JP7159073B2 - load cell - Google Patents

Description

Embodiments of the present invention relate to load cells capable of detecting force and torque.

A load cell is composed of, for example, a strain body that receives a force, a strain gauge as a strain sensor provided on the strain body, and a structure to which the strain body is fastened (see Patent Document 1, for example).

JP 2017-172983 A

The strain-generating body is fixed to the structure using, for example, bolts. However, with the miniaturization of the load cell, it has become difficult to fix the strain-generating body to the structure with bolts, and it has become difficult to hold the position of the strain-generating body with respect to the structure with high accuracy.

If the strain-generating body is not fixed to the structure with high precision, the gauge factor, which is the ratio of the strain to the change in electrical resistance, becomes small in the strain gauge, making it difficult to accurately detect, for example, a weak force. There are problems such as

This embodiment provides a load cell capable of fixing the strain generating body to the main body with high accuracy.

A load cell according to an embodiment includes a tubular first member having a first flange on the inside, a second member arranged concentrically with the first member and having a second flange on the outside, and a tubular second member. 1 structure, a tubular second structure provided inside the first structure, and an elastic third structure provided between the first structure and the second structure. a first strain body having the first member attached to the outside of the first structure and the second member attached to the inside of the second structure; At least one second brace provided between a first structure and said first collar, a second end provided between said second structure and said second collar, and having a strain sensor. and a strain body.

FIG. 2 is a top view showing the load cell according to the first embodiment; FIG. 2 is an exploded perspective view of FIG. 1 ; Sectional drawing along the III-III line of FIG. The figure which shows an example of the strain sensor applied to 1st Embodiment. Sectional drawing which shows the load cell which concerns on 2nd Embodiment.

Embodiments will be described below with reference to the drawings. In the drawings, the same parts are given the same reference numerals.

(First embodiment)
1 to 4 show a load cell according to a first embodiment. The load cell 10 comprises a first member 11, a second member 12, a first strain body 13, for example two second strain bodies 14, 15, a first elastic body 16 and a second elastic body 17. .

The first member 11, the second member 12, the first strain body 13, and the second strain bodies 14 and 15 are made of stainless steel (SUS), for example. However, the material is not limited to SUS, and other metal materials such as iron and aluminum can also be used.

The first member 11 is cylindrical and has a first collar portion 11a inside.
The second member 12 has a smaller diameter than the first member 11 and is arranged concentrically therewith. The second member 12 has a second collar portion 12a on the outside.

The first strain-generating body 13 includes a tubular first structure 13a, a tubular second structure 13b provided inside the first structure 13a, and the first structure 13a and the second structure 13b. and a third structure 13c provided between and connecting them. The third structure 13c has elasticity. Therefore, the second structure 13b can move in the axial direction (direction of arrow A shown in FIG. 3) with respect to the first structure 13a.

Also, the thickness of the third structure 13c is thicker than the thickness of the second strain-generating bodies 14 and 15 . Therefore, the range of force detectable by the load cell (rated load) and withstand load (allowable load) depend on the length of the third structure 13c (the distance between the first structure 13a and the second structure 13b). ) and can be adjusted by changing the thickness.

The first member 11 is attached to the outside of the first structure 13 a of the first strain body 13 . Specifically, the inner diameter of the first member 11 is slightly smaller than the outer diameter of the first structure 13a, and the first member 11 is press-fitted to the outside of the first structure 13a.

Also, the second member 12 is mounted inside the second structure 13 b of the first strain generating body 13 . Specifically, the outer diameter of the second member 12 is slightly larger than the inner diameter of the second structure 13b, and the second member 12 is press-fitted inside the second structure 13b.

As shown in FIG. 2, a plurality of notches 13d are provided in portions of the first structural body 13a and the second structural body 13b located in the diametrical direction of the first strain generating body 13. As shown in FIG. These cutouts 13d are used for positioning the two second strain-generating bodies 14 and 15. As shown in FIG. Therefore, the width of these cutouts 13d is substantially equal to the width of the second strain-generating bodies 14 and 15, and the depth thereof is slightly shallower than the thickness of the second strain-generating bodies 14 and 15. As shown in FIG.

The first elastic body 16 is, for example, a ring-shaped disc spring, and is provided inside the first member 11 along the first collar portion 11a. The outer diameter of the first elastic body 16 is substantially equal to the inner diameter of the first member 11, and the inner diameter of the first elastic body 16 is set to a size that allows contact with the first ends of the second strain-generating bodies 14 and 15. ing.

The second elastic body 17 is, for example, a ring-shaped disc spring, and is provided outside the second member 12 along the second collar portion 12a. The inner diameter of the second elastic body 17 is substantially equal to the outer diameter of the second member 12 , and the outer diameter of the second elastic body 17 is large enough to contact the second ends of the second strain-generating bodies 14 and 15 . It is

At the time of assembly, first, for example, the first ends of the second strain-generating bodies 14 and 15 are inserted into the plurality of notches 13d of the first structure 13a, and the second strain-generating bodies 14 and 15 are inserted into the plurality of notches 13d of the second structure 13b. The second ends of the two strain bodies 14, 15 are inserted.

