JP2514596Y2 - Electrostatic sensor device - Google Patents

Description

[Detailed Description of the Invention] [Industrial field of application] The present invention relates to an electrostatic sensor device for detecting a change in a minute electrostatic capacitance with respect to an object to be detected.

[Conventional technology]

Recently, an electrostatic sensor device using a ceramic resonator as a resonator has been proposed. As shown in FIG. 4, this type of device includes an oscillation circuit 1, a tuning circuit 2, and a detection needle which is connected to the tuning circuit 2 and includes an electrode needle or the like for detecting a capacitance change with an object to be detected. It includes a unit 3, a detection circuit 4, and an amplification circuit 5. The oscillation circuit 1 and the tuning circuit 2 include ceramic resonators that are independent of each other. For example, as shown in FIG. 5, the resonance frequency f ₀ of the tuning circuit 2 is set to the fixed oscillation frequency f ₁ of the oscillation circuit 1. The capacitance is set to a position slightly deviated, and the resonance frequency is deviated from f ₀ by Δf in correspondence with the change ΔC of the small capacitance detected by the detection unit 3, and the change ΔC of the capacitance is output. It is converted into a change in ΔV, detected and amplified, and taken out.

Normally, in this type of device, as shown in FIG. 6, a ceramic resonator 7 as a tuning circuit is arranged on a printed circuit board 6. The output terminal 8 of the ceramic resonator 7 is connected to the conductor pattern 10 formed on the printed circuit board 6 by using solder, and the conductor pattern 10 is provided with the base end side of the electrode needle 11 constituting the detecting portion 3. Solder connected. The tip of the electrode needle 11 projects outward from the printed circuit board 6 and faces an unillustrated object to be detected, and detects the movement of the object to be detected as a minute change in capacitance. The printed circuit board 6 is further provided with an oscillator circuit 1, a detection circuit 4 and an amplifier circuit 5. The printed circuit board 6 on which these circuits are formed is covered with a conductor case 12, and each circuit on the printed circuit board 6 is kept quiet from the outside. It is electrically cut off.

[Problems to be solved by the device]

However, in the conventional proposed device, since the electrode needle 11 is connected to the conductor pattern 10 by using solder or the like, the solder connection position of the electrode needle 11 is not constant and the output terminal 8 of the ceramic resonator 7 is not fixed. There is a problem in that the distance from the position to the tip of the electrode needle 11 varies, the capacitance with respect to the ground increases, the resonance point shifts, and the detection performance of the device becomes unstable.

That is, in this type of electrostatic sensor device, as shown in FIG. 7, the resonance frequency f of the ceramic resonator 7 is nλ / 4 (λ is the resonance frequency) from the output terminal 8 to the tip of the electrode needle 11. When the wavelength of the signal, n is an integer of 1 or more), it suddenly changes and becomes the most unstable, and this unstable region extends to a region of ± λ / 10 around nλ / 4. When a very high resonance frequency such as 1 GHz to 3 GHz is used in order to reduce the size of the device and achieve detection with high sensitivity, the electrode needle 11 is slightly misaligned when soldered. Then, the distance between the output terminal 8 and the tip of the electrode needle 11 enters the unstable region of the resonance frequency f, and the detection performance of the device becomes unstable.

The present invention has been made in order to solve the above-mentioned conventional problems, and an object thereof is to prevent destabilization of the device performance due to the positional deviation at the time of solder connection of the electrode needle, and to prevent the output terminal of the ceramic resonator. An object of the present invention is to provide an electrostatic sensor device with stable detection performance in which the length from the electrode needle to the tip of the electrode needle does not fall within the unstable region of the resonance frequency.

[Means for solving the problem]

The present invention is configured as follows to achieve the above object. That is, the present invention is an electrostatic sensor device in which a resonator is formed of a ceramic resonator, and a base end side of a circuit board on which the ceramic resonator is mounted is housed in a conductor case, and an opening portion of the conductor case is provided. The electrode pattern forming portion of the circuit board is formed so as to project to the outside of the conductor case, and the detection electrode pattern is formed on the electrode pattern forming portion from the base end side to the tip end side of the electrode pattern forming portion. Of the detection electrode pattern is connected to the output terminal of the ceramic resonator, and the extended front end surface of the detection electrode pattern is for detecting a capacitance change facing the object to be detected. It is characterized by having an electrode surface.

