JPS5856100B2 - force transducer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a force measuring device that converts force corresponding to pressure, flow rate, buoyancy, etc. into an electrical signal using a strain detection element.

FIG. 1 is a configuration explanatory diagram showing an example of a conventionally known force transducer.

This device is constructed so that the pressure received by the sensing diaphragm 1 is transmitted to one end of a lever 3 via a transmission rod 2, and the lever 3 causes a flexible substrate 4 to flex.

Strain detection elements 5L52 are arranged at two locations on the flexible substrate 4 where strain acts with opposite polarities.

In conventional devices with such a configuration, the flexible substrate 4 is constructed from a single flat substrate in order to uniformly apply tension in one part and compression in other parts of the flexible substrate 4. However, there was a drawback that the configuration was complicated.

Here, an object of the present invention is to realize a force transducer with a simple configuration and high precision.

FIG. 2 is a structural explanatory diagram showing an example of a flexible substrate which forms the main part of the present invention, with A being a plan view thereof and B being a side view thereof.

This flexible board 4 has a 5-shape and is composed of a first plate 41 having one end fixed, and a second plate 42 having one end connected to the other end of the first plate. It's made of board.

411 and 412 are grooves provided perpendicularly to the longitudinal direction of the first plate 41, and are provided parallel to each other at a certain distance.

Two strain detection elements 51 and 52 are respectively arranged on the surface of the plate 41 on the opposite side from the grooves 411 and 412.

Thus, the load to be detected is applied perpendicularly to the second plate 42 at a point 421 approximately equidistant from the strain sensing elements 51, 52.

In the flexible board 4 having the above configuration, if a load P is applied to the location 421 in the direction of the arrow as shown in FIG. 2B, the bending moment diagram applied to the second board 42 is As shown in FIG. 3A, the first plate 41
The bending moment diagram applied to is shown in FIG. 3B.

That is, bending moments of approximately equal size and opposite signs (polarity) act on the portions of the first plate where the grooves 41L412 are provided.

Therefore, if the section modulus of the portion of the first plate 41 where the groove 41L412 is provided is made equal, the first plate 4
The strain that occurs on the surface opposite to the grooves 411 and 412 of No. 1 is
The signs are opposite and the magnitudes are almost equal.

Therefore, in this case, tensile strain occurs in the strain detection element 51, and compressive strain occurs in the strain detection element 52.

The electrical signals from these strain detection elements 5L52 are differentially detected by, for example, a bridge circuit or the like, and an electrical signal corresponding to the applied load can be obtained.

In general, for example, in a single cantilever beam 6 as shown in FIG. 4, a linear force P applied perpendicularly to the beam 6 causes deformation of the beam 6 and a θ angle deviation from the perpendicular to the beam 6.

In order to avoid errors caused by this and to ensure that the force always acts perpendicularly to the beam 6, it is possible to add a mechanism that converts it into a moment input, but the error of this mechanism is added, and in any case, The relationship between force and electrical output becomes nonlinear.

In the present invention, when the load P is applied to the second plate 42, since the plate thickness of the portion of the first plate 41 where the grooves 411 and 412 are provided is thinner, stress is applied to this portion. is concentrated, this portion expands and contracts, and the second plate 42 only moves in parallel in response to the load P, as shown in FIG. 2B.

As a result, the load conditions do not change as the load amount changes, and a linear relationship between force and electrical output can be obtained.

According to experiments by the inventor of this application, ±0.15% with a strain gauge attached to a 1800 micros drain
, linearity within ±0.03% was obtained with the vapor-deposited strain gauge.

Further, since it has a flat plate structure, machining during molding is easy, and in particular, since the grooves 411 and 412 are concave shapes that open outward, machining is easy.

Furthermore, the strain detection element can be easily attached and fixed during polishing of the surface.

Furthermore, in the device of the present invention, it has been experimentally confirmed that if the structural dimensions are appropriately selected, the influence of torsional strain will be less than a few percent to several percent of the principal strain, and can be almost ignored.

In addition, in the above-mentioned embodiment, the groove 411.4 is formed in the first plate 41.
12 are provided, but holes or the like may be provided in place of the grooves 411 and 412. In short, as long as the portion of the first plate 41 where the strain detecting element is attached is likely to cause a large strain, good.

Note that if there is no need to increase the sensitivity, the grooves 411 and 412
Of course, there is no need for the above.

Note that if the thin film strain sensing elements 51 and 52 are directly formed on the first plate 41 by vapor deposition or sputtering, (1) multiple strain sensing elements can be molded at the same time under the same conditions; , each resistance value or resistance temperature coefficient, etc.
You can obtain products with uniform characteristics.

(2) The bonding between the strain sensing element and the flexible substrate is an intermolecular bond, and no adhesive is required, so there is no creep phenomenon caused by adhesives, etc., and there is no decrease in sensitivity. There is no fear that the adhesive will be deformed or its adhesive function will deteriorate due to the influence of.

(3) Thin film strain sensing elements are extremely stable in physical properties and have high reliability in terms of characteristics such as aging.

(4) For pasting, the shape distortion detection element requires gluing work,
Thin-film strain sensing elements are manufactured directly onto a substrate using a device, and are excellent in mass production, and a large number of them can be manufactured in one line at the same time.

(5) Since leads for bridge circuit connection can be formed during thin film pattern formation, the number of bridge connection steps can be reduced.

(6) The zero-cooking correction resistor of the bridge circuit can also be created at the same time, or the resistance value of each distortion detection element can be corrected by trimming.

As explained above, according to the present invention, the flexible substrate is
It is possible to realize a highly accurate force transducer that has a simple structure and has various features such as those described below.

(1) When using vapor-deposited strain gauges as strain sensing elements, they can be manufactured simultaneously on the same surface.
Elements with uniform resistance values and temperature coefficients can be obtained.

(2) When configuring a full bridge circuit by detecting elongational strain and compressive strain at two locations each, the detection locations for the same type of strain are collected at one location each, and variations in the thickness of the flexible substrate, variations in vapor deposition, etc. There is little influence from

(3) A linear Kerr distortion characteristic can be obtained.

(4) Linear force can be directly converted as it is.

(5) Since it has a flat structure, molding is easy.

[Brief explanation of the drawing]

FIG. 1 is a configuration explanatory diagram showing an example of a conventionally known force transducer;
FIG. 2 is a configuration explanatory diagram showing an example of a flexible base and plate that constitute the main part of the present invention, where A is a plan view, B is a side view, and FIG.
B is a bending moment diagram of the flexible substrate shown in FIG. 2, and FIG. 4 is an explanatory diagram for explaining the present invention. 4...Flexible board, 41...First plate, 411°412...Groove, 42...Second plate, 51.52... ...Distortion detection element.

Claims (1)

[Claims] 1. A first plate having one end fixed, and a second plate having one end connected to the other end of the first plate and provided parallel to one side of the first plate. A flat flexible substrate, comprising at least two strain detection elements provided at a required distance on one surface of the first plate, such that a point of zero bending moment is generated between the strain detection elements. A force transducer adapted to apply a load to be converted to said second plate. 2. The force transducer according to claim 1, wherein the portion of the flexible substrate where the strain detection element is provided is a flexible portion, and stress is concentrated on the flexible portion. 3. The force transducer according to claim 2, wherein a groove or a hole is formed in the flexible substrate as the flexible portion. 4. As a strain detection element, an insulating layer formed on the surface of the flexible substrate, a resistance pattern layer formed on the insulating layer,
The force transducer according to claim 1, 2, or 3, comprising an electrode layer formed on a portion of the resistive pattern layer.