JPS5856424B2 - 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 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 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 polarity.

In conventional devices with such a configuration, the flexible substrate 4 is made of a single flat substrate in order to uniformly generate tension in one part and compression in other parts. It has the disadvantage that it cannot be configured easily and the store structure is complicated.

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

FIGS. 2A and 2B are structural explanatory diagrams showing an example of a flexible substrate forming the main part of the present invention, where A is a perspective view and B is a side view.

This flexible substrate 4 has a comb-tooth 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 of one board.

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

411 and 412 are grooves provided in the first plate 41 at a required distance.

The strain detection elements 51 and 52 are located in the grooves 411° 41 of the flexible substrate 4.
2 is disposed on the surface opposite to the grooves 411 and 412 where grooves 411 and 412 are provided.

In the flexible substrate 4 having such a configuration, now FIG.
As shown in FIG. 3A, if a load P is applied to the tip 421 of the second plate 42 in the direction of the arrow, the bending moment diagram acting on the second plate 42 will be as shown in FIG. , the bending moment diagram applied to the first plate 41 is shown in Fig. 3B.
It becomes as shown in .

That is, bending moments of approximately equal size and opposite signs (polarity) act on the locations where the first plate grooves 411 and 4120 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 51 and 52 are differentially detected by, for example, a bridge circuit, 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 ensure that the force always acts perpendicularly to the beam 6 in order to avoid errors caused by this, it is recommended to add a mechanism to convert it into moment force, or in any case, the error of this mechanism will be added. The relationship between force and electrical output tends to be nonlinear.

In the present invention, when the load P is applied to the second plate 42, since the plate thickness of the part of the first plate 41 where the grooves 411 and 412 are provided is thinner, stress is applied to this part. 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.

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.

Moreover, since the load P is applied equally to the second plate 42 provided on both the first plates 410 and I11, no torsional strain occurs in the first plate 41.

Therefore, there is no possibility that torsional strain will be detected by the strain detection elements 51 and 52.

FIG. 5 is a configuration explanatory diagram of a specific example of the present invention.

In this example, the air pressure input Q is received by the Perot 1' and applied as a force P to the tip end portion 421 of each second plate 42 via the U-shaped transmission plate 7.

In the above-mentioned embodiment, the load P and the groove 411.
Although it has been described that the strain is applied to the second plate 420 at 420 locations where a strain having the opposite sign and the same magnitude occurs in the strain detecting element 51.5, the present invention is not limited to this.
It is only necessary that the load P be applied to a position of the second plate 42 where a bending moment of zero occurs between the two.

In addition, in the embodiment described above, the groove 411.4 is provided in the first plate 41.
12 are provided, but holes or the like may be provided instead 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.

In addition, if there is no need to increase the sensitivity, use grooves 411 and 412.
(But of course it's a good word.

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, then (1) a plurality of strain sensing elements can be molded simultaneously under the same conditions; By doing this, it is possible to obtain products with uniform characteristics such as respective resistance values or temperature coefficients of resistance.

(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.

0) For attachment, shape strain detection elements require adhesive work, but thin film strain detection elements are manufactured directly onto the substrate using equipment, making them excellent for mass production and allowing for the manufacture of many devices at the same time under the same conditions. I can do it.

(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-adjustment correction resistance 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.

Note that the thin film strain sensing elements 51 and 52 can be made, for example, as follows.

(i) Polish the surface of the flexible substrate 40 to make it sufficiently flat.

(11) An inorganic insulating material, such as SiO, is deposited on a flat surface to a thickness of about several microns to form an insulating layer on the surface of the flexible body.

(iii) A resistive material such as Ni-Cr or Pt is deposited to an appropriate thickness on the insulating layer, and then a desired resistive pattern layer is formed by etching or other techniques.

4v) Add a few μm of electrode material, such as Au, to a part of the resistance layer.
The electrode layer is formed by vapor deposition to a certain thickness.

(V) Connect a lead wire, for example, a gold wire, to the electrode layer.

(Vi) An inorganic insulating material is deposited on the resistance layer and the electrode layer to a thickness of about several μm or less to form a protective film.

Note that this protective film may be omitted.

As explained above, according to the present invention, the flexible substrate can be composed of one flat plate, and the structure is simple, and
It has various features such as:

A highly accurate force transducer can be realized.

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

(2) When constructing a full-fridge 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, which is affected by variations in the thickness of the flexible substrate, variations in vapor deposition, etc. There are few

(3) Obtain a linear Kerr distortion characteristic.

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

(5) Since it has a flat plate structure, it is easy to mold it.

(6) Since it has a symmetrical structure, it is stable and there is no risk of detecting torsional distortion.

[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 board that forms the main part of the present invention, in which A is a perspective view, B is a top view, and FIG.
B is a bending moment diagram of the flexible substrate shown in FIG. 2, FIG. 4 is an explanatory diagram for explaining the present invention, and FIG. 5 is an explanatory diagram of a configuration of a specific example of the present invention. 4... Flexible board, 41... First plate, 411°4
12...Groove, 42...Second plate, 51.52...
Strain 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 both sides of the first plate. A flat flexible substrate, comprising at least two strain detection elements vertically provided at a required distance on one surface of the first plate, and a point where zero bending moment occurs between the strain detection elements. a force transducer adapted to apply a force to be transduced to each of said second plates so as to cause a force to be transduced; 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.