JP7187358B2 - 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 the present embodiment has a cylindrical first structure having a plurality of first cutouts and a plurality of second cutouts arranged concentrically with the first structure. a second structure, a third structure connecting the first structure and the second structure, and a strain sensor, and a first end of the plurality of the first structures of the first structure are provided. a plurality of strain-generating bodies each inserted into a notch portion, the second ends of which are inserted into the plurality of second notch portions of the second structure; a plurality of first blocks for fixing the first end of the strain-generating body to the first structure; and a plurality of second blocks for fixing to the second structure.

The top view which shows the load cell which concerns on 1st 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 first embodiment; The perspective view which partially exploded and shows the load cell which concerns on 2nd Embodiment. The perspective view which shows the load cell which concerns on 3rd Embodiment. FIG. 7 is a partially exploded perspective view of FIG. 6 ; The perspective view which shows the load cell which concerns on 4th Embodiment. FIG. 9 is a partially exploded perspective view of FIG. 8 ; The perspective view which shows the load cell which concerns on 5th Embodiment. FIG. 11 is a partially exploded perspective view of FIG. 10 ; The perspective view which shows the load cell which concerns on 6th Embodiment. FIG. 13 is a partially exploded perspective view of FIG. 12 ;

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 3 show a load cell 10 according to a first 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. It comprises a strain body 15 and, 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 cutouts 11a, 11b and the second cutouts 12a, 12b are, for example, U-shaped. The inside and the outside of the first structure 11 are communicated by the first notches 11a and 11b, and the inside and the outside of the second structure 12 are communicated by the second notches 12a and 12b.

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 first blocks 16a, 16b and the second blocks 17a, 17b are, for example, rectangular parallelepipeds corresponding to the shapes of the first cutouts 11a, 11b and the second cutouts 12a, 12b. It is made of the same material as the 2nd structure 12 and the 3rd structure 13, or hard rubber.

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.

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 notch portions 11a and 11b and the second notch portions 12a and 12b, respectively. It is regulated so as not to move in the circumferential direction.

The shapes of the first blocks 16a, 16b and the second blocks 17a, 17b are not limited to rectangular parallelepipeds, and can be press-fitted into the first cutouts 11a, 22b and the second cutouts 12a, 12b. Any shape may be employed as long as it can make surface contact or line contact with the first and second ends of the strain bodies 14 and 15 and press the first and second ends.

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.

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.

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

(Effect of the first embodiment)
According to the first embodiment, the first structure 11 has first notches 11a and 11b, the second structure 12 has second notches 12a and 12b, and the first strain-generating A first end of the body 14 is fixed in close contact with the first structure 11 by a first block 16a press-fitted into the first notch 11a, and a second end is a second notch 12a. It is tightly fixed to the second structure 12 by the second block 17a press-fitted inside. 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 reliably and precisely fixed to the first structure 11 and the second structure 12. 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, by press-fitting the first blocks 16a and 16b into the first notches 11a and 11b and press-fitting the second blocks 17a and 17b into the second notches 12a and 12b, , 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.

Further, the first blocks 16a, 16b are press-fitted into the first notches 11a, 11b, and the second blocks 17a, 17b are press-fitted into the second notches 12a, 12b. For this reason, the first blocks 16a and 16b are in close contact with the first notches 11a and 11b, and the second blocks 17a and 17b are in close contact with the second notches 12a and 12b. Therefore, the first blocks 16a, 16b and the second blocks 17a, 17b function as packings that seal the first cutouts 11a, 11b and the second cutouts 12a, 12b. Intrusion can be prevented.

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.

(Second embodiment)
FIG. 5 shows a partially disassembled load cell 10 according to the second embodiment.

In the second embodiment, a first beam portion 18 is provided between each of the first blocks 16a and 16b and each of the second blocks 17a. That is, the first block 16 a and the second block 17 a are connected by the first beam portion 18 , and the first block 16 b and the second block 17 b are connected by the first beam portion 18 . The material of the first beam portion 18 is the same as the material of the first blocks 16a, 16b and the second blocks 17a, 17b.