[Action]

In the present invention, since the portion corresponding to the electrode needle of the proposed device is formed in the electrode pattern forming portion of the circuit board as the detection electrode pattern, the output terminal of the ceramic resonator and the extended tip surface of the detection electrode pattern Is a constant value with no variation, and the distance is calculated as nλ / 4 ± λ
It becomes easy to set an appropriate value while avoiding the area of / 10, and it becomes possible to stabilize the detection performance of the device.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.
In the description of the present embodiment, the same parts as those of the proposed device are designated by the same reference numerals, and the duplicated description will be omitted.

1 to 3 show an embodiment of the electrostatic sensor device according to the present invention. In these figures, a ceramic resonator as a tuning circuit is disposed on the ground mounting surface 9 on one side of the printed circuit board 6 functioning as a circuit board, similarly to the proposed device, and the oscillation circuit 1 and the detection circuit are detected. Circuits (not shown) such as the circuit 4 and the amplifier circuit 5 are formed. In this embodiment, two circuits of the ceramic electrostatic device are formed, and along with this, two ceramic resonators as a tuning circuit are also arranged, and both ceramic resonators 7a and 7b have output terminals 8a. , 8b are arranged close to each other. Insert holes 13a and 13b into which the output terminals 8a and 8b are inserted are formed on the printed circuit board 6, and the output terminals 8a and 8b of the corresponding ceramic resonators 7a and 7b are inserted into the insertion holes 13a and 13b. It is fixed.

An electrode pattern forming portion 14 is formed on the printed circuit board 6 so as to project outward with the portion where the ceramic resonators 7a and 7b are provided as the base side. Detection electrode patterns 15a and 15b are formed on the surface of the electrode pattern forming portion 14 by using an appropriate means such as baking, etching, vapor deposition or the like. The base end sides of the detection electrode patterns 15a and 15b include corresponding insertion holes 13a and 13b, respectively, and the output terminals 8a and 8b of the ceramic resonators 7a and 7b of the respective channels are inserted into the insertion holes 13a and 13b. In this state, it is soldered to the corresponding detection electrode patterns 15a and 15b. The detection electrode patterns 15a, 15b
As shown in FIG. 2, the tip side of the electrode pattern forming portion 14
To the tip position, and the extended tip surfaces of the pattern are detection electrode surfaces 16a, 16b facing the object to be detected (not shown) for detecting capacitance change.

The electrode pattern forming unit 14 further includes a detection electrode pattern.
Ground patterns 17a, 17b, 17c are provided between the outside of 15a, 15b and the detection electrode patterns 15a, 15b, and the detection electrode pattern 15a is sandwiched by the ground patterns 17a, 17b,
Further, the detection electrode pattern 15b is a ground pattern 17b, 17c.
The detection electrode patterns 15a and 15b are electrostatically cut off by the ground pattern 17b to suppress variations in the fixed capacitance C ₀ around the patterns 15a and 15b. The base ends of the ground patterns 17a, 17b, 17c are connected to the ground mounting surface 9. A conductor pattern 18 is formed on the opposite surface of the electrode pattern forming portion 14 and blocks an electric field that penetrates the detection electrode patterns 15a and 15b from the outside of the pattern 18 through the inside of the printed circuit board 6. .

The circuit forming portion of the printed circuit board 6 is covered with the conductor case 12, and the electrode pattern forming portion 14 projects outward from an opening provided in the conductor case 12. The electrode pattern forming portion 14 is covered with a cylindrical protective cover 20 formed of a conductor, and the base end side of the protective cover 20 is fixed to the conductor case 12 by screwing or the like.
In the present embodiment, the tip surface of the protective cover 20 and the protruding tip surface of the electrode pattern forming portion 14, that is, the tip surface of the protective cover 20 and the detection electrode patterns 16a, 16b of the detection electrode patterns 15a, 15b are on the same plane. They are matched with each other, and the tip end surface of the protective cover 20 can be used as a reference surface for determining the distance between the object to be detected and the detection electrode surfaces 16a and 16b.

The device of the present embodiment, similarly to the electrode needle 11 of the proposed device, the detection electrode surface 16a, 16b facing the object to be detected, it is possible to detect the change in the small capacitance due to the movement of the object to be detected. so,
Voltage detection signals are taken out from the corresponding ceramic resonators 7a and 7b. According to this embodiment,
Since the detection electrode patterns 15a and 15b are integrally formed on the printed circuit board 6, the ceramic resonators 7a and 7b are formed.
It is possible to accurately set the distance from the output terminals 8a, 8b of b to the corresponding detection electrode surfaces 16a, 16b to a distance avoiding the region of nλ / 4 ± λ / 10 where the resonance frequency becomes unstable, As a result, stabilization of the device detection performance can be achieved.

