JPH0432724A - Noncontact type displacement detector - Google Patents

Abstract

PURPOSE:To increase S/N and to improve the resolution by providing a short- circuit current path on a plane perpendicular to the axis of a coil which detects the displacement of a body to be detected while the axis is surrounded, making the whole structure compact, and reducing the influence of a disturbing high frequency magnetic field. CONSTITUTION:When the body 1 to be detected is displaced, magnetic flux PHIis varied and the displacement detector detects the quantity of the displacement of the object body 1 from variation of a current flowing to the detection coil 2 corresponding to the variation of the magnetic flux PHI. When a disturbind magnetic field is applied to the coil 2 and a stabilizing coil 4 provided covering the coil 2, lines of magnetic force cross-link with the coil 4, where an electromotive force is induced. The coil 4 is short-circuited, so the current based upon the electromagnetic force flows to generate the lines of magnetic force canceling the applied lines of magnetic force with the current. The lines of magnetic force due to the disturbing magnetic field, however, do not cross-link with the coil 2 and the coil 2 is therefore shielded from the disturbing magnetic field, so that the quantity of displacement of the object body 1 can be detected with the high S/N.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a non-contact displacement detection device used for vibration control of shaft vibration measuring instruments, magnetic bearings, etc., and particularly when a disturbance magnetic field is applied to the displacement detection device. The present invention relates to a non-contact displacement detection device that can detect displacement without being affected by the magnetic field.

(Prior art) As shown in FIG. 4, a conventional displacement detection device of this type includes a detection device arranged in the direction of displacement of the shaft body l, which is the object to be detected, and facing each other. Vessel Ha.

A device has been proposed that includes cores 3b and 3c of A, and detection coils 2e and 2d that are wound around the cores with their axes aligned with the displacement direction. According to this device, when the detection coils 2c and 2d are excited by excitation voltages of mutually opposite phases from an oscillator (not shown), magnetic fluxes Φ1°Φ2 passing through the cores 3b, 3c and the shaft l are formed, and 1111 bodies are generated. A voltage corresponding to the changed position of l is output as a sensor output from the midpoint M of the coils 2c and '2d.

In such a displacement detection device, when a disturbance magnetic field generation source exists near the displacement detector, the S/N ratio of the detector decreases due to the influence of the disturbance magnetic field. Therefore, in order to prevent the S/N ratio of the displacement detector from decreasing, measures such as increasing the distance between the detector and the source of the disturbance magnetic field, or inserting a magnetic wall between the detector and the source of the disturbance magnetic field are taken. It has been subjected.

(Problems to be Solved by the Invention) However, in the above-mentioned conventional device, by taking the measures described in 1, the overall structure of the device has to be enlarged, and the structure is not designed to be able to attach a magnetic wall. There was a problem that it was indispensable. In addition, in the case of one high-frequency disturbance magnetic field, it is difficult to reduce the influence even by taking the countermeasures described in J.

The present invention has been made to solve these conventional problems, and it not only makes the overall structure of the displacement detector compact, but also reduces the influence of disturbance high-frequency magnetic fields, and the S/N of the detector.
It is an object of the present invention to provide a non-contact type displacement detection device which aims to improve the displacement detection resolution by increasing the ratio.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a non-contact displacement detection system having a detector that detects the displacement of a detected object made of a magnetic material or a conductive material using magnetic changes. In the device, 01j
A non-contact device characterized by having a coil that faces the detected object and detects the displacement of the detected object, and a short-circuit current path provided in a plane perpendicular to the axis of the coil so as to surround the axis. A contact displacement detection device is provided.

(Function) When a disturbance magnetic field is applied, the magnetic field generated in response to the current induced in the short-circuit current path by the disturbance magnetic field kills the disturbance magnetic field, so it can be detected without the influence of the disturbance magnetic field. H can detect the displacement of the object to be detected.

(Example) Hereinafter, the present invention will be explained in detail based on the drawings.

FIG. 1 is a basic configuration diagram of a non-contact displacement detection device showing an embodiment of the present invention. For example, a detector C for detecting the amount of displacement of a detected object l made of a silicon steel plate has an E-shaped core 3 made of a silicon steel plate, for example, and an axis line n; It is composed of a detection coil 2 that is wound perpendicularly to the body 1a facing the detection body 1.

Further, at one end of the core 3, a loop-shaped stabilizing coil (short-circuit current path) 4 whose terminals are short-circuited has its axis aligned with the detection coil 2.

That is, it is disposed surrounding the core 3 so as not to interlink with the magnetic flux Φ generated by the coil 2. An alternating current is supplied to the detection coil 2 from a displacement detection device (not shown), and two closed circuits as shown in FIG. 1 are formed by magnetic flux Φ generated by the current.

When the detected object 1 is displaced in the direction toward or away from the detection coil 2, the magnetic flux Φ 11; The amount of displacement of the detected object 1 is detected from the change.

When an electromotive force is induced in the stabilizing coil 4 by a disturbance magnetic field, 1): Since the coil 4 is short-circuited, a current caused by the electromotive force flows, and the disturbance magnetic field is canceled by the current. A magnetic field is generated.

