JPH0690053B2 - Distortion detector strain detector - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a strain detector for a displacement detector that detects a mechanical displacement of an object or a displacement of a liquid surface by using a magnetostriction phenomenon.

[Conventional technology]

Conventionally, various types of displacement detectors such as a differential transformer, a potentiometer, and a capacitance type displacement detector have been known as displacement detectors for detecting mechanical displacement of an object or displacement of a liquid surface. The applied displacement detector is particularly excellent in linearity and resolution.

As this type of magnetostrictive displacement detector, U.S. Patent No. 3,898,55
As described in Japanese Patent Laid-Open No. 5 (1994), it is known that a conductor wire is inserted through the center of a circular magnetostrictive wire and a movable permanent magnet is arranged outside the magnetostrictive wire. Then, by causing a current pulse to flow through the conducting wire, a torsional strain is generated in a portion where the magnetostrictive wire is close to the permanent magnet, and the torsional strain is converted into an electric signal by a strain detecting device provided at one end of the magnetostrictive wire, The mechanical displacement given to the permanent magnet is detected by measuring the propagation time of the torsional strain.

The above-mentioned strain detection device is composed of two strips whose free ends are fixed to the front and back sides of the magnetostrictive wire, a receiving coil wound around these strips, and a bias magnet arranged between the strips. The torsional strain propagated through the magnetostrictive line is converted into a longitudinal strain of the strip, and this is converted into an electric signal by a coil.

[Problems to be Solved by the Invention]

In the case of the strain detecting device, the free end of the strip is fixed to the magnetostrictive wire by welding, but if the welding is performed in a wide area as much as possible, the torsional strain propagating the magnetostrictive wire is dispersed at the welded portion, There is a drawback that a beautiful waveform cannot be detected because it is reflected. Therefore, the welding work requires a high degree of skill and close attention, and there is a problem that productivity is deteriorated and cost is increased.

Therefore, an object of the present invention is to provide a strain detector for a displacement detector that is easy to manufacture and that can convert torsional strain into an electrical signal with high accuracy.

[Means for Solving the Problems]

In order to achieve the above object, the strain detection device of the present invention is provided in a specific portion of the magnetostrictive line, a probe that intersects and contacts the magnetostrictive line, detects the axial strain of the probe, and an electrical signal. A receiver for converting to, a probe and a magnetostrictive wire disposed outside the probe, and an elastic body for pressing and holding the two, and an adjusting means for pressing the back of the elastic body to adjust the press-contact force between the probe and the magnetostrictive wire. It is equipped with.

[Action]

A first feature of the present invention is that the magnetostrictive wire and the probe are in contact with each other in a cross shape without any unnecessary portion such as a welded portion, and are pressed and held from both sides via elastic bodies. When the magnetostrictive wire and the probe are fixed by welding etc., the torsional strain of the magnetostrictive wire is efficiently converted into the axial strain of the probe, but on the contrary, the torsional strain is dispersed and reflected at the welded part, which is originally necessary at the receiving part. Not only unnecessary waveforms but also many unnecessary waveforms are detected. On the other hand, if the magnetostrictive wire and the probe are pressed and held from both sides via the elastic body, the conversion efficiency of the torsional strain into the axial strain is slightly lower than that at the time of welding, but the magnetostrictive wire and the probe are at the time of welding. Since the contact is made in a narrow area, there is little dispersion or reflection of the torsional strain at the contact portion, and the elastic body suppresses the dispersion or reflection of the torsional strain, and the receiving portion can detect a "clean waveform" with few unnecessary waveforms.

The second feature of the present invention is that the pressure contact force between the magnetostrictive wire and the probe can be adjusted by the adjusting means. When the magnetostrictive wire and the probe are fixed by welding, the reflected wave differs greatly depending on the size of the welding area, and the quality of welding greatly affects the waveform detected by the receiver. Moreover, adjustment after welding is completely impossible. On the other hand, in the present invention, since the pressure contact force can be adjusted by the adjusting means, the desired waveform can always be adjusted by operating the adjusting means while watching the detected waveform of the receiver after assembling. Therefore, it is possible to obtain a uniform strain detection device with less variation in the detection waveform of each product.

In addition, in the present invention, when assembling the magnetostrictive wire and the probe,
Since the magnetostrictive wire and the probe are sandwiched from both sides via the elastic body and they are only tightened by the adjusting means, there is no need for complicated welding work as in the past, assembly is easy and productivity is remarkably high. improves. Further, according to the present invention, the magnetostrictive wire and the probe can be easily disassembled, so that if the receiving part fails, only the receiving part needs to be replaced, and the other parts, that is, the magnetostrictive line, the elastic body, the adjusting means, etc., remain unchanged. It has the advantage of being shared.

It is desirable that the magnetostrictive line and the probe intersect at a right angle because the torsional strain propagating through the magnetostrictive line can be most efficiently converted into the axial strain of the probe.

〔Example〕

 FIG. 1 shows a specific example of the displacement detector according to the present invention.

In the drawing, the magnetostrictive wire 1 is inserted into a non-magnetic and conductive middle cylinder 7, and inside both ends of the middle cylinder 7, an elastic body 8 such as a rubber through which the magnetostrictive wire 1 penetrates is incorporated. There is.
Then, after applying tension to the magnetostrictive wire 1, both ends of the middle cylinder 7 are compressed to form the narrowed portions 9, thereby simultaneously pressing the magnetostrictive wire 1 and the elastic body 8, and the magnetostrictive wire 1 is It is equipped in the cylinder 7.

