JP2645243B2 - Non-contact displacement sensor and displacement detection method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a non-contact displacement sensor for detecting a displacement of an object in a non-contact state, and more particularly to a displacement sensor of an inductance change detection type.

(Prior Art) In recent years, magnetic bearings that support a rotating shaft in a non-contact state using magnetic attraction have been proposed, and attention has been paid to the possibility of ultra-high-speed rotation. This magnetic bearing utilizes a non-contact displacement sensor that detects displacement of an object in a non-contact state, and detects a displacement of the rotating shaft that detects an electromagnet that generates a magnetic attractive force for supporting the rotating shaft with the displacement sensor. In this way, non-contact support of the rotating shaft is realized by controlling based on the following.

As a non-contact displacement sensor used for such a magnetic bearing or the like, an inductance change detection type displacement sensor is widely known because of its features such as a wide measurement range and a large output. This inductance change detection type displacement sensor uses an object as a part of a closed magnetic circuit of a coil containing an iron core, and when the gap between the coil and the object changes due to the displacement of the object, the magnetic resistance of the closed magnetic circuit changes. Since the inductance of the coil changes, the change in the inductance is detected by supplying an alternating current of a predetermined frequency to the coil and measuring the voltage across the coil to detect the displacement of the object.

(Problems to be Solved by the Invention) In the conventional non-contact displacement sensor of the inductance change detection type as described above, in consideration of the above-mentioned correspondence to the ultra-high-speed rotation of the magnetic bearing, in order to achieve the ultra-high-speed rotation, In order to improve the bending resonance point of the rotating shaft by shortening the rotor length of the magnetic bearing, the distance between the motor and the electromagnets for the bearing and the displacement sensor is reduced. Since the windage of the rotating shaft increases with the rise of the motor shaft, a high-output motor is required, so that the electromagnetic noise for the displacement sensor is greatly increased, and a countermeasure is required.

Further, in the conventional non-contact displacement sensor, the core of the detection coil is usually made of a silicon steel plate, and has a characteristic that the inductance decreases as the frequency increases as shown in FIG. For this reason, the inductance changes due to the frequency change of the input signal due to the fluctuation of the power supply voltage or the modulated wave generated by the displacement of the object, and the detection accuracy is reduced.

In view of the above, the present invention is to improve the resistance to electromagnetic noise and improve the frequency characteristics to improve the detection accuracy in the non-contact displacement sensor of the inductance change detection type.

(Means for Solving the Problems) In order to solve the above problems, the present invention provides a detection coil in which a winding is wound around an outer periphery of a substantially U-shaped core formed by laminating thin plates of an amorphous alloy having a small high-frequency loss. An oscillator that supplies an AC output to one end of the winding of the coil; and a detector that detects an output at both ends of the winding shaft of the coil that is generated by supplying an AC output from the oscillator to the coil. And a filter that smoothes and detects the output from the detector, grounds the other end of the winding shaft of the coil, and sets the output impedance of the oscillator to the input impedance of the winding of the coil. In order to arrange both ends of the core of the coil so as to provide a gap ε with respect to the object, the magnetic resistance of ε is set to the magnetic resistance of the core and the magnetic resistance of the object. And the displacement of the object is changed by the inductance with respect to the frequency change of the frequency-to-inductance characteristic of the coil in the closed magnetic circuit formed by the object, the core of the coil, and the air gap ε. A non-contact displacement sensor for detecting a displacement of the object as an inductance displacement of the closed magnetic path by setting a frequency of a signal to be supplied to the coil near a center of a frequency region in which a change does not occur.

A coil formed by laminating a thin plate of an amorphous alloy having a small high-frequency loss and having a winding wound around an outer periphery of a substantially U-shaped core; The output of both ends of the winding is detected by a detector, the output from the detector is smoothed by a filter, and the inductance is detected, the other end of the winding of the coil is grounded, and the oscillator is The output impedance of the coil is set to be larger than the input impedance of the winding, and the magnetic resistance of the core of the coil and the air gap ε having a value larger than the magnetic resistance of the object are provided, Inductance is applied to the frequency change of the frequency-to-inductance characteristic of the coil obtained by arranging both ends of the core of the coil with respect to an object to form a closed magnetic circuit. There are those according to displacement of the object by setting the frequency of the signal supplied to the coil in the vicinity of the center of the frequency range that does not change in the displacement detection method characterized by detecting a change in inductance of the closed magnetic circuit.

