JP2021139626A - Force sensor - Google Patents

Abstract

To provide a force sensor with a configuration that can detect forces and moments with high accuracy by significantly improving the misalignment of multiple strain gauges and the variation in resistance values.SOLUTION: A force sensor 1 includes: a first strain body 11 having a first main surface 11a in which a plurality of first strain gauges are arranged; and a second strain body 12 having a second main surface 12a on which a plurality of second strain gauges are arranged. The first strained body 11 and the second strained body 12 have a configuration in which the first main surface 11a and the second main surface 12a are connected and fixed outward to each other or inward to each other.SELECTED DRAWING: Figure 1

Description

The present invention relates to a strain gauge type force sensor.

Strain gauge type force sensors are used for advanced control of measuring instruments and industrial robots. In the known 6-axis force sensor, a plurality of strain gauges are arranged on each of a total of four surfaces of the upper surface, the lower surface, the right side surface, and the left side surface of the arm portion of the strain generating body. Therefore, a large number of strain gauges are provided, and the wiring of the strain gauges becomes very complicated, so that the price is high. Therefore, there has been proposed a force sensor having a configuration in which a plurality of strain gauges are provided in a predetermined arrangement on a total of two surfaces of the strain-causing body (see Patent Document 1: Patent No. 6047703). Further, a force sensor having a configuration in which a plurality of strain gauges are provided only on the main surface of the strain-causing body in a predetermined arrangement has been proposed (see Patent Document 2: Patent No. 6378381).

Japanese Patent No. 6047703 Japanese Patent No. 6378381

The configuration described in Patent Document 1 is such that the arrangement of the plurality of strain gauges arranged on the upper surface and the arrangement of the plurality of strain gauges arranged on the lower surface coincide with each other in a plan view. This is important for ensuring detection accuracy. However, there is a problem that the position shift of the strain gauge and the variation of the resistance value are likely to occur. On the other hand, the configuration described in Patent Document 2 is different from the method of deformation due to an external force between the main surface on which the strain gauge is arranged and the surface on the opposite side in the strain-causing body. There is a problem that the symmetry is inferior. Therefore, it is desired to improve the detection accuracy by further improving the position accuracy of the strain gauge.

The present invention has been made in view of the above circumstances, and by significantly improving the positional deviation of a plurality of strain gauges and the variation in resistance values, it is possible to provide a force sensor having a configuration capable of detecting a force and a moment with high accuracy. With the goal.

As an embodiment, the problem is solved by a solution means as disclosed below.

The force sensor according to the present invention has a first strain generating body having a first main surface on which a plurality of first strain gauges are arranged, and a second main surface on which a plurality of second strain gauges are arranged. A second main surface is provided, and the first main surface and the second main surface are connected and fixed to each other with the first main surface and the second main surface facing outward or inward with each other. It is characterized by being.

According to this configuration, the first strain-generating body and the second strain-causing body have a plurality of first strain gauges arranged on the first main surface and a plurality of second strains arranged on the second main surface. Since the strain gauges are arranged and fixed so as to coincide with each other in a plan view, the misalignment is greatly improved and the force and the moment can be detected with high accuracy.

According to the present invention, it is possible to realize a force sensor capable of detecting a force and a moment with high accuracy while greatly improving the misalignment and improving the productivity.

FIG. 1 is a schematic perspective view showing an example of a force sensor according to the first embodiment of the present invention. FIG. 2 is a schematic structural development view of the force sensor shown in FIG. FIG. 3 is a schematic structural development view of the force sensor shown in FIG. FIG. 4A is a schematic perspective view of the first strain generating body in the force sensor shown in FIG. 1, and FIG. 4B is a schematic perspective view of the second strain generating body in the force sensor shown in FIG. FIG. 5 is a schematic perspective view showing an example of a force sensor according to a second embodiment of the present invention.

