JPH0450969B2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a strain-generating element that converts force into strain;
In particular, the present invention relates to a strain-generating element having two opposing fixed walls that are symmetrical about an axis.

Conventional technology Typical conventional strain-generating elements used in force transducers, etc. have a structure in which force is applied to the free end of a cantilever beam with one end fixed, and the force applied to the free end is A corresponding deflection or strain is configured to occur in the flexible portion of the cantilever. In the case of a force transducer, a strain sensing element made of a metal wire or a semiconductor is attached to the flexible part of a cantilever that constitutes a strain generating element, and the said bending is detected as an electrical quantity by the strain sensing element. ,
Force is converted into electricity.

In this type of conventional strain-generating element, when the force to be detected is applied, bending stress acts on all members involved in supporting the fixed end of the cantilever, resulting in a slight displacement at the fixed end. The purpose of the cantilever beam is to make the material of the cantilever beam durable enough to withstand the applied force. If metal is used, there will be a difference in thermal expansion between the material of the cantilever beam and the material of the strain sensing element, which will cause distortion due to the temperature difference between the cantilever beam and the strain sensing element, causing conversion errors. However, in order to fix the cantilever beam and the strain detection element, which have different thermal expansion, an organic adhesive is required, and the adhesive further causes conversion errors.

Problems to be solved by the invention Therefore, the problems to be solved by the invention are as follows:
These are errors caused by the displacement of the fixed end of a strain-generating element with a conventional cantilever structure, and conversion errors due to the difference in materials between the cantilever and the strain detection element, which is due to the strength required for the cantilever structure. .

Means for Solving the Problems In order to solve the above problems, according to the present invention,
Strain detection elements 7A and 7B made of semiconductor material (see Figure 1)
In the strain element to which the strain sensing element is attached, a pair of opposing side walls 2 of a rectangular plate 1 made of the same semiconductor material as that of the strain sensing element are used as fixed walls, and a pair of U-shaped parts having parallel legs parallel to the fixed walls 2 are used. A window 4 is bored in the square plate 1 symmetrically with respect to the central axis A parallel to the fixed wall 2 of the square plate 1, and the square plate 1 is perpendicular to the fixed wall 2.
Using a configuration in which the side wall of the window serves as the action surface 6, opposite strains are generated in the pair of legs of the U-shaped window 4 in response to a force F applied near the central axis A of the action surface 6 in the direction of the axis A. let

Function In the rectangular plate 1 having the above structure, the leg joint wall 4B between both legs 4A of each U-shaped window 4 and the tip wall 4C of the leg 4A are thin parts parallel to the working surface 6.
Therefore, when a force F is applied to the working surface 6, these thin-walled parts are deformed with a strain as shown by the dotted line in FIG. 2, and the working surface 6 is displaced parallel to , the protrusion 5 between the legs 4A is also shown in a greatly exaggerated manner with dotted lines on the nearer fixed wall 2.
tilt to the side. Therefore, the rectangular plate 1 of the above structure fixed by both fixed walls 2, 2 is a strain-generating element that generates a strain as shown in a greatly exaggerated dotted line in FIG. 2 in response to the applied force F. It acts as.

Embodiment To explain the illustrated embodiment of the invention, the rectangular plate 1 is made of a semiconductor, preferably carved from a single crystal semiconductor. A pair of opposing side walls of the square plate 1 are appropriately fixed to holding members 3, 3 as fixed walls 2, 2. Therefore, the square plate 1 is supported symmetrically with respect to the central axis A at the center between the fixed walls 2, 2. In this respect, the present invention is fundamentally different from conventional cantilever structures.

A pair of U-shaped windows 4 are formed at symmetrical positions on the square plate 1 with respect to the central axis A so that their parallel legs 4A are parallel to the fixed wall 2. Although each U-shaped window 4 in the illustrated example is inverted, the U-shaped window 4 may be erect or inverted as long as the parallel legs 4A are parallel to the fixed wall 2. Between both parallel legs 4A, a projection 5 projects parallel to the fixed wall 2 into the U-shaped window 4.

The side walls of the square plate 1 which are perpendicular to the fixed walls 2, 2 are used as working surfaces 6. In the illustrated example, the force F is applied to the lower working surface 6, but the force F is applied to the upper working surface 6.
May be added to.

