JP2018205141A - Force sensor - Google Patents

Abstract

To provide a force sensor constituted in such a manner that prevention of the positional deviation of a strain gauge and improvement of the productivity of the force sensor are made compatible.SOLUTION: A force sensor 1 is equipped with: a strain body 2 which has three or more beam portions 20 provided at positions rotationally symmetric with respect to a central axis P1; and a plurality of strain gauges 41 to 48 provided on an outside surface 20a of the beam portion 20. The strain body 2 has a power receiving portion 12 positioned on the center axis P1, and a fixing portion 19 fixed to the power receiving portion 12 through the beam portion 20. The beam portion 20 has an arm portion 14 coupled to the power receiving portion 12, and flexure portions 16 and 18 respectively coupled to both sides of the arm portion 14 in a direction intersecting an extending direction of the arm portion 14. The plurality of strain gauges 41 to 48 are provided only on the outside surface 20a adjacent to an outer circumferential surface 19f of the fixing portion 19.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a technique effective when applied to a strain gauge type force sensor.

  Since the force sensor can detect the force and moment received by the force receiving portion with high accuracy, it is used for advanced control of measuring instruments, industrial robots, and the like.

  In the conventional 6-axis force sensor, strain gauges are provided on four surfaces (for example, an upper surface, a lower surface, a right side surface, and a left side surface) of the arm portion of the strain generating body. For this reason, a large number of strain gauges are provided, and wiring for these strain gauges becomes very complicated, which is expensive.

  Therefore, the inventors of the present application have proposed a force sensor having a configuration in which strain gauges are provided in a predetermined arrangement on two opposing surfaces of the arm portion of the strain generating body (see Patent Document 1: Japanese Patent Laid-Open No. 2006-70673).

JP 2006-70673 A

  The force sensor described in Patent Document 1 has a structure in which strain gauges are provided in a predetermined arrangement on two surfaces facing each other in an arm portion of a strain generating body. Here, as in the force sensor described in Patent Document 1, for example, when a bridge circuit is configured by strain gauges provided in a predetermined arrangement on two surfaces of the upper surface and the lower surface of the arm unit, It is important to secure the detection accuracy that the strain gauge is provided symmetrically (coincided in plan view). In other words, in order to ensure detection accuracy, high-precision position adjustment is performed so that a plurality of strain gauges attached to the upper surface and a plurality of strain gauges attached to the lower surface are attached to positions that are plane-symmetrical. Is required. However, if the position adjustment with high accuracy is performed, the productivity is lowered. Therefore, further prevention of displacement of the strain gauge and improvement in productivity are desired.

  The present invention has been made in view of the above circumstances, and prevents misalignment of the strain gauge by eliminating the misalignment caused by providing a plurality of strain gauges in a predetermined arrangement on two surfaces facing each other in the arm portion of the strain generating body. An object of the present invention is to provide a force sensor having a configuration capable of improving productivity.

  As an embodiment, the above-described problem is solved by a solution as disclosed below.

  The disclosed force sensor includes a strain generating body having three or more beam portions provided at rotationally symmetric positions with respect to a central axis, and a plurality of strain gauges provided on an outer surface of the beam portion. The strain body includes a force receiving portion located on the central axis, and a fixing portion fixed to the force receiving portion via the beam portion, and the beam portion includes: An arm portion connected to the force receiving portion, and flexure portions respectively connected to both sides of the arm portion in a direction crossing the extending direction of the arm portion, and the plurality of strain gauges are fixed It is provided only on the outer surface at a position adjacent to the outer peripheral surface of the part.

  According to the disclosed force sensor, since a plurality of strain gauges are provided only on the outer surface of the beam portion adjacent to the outer peripheral surface of the fixed portion, the strain gauges are provided in a predetermined arrangement on two surfaces facing each other in the arm portion. In this configuration, the positional deviation caused by the problem is eliminated. Therefore, the displacement of the strain gauge can be prevented. Furthermore, by providing a plurality of strain gauges only on the outer surface, the number of strain gauges arranged is halved, so that the productivity is greatly improved and the cost is greatly reduced.

