JP2002350105A - Non-contact displacement gauge and measurement method using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To quickly measure the dimensional displacement of a work to be measured by readily and easily setting the measurement environment of the work to a state which close to the ideal state. SOLUTION: A non-contact displacement gauge is provided with a probe 2 having a measuring electrode 3 at its front end and measures the displacement of the interval between the work 1 to be measured and probe 2 from the change of the capacitance between the work 1 and electrode 3. The electrode 3 of the probe 2 is covered with an insulating coating film 7. The film 7 insulates the measuring electrode 3 from a liquid 9 when the electrode 3 is dipped in the liquid 9 for measuring the interval between the electrode 3 and work 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-contact displacement meter for measuring a change in distance from a measurement work via a capacitance and a measuring method using the same. In particular, the present invention relates to a non-contact displacement meter which is optimal for quickly measuring a ground measurement work, and a measuring method using the same.

[0002]

2. Description of the Related Art A capacitive non-contact displacement meter can detect a displacement of a measurement work with extremely high accuracy. For example, a non-contact displacement meter with a maximum measured displacement of 1 mm has a very high accuracy of 0.1 μm in resolution, which is the minimum detected displacement. If the maximum measured displacement is smaller, the resolution is set to 0.
Some have higher accuracy of 005 μm.

A non-contact displacement meter approaches a probe to a work to be measured, and detects a distance between the probe and the work as a change in capacitance. FIG. 1 shows the measurement principle. In this figure, the capacitance between the measurement work 1 and the measurement electrode 3 is proportional to the product of the area of the measurement electrode 3 and the dielectric constant of the substance between the measurement work 1 and the measurement electrode 3. Is inversely proportional to the distance between the workpiece 1 The capacitance can be expressed by the following equation. C = K × S / d where C is the capacitance, K is the dielectric constant, S is the area of the measurement electrode, and d is the distance between the measurement electrode and the measurement work. In this equation, since the dielectric constant and the area of the measurement electrode are constants, the distance between the measurement electrode and the measurement work can be detected from the capacitance. As is apparent from this equation, the change in the capacitance increases as d decreases. Therefore, the capacitance becomes infinitely large as d approaches 0. For this reason, the capacitance-based method can more accurately detect the displacement of the measurement work in a region where d is reduced.

[0004]

The non-contact displacement meter is most suitable for inspection of a measurement work requiring extremely high dimensional accuracy, such as an inner ring or an outer ring of a ground bearing. In particular, a non-contact displacement meter that measures the distance to a point focused on a spot like a laser is in a favorable state because the ground surface ground to a flat or curved surface has fine irregularities when observed microscopically. The distance from the ground surface cannot be measured. Since a non-contact displacement meter that measures an interval via a capacitance can measure an average distance from a ground surface, it can measure a distance from an inspection surface in an ideal state.

Taking advantage of this feature, in the manufacturing process of bearings and the like, the dimensional accuracy of the inner ring and the outer ring is measured by a capacitance-type non-contact displacement meter. Further, since bearings require extremely high machining accuracy, the inner and outer diameters of the ground inner ring and outer ring are detected by a non-contact displacement meter method.
The dimensions detected by the non-contact displacement meter are compared with standard values.
The deviation of the measured dimension from the standard value is fed back to the grinding process. However, the conventional capacitance-type non-contact displacement meter has a disadvantage that an error easily occurs due to contamination of the surface of the measurement work. Further, in order to reduce errors due to surface contamination, the ground measurement work is cleaned thoroughly, but this cleaning step has a disadvantage that it is difficult to measure dimensions quickly. This is because after the ground measurement work is thoroughly cleaned, measurement is performed in a clean environment in a clean room. Therefore, in the manufacturing process of the bearing, the actual condition is that the dimensions of the measurement work ground, for example, once a day are measured. However, the dimension measured in this way corrects the dimensional accuracy of the measurement workpiece to be processed the next day, and in the worst case, all the measurement workpieces ground in one day may be out of specification.

[0006] Such an adverse effect can be eliminated by quickly measuring the cut measurement work. Conventional non-contact displacement meter
In order to increase the measurement accuracy, it is necessary to restrict the measurement environment very severely, so that the measurement work cannot be measured quickly. Since the surface of the cut measurement work causes measurement errors due to surface contamination, and a change in the temperature of the measurement work also causes measurement errors, it is necessary to measure these dimensions under constant conditions. For this reason, it is not possible to accurately measure the cut work piece in a short time.

[0007] The present invention has been developed for the purpose of solving such disadvantages. An important object of the present invention is to provide a non-contact displacement meter capable of quickly and easily measuring a dimensional displacement of a measurement workpiece by setting a measurement environment of the measurement workpiece to a state close to an ideal, and a measurement using the non-contact displacement meter. It is to provide a method.

[0008]

The non-contact displacement meter according to the present invention includes a probe 2 having a measuring electrode 3 at a tip thereof.
The displacement of the distance between the measurement work 1 and the probe 2 is measured based on the change in the capacitance between the measurement work 1 and the measurement electrode 3. The probe 2 covers the surface of the measurement electrode 3 with an insulating film 7. The insulating film 7 is insulated from the liquid 9 while the measurement electrode 3 is immersed in the liquid, and measures the distance between the measurement electrode 3 and the measurement work 1.

The insulating film 7 can be made of an ultraviolet curable resin which is cured by irradiating ultraviolet rays, or glass. The thickness of the insulating film 7 can be set to 2 to 50 μm.

In the measuring method using the non-contact displacement meter of the present invention, the probe 2 having the measuring electrode 3 at the tip is brought close to the surface of the measuring work 1 and the electrostatic force between the measuring work 1 and the measuring electrode 3 is increased. The displacement of the distance between the measurement work 1 and the probe 2 is measured based on the change in the capacitance. In this measurement method, a probe 2 whose surface is covered with a water-resistant and oil-resistant insulating film 7 is used while the measurement work 1 is placed in a liquid. The measurement electrode 3 of the probe 2 is brought close to the surface of the measurement work 1 in the liquid, and the displacement of the distance between the measurement electrode 3 and the measurement work 1 is measured via the capacitance.

As the liquid 9 to be filled with the measuring work 1, a cleaning oil of the cut measuring work 1 can be used.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. However, the following examples illustrate a non-contact displacement meter for embodying the technical idea of the present invention and a measuring method using the same, and the present invention describes a non-contact displacement meter and a measuring method. Not specified below.

Further, in this specification, in order to make it easy to understand the claims, the numbers corresponding to the members shown in the embodiments will be referred to as “claims” and “ In the column of “means”. However, the members described in the claims are not limited to the members of the embodiments.

The non-contact displacement meter shown in FIG.
Probe 2 with built-in measuring electrode 3 for detecting the distance between
And a measurement circuit 8 connected to the measurement electrode 3 of the probe 2 to measure the distance between the measurement electrode 3 of the probe 2 and the measurement work 1.

The probe 2 includes a measurement electrode 3 embedded at the tip, a guard ring 4 disposed around the measurement electrode 3, and an insulator embedded between the guard ring 4 and the measurement electrode 3. 5, a lead wire 6 buried in the insulator 5 and connected to the measurement electrode 3 and the guard ring 4, and an insulating film 7 covering the surface of the insulator 5.

The measuring electrode 3 is a conductive plate such as a metal plate. The measurement electrode 3 has a surface facing the measurement work 1 having a shape along the surface of the measurement work 1. The measurement electrode 3 for measuring the distance from the measurement work 1 having the measurement surface as a plane has a flat surface facing the measurement work 1. A measurement electrode, such as an inner ring or an outer ring of a bearing, that measures a dimension with a measurement work having a curved measurement surface has a curved surface along the measurement work that faces the measurement work. The measurement electrode having a shape along the measurement surface of the measurement work can detect the interval with the measurement work with higher accuracy. However, the measurement electrode can also detect the interval between the measurement workpieces by making the surface facing the measurement workpiece a flat surface.

The guard ring 4 is in the form of a ring provided around the measuring electrode 3 and is insulated from the measuring electrode 3 and arranged on the same plane as the measuring electrode 3. Guard ring 4
By shielding the periphery of the measurement electrode 3, errors due to noise induced to the measurement electrode 3 can be reduced.

The insulator 5 is an insulating material such as plastic,
The measurement electrode 3 and the guard ring 4 are buried at the tip, and the measurement electrode 3 and the guard ring 4 are arranged at fixed positions. When the insulator 5 is formed of plastic, the measurement electrode 3 and the guard ring 4 are embedded and buried.

Further, a lead wire 6 connected to the measurement electrode 3 and the guard ring 4 is embedded in the insulator 5.
The lead wire 6 includes a core wire 6A connected to the measurement electrode 3,
And outer leads 6B connected to the guard ring 4. The outer leads 6B are arranged in a cylindrical shape around the core wire 6A and embedded in the insulator 5. Core wire 6A and outer lead 6
B is a coaxial cable structure embedded in the insulator 5.

The probe 2 in FIG. 2 insulates both surfaces of the measurement electrode 3 and the guard ring 4 with an insulating film 7. The probe does not necessarily need to be provided with a guard ring. This is because the probe and the guard ring can measure the distance from the measurement work. Probes without guard rings insulate the surface of the measurement electrode with an insulating film. The probe 2 including the measurement electrode 3 and the guard ring 4 covers both surfaces of the measurement electrode 3 and the guard ring 4 with the insulating film 7. The insulating film 7 insulates the measurement electrode 3 and the guard ring 4 from the liquid 9 while the probe 2 is in the liquid 9. Therefore, the insulating film 7 has a characteristic that the measurement electrode 3 and the guard ring 4 can be insulated when the insulating film 7 is in a liquid 9 such as oil or water. As the insulating film 7, an ultraviolet curable resin that is cured by irradiating ultraviolet light can be used. As this type of resin, there are urethane resins and epoxy resins. The ultraviolet curable resin is very hard in a cured state, and the measuring electrode 3
And the guard ring 4 are effectively protected and insulated. further,
Glass can also be used for the insulating film 7. The insulating film 7
The film thickness is reduced as far as the measurement electrode 3 can be effectively insulated.
This is because the thick insulating film 7 causes a decrease in measurement accuracy. However, if the insulating film 7 is too thin, the measuring electrode 3
Cannot be sufficiently insulated, and the insulation characteristics deteriorate. The thickness of the insulating film 7 is, for example, 2 to 50 μm, preferably 3 to 30 μm, and more preferably 5 to 20 μm in consideration of measurement accuracy and insulating characteristics.

The probe 2 shown in FIG. 2 has a measurement electrode 3 and a guard ring 4 embedded in an insulator 5, and the surface of the insulator 5 is covered with an insulating film 7. As shown in FIG. 3, the probe 2 may have an integral structure of the insulator 5 and the insulating film 7. The probe 2 is composed of an insulating material having an integral structure of an insulator 5 and an insulating film 7, a measuring electrode 3 and a guard ring 4.
It is manufactured by burying it. The probe 2 has the measurement electrode 3 and the guard ring 4 embedded so that the surfaces of the measurement electrode 3 and the guard ring 4 are covered with an insulating material to be insulated.

The probe 2 shown in FIG. 2 has an insulating film 7 covering the distal end surface of the insulator 5 and the periphery. However, although not shown, the probe can be provided with an insulating film only on the tip surface of the insulator to insulate the measurement electrode from the guard ring. This is because the guard ring and the measurement electrode are not exposed around the insulator. However, as shown in FIG. 2, the probe 2 in which the front end surface and the periphery are covered with the insulating film 7 or the entire surface of the insulator 5 is covered with the insulating film 7 is obtained by putting the probe 5 in the liquid 9 in the insulator 5. An insulating material having poor insulation properties can be used. This is because the insulating film 7 insulates the liquid 9.

The above-described probe 2 moves the measurement electrode 3 close to the measurement work 1 contained in the liquid 9 and
The distance between the electrode and the measurement electrode 3 can be measured. FIG. 4 shows the measuring circuit 8 connected to the measuring electrode 3. This measuring circuit 8
An oscillation circuit 10 for oscillating an alternating current; a current detection circuit 11 connected between the oscillation circuit 10 and the measurement electrode 3; and a control circuit 12 for controlling an output voltage of the oscillation circuit 10 by an output signal of the current detection circuit 11 And a display circuit 13 for detecting and displaying the distance between the measurement electrode 3 and the measurement work 1 from the output voltage of the oscillation circuit 10 controlled by the control circuit 12.

In the measuring circuit 8 shown in FIG. 4, the control circuit 12 controls the output voltage of the oscillation circuit 10 so that the current flowing through the measuring electrode 3 becomes a constant value. The current flowing through the measurement electrode 3 is detected by the current detection circuit 11. Current detection circuit 11
The current signal detected by the control circuit 12 is input to the control circuit 12. The control circuit 12 compares the input current signal with a reference value,
When the current signal is lower than the reference value, the output voltage of the oscillation circuit 10 is increased, and when the current signal is higher than the reference value,
The output voltage of the oscillation circuit 10 is reduced. The reference value with which the control circuit 12 compares the input current signals is the capacitance between the measurement electrode 3 and the measurement work 1 when the distance between the measurement electrode 3 and the measurement work 1 is a preset distance. Is the value for the set capacity. Since the current flowing through the measurement electrode 3 changes depending on the distance between the measurement electrode 3 and the measurement work 1, that is, the capacitance, for example, the distance between the measurement electrode 3 and the measurement work 1 becomes wider than the set distance. When the capacitance decreases, the current flowing through the measurement electrode 3 decreases. Measurement electrode 3 and measurement work 1
This is because the impedance between them increases. The display circuit 13 includes the oscillation circuit 10 output from the control circuit 12.
The distance between the measurement electrode 3 and the measurement work 1 is detected from the output voltage. Since the output voltage of the oscillation circuit 10 changes according to the capacitance, and the capacitance changes at the interval between the measurement electrode 3 and the measurement work 1, the output voltage of the oscillation circuit 10 Intervals can be detected. Display circuit 13
Detects the interval from the output voltage of the oscillation circuit 10 and displays the value.

The above measuring circuit 8 accurately measures the distance between the measuring electrode 3 and the measuring work 1 in comparison with the set distance. However, the measurement circuit 8 does not necessarily need to detect the capacitance between the measurement electrode 3 and the measurement work 1 by the above method. For example, the interval between the measurement electrode 3 and the measurement work 1 can be detected by keeping the output voltage of the oscillation circuit 10 constant and detecting the current flowing through the measurement electrode 3. Also,
The oscillation frequency of the oscillation circuit 10 can be changed by the capacitance between the measurement electrode 3 and the measurement work 1, and the interval between the measurement electrode 3 and the measurement work 1 can be detected by the oscillation frequency.

The above-described non-contact displacement meter detects the distance between the measuring electrode 3 and the measuring work 1 as follows. As shown in FIG. 2, the measurement work 1 is placed in the liquid 9 filling the container 14. The measuring work 1 is preferably entirely immersed in a liquid 9 as shown in the figure. In the method of immersing the entirety in the liquid 9 and measuring the distance from the measurement work 1, the temperature of the entire measurement work 1 can be set to the temperature of the liquid 9. The liquid 9 has a higher thermal conductivity than air. Therefore, the temperature of the measurement work 1 immersed in the liquid 9 quickly becomes the liquid temperature. For this reason, the temperature of the measurement work 1 can be accurately detected based on the liquid temperature. However, in the measurement method of the present invention, it is not always necessary to immerse the entire measurement work in the liquid. This is because only the measurement part with the measurement work can be put in the liquid to measure the interval.

The whole probe 2 or the tip provided with the measuring electrode 3 is put into the liquid 9 and the measuring electrode 3 is fixed at a position facing the measuring work 1. Although the figure does not show the structure for fixing the probe 2, the probe 2
Is fixed to, for example, a container 14 containing the liquid 9 or a table (not shown) on which the container 14 is placed. In this state, the liquid 9 is placed between the measurement electrode 3 and the measurement work 1.
Is interposed. The liquid 9 is oil or water. When measuring the dimensions of the inner and outer rings of the bearing, a cleaning oil is used as the liquid 9. The dielectric constant of the liquid 9 is different from the dielectric constant of air. Different dielectric constants result in different capacitances. This is because the capacitance increases in proportion to the dielectric constant. The display circuit 13 corrects the permittivity. The display circuit 13 stores a correction coefficient for the permittivity of the liquid 9 in which the probe 2 and the measurement work 1 are put. For example, when the distance between the measurement electrode 3 and the measurement work 1 is measured using the liquid 9 whose dielectric constant is twice that of air, the distance is displayed as 1/2 of the display value of air. This is because when the measurement is performed using the liquid 9, the same capacitance is obtained when the distance between the measurement electrode 3 and the measurement work 1 is twice as large as that in the case of air.

