JPH0644103U - Potentiometer - Google Patents

Abstract

(57) [Summary] (Modified) [Purpose] To provide a potentiometer that has a long life and can be used in a wide temperature range. [Arrangement] An annular resistor 14 having both open ends is arranged on a base 2. The rotating shaft 4 located at the center of the
The base 2 is rotatably inserted through a bearing 5. A movable electrode 16 is provided on an electrode arm 15 attached to the rotary shaft 4, and the movable electrode 16 is connected to a resistor 14 via an insulator 17.
To form a first capacitor. A fixed electrode 18 is provided on the base 2, and the fixed electrode 18 is opposed to the one end portion 14b of the resistor 14 with the insulator 17 interposed therebetween to form a second capacitor. Input ends 14a, 14 of the resistor 14
By applying an alternating current to a, a reduced voltage is generated in each of the movable electrode 16 and the fixed electrode 18. Movable electrode 1
The voltage generated at 6 increases or decreases as the movable electrode 16 moves.
Then, the rotation angle and the amount of displacement of the object to be detected are detected via the rotary shaft 4.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a potentiometer used for an automatic control system or the like.

[0002]

[Prior art]

 The adoption of automatic control methods is increasing in various industrial fields. In this automatic control method, a sensor for feedback is used for various purposes, and the demand for the sensor is also increasing. Applications of this sensor include, for example, detection of rotation angle and displacement amount.

There are various types of sensors for detecting the absolute value (analog amount) of the rotation angle and the displacement amount, and a contact type potentiometer is representative. As shown in FIGS. 4 and 5, the resistor 1 made of a resistance wire or a conductive plastic element is bent into an annular shape with both ends open, and is placed on the inner surface of the circumferential wall 2a of the base 2. Input terminals 3 are provided at both ends of the resistor 1.

A rotary shaft 4 is arranged at the center of the resistor 1, and the rotary shaft 4 rotatably inserts the base 2 through a bearing 5. A base end of a movable arm 6 is fixed to the rotary shaft 4, and a brush 7 provided at the tip of the movable arm 6 is in sliding contact with the resistor 1. A slip ring 8 is attached to the rotary shaft 4, and the slip ring 8 and the movable arm 6 are electrically connected via the rotary shaft 4 which is a conductor or by direct contact. Further, one end of the conductive wire 9 is in contact with the concave groove 8a of the slip ring 8, and the output terminal 10 is provided at the other end of the conductive wire 9.

According to the contact-type potentiometer, when the brush 7 is rotationally displaced integrally with the rotary shaft 4, the voltage of the output terminal 3 changes, and the absolute value of the resistance division ratio of the resistor 1 varies depending on the position of the brush 7. Thus, the rotation angle of the rotary shaft 4 and the absolute value of the displacement amount can be detected. Since this potentiometer uses the resistance partial pressure of the resistor 1, it is not affected by temperature changes and can be used in an environment of a wide temperature range of -40 ° C to + 150 ° C. However, this potentiometer has the drawbacks that the sliding of the brush 7 causes abrasion of the resistor 1, which deteriorates the detection accuracy and shortens the service life, and causes large sliding noise during sliding.

[0006] On the other hand, there is a potentiometer in which the detecting portion is not in contact with the potentiometer to obtain a long life. In this potentiometer, as shown in FIGS. 6 and 7, two magnetoresistive elements 11, 11 each having a substantially semi-arcuate shape are arranged on the base 2 with their centers of curvature in common. A conductive wire 12 is connected between the magnetoresistive elements 11 and 11 and input terminals 3 are provided at the other ends of the magnetoresistive elements 11 and 11, respectively.

At the center of curvature of the magnetoresistive elements 11 and 11, a rotary shaft 4 is provided penetrating the base 2. A substantially semicircular permanent magnet 13 is arranged as a magnetic field source on the rotary shaft 4. It is set up. The permanent magnet 13 rotates integrally with the rotating shaft 4 in close proximity to the magnetoresistive elements 11 and 11, and at this time, the magnetic field applied to the magnetoresistive elements 11 and 11 changes.