(Effect of Second Embodiment)
According to the second embodiment, similarly to the first embodiment, the first and second strain generating bodies 14 and 15 can be fixed with high precision by the first blocks 16a and 16b and the second blocks 17a and 17b.

Moreover, according to the second embodiment, the first block 16a and the second block 17a are connected by the first beam portion 18, and the first block 16b and the second block 17b are connected by the first beam portion 18. there is Therefore, when the first structure 11 and the second structure 12 move relative to each other due to the applied load, the first beam 18 causes the first and second strain bodies 14 and 15 to move in the axial direction. can be prevented from being transformed into Therefore, it is possible to detect the applied load with high accuracy.

In addition, since the first blocks 16a and 16b and the second blocks 17a and 17b are connected by the first beam portions 18, respectively, the first blocks 16a and the second blocks 17a are simultaneously connected to the first notch portions 11a and the second blocks 17a and 17b. The first block 16b and the second block 17b can be attached to the first cutout 11b and the second cutout 12b at the same time. Therefore, it is possible to reduce the number of assembly man-hours.

Moreover, since the first blocks 16a and 16b and the second blocks 17a and 17b are connected by the first beam portions 18, the first and second blocks 16a and 17a and the first notch portion 11a and the second It is possible to easily and accurately position the notch 12a. Therefore, it is possible to prevent variations between products and improve quality.

Furthermore, since the first blocks 16a, 16b and the second blocks 17a, 17b are connected by the first beams 18, when the first blocks 16a, 16b and the second blocks 17a, 17b are separated, In comparison, it is possible to facilitate the management of parts.

(Third Embodiment)
6 and 7 show the load cell 10 according to the third embodiment.

In the third embodiment, the first block 16a and the second block 17a connected by the first beam portion 18 and the first block 16b and the second block 17b connected by the first beam portion 18 are further divided into 2 are connected by a beam portion 19 .

The second beam portion 19 is linear along the diameter of the second structure 12 and provided between the second block 17a and the second block 17b. Therefore, the first blocks 16 a and 16 b and the second blocks 17 a and 17 b are integrated by the first beam portion 18 and the second beam portion 19 . The material of the second beam portion 19 is the same as the material of the first beam portion 18 .

(Effect of the third embodiment)
According to the third embodiment, similarly to the first and second embodiments, the first and second strain-generating bodies 14 and 15 are fixed with high precision by the first blocks 16a and 16b and the second blocks 17a and 17b. can be done.

Moreover, according to the third embodiment, the first block 16a and the second block 17a connected by the first beam portion 18 and the first block 16b and the second block 17b connected by the first beam portion 18 are They are connected and integrated by the second beam portion 19 . Therefore, the first blocks 16a, 16b and the second blocks 17a, 17b can be integrally attached to the first notches 11a, 11b and the second notches 12a, 12b. Therefore, compared to the second embodiment, it is possible to further facilitate assembly and prevent variations between products.

Moreover, since it is possible to further reduce the number of parts compared to the second embodiment, it is possible to facilitate the management of parts.

(Fourth embodiment)
8 and 9 show a load cell according to a fourth embodiment.
In 3rd Embodiment, the 2nd beam part 19 is formed in linear form. On the other hand, in the fourth embodiment, the second beam portion 20 is formed in an annular shape.

As shown in FIG. 9, the second structure 12 has a stepped portion 12c along the outer circumference, and the second notches 12d and 12e are provided on the stepped portion 12c. In this case, the second cutouts 12d and 12e do not communicate the inside and the outside of the second structure 12 with each other. However, in order to pull out wiring (not shown) connected to the first and second strain generating bodies 14 and 15 to the inside of the second structure 12, the second Notch portions 12d and 12e may be formed.

The depth of the second cutouts 12d and 12e is, for example, shallower than the thickness of the first and second strain-generating bodies 14 and 15, and the surfaces of the first and second strain-generating bodies 14 and 15 are stepped. It is made possible to slightly protrude from the surface of the portion 12c.

