JPH045525A - Noncontact type displacement detector - Google Patents

Abstract

PURPOSE:To accurately detect the quantity of displacement of a body to be detected by arranging two detectors opposite each other as for the center of the body, connecting the coils of the detectors in series and applying opposite- phase AC voltages across the coils, and taking a detection signal out of the connection point between the coils. CONSTITUTION:An oscillator 4 supplies exciting voltages V1 and V2 to the coils 2a and 3a. When the body 1 is displaced, the coils 2 and 3 are varied in inductance with the displacement quantity and, therefore, vary impedance. The sensor output V0 is taken out of the connection point A between the coils 2a and 3a by dividing the exciting voltages V1 and V2 at the impedance ratio of the coils 2a and 3a, and rectified synchronously by the synchronous rectifier 6 of a converter 5 to generate a synchronous rectification output VR. The output VR is inputted to an LPF 7, which cuts its carrier frequency component to generate a displacement detection output VC.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a non-contact displacement detection device used for vibration control of shaft vibration measuring instruments, magnetic bearings, and the like.

(Prior art) Conventional non-contact displacement detection devices use, for example, eddy current to detect the displacement of a detected object, but there are output fluctuations due to temperature changes in the displacement detector and the detected object. Ta. In order to offset this variation, two displacement detectors are placed facing each other on two surfaces of the object to be detected, and the two detection signals taken out from the two detectors are combined into one detection signal using an arithmetic circuit. I was trying to convert it into a signal.

(Problem to be Solved by the Invention) Since the conventional non-contact displacement detection device has the above-mentioned structure, two detection signals taken out from the two displacement detectors are combined into one detection signal by an arithmetic circuit. Therefore, there were problems in that the circuit configuration was complicated and the number of wires for connecting each detector and the arithmetic circuit was large, resulting in high cost.

In addition, when using the displacement detection device in special environments such as vacuum or active gas atmosphere, the object to be detected or the detector should be covered with a conductor such as stainless steel foil to prevent gas generation from bearing grease and corrosion. Measures will be taken to enclose the area. in this case,
With conventional non-contact displacement detection devices that utilize eddy currents, it has been impossible to detect displacement of an object to be detected.

Therefore, in order to solve the above-mentioned problems, the present invention has a structure in which two detectors are used to offset the fluctuations due to temperature, a single detection signal is output, and the detection object or the detector is It is an object of the present invention to enable displacement of a detected object to be detected even when surrounded by conductive foil.

(Means for Solving the Problems) According to the present invention, the above-mentioned object is to provide a non-contact displacement detection device for detecting displacement of a detected object, in which one of two detectors each having a winding is The windings of the two detectors are arranged opposite to one surface of a detected object made of a magnetic material, and the other is arranged opposite to another surface opposite to the first surface with respect to the center of the detected object. This is achieved by connecting the two detectors in series, applying an excitation AC voltage of opposite phase to both ends of each winding, and taking out the output from the connection point of the windings of the two detectors and using it as a detection signal. .

(Function) An excitation alternating current of opposite phase is applied to both ends of each of the series-connected windings of two detectors arranged facing each other on two opposite sides of the object to be detected, which is made of a magnetic material, with respect to its center. Apply voltage. The difference in voltage drop in each winding due to the inductance of the two windings is extracted as a single detection signal from the connection point of both windings.

(Example) First, the basic configuration of the non-contact displacement detection device of the present invention will be explained as follows.
This will be explained with reference to FIGS. 6 to 6.

As shown in FIG. 4, the displacement detection device of the present invention basically consists of two windings Ml and M2, which form first and second detectors and are connected in series. Line M l.

An oscillator A connected to the windings M+ and M2 so as to apply excitation alternating current voltages Vl and V2 to M2 respectively in opposite phases.
C1, AC2, and the first and second detectors are arranged facing each other on two surfaces of an object to be detected (not shown) made of a magnetic material.

The windings M1 and M2 are designed to have the same magnetic pole area and magnetic permeability.

Letting V be the voltage applied across the windings Ml and M2 of the first and second detectors, it is expressed as V=Vl-V2.

If the angular frequency of the alternating current voltage is Q), then the winding Ml.

The impedance Zl, Z2 of M2 is Z+=ωL1, Z
2=ωL2. Here, Ll and L2 are windings M t
.

This is the inductance of M2. Therefore, the winding M 1゜M
If the voltage drops at 2 are VLI and VL2, then the output (hereinafter referred to as "sensor output") Vo at the connection point of the windings M1 and M2 is given by:

Next, the influence of the positional relationship between the magnetic pole of the winding of the detector and the detected object 1 on the sensor output Vo will be described.

In FIG. 5, the distance between the magnetic poles of the windings Ml and M2 and the detected object l is g'+g2. When the detected object l is located at the center between the magnetic poles (the position shown in FIG. 5), that is, g 1=
When g2=ho, the area of the magnetic pole is S and the magnetic permeability is subtracted, so L+=L2, and the sensor output VO at this time is as follows.

