JP7187359B2 - 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 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 cut-out portions of the strain-generating bodies and the first end portions of the strain-generating bodies being press-fitted into the plurality of the first cut-out portions to fix the first end portions of the strain bodies to the first structure. , a plurality of first blocks having first stoppers, and a plurality of second cutouts, respectively, for fixing the second ends of the strain-generating bodies to the second structure, and the first stoppers. and a plurality of second blocks having second stops spaced a predetermined distance from each other.

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 shows the load cell which concerns on 2nd Embodiment. FIG. 6 is a partially exploded perspective view of FIG. 5 ;

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 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. 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 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 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 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.

The first blocks 16a and 16b have first stoppers ST11 and ST12, respectively, and the second blocks 17a and 17b have second stoppers ST13 and ST14, respectively.

The first stopper ST11 has first stopper members 16a-1 and 16a-2, and the first stopper ST12 has first stopper members 16b-1 and 16b-2. The first stopper members 16a-1, 16a-2 extend from the first block 16a toward the second structure 12, and the first stopper members 16b-1, 16b-2 extend from the first block 16b to the second structure. It extends in the direction of the structure 12 .

The first stopper member 16a-1 and the first stopper member 16a-2, and the first stopper member 16b-1 and the first stopper member 16b-2 are arranged in the circumferential direction of the first structure 11 and the second structure 12, respectively. are separated by a predetermined distance. In other words, the first stopper member 16a-1 and the first stopper member 16a-2 are separated from each other by a predetermined distance, for example, in the direction of torque application (direction of arrow T shown in FIG. 2). The stopper member 16b-2 is also separated by a predetermined distance in the torque application direction.

The second stoppers ST13 and ST14 have second stopper members 17a-1 and 17b-1, respectively. The second stopper member 17a-1 extends from the second block 17a toward the first structure 11 and is arranged between the first stopper members 16a-1 and 16a-2. The second stopper member 17b-1 extends from the second block 17b toward the first structure 11 and is arranged between the first stopper members 16b-1 and 16b-2.

Distance between first stopper members 16a-1, 16a-2 and second stopper member 17a-1, and distance between first stopper members 16b-1, 16b-2 and second stopper member 17b-1 is equal to the distance that the first structure 11 and the second structure 12 move relative to each other when a rated load in the torque direction is applied to the load cell 10 . Therefore, when a torque equal to or greater than the rated load is applied to the load cell 10, one of the first stopper members 16a-1, 16a-2, 16b-1, and 16b-2 will move to the second stopper members 17a-1 and 17b-. 1, and breakage of the first and second strain generating bodies 14 and 15 is prevented.

The shapes of the first stoppers ST11 and ST12 are not limited to those described above, and can be modified as shown within the dashed lines in FIG. That is, the first stopper ST11 and the second stopper ST13 are configured by one stopper member. The distance between the first stopper ST11 and the second stopper ST13 is the same as above.

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.

In the case of the first embodiment, since the load cell 10 has the first stoppers ST11, ST12 and the second stoppers ST13, ST14, the load cell 10 can also function as a torque sensor.

(Effect of the first embodiment)
According to the first embodiment, the first structure 11 has first cutouts 11a, 11b and the second structure 12 has second cutouts 12a, 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, 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 blocks 16a and 16b are provided with first stoppers ST11 and ST12, respectively, and the second blocks 17a and 17b are provided with a second stopper ST13 separated from the first stoppers ST11 and ST12 by a predetermined distance in the torque application direction. , ST14, respectively. Therefore, the first strain-generating body 14 and the second strain-generating body 15 can be protected when a force in the torque direction exceeding the rated load or a translational force in the direction of the arrow X shown in FIG. 1 is applied to the load cell 10. It is possible.

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)
5 and 6 show the load cell 10 according to the second embodiment.
The load cell 10 according to the first embodiment includes first and second stoppers ST11 to ST14 that protect the first and second strain generating bodies 14 and 15 against force in the torque direction. In contrast, the load cell 10 according to the second embodiment includes first and second stoppers ST21 to ST24 that protect the first and second strain generating bodies 14 and 15 against forces other than those in the torque direction. there is

The first stopper ST21 has first stopper members 16a-3 and 16a-4, and the first stopper ST22 has first stopper members 16b-3 and 16b-4. The first stopper members 16a-3, 16a-4 extend from the first block 16a toward the second structure 12, and the first stopper members 16b-3, 16b-3 extend from the first block 16b to the second structure. It extends in the direction of the structure 12 .