Preferably, strain detection elements 7A, 7 made of semiconductor single crystal are provided between the protrusion 5 and the opposing wall of the U-shaped window 4.
B is fixed by adhesion or the like without using an organic adhesive. More preferably, the semiconductor strain detection element 7A,
The material of 7B is made the same as that of the square plate 1, and glass is used as the adhesive. The semiconductor strain detection elements 7A and 7B are elements whose resistance value changes depending on the strain, and are connected to, for example, a bridge circuit (not shown) to generate an output electrical signal proportional to the strain.

The reason why the rectangular plate 1 of the present invention is made of a semiconductor is to prevent distortion caused by temperature changes from occurring in the strain detection element when a semiconductor strain detection element is incorporated therein. 1
The pair of U-shaped windows 4 are formed as a pair by providing them symmetrically with respect to the central axis A of the leg joint wall 4B of the window 4 in FIG. 1, that is, the thin wall portion, as shown by the dotted line in FIG. This is to generate a symmetrical strain with respect to the central axis A so that the force F is applied equally to both fixed walls 2, 2. The equal burden of the applied force F by the opposing fixed walls 2, 2 reduces the load on the fixed walls 2, 2 to approximately half of that in the case of a cantilever beam, so the square plate 1
This increases the degree of freedom in selecting the material, prevents undesired distortion in the vicinity of the walls 2, 2, and also allows the holding member 3 to be simplified and downsized. In addition,
For simplicity, it is also possible to make the shape of the window on which the element is not fixed to be a simple rectangle.

To explain the operation, when a force F is applied to the action surface 6, the leg joint wall 4B and the leg tip wall 4C are deformed, and the protrusion 5 The tip of the wall is inclined toward the fixed wall 2 that is closer to it.

Referring to FIG. 2, let θ be the angular displacement of the leg joint wall 4B and the leg tip wall 4C, let the length of the leg joint wall 4B be, and let the leg joint for a given force F of a specific magnitude. If the maximum displacement of the part wall 4B and the leg tip wall 4C is δ ₁ , the maximum displacement corresponding to δ ₁ of the protrusion 5 is δ ₂ , and the height of the protrusion 5 is h, the following approximate formula holds true. .

δ ₁ ≒lθ δ ₂ ≒hθ When the strain detection elements 7A and 7B are provided as shown in FIG. 1, the strain in FIG. 2 gives compressive strain to one strain detection element 7A, and Since tensile strain is applied to the strain detection element 7B, the force F can be detected in a so-called push-pull manner, allowing highly sensitive and highly accurate force detection.

Effects of the Invention As explained above, the strain-generating element that converts force into strain according to the present invention has two fixed walls and two
Since it has two U-shaped windows, it has the following remarkable effects.

(a) Since the acting surface is substantially moved in parallel, even if the point of application of the force F is slightly shifted from the central axis A, there is no effect.

(b) Since no bending stress acts on the members that support the fixed walls, each fixed wall can be supported by a relatively simple holding member and the size can be reduced without sacrificing accuracy.

(c) It is possible to use a semiconductor strain sensing element having a coefficient of thermal expansion equal to that of the rectangular plate, and it is possible to prevent temperature errors due to the difference in coefficient of thermal expansion between the two.

(d) Both the strain element and the semiconductor strain detection element are made of materials that can withstand high temperatures, making it possible to bond them to glass, thereby making it possible to prevent temperature errors, creep errors, etc. caused by organic adhesives.

(E) A measurement system can be constructed in which the member supporting the fixed wall 2 and the member applying the force F are arranged coaxially.

[Brief explanation of drawings]

FIG. 1 is a schematic perspective view of one embodiment of the strain element according to the present invention, and FIG. 2 is an explanatory diagram of its operation. DESCRIPTION OF SYMBOLS 1... Square plate, 2... Fixed wall, 3... Holding member, 4... U-shaped window, 4A... Parallel leg part, 5... Protrusion, 6... Working surface, 7A, 7B... Strain detection element ,
A...Central axis line, F...force.

Claims (1)

[Claims] 1. In a strain element to which a strain detection element made of a semiconductor material is attached, a pair of opposing side walls of a rectangular plate made of the same semiconductor material as the semiconductor material of the strain detection element are used as fixed walls, and parallel legs parallel to the fixed walls are provided. drilling a pair of U-shaped windows in the square plate symmetrically with respect to a central axis parallel to the fixed wall of the square plate;
A side wall of the rectangular plate perpendicular to the fixed wall is used as a working surface, and the pair of legs of the U-shaped window are caused to produce opposite strains in response to a force applied in the axial direction near the central axis of the working surface. A strain element that converts force into strain.