(Function and Effect of the Invention) In the present invention configured as described above, the signal supplied to the detection coil by the inductance detection means needs to be set very high with respect to the frequency of the displacement of the object.
By configuring the core of the detection coil using an amorphous alloy having a small high-frequency loss, the ratio of the magnetoresistance due to the gap between the detection coil and the target object increases in the total magnetic resistance of the closed magnetic circuit formed by the detection coil. Therefore, the sensitivity as a sensor is improved, and the influence of the electromagnetic nozzle, which is a disturbance, can be reduced. In addition, the frequency-to-inductance characteristics of a detection coil using an amorphous alloy for the core have a region where the inductance does not change with frequency change. Therefore, set the frequency of the signal supplied to the detection coil near the center of this frequency region. Accordingly, even if a modulated wave or the like due to displacement of the object occurs, the inductance does not change, the frequency characteristics of the sensor become flat, and the detection accuracy is improved.

(Embodiment) FIG. 1 is a diagram showing an embodiment of the present invention. In FIG. 1, a detection coil 1 has a winding 3 wound around an outer periphery of a substantially U-shaped core 2 formed by laminating thin sheets of an iron-based amorphous alloy having a small high-frequency loss, and displacement is detected. The core 2 is fixedly arranged with the both ends of the core 2 facing the object 4. Reference numerals 5, 6 and 7 denote an oscillator, a detector and a filter, respectively, which constitute the inductance detecting means. The AC output of the oscillator 5 is supplied to one end of the winding 3 of the detection coil 1. The other end of the winding 3 is grounded in order to measure the voltage at both ends thereof, and is connected to a detector 6 at one end to which the AC input is supplied. Is detected. The output of the detector 6 is supplied to a low-pass or notch or a filter 7 in which both are combined, and only the displacement component of the object 4 is extracted.

Here, the output impedance of the oscillator 5 is larger than the input impedance of the winding 3, and the AC output from the oscillator 5 is a constant current output. At least a portion of the object 4 facing the core 2 is made of a magnetic material, and the detection coil 1 forms a closed magnetic path passing through the core 2, a gap ε with the object 4, and the object 4. In this closed magnetic circuit, the magnetic resistance of the air gap ε is larger than that of the core 2 and the object 4 made of a magnetic material. When the air gap ε changes due to the displacement of the object 4, the magnetic resistance in the closed magnetic circuit changes greatly. The inductance of the coil 1 changes. This inductance change is detected by applying an AC constant current to the winding 3 by the oscillator 5 as described above, detecting the voltage between both ends of the winding 3 by the detector 6, smoothing the AC voltage by the filter 7, and displacing the displacement component of the object 4. Only detect.

At this time, the oscillation frequency of the oscillator 5 needs to be set to a frequency sufficiently higher than the frequency of the displacement of the object 4 to be detected. On the other hand, when the detection coil 1 having the core 2 made of an iron-based amorphous alloy is used, as shown in FIG. 2, the inductance flat region where the inductance does not change and remains almost constant with respect to the frequency change in the high frequency region. The existence has been confirmed by experiments. Therefore, in this embodiment, the oscillation frequency of the oscillator 5 is set near the center of the flat inductance region.

