JPH01127909A - Capacitance type stroke sensor - Google Patents

Abstract

PURPOSE:To eliminate the mechanical consumption and to improve the durability by providing a pair of differential electrodes on a substrate, and also, providing a common electrode which is opposed to said electrodes and can move by holding a prescribed interval. CONSTITUTION:When a common electrode 9 moves in the direction as indicated with an arrow, its opposed area to differential electrodes 7 (7a, 7b) and guide rails 8a, 8b is varied continuously from a part of oblique lines to a part of broken lines as shown in a figure (a). Accordingly, each capacitance Ca, Cb of the electrode 9 and the electrodes 7a, 7b is varied as shown in a figure (b), therefore, by bringing these capacitances to DC conversion by each capacity- voltage converting circuit, an output voltage characteristic being proportional to a moving distance of the electrode 9 can be obtained as shown in a figure (c). In such a way, as for a position detection of the common electrode 9, the capacitance between the common electrode of non-contact and the differential electrodes can be detected, therefore, even if this sensor is used for a vehicle, etc. to which vibration, etc., are always applied, the mechanical consumption is not caused, and the durability is not deteriorated.

Description

DETAILED DESCRIPTION OF THE INVENTION INDUSTRIAL APPLICATION J Field of the Invention The present invention relates to a stroke sensor installed in a vehicle, agricultural machine, etc., for detecting the positional relationship or moving distance of component members.

"Prior Art" FIG. 5 is a side view showing a conventional stroke sensor, in which 1 is a housing, 2 is a slide plate, and a contact 3 is provided at the tip of the slide plate. Reference numeral 4 denotes a substrate, on the upper surface of which a resistor 5 is provided, for example, by coating, and the contactor 3 is configured to slide on the resistor 5. Therefore, if the slide plate 2 is fixed to a moving object, the detected resistance value changes as the slide plate 2 moves, and a resistance value proportional to the moving distance of the slide plate 2 can be obtained.

"Problems to be Solved by the Invention" However, since the above-mentioned conventional configuration has a structure in which the contactor 3 is in contact with the resistor 5, it is difficult to use it in vehicles, agricultural machinery, etc. that are subject to constant vibrations. , resistor 5
It has the drawback that it is subject to rapid wear and tear, resulting in reduced durability.

Therefore, in the present invention, a pair of differential electrodes are provided on a printed wiring board, and a common electrode is provided that faces the pair of differential electrodes and is movable while maintaining a constant spacing. established,
As the common electrode moves, the opposing area between one of the pair of differential electrodes and the common electrode continuously increases, and the opposing area between the other differential electrode and the common electrode continuously decreases. .

"Example" FIG. 1 is an embodiment of the capacitive stroke sensor according to the present invention, and FIG. 2 is a cross-sectional view of the same, in which 6 is a printed circuit board, and 7a and 7b are formed on the printed circuit board 6. The conductor pattern constitutes a pair of differential electrodes. Guide rails 8a and 8b are made of metal members such as brass. Reference numeral 9 denotes a common electrode made of a metal member, and guide rails 8a,
8b so as to be slidable. 10 is an oscillator, lla and llb are capacitance/voltage conversion circuits that convert capacitance into DC voltage, 12a and 12b are rectification/impedance conversion circuits, and 13 is a differential amplifier circuit.

Next, the operation will be explained. When the common electrode 9 moves in the direction of the arrow, the differential electrodes 7a, 7b and the guide rail 8a
, 8b and the common electrode continuously change from the diagonally shaded area to the broken line area as shown in FIG. Therefore, the common type f! 9 and differential type 1) The opposing area of i7a is S
a, Sb is the opposing area of the common electrode 9 and the differential type i7b, d is the inter-electrode gap between the common electrode 9 and the differential electrodes 7a and 7b, and ε0 is the dielectric constant in air. The capacitance iCa of the electrode 7a = εoS a/d and the capacitance cb of the common electrode and the differential electrode 7b = εoSb/d, which change as shown in FIG. 4(A). Therefore, the capacitance 1Eca and Cb are converted into capacitance/voltage conversion circuits 11a and 11b.
By converting the voltage into a DC voltage, it is possible to obtain an output voltage characteristic proportional to the moving distance of the common electrode as shown in FIG. 4(B).

FIG. 6 shows another embodiment of the present invention, in which the same parts as in FIG. 1 are given the same reference numerals. Differential electrode 7a.

The printed circuit board 6 on which the parts 7b are formed is formed into a cylindrical shape, and the common TFI 9 disposed on a guide rail 8 formed in a cylindrical shape slides in the hollow part of the printed circuit board 6. The inter-electrode gap d in this embodiment is a gap formed by the thickness of the printed circuit board 6, the inner wall of the printed circuit board 6, and the surface of the common electrode 9. Further, the gap may be filled with a silicone oil or the like.

[Effects of the Invention] As explained above, according to the present invention, the position of the common electrode is detected by detecting the capacitance between the common electrode and the differential electrode in a non-contact manner, so that the vehicle is constantly subjected to vibrations and the like.

Even when used in agricultural machinery, etc., there is no mechanical wear and tear, and there is no decrease in durability, unlike conventional methods.In addition, by using a cylindrical printed circuit board as shown in Figure 6, a small stroke sensor can be used. can be provided.

[Brief explanation of the drawing]

Fig. 1 is an embodiment of the capacitive stroke sensor according to the present invention, Fig. 2 is a cross-sectional view of the same, Fig. 3 is an explanatory diagram of operation, Fig. 4 is an operation characteristic diagram, and Fig. 5 is a conventional technique. FIG. 6 is a side view of a stroke sensor according to another embodiment of the present invention. 1....... Housing, 2...... Slide plate, 3... Contact, 4, 6...
. . . Substrate, 5 . . . Resistor, 7a. 7b......Differential electrode, 8.8a, 8b...
...... Guide rail, 9... Common electrode, IO... Oscillator, 11a, ll
b・・・・・・Capacity/voltage conversion circuit, 12, 1
2b: Rectification/impedance conversion circuit, 13: Differential amplifier circuit Patented by President and CEO of Taiko Denki Seisakusho Co., Ltd. 1) Takehiko

Claims (1)

[Claims] A pair of differential electrodes is provided on a printed wiring board, and a common electrode is provided that faces the pair of differential electrodes and is movable while maintaining a constant interval, and as the common electrode moves, the pair of differential electrodes A capacitive stroke sensor characterized in that when the facing area between one of the electrodes and the common electrode increases continuously, the facing area between the other differential electrode and the common electrode continuously decreases.