JPH046401A - Multichannel eddy-current type non-contact displacement detecting apparatus - Google Patents

Abstract

PURPOSE:To make it possible to prevent the interference between channels by providing switching circuits which sequentially select on of detecting coil in a cyclic pattern, and driving the selected detecting coil. CONSTITUTION:When a switching signal Sw1 is sent out, a switch 55 is switched to the side (a). An oscillator 50 operates with a detecting coil 4 of a sensor 21 as an operating coil. The oscillator output voltage is applied to a peak holding circuit 59 and stored in a latch circuit 61. Then, after the specified time, a switching signal Sw2 is sent out, and the oscillator 50 operates with a coil 4 of a sensor 22 as an operating coil. The oscillator output voltage is stored in a latch circuit 62. After the further specified time, a switching signal Sw3 is sent out and the oscillator 50 operates with a coil 4 of a sensor 23 as an operating coil. The oscillator output voltage is stored in a latch circuit 63. After the specified time, a switching signal Sw4 is generated by the similar way, and the oscillator output voltage is stored in a latch circuit 64. In this way, the data stored in the circuits 61 - 64 are read out at the same time and sent out into a control device.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is used to detect changes in the gap length between the rotating shaft and the magnetic bearing in high-speed rotating machines, etc. in which the rotating shaft is supported by a magnetic bearing. This invention relates to a multi-channel eddy current type non-contact displacement detection device used for.

[Conventional technology]

FIG. 2 shows a conventional eddy current type non-contact displacement detection device of this type. In the figure, l is a rotating shaft supported by a magnetic bearing. 21 to 24, and 25 to 28 are sensors, which have a configuration as shown in FIG.
Sensors 24 to 28 are arranged around one end of the rotating shaft 1 at predetermined intervals in the circumferential direction with the detection surfaces facing the rotating shaft 1, and the sensors 25 to 28 are arranged around the other end of the rotating shaft 1. , are arranged at predetermined intervals in the circumferential direction, with the detection coil surface facing the rotating shaft 1.

In FIG. 3, the sensor 21 is shown as a representative,
3 is the case, 4 is the detection coil, and the rotation axis 1 and the gap G
The voltage across the detection coil 4, which is magnetically coupled with a gap of approximately 0.3 to 1 mm, is taken out to the measurement circuit through an internal lead wire 5 and an external lead wire 6.

The detection coil 4 of each sensor 21 to 24 is as high as 5.6 mm.
An oscillation circuit 3 is connected to the oscillation circuits 31A to 34A via
The output of 1A and 33A is a comparison circuit (differential amplifier circuit) 41A
The outputs of oscillation circuits 32A and 34A to which the left and right pairs of sensors 22 and 24 are connected, respectively, are input to a comparison circuit (differential amplifier circuit) 41B. Similarly, each sensor 25-2
The detection coil 4 of 8 is connected to the oscillation circuits 31B to 34B via the leads 5.6, and the outputs of the oscillation circuits 31B and 33B, to which the upper and lower pairs of sensors 25 and 27 are respectively connected, are connected to a comparison circuit (differential amplification). circuit) oscillation circuit 32B to which left and right pairs of sensors 26 and 28 are respectively connected to 42A;
The outputs of 34B and 34B are input to a comparison circuit (differential amplifier circuit) 42B.

In the figure, amp indicates an amplifier.

These oscillation circuits 31A to 34A, 31B to 34B are the fourth
As shown in the figure, Colpitts oscillator O8C and filter FI
Each Colpitts oscillator O5C is tuned to the same oscillation frequency (several hundred KHz to several MHz) f. R1
-R4 is a resistance, C.

~C1 is a capacitor, and ■ is a voltage.

In Fig. 4, ro. is the resistance bone and inductance of the rotating shaft 1, r, and is the detection coil 4 of the sensor 21.
resistance and inductance, M is mutual inductance, ω
=2πf (f: oscillation frequency), and the impedance Z seen from the oscillator side (hereinafter referred to as the impedance of the detection coil) is as follows.

In this configuration, when the rotating shaft 1 is displaced in its radial direction, the impedance Z changes, the oscillation voltage of the Colpitts oscillator oSC changes, and the oscillation circuits 31A to 34A,
Since the oscillation voltages of 31B to 34B change, the outputs of the differential amplifier circuits 41A to 42B change, and the
1-23, sensor 25-27 direction) and the Z-axis direction (sensor 22-24, sensor 26-28 direction), the change in the gap G can be known.

