JP7191737B2 - 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, 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 plurality of first notches, a second structure having a plurality of second notches, and the first structure and the second structure. A third structure to be connected and a strain sensor are provided. and a plurality of strain-generating bodies inserted into the second cutout portions of the strain-generating bodies, and the first end portions of the strain-generating bodies being press -fitted into the plurality of first cutout portions, respectively, to be fixed to the first structure. a plurality of first blocks; a plurality of second blocks press-fitted into the plurality of second cutouts to fix the second end of the strain-generating body to the second structure; and a first end. are provided in the plurality of first notches, and second ends are provided in the plurality of second notches, respectively, and a plurality of third blocks that fix the first block and the second block; ,

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

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

(embodiment)
1 to 4 show a load cell 10 according to an embodiment.
The load cell 10 includes a first structural body 11, a second structural body 12 and a third structural body 13 as a main body, a first strain body 14 constituting a first sensor chip, and a second strain body constituting a second sensor chip. The strain body 15 comprises, for example, two first blocks 16a, 16b and two second blocks 17a, 17b.

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 located substantially midway between the first structure 11 and the second structure 12 in the direction along the axis of the first structure 11 and the second structure. connect with the body 12; The third structure 13 has elasticity, and the second structure 12 moves toward the first structure 11 in the direction along the axis (the direction of arrow Z shown in FIGS. 1 and 2) and the axis. It is made movable in the turning direction (direction of arrow T shown in FIG. 2).

The first structure 11 comprises, for example, two first cutouts 11a, 11b in the diametrical direction, and the second structure 12 also comprises, for example, two second cutouts 12a, 12b in the diametrical direction. there is The first notch 11a and the second notch 12a face each other, and the first notch 11b and the second notch 12b face each other.

The first structure 11 and the second structure 12 are not necessarily cylindrical, and are connected to each other by the third structure 13 to form the first cutouts 11a, 11b and the second cutouts 12a, 12b. For example, it may be a rectangular parallelepiped as long as it is provided.

The first strain generating body 14 is inserted into the first notch portion 11 a of the first structure 11 and the second notch portion 12 a of the second structure 12 . That is, the first end of the first strain generating body 14 is arranged in the first notch 11a, and the second end is arranged in the second notch 12a.

The second strain generating body 15 is inserted into the first notch portion 11 b of the first structure 11 and the second notch portion 12 b of the second structure 12 . That is, the first end of the second strain generating body 15 is arranged in the first notch 11b, and the second end is arranged in the second notch 12b.

The first strain-generating body 14 and the second strain-generating body 15 are made of SUS, for example. The thicknesses of the first strain-generating body 14 and the second strain-generating body 15 are, for example, thinner than the thickness of the third structure 13, and as described later, when the second structure 12 moves relative to the first structure 11, , is deformable.

A first block 16 a is provided in the first notch 11 a of the first structure 11 , and a second block 17 a is provided in the second notch 12 a of the second structure 12 . Further, a first block 16b is provided in the first cutout portion 11b of the first structure 11, and a second block 17b is provided in the second cutout portion 12b of the second structure 12. As shown in FIG.

The shapes of the first blocks 16a, 16b and the second blocks 17a, 17b correspond to the shapes of the first notches 11a, 11b and the second notches 12a, 12b.

The first blocks 16a, 16b and the second blocks 17a, 17b are made of the same material as the first structure 11, the second structure 12, and the third structure 13, or hard rubber, for example.

As shown in FIG. 3, the width W1 of the first blocks 16a and 16b and the second blocks 17a and 17b is the same as the first cutouts 11a and 11b of the first structure 11 and the second cutouts of the second structure 12. It is slightly wider than the width W2 of the cutouts 12a and 12b (W1>W2). Therefore, the first blocks 16a, 16b and the second blocks 17a, 17b are press-fitted into the first notches 11a, 11b and the second notches 12a, 12b, respectively.

A first end portion of the first strain generating body 14 is pressed against, for example, the upper surface of the first notch portion 11a, that is, the first structure 11 by the first block 16a. The second end of the first strain generating body 14 is pressed against, for example, the upper surface of the second notch 12a, that is, the second structure 12 by the second block 17a.

A first end portion of the second strain generating body 15 is pressed against, for example, the upper surface of the first notch portion 11b, that is, the first structure 11 by the first block 16b. The second end of the second strain generating body 15 is pressed against, for example, the upper surface of the second notch 12b, that is, the second structure 12 by the second block 17b.

However, the width W1 of the first blocks 16a, 16b and the second blocks 17a, 17b may be equal to or slightly narrower than the width W2 of the first cutouts 11a, 11b and the second cutouts 12a, 12b. (W1≦W2). That is, the first blocks 16a, 16b and the second blocks 17a, 17b are inserted into the first cutouts 11a, 11b and the second cutouts 12a, 12b, respectively. They may be placed on the strain-generating bodies 15, respectively.

