JPH06137807A - Noncontact type potentiometer - Google Patents

Abstract

PURPOSE:To provide a noncontact type potentiometer which is long in its life and can be used in a wide temperature range. CONSTITUTION:A plurality of electrodes 15 to 17 respectively composed of a conductive body are oppositely arranged to form two or more parallel plate capacitors connected in series, and movable plates 19, 20 respectively formed of the conductive body are arranged having a space from the electrodes on both sides and about parallel to the electrode in each parallel plate capacitor. Since the movable plates 19, 20 are attached to a rotary shaft 18 so as to be mutually electrically insulated and shifted in their positional relationship to a rotation center, a detection section is noncontactingly composed to have a long life, and even if inclination or looseness occurs in the movable plate within a range where the movable plate does not come into contact with the electrode, the capacity of the detection section is not influenced and fixed, and the structure of a potentiometer therefore becomes simple. In addition, a differential capacitor C is formed to theoretically offset the influence of temperature change, and thus the potentiometer can be used in a wide temperature range.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-contact potentiometer for electrically detecting rotational displacement.

[0002]

2. Description of the Related Art Conventionally, as a potentiometer, a contact type using a resistance wire or a resistance element or a non-contact type using a magnetoresistive element has been known. Such potentiometers include the contact type shown in FIG. 6 and the non-contact type shown in FIG.

The contact type potentiometer shown in FIG.
A transmission shaft 1 supported by bearings for transmitting rotation, a rotary plate 2 attached to the transmission shaft 1, a brush 3 for detection attached to the rotary plate 2, and a resistor 4 slid by the brush 3. And the rotational displacement amount is detected by the resistance between terminals obtained by the contact position of the brush 3. Reference numerals 5, 6, and 7 are terminals.

The non-contact potentiometer shown in FIG. 7 has a transmission shaft 8 supported by bearings for transmitting rotation, a permanent magnet 9 fixed to the transmission shaft 8, and symmetrically arranged about the transmission shaft 8. It is composed of two magnetoresistive elements 10 and 11, and by utilizing the fact that the resistance value of the element increases and decreases due to the change of the magnetic field strength of the permanent magnet 9, the rotational displacement is obtained by taking the difference between the resistances of the elements. Detect the amount. In addition,
Reference numerals 12, 13, and 14 are terminals.

[0005]

However, in the contact type shown in FIG. 6, the brush and the resistor come into contact with each other and wear occurs, so that there is a problem in service life. On the other hand, in the non-contact type using the magnetoresistive element shown in FIG. 7, the magnetic characteristic applied to the element is weakened due to the change over time of the magnetic characteristic of the permanent magnet, and the characteristic is deteriorated. Furthermore, since the element is a semiconductor, it has poor temperature characteristics, and there is a problem that temperature compensation must be added when used in a wide temperature range.

The present invention has been made in view of the above problems, and an object thereof is to provide a non-contact potentiometer which has a long life and can be used in a wide temperature range.

[0007]

In the non-contact potentiometer of the present invention, a plurality of electrodes made of a conductor are arranged to face each other to form a parallel plate capacitor in which two or more electrodes are connected in series. A movable plate made of a conductor is placed in parallel with the electrodes on both sides of the capacitor in parallel with the electrodes, and these movable plates are electrically insulated from each other and attached to the rotating shaft with a phase relationship shifted with respect to the center of rotation. It is what has been.

[0008]

When the movable plate made of a conductor is inserted between the parallel plate capacitors made of a pair of electrodes, two parallel plate capacitors connected in series are formed between the electrodes on both sides of the movable plate. This is equivalent in capacitance to one capacitor in which the distance L between the electrodes is reduced to L-t (where t is the thickness of the movable plate). The capacitance C between the electrodes in the portion where the movable plate of such a capacitor is inserted is C = ε ₀ · S / (Lt) where S is the area of the electrode in that portion, and the area S is By constantly changing according to the rotation of the shaft, the capacitance of the capacitor changes linearly according to the rotation angle.

In the non-contact potentiometer of the present invention, the area of the movable plate facing the electrodes is constantly changed by the rotation of the transmission shaft, which changes the apparent distance between the electrodes. Each capacity changes linearly according to the rotation angle. Therefore, the output (potential) obtained by the differential capacitor formed by these parallel plate capacitors also changes according to the rotation angle, so that the rotational displacement amount of the rotary shaft is detected.

For example, the capacitances C ₁ and C ₂ of _two parallel plate capacitors connected in series change linearly according to the rotation angle, and the output obtained by the differential capacitor composed of these parallel plate capacitors. (Potential between two parallel plate capacitors) becomes C ₁ / (C ₁ + C ₂ ) or C ₂ / (C ₁ + C ₂ ) and changes according to the rotation angle. To be detected.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A non-contact potentiometer according to a first embodiment of the present invention will be described below with reference to FIGS.

The non-contact potentiometer of this embodiment is
The differential capacitor C as shown in FIG. 1 is the main component. The differential capacitor C has a structure in which electrode plates 15, 16, 17 (electrodes) made of a conductor and having the same area are opposed to each other, and two parallel plate capacitors are connected in series. The movable plates 19 and 20 made of a conductor are provided between the electrode plates 16 and 17 and between the electrode plates 16 and 17, respectively.
5, 16 and 17 are arranged substantially parallel to each other, and respective movable plates 19 and 20 are positioned with respect to the transmission shaft 18 (rotation shaft) transmitting the rotation via insulators 21 and 22. Attached with a phase difference of π (180 °), electrode plates 15, 1
Areas of the portions of the parts 6 and 17 facing the movable plates 19 and 20 are constantly changed by rotation. In addition, the input terminals 23 and 24 are drawn out from the electrode plates 15 and 17,
An output terminal 25 is drawn out from the electrode plate 16.