The inner diameter of the annular second beam portion 20 is slightly smaller than the outer diameter of the second structure 12 . Therefore, when the second beam portion 20 is attached to the second structure 12 , the second beam portion 20 is press-fitted into the second structure 12 .

The annular second beam portion 20 is press-fitted to the outside of the second structure 12, and the first blocks 16a and 16b are press-fitted into the first notch portions 11a and 11b. Therefore, the first and second strain generating bodies 14 and 15 are securely fixed to the first structure 11 and the second structure 12 by the second beam portion 20 and the first blocks 16a and 16b.

As shown within the dashed lines in FIG. 9, the annular second beam portion 20 may have second blocks 17a and 17b. In this case, the first and second strain generating bodies 14 and 15 are also fixed to the second structure 12 by the second blocks 17a and 17b.

(Effect of the fourth embodiment)
According to the fourth embodiment, as in the first to third embodiments, the first blocks 16a and 16b (and the second blocks 17a and 17b) and the second beam portion 20 provide the first and second strain bodies 14, 15 can be fixed with high accuracy.

Moreover, according to the fourth embodiment, the first blocks 16a and 16b (and the second blocks 17a and 17b) and the first beam portion 18 are connected and integrated by the annular second beam portion 20. . Therefore, the first blocks 16a and 16b (and the second blocks 17a and 17b) and the annular second beam portion 20 are separated from the first cutout portions 11a and 11b (and the second cutout portions 12a and 12b) and the second cutout portions 12a and 12b. It can be integrally attached to the structure 12 . Therefore, assembly can be facilitated, variations in products can be prevented, and quality can be improved.

Moreover, since the annular second beam portion 20 is press-fitted to the outside of the second structure 12 , it functions as a packing that separates the inside and the outside of the second structure 12 . Therefore, it is possible to prevent dust and moisture from entering between the first structure 11 and the second structure 12, thereby preventing quality deterioration.

(Fifth embodiment)
10 and 11 show the load cell 10 according to the fifth embodiment.
In the fourth embodiment, the annular second beam 20 is attached to the outside of the second structure 12 . In contrast, in the fifth embodiment, the annular second beam portion 30 is mounted inside the second structure 12 .

As shown in FIG. 11, the second structure 12 has a stepped portion 12f along the inner periphery, and the second notches 12g and 12h are provided on the second structure 12 and the stepped portion 12f. It is In this case, the second cutouts 12g and 12h communicate between the inside and the outside of the second structure 12, and the wires (not shown) connected to the first and second strain generating bodies 14 and 15 are connected to the second cutouts 12g and 12h. It can also be used as a passageway for drawing inside the structure 12 .

The depth of the second cutouts 12g and 12h is approximately equal to the sum of the thicknesses of the first and second strain generating bodies 14 and 15 and the thickness of the annular second beam portion 30. As shown in FIG. Therefore, when the first and second strain-generating bodies 14 and 15 are mounted in the second notch portions 12b and 12h, the surfaces of the first and second strain-generating bodies 14 and 15 are slightly above the surface of the stepped portion 12f. protruded to The width W2 of the second cutouts 12g and 12h is approximately equal to or slightly larger than the width W3 of the first and second strain generating bodies 14 and 15. As shown in FIG. Therefore, the movement of the first and second strain generating bodies 14 and 15 in the circumferential direction of the first and second structures 11 and 12 can be restricted.

The annular second beam portion 30 is arranged to connect the second blocks 17a and 17b. The outer diameter of the annular second beam portion 30 is slightly larger than the inner diameter of the second structure 12, and the second beam portion 30 is press-fitted into the second structure 12 when attached to the second structure 12. be done.