The potentiometer utilizes that the internal resistance of the magnetoresistive element changes when a magnetic field is applied to the element. That is, as the permanent magnet 13 rotates, the resistance values of the magnetoresistive elements 11 and 11 facing the permanent magnet 13 increase or decrease, and the position of the permanent magnet 13 is obtained. According to this non-contact type potentiometer, mechanical deterioration does not occur in the detecting portion, so that its life can be extended. However, the permanent magnet 13 is prone to deterioration of magnetic characteristics due to aging, and thus has a problem in detection accuracy. Further, since the magnetoresistive elements 11 and 11 which are semiconductors have poor temperature characteristics, some temperature compensation must be taken into consideration in order to use them in a wide temperature range.

[0009]

[Problems to be solved by the device]

 By the way, the potentiometer, which is a sensor that detects the absolute value of the rotation angle and the amount of displacement, is an important issue in terms of expanding the applicable temperature range and extending the service life in order to achieve accurate control in adverse environments. Has become. However, a potentiometer with a contact-type detector as described above can extend the temperature range, but it is difficult to extend its life. On the other hand, a non-contact potentiometer with a detection unit can extend the service life, but it has problems in detection accuracy and it is difficult to expand the temperature range, making it suitable for both contact and non-contact potentiometers. There were merits and demerits.

It is an object of the present invention to solve the two problems of expanding the applicable temperature range and extending the service life, and to provide a potentiometer that solves the problem of detection error due to temperature change.

[0011]

[Means for Solving the Problems]

 In order to achieve the above-mentioned object, the potentiometer according to the present invention comprises a low antibody pattern formed on a fixed support and having a predetermined current applied thereto, an insulator layer formed on the resistor pattern, and the insulator. A fixed electrode that is slidable on the layer and a fixed electrode that is connected and arranged on the insulator layer above one end face of the resistor pattern, and the fixed electrode that moves as the movable electrode moves. It is characterized by detecting the voltage change of the movable electrode with respect to the reference voltage.

It is preferable that the fixed electrode and the movable electrode have the same area, and the distance between the fixed electrode and one end of the resistor is equal to the distance between the movable electrode and the resistor.

[0013]

[Action]

 According to the above configuration, when an alternating current is passed through the resistor, a certain amount of attenuated potential is generated in the movable electrode via the first capacitor formed between the resistor and the movable electrode, and this movable electrode When is slid, a change proportional to the potential difference with the resistor is generated on the movable electrode, and the displacement of the movable electrode can be detected. At this time, the movable electrode acts as a pseudo brush instead of the brush in the contact-type potentiometer, and a potentiometer in which the resistor does not wear is realized. Further, the output fluctuation due to the deformation of the material due to the temperature change of the insulator layer can be taken out from the fixed electrode through the second capacitor formed between the end of the resistor and the fixed electrode.

[0014]

【Example】

 An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a perspective view of a potentiometer according to an embodiment, FIG. 2 is a sectional view, and FIG. 3 is a processing circuit diagram. In this embodiment, a resistor 14 composed of a ring-shaped resistor element having open ends is mounted on the upper surface of a base 2 which is an insulating support, and the input ends 14a and 14a of the resistor 14 have an AC power source. Input terminal of is connected. An insulator 17 having a uniform thickness is attached to the upper surface of the resistor 14.

A rotary shaft 4 that rotatably penetrates the base 2 via a bearing 5 is provided at the center of the resistor 14, and the base end of the electrode arm 15 is attached to the rotary shaft 4. ing. A movable electrode 16 made of a conductor is provided at the tip of the electrode arm 15. The movable electrode 16 is arranged in contact with the surface of the insulator 17, and slides on the insulator 17 integrally with the rotating shaft 4. In this case, it is preferable that the electrode arm 15 is provided with elasticity so that no gap is formed between the movable electrode 16 and the insulator 17.

A slip ring 8 having a U-shaped cross section in the radial direction connected to the electrode arm 15 is attached to the rotary shaft 4, and a conductive wire 9 for output is provided in a groove 8 a of the slip ring 8. It is slidably fitted.

The base 2 supporting the resistor 14 is provided with a fixed electrode 18 in addition to the movable electrode 16. The fixed electrode 18 is arranged at one end 14 b of the resistor 14 and is provided in contact with the upper surface of the insulator 17. The fixed electrode 18 is provided in order to solve the problem of measurement error caused by using the insulator 17 as the insulating layer.