The distance between the measuring electrode 3 and the measuring work 1 is detected by successively changing the measuring works 1 immersed in the liquid 9 of the container 14. The measurement work 1 is placed in a predetermined position, and the distance between the measurement work 1 and the measurement electrode 3 is measured. Foreign matter mixed into the liquid 9 causes a measurement error. Therefore, a clean liquid 9 free from foreign matter is used as the liquid 9. The measurement work 1 to be put in the liquid 9 is also cleaned, for example, with a cleaning liquid and immersed in the liquid 9. The liquid 9 in the container 14 can be clarified by circulating through a filter to remove foreign substances. When a cleaning liquid is used as the liquid 9, the measurement work 1 washed with the cleaning liquid can be put into the liquid 9 as it is to perform measurement.

[0029]

According to the non-contact displacement meter and the measuring method using the non-contact displacement meter of the present invention, the measurement environment of the measurement work can be easily and easily set to a state close to the ideal, and the dimensional displacement of the measurement work can be quickly changed. There is a feature that can be measured. That is, the non-contact displacement meter of the present invention is provided with a probe having a measurement electrode at the tip, the surface of the measurement electrode is coated with an insulating film, and the measurement electrode is insulated from the liquid in a state of being immersed in the liquid, Further, the measuring method of the present invention is such that the measuring electrode of the probe whose surface is covered with the insulating film is brought close to the surface of the measuring work put in the liquid, and the displacement of the distance between the measuring electrode and the measuring work is electrostatically changed. This is because the measurement is performed via the capacitance. The non-contact displacement meter and the measuring method that measure the displacement of the distance between the measurement work and the liquid in the liquid can be measured while removing the surface of the measurement work with the liquid, so it is effective that foreign substances on the surface cause measurement errors. Can be prevented. Further, since the temperature change of the measurement work can be reduced by putting the measurement work in the liquid, the measurement error caused by this can be minimized. As described above, the non-contact displacement meter and the measurement method of the present invention measure the displacement of the distance between the measurement electrode and the measurement work in the liquid. The dimensional displacement of the measurement work can be accurately measured in a short period of time without any restrictions, while keeping the conditions extremely simple.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing the measurement principle of a capacitance-type non-contact displacement meter.

FIG. 2 is a sectional view of a non-contact displacement meter according to an embodiment of the present invention.

FIG. 3 is a sectional view of a non-contact displacement meter according to another embodiment of the present invention.

FIG. 4 is a circuit diagram of a measurement circuit of the non-contact displacement meter shown in FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Measurement work 2 ... Probe 3 ... Measurement electrode 4 ... Guard ring 5 ... Insulator 6 ... Lead wire 6A ... Core wire 6
B ... Outer lead 7 ... Insulating film 8 ... Measurement circuit 9 ... Liquid 10 ... Oscillation circuit 11 ... Current detection circuit 12 ... Control circuit 13 ... Display circuit 14 ... Container

Claims (6)

[Claims] 1. A probe (2) having a measuring electrode (3) at its tip.
The probe (2) is brought close to the measurement work (1), and the change in the capacitance between the measurement work (1) and the measurement electrode (3) causes the measurement work (1) and the probe ( This is a non-contact displacement meter that measures the displacement at the distance from 2), and the probe (2) covers the surface of the measuring electrode (3) with an insulating film (7). The measurement electrode (3) is insulated from the liquid (9) with the measurement electrode (3)
Non-contact displacement meter that measures the distance between the workpiece and the work (1). 2. The non-contact displacement meter according to claim 1, wherein the insulating film (7) is an ultraviolet curing resin which is cured by irradiating ultraviolet rays. 3. The non-contact displacement meter according to claim 1, wherein the insulating film is glass. 4. The non-contact displacement meter according to claim 1, wherein the thickness of the insulating film (7) is 2 to 50 μm. 5. A probe (2) having a measuring electrode (3) at its tip.
Is brought close to the surface of the measurement work (1), and the distance between the measurement work (1) and the probe (2) is determined by the change in capacitance between the measurement work (1) and the measurement electrode (3). In a measurement method using a non-contact displacement meter that measures displacement, a probe (2) whose surface is covered with a water-resistant and oil-resistant insulating film (7) while a measurement work (1) is Use the measurement electrode (3) of this probe (2) close to the surface of the measurement work (1) in the liquid, and move the measurement electrode (3) and the measurement work (1).
A measurement method using a non-contact displacement meter configured to measure a displacement of an interval between the two through a capacitance. 6. A measuring method using a non-contact displacement meter according to claim 5, wherein a cleaning oil of the cut measuring work (1) is used as the liquid (9) for charging the measuring work (1).