Next, when the detected object 1 moves from the position shown in FIG. 5 to the M2 side by an amount of X, that is, when gl:>gz, the sensor output Vo at this time is 1 moves from the position shown in FIG. 5 to the M1 side by X, that is, when g 1 (g 2), the sensor output Vo at this time is expressed as follows.

In this way, by combining two magnetic poles, the voltage V applied to both ends of the windings Ml and M2 is constant, so the sensor output VO can take a value proportional to the amount of movement X of the detected object. Recognize.

Furthermore, even if a non-magnetic conductor such as stainless steel foil is interposed between the magnetic pole and the detected object 1, the sensor output VO is not related to changes in Ll and L2 as described above. takes a value proportional to the amount of movement X of the detected object 1.

Next, the effect on the sensor output Vo when the detected object and the detector are deformed due to temperature changes will be described.

In FIG. 6, for example, if we consider the case where the amount of deformation of the detected object l is y, the inductance of the winding when the detected object is located at the center between the magnetic poles, that is, g1=g2:=hO. Ll and L2 are expressed as follows.

Therefore, L1=L2, and the sensor output VO is (2) o=L1+L2 (Ll-L2)=O.

From this, even if the detected object l is deformed due to a temperature change, the changes in the inductance of the windings Ml and M2 are canceled out, and the resensor output Vo is not equally affected.

Next, embodiments of the present invention will be described in detail.

FIG. 2 is a block diagram of the overall configuration of a non-contact displacement detection device according to an embodiment of the present invention. As shown in the figure,
Windings 2a and 3a of two detectors 2 and 3 are arranged opposite to two surfaces 1a and It) of a detected object 1 having a circular cross section, respectively, and the windings 2a and 3a are connected to each other in series. , both ends of which are connected to an oscillator 4, from which excitation alternating current voltages (hereinafter referred to as "excitation voltages") vl having mutually opposite phases are applied.

v2 is applied. The oscillator 4 is also connected to the synchronous rectifier 6 of the converter 5 and supplies the latter with a synchronously rectified radical signal Rer of the same frequency as the excitation voltage.

A winding 2a marked mj is connected to the sensor output input terminal of the synchronous rectifier 6.
, 3a are connected to supply the sensor output VO. The output of the synchronous rectifier 6 is connected to a low-pass filter of the converter 5.

The operation of the non-contact displacement detection device having the above configuration will be explained with reference to FIG. 3. The oscillator 4 supplies excitation voltages Vl and V2 shown in FIG. 3(a) to the windings 2a and 3a, respectively. When the detected object 1 is displaced (FIG. 3(b)), the inductance of the windings 2 and 3 changes according to the amount of displacement, and therefore their impedance changes. The sensor output Vo is taken out from the connection point of the windings 2a and 3a as an output obtained by dividing the excitation voltages Vl and V2 applied to both ends of the windings 2a and 3a by the impedance ratio of the windings 2a and 3a (Fig. 3). (C))
, to the synchronous rectifier 6 of the converter 5. Synchronous rectifier 6
synchronously rectifies the inputted sensor output Vo using the synchronous rectification reference signal Ref from the oscillator 4 as a reference, and outputs it as a synchronous rectification output vR (FIG. 3(d)). The low-pass filter 7 cuts the carrier frequency of the input synchronous rectification output vR and outputs the output as the displacement detection device output VC (FIG. 3(e)).

FIG. 1 is a diagram showing in detail the arrangement of the detected object 1 and the detectors 2 and 3 shown in FIG. The outer periphery of the shaft l as the object to be detected”
The cores 2b and 3b of the detector 2.3 are disposed facing each other on the diametrically opposite surfaces 1a and lb of the detector 2.3.
3a and 3a are wound with their axes perpendicular to the opposing sides 1a and +b.

The winding 2a, by the excitation voltage Vl, 'V2 from the oscillator 4,
3a is excited, magnetic flux φ1.3a passes through cores 2b, 3b and shaft l. φ2 is formed, and the sensor output Vo of the voltage according to the amount of displacement of the shaft body l is the winding 2a.

It is output from connection point A of 3a.

FIG. 7 shows a modification of the embodiment shown in FIG. 1, which is different from the embodiment shown in FIG.

The difference is that the cores 2b and 3b are wound in parallel to 1b.

FIG. 8 is a diagram showing the arrangement of the detected object l and the detectors 2 and 3 according to another embodiment of the present invention. This embodiment is shown in FIG.
In the embodiment shown in FIG.
Detector 2 is placed inside the object 1 to be detected.
3 is arranged.

As shown in FIG. 8, the object 1 to be detected consists of a hollow cylindrical body, the cores 2b and 3b are integrally formed from a common single member, and two Surface 1a
, lb, respectively. - the windings 2a, 3a are wound around the cores 2b, 3b in such a way that their axes are perpendicular to the opposing surfaces 1a, lb, respectively;

FIG. 9 is a diagram showing a modification of the embodiment shown in FIG.
Each core 2b has a different shape.

3b has two winding parts 2b1, 2b2; 3b+, 3b2, and these winding parts 2b+, 2b2; 3bt.

The difference is that windings 2a and 3a are respectively wound around 3b2.