FIG. 1 is a perspective view showing an example of a force sensor according to the first embodiment of the present invention. FIG. 2A is a plan view of the force sensor of the above embodiment, and FIG. 2B is a front view of FIG. FIG. 3 is a perspective view showing an example of a force sensor according to the second embodiment of the present invention. FIG. 4A is a plan view of the force sensor of the above embodiment, and FIG. 4B is a front view of FIG. 4A. FIG. 5 is a perspective view showing an example of a force sensor according to the third embodiment of the present invention. 6A is a plan view of the force sensor of the above embodiment, and FIG. 6B is a front view of FIG. 6A. FIG. 7 is a bottom view of the force sensor of the embodiment. FIG. 8 is a perspective view showing an example of a force sensor according to the fourth embodiment of the present invention. FIG. 9A is a plan view of the force sensor of the above embodiment, and FIG. 9B is a front view of FIG. 9A. 10A is an explanatory diagram of a bridge circuit for detecting Fz, Mx, and My included in the force sensor according to the present invention, and FIG. 10B illustrates Fx, Fy, Mz included in the force sensor according to the present invention. It is explanatory drawing of the bridge circuit for a detection.

  The force sensor 1 according to the first to fourth embodiments described below includes force components Fx, Fy, three-axis directions of a three-dimensional space orthogonal coordinate system (x-axis, y-axis, z-axis). This is a 6-axis force sensor that can simultaneously detect a total of 6 components including Fz and moment components Mx, My, and Mz about the three axes.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described in detail with reference to the drawings. The force sensor 1 (1A) of the first embodiment is an example in which three beam portions 20 are provided at positions that are rotationally symmetric with respect to the central axis P1, and is an example of a basic structure.

  FIG. 1 is a perspective view (schematic diagram) showing an example of a force sensor 1A according to the present embodiment, FIG. 2 (A) is a plan view (schematic diagram) thereof, and FIG. 2 (B) is a front view thereof. It is a figure (schematic diagram) (a signal processing part and wiring are not shown). Note that components having the same function are denoted by the same reference symbols throughout the drawings for describing the embodiments, and the repetitive description thereof may be omitted.

  As shown in FIGS. 1, 2A, and 2B, the force sensor 1A includes a plurality of strain gauges 41 to 48 and an outer surface 20a on which the plurality of strain gauges 41 to 48 are provided. And a distortion body 2. The strain body 2 of the present embodiment is a plate-like body, and includes a force receiving portion 12 that is located on the central axis P1, a fixing portion 19 that is fixed to the force receiving portion 12, and a force receiving portion 12 that is fixed. And a beam portion 20 that connects the portion 19. Three beam portions 20 are arranged at positions that are rotationally symmetric with respect to the central axis P <b> 1 of the strain body 2. Similarly, three fixing portions 19 are arranged. The strain body 2 has a shape that is rotationally symmetric with respect to its central axis P1.

  In FIG. 1 and FIG. 2A, a portion surrounded by a broken line indicates one of the beam portions 20. The beam unit 20 includes an arm unit 14 coupled to the force receiving unit 12 and a flexure unit 16 coupled to both sides of the arm unit 14 in the X-axis direction intersecting the Y-axis direction that is the extending direction of the arm unit 14. , 18. The flexure portion 16 and the flexure portion 18 are provided at positions that are line-symmetric with respect to the central axis P1 of the strain body 2. The force receiving portion 12, the beam portion 20, and the fixing portion 19 are an integral structure. The size of each part of the strain generating body 2 is set so that the beam part 20 can be regarded as an elastic body when the force receiving part 12 and the fixing part 19 are regarded as rigid bodies.

  As shown in FIG. 2A, the width dimension of the flexure portion 16 (18) in the Y-axis direction is set to be smaller than the width dimension of the arm portion 14 in the X-axis direction. As shown in FIG. 2B, the height dimension of the flexure portion 16 (18) in the Z-axis direction is set larger than the width dimension of the flexure portions 16 and 18 in the Y-axis direction.