(First Embodiment)
Hereinafter, the first embodiment of the present invention will be described in detail with reference to the drawings. The force sensor 1 of the present embodiment has force components Fx, Fy, Fz in the three-axis directions of the Cartesian coordinate system (X-axis, Y-axis, Z-axis) in the three-dimensional space, and moment components Mx around the three axes. It is a 6-axis force sensor that can detect a total of 6 components of My and Mz at the same time. The force sensor 1 (1A) of the present embodiment is an example in which three beam portions 11e indicated by a portion surrounded by a broken line are provided at positions that are rotationally symmetric with respect to the central axis P1.

FIG. 1 is a schematic perspective view showing an example of the force sensor 1A according to the present embodiment, FIG. 2 is a schematic structural development view of the force sensor 1A viewed from diagonally above, and FIG. 3 is an obliquely downward view. It is a schematic structural development view of the force sensor 1A seen from (the signal processing unit and wiring are not shown). In all the drawings for explaining the embodiment, members having the same function may be designated by the same reference numerals, and the repeated description thereof may be omitted.

As shown in FIGS. 1 to 3, the force sensor 1A includes a first strain body 11 having a first main surface 11a on which a plurality of first strain gauges 31 to 34 are arranged, and a plurality of second strains. A second strain 12 having a second main surface 12a on which gauges 41 to 44 are arranged, and an intermediate 13 disposed between the first strain 11 and the second strain 12 The first straining body 11 and the second straining body 12 are connected and fixed by a fixing member 51 with the intermediate body 13 interposed therebetween. In this example, the table 14 and the base 15 are provided, the table 14 and the second strain generating body 12 are connected and fixed by a fixing member 52 such as a bolt, and the first strain generating body 11 and the base 15 are bolted. It is connected and fixed by a fixing member 51 such as. Instead of the fixing member 51 and the fixing member 52, it is also possible to bond and fix with an adhesive or the like.

The first strain-generating body 11 and the second strain-causing body 12 have a configuration in which the first main surface 11a and the second main surface 12a are connected and fixed to each other outward or inward. In the examples shown in FIGS. 1 to 3, the first main surface 11a and the second main surface 12a are connected and fixed to each other outward. Here, the first main surface 11a is in the same direction as the arrow in the Z-axis direction in the drawing, and the second main surface 12a is in the opposite direction to the arrow in the Z-axis direction in the drawing. A recess 14a is formed on the lower side of the table 14, and a recess 15a is formed on the upper side of the base so as not to prevent deformation of the first strain generating body 11 and the second strain generating body 12 due to the force. It has become. As a configuration other than the above, in the first strain-generating body 11 and the second strain-causing body 12, the first main surface 11a and the second main surface 12a may be connected and fixed to each other inward.

As an example, the first strain generating body 11 and the second strain generating body 12 are obtained by forming through holes or the like in a springy material such as an aluminum alloy, alloy steel, or stainless steel using an NC processing machine. .. As an example, the first strain-causing body 11 and the second strain-causing body 12 are formed by subjecting a plate-shaped body having a circular outer shape to cutting, laser processing, electric discharge machining, or a combination of these.

As an example, the first straining body 11 and the second straining body 12 are made of metallic glass. As an example, the first strain-causing body 11 and the second strain-causing body 12 are made of metallic glass obtained by forming an amorphous metal using a mold or the like. Since the molding surface of the mold can be transferred to the metal glass on the nano-order, the first main surface 11a for providing the insulating layer can be made a mirror surface at the same time as the molding of the first strain 11, and the second riser The second main surface 12a for providing the insulating layer at the same time as the modeling of the strain body 12 can be made a mirror surface. Therefore, the processing time of the first strain-causing body 11 and the second strain-causing body 12 can be significantly shortened. As an example, the first strain-causing body 11 and the second strain-causing body 12 are made of Fe-Co-Si-B-Nb-based metallic glass. The structure is not limited to the above, and the first strain-generating body 11 and the second strain-causing body 12 may be manufactured by a known manufacturing method using a known material.

As an example, the first strain gauges 31 to 34 and the second strain gauges 41 to 44 have a configuration in which the wiring pattern of a metal thin film of a Cu—Ni-based alloy or a Ni—Cr-based alloy is covered with a polyimide film or an epoxy film. In some cases, a semiconductor thin film is used. As an example, there is a case where a strain gauge made of a metal thin film is directly formed by using a sputtering method or a vacuum vapor deposition method.

