JPS5856099B2 - force transducer - Google Patents

Description

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

FIG. 1 is a diagram illustrating the configuration of 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 bends a flexible substrate 4.

Strain detection elements 51 and 52 are arranged on the flexible substrate 4 at two locations where strain acts with opposite polarities.

In conventional devices with such a configuration, the flexible substrate 4 is constructed of 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, the present invention aims to realize a force transducer with a simple structure 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 U-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 is made from a single board.

Then, a load to be detected is applied to the tip 421 of the second plate 42.

43 and 44 are grooves provided near the joint between the first plate 41 and the second plate 42.

The strain detection elements 51 and 52 are arranged on the surface of the flexible substrate 4 at the location opposite to the grooves 43 and 44 where the grooves 43 and 44 are provided.

In the flexible substrate 4 having such a configuration, now FIG.
If a load P is applied to the tip 421 of the second plate 42 in the direction of the arrow as shown in FIG. A diagram of the bending moment applied to the second plate 42 is shown in FIG. 3B.

That is, the bending moment occurring near the joint between the first plate 41 and the second plate 42 has the same magnitude and has the sign (
polarity) are opposite.

Therefore, if the section modulus of the first plate 41 and the second plate 42 are made equal, the strain generated on the surface of one side of the first plate 41 and the second plate 42 will have the opposite sign and be large. The results will be the same.

Therefore, in this case, compressive strain occurs in the strain detection element 51 provided on the surface of the first plate 41, and tensile strain occurs in the strain detection element 52 provided on the second plate 42.

The electrical signals from these distortion detection elements 51 and 52 are differentially detected by, for example, a bridge circuit, and are applied to the first plate 4.
It is possible to obtain an electrical signal corresponding to the load applied to the tip 421 of No. 2.

Note that the flexible substrate 4 may have a symmetrical structure as shown in FIGS. 4A and 4B.

At first glance, it seems that the structure has good stability (balance) against loading forces.

However, if the structure is made symmetrical, the structure becomes more complicated and the number of processing steps increases.

Furthermore, in FIG. 4A, the load points are divided into two locations, so a transmission mechanism is required to equally transmit the load to the two load points.

In FIG. 4B, there is only one loading point, but a pair of strain detection elements 51 detecting the same type of strain as in FIG. 4A.
Otherwise, the arrangement positions of the strain gauges 52 are dispersed on both sides, and in particular, when a vapor deposition strain gauge is used as a strain detection element, the effects of variations during vapor deposition are likely to occur.

Furthermore, in the device of the present invention, it has been experimentally confirmed that if the structural dimensions are appropriately selected, the effect of torsional strain will be less than 10% to several % compared to the principal strain, and can be almost ignored.

Next, as shown in FIGS. 5A and 5B, in the device of the present invention and the one having a symmetrical structure, strain detection is carried out so that transverse strain in a direction perpendicular to the principal strain direction can be detected on the first plate, one end of which is fixed. Comparisons were made with each element 53 attached, and in this case as well, it was experimentally confirmed that the strain of the symmetrical structure was about 6.5 times that of the device of the present invention.

In addition, in the above-mentioned embodiment, the first plate 41 and the second plate 42
Although the grooves 43t and 446' are provided, holes etc. may be provided instead of the grooves 43 and 44. In short, the distortion detection elements 51 and 52 of the first plate 41 and the second plate 42 are provided. Any material that causes a large amount of distortion may be used.

Note that, of course, the grooves 43, 44, etc. may be omitted if there is no need to increase the sensitivity.

Note that if the thin film strain sensing elements 51 and 52 are formed directly on the flexible substrate 4 by vapor deposition or sputtering, (1) multiple strain sensing elements can be molded at the same time under the same conditions; 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 equipment, and are excellent in mass production, allowing many to be manufactured at the same time under the same conditions.

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

(6) It is also possible to prepare the electric adjustment correction resistor of the bridge circuit at the same time, or to correct it by trimming the resistance value of each distortion detection element.

As explained above, according to the present invention, since the flexible substrate can be constructed from a single flat plate, a highly accurate force transducer having a simple construction and the following various features can be realized.

(1) When using vapor-deposited strain gauges as strain sensing elements, they can be manufactured simultaneously on the same surface, so 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) The fixed end and load end of the flexible board can be brought close to each other, and the bending moment acting on the fixed end can be reduced.

Theoretically, it can be set to zero, and the fixation is stable.

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

(For example, with a span of 2,500 microstrains, the error is within ±0.2% of the full scale. However, the attachment depends on the gauge.

Includes all creep errors, hysteresis errors, etc.

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

[Brief explanation of drawings]

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 substrate that forms the main part of the present invention, where A is a plan view, B is a side view, and FIGS. 3A and B.
are the bending moment diagrams of the flexible board in Figure 2, 4th and 5th
The figure is an explanatory diagram for explaining the present invention. 4... Flexible board, 41... First plate, 42... Second plate, 43, 44...
Groove, 51, 52... Strain detection element.

Claims (1)

[Claims] 1. A flexible substrate comprising a first plate and a second plate whose one end is connected to one end of the first plate parallel to one side of the first plate;
At least two or more strain detection elements are provided on a surface of one common side of the first plate and the second plate, each disposed near where the first plate and the second plate join. , a force transducer configured to apply a force to be converted to the other end of the first plate or the 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.