JPS5950304A - Displacement measuring device - Google Patents

Abstract

PURPOSE:To eliminate influence of a sensitivity drop portion of a detecting coil, and to measure exactly and with high accuracy the displacement in the axial direction of a rotating body, by correcting the sensitivity drop portion of the detecting coil, which is contained in a measuring signal, by correcting operation part. CONSTITUTION:A synchronizing rectifying part 20 rectifies a detecting signal by a synchronizing signal 4a synchronizing with electric power source frequency of an AC power source 4, and sends it out to a proportional operation part 30. The proportional operation part 30 converts a detecting signal from the synchronizing rectifying part 20, to a signal being proportional to displacement (x), and outputs it as a measuring signal E2. A drop portion of sensitivity of detecting coils 2, 3 is contained in the measuring signal E2. f(N) is a ratio in which the sensitivity of the detecting coils 2, 3 drops in accordance with an increase of a revolving speed, its range is 0<f(N)<=1, and f(N)=1 is sensitivity in a state that a rotating body 1 does not rate. As soon as the displacement (x) is detected, a revolving speed detecting part 50 detects a revolving speed N of the rotating body 1 and sends a revolving speed signal to a correcting operation part 40. The correcting operation part 40 executes a correction of a sensitivity drop portion of the detecting coils 2, 3 contained in the measuring signal E2 in accordance with the revolving speed signal.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a displacement measuring device that measures the movement or displacement of a rotating body in the axial direction.

[Technical background of the invention and its problems]

FIG. 1 is a diagram showing the configuration of a conventional displacement measuring device that measures the axial displacement of a rotating body that is rotating. In this device, a pair of detection coils 2 and 3 are arranged on both ends of a target to be measured 1a provided on a rotating body 1, with a gap a from the surface of the target 1a. The detection coils 2 and 3 are installed at a distance r from the center of the rotating body 1, as shown in FIG.

Reference numeral 10 denotes a detection unit, which constitutes a bridge circuit with the detection coil 2゜3 and impedance elements Zl and Z2 having preset impedance values, and changes the inductance of the detection coil 2゜3 ( When reactance) L changes, an AC signal corresponding to the change in inductance L is output as a detection signal and supplied to the subsequent synchronous rectifier 20. This synchronous rectifier 2θ rectifies the detection signal into a DC signal using a synchronization signal 4a synchronized with the power frequency of the AC power supply 4 that supplies power to the detection unit 10. Since this DC signal is not a signal proportional to the amount of change in displacement X (for example, an inverted S-shape), it is converted into a DC signal proportional to the amount of change in displacement
kx). Here, k is the detection coil 2.
It has a sensitivity of 3. This measures the displacement , there is a problem that a large measurement error occurs. The pick-up detection coils 2 and 3 form a magnetic circuit having a magnetic path M as shown in FIG. 3, and the iron core 2IL of these detection coils 2.3.

The inductance of 3a is expressed as follows.

Here, RA is the magnetic resistance of the air gap a, RT is the magnetic resistance of the target 9t 1a to be measured, RC is the magnetic resistance of the coil core 2a and Ja, and n is the winding of the coil. And the magnetic resistance RT and coil iron core of the measured Tada) Ja! a,
, 9a are always constant. Therefore, the inductance L changes depending on the change in the magnetic resistance RA of the air gap a. However, as shown in FIG. 2, when the rotating body 1 starts to rotate at the rotational angular velocity ω, the measured target 1*'' facing the detection coil 2.3 is pulled by ω2r2 to θ= in the tangential direction shown by the arrow A. In addition, the opening shown in FIG. 3 is the magnetic radial direction, and C is the rotational movement direction of the tarded 1a to be measured.

Due to this tensile stress, the magnetic permeability μ in the direction A of the target to be measured Ia decreases, and the magnetic resistance RA of the target to be measured Ja on the surface facing the detection coils 2 and 3 increases. As a result, the total magnetic resistance ΣR4 in the above equation representing the inductance L increases. Therefore, the ratio (ΔL/ΔRA) between the variation ΔRA in the magnetic resistance of the air gap a and the variation ΔL in the inductance L decreases. Therefore, as shown in FIG. 4, the output of the measurement signal E with respect to the displacement X becomes lower as the number of rotations N increases.

[Purpose of the invention]

The present invention was made in view of the current situation, and provides a highly accurate displacement measuring device that can eliminate the influence of the decrease in sensitivity of the detection coil that occurs depending on the rotation speed and accurately measure displacement in the direction of the rotation axis. The purpose is to provide.

[Summary of the invention]

The present invention provides a displacement measuring device that detects the displacement of a rotating body in the axial direction by a detection coil, rectifies this detection signal, and outputs the detected signal as a measurement signal proportional to the displacement. The decrease in sensitivity of the detection coil that decreases as the number of rotations increases is corrected by a correction calculation means having a relationship of sensitivity of the detection coil in inverse proportion to the number of rotations, and the above object is achieved. This is a displacement measurement device that aims to achieve this goal.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG. In addition, the same subdivisions as in the conventional device are given the same reference numerals, and detailed description thereof will be omitted.

That is, this device is provided with a correction calculation section 40 which receives the measurement signal E from the proportional calculation section 30, as shown in FIG.

The correction calculation section 40 inverts the sensitivity of the detection coil 2.3 to the magnitude of the rotation speed of the rotation body 30 based on the rotation speed signal of the rotation speed of the rotation body 3 detected by the rotation speed detection section 50. a detection coil 2 which has a function of outputting a proportional signal and which decreases as the rotational speed included in the measurement signal E increases;
This is to correct the decrease in sensitivity of No. 3.