FIG. 4A is a schematic perspective view of the first strain-causing body 11, and FIG. 4B is a schematic perspective view of the second strain-causing body 12. The first strain-causing body 11 and the second strain-causing body 12 are plate-shaped bodies having a shape that is rotationally symmetric with respect to the central axis P1. The first strain generating body 11 is a beam portion that connects a receiving portion 11c located on the central axis P1, a fixing portion 11d fixed to the receiving portion 11c, and the receiving portion 11c and the fixing portion 11d. It has 11e and. Similarly, the second strain generating body 12 connects the receiving portion 12c located on the central axis P1, the fixing portion 12d fixed to the receiving portion 12c, and the receiving portion 12c and the fixing portion 12d. It has a beam portion 12e to be used. The receiving portion 11c, the beam portion 11e, and the fixing portion 11d are integral structures. The size of each portion of the first strain generating body 11 is set so that the beam portion 11e can be regarded as an elastic body when the receiving portion 11c and the fixed portion 11d are regarded as rigid bodies. The same applies to the second strain body 12.

In this embodiment, the first strain-generating body 11 and the second strain-causing body 12 have the same structure. As a result, symmetry can be maintained and productivity is improved without increasing the types of parts. As an example, the first strain-causing body 11 and the second strain-causing body 12 have the same structure and are made of the same material. As a result, it is possible to easily manufacture a strain-causing body having excellent symmetry at low cost. As an example, by providing the intermediate body 13, it is possible to easily provide a space (gap) necessary for wiring and arranging a circuit board. Then, it is possible to easily wire the bridge circuit by utilizing the third main surface 11b of the first strain-generating body 11 and the fourth main surface 12b of the second strain-causing body 12.

As an example, the first strain gauges 31 to 34 and the second strain gauges 41 to 44 are made of a sputter film of the same material or a vapor deposition film of the same material. As a result, the symmetry can be maintained, the productivity can be improved, and the manufacturing variation can be suppressed as much as possible. As an example, the first strain gauges 31 to 34 and the second strain gauges 41 to 44 can be configured to be formed at the same time. As a result, the resistance values of the first strain gauges 31 to 34 and the second strain gauges 41 to 44 can be made uniform. The configuration is not limited to the above, and the first strain gauges 31 to 34 and the second strain gauges 41 to 44 may be formed into a plate shape, a sheet shape, or a film shape and bonded to each other.

The first distortion gauges 31 to 34 are arranged so as to form a bridge circuit for detecting a force component in a predetermined direction by four positions symmetrical with each other in each beam portion 11e. Similarly, the second strain gauges 41 to 44 are arranged so as to form a bridge circuit for detecting a force component in a predetermined direction by four positions symmetrical with each other in each beam portion 12e. As a method for constructing these bridge circuits, known techniques such as the above-mentioned Patent Document 1 can be applied.

In the present embodiment, the force component Fx in the X-axis direction, the force component Fy in the Y-axis direction, the force component Fz in the Z-axis direction, and the circumference of the X-axis are formed between the first strain-causing body 11 and the second strain-causing body 12. An intermediate body 13 made of a material and a shape that can be deformed according to the moment component Mx, the moment component My around the Y axis, and the moment component Mz around the Z axis is arranged. The intermediate 13 can be linearly deformed according to a total of 6 components of the force components Fx, Fy, and Fz in the three axis directions of the X axis, the Y axis, and the Z axis, and the moment components Mx, My, and Mz around the three axes. Structure. According to the present embodiment, by arranging the intermediate body 13, the desired rated capacity can be obtained by arbitrarily setting the material, shape, thickness, and number of the intermediate bodies 13.