  The plurality of strain gauges 41 to 48 are provided on the beam portion 20, and are provided only on the outer surface 20 a at a position adjacent to the outer peripheral surface 19 f of the fixed portion 19.

  The outer side surface 20a is larger in size than the surface of the beam portion 20 in the direction of the central axis P1. Further, the outer surface 20a has no shielding object. Therefore, the outer surface 20a is easy to dispose a plurality of strain gauges 41 to 48, and can easily cope with the downsizing of the strain generating body 2.

  The strain body 2 is obtained, for example, by forming a through-hole or the like in a spring material such as an aluminum alloy, alloy steel, stainless steel using an NC (Numerical Control) processing machine. Here, for example, the plate 2 having a circular outer shape is subjected to cutting processing, laser processing, electric discharge processing, or a combination processing thereof, and the like, and the strain generating body 2 including the force receiving portion 12, the fixing portion 19, and the beam portion 20. Is formed. In the strain body 2, spaces (penetrating portions) for partitioning the force receiving portion 12, the fixing portion 19, and the beam portion 20 are formed. In the present embodiment, an outer peripheral surface of the strain generating body 2 is constituted by the outer surface 20a located away from the central axis P1 among the radial side surfaces of the beam portion 20 and the outer peripheral surface 19f of the fixing portion 19. Yes. The force sensor 1A is assembled to, for example, an industrial robot through a bolt or the like through a through hole 19a formed in the fixed portion 19.

  In the force sensor 1 </ b> A, when a force is applied to the force receiving portion 12 disposed on the central axis P <b> 1 of the strain body 2, distortion due to stress (bending, shearing, torsion) is generated in the beam portion 20. For example, a bending (deflection) strain is generated in the radial direction (extending direction) of the beam portion 20 and a direction orthogonal thereto, a shear strain is generated in a direction of 45 ° with respect to the radial direction of the beam portion 20, and the beam portion 20 Torsional distortion occurs in the circumferential direction. In the force sensor 1 </ b> A, when detecting these strains, a plurality of strain gauges 41 to 48 are provided only on the outer surface 20 a of the beam portion 20. The outer side surface 20 a is formed in the extending direction of the arm portion 14. Further, the outer surface 20a is formed at a position away from the central axis P1 in the radial side surface of the beam portion 20.

  As the strain gauges 41 to 48, for example, a wiring pattern of a metal thin film (such as a metal foil) of a Cu (copper) -Ni (nickel) -based alloy or a Ni-Cr (chromium) -based alloy is used as a flexible polyimide, What was covered with the epoxy resin film can be used. Such strain gauges 41 to 48 are attached to the outer surface 20a of the beam portion 20 using an adhesive, and detect and detect strain from a resistance change when the metal thin film is deformed due to the distortion of the beam portion 20. can do. Further, as the strain gauges 41 to 48, a semiconductor strain gauge using a semiconductor thin film can also be used. The strain gauges 41 to 48 may directly form a metal thin film gauge on the outer surface 20a of the beam portion 20 by using a sputtering method or a vacuum deposition method.

  According to the present embodiment, since the plurality of strain gauges 41 to 48 are provided only on the outer surface 20a adjacent to the outer peripheral surface 19f of the fixed portion 19, a plurality of strains are arranged in a predetermined arrangement on the two surfaces facing each other in the arm portion. It becomes the structure which eliminated the position shift resulting from providing a gauge. Therefore, the displacement of the strain gauge can be prevented. Further, the configuration in which the plurality of strain gauges 41 to 48 are provided only on the outer surface 20a reduces the number of strain gauges to be halved, so that the productivity is greatly improved and the cost is greatly reduced. Furthermore, since there is no shielding on the outer surface 20a, it is easy to dispose a plurality of strain gauges 41 to 48 by directly forming a metal thin film gauge using a sputtering method or a vacuum deposition method. By using a sputtering method or a vacuum evaporation method, productivity is dramatically improved. Since the outer surface 20a is larger in size than the surface of the beam portion 20 in the direction of the central axis P1, it is easy to dispose a plurality of strain gauges 41 to 48 and to reduce the size of the strain generating body 2. Easy to handle.