Next, the operation of the apparatus configured as described above will be explained. First, the detection coils 2 and 3 are placed facing each other on both sides of the rotating body 1 at a predetermined distance r from the central axis thereof. At this point, the AC power supply 4 is turned on, and current flows to the detection coil 2.3.

The measurement signal E1 from the proportional calculation unit 30 when the rotating body 1 is not rotating is as shown in FIG. 6 (,) (E 1 =
It becomes kx. Here, as described above, k is the sensitivity of the detection coil coils 2 and 3, and X is the displacement.

Next, a state in which the rotating body 1 starts rotating will be explained.

The inductance L of each of the detection coils 2 and 3 changes in response to the displacement X in the direction of the rotational axis caused by the rotation of the rotary body 10 times. Further, as the rotational speed N of the rotating body 1 increases, a tensile stress θ=ω2r2 is generated in the direction A shown in FIG. Then, the magnetic permeability μ in the direction A decreases, and the magnetic resistance RT of the target to be measured increases. therefore,
The sensitivity of the detection coils 2 and 3 decreases.

The sensitivity of the detection coils 2 and 3 decreases as the rotational speed N increases.

Due to the change in the inductance L of the detection coils 2 and 3, the detection section 10 sends a detection signal corresponding to the displacement X to the synchronous rectification section 20 from a bridge circuit composed of the detection coil 2.3 and impedance elements Zi and Z2. The synchronous rectifier 20 rectifies the detection signal using a synchronous signal 4 a synchronized with the power layer wave number of the AC power source 4 and sends it to the proportional calculation section 30 . This direct current sending signal is not a signal proportional to the amount of change in the displacement X. Therefore, the proportional calculation section 30 converts the detection signal from the synchronous rectification section 20 into a signal proportional to the displacement X, and outputs it as a measurement signal E2. This measurement signal E2 includes a reduction in sensitivity of the detection coils 2 and 3, as shown in FIG. 6(b). Here, f (N) is the rate at which the sensitivity of the detection coils 2, 3 decreases as the rotational speed increases. And the range is 0<f(b)≦1,
f(f)=1 is one sensitivity when the rotating body 1 is not rotating.

Simultaneously with detecting the displacement
The 0 rotation speed N is detected and a rotation speed signal is sent to the correction calculation section 40. The correction calculation unit 40 corrects the decrease in sensitivity of the detection coils 2 and 3 included in the measurement signal E2 based on the rotational speed signal.

In other words, the correction calculation unit 40 has a function that is an inverse function [1/f□□□] of the ratio f of sensitivity that decreases as the rotational speed N increases, and corrects the decrease in sensitivity included in the measurement signal E2. do. In FIG. 5, the measurement signal E2 is equal to -f
(g) becomes. Then, the correction calculation unit 40 receives the measurement signal E.
2 is as shown in FIG. 6(b), and is a signal that is not affected by the magnitude of the rotational speed N.

Therefore, the detection coils 2 and 3 included in the measurement signal E2
Since the decrease in sensitivity is corrected by the correction calculation unit 40 based on the relationship between the sensitivities of the detection coils 2 and 3, which are inversely proportional as the rotational speed increases, no matter what rotational speed the rotating body 1 rotates,
Displacement X can be measured more accurately without being affected by the decrease in sensitivity of the detection coil 2.3. Further, the displacement X can be accurately measured no matter where the detection coil 2.3 is placed facing the object to be measured (Jm).

〔Effect of the invention〕

Since the present invention corrects the reduced sensitivity of the detection coil included in the measurement signal using the correction calculation section, the influence of the reduced sensitivity of the detection coil can be eliminated, and the axial displacement of the rotating body can be accurately measured with accuracy. It is possible to provide a high displacement measuring device.

[Brief explanation of the drawing]

Figure 1 is a configuration diagram showing a conventional displacement measuring device, Figure 2 (
) (b) is an external view showing the arrangement of the detection coil, Fig. 3 is an enlarged view of the part where the detection coil is arranged, Fig. 4 is a graph showing the output of the measurement signal depending on the rotation speed, and Fig. 5 is a graph showing the output of the measurement signal depending on the rotation speed. A configuration diagram of a displacement measuring device according to the present invention, FIG. 6 (,)
(b) shows a block diagram for explaining the operation of this device. 1...Rotating body, 1a...Targut to be measured, 2゜3
...Detection coil, 4...AC power supply, Z 1, Z
2... impedance element, 20... synchronous rectifier,
30... Proportional calculation section, 40... Correction calculation section, 50.
...Rotation speed detection section. Applicant's representative Patent attorney Takehiko Suzue Figure 1 Figure 2

Claims (1)

[Claims] Rotating body i! In a displacement measuring device that measures displacement in one direction, a detection coil to which AC power is supplied is placed at a target of a rotating body to be measured with a required gap, and detection is performed based on displacement in the axial direction of this rotating body. A displacement detection section that outputs a displacement detection signal from a change in the inductance of the coil; the output of this displacement detection section is synchronously rectified at the frequency of the AC power supply; and the DC signal obtained by this synchronous rectification is proportional to the displacement in the axial direction. means for converting into a measured signal, a rotation speed detection unit that detects the rotation speed of the rotating body and outputs a rotation speed signal, and an error component included in the measurement signal that occurs in response to the rotation speed of the rotating body. A displacement measuring device comprising: a correction calculation section that corrects K based on a correction relationship between the rotation speed of the rotating body and the detection sensitivity of the displacement detection section, which is predetermined based on the rotation speed signal.