After that, for example, the first elastic body 16 is mounted inside the first member 11 , and the first member 11 is mounted outside the first structural body 13 a of the first strain body 13 . From this state, the first elastic body 16 contacts the first ends of the second strain-generating bodies 14 and 15, and the first member 11 is press-fitted to the outside of the first structural body 13a until a predetermined contact pressure is achieved. be. For this reason, as shown in FIG. It is fixed to the first structure 13 a by the body 16 .

Also, the second elastic body 17 is attached to the outside of the second member 12 , and the second member 12 is attached to the inside of the second structural body 13 b of the first strain-generating body 13 . From this state, the second member 12 is press-fitted inside the second structure 13b until the second elastic body 17 abuts on the second ends of the second strain-generating bodies 14 and 15 and a predetermined contact pressure is achieved. be. For this reason, as shown in FIG. It is fixed by the body 17 to the second structure 13b.

As described above, the depth of the notch 13d is slightly shallower than the thickness of the second strain-generating bodies 14 and 15. As shown in FIG. Therefore, when the first strain-generating bodies 14 and 15 are inserted into the notch 13d, the upper surfaces of the second strain-generating bodies 14 and 15 protrude slightly from the notch 13d. Therefore, the first elastic body 16 and the second elastic body 17 are in contact with the upper surfaces of the second strain-generating bodies 14 and 15, and the second strain-generating bodies 14 and 15 are connected to the first structure 13a and the second structure 13b. can be fixed securely.

In the above configuration, when the second member 12 receives a force in the direction of arrow A shown in FIG. to move in the direction of arrow A. Accordingly, the second strain generating bodies 14 and 15 are deformed in their thickness direction (direction of arrow A).

That is, the thickness of the second strain-generating bodies 14 and 15 is thinner than the thickness of the third structure 13c. Therefore, when the first structural body 13a and the second structural body 13b move relative to each other, the second strain generating bodies 14 and 15 are interlocked and deformed.

FIG. 4 shows an example of strain sensors (strain gauges) provided on the second strain generating bodies 14 and 15. As shown in FIG. The second strain-generating body 14 is provided with, for example, thin-film resistors R1 and R2 as strain sensors, and the second strain-generating body 15 is provided with, for example, thin-film resistors R3 and R4 as strain sensors.

The thin-film resistors R1, R2 and the thin-film resistors R3, R4 are arranged on the second end side of the second strain-generating bodies 14, 15, that is, near the second structure 13b. The reason for this is that when the second structure 13b of the first strain-generating body 13 moves in the direction of arrow A in the figure with respect to the first structure 13a, the strain generated in the second strain-generating bodies 14 and 15 is the second This is because the structure 13b side is larger than the first structure 13a.

The thin-film resistors R1, R2, R3, and R4 constitute, for example, a bridge circuit, and output forces applied to the second strain-generating bodies 14 and 15 as electric signals.

For example, by providing a plurality of openings in the third structure 13c, it is also possible to move the second structure 13b around the axis (in the direction of arrow B shown in FIG. 3) with respect to the first structure 13a. is. In this case, the load cell 10 makes it possible to study the torque.

(Effect of the first embodiment)
According to the first embodiment, the second elastic bodies 14 and 15 are the first elastic body 16 mounted inside the first member 11 and the second elastic body mounted outside the second member 12. 17, the first strain body 13 is fixed to the first structure 13a and the second structure 13b. Therefore, even when the shape of the load cell 10 is reduced, the second strain-generating bodies 14 and 15 can be reliably fixed to the first structure 13a and the second structure 13b of the first strain-generating body 13. .

Moreover, since the second strain-generating bodies 14 and 15 are fixed using the first elastic bodies 16 and the second elastic bodies 17, the second strain-generating bodies 14 and 15 are fixed using bolts, for example. Therefore, the space can be reduced, and the shape of the load cell 10 can be made smaller.

Further, the second strain-generating bodies 14 and 15 press-fit the first member 11 to which the first elastic body 16 is attached to the outside of the first structural body 13a of the first strain-generating body 13, and the second elastic body 17 is The assembled second member 12 can be assembled only by press-fitting the attached second member 12 inside the second structural body 13b of the first strain-generating body 13 . Therefore, assembly is easy, and manufacturing costs can be reduced.

(Second embodiment)
FIG. 5 shows a second embodiment. In the first embodiment, the second strain generating bodies 14 and 15 are fixed using disc springs as the first elastic body 16 and the second elastic body 17 . On the other hand, in the second embodiment, the first brim portion 11b and the second brim portion 12b are elastic bodies, and the first brim portion 11b and the second brim portion 12b themselves provide the second strain body 14, 15 is fixed.

