JP7159072B2 - 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 fixed (see, for example, Patent Document 1).

JP 2017-172983 A

The strain bodies are fixed to the structure using bolts, for example. 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 precision.

The load cell of this embodiment includes a first structure having a first opening, a second structure having a second opening, and a third structure connecting the first structure and the second structure. , a strain generating body provided with a strain sensor, a first end of which is inserted into the first opening of the first structure and a second end of which is inserted into the second opening of the second structure a first block inserted into the first opening to press the first end of the strain body against the first structure; and a first block inserted into the second opening to press the strain body. a second block having a second end pressed against the second structure.

The top view which shows the load cell which concerns on this embodiment. Sectional drawing along the II-II line of FIG. The exploded perspective view which looked at FIG. 1 from the back side. 2 is a perspective view of FIG. 1; FIG. FIG. 2 is a plan view showing an example of a strain generating body and a strain sensor applied to the present embodiment;

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

1 to 4 show a load cell 10 according to this embodiment.
The load cell 10 includes a first structure 11, a second structure 12 and a third structure 13 as a main body, a first strain body 21, a second strain body 22, and for example two first blocks 31a, 31b, and two second blocks 32a, 32b.

The first structure 11, the second structure 12, and the third structure 13 are integrally made of metal such as stainless steel (SUS). However, the material of the structure is not limited to SUS, and materials such as iron, aluminum, and resin can also be used.

The first structure 11 and the second structure 12 are, for example, cylinders, and the second structure 12 is arranged inside the first structure 11 and concentrically with the first structure 11 . That is, the first structure 11 and the second structure 12 share the central axis.

As shown in FIGS. 2 and 3, the third structure 13 is arranged at one end of the first structure 11 and the second structure 12 in the direction along the axis, for example, at the upper portion thereof. 2 structure 12 is connected. The third structure 13 has elasticity, and the second structure 12 is elastic with respect to the first structure 11 in the direction along the axis (direction of arrow F shown in FIG. 2) and the direction around the axis. It is movable in the direction of arrow T shown in FIG. Also, the third structure 13 has, for example, two windows 13a and 13b along the diameter direction.

The first structure 11 has, for example, two first openings 11a and 11b on the sides corresponding to the two windows 13a and 13b, and the second structure 12 has the sides corresponding to the two windows 13a and 13b. is provided with, for example, two second openings 12a, 12b. The second opening 12a faces the first opening 11a, and the second opening 12b faces the first opening 11b.

The first strain generating body 21 is inserted into the first opening 11 a of the first structure 11 and the second opening 12 a of the second structure 12 . That is, the first end of the first strain generating body 21 is arranged inside the first opening 11a, and the second end is arranged inside the second opening 12a.

The second strain generating body 22 is inserted into the first opening 11 b of the first structure 11 and the second opening 12 b of the second structure 12 . That is, the first end of the second strain generating body 22 is arranged inside the first opening 11b, and the second end is arranged inside the second opening 12b.

The first strain-generating body 21 and the second strain-generating body 22 are made of SUS, for example. The thicknesses of the first strain-generating body 21 and the second strain-generating body 22 are, for example, thinner than the thickness of the third structure 14, and as described later, when the second structure 12 moves relative to the first structure 11, , is deformable.

A first block 31 a is press-fitted into the first opening 11 a of the first structure 11 , and a second block 32 a is press-fitted into the second opening 12 a of the second structure 12 . Further, a first block 31b is press-fitted into the first opening 11b of the first structure 11, and a second block 32b is press-fitted into the second opening 12b of the second structure 12. As shown in FIG.

Each of the first blocks 31a, 31b and the second blocks 32a, 32b is made of an elastic material such as SUS. Although each of the first blocks 31a, 31b and the second blocks 32a, 32b is, for example, a rectangular parallelepiped, the shape is not limited to this, and may be, for example, a wedge shape.

The first end of the first strain generating body 21 is pressed against, for example, the upper surface of the first opening 11a, that is, the first structure 11 by the first block 31a. The second end of the first strain generating body 21 is pressed against, for example, the upper surface of the second opening 12a, that is, the second structure 12 by the second block 32a.

The first end of the second strain generating body 22 is pressed against, for example, the upper surface of the first opening 11b, that is, the first structure 11 by the first block 31b. The second end of the second strain generating body 22 is pressed against, for example, the upper surface of the second opening 12b, that is, the second structure 12 by the second block 32b.

As shown in FIG. 4, the first openings 11a, 11b and the second openings 12a, 12b have a first portion 12-1 and a second portion 12-2. The first portion has a cross-sectional shape similar to that of the first strain-generating body 21 and the second strain-generating body 22, and the second portion 12-2 has a cross-sectional shape similar to that of the first blocks 31a and 31b and the second blocks 32a and 32b. Similar. Therefore, the first strain-generating body 21, the second strain-generating body 22, the first blocks 31a, 31b, and the second blocks 32a, 32b are positioned inside the first openings 11a, 11b and the second openings 12a, 12b. , the first structure 11 and the second structure 12 are regulated so as not to move in the circumferential direction and in the axial direction.