Since the elastic body 8 is in close contact with the outer circumference of the magnetostrictive wire 1 in the narrowed portion 9, the ultrasonic wave propagated to both ends of the magnetostrictive wire 1 is effectively absorbed by the elastic body 8. Therefore, only the ultrasonic wave due to the torsional strain generated in the permanent magnet 2 is formed in the opening 25 formed in the middle cylinder 7.
After that, the distortion can be detected by the strain detection device 4.

Since the start end of the magnetostrictive wire 1 is connected to the conducting wire 12, the rear end thereof is electrically connected to the right end of the middle cylinder 7 by the conducting wire 10, and the left end of the middle cylinder 7 is connected to the conducting wire 11, the multicore cable 15 The current pulse supplied by the magnetic field flows through the magnetostrictive line 1. In addition,
In this embodiment, the middle cylinder 7 is used as a part of the conductor, but when the middle cylinder 7 is made of a non-conductive material,
If another conductor wire (not shown) is provided between the rear end of the magnetostrictive wire 1 and the conductor wire 11, the same purpose is achieved.

The middle cylinder 7 equipped with the magnetostrictive wire 1 is inserted into a non-magnetic outer cylinder 17, and a vibration absorbing material 23 made of, for example, a sponge is provided in an annular space formed between the outer cylinder 17 and the middle cylinder 7. Are arranged. The vibration absorbing material 23 absorbs and attenuates mechanical vibrations and shocks from the outside that act on the outer cylinder 17, the case 20 welded to the outer cylinder 17, or joined and fixed by another mechanical method. The necessary disturbance is prevented from being detected by the strain detector 4.

At the right end of the outer cylinder 17, an end cap 18 is press-fitted or fixed by another mechanical method, for example, even if the outer cylinder 17 is in liquid, the liquid does not enter the outer cylinder 17,
It is possible to detect the position of the permanent magnet 2.

A case cover 19 is inserted and fixed at the left end of the case 20, and the multi-core cable 15 is penetrated through the case cover 19 to connect the case 20 to the case 20.
Has been introduced within. The multi-core cable 15 can supply a current pulse to the magnetostrictive wire 1 and take out the detection signal of the strain detecting device 4 through the conductors 13 and 14. Also,
If a shield wire is used as the multi-core cable 15, the shield conductor 16 is electrically connected to the inner surface of the case 20,
The outer cylinder 17 can also be used as an electric shield for the magnetostrictive wire 1 and the strain detecting device 4.

The displacement detector having the above-described configuration is configured such that the screw portion 21 of the case 20 is inserted into the fixed portion 24 of the machine or the like where displacement is to be detected, and the nut 22 is tightened and fixed, and the permanent magnet is attached to the movable portion (not shown) of the machine or the like. If 2 is fixed, it can be easily installed and the displacement of a movable part such as a machine can be detected.

FIG. 2 shows an example of the strain detection device 4 which is the main part of the present invention.

A probe 26, to which a piezoelectric element 27, which is an example of a receiver, is attached at the left end, is in contact with the magnetostrictive wire 1 at an angle, and a U-shaped holding metal fitting 29 is interposed between the magnetostrictive wire 1 and an elastic body 28 such as rubber.
Holds contact with the probe 26. Then, by tightening the left end portion of the retainer fitting 29 with the screw 30, the contact between the magnetostrictive wire 1 and the probe 26 is made more reliable.

When the torsional strain generated at the position where the permanent magnet 2 is close to the magnetostrictive line 1 reaches the portion of the magnetostrictive line 1 in contact with the probe 26, the torsional strain 31 causes a strain 32 in the axial direction of the probe 26. An electric signal corresponding to the magnitude of the strain 32 is obtained between the conducting wires 13 and 14 connected to the bipolar plates of the piezoelectric element 27. Thus, since the magnetostrictive wire 1 and the probe 26 are in point contact with each other at an angle, the influence of the reflection of the torsional strain due to the contact of the probe 26 can be minimized, and highly accurate detection can be performed.

〔The invention's effect〕

As is apparent from the above description, according to the present invention, the probe is crossed with the magnetostrictive wire and pressed against it, so that the torsional strain of the magnetostrictive wire is converted into the axial displacement of the probe, which is troublesome welding. No steps are required and manufacturing is much easier.

Further, since the back of the probe and the magnetostrictive wire is supported by an elastic body, and the pressure contact force between the probe and the magnetostrictive wire can be adjusted by the adjusting means, an appropriate pressure contact force can be easily obtained, and the elastic body It is possible to suppress the dispersion and reflection of the torsional strain that has reached the contact portion with the probe, and to detect a clean waveform as compared with the conventional welding method.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an embodiment of the displacement detector according to the present invention, and FIG. 2 is an enlarged cross-sectional view of the strain detecting device as seen from the axial direction of the magnetostrictive line. 1 ... Magnetostrictive line, 2 ... Permanent magnet, 4 ... Strain detection device, 26
...... Probe, 27 ...... Piezoelectric element, 28 …… Elastic body.

Claims (1)

[Claims] 1. A current pulse is applied to a magnetostrictive line to generate a torsional strain at a portion of the magnetostrictive line that is adjacent to a permanent magnet that can move along the magnetostrictive line, and the propagation time of the torsional strain to a specific portion of the magnetostrictive line is set. In a displacement detector that detects the mechanical displacement applied to a permanent magnet by measuring, a probe that is provided at a specific part of the magnetostrictive line and that crosses and contacts the magnetostrictive line, and the axial strain of the probe Detect and
A receiver for converting into an electric signal, an elastic body arranged outside the probe and the magnetostrictive wire and holding them in pressure contact, and an adjustment for pressing the back of the elastic body to adjust the pressure contact force between the probe and the magnetostrictive wire. Distortion detecting apparatus for a displacement detector, comprising: