JPH0750646Y2 - Ceramic type electrostatic sensor device - Google Patents

Description

[Detailed Description of the Invention] [Industrial field of application] The present invention relates to a moving table equipped with a ceramic electrostatic sensor (an electrostatic sensor having a resonator formed of a ceramic resonator) as a ceramic electrostatic sensor. The present invention relates to a ceramic type electrostatic sensor device that integrally feeds and detects the positioning of a moving table.

[Conventional technology]

For example, a measuring device such as a scanning tunneling microscope and a ceramic electrostatic sensor are mounted on a movable table, and the feed amount of the movable table is detected by the ceramic electrostatic sensor as a change in capacitance, or As shown in the figure, the ceramic type electrostatic sensor 2 is mounted on the moving base 1, and the feed screw 3 of the feeding mechanism 4 formed by fitting the feed screw 3 into the screw forming hole of the moving base 1 is rotationally driven. , Ceramic type electrostatic sensor 2
There is known a device in which the unit is moved integrally with the moving table 1 to measure the size of the detected body 5 by detecting a change in electrostatic capacitance between the detection electrode 10 and the detected body 5.

This type of ceramic electrostatic sensor has a built-in high-frequency circuit, and its driving frequency is a signal of ultrahigh frequency of 1 GHz in order to increase the detection sensitivity of electrostatic capacitance, and it is detected by the detection electrode 10. A change in capacitance is converted into, for example, a voltage signal, the voltage signal is processed in a desired form, signal-amplified on the output side of the circuit, and output as a detection signal of change in capacitance. In an electrostatic sensor device using an ultrahigh frequency as described above, the radiation of electromagnetic waves propagating in the air from the high-frequency circuit side causes, for example, stray capacitance or parasitic capacitance between circuit elements or between circuit elements and conductors, resulting in circuit operation. The ceramic type electrostatic sensor 2 is entirely covered with a conductor case 9 in order to prevent high frequency radiation. The movable table 1 is formed of a conductive metal so as to serve as a ground conductor of a high frequency circuit in the ceramic electrostatic sensor 2.

In general, in the electrostatic sensor 2 including a high-frequency circuit of this type, even if the conductor case 9 is used, a slight adverse effect due to radiation of leaked electromagnetic waves to the outside remains, and this effect makes the characteristics of the electrostatic sensor device minute. The output voltage before amplification of the electrostatic sensor device is as small as 1 to 10 mV.
It has the characteristic that the fluctuation of the order becomes a noise component. In order to prevent such an adverse effect of leaked electromagnetic waves, it is necessary to ground the conductor case 9 as stably as possible.

[Problems to be solved by the device]

When an attempt is made to detect a change in a minute electrostatic capacitance with high sensitivity by using the ceramic type electrostatic sensor 2 with an ultrahigh frequency signal, a ground circuit is configured via the feed mechanism 4 and the like, so that when the movable table 1 moves Due to vibration or the like, an extremely minute gap is instantaneously generated between the bottom surface of the conductor case 9 and the moving base 1 or between the moving base 1 and the feed screw 3 in the ceramic electrostatic sensor, and this gap moves the moving base 1. And the grounding state of the high-frequency circuit in the ceramic electrostatic sensor becomes unstable and is affected by the fluctuation of leakage electromagnetic waves, the circuit constant of the high-frequency circuit fluctuates, and the oscillation frequency of the electrostatic sensor device changes. In addition, the circuit constant such as a change in the ground resistance of the detection signal circuit of the small electrostatic capacitance changes, noise is generated with the movement of the moving table 1, and the ceramic electrostatic sensor does not operate normally. Say There was a problem.

The present invention has been made in order to solve the above-mentioned conventional problems, and an object thereof is to prevent the generation of harmful noise even when a moving table equipped with a ceramic electrostatic sensor is moved. To provide an electric sensor device.

[Means for Solving the Problems]

The present invention is configured as follows to achieve the above object. That is, according to the present invention, a ceramic electrostatic sensor having a high frequency circuit is mounted on a conductor moving base covered with a conductor case, and a feed mechanism linked to the conductor moving base is driven to move the ceramic electrostatic sensor to the conductor. In a ceramic type electrostatic sensor device that moves with a table, the conductor case is capacitively grounded to the conductor moving table at a high frequency between the contact surfaces of the conductor case covering the ceramic electrostatic sensor and the conductor moving table. It is configured by an insulating member being interposed.

[Action]

In the present invention, the insulating member is provided between the conductor moving base and the conductor case covering the ceramic electrostatic sensor, so that the grounding state between the moving base and the feeding mechanism during feeding of the moving base by the feeding mechanism is maintained. It is intended to eliminate the influence of a change and a change in the gap between the electrostatic sensor and the conductor moving base and inside the feed mechanism, for example, between the feed screw fittings. That is, the conductor case and the conductor moving base are grounded at a high frequency through a constant electrostatic capacitance Co formed by an insulating member between them, and the constant electrostatic capacitance Co and the static electricity during the feed movement of the conductor moving base by the feeding mechanism. The variation Cv (Co >> Cv) of the capacitance constitutes a series circuit. In this series circuit of Co and Cv, Co is much larger than Cv, so the overall capacitive impedance between the conductor case and feed mechanism of the ceramic electrostatic sensor is determined by the electrostatic capacitance Co, and the variation Cv Can be ignored. Therefore, even if the capacitance changes due to the feed mechanism, the noise component generated from the electrostatic sensor is significantly reduced (for example, to about 1/10 or less), and the effect of the fluctuation Cv can be ignored. And the noise is reduced.