As an example, the intermediate body 13, the first strain-causing body 11, and the second strain-causing body 12 have the same shape in a plan view. As an example, the intermediate 13, the first strain 11 and the second strain 12 have the same structure. As a result, the degree of freedom in design can be increased without increasing the types of parts, and productivity is improved. As an example, the intermediate 13, the first strain 11 and the second strain 12 are made of the same material. This makes it easy to manufacture at low cost. The intermediate 13 may be one, and a plurality of intermediates 13 may be laminated. As an example, the intermediate 13 is thicker than the first strained body 11 and thicker than the second strained body 11. As an example, the intermediate 13 is a cast product having a thickness larger than that of the first strained body 11 and a thickness larger than that of the second strained body 11. As a result, the rated capacity as the magnitude of the force that can be measured by the force sensor 1A can be increased. As an example, the intermediate 13 is more rigid than the first straining body 11 and the second straining body 12. As a result, the rated capacity as the magnitude of the force that can be measured by the force sensor 1A can be increased. As an example, by increasing the number of intermediates 13, the rated capacity as the magnitude of the force that can be measured by the force sensor 1A can be increased. By adopting one or more of the above configurations, it is possible to easily manufacture the force sensor 1A according to various specifications. Therefore, the degree of freedom in design is dramatically increased as compared with the conventional structure. In addition, the present invention is not limited to the above structure, and may be produced by a known production method using a known material.

Subsequently, a method of manufacturing the force sensor 1 (1A) will be described below.

In the force sensor 1A of the present embodiment, a plurality of first strain gauges 31 to 34 are arranged on the first main surface 11a of the first strain generating body 11, and a plurality of second strain gauges 41 to 44 are arranged on the first main surface 11a. It has a strain gauge disposing step for disposing on the second main surface 12a of the distorted body 12. Further, after the strain gauge disposing step, the first strain body 11 in which the first strain gauges 31 to 34 are arranged and the second strain body 12 in which the second strain gauges 41 to 44 are arranged are placed. The first main surface 11a and the second main surface 12a are connected and fixed so as to face outward or inward to form an integral structure. In the assembly step, as an example, an intermediate body 13 having a higher rigidity than the first strain-generating body 11 and the second strain-causing body 12 is arranged between the first strain-causing body 11 and the second strain-causing body 12. ..

As a preliminary step of the strain gauge disposing step, insulating layers are provided on the first main surface 11a of the first strain 11 and the second main surface 12a of the second strain 12. As an example, an insulating layer is provided on one side of the plate-shaped body, and then the first strain-generating body 11 and the second strain-causing body 12 are cut out, respectively. As an example, the first strain-generating body 11 and the second strain-causing body 12 are cut out, respectively, and then insulating layers are provided on the first main surface 11a and the second main surface 12a, respectively.

In the strain gauge disposing step, the first strain gauges 31 to 34 are arranged so as to form a bridge circuit for detecting a force component in a predetermined direction by four positions symmetrical with each other in each beam portion 11e. .. Similarly, the second strain gauges 41 to 44 are arranged so as to form a bridge circuit for detecting a force component in a predetermined direction by four positions symmetrical with each other in each beam portion 12e. As a method for constructing these bridge circuits, the above-mentioned technique of Patent Document 1 can be applied.

In the strain gauge disposing step, when disposing the first strain gauges 31 to 34 and the second strain gauges 41 to 44, as an example, a sputter film or a vapor deposition film of the same material is simultaneously formed. Alternatively, when arranging the first strain gauges 31 to 34 and the second strain gauges 41 to 44, as an example, a sputter film or a vapor-deposited film of the same material is continuously formed. As an example, the first strain gauges 31 to 34 and the second strain gauges 41 to 44 are provided on the surface (one side) of the plate-shaped body provided with the insulating layer, and then the first strain 11 and the second strain are generated. Cut out each of the body 12. As an example, the first strain-causing body 11 and the second strain-causing body 12 are cut out, respectively, and insulating layers are provided on the first main surface 11a and the second main surface 12a, respectively, and then the first strain gauges 31 to 34 and Second strain gauges 41 to 44 are provided.

Generally, in a sputtering apparatus or a vacuum vapor deposition apparatus, it is necessary to strictly control the processing conditions in order to maintain the reproducibility of the film thickness. According to this embodiment, it is possible to easily match the manufacturing conditions when the first strain gauges 31 to 34 are arranged and the manufacturing conditions when the second strain gauges 41 to 44 are arranged. Therefore, the symmetry can be maintained, the productivity is improved, and the manufacturing variation can be suppressed as much as possible. The structure is not limited to the above, and the plate-shaped, sheet-shaped, or film-shaped first strain gauges 31 to 34 and the second strain gauges 41 to 44 may be bonded by a known manufacturing method, respectively.

