JPS5856412B2 - displacement detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a displacement detection device that converts mechanical displacement or mechanical position into an electrical signal using magnetostrictive wires.

The purpose of the present invention is to have a simple structure, to avoid the influence of the propagation speed of an ultrasonic signal propagating within a magnetostrictive wire, and to apply an excitation pulse current to an excitation means for generating an ultrasonic signal before transmitting the ultrasonic signal within the magnetostrictive wire. The present invention aims to realize this type of device that can detect displacement with high accuracy without being affected by time delays until ultrasonic signals are generated.

Another object of the present invention is to realize a device that is not affected by environmental changes such as changes in ambient temperature and can always detect displacement with high accuracy.

FIG. 1 is a block diagram showing an embodiment of the present invention.

In the figure, 1 is, for example, Ni-8PANC. A magnetostrictive wire made of a linear magnetostrictive material such as Ni, 2 is a first receiving means placed at one end of the magnetostrictive wire 1, and 3 is a second receiving means placed at the other end of the magnetostrictive wire. , here we show examples in which both are constructed from coils wound around magnetostrictive wires.

4 is a permanent magnet that moves while its magnetic field intersects with the magnetostrictive wire 1, and mechanical displacement is applied to this permanent magnet 4.

O8 is an excitation pulse generator whose output pulse current ip is supplied to the magnetostrictive wire 1.

FF1. FF2 is a flip-flop circuit, and an excitation pulse signal ip is applied to the cent terminal S of each flip-flop circuit.

Further, a signal e1 from the first receiving means 2 is applied to the reset terminal R of the flip-flop circuit FF1, and a signal e2 from the second receiving means 3 is applied to the reset terminal R of the flip-flop circuit FF2.

CK is a flip-flop circuit FF1. Time width signal PW1. obtained from FF2. This is an arithmetic circuit that receives PW2 as an input.

The operation of the device configured in this way is shown in Figures 2 and 3 below.
This will be explained with reference to the figures.

First, an excitation pulse current ip is supplied from the excitation pulse generator O8 to the magnetostrictive wire 1 as shown in FIG. 3A.

Here, when an excitation pulse current flows through the magnetostrictive wire 1, a torsional moment is given in the magnetostrictive wire 1 at the position where the permanent magnet 4 is present due to the interaction between the magnetic field caused by this excitation pulse current and the magnetic field of the permanent magnet 4. An ultrasonic signal (torsional elastic wave signal) is generated.

That is, in FIG. 2, when a pulse current flows through the magnetostrictive wire 1, the magnetic field F2 due to this current acts on the magnetic field F□ caused by the permanent magnet 4, and the magnetic field on the right side of the magnetostrictive wire 1 becomes larger than the magnetic field on the left side.

Therefore, an imbalance occurs in the magnetic field distribution in the cross section of the magnetostrictive wire 1, and an ultrasonic signal is generated.

The ultrasonic signal thus generated at the location of the permanent magnet 4 propagates toward both ends of the magnetostrictive wire 1 and reaches the first receiving means 2.
and detected by the second receiving means 3.

Now, if it is assumed that an ultrasonic signal is generated in the magnetostrictive wire 1 at the same time as the excitation pulse current ip is supplied to the magnetostrictive wire 1, the time t1 and t2 is expressed by equation (1) and (2)
It can be expressed by the formula.

The excitation pulse ip is applied to the magnetostrictive wire 1 and the flip-flop circuit FF1. It is applied to the cent terminal S of FF2, and each flip-flop circuit FF□,
Set the FF2 as shown in FIG. 2, 2 and E.

Also, after t, t2 after applying the excitation pulse ip, the first
The pulsed voltage signal e1. obtained by the receiving means 2 and the second receiving means 3. e2 is a flip-flop circuit FF1
．． The voltage is applied to the reset terminals of FF2, respectively, and these are put into a reset state as shown in FIG.