  The plurality of strain gauges 41 to 48 are provided at positions closer to the central axis P <b> 1 than the outer peripheral surface 19 f of the fixed portion 19. Thereby, when handling the force sensor 1A, for example, by gripping the outer peripheral surface 19f provided at a position farther from the central axis P1 than the plurality of strain gauges 41-48, the plurality of strain gauges 41-41. It is possible to prevent accidental contact with 48.

  The force sensor 1A of the present embodiment has a force component Fx in the X-axis direction, a force component Fy in the Y-axis direction, a force component Fy in the Y-axis direction, and the Z-axis when the center axis P1 and the Z-axis coincide with each other. A force component Fz in the direction, a moment component Mx around the X axis, a moment component My around the Y axis, and a moment component Mz around the Z axis are detected. The force sensor 1A includes a first bridge circuit 21 that detects Fz, Mx, and My shown in FIG. 10A, and a second bridge circuit 22 that detects Fx, Fy, and Mz shown in FIG. 10B. And have. In the present embodiment, a first bridge circuit 21 and a second bridge circuit 22 including strain gauges 41 to 48 are provided in each of the three beam units 20 in order to detect and detect force components in six axial directions. .

  The first bridge circuit 21 that detects Fz, Mx, and My includes a first strain gauge 41, a second strain gauge 42, a third strain gauge 43, and a fourth strain gauge 44. The second bridge circuit 22 that detects Fx, Fy, and Mz includes a fifth strain gauge 45, a sixth strain gauge 46, a seventh strain gauge 47, and an eighth strain gauge 48. However, it is not limited to this configuration.

  The plurality of strain gauges 41 to 48 are provided on the outer side surface 20a by being divided into two in the arrangement area 16a corresponding to the flexure part 16 on a one-to-one basis and in the arrangement area 18a corresponding to the flexure part 18 on a one-on-one basis. . Thereby, the detection power of the distortion generated from the pair of flexure portions 16 and 18 can be enhanced.

  As shown in FIG. 2B, a first strain gauge 41 and a third strain gauge 43, a second strain gauge 42 and a fourth strain gauge 44, a fifth strain gauge 45 and a seventh strain gauge. 47 and the sixth strain gauge 46 and the eighth strain gauge 48 are provided at positions symmetrical with respect to the central axis P1. According to this, the resistance values of the strain gauges 41 to 48 having the line symmetric positional relationship can be similarly changed with respect to the force component Fz in the Z-axis direction. And since the 1st bridge circuit 21 and the 2nd bridge circuit 22 are comprised, when force is not acting on the force receiving part 12, it can be canceled so that an unnecessary output signal may not arise.

  The first strain gauge 41 and the second strain gauge 42, the third strain gauge 43 and the fourth strain gauge 44, the fifth strain gauge 45 and the seventh strain gauge 47, and the sixth strain gauge 46. And the eighth strain gauge 48 are provided at positions symmetrical with respect to the center line P2 in the direction orthogonal to the center axis 12 among the center lines of the outer surface 20a. According to this, the resistance values of the strain gauges 41 to 48 having the line-symmetrical positional relationship can be similarly changed with respect to the force component Fx in the X-axis direction. And since the 1st bridge circuit 21 and the 2nd bridge circuit 22 are comprised, when force is not acting on the force receiving part 12, it can be canceled so that an unnecessary output signal may not arise.

  The first strain gauge 41, the second strain gauge 42, the third strain gauge 43, and the fourth strain gauge 44 all have a strain detection direction of 45 ° with respect to the extending direction of the arm portion 14. (Or 135 ° direction).