Therefore, the stabilizing coil 4 can protect the detection coil 2 from disturbance magnetic fields.

Next, the operation of the above embodiment will be explained. In normal times when there is no disturbance magnetic field, when the detected object 1 is displaced, the magnetic flux Φ changes according to the amount of displacement, and the change in the current flowing through the detection coil 2 that occurs in response to the change in the magnetic flux Φ causes a displacement (not shown). The displacement wind of the detected object j is detected by the detection device.

On the other hand, when the disturbance magnetic field is applied to the detection coil 2 and the stabilizing coil 4 covering the coil 2, the stabilizing coil 4
The lines of magnetic force interlink with each other, and an electromotive force is induced in the coil 4. However, since the coil 4 is short-circuited, a current due to the electromotive force flows through the coil 4, and the current causes the lines of magnetic force in mJ. Magnetic field lines are generated that offset the Therefore, the lines of magnetic force caused by the disturbance magnetic field do not interlink with the detection coil 2, and therefore the detection coil 2 is in a shielded state against the disturbance magnetic field, and the displacement amount of the detected object 1 is detected with a high S/N ratio. be able to.

At this time, the magnetic flux generated by the detection coil 2 does not interlink (penetrate) with the stabilizing coil 4.
Since a closed circuit is formed inside the coil, even if the magnetic flux of the closed circuit changes due to the displacement of the detected object l, the magnetic flux change for the stabilizing coil 4 will be plus or minus zero, and the magnetic flux will change due to the detection coil 2. There is no influence on the stabilizing coil 4, and therefore the detection coil 2 can reliably detect only changes in magnetic flux due to displacement of the detected object 1.

FIG. 2 shows a modification of the embodiment shown in FIG. The difference is that the coils 2a and 2b are wound so that their axes are perpendicular to the opposing body 1a of the object to be detected I, and both coils 2a and 2b are connected in series. The other configurations are the same as those of the first embodiment.

Next, the operation of this embodiment will be explained. Normally, the current flowing through the two detection coils 2a and 2b connected in series changes due to changes in the magnetic flux Φ that changes according to the amount of displacement of the detected object l, and the displacement of the detected object l is detected. Therefore, the amount of displacement of the object to be detected 1 can be detected with the same sensitivity as in the embodiment shown in FIG. 1 above.

- When a force or a disturbance magnetic field is applied, the detection coils 2a and 2b become shielded from the disturbance magnetic field due to the action of the stabilizing coil 4, similar to the embodiment shown in FIG. amount can be detected with a high S/N ratio.

Figure 3 shows the conventional device shown in Figure 4 with a stabilizing coil/l.
, 4 is provided, and 1-the above-mentioned 1st. As in the second embodiment, the stabilizing coils 4, 4 shield the detection coils 2c, 2d from the disturbance magnetic field, thereby responding to the amount of displacement of the shaft l without being affected by the disturbance magnetic field. The output is obtained from the midpoint M between the coils 2c, 2d.

The above-mentioned stabilizing coil 4 is made of a superconducting material (the smaller the resistance, the greater the canceling effect of the disturbance magnetic field, and the more effective it is to cancel the disturbance magnetic field), but it is also sufficient to short-circuit a coil made of a normal conductive material. The effect of this can be obtained.

Further, in the embodiment, an example of a coil in which a thin wire is wound multiple times as a stabilizing coil is shown, but a thin conductor may be formed into a cylindrical shape to serve as a stabilizing coil.

(Effects of the Invention) As described in detail below, the present invention provides a non-contact displacement detector having a detector that detects the displacement of a detected object made of a magnetic or conductive material using magnetic changes. In 11 devices,
1111 A coil that faces the detected object and detects the displacement of the detected object, and the @I in a plane perpendicular to the axis of the coil.
Since it is characterized by having a short-circuit current path provided so as to surround the t-line, it reduces the influence of a disturbance high-frequency magnetic field and increases the S/N ratio of the displacement detector. This excellent effect can be achieved.

[Brief explanation of the drawing]

Fig. 1 is a basic configuration diagram showing an embodiment of the J1 contact type displacement detection device of the present invention, Fig. 2 is a basic configuration diagram showing an embodiment of the J1 contact type displacement detection device of Mizuki JD Akira, and Fig. 3 The figure is number 4
A configuration diagram of a third embodiment in which a stabilizing coil is arranged in the conventional device shown in the figure is not shown, and No. 41 is a configuration diagram of the conventional device. l...Object to be detected, A...Detector, 2, 2a, 2b. 2c, 2d...Detection coil (coil), 4...Stabilizing coil (short circuit current path). Figure 1 Figure 2

Claims (1)

[Claims] 1. In a non-contact displacement detection device having a detector that detects the displacement of a detected object made of a magnetic material or an electric conductor using magnetic change, a sensor is used to detect the displacement of the detected object by facing the detected object. A non-contact displacement detection device characterized by having a coil to be detected and a short circuit current path provided in a plane perpendicular to the axis of the coil so as to surround the axis.