetic information that is normal
Active displacement of magnetic information with high reliability
Available.

[0054]

[0055]

[0056]

[Brief description of the drawings]

FIG. 1 is a configuration conceptual diagram of a displacement detection device according to an embodiment of the present invention.

FIG. 2 is a diagram for explaining a distortion signal.

FIG. 3 is a diagram for explaining a distortion signal.

FIG. 4 is a diagram for explaining a distortion signal according to the present invention.

FIG. 5 is a circuit diagram of a part of the displacement detection device of the present embodiment.

FIG. 6 is a time chart for explaining the operation of the displacement detection device of the present embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Magnetostrictive wire 10a Detecting part 10b Fixing part 11 Fixing member 12 Permanent magnet 14 Pulse generating circuit 16 Receiving circuit 18 Propagation time detecting circuit 19 Judgment circuit 20 Displacement detecting circuit 26 Coil

Claims (1)

(57) [Claims] 1. A magnetic detecting means for detecting magnetic information whose propagation time changes according to a displacement of a relative position between a first member and a second member which are relatively movable, and magnetic information detected by the magnetic detecting means. A relative displacement detector that includes a propagation time detector that detects a propagation time of the magnetic information, and a relative displacement detector that calculates a relative displacement between the first member and the second member from the propagation time. It detects the time waveform in a predetermined level range
Error when the detection time is out of the predetermined time range.
And judgment, relative displacement detecting device, characterized in that it comprises a determining means for the propagation time is prohibited from being employed in the calculation of the relative displacement amount when it is determined that abnormality.