JPH04232878A - Surface potential sensor - Google Patents

Abstract

PURPOSE:To improve the sensitivity of a surface potential sensor by improving the vibration frequency of a chopper while maintaining the amplitude of the electrostatic chopper of the surface potential sensor. CONSTITUTION:One end of a driving bar-shaped piezoelectric element 11 is fixed at the bottom section of a U-shaped base 12. The first lever 13 and the second lever 14 are connected to each apex of the base 12 and the other end of the bar-shaped piezoelectric element 11, and the first lever 13 and the second lever 14 are displaced in different directions by the longitudinal piezoelectric effect of the bar-shaped piezoelectric element 11. One end of the third lever 15 is connected to the end section of the first lever 13, and one end of the fourth lever 16 is connected to the end section of the second lever 14 respectively. An electrostatic chopper 17 is connected to the other end of the third lever 15, and the other end of the fourth lever 16 is connected to it. Displacements of the first lever 13 and the second lever 14 are transferred to the third lever 15 and the fourth lever 16 respectively, and the electrostatic chopper 17 is vibrated by the couple between them.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a potential sensor used for detecting the strength of an electrostatic field, measuring the amount of charge, and the like.

0002

[Prior Art] Generally, a potential sensor has a case that has a detection hole for introducing lines of electric force radiated from an object to be measured, and a chopper section that cuts the lines of electric force entering the case at regular intervals. , and an electrode for receiving the cut lines of electric force and extracting an alternating current signal.

FIGS. 3 and 4 are a plan sectional view and a side sectional view showing an example of a conventional potential sensor. The chopper section uses a tuning fork 2 to which a driving piezoelectric ceramic 6 is adhered, and the electric lines of force 7 are cut at the tips 2a and 2b of the tuning fork 2. The electrode 3 is fixed to the substrate 8 at a position behind the tips 2a and 2b of the tuning fork 2. A substrate 8 on which these chopper parts and electrodes are mounted is housed in a case 1 having a detection hole 18. Reference numbers 4, 5 and 9 are a tuning fork drive terminal, an output terminal and a ground terminal, respectively.

0004

SUMMARY OF THE INVENTION The conventional surface potential sensor using a tuning fork type chopper has a problem in that its sensitivity cannot be sufficiently increased. That is, the detection sensitivity of the chopper-type surface potential sensor is proportional to the effective operating area of the chopper, which blocks, passes, or exposes lines of electric force, and the operating frequency of the chopper. Therefore, in order to increase the operating frequency of the tuning fork in order to increase the sensitivity of the sensor, it is necessary to shorten the arm of the tuning fork or increase the plate thickness of the tuning fork. This conversely reduces the amplitude of the tuning fork and reduces the effective operating area of the chopper. Therefore, the tuning fork is designed to provide the best compromise between the effective operating area of the chopper and the operating frequency. Currently, the tuning fork frequency is 520H.
z, chopper amplitude of about 0.5 mm is used.

Therefore, the present invention aims to greatly improve the operating frequency of the chopper while keeping the effective operating area of the chopper at the same level as the conventional one, thereby significantly improving the measurement sensitivity of the chopper type surface potential sensor. This is an issue.

[0006]

[Means for Solving the Problems] The present invention improves the operating frequency of an electrostatic chopper while keeping the amplitude of the chopper at the same level.It is used for driving an electrostatic chopper to reduce dimensional distortion by the piezoelectric longitudinal effect when voltage is applied. A rod-shaped piezoelectric element is generated, a base is formed in a U-shape, and one end of the piezoelectric element is connected to the inner bottom, and first and second bases are connected to the other end of the piezoelectric element and each top of the base, respectively. a third lever having one end connected to the electrostatic chopper and one end of the fourth lever, and the other end connected to one end of the first lever;
It has a mechanism in which the other end of the fourth lever is connected to one end of the second lever.