The insulator 17 is originally provided to keep the distance between the movable electrode 16 and the resistor 14 constant. In other words, since the rotary shaft 4 is only supported by the base 2 via the bearing 5, it easily tilts with respect to the base 2. In this case, the distance between the movable electrode 16 and the resistor 14 changes, and the measurement error Cause. However, by mounting the insulator 17 on the upper surface of the resistor 14 and sliding the lower surface of the movable electrode 16 in contact with the surface of the insulator 17, the insulator 17 functions as a spacer. The distance between the movable electrode 16 and the resistor 14 can be kept constant, and the detection accuracy can be improved.

On the other hand, when the insulator 17 is used, the space dimension of the insulating layer changes due to the expansion and contraction of the material due to the temperature change of the insulator 17, and the dielectric constant of the first capacitor changes, resulting in an error in detection accuracy. Occurs.

Therefore, in this embodiment, the fixed electrode 18 is provided separately from the movable electrode 16. That is, in addition to the first capacitor formed between the movable electrode 16 and the resistor 14, the second capacitor having the same capacitance as the first capacitor is provided between the fixed electrode 18 and the one end 14b of the resistor 14. Capacitor is formed, and the second capacitor is provided so as to detect a capacitance change due to a temperature change of the insulator 17 and compensate for it in a circuit manner.

The operation of the potentiometer as a whole as well as the operation of the second capacitor will be described below.

When an AC power source is connected to the input ends 14a, 14a of the resistor 14 and a current is passed, the movable electrode 16 and the fixed electrode 18 are attenuated by capacitor coupling with the resistor 14 and one end 9b thereof. The obtained voltage is obtained.

In this case, a voltage difference with a constant amplitude is generated between the movable electrode 16 and the resistor 14, and this voltage difference increases or decreases in proportion to the position of the movable electrode 16 and changes in proportion to this. It occurs on the movable electrode 16. Therefore, by measuring the output of the movable electrode 16 provided on the rotary shaft 4, the rotation angle and displacement amount of the rotary shaft 4 can be detected.

However, if the insulator 17 expands and deforms due to a temperature change and the permittivity between the resistor 14 and the movable electrode 16 changes, this change naturally causes a detection error and is compensated for in a circuit manner. There is a need to. FIG. 5 shows an example of the processing circuit of the potentiometer of this embodiment. As shown in the figure, voltage measuring devices 19 and 20 are connected to the movable electrode 16 and the fixed electrode 18, respectively, and the output signal of the voltage measuring device is input to the arithmetic processing unit 21.

Further, temperature compensation of the potentiometer will be described with reference to the circuit of FIG. The voltage of the AC power supply 23 is V, the input current is I, the resistance of the resistor 14 is R ₀ , the resistance value between the movable electrode 16 and the resistor 14 is R ₁ , the capacity of the first capacitor is C ₂ , If the capacitance of the second capacitor is C ₁ , the output of the first capacitor is V ₂ , and the output of the second capacitor is V ₁ , then V = IR _O , V ₁ = 1 / jwC ₁ · I V ₂ = R ₀ / R ₁ (1 / jwC ₂ · I), and when C ₁ = C ₂ holds, V ₂ = R ₁ / R ₀ V ₁ .

Then, the temperature change occurs equally in the first capacitor and the second capacitor as an in-phase disturbance, and as a result, the capacitances C ₁ and C ₂ are not affected by the temperature change. Also, the antibody 14 is not affected by the temperature change because of the partial pressure ratio R ₁ / R ₀ . Therefore, when the input current I of the capacitor changes due to the temperature change, the outputs V ₁ and V ₂ change respectively, and in that case, it is canceled by setting V ₂ / V ₁ etc. in the arithmetic processing unit 21 in the subsequent stage. it can. In the above case, the area of the movable electrode 16 and the fixed electrode 18 are made the same as the simplest means of setting C ₁ = C _2, and the electrodes 16, 18 and the resistor 14 and the one end portion 14b of the same are not used. The distance between them should be the same.