Therefore, from the output ends of the flip-flop circuits FF□ and FF2, as shown in FIG. 2, tl.

A time width signal PW1. having time widths t1 and t2 proportional to t2. PW2 is obtained.

The arithmetic circuit CK includes each flip-flop circuit FF1゜FF.
As for the time width signal PW from 2, let PW2 be the input.

For example, time width t1. By detecting t2 and calculating equation (3), a signal Eo related to the permanent magnet 4, that is, the mechanical displacement, can be obtained from the output terminal OUT.

In equation (3), t1+t2 is the distance between the first receiving means 2 and the second receiving means 3, and is a constant value regardless of the displacement position X of the permanent magnet 4, so the output signal Eo is It is exactly proportional to the mechanical displacement position X.

Note that if the arithmetic circuit CK is configured with a digital arithmetic circuit, the output signal Eo can be easily obtained as a digital signal, and the output signal Eo can be easily obtained as an analog signal if the arithmetic circuit CK is configured with an analog circuit.

The signal Eo related to the position It has the feature of being able to

One of the features of the device configured in this way is that a permanent magnet 4 for generating an ultrasonic signal within the magnetostrictive wire 1 is placed between the two receiving means 2 and 3. Due to this arrangement, the ultrasonic signal propagates from the permanent magnet 4 under the same conditions on the left and right sides, and tl t2
By calculating , it is possible to easily eliminate errors caused by time delays in the oven where an ultrasonic signal is actually generated within the magnetostrictive wire 1 after the excitation pulse ip is applied to the magnetostrictive wire 1.

That is, if this time delay is α, then, for example, equation (4) becomes Eo=(t1+α)(t2+α)=t1−t2, and the influence of α disappears.

Further, in the apparatus shown in FIG. 1, the first receiving means 2, the second
Since all of the receiving means 3 can be fixed to the magnetostrictive wire 1, by housing these means in a shield case or the like, there is an effect that the influence of external noise etc. can be eliminated.

It also has the advantage of not being affected by changes in length due to linear expansion of the magnetostrictive wire 1 itself due to temperature changes or the like.

That is, α is the linear expansion coefficient of magnetostrictive wire 10, and At is the temperature change.
If we rewrite equation (3) taking this into account, we get equation (4), and the device configured in this way has the following characteristics: The influence of changes in the degree of coupling between the permanent magnet and the magnetostrictive wire can be removed.

That is, the ultrasonic signals generated within the magnetostrictive wire 1 at the position of the permanent magnet 4 and propagated to the left and right are signals with approximately the same amplitude regardless of the degree of coupling between the magnetostrictive wire 1 and the permanent magnet 4, and each Receiving means 2 and 3 receive this and reset each flip-flop.

From this, the time width t1. of the signal from each flip-flop. At t2, the change in the amplitude value of the propagation signal (
Errors due to variations in the amplitude value (which vary depending on changes in the degree of coupling between the permanent magnet 4 and the magnetostrictive wire 1) also intervene in the same way.

Therefore, this error can be canceled by performing the calculation of equation (3) including the calculation of tl-t2.

Therefore, according to the device according to the present invention, the displacement position can be measured with high accuracy without being affected by environmental changes.

A signal corresponding to the displacement position X is obtained by performing calculations including calculations. (affected by changes) will be canceled by calculation, and will not be affected by environmental changes such as changes in ambient temperature.

FIG. 4 is a block diagram of the configuration when the present invention is applied to an automatic balance meter.

Components corresponding to those in FIG. 1 are designated by the same reference numerals.

In the figure, Ei is the input signal to be measured and recorded, and AM is the input signal Ei and the feedback signal E from the arithmetic circuit CK, which will be described later.
An amplifier that receives a deviation signal ε from f and drives the balanced motor BM according to the deviation ε.

The balance motor BM is connected to the recording pen PN that moves on the recording paper 5 and is also connected to the permanent magnet 4.

