Capacitor coupled potentiometer

Details Capacitor coupled potentiometer Capacitor coupled potentiometer

1994-03-30

1996-06-11

Walberg, Teresa J.

Electrical resistors

Mechanically variable

Movable contact electrically adjustable over length of...

338 75, 338 92, 338140, 338173, 338178, 338187, 338188, 338189, 338202, H01C 1000

Patent

active

055259553

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

The present invention relates to a potentiometer used in automatic control and the like.


BACKGROUND ART

As sensors for a feedback use in an automatic control system, for example, sensors for detecting the absolute values (analog amounts) of a rotational angle and a displacement amount are known, and a typical one of these sensors is a potentiometer. The potentiometer is classified into a contact type shown in FIGS. 1 and 2, and a non-contact type shown in FIGS. 3 and 4.
As shown in FIGS. 1 and 2, a contact type potentiometer comprises a circular base 2 fixed with a cylindrical wall 2a to the inner surface of which a resistor member 1 is adhered. A rotational shaft 4 is supported by the circular base 2. A brush 7 is attached to the rotational shaft 4 via a movable arm 6, and a slip ring 8 is fixed to the rotational shaft 4. A V-shaped conductive wire 9 is connected to an output terminal 10, and slidably contacts with a recess groove 8a formed by notching the slip ring 8.
The resistor member 1 consists of a metal resistor or conductive plastic to have a C-shaped cross-section, and its two terminals are respectively connected to input terminals 3.3. The rotational shaft 4 is pivotally supported on the bottom portion of the base 2 via a bearing 5, and is located at the central portion of the resistor member 1. The brush 7 is attached to the distal end of the movable arm 6, and slidably contacts with the inner circumferential surface of the resistor member 1. The movable arm 6 and the slip ring 8 located above the arm 6 are electrically connected to each other via the rotational shaft 4.
The above-mentioned contact type potentiometer is used by applying a DC voltage across the input terminals 3.3. When the brush 7 rotates and is displaced together with the rotational shaft 4, the voltage from the output terminal 10 changes. More specifically, the absolute value of the voltage dividing ratio of the DC voltage by the resistor member 1 is obtained in accordance with the position of the brush 7, and hence, the absolute value of the rotational angle or the displacement amount of the rotational shaft 4 can be detected.
This potentiometer is not influenced by a change in temperature, and can be used in an environment in a wide temperature range from -40.degree. C. to +150.degree. C. since it detects the position of the brush 7 using the voltage dividing ratio of the DC voltage in accordance with the resistance dividing ratio of the resistor member 1. However, detection precision is impaired due to wear of the resistor member 1 by the brush 7, and the service life of the potentiometer is shortened. In addition, a torque upon sliding is undesirably large.
In order to prolong the service life, a potentiometer including a non-contact detection portion is proposed. As shown in FIGS. 3 and 4, this potentiometer comprises a disk-shaped base 2 having a cylindrical wall 2a, and two magnetoresistive elements 11.11 are arranged on the base 2.
The two magnetic resistance elements 11.11 are designed to have a substantially semi-arcuated shape, and are arranged on the bottom portion of the base 2 to have a common center of curvature. These two magnetic resistance elements 11.11 are commonly connected to an output terminal 10 via a conductive wire. Input terminals 3.3 are respectively connected to the end portions of these elements 11.11 via conductive wires.
A rotational shaft 4 is pivotally inserted in the bottom portion of the base 2 via a bearing 5, and is located at the center of curvature of the two magnetic resistance elements 11.11. Furthermore, a permanent magnet 13 having a substantially semi-circular shape is attached as a magnetic field generating source to the circumferential surface of the rotational shaft 4, and opposes to the two magnetic resistance elements 11.11 via gaps. The permanent magnet 13 rotates in an facing state to the two magnetic resistance elements 11.11 via gaps upon rotation of the rotational shaft 4, thereby changing the amount of a magnetic field applied to the two magnetic resi

REFERENCES:
patent: 3671854 (1972-06-01), Masuda
patent: 3988710 (1976-10-01), Sidor et al.
patent: 4274074 (1981-06-01), Sakamoto
patent: 5231508 (1993-07-01), Murphy, Jr.

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