JPS60262402A - Variable resistance unit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Field of application of the invention] The present invention relates to a variable resistance device, i.e. a potentiometer device (=
related.

[Background of the invention]

Applicant's pending UK Patent Application No. 8312279
No. (J, C, Greenwatt 56) relates to a transducer C2 for detecting relative rotational interlocking between first and second bodies, the sensor member of this transducer comprising:
It consists of flexible thin sheets of monocrystalline piezoresistive material arranged in two widths so that they can be bent by rotational motion.

[Problem of invention]

The applicant has now discovered that a similar structure can be employed in the manufacture of variable resistance devices or potentiometer devices. It is an object of the present invention to do so.

[Summary of the invention]

According to one aspect of the invention, a variable resistance or potentiometer is provided which includes a flexible piezoresistive element and a device for applying a bending force C2 to the element and thereby determining the electrical resistance of the element.

According to another feature of the invention, there is provided a flexible piezoresistive element mounted on the support beam 1, said element ζ a movable cam having an abutting first cam surface and a movable cam surface having an abutting second cam surface. a support beam having a structure and means for moving said cam structure, a variable resistor or potentiometer arranged so that said element can be bent by a distance corresponding to the relative relationship of the shapes of the cams; provided.

Although this device is of general use, it is particularly used in, for example, chart recorders, X-Y plotters, and differential pressure recorders, which require high accuracy and reliability.

〔Example〕

Embodiments of the present invention will be described below with reference to the accompanying drawings.
C2 in the only figure shows a schematic diagram of the present variable resistance device. For clarity, the housing within which the device is mounted is not shown.

Referring to the drawings, the device has a double cam structure 011 integrally molded from plastic material, which structure is a shirt).
The cam assembly 011 has an operating or copying cam α1 with an outer surface shape 1' which produces the desired electrical resistance characteristics, and a semi-circular reference cam α◆. Each cam is in contact with a corresponding cam follower (]Fj, (16).

The sensor element of the device has a flexible thin hvt of monocrystalline silicon attached via an integral mounting part α8 to the movable support beam α. The movement of the beam 0I is caused by a relatively thin flexible hinge part (2). Usually both cam followers (15, CI@ and the beam α) are molded from plastic material. Advantageously, the beam a
The tightening element 025 is the cam follower QO and the α spring (
to) and) are abutted by C2.

The sensor element αη is doped, for example with boron, to form one or more piezoresistive regions Q]J. Normally, element damage is rejected by a Wheatstone bridge resistor circuit, and each resistance value is set so that the bridge is balanced in the undistorted state of the element 0η.

Connection to the resistance circuit (c) is made by a conductor (c) attached to the support beam α9.

When the cam structure α is rotated, the element is bent through the abutting cam follower α, and the resistance value changes by usually up to 20%, resulting in a corresponding unbalance of the bridge. This unbalance signal is transmitted to an amplifier (not shown). The output signal may be amplified by 2 to produce an output signal corresponding to the rotational position 62 of the cam structure.

Preferably, the cam a4 has a contour shape such that a bilinear relationship occurs between the angular displacement of the cam and the resistance value of the element q force. This contour shape is determined by calculations based on the strain-resistance characteristics of the specific element used.

The transducer element a.eta. is made from single crystal silicon by masking and etching from a silicon substrate. Normally, Ueno is processed to form a resistor Qη, and then its front and back surfaces are masked. The front mask defines the boundaries between elements 69, and the back mask defines the mounting portions of each element.

The wafer is etched first from the six double sides to define the flexible portion of each element and then from the surface to separate each element. It has been found that conventional etching produces very uniform cuts that maintain the thickness of the flexible portion of the device to within 1 micron.

The last 6 two connecting leads (A) are connected to the resistor circuit (2) by e.g. nail head bonding (2), and then the element is connected to the support beam (A) by the mounting part <lFG.
(Two installed.

Compensation for the eccentricity of the cam structure is performed by a cam follower αQ and a reference cam α that are in contact with the support beam C11l.

When the cam assembly Qll is rotated, the curvature of the sensor c1η corresponds to the difference in radius of the two cams (2), so that the approximately two-circular cam controls the reference beam. This automatically compensates for non-coaxiality or eccentricity of the cam assembly. bring about.

Although the above description is redundant for circular cams, it goes without saying that other cam structures may also be used, such as circular surface or linear cams.

[Brief explanation of drawings]

The drawing is a perspective view schematically showing a variable resistance device according to an embodiment of the present invention. In the figure, 11 is a movable cam structure, 16 is a first cam surface, 14 is a second cam surface, is, 16 is a cam follower, 17 is a flexible piezoresistive element, 19 is a support beam, and 22.23 is a pressurized spring. shows. Agent Patent Attorney Masatoshi Sato

Claims (6)

[Claims] (1) A variable resistance device comprising a flexible piezoresistance element and a member that applies two bending forces to determine the electrical resistance of the element. (2) a movable cam structure having a flexible piezoresistive element mounted on the support beam (2), a first cam surface abutting the element and a second cam surface abutting the support beam; A variable resistance device having a relative shape of the cam relative to C2 (=means for moving said force ram assembly so that it is bent by a corresponding distance). (3) The device according to claim 2, wherein a cam follower is provided in contact with each of the cams 12, respectively. (4) The device according to claim 2 (1) or (6) (2), wherein the cam structure is an integral part made of plastic material. (5) The first cam surface is contoured to create a bilinear relationship between the angular displacement of the cam and the resistance of the element. Any one of the devices described in C. (6) The device according to any one of claims 2 to 5, wherein the support beam and the flexible element are pressurized by respective cams (two springs).