[Problem to be solved by the invention]

In this way, in a multi-channel type device in which multiple sensors are placed close together and each oscillator is tuned to the same frequency and driven, it is difficult to completely eliminate interference between the channels, and the oscillation circuit operates in constant oscillation mode. As a result, the interference voltage (voltage at the beat frequency) is superimposed on the oscillation voltage, which may reduce detection accuracy, which limits the number of sensors that can be used, and also increases the temperature. Temperature compensation is performed to prevent fluctuations in the oscillation frequency caused by this, and an oscillation circuit is provided for each sensor to tune the oscillation frequency. As the number of sensors increases, the circuit configuration becomes complex, making it difficult to downsize. This is difficult and requires special measures to suppress the mutual interference for each channel.

There is also a method of shifting the oscillation frequencies of each oscillator to such an extent that the above-mentioned mutual interference does not occur, but this method is the same as the above case in that the same number of oscillators as sensors are used.

The present invention has been made to solve the above problems, and provides a multi-channel eddy current type non-contact displacement detection device that can be made smaller than conventional ones and can prevent interference between chamfers. The purpose is to provide.

[Means to solve the problem]

In order to achieve the above-mentioned object, the present invention includes a plurality of sensors each having a detection coil arranged opposite to a target object with a gap therebetween, and processes the output of an oscillator using the detection coil as an operating coil to perform the above-mentioned A multi-channel eddy current type non-contact displacement detection device for detecting displacement of an object is provided with a switching circuit that sequentially and cyclically selects one of the detection coils mentioned above, and is configured to drive the selected detection coil. It is something.

In the second aspect of the present invention, the number of oscillators is one, and the switching circuit selects one of the detection coils and selectively connects it to the oscillator.

In claim 3, the switching circuit sequentially and cyclically selects and operates the oscillators connected to each detection coil.

The configuration was selected.

[Effect]

In the present invention, while one sensor is being driven, the other sensors are inactive, so the above-mentioned mutual interference does not occur.

〔Example〕

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

In FIG. 1, 50 is an oscillator O3C (oscillation frequency ro) common to each of the sensors 2I to 24, and the sensors 21 to
The detection coil 4 of No. 24 is connected to the changeover switch 55 of the changeover circuit A.
It is connected to the oscillator 50 via 58. 51 to 54 are resistors, which are connected to the sensor 2 via changeover switches 55 to 58.
Each of the detection coils 1 to 24 is connected in parallel. 5
A peak hold circuit 9 receives the oscillation voltage of the oscillator 50 and holds the maximum amplitude absolute value of the oscillation voltage. 60 is an A/D converter that converts the hold value of the pic-hold circuit 59 into a digital value. 61-6
A latch circuit 4 latches the output of the A/D converter 60 when each of the sensors 21 to 24 is connected to the oscillator 50. D/A converters 65 to 68 convert the data read from the latch circuits 61 to 64 into analog signals and send them to a control device (not shown).

50A is an oscillator whose oscillation output (oscillation frequency f
, <f,) are input to the timing generator 69. The timing generator 69 generates a switching signal S synchronized with the oscillation cycle of the oscillator 50A. 1 to S1.14 are sequentially sent to the changeover switches 55 to 58 cyclically after a fixed time ΔT, and latch timing signals t□ to t are delayed by a fixed time ΔT2 from the switching signals 5w1-'-3W4, respectively.
j14 is sent to latch circuits 61-64. Oscillator 50
A and the timing generator constitute a timing generation circuit B.

In this configuration, when the switching signal SWI is sent out, the changeover switch 55 is switched to the a side, the detection coil 4 of the sensor 21 is connected to the oscillator 50, and the oscillator 50 oscillates using the detection coil 4 as an operating coil. At this time, the changeover switches 56-58 are not switched to the b side, and the detection coils 4 of the other sensors 22-24 are connected in parallel to the resistors 52-54 via the changeover switches 56-58. In addition, the switching signal S, 1. After a delay of ΔT2 hours from the occurrence of
1 is given a launch signal t□. This ΔT2 time is the time required for the output of the oscillator 50 to stabilize after the changeover switch 55 is turned to the a side.