As shown in FIG. 2, the differential capacitor C has an input terminal 23, 24 connected to an AC power supply D, and an output terminal 25 connected to an amplifier A and a rectifier circuit S to be incorporated in a detection circuit. , Constitutes a non-contact potentiometer.

In this non-contact potentiometer, the rotation of the transmission shaft 18 causes the areas where the electrode plates 15 and 16 and the movable plate 19 face each other and the areas where the electrode plates 16 and 17 and the movable plate 20 face each other to be linear according to the rotation angle. Change to the electrode plate 1
Since the capacity of the parallel plate capacitors composed of 5 and 16 and the capacity of the parallel plate capacitors composed of the electrode plates 16 and 17 also change linearly according to the rotation angle, the difference composed of these parallel plate capacitors is Since the output (potential of the output terminal 25 connected to the electrode plate 16) obtained by the dynamic capacitor C changes according to the rotation angle with the output characteristics shown in the graph of FIG. 3, for example, the rotation of the transmission shaft 18 The displacement amount is detected.

Next, a non-contact potentiometer according to a second embodiment of the present invention will be described with reference to FIGS. 4 and 5.

The non-contact potentiometer of this embodiment is
The main structure is a differential capacitor C as shown in FIGS. 4 and 5. In this differential capacitor C, substrates 26, 27, 28 made of an insulator are arranged with a space therebetween via a spacer 33, and conductors are provided on both surfaces of the substrate 27 and the surfaces of the substrates 26, 28 facing these surfaces. Electrode layer 2
9, 30, 31, 32 (electrodes) are formed in a semi-circular shape, and the movable plates 19, 20 in a substantially semi-circular shape made of a conductor are formed between the substrates 26, 27 and the substrates 27, 28, and the electrode layer 29 is formed in the movable plate 19, 20. , 30, 31, 32 are arranged to face each other with a space, so that the capacitances of the two parallel plate capacitors connected in series can be changed. Each of the movable plates 19 and 20 has a transmission shaft 18 as shown in FIG.
Is fixed at a position having a phase relationship of π (180 °) with respect to the rotation center of
Are supported by bearings 34 and 35 as shown in FIG. In addition, the input layers 23 and 24 are connected to the electrode layers 29 and 32.
, The electrode layers 30 and 31 are electrically connected to each other, and the output terminal 25 is drawn out.

The differential capacitor C is incorporated in the detection circuit shown in FIG. 2 shown in the first embodiment to form a non-contact potentiometer.

In these embodiments, the phase difference between the two movable bodies is set to 180 ° because the detection range theoretically becomes maximum when the phase difference is 180 °. However, in the present invention, the phase difference does not necessarily have to be 180 °,
If there is a phase difference, the amount of rotational displacement can be detected.

Further, in these embodiments, two parallel plate capacitors are connected in series, but in the present invention, three or more parallel plate capacitors may be connected in series. Even in that case, the rotational displacement amount can be detected.

[0020]

According to the non-contact potentiometer of the present invention, a plurality of electrodes made of a conductor are arranged to face each other to form two or more parallel plate capacitors connected in series. Since a movable plate made of a conductor is spaced apart from the electrodes on both sides and arranged substantially parallel to the electrodes, the movable plates are electrically insulated from each other and attached to the rotary shaft with a phase relationship shifted with respect to the rotation center. The detector is configured to be non-contact for a long life, and the capacity is not affected even if the movable plate is tilted or rattles in a range where it does not contact the electrodes, so that the structure is simple. Further, by forming a differential capacitor, the effect of temperature change is theoretically canceled out, and it can be used in a wide temperature range.

[Brief description of drawings]

FIG. 1 is a perspective view of a main part of a non-contact potentiometer according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram showing an example of a detection circuit of the non-contact potentiometer of the present invention.

FIG. 3 is a graph showing an example of output characteristics of the non-contact potentiometer of the present invention.

FIG. 4 is a perspective view of a main part of a non-contact potentiometer according to a second embodiment of the present invention.

FIG. 5 is a sectional view of a non-contact potentiometer according to a second embodiment of the present invention.

FIG. 6 is a principle diagram of a conventional contact type potentiometer.

FIG. 7 is a principle diagram of a conventional non-contact potentiometer.

[Explanation of symbols]

 1 Transmission Shaft 2 Rotating Plate 3 Brush 4 Resistor 5 Terminal 6 Terminal 7 Terminal 8 Transmission Shaft 9 Permanent Magnet 10 Magnetoresistive Element 11 Magnetoresistive Element 12 Terminal 13 Terminal 14 Terminal 15 Electrode Plate (Electrode) 16 Electrode Plate (Electrode) 17 Electrode plate (electrode) 18 Transmission shaft (rotating shaft) 19 Movable plate 20 Movable plate 21 Insulator 22 Insulator 23 Input terminal 24 Input terminal 25 Output terminal 26 Substrate 27 Substrate 28 Substrate 29 Electrode layer (electrode) 30 Electrode layer (electrode) ) 31 electrode layer (electrode) 32 electrode layer (electrode) 33 spacer 34 bearing 35 bearing C differential capacitor D AC power supply A amplifier S rectifier circuit

Claims (1)

[Claims] 1. A parallel plate capacitor in which a plurality of electrodes made of a conductor are arranged so as to face each other and two or more electrodes are connected in series, and a movable plate made of a conductor is provided on both sides of each parallel plate capacitor. A non-contact potentiometer which is spaced apart from the electrode and arranged substantially parallel to the electrode, and in which the movable plates are electrically insulated from each other and are attached to the rotating shaft with a phase relationship shifted with respect to the center of rotation.