(Second Embodiment)
The force sensor 1B of the second embodiment shown in FIG. 5 is an example of a structure having no intermediate body 13. In the second embodiment, the differences from the first embodiment will be mainly described.

In the present embodiment, the first straining body 11 and the second straining body 12 are the third main surface 11b on the opposite side of the first main surface 11a of the first straining body 11 and the second straining body 12. In this configuration, the fourth main surface 12b on the opposite side of the second main surface 12a is fitted to each other outward or inward. According to this configuration, the number of parts can be reduced and the overall thickness can be reduced.

In the above example, the first strain-causing body 11 and the second strain-causing body 12 have been described as having a circular shape in a plan view, but the present invention is not limited to this, and a case where a square shape or a polygonal shape is formed in a plan view. There is. As the first straining body 11 and the second straining body 12, known straining body shapes such as a so-called Y-shaped straining body in a plan view and a so-called cross-shaped straining body in a plan view can be applied.

In the above-mentioned example in which the intermediate body 13 is provided, the intermediate body 13, the first strain-causing body 11 and the second strain-causing body 12 have the same shape in a plan view. Depending on the situation, the intermediate body 13 may have a shape different from that of the first strain-generating body 11 and the second strain-causing body 12. As the intermediate body 13, known strain-causing body shapes such as a so-called Y-shaped strain-causing body in a plan view and a so-called cross-shaped strain-generating body in a plan view can be applied to the intermediate.

The processing methods of the first strain-causing body 11, the second strain-causing body 12, and the intermediate body 13 are not limited to cutting, laser machining, electric discharge machining, or a combination of these, but also etching, die-casting, press working, and 3D. Known processing technologies such as printer technology can be applied. As described above, the present invention is not limited to the above-described embodiment.

1, 1A, 1B Force sensor 11 1st strain generator, 11a 1st main surface, 11b 3rd main surface, 11c receiving part, 11d fixed part, 11e beam part, 11f arm part, 11g flexure part 12 2nd Distortion body, 12a 2nd main surface, 12b 4th main surface, 12c receiving part, 12d fixed part, 12e beam part, 12f arm part, 12g flexure part 13 Intermediate 14 Table 15 Base 21 1st bridge circuit (Fz) , Mx, My detection bridge circuit)
22 Second bridge circuit (Fx, Fy, Mz detection bridge circuit)
31-34 First strain gauge 41-44 Second strain gauge P1 Central axis

Claims (5)

A first strain body having a first main surface on which a plurality of first strain gauges are arranged and a second strain body having a second main surface on which a plurality of second strain gauges are arranged are provided.
The first strain-generating body and the second strain-causing body are force sensor characterized in that the first main surface and the second main surface are connected and fixed to each other outward or inward to each other. .. The force sensor according to claim 1, wherein the first strain-causing body and the second strain-causing body have the same structure. The force sensor according to claim 1 or 2, wherein the first strain-causing body and the second strain-causing body are made of metallic glass. Between the first strain-causing body and the second strain-causing body, a force component in the X-axis direction, a force component in the Y-axis direction, a force component in the Z-axis direction, a moment component around the X-axis, and a force component around the Y-axis. The force sensor according to any one of claims 1 to 3, wherein an intermediate body made of a material and a shape that can be deformed according to a moment component and a moment component around the Z axis is arranged. The first strain-generating body and the second strain-causing body are connected to a receiving portion located on a central axis, a fixing portion fixed to the receiving portion, the receiving portion, and the fixing portion. Each has a beam part to do
The first strain gauge and the second strain gauge are respectively arranged so as to form a bridge circuit for detecting a force component in a predetermined direction by four positions symmetrical with each other in the beam portion. The force sensor according to any one of claims 1 to 4, wherein the force sensor according to any one of claims 1 to 4.

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