[0007]

[Operation] In the surface potential sensor of the present invention, when a voltage is applied to the piezoelectric element for driving the electrostatic chopper, dimensional distortion occurs due to the piezoelectric longitudinal effect, which deforms the U-shaped base and is displaced, and the first lever and second lever connected to each top are respectively displaced accordingly. Further, these displacements are transmitted to the tips of the third and fourth levers, respectively, and a couple is generated between the two levers. This couple causes the chopper to vibrate, and intermittently blocks the lines of electric force from the object to be measured toward the detection electrode. The amplitude is expanded by the displacement of multiple members, ranging from dimensional distortion of the piezoelectric element to vibration of the chopper.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be explained with reference to the drawings. 1 and 2 are a plan sectional view and a side sectional view showing an embodiment of the present invention. The lower end of the piezoelectric element 11 is the base 12
The inner bottom of the lever is connected to the inner bottom of the lever, and the upper end thereof is connected to the lower end of the first lever 13 and the second lever 14, respectively. The lower ends of the levers 13 and 14 are also connected to the base 2, and the upper ends of the levers 13 and 14 are connected to one ends of a third lever 15 and a fourth lever 16, respectively. At the other end of the lever 15,
The electrostatic chopper 17 and the other end of the lever 16 are connected.

When a voltage is applied, the piezoelectric element 11 stretches in the direction of the dashed arrow S due to the longitudinal effect, causing dimensional distortion, and in response, the upper ends of the levers 13 and 14 are displaced in the directions of the dashed arrows T and U, respectively. will occur. The force couple accompanying these two displacements drives the electrostatic chopper 17 in the direction of the arrow 19 via the levers 15 and 16. The electric force lines 7 are cut by the movement of the electrostatic chopper 17 in the direction 19 of the arrow. The electrode 3 is fixed to the substrate 8 at a position behind the chopper 17. The substrate 8 on which these chopper parts and electrodes are mounted is housed in a case 1 having a detection hole 18. Reference numbers 4, 5 and 9 are respectively chopper drive terminals;
It is an output terminal and a ground terminal.

0010

[Effects of the Invention] The present invention does not simply use the deflection of the plate to expand the amplitude like the tuning fork type, but mechanically expands the distortion of the piezoelectric element, so the frequency is much higher than that of the tuning fork type. A sufficiently large amplitude (for example, about 0.5 mm) can be obtained up to a frequency of about 3 kHz (for example, about 3 kHz), and the sensitivity as a surface potential sensor can be improved by about 6 times compared to the conventional one.

[Brief explanation of the drawing]

FIG. 1 is a plan sectional view of an embodiment of the present invention.

FIG. 2 is a side sectional view of the above embodiment of the invention.

FIG. 3 is a plan cross-sectional view showing an example of a conventional potential sensor.

FIG. 4 is a side sectional view showing an example of a conventional potential sensor.

[Explanation of symbols]

1 Case 2 Tuning fork 2a, 2b Tip part 3 Electrode 4 Drive terminal 5 Output terminal 6 Piezoelectric ceramics 7 Electric lines of force 8 Substrate 9 Ground terminal 11 Piezoelectric element 12 Base 13, 14, 15, 16 Lever 17 Electrostatic chopper 18 Detection hole 19 Direction of motion

Claims (1)

[Claims] Claim 1: A surface potential of a method in which an AC voltage proportional to the charged voltage of the object to be measured is extracted from the detection electrode by periodically changing the lines of electric force from the object to the detection electrode by vibration of an electrostatic chopper. The sensor includes a rod-shaped piezoelectric element for driving the electrostatic chopper that generates dimensional distortion due to a piezoelectric longitudinal effect when voltage is applied, and a base formed in a U shape and having one end of the piezoelectric element connected to the inner bottom. and a first and second lever connected to the other end of the piezoelectric element and each top of the base, one end of which is connected to an electrostatic chopper and one end of a fourth lever, and the other end of which is connected to the first and second levers. a third lever connected to one end of the lever; the other end of the fourth lever is connected to one end of the second lever; 4. A surface potential sensor characterized in that the electrostatic chopper is vibrated by generating a couple between the lever and the electrostatic chopper.