In addition, even if the plurality of channels of the detection electrode patterns 15a and 15b are formed on the printed circuit board 6 in close proximity to each other, both patterns 15
Since a ground pattern 17b is provided between a and 15b to electrostatically block it, mutual interference of radio waves emitted from the detection electrode patterns 15a and 15b can be prevented, and the stray distribution capacitance is uniform. Since the resonance frequency is stabilized, the circuit operation of the electrostatic sensor device of each channel can be stabilized accordingly. In addition, the detection electrode patterns 15a, 15b
The ground patterns 17a, 17c and the conductor pattern 18 have achieved an electrostatic shield effect from the surrounding circuits and the like due to the electrostatic shield effect, and furthermore, the conductor protective cover 20 shields radio wave radiation internally and externally. It is possible to further stabilize the circuit operation.

Further, since each detection electrode pattern 15a, 15b is protected against external force by the protective cover 20, the detection electrode patterns 16a, 16b of the detection electrode patterns 15a, 15b may contact or collide with other members. It is possible to improve the reliability of the electrostatic detection unit without being damaged and to prolong the life of the device.

Further, since the device configuration is extremely simple, the device can be easily manufactured, and the device cost can be reduced.

The present invention is not limited to the above embodiment,
Various embodiments may be adopted. For example, although the printed circuit board is used as the circuit board in the above embodiment, it may be formed of a multilayer board.

Further, in the above embodiment, the circuit of the two-channel electrostatic sensor device is formed on the printed circuit board, but the circuit of three or more channels may be formed, or the circuit of only one channel may be formed.

Further, in the embodiment, the conductor pattern 18 is formed on the surface of the printed board opposite to the surface on which the detection electrode patterns 15a and 15b are formed, but the conductor pattern 18 can be omitted.

[Effect of device]

According to the present invention, an electrode pattern forming portion is formed to project on a circuit board, a detection electrode pattern is formed integrally with the circuit board on the electrode pattern forming portion, and the base end side of the detection electrode pattern is used as an output terminal of a ceramic resonator. Since the extension tip surface of the detection electrode pattern is connected and formed as the detection electrode surface, the distance from the output terminal of the ceramic resonator to the detection electrode surface can be formed to a constant value without variation. . Therefore, the distance can be accurately set to a distance that avoids the length at which the resonance frequency becomes unstable, and the detection performance of the device can be stabilized.
Further, since the device configuration is simple and the device is easily manufactured, the excellent device of the present invention can be provided at low cost.

[Brief description of drawings]

FIG. 1 is a sectional view showing the construction of an essential part of an electrostatic sensor device according to an embodiment of the present invention. FIG. 2 is a front view of the device of the same embodiment.
2 is a side view with a part of FIG. 2 omitted, FIG. 4 is a block diagram showing a circuit configuration of one channel of an electrostatic sensor device using a ceramic resonator, and FIG. 5 is electrostatic capacitance detection of the electrostatic sensor device. Fig. 6 is an explanatory diagram of an example, Fig. 6 is an explanatory diagram of a proposed device using a ceramic resonator, and Fig. 7 is a characteristic explanatory diagram showing the relationship between the distance from the output terminal of the ceramic resonator to the tip of the electrode needle and the resonance frequency. is there. 1 ... Oscillation circuit, 2 ... Tuning circuit, 3 ... Detector, 4 ...
… Detector circuit, 5 …… Amplifier circuit, 6 …… Printed circuit board, 7,
7a, 7b …… Ceramic resonator, 8,8a, 8b …… Output terminal, 9
...... Ground mounting surface, 10 …… conductor pattern, 11 …… electrode needle, 12 …… conductor case, 13a, 13b …… insertion hole, 14 …… electrode pattern forming part, 15a, 15b …… detection electrode pattern, 16
a, 16b …… Detection electrode surface 17a, 17b, 17c …… Ground pattern, 18 …… Conductor pattern, 20 …… Protective cover.

Claims (1)

(57) [Scope of utility model registration request] 1. An electrostatic sensor device comprising a resonator as a ceramic resonator, wherein a base side of a circuit board on which the ceramic resonator is mounted is housed in a conductor case, and an opening of the conductor case is provided. The electrode pattern forming portion of the circuit board is formed so as to project to the outside of the conductor case, and the detection electrode pattern is formed on the electrode pattern forming portion of the electrode pattern forming portion from the base end side to the tip end side of the electrode pattern forming portion. The detection electrode pattern is formed to extend in the projecting direction, the base end side of the detection electrode pattern is connected to the output terminal of the ceramic resonator, and the extension front end surface of the detection electrode pattern is a detection electrode for capacitance change facing the object to be detected. The electrostatic sensor device that is the surface.