Received signal e1 from receiving means 2 and receiving means 3.

e2 is connected to the flip-flop circuit FF1 through the comparator amplifier OP2. It is applied to the reset terminal R of FF2.

These comparison amplifiers OP1 yOP2 are connected to each receiving means 2.
, 3 by comparing it with the reference voltage Es.

A signal Ef related to the position of the permanent magnet 4 (corresponding to the position of the recording pen PN) obtained from the arithmetic circuit CK is given to the deviation detection circuit EA, and is sent to the amplifier AM and the balanced motor BM.
, the circuit loop including the magnetostrictive wire 1 and the arithmetic circuit CK is E
The permanent magnet 4 (recording pen PN) moves so that f=Ei, and is automatically balanced there.

Therefore, the permanent magnet 4, that is, the recording pen PN, can be made to accurately follow the input signal Ei, and the magnitude of the input signal Ei can be determined from the recording position.

FIGS. 5 and 6 are configuration diagrams showing an example of application of the device of the present invention.

Figure 5 shows the case where the permanent magnet 4 is applied to a level meter.
is coupled to a float 6 and moves up and down along the magnetostrictive line 1 in response to the displacement of the liquid level in the tank.

Figure 6 shows the case where it is applied to a differential pressure converter.
The connecting rod connecting the magnetostrictive wires 1 and 72 is made of the magnetostrictive wire 1, and the first receiving means 2 and the second receiving means 3 are fixedly arranged at both ends of the magnetostrictive wire 1. It is fixed to the body 8 so as to be sandwiched between the receiving means 3 and the second receiving means 3.

The body 8 is composed of two parts 81 and 82 with an insulating material 80 in between, and the pulse current ip is supplied to the magnetostrictive wire 1 through diaphragms 71 and 72. be done.

The diaphragms 71, 72 are displaced according to the difference between the pressures P□ and P2 introduced on one side thereof, and the magnetostrictive lines 1. Both the first receiving means 2 and the second receiving means 3 are displaced.

Note that in each of the above embodiments, the arithmetic circuit that receives two time width signals as input uses (3) a digital method.
These calculations may be performed using formulas, or may be performed using an analog method.

As described above, according to the present invention, it is possible to realize a highly accurate displacement detection device that has a simple structure and is not affected by environmental changes such as changes in ambient temperature.

[Brief explanation of the drawing]

Figure 1 is a configuration block diagram showing one embodiment of the present invention.
The figure is an explanatory diagram for explaining the operating principle in which ultrasonic signals are generated in magnetostrictive wires, Figure 3 is an operating waveform diagram of the device shown in Figure 1, and Figure 4 is when the present invention is applied to an automatic balance instrument. FIGS. 5 and 6 are block diagrams showing application examples of the apparatus of the present invention. 1... Magnetostrictive wire, 2, 3... Receiving means,
4... Permanent magnet, O8... Excitation pulse generator, FF1. FF2...Flip flop circuit, CK/°...Arithmetic circuit.

Claims (1)

[Claims] 1. A magnetostrictive wire made of a magnetostrictive material, a first receiving means and a second receiving means coupled to the magnetostrictive wire, and a mechanical displacement is applied to move along the magnetostrictive wire so that the magnetic field intersects the magnetostrictive wire. through the magnetostrictive wire. Second
a permanent magnet placed between the receiving means, an excitation pulse generator for supplying an excitation pulse current to the magnetostrictive wire, set by the excitation pulse from the excitation pulse generator and set by the pulse from the first receiving means; a first flip-flop circuit that is reset; a second flip-flop circuit that is set by the excitation pulse and reset by a pulse from the second receiving means;
Time width t1 output from the second flip-flop circuit
．． Input the signal of t2 and at least (t□-tz)/
A displacement detection device comprising an arithmetic circuit means for performing an arithmetic operation (tt + tz) to obtain a signal corresponding to the mechanical displacement.