Next, characteristics of the first and second capacitors formed by the movable electrode 16 and the fixed electrode 18, the resistor 14 and the one end portion 14b thereof will be described. The impedance Z formed between the two electrodes 16 and 18 and the resistor 14 is Z = 1 / jwc = 1 / ε ₀ ε _S w = 2πf. Here, c is the capacitance, f is the oscillation frequency, ε _S is the dielectric ratio of the insulator, S is the effective area of the electrode, and 1 is the distance between the electrode and the resistor.

As can be seen from the above equation, there are the following three ways to reduce the impedance Z in order to improve the sensitivity of the potentiometer. Raise the transmission frequency f. A material having a high dielectric constant ε _S is used for the insulator 17. The thickness of the insulator 17 is reduced. Regarding, when is increased too much the oscillation frequency 5, since the dielectric component of the electrode arm 15 and the conductive wire 9 is increased, it is preferable to drive between several tens H _Z ~ several hundred H _Z. With regard to (1) and (2), since it is necessary to attach importance to the fact that the material of the insulator 17 has no water absorption and the coefficient of friction is small, the sensitivity is increased by reducing the thickness of the insulator 17.

Further, it is desirable that the electrode arm 15 is provided at a right angle to the sliding direction of the resistor 14 and the movable electrode 16. This is because if there is a resistor 14 in a portion facing the electrode arm 15, a capacitance is generated between the resistor and the stray capacitance, and the linearity of the output deteriorates.

In the above embodiment, the resistor 14 is formed in an annular shape, the movable electrode 16 is attached to the rotary shaft 4, and a potentiometer for detecting the rotation angle and the amount of rotational displacement is provided. Although shown, the invention is not so limited. For example, a potentiometer for detecting a linear displacement amount can be configured by making the resistor 14 into a rectangular shape and sliding the movable electrode 16 along a straight line (however, not shown).

Further, the insulator 17 for maintaining the gap between the movable electrode 16 and the resistor 14 may be provided on the movable electrode 16 side instead of being provided on the resistor 14 side. Other arrangements, shapes, etc. of the electrodes 16 and 18 and the resistor 14 may be changed as necessary.

[0033]

[Effect of device]

 According to the potentiometer of the present invention, since the detection unit is not in contact, mechanical deterioration does not occur in the detection unit, the detection accuracy can be maintained for a long time, and the life of the potentiometer can be extended. Further, in the present invention, since the detection current can be taken out by the first capacitor and the second capacitor, by detecting this output ratio as the measured value, the detection error due to the temperature change of the insulator can be detected in a circuit. It becomes possible to compensate.

Further, the potentiometer of the present invention uses a non-contact type detection unit, but it is not a magnetic type. Therefore, unlike the conventional non-contact potentiometer using magnetism, the deterioration of the magnetic characteristics due to the change in the rate of the permanent magnet is not caused. However, there is no problem such as a decrease in detection accuracy. Also, since it does not use magnetism, it has good temperature characteristics and can be used in a wide temperature range.

[Brief description of drawings]

FIG. 1 is a perspective view of a potentiometer according to an embodiment of the present invention.

2 is a partial cross-sectional view of the potentiometer of FIG.

FIG. 3 is an equivalent circuit diagram of the potentiometer of FIG.

FIG. 4 is a cross-sectional explanatory view of a conventional contact potentiometer.

5 is a vertical partial sectional view of the potentiometer of FIG.

FIG. 6 is a cross-sectional view of a conventional non-contact potentiometer.

FIG. 7 is a vertical partial sectional view of the potentiometer of FIG.

[Explanation of symbols]

2 ... Base, 4 ... Rotating shaft, 14 ... Resistor, 15 ... Electrode arm, 16 ... Movable electrode, 17 ... Insulator, 18 ... Fixed electrode.

Claims (2)

[Scope of utility model registration request] 1. A resistor pattern formed on a fixed support to which a predetermined current is applied, an insulator layer formed on the resistor pattern, and a movable electrode slidable on the insulator layer. And a fixed electrode that is connected and arranged on the insulator layer above one end surface of the resistor pattern, and detects a voltage change of the movable electrode with respect to a reference voltage of the fixed electrode due to movement of the movable electrode. A potentiometer characterized by: 2. The fixed electrode and the movable electrode have the same area, and the distance between the fixed electrode and one end of the resistor is set equal to the distance between the movable electrode and the resistor. The potentiometer according to claim 1.