〔Example〕

An embodiment of a ceramic type electrostatic sensor device according to the present invention will be described below with reference to the drawings. In the description of the present embodiment, the same parts as those in the conventional example are designated by the same reference numerals, and detailed description thereof will be omitted. FIG. 1 shows a first embodiment of the present invention. In the device of the first embodiment, a concave member 7 is formed on the upper surface of a movable base 1 made of a conductive metal, and a plate-shaped insulating member 8 such as epoxy is formed in the concave member 7.
Is fitted and fixed, and a conductor case 9 incorporating the ceramic electrostatic sensor 2 is mounted on the upper side of the insulating member 8.

In this way, if the insulating member 8 is provided between the conductor case 9 and the conductor moving base 1, the circuit of the ceramic electrostatic sensor 2 operates as a closed circuit in the conductor case 9 in terms of low frequency, and high frequency. Specifically, as shown in FIG. 4, the capacitance Co between the conductor moving base 1 and the conductor case 9, the conductor moving base 1 and the feeding mechanism 4 are used.
It is grounded by a series circuit of the variable amount Cv of the capacitance between the male screw of the feed screw 3 inside the feed mechanism 4 and the screw hole receiving the feed screw 3. In this way, the conductor moving base 1 and the conductor case 9 are capacitively grounded, whereby the conductor moving base 1
When the feed mechanism 4 is moved by the drive of the feed mechanism 4, the feed mechanism 4 and the move table 1 move to the electrostatic capacitance between the conductor move table 1 and the ground.
Even if there is a variation Cv due to a change in the contact state with the sensor or a change in the air gap due to vibration between the electrostatic sensor and the conductor moving table 1, Cv
On the other hand, Co is much larger, so the influence of Cv is small,
As a result, the grounded state of the conductor case 9 becomes stable, and the circuit constant of the high-frequency circuit does not fluctuate due to Cv, so that noise is not generated and high-resolution measurement of the ceramic electrostatic sensor becomes possible. .

FIG. 2 shows a second embodiment of the present invention. The second embodiment is the same as the first embodiment except that the entire conductor case 9 is covered with an insulating member 8. Various methods can be used to form the insulating member 8 that covers the conductor case 9. In this embodiment, the insulating laminate tape is evenly wound around the outside of the conductor case 9 to form the insulating member. 8 forming.

Also in the second embodiment, the conductor moving table 1 and the conductor case 9 are opposed to each other with the insulating member 8 interposed therebetween, and the conductor case 9 moves with the conductor case 9 as shown in FIG. 4 in terms of high frequency. A fixed capacity Co corresponding to the insulating member 8 between the stands 1 and a variable capacity between the conductor moving stand 1 and the feed mechanism 4 and inside the feed mechanism
Stable ground in a series circuit with Cv, so conductor moving stand 1
When moving the same as in the case of the first embodiment,
The circuit constant of the high frequency circuit in the ceramic type electrostatic sensor 2 does not fluctuate greatly and noise is not generated,
Highly sensitive and high-performance detection using the ceramic electrostatic sensor 2 becomes possible. It should be noted that the present invention is not limited to the above-mentioned embodiment, and various modes of implementation can be adopted.

[Effect of device]

According to the present invention, the insulating member is provided between the conductor case covering the ceramic electrostatic sensor and the conductor moving base. Therefore, in terms of high frequency, the conductor case is between the conductor case and the conductor moving base. The constant capacity Co corresponding to the insulating member of C and the variable capacity Cv between the conductor moving base and the feed mechanism are grounded in series, and Co is much larger than Cv, so the conductor moving base moves. Even if the fluctuating capacitance Cv changes, it becomes a fluctuating component that can be ignored from the viewpoint of the total ground capacitance, and stable grounding of the conductor case is realized. As a result, it is possible to prevent the ground state from becoming unstable and the circuit constant of the high-frequency circuit in the ceramic electrostatic sensor to fluctuate significantly as in the conventional case. Therefore, when the conductor moving table is moved, the conventional problem that noise is generated in the ceramic type electrostatic sensor and the detectability is lowered is surely solved, and the high sensitivity and high performance measurement of the ceramic type electrostatic sensor is solved. It can be detected.

Further, since the present invention has a simple structure in which an insulating member is simply provided between the conductor moving base and the conductor case, the device structure can be made small, lightweight and inexpensive, and minute position detection in various fields, etc. Applicable to, and its practical value is very large.

[Brief description of drawings]

FIG. 1 is a sectional view of a main part showing a first embodiment of the present invention, and FIG.
FIG. 4 is a cross-sectional view of a main part showing a second embodiment of the present invention, FIG. 3 is a perspective view showing a conventional device, and FIG. 4 is an equivalent circuit diagram of the ground capacitance of a conductor case in the embodiment. 1 ... Conductor moving table (moving table), 2 ... Ceramic type electrostatic sensor, 3 ... Feed screw, 4 ... Feed mechanism, 5 ... Detected object, 7 ... Recess, 8 ... Insulating member, 9 ... Conductor case, 10 ... Detection electrode.

Claims (1)

[Scope of utility model registration request] 1. A ceramic type electrostatic sensor having a high frequency circuit is mounted on a conductor moving base covered with a conductor case, and a feed mechanism linked to the conductor moving base is driven to move the ceramic type electrostatic sensor to the conductor moving base. In a ceramic-type electrostatic sensor device that moves together with the conductor-type electrostatic sensor, insulation is provided for capacitively grounding the conductor case to the conductor-moving base at a high frequency between the contact surfaces of the conductor case covering the ceramic-type electrostatic sensor and the conductor-moving base. A ceramic type electrostatic sensor device characterized in that a member is interposed.