  The fifth strain gauge 45, the sixth strain gauge 46, the seventh strain gauge 47, and the eighth strain gauge 48 are all arranged so that the strain detection direction coincides with the extending direction of the arm portion 14. Is done.

  As shown in FIG. 10 (A), when the input signal BV is applied to the first bridge circuit 21, the output signal Vo is changed to the non-equilibrium state due to the change in the resistance values of the strain gauges 41 to 44. Change. In the force sensor 1A, stress is generated in the beam unit 20, but since the first bridge circuit 21 is configured, an interference removing function and a temperature guarantee function are provided, and for example, when detecting stress due to bending (deflection). The stress due to shear is canceled.

  As shown in FIG. 10B, when the input signal BV is applied to the second bridge circuit 22, the output signal Vo is output when the strain gauges 45 to 48 are in an unbalanced state due to a change in resistance value. Change. In the force sensor 1A, a stress is generated in the beam unit 20. However, since the second bridge circuit 22 is configured, an interference removing function and a temperature guarantee function are provided. For example, when detecting stress due to shearing, bending ( The stress due to bending is canceled.

  When the central axis P1 and the Z axis are matched, the force component Fz in the Z-axis direction of the force received by the force receiving portion 12 of the strain body 2 of the force sensor 1A, the moment component Mx around the X axis, and Y The detection results obtained by detecting the moment component My around the axis by the first bridge circuit 21 are shown in Table 1 below.

  In Table 1, “+” indicates that the resistance value of the strain gauges 41 to 44 increases, “−” indicates that the resistance value decreases, and “0” indicates that the resistance value is small or 0. The output signal Vo is “1” when there is a bridge output (unbalanced output), and “0” when the value is 0 or small.

  According to Table 1, the first bridge circuit 21 confirms increase and decrease in the resistance values of the strain gauges 41 to 44 in the force component Fz in the Z-axis direction, the moment component Mx around the X axis, and the moment component My around the Y axis. , Fz, Mx, My can be detected.

  Next, the force component Fx in the X-axis direction, the force component Fy in the Y-axis direction, and the moment component Mz around the Z-axis of the force received by the force receiving portion 12 of the strain body 2 of the force sensor 1A The detection results detected by the bridge circuit 22 are shown in Table 2 below.

  In Table 2, “+” indicates that the resistance value of the strain gauges 45 to 48 increases, “−” indicates that the resistance value decreases, and “0” indicates that the resistance value is small or 0. The output signal Vo is “1” when there is a bridge output (unbalanced output), and “0” when the value is 0 or small.

  According to Table 2, the second bridge circuit 22 is confirmed to increase or decrease the resistance values of the strain gauges 41 to 44 in the force component Fx in the X-axis direction, the force component Fy in the Y-axis direction, and the moment component Mz around the Z-axis. , Fx, Fy, and Mz can be detected.

  According to Tables 1 and 2, components that are difficult to detect in the second bridge circuit 22 (Fz, Mx, My) are detected by the first bridge circuit 21, and components that are difficult to detect in the first bridge circuit 21 (Fx , Fy, Mz) are detected by the second bridge circuit 22. By configuring the first bridge circuit 21 and the second bridge circuit 22 in this way, the force components in the six axis directions can be separated and detected.

  Here, when the strain gauges 41 to 48 are set as one set, the three sets are arrangement configurations that are rotationally symmetric with respect to the central axis P1. This is because the way of assembling the bridge circuits of the strain gauges 41 to 48 on each outer surface 20a can be made the same, so that the workability when the strain gauges 41 to 48 are provided on each outer surface 20a is good, and the output in the initial state is zero. This is because adjustment work such as zero adjustment and sensitivity adjustment for setting the output level to an appropriate value is facilitated. However, it is not limited to this configuration.

(Second Embodiment)
The force sensor 1 (1B) of the second embodiment is an example in which three beam portions 20 are provided at positions that are rotationally symmetric with respect to the central axis P1, and has a structure in which the fixing portion 19 is reinforced. It is an example.