The width W2 of the first cutouts 11a, 11b and the second cutouts 12a, 12b is substantially equal to or slightly larger than the width W3 of the first strain-generating body 14 and the second strain-generating body 15 (W2≧W3). . Therefore, the first and second strain-generating bodies 14 and 15 are arranged in the first cutouts 11a and 11b and the second cutouts 12a and 12b, respectively. It is regulated so as not to move in the circumferential direction.

The first structure 11 has third cutouts 11a-1 and 11b-1 communicating with the first cutouts 11a and 11b, respectively, and the second structure 12 has second cutouts 12a and 12b. and fourth cutouts 12a-1 and 12b-1, respectively.

The third cutouts 11a-1 and 11b-1 and the fourth cutouts 12a-1 and 12b-1 are central portions in the width direction of the first cutouts 11a and 11b and the second cutouts 12a and 12b. is provided in

The width W4 of the third cutouts 11a-1 and 11b-1 and the fourth cutouts 12a-1 and 12b-1 is equal to the width W2 of the first cutouts 11a and 11b and the second cutouts 12a and 12b. Narrower (W4<W2).

A third block 18a is provided between the third cutout portion 11a-1 and the fourth cutout portion 12a-1. A third block 18b is provided between them.

The third block 18a is press-fitted between the third cutout portion 11a-1 and the fourth cutout portion 12a-1, and the third block 18b is inserted between the third cutout portion 11b-1 and the fourth cutout portion. 12b-1.

Specifically, the width W5 of the third blocks 18a and 18b is slightly wider than the width W4 of the third cutouts 11a-1 and 11b-1 and the fourth cutouts 12a-1 and 12b-1 (W5 >W4). Alternatively, the length L1 of the third blocks 18a and 18b is the length between the third cutout portion 11a-1 and the fourth cutout portion 12a-1, and the length between the third cutout portion 11b-1 and the fourth cutout portion 11b-1. It is longer than the length L2 between the notch 12b-1.

Either or both of the above conditions for press-fitting the third blocks 18a and 18b into the third cutouts 11a-1 and 11b-1 and the fourth cutouts 12a-1 and 12b-1 are provided. may

In this manner, the third block 18a is press-fitted between the third cutout portion 11a-1 and the fourth cutout portion 12a-1, and the third block 18b is inserted between the third cutout portion 11b-1 and the fourth cutout portion 12a-1. 4 is press-fitted between the notch portion 12b-1. Therefore, the first blocks 16a, 16b and the second blocks 17a, 17b are pressed by the third blocks 18a, 18b, and the first strain-generating body 14 and the second strain-generating body 15 are pressed against the first blocks 16a, 16b, It is fixed to the first structure 11 and the second structure 12 by the second blocks 17a and 17b.

FIG. 4 schematically shows configurations of the first strain-generating body 14 and the second strain-generating body 15 .
Thin-film resistors R1 and R2, for example, as strain sensors (strain gauges) are arranged on the surface of the first strain-generating body 14, and thin-film resistors R3, for example, as strain sensors are arranged on the surface of the second strain-generating body 15. , R4 are arranged. The thin film resistors R1 to R4 are arranged at positions where a large strain occurs in the first and second strain generating bodies 14 and 15. FIG. Specifically, the thin-film resistors R1 to R4 are arranged closer to the second structure 12 than the central portions of the first and second strain generating bodies 14 and 15 in the longitudinal direction.

The thin film resistors R1 to R4 constitute, for example, a Wheatstone bridge circuit (not shown), and the output signal of the load cell is output from this bridge circuit. The configuration of the bridge circuit can be changed as appropriate.

As shown in FIG. 2, when a force in the direction of the arrow Z 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 14 and the second strain-generating body 15 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.

(Effect of Embodiment)
According to this embodiment, the first structure 11 has first notches 11a and 11b, and the second structure 12 has second notches 12a and 12b. A first end portion of the first strain generating body 14 is fixed in close contact with the first structure 11 by a first block 16a press-fitted into the first notch portion 11a, and a second end portion is a second It is fixed in close contact with the second structure 12 by the second block 17a press-fitted into the notch 12a. A first end of the second strain generating body 15 is fixed in close contact with the first structure 11 by a first block 16b press-fitted into the first notch 11b, and the second end is It is fixed in close contact with the second structure 12 by the second block 17b press-fitted into the second notch 12b. Therefore, the load cell 10 can be made smaller than when the strain-generating bodies are fixed using bolts. By the first blocks 16a, 16b and the second blocks 17a, 17b, the first strain-generating body 14 and the second strain-generating body 15 can be fixed to the first structure 11 and the second structure 12 with high precision. can. 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 16a and 16b are press-fitted or inserted into the first cutouts 11a and 11b, and the second blocks 17a and 17b are press-fitted or inserted into the second cutouts 12a and 12b. By inserting them, the first strain body 14 and the second strain body 15 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.