FIG. 5 schematically shows the configuration of the first strain-generating body 21 and the second strain-generating body 22. As shown in FIG.
For example, thin film resistors R1 and R2 as strain sensors (strain gauges) and a plurality of terminals 41, 42 and 43 are arranged on the surface of the first strain generating body 21. FIG. A thin film resistor R1 is connected between terminals 41 and 42, and a thin film resistor R2 is connected between terminals 42 and 43. FIG.

For example, thin film resistors R3 and R4 and a plurality of terminals 44, 45 and 46 as strain sensors are arranged on the surface of the second strain generating body 22. As shown in FIG. Thin-film resistor R3 is connected between terminals 44 and 45, and thin-film resistor R4 is connected between terminals 45 and 46. FIG. These thin film resistors R1 to R4 constitute, for example, a Wheatstone bridge circuit.

As shown in FIG. 2, when a force in the direction of arrow F is applied to the load cell 10 from the outside and the second structure 12 moves in the direction along the axis with respect to the first structure 11, the first strain body 21 and the second strain generating body 22 are deformed. As a result, the thin film resistors R1 to R4 are compressed or expanded, and when the resistance value changes, an electrical signal corresponding to the force applied from the bridge circuit is generated as a sensor output.

The load cell 10 also functions as a torque sensor when force is applied around the axis.

(Effect of Embodiment)
According to the above embodiment, the first structure 11 has the first openings 11a and 11b, the second structure 12 has the second openings 12a and 12b, and the first strain body 21 has The first end is pressed against the first structure 11 by the first block 31a in the first opening 11a, and the second end is pressed against the second structure by the second block 32a in the second opening 12a. The first end of the second strain generating body 22 is pressed against the first structure 11 by the first block 31b in the first opening 11b, and the second end is pressed against the second opening 11b. In the portion 12b, the second block 32b is pressed against the second structure 12. As shown in FIG. Therefore, the load cell 10 can be made smaller than when bolts are used. The second strain-generating body 22 can be reliably fixed to the first structure 11 and the second structure 12 by the first blocks 31a, 31b and the second blocks 32a, 32b. Therefore, even when a weak force is applied to the load cell 10, the applied force can be detected with high accuracy.

Further, according to the present embodiment, the first blocks 31a and 31b are press-fitted into the first openings 11a and 11b, and the second blocks 32a and 32b are press-fitted into the second openings 12a and 12b. A first strain body 21 and a second strain body 22 can be fixed to the first structure 11 and the second structure 12 . Therefore, even when the first structure 11 and the second structure 12 are miniaturized, they are easier to manufacture than when bolts are used, and the manufacturing cost can be reduced.

The first structural body 11 and the second structural body 12 forming the main body are not limited to cylindrical shapes, and may be rectangular parallelepipeds, for example. In this case, the third structure 13 may have any configuration as long as it connects the first structure 11 and the second structure 12 .

The number of strain-generating bodies is not limited to two, and may be one or three or more.

The number of strain gauges provided on the strain generating body is not limited to two, and may be one or four, and the type of strain gauge is not limited to thin film resistors.

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 10 Load cell 11 First structure 11a, 11b First opening 12 Second structure 12a, 12b Second opening 12-1 First part 12-2 Second Part 13 Third structure 21 First strain body 22 Second strain body 31a, 31b First block 32a, 32b Second block R1 to R4 Thin film resistor.

Claims (6)

a first structure having a first opening;
a second structure having a second opening;
a third structure connecting the first structure and the second structure;
a strain body provided with a strain sensor having a first end inserted into the first opening of the first structure and a second end inserted into the second opening of the second structure; ,
a first block inserted into the first opening to press the first end of the strain body against the first structure;
a second block inserted into the second opening to press the second end of the strain generating body against the second structure;
A load cell comprising a the first structure is a cylinder,
The load cell according to claim 1, wherein said second structure is a cylinder arranged concentrically with said first structure. The first opening and the second opening have a first portion into which the first end or the second end of the strain body is inserted and a first portion into which the first block or the second block is inserted. 2. The load cell of claim 1, comprising a second portion that the first structure includes a plurality of the first openings;
the second structure includes a plurality of the second openings;
The strain-generating body includes a plurality of strain-generating bodies inserted into the plurality of first openings and the plurality of second openings,
the first block includes a plurality of the first blocks inserted into the plurality of the first openings;
4. The load cell according to claim 3, wherein said second block includes a plurality of said second blocks inserted into a plurality of said second openings. The third structure is provided between one axial end of the cylindrical first structure and one axial end of the cylindrical second structure, and is provided between the first opening and the second structure. 5. The load cell according to claim 4, comprising a plurality of third openings at positions corresponding to said second openings. a cylindrical first structure having a plurality of first openings;
a cylindrical second structure having a plurality of second openings and arranged concentrically with the first structure;
a third structure connecting the first structure and the second structure;
A plurality of strain sensors are provided, and first ends are respectively inserted into the plurality of first openings of the first structure, and second ends are inserted into the plurality of second openings of the second structure. a plurality of strain-generating bodies to be inserted;
a plurality of first blocks inserted into each of the plurality of first openings to press the first end of the strain body against the first structure;
a plurality of second blocks inserted into each of the plurality of second openings to press the second end of the strain body against the second structure;
A load cell comprising a

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