  3 is a perspective view (schematic diagram) showing an example of a force sensor 1B according to the present embodiment, FIG. 4 (A) is a plan view (schematic diagram) thereof, and FIG. 4 (B) is a front view thereof. It is a figure (schematic diagram) (a signal processing part and wiring are not shown). The second embodiment will be described with a focus on differences from the first embodiment.

  In the present embodiment, for example, a cylindrical body is subjected to cutting, laser processing, electric discharge machining, or a combined machining thereof, and the like, and a starting member including the force receiving portion 12, the fixing portion 19, the connecting portion 9, and the beam portion 20 is formed. The distortion body 2 is molded. In the strain body 2, spaces (penetrating portions) for partitioning the force receiving portion 12, the fixing portion 19, the connecting portion 9, and the beam portion 20 are formed.

  In the present embodiment, adjacent fixing portions 19 are connected by a connecting portion 9. The force receiving portion 12, the beam portion 20, the fixing portion 19, and the connecting portion 9 are an integral structure. With this configuration, the strain body 2 is reinforced by the fixing portion 19 and the connecting portion 9, and thus has a robust structure.

  The connecting portion 9 is provided at a position adjacent to the outer side surface 20a located at a position away from the central axis P1 among the radial side surfaces of the beam portion 20. Two connecting portions 9 and two fixing portions 19 are provided at a position surrounding the outer side surface 20a. And the outer peripheral surface 19f of the fixing | fixed part 19 and the outer peripheral surface 19g of the connection part 9 comprise the outer peripheral part of the strain body 2. FIG. Thus, the outer peripheral surface 19f and the outer peripheral surface 19g surround the outer surface 20a.

  The plurality of strain gauges 41 to 48 are provided at a position closer to the central axis P1 than the outer peripheral surface 19f, and are provided at a position closer to the central axis P1 than the outer peripheral surface 19g. Thereby, when handling the force sensor 1B, for example, either one or both of the outer peripheral surface 19f and the outer peripheral surface 19g provided at positions farther from the central axis P1 than the plurality of strain gauges 41 to 48 are gripped. By doing so, it can prevent contacting with the some strain gauges 41-48 accidentally. Further, since the plurality of strain gauges 41 to 48 are protected by being provided at a position closer to the central axis P1 than the outer peripheral portion of the strain generating body 2 constituted by the outer peripheral surface 19f and the outer peripheral surface 19g. It is possible to prevent erroneous contact with the strain gauges 41 to 48.

  Slits 19b are formed on both surfaces of the flexure portions 16, 18 in the direction of the central axis P1. Since both surfaces of the flexure portions 16 and 18 in the direction of the central axis P1 and the connecting portion 9 are separated by the slit 19b, the flexure portions 16 and 18 are easily elastically deformed. The slit 19b extends in the X-axis direction and has a groove shape with a predetermined depth. Because the slit 19b causes both surfaces of the flexure portions 16 and 18 in the direction orthogonal to the central axis P1 and the fixed portion 19 to be loosely coupled with each other, the flexure portions 16 and 18 are easily elastically deformed. It has become. Therefore, the strain gauges 41 to 48 have a structure in which strain is easily detected.

  Further, since the force receiving portion 12 and the arm portion 14 are protected by the fixing portion 19 and the connecting portion 9, a robust structure is obtained.

(Third embodiment)
The force sensor 1 (1C) of the third embodiment is an example in which three beam portions 20 are provided at positions that are rotationally symmetric with respect to the central axis P1, and the table 6, the strain body 2, This is an example of a structure in which the base 8 is integrated.

  FIG. 5 is a perspective view (schematic diagram) showing an example of a force sensor 1C according to the present embodiment, FIG. 6 (A) is a plan view (schematic diagram) thereof, and FIG. 6 (B) is a front view thereof. FIG. 7 is a bottom view (schematic diagram) thereof (signal processing unit and wiring are not shown). In the third embodiment, a description will be given focusing on differences from the already described embodiments.