In the above configuration, since the core 2 is made of an amorphous alloy having a small high-frequency loss, when a high-frequency AC current is supplied from the oscillator 5 to the winding 3, the magnetic material in the closed magnetic circuit formed by the detection coil 1 is provided. Part (ie,
Since the increase in the magnetic resistance of the core 2) is remarkably suppressed, the magnetoresistance component due to the gap ε between the core 2 and the object 4 in the total magnetic resistance of the closed magnetic circuit is large, and the inductance due to the displacement of the object 4 is large. The change increases, and the sensitivity as a sensor improves. In addition, by setting the oscillation frequency of the oscillator 5 in a flat inductance region, which is a frequency characteristic peculiar to the amorphous alloy core 2 which does not exist in the frequency characteristics of the conventional silicon steel sheet core (see FIG. 3), The inductance becomes substantially constant even for the modulated wave caused by the displacement of No. 4, the frequency characteristics of the sensor become good, and the detection accuracy is improved. As described above, according to the present embodiment, the sensitivity of the non-contact displacement sensor can be improved, the frequency characteristics can be flattened, and the detection accuracy can be improved. It can respond to the change.

Note that the sensitivity of the sensor can be further improved by using an amorphous alloy for a portion of the object where the displacement is detected, where the closed magnetic path is formed by the detection coil. In the above embodiment, the displacement of the object is detected by a single detection coil. However, the present invention may be applied to a displacement sensor having a configuration in which two or more known detection coils are bridge-connected (one of which may be a dummy). Has a similar effect. Further, in the above-described embodiment, an AC constant current is supplied to the detection coil to detect the voltage at both ends. However, the detection coil may be driven with the AC constant voltage to detect a current flowing through the detection coil. Further, the filter 7 is not necessarily required for control.

[Brief description of the drawings]

FIG. 1 is a block diagram of one embodiment of the present invention, FIG. 2 is a diagram showing frequency versus inductance characteristics of one embodiment of the present invention,
FIG. 3 is a diagram showing frequency versus inductance characteristics of a conventional non-contact displacement sensor. DESCRIPTION OF SYMBOLS 1 ... Detection coil, 2 ... Core, 3 ... Winding, 4 ... Target object, 5 ... Oscillator, 6 ... Detector, 7 ... Filter.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Midorio Okada 1-1-1, Showa-cho, Kariya-shi, Aichi Japan Inside Denso Co., Ltd. (72) Inventor Shinzo Ito 1-1-1, Showa-cho, Kariya-shi, Aichi Japan Japan Denso Stock In-company (56) References JP-A-50-80157 (JP, A) JP-A-55-33607 (JP, A) JP-A-56-87816 (JP, A)

Claims (2)

(57) [Claims] 1. A detection coil having a winding wound around a substantially U-shaped core formed by laminating thin sheets of an amorphous alloy having a small high-frequency loss, and an AC output supplied to one end of the winding of the coil. An oscillator; a detector for detecting an output from both ends of the winding shaft of the coil generated by supplying an AC output from the oscillator to the coil; and a filter for smoothing and detecting the output from the detector. And the other end of the winding shaft of the coil is grounded, the output impedance of the oscillator is set to be larger than the input impedance of the winding of the coil, and both ends of the core of the coil are objects. In providing the air gap ε, the magnetic resistance of the ε is set to a value larger than the magnetic resistance of the core and the magnetic resistance of the object, and the displacement of the object is The coil is supplied to the coil near the center of the frequency region where the inductance does not change with respect to the frequency change of the frequency-to-inductance characteristic of the coil in the closed magnetic circuit formed by the object, the core of the coil, and the air gap ε. A non-contact displacement sensor which detects a displacement of the object as an inductance displacement of the closed magnetic circuit by setting a frequency of a signal. 2. An AC output is supplied by an oscillator to one end of a winding of a detection coil in which a winding is wound around an outer periphery of a substantially U-shaped core formed by laminating thin sheets of an amorphous alloy having a small high-frequency loss. The output of both ends of the winding of the coil generated by the detector is detected by a detector, and the output from the detector is smoothed by a filter to detect the inductance, and the other end of the winding of the coil is grounded. And a gap that sets the output impedance of the oscillator to be larger than the input impedance of the winding of the coil, and has a value larger than the magnetic resistance of the core of the coil and the magnetic resistance of the object. ε is provided, and both ends of the core of the coil are arranged with respect to an object to form a closed magnetic circuit. Displacement detection method and detecting inductance of the displacement of the object by setting the frequency of the signal supplied to the coil in the vicinity of the center of the frequency range that does not change as a change in inductance of the closed magnetic circuit.