FIG. 10 shows an embodiment in which the detected object 1 is surrounded by a conductive foil 9. This embodiment has the same structure as the embodiment shown in FIG.
．． A conductive foil 9 having a thickness of 1 to 0.2 mm is arranged to cover the outer periphery of the shaft I so as to be interposed between the shaft 1 of the object to be detected and the detectors 2 and 3.

In this configuration, the excitation voltages Vl, V2 from the oscillator 4
When the windings 2a and 3a are excited, the cores 2b and 3
The magnetic flux φ1.b generated at φ2 passes through the conductor foil 9 and passes through the detected object 1, forming a magnetic path similar to that shown in FIG. As a result, a sensor output VD of a voltage corresponding to the amount of displacement of the detected object (shaft body) 1 is output from the connection point A of the windings 2a and 3a. In this way, since the present invention does not utilize eddy currents, it is possible to detect the amount of displacement of the detected object 1 without being equally affected by the presence of conductive foil.

FIG. 11 shows a configuration similar to that of the embodiment shown in FIG. 7, in which the detected object 1 is surrounded by a conductive foil 9.

With this configuration as well, a magnetic path similar to that shown in FIG.

12 shows a configuration similar to the embodiment shown in FIG. 8, with the detectors 2 and 3 surrounded by conductive foil, and FIG. 13 shows a configuration similar to the embodiment shown in FIG. 8 and 9. In these configurations, magnetic paths similar to those shown in FIGS. 8 and 9 are formed, and the amount of displacement of the detected object 1 is determined despite the presence of the conductive foil. can be detected.

FIG. 14 shows yet another embodiment, and while each of the above-mentioned embodiments has a uniaxial detection configuration that detects the displacement of l shaft bodies as objects to be detected, this embodiment has a plurality of It has a multi-axis detection configuration that detects the displacement of the shaft body.

In FIG. 14, detector windings 2a and 3a connected in series, similar to those in each of the previously described embodiments, are arranged facing each other on each of the first to Nth shaft bodies as objects to be detected (not shown). Ru. The detector windings 2a and 3a of the first to Nth shaft bodies are connected in parallel to each other. Detector windings 2a of the first to Nth shaft bodies connected in parallel.

An oscillator 4 is connected to 3a to apply an excitation voltage to the detector winding. The junction of the detector windings 2 a + 3 a of each column is connected to a respective converter 5 and supplies the junction output Vo. The converter 5 can be configured in the same manner as the uniaxial detection configuration described above, and outputs the output VC of the displacement detection device.

In this way, when the non-contact displacement detection device of the present invention has a multi-axis detection configuration, the detector windings in each row can share a single oscillator, which further reduces the number of wiring lines and further reduces costs. can be achieved.

(Effects of the Invention) As explained above, the non-contact displacement detection device according to the present invention directs one force of two detectors each having a winding to one surface of a detected object made of a magnetic material. The windings of the two detectors are connected in series, and the other is arranged facing the other surface opposite to the first surface with respect to the center of the detected object, and the windings of the two detectors are connected in series, and the opposite ends of each winding are connected to each other in series. By applying a phase excitation AC voltage, the output is taken out from the connection point of the windings of the two detectors and used as a detection signal, so not only is there no output fluctuation due to temperature, but the arithmetic circuit is It is unnecessary, the 4° configuration is simple, and the number of wiring lines can be reduced, resulting in excellent effects such as cost reduction. Furthermore, since the configuration detects changes in magnetic flux rather than using eddy currents, the amount of displacement of the detected object can be accurately detected even when a conductive foil is interposed between the detected object and the detector.

[Brief explanation of drawings]

FIG. 1 is a layout diagram showing a uniaxial detection configuration according to an embodiment of the present invention, FIG. 2 is a block diagram showing an embodiment of the present invention, and FIG. 3 is a waveform diagram of signals in each part of FIG. Fig. 4 is a basic configuration diagram of the non-contact displacement detection device of the present invention, Fig. 5 is a diagram showing a state in which the object to be detected is at the center between the magnetic poles, and Fig. 86 is a state in which the object to be detected is displaced due to temperature change. FIGS. 7 to 13 are layout diagrams showing other embodiments of the uniaxial detection configuration according to the present invention, and FIG. Figures 8 and 9 show examples in which the detector is placed inside the object to be detected, and Figures 10 to 13 show examples in which a conductive foil is interposed between the detector and the object to be detected. , FIG. 14 is a layout diagram showing an embodiment of the multi-axis detection configuration according to the present invention. 1... Detected object, 2, 3... Detector, 2a, 3a.
...Detector winding, 4...Oscillator, 5...Converter, 6
...Synchronous rectifier.

Claims (1)

[Claims] 1. In a non-contact displacement detection device that detects the displacement of a detected object, one of the two detectors each having a winding is placed opposite to one surface of the detected object made of a magnetic material, and the other The windings of the two detectors are arranged opposite to each other on another surface opposite to the one surface with respect to the center of the detected object, and the windings of the two detectors are connected in series;
A non-contact displacement detection device characterized in that an excitation AC voltage of opposite phase is applied to both ends of each winding, and an output is taken out from a connection point of the windings of the two detectors and used as a detection signal.