The first stopper member 16a-3 and the first stopper member 16a-4, and the first stopper member 16b-3 and the first stopper member 16b-4 are arranged along the axes of the first structure 11 and the second structure 12, respectively. are spaced apart by a predetermined distance in the direction of In other words, the first stopper member 16a-3 and the first stopper member 16a-4 are separated by a predetermined distance in the direction of the arrow Z shown in FIG. They are separated by a predetermined distance in the direction of the arrow Z.

The second stoppers ST23, ST24 have second stopper members 17a-2, 17b-2, respectively. The second stopper member 17a-2 extends from the second block 17a toward the first structure 11 and is arranged between the first stopper members 16a-3 and 16a-4. The second stopper member 17b-2 extends from the second block 17b toward the first structure 11 and is arranged between the first stopper members 16b-3 and 16b-4.

Distance between first stopper members 16a-3, 16a-4 and second stopper member 17a-2, and distance between first stopper members 16b-3, 16b-4 and second stopper member 17b-2 is equal to the distance that the first structure 11 and the second structure 12 move relative to each other when a rated load is applied to the load cell 10 in a direction other than torque. Therefore, when a force other than torque exceeding the rated load is applied to the load cell 10, any one of the first stopper members 16a-3, 16a-4, 16b-3, and 16b-4 will move to the second stopper member 17a-2. , 17b-2, and breakage of the first and second strain generating bodies 14, 15 is prevented.

The shapes of the first stoppers ST21 and ST22 are not limited to those described above, and can be modified as shown within the dashed lines in FIG. That is, the first stopper ST21 is composed of one stopper member like the second stopper ST23. The distance between the first stopper ST21 and the second stopper ST23 is the same as described above.

In the case of the second embodiment, since the load cell 10 has the first stoppers ST21, ST22 and the second stoppers ST23, ST24, the load cell 10 can also function as a force sensor.

(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, the first blocks 16a and 16b are provided with first stoppers ST21 and ST22, respectively, and the second blocks 17a and 17b are axially separated from the first stoppers ST21 and ST22, respectively, by a predetermined distance from the first and second structures. It has spaced apart second stoppers ST23 and ST24. Therefore, it is possible to protect the first strain-generating body 14 and the second strain-generating body 15 when a force in a direction other than the torque exceeding the rated load is applied to the load cell 10 .

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 13 Third structure 14 First riser Strain body 15 Second strain-generating body 16a, 16b First block 17a, 17b Second block ST11, ST12, ST21, ST22 First stopper ST13, ST14, ST23, ST24 Second stopper , 16a-1 to 16a-4, 16b-1 to 16b-4... first stopper member, 17a-1, 17b-1, 17a-2, 17b-2... second stopper member, R1 to R4... thin film resistor .

Claims (7)

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 each press-fitted into the plurality of first cutouts to fix the first end of the strain body to the first structure and having a first stopper;
A plurality of second stoppers press-fitted into the plurality of second notches, respectively, fixing the second end of the strain-generating body to the second structure, and spaced apart from the first stopper by a predetermined distance. a second block;
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 widths of said first notch and said second notch. 3. The load cell of claim 2, wherein said first structure is cylindrical and said second structure is cylindrical concentrically disposed with said first structure. 4. The load cell according to claim 3, wherein said second stopper is spaced from said first stopper in the circumferential direction of said first and second structures. The first stopper has a pair of first stopper members extending in the direction of the second structure and spaced apart in the circumferential direction of the first and second structures, the second stopper comprising: 5. The load cell according to claim 4, further comprising a second stopper member extending toward said first structure and disposed between said pair of said first stopper members. 4. The load cell according to claim 3, wherein said second stopper is spaced apart from said first stopper in the axial direction of said first and second structures. The first stopper has a pair of first stopper members extending in the direction of the second structure and spaced apart in the axial direction of the first and second structures, the second stopper comprising: 7. The load cell according to claim 6, further comprising a second stopper member extending toward said first structure and disposed between said pair of said first stopper members.

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