The oscillation voltage of the oscillator 50 is input to a peak hold circuit 59, and the peak hold circuit 59 holds the maximum amplitude absolute value of the oscillation voltage. This hold value is converted into a digital value and stored in the latch circuit 61. When the reading operation of the launch circuit 61 ends after the switching signal SWl is generated, the switching signal SW+ disappears and the predetermined time Δ
After T1 has elapsed, a switching signal S8□ is sent out. This time ΔT1 is the time required for the energy stored in the detection coil 4 to be completely released. As a result, the changeover switch 55 is switched to the b side, and the energy stored in the detection coil 4 of the sensor 21 is released to the resistor 51, and the changeover switch 56 is switched to the a side, and the detection coil 4 of the sensor 22 is switched to the a side. is connected to the oscillator 50. The oscillator 50 then oscillates using the detection coil 4 of the sensor 22 as an operating coil,
The oscillation voltage is stored through the A/D converter 60 in the latch circuit 62 receiving the latch timing signal t□. This latch timing signal t0 is the switching signal S, 42
Occurs 612 hours after the occurrence of. Switching signal Sll!
When the reading operation of the latch circuit 62 is completed after the occurrence of , the switching signal 551g disappears, and the switching signal 51113 is sent out after a predetermined time ΔT has elapsed. This results in
The changeover switch 56 is switched to the b side, and the energy stored in the detection coil 4 of the sensor 22 is released to the resistor 52, and the changeover switch 57 is switched to the a side, and the detection coil 4 of the sensor 23 is switched to the oscillator 50. connected to. The oscillator 50 then oscillates using the detection coil 4 of the sensor 23 as an operating coil, and the oscillation voltage is passed through the A/D converter 60 to the latch circuit 6 receiving the latch timing signal t.
3. Similarly, after 611 hours, the switching signal S, 44 is generated, the detection coil 4 of the sensor 24 is connected to the oscillator 50, and the oscillation voltage is stored in the latch circuit 64 through the A/D converter 61.

The data stored in the latch circuits 61-64 in this manner are simultaneously read out, converted into analog values by the D/A converters 61-64, and then sent to a control device (not shown).

In this embodiment, only one oscillator is used, and one of the detection coils is always selected and driven by this oscillator rather than at the same time, so there is no mutual interference between channels.

Furthermore, this embodiment has the advantage that, in addition to the oscillator 50, there is no need to provide an oscillator to which the detection coil is connected.

In the above embodiment, one oscillator is used and a plurality of detection coils are sequentially selected. However, as in the conventional example, an oscillator is provided for each sensor, and the switching circuit A sequentially and cyclically selects a plurality of detection coils. A similar effect can also be obtained by selecting one oscillator to operate during a period of time, and stopping the other oscillators during this period.

Further, in the above embodiment, the hold value of the peak hold circuit 59 is stored in the latch circuits 61 to 64 every day, but the hold value of the peak hold circuit 59 is directly sampled and inputted to the control device. In some cases, it may be processed.

〔Effect of the invention〕

As explained above, since the present invention operates each sensor sequentially and cyclically, interference between channels can be completely prevented, and there is no need to provide a means to prevent or suppress interference. Therefore, the device can be made smaller and less expensive, and the detection accuracy can also be improved due to the absence of the above-mentioned interference.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an embodiment of the present invention, Fig. 2 is a circuit diagram showing a conventional displacement detection device, Fig. 3 is a sectional view showing the configuration of the sensor, and Fig. 4 is the oscillation circuit in Fig. 2. FIG. 2 is a circuit diagram showing an example. 21-24-sensor, 50-oscillator, 50A-oscillator, 51-54-resistance, 55-58-selector switch, 59
-Peak hold circuit, 61 to 64 -Latch circuit, 6
9--timing orderer, A switching circuit, B-timing generation circuit, second shaft

Claims (3)

[Claims] (1) Equipped with a plurality of sensors having detection coils arranged opposite to the target object across a gap, and detecting the displacement of the target object by signal processing the output of an oscillator using the detection coils as operating coils. In a multi-channel eddy current type non-contact displacement detection device, a switching circuit for sequentially and cyclically selecting one of the above-mentioned sensors and a timing generation circuit for controlling this switching circuit are provided, and the detection coil of the selected sensor is A multi-channel eddy current type non-contact displacement detection device characterized by driving. (2) The multi-channel eddy current type non-contact according to claim 1, wherein the number of oscillators is one, and the switching circuit sequentially and cyclically selects one of the sensors and connects it to the oscillator. Displacement detection device. (3) The multi-channel vortex according to claim 1, wherein the plurality of sensors and the detection coil of each sensor are connected to an oscillator, and the switching circuit sequentially and cyclically selects and operates the oscillators. Current type non-contact displacement detection device.