  In this embodiment, for example, a strain generating body 2 having a force receiving portion 12, a fixing portion 19, and a beam portion 20 by subjecting a cylindrical body to cutting, laser processing, electric discharge machining, or a combination thereof, The table 6 and the base 8 are integrally formed. In addition, spaces (penetrating portions) for partitioning the force receiving portion 12, the fixing portion 19, the beam portion 20, the table 6, and the base 8 are formed.

  In the present embodiment, the table 6 is disposed on the central axis P <b> 1 and is connected to the force receiving portion 12. The base 8 is disposed at a position opposite to the table 6 on the central axis P1, and is connected to a coupling portion 19d extending from the fixed portion 19 in the direction of the central axis P1. The table 6, the force receiving portion 12, the beam portion 20, the fixing portion 19, the coupling portion 19d, and the base 8 are an integral structure.

  With this configuration, the number of steps for incorporating the strain generating body 2 into the table 6 and the base 8 can be reduced. Further, since the table 6, the strain body 2 and the base 8 are an integral structure, parts such as bolts and screws for assembling the strain body 2 and the table 6, and the strain body 2 and the base 8, respectively. Can be reduced. Further, the assembly error due to the component assembly is eliminated, so that the performance is improved. And such force sensor 1C becomes easy to handle. In addition, the strain body 2 is protected by the table 6 and the base 8, and a robust structure is obtained.

  A mounting hole 6a for attaching a measuring jig or the like with a bolt or the like is provided on a surface of the table 6 in the Z-axis direction opposite to the force receiving portion 12 at a position that is rotationally symmetric with respect to the central axis P1. Four pin holes 6b are formed at predetermined intervals, and four pin holes 6b for attaching positioning pins such as measuring jigs are formed at positions orthogonal to the central axis P1.

  Of the surface in the Z-axis direction of the base 8, four mounting holes 8 a are formed at predetermined intervals on the surface opposite to the force receiving portion 12 at a position that is rotationally symmetric with respect to the central axis P <b> 1. The attachment hole 8a is used to attach the force sensor 1C to a housing or the like of a measuring device with a bolt or the like.

  The plurality of strain gauges 41 to 48 are provided at a position closer to the central axis P <b> 1 than the outer peripheral surface of the table 6, and are provided at a position closer to the central axis P <b> 1 than the outer peripheral surface of the base 8. Thereby, when handling force sensor 1C, it can prevent contacting with a plurality of distortion gauges 41-48 accidentally. Further, since the plurality of strain gauges 41 to 48 are protected by the table 6 and the base 8, it is possible to prevent erroneous contact with the plurality of strain gauges 41 to 48.

  Since spaces are formed on both surfaces of the flexure portions 16 and 18 in the direction of the central axis P1, the flexure portions 16 and 18 are easily elastically deformed. Therefore, the strain gauges 41 to 48 have a structure in which strain is easily detected.

  Moreover, since the strain body 2 is protected by the table 6 and the base 8, it has a robust structure.

  As shown in FIG. 6B, the force receiving portion 12 of the strain body 2 is connected to the table 6. As shown in FIG. 7, the force receiving portion 12 of the strain body 2 is separated from the base 8. A coupling portion 19 d is formed on the fixing portion 19 of the strain body 2. The fixing portion 19 of the strain generating body 2 is connected to the base 8 via a coupling portion 19d. Here, the force receiving portion 12 has a regular hexagonal shape in plan view.

(Fourth embodiment)
In the first to third embodiments described above, the strain generating body 2 is an example in the case of having three beam portions 20, and an example of a so-called Y beam structure has been shown. The force sensor 1 (1D) of the fourth embodiment is an example in which the strain generating body 2 has four beam portions 20, and is an example of a so-called X beam structure.

  FIG. 8 is a perspective view (schematic diagram) showing an example of a force sensor 1D according to the present embodiment, FIG. 9A is a plan view thereof (schematic diagram), and FIG. 9B is a front view thereof. It is a figure (schematic diagram) (a signal processing part and wiring are not shown). In the fourth embodiment, a description will be given focusing on differences from the already described embodiments.