Specifically, as shown in FIG. 5, the first flange portion 11b of the first member 11 is inclined toward the press-fitting direction of the first member 11, and the second flange portion 12b of the second member 12 It is inclined toward the press-fitting direction of the first member 11 . That is, the tip of the first collar portion 11 b is inclined so as to approach the first structure 13 a of the first strain body 13 , and the tip of the second collar portion 12 b is tilted toward the first structure 13 a of the first strain body 13 . 2 is tilted to approach the structure 13b. Therefore, the first brim portion 11b and the second brim portion 12b have elasticity.

At the time of assembly, first, for example, the first ends of the second strain-generating bodies 14 and 15 are inserted into the plurality of notches 13d of the first structure 13a, and the second strain-generating bodies 14 and 15 are inserted into the plurality of notches 13d of the second structure 13b. The second ends of the two strain bodies 14, 15 are inserted.

After that, the first member 11 is attached to the outside of the first structural body 13a of the first strain body 13, and the first flange portion 11b abuts on the first end portions of the second strain bodies 14 and 15, causing a predetermined The first member 11 is press-fitted into the first structure 13a until a contact pressure of . Therefore, as shown in FIG. 5, the first ends of the second strain generating bodies 14 and 15 are fixed to the first structural body 13a by the first collar portion 11b of the first member 11. As shown in FIG.

The second member 12 is mounted inside the second structure 13b of the first strain body 13, and the second collar portion 12b abuts on the second ends of the second strain bodies 14 and 15 to provide a predetermined The second member 12 is press-fitted into the second structure 13b until a contact pressure of . Therefore, as shown in FIG. 5, the second end portions of the second strain generating bodies 14 and 15 are fixed to the second structural body 13b by the second collar portion 12b of the second member 12. As shown in FIG.

(Effect of Second Embodiment)
Effects similar to those of the first embodiment can also be obtained by the second embodiment. Moreover, according to the second embodiment, the second strain-generating bodies 14 and 15 are configured by the elastic first brim portion 11b and the second brim portion 12b. It can be fixed to the second structure 13b. Therefore, the number of parts can be reduced as compared with the first embodiment, and the assembly can be further facilitated.

In addition, the present invention is not limited to the above-described embodiments as they are, and can be embodied by modifying constituent elements without departing from the gist of the present invention at the implementation stage. Also, various inventions can be formed by appropriate combinations of the plurality of constituent elements disclosed in the above embodiments. For example, some components may be omitted from all components shown in the embodiments. Furthermore, components across different embodiments may be combined as appropriate.

Reference Signs List 11 First member 11a, 11b First flange 12 Second member 12a, 12b Second flange 13 First strain body 13a First structure 13b Second structure Body 13c...Third structure 14, 15...Second elastic body 16...First elastic body 17...Second elastic body.

Claims (9)

a cylindrical first member having a first collar portion inside;
a second member arranged concentrically with the first member and having a second flange on the outside;
A tubular first structure, a tubular second structure provided inside the first structure, and an elastic structure provided between the first structure and the second structure. a first strain body having a third structure, wherein the first member is attached to the outside of the first structure and the second member is attached to the inside of the second structure;
A first end is provided between the first structure and the first collar, a second end is provided between the second structure and the second collar, and has a strain sensor. at least one second strain element;
A load cell comprising a a ring-shaped first elastic body provided between the first collar portion and the first end portion of the second strain-generating body;
a ring-shaped second elastic body provided between the second collar portion and the second end portion of the second strain-generating body;
The load cell of claim 1, further comprising: The load cell according to claim 2, wherein the first elastic body and the second elastic body are disc springs. The load cell according to claim 1, wherein the first collar portion and the second collar portion are elastic bodies. The load cell according to claim 1, wherein the thickness of the third structure is thicker than the thickness of the second strain body. The first structure and the second structure each have a notch into which the second strain body is inserted, and the depth of the notch is shallower than the thickness of the second strain body. A load cell according to claim 1. a cylindrical first member having a first collar portion inside;
a second member arranged concentrically with the first member and having a second flange on the outside;
A tubular first structure, a tubular second structure provided inside the first structure, and an elastic structure provided between the first structure and the second structure. a first strain body having a third structure, wherein the first member is attached to the outside of the first structure and the second member is attached to the inside of the second structure;
a ring-shaped first elastic body provided on the first brim;
a ring-shaped second elastic body provided on the second collar;
A first end is provided between the first structure and the first elastic body, a second end is provided between the second structure and the second elastic body, and has a strain sensor. at least one second strain element;
A load cell comprising a The load cell according to claim 7, wherein the first elastic body and the second elastic body are disc springs. a cylindrical first member having an elastic first brim inside;
a second member arranged concentrically with the first member and having an elastic second brim on the outside;
A tubular first structure, a tubular second structure provided inside the first structure, and an elastic structure provided between the first structure and the second structure. a first strain body having a third structure, wherein the first member is attached to the outside of the first structure and the second member is attached to the inside of the second structure;
A first end is provided between the first structure and the first collar, a second end is provided between the second structure and the second collar, and has a strain sensor. at least one second strain element;
A load cell comprising a

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