Furthermore, the first blocks 16a, 16b and the second blocks 17a, 17b are press-fitted between the third cutouts 11a-1, 11b-1 and the fourth cutouts 12a-1, 12b-1, respectively. are pressed by the third blocks 18a and 18b. Therefore, the first strain-generating body 14 and the second strain-generating body 15 are formed by the first blocks 16a, 16b, the second blocks 17a, 17b, and the third blocks 18a, 18b. It is fixed to the body 12 more firmly. Therefore, a load cell capable of transmitting the force applied to the load cell 10 to the first strain-generating body 14 and the second strain-generating body 15 and detecting a weak force with high accuracy is constructed. be able to.

(Modification)
The third blocks 18a, 18b are press-fitted between the third cutouts 11a-1, 11b-1 and the fourth cutouts 12a-1, 12b-1, respectively. However, the present invention is not limited to this, and as shown within the dashed lines in FIG. It is also possible to press-fit into each.

In this case, the width W6 of the third blocks 18a, 18b is slightly wider than the width W2 of the first cutouts 11a, 11b and the second cutouts 12a, 12b (W6>W2). Alternatively, the length L3 of the third blocks 18a and 18b is slightly longer than the length L4 between the first cutout portion 11a and the second cutout portion 12a (L3>L4).

As a result, the third blocks 18a and 18b are press-fitted between the first notch portions 11a and 11b and the second notch portions 12a and 12b, respectively, and the third blocks 18a and 18b cause the first strain-generating body 14 to move. And the second strain generating body 15 is fixed to the first structure 11 and the second structure 12 by first blocks 16a and 16b and second blocks 17a and 17b.

(Effect of modification)
This modification can also provide the same effects as the embodiment. Moreover, in this modification, the width W6 of the third blocks 18a, 18b is slightly wider than the widths of the first blocks 16a, 16b and the second blocks 17a, 17b. Therefore, the first ends of the third blocks 18a, 18b contact substantially the entire top surfaces of the third blocks 18a, 18b, and the second ends of the third blocks 18a, 18b contact the second blocks 17a, 17b. almost the entire surface of the upper surface of the Therefore, the first strain-generating body 14 and the second strain-generating body 15 are firmly fixed to the first structure 11 and the second structure 12 through the first blocks 16a, 16b and the second blocks 17a, 17b. be able to.

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 notch 12 Second structure 12a, 12b Second notch 11a-1, 11b-1 Third notch Part 12a-1, 12b-1... Fourth notch part 13... Third structure 14... First strain-generating body 15... Second strain-generating body 16a, 16b... First block 17a, 17b . . 2nd block, 18a, 18b .. 3rd block, R1 to R4 .

Claims (6)

a first structure having a plurality of first notches;
a second structure having a plurality of second notches;
a third structure connecting the first structure and the second structure;
A strain sensor is provided, the first end being inserted into the plurality of first notches of the first structure, and the second end being inserted into the plurality of second notches of the second structure. a plurality of strain-generating bodies to be inserted;
a plurality of first blocks press- fitted into the plurality of first notches, respectively, to fix the first end of the strain-generating body to the first structure;
a plurality of second blocks that are press -fitted into the plurality of second cutouts to fix the second end of the strain generating body to the second structure;
First ends are provided in the plurality of first notches, and second ends are provided in the plurality of second notches, respectively, to fix the first block and the second block. a third block;
A load cell comprising: 2. The load cell according to claim 1, wherein the width of the third block is wider than the widths of the first cutout and the second cutout. 3. The load cell according to claim 1, wherein the length of said third block is longer than the length between said first notch and said second notch. The first structure has a third cutout communicating with the first cutout, the second structure has a fourth cutout communicating with the second cutout, The width of the third cutout portion and the fourth cutout portion is narrower than the width of the first cutout portion and the second cutout portion, and the width of the third block is the width of the third cutout portion and the width of the fourth cutout portion. 2. The load cell according to claim 1, wherein the width is wider than the width of the fourth notch. The first structure has a third cutout communicating with the first cutout, the second structure has a fourth cutout communicating with the second cutout, 3. The load cell according to claim 1, wherein the length of said third block is longer than the length between said third cutout portion and said fourth cutout portion. 2. The load cell according to claim 1, wherein widths of said first block and said second block are wider than widths of said first notch and said second notch.

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