  In the present embodiment, the strain body 2 is formed by, for example, subjecting a prismatic element to cutting, laser processing, electric discharge machining, or a combination thereof. Four beam portions 20 are arranged at rotationally symmetric positions with respect to the central axis P1 of the force receiving portion 12 in the Z-axis direction.

  In the present embodiment, when the Z-axis direction is upward, the upper portion of the force receiving portion 12 protrudes from the upper surfaces of the arm portion 14 and the fixing portion 19. As a result, it is easy to attach a measuring jig or the like to the mounting hole 12a formed in the force receiving portion 12 with a bolt or the like in a state where the bolt is inserted into the through hole 19a formed in the fixing portion 19 or the like. Even if the measuring jig or the like is greatly displaced, it does not contact the fixed portion 19. A notch portion 19e is formed at the lower portion of the fixed portion 19. As a result, the flexure portions 16 and 18 do not come into contact with the mounting table or the like in a state where the bolts or the like are attached to the mounting table or the like through the through holes 19a formed in the fixing unit 19. Here, the strain body 2 has a square shape in plan view. In addition, it is not limited to this example, The strain body 2 can be made into circular shape by planar view.

  The present invention is not limited to the embodiments described above, and various modifications can be made without departing from the present invention. For example, in the above-described embodiment, the case where the present invention is applied to a 6-axis force sensor has been described. The present invention is not limited to this, and the present invention can also be applied to a force sensor with a reduced number of axes such as one axis and three axes. In the above-described embodiment, an example in which three or four beam units 20 are provided has been described. Not only this but the structure which has five or more beam parts 20 can be used. The strain generating body 2 is not limited to the above-described cutting processing, laser processing, electric discharge processing, or a combination processing thereof, and a known processing technology such as an etching method, a die casting method, a press processing, or a 3D printer technology can be applied.

  For example, when a plurality of strain gauges 41 to 48 constituting a bridge circuit are provided in the beam portion, a predetermined number of strain gauges connected in advance to constitute a bridge circuit are pasted as a strain gauge ASSY (assembly) formed with a bridge. Can be attached.

  In the arrangement of the strain gauges 41 to 48 described above, the outer surface 20a is a position where it is easier to use the sputtering method or the vacuum evaporation method than the inner surface, and the sputtering method or the vacuum evaporation method is used. By forming the strain gauges 41 to 48 at the same time, the productivity is remarkably improved, and it is also possible to prevent displacement of the strain gauges from each other by the simultaneous formation.

DESCRIPTION OF SYMBOLS 1, 1A, 1B, 1C, 1D Force sensor 2 Strain body 6 Table 8 Base 9 Connection part 12 Force receiving part 14 Arm part 16, 18 Flexure part 16a, 18a Arrangement area 19 Fixing part 19f Outer peripheral surface 19g Connection part 20 Beam part 20a Outer side surface 21 First bridge circuit (Fz, Mx, My detection bridge circuit)
22 Second bridge circuit (Fx, Fy, Mz detection bridge circuit)
41-48 strain gauge P1 center axis

Claims (8)

A strain-generating body having three or more beam portions provided at rotationally symmetric positions with respect to the central axis, and a plurality of strain gauges provided on the outer surface of the beam portion,
The strain body includes a force receiving portion located on the central axis, and a fixing portion fixed to the force receiving portion via the beam portion,
The beam portion includes an arm portion coupled to the force receiving portion, and a flexure portion coupled to both sides of the arm portion in a direction intersecting the extending direction of the arm portion,
The plurality of strain gauges are provided only on the outer surface at a position adjacent to the outer peripheral surface of the fixed portion. 2. The force sensor according to claim 1, wherein the plurality of strain gauges are respectively provided in a pair of arrangement areas that correspond one-to-one with the flexure portion. A connecting portion connected to the adjacent fixed portions;
The force sensor according to claim 1