The annular second beam portion 30 is press-fitted inside the second structure 12, the first blocks 16a, 16b are press-fitted into the first notches 11a, 11b, and the second blocks 17a, 17b are press-fitted into the second structure. It is press-fitted into the notch portions 12g and 12h. Therefore, the first and second strain generating bodies 14 and 15 are attached to the first structure 11 and the second structure 12 by the first blocks 16a and 16b, the second blocks 17a and 17b, and the second beam portions 20. securely fixed.

(Effect of the fifth embodiment)
According to the fifth embodiment, as in the first to fourth embodiments, first blocks 16a and 16b, second blocks 17a and 17b, and second beam portions 30 provide first and second strain-generating bodies 14 and 15. can be fixed with high precision.

Moreover, according to the fifth embodiment, the first blocks 16 a and 16 b, the second blocks 17 a and 17 b, and the first beam portion 18 are connected and integrated by the annular second beam portion 30 . Therefore, the first blocks 16a and 16b and the second blocks 17a and 17b and the annular second beam portion 30 are connected to the first cutout portions 11a and 11b, the second cutout portions 12a and 12b and the second structure 12. It can be worn integrally. Therefore, assembly can be facilitated, variations in products can be prevented, and quality can be improved.

In addition, the annular second beam portion 30 is press-fitted inside the second structure 12, and the second blocks 17a and 17b are press-fitted into the second notches 12a and 12b. It acts as a packing that separates the inside from the outside. Therefore, it is possible to prevent dust and moisture from entering between the first structure 11 and the second structure 12, thereby preventing quality deterioration.

(Sixth embodiment)
12 and 13 show a load cell according to the sixth embodiment.
The sixth embodiment is a modification of the first embodiment, and as shown in FIG. A spring washer 40 is provided between each of the two strain generating bodies 15 .

In a state where the first blocks 16a and 16b are press-fitted into the first cutouts 11a and 11b and the second blocks 17a and 17b are press-fitted into the second cutouts 12a and 12b, the first and second strain generating bodies 14 , 15 are fixed to the first structure 11 by spring washers 40 and first blocks 16a, 16b, and fixed to the second structure 12 by spring washers 40 and second blocks 17a, 17b.

(Effect of the sixth embodiment)
According to the sixth embodiment, similarly to the first to fifth embodiments, the first and second strain generating bodies 14 and 15 are fixed with high accuracy by the first blocks 16a and 16b and the second blocks 17a and 17b. can be done.

Moreover, according to the sixth embodiment, spring washers 40 are provided between the first blocks 16a, 16b and the first strain body 14 and between the second blocks 17a, 17b and the second strain body 15, respectively. is provided. Therefore, the elasticity of the spring washer 40 enables the first and second strain-generating bodies 14 and 15 to be firmly fixed to the first structure 11 and the second structure 12, thereby providing a vibration-resistant load cell. can be configured.

It is also possible to apply the spring washer 40 according to the sixth embodiment to the second to fifth embodiments.

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, 12d, 12e, 12g, 12h Second notch 12c, 12f Step 13 Third structure 14 First strain body 15 Second strain body 16a, 16b First block 17a, 17b Second block 18 First beam 19 , 20, 30... second beam portion, 40... spring washer, R1 to R4... thin film resistor.

Claims (7)

a cylindrical first structure having a plurality of first notches;
a cylindrical second structure having a plurality of second notches and arranged concentrically with the first structure;
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;
A load cell comprising: 2. The load cell according to claim 1, wherein widths of said first block and said second block are wider than respective widths of said first cutout portion and said second cutout portion. 3. The load cell according to claim 2, further comprising a first beam provided between each of said first blocks and each of said second blocks. 4. The load cell according to claim 3, further comprising a second beam portion provided between said second blocks. 5. The load cell according to claim 4, wherein the second beam portion is annular and provided on the outer periphery of the second structure. 5. The load cell according to claim 4, wherein the second beam portion is annular and provided on the inner circumference of the second structure. springs between each of the first blocks and the first end of each of the strain bodies and between each of the second blocks and the second end of each of the strain bodies; 3. The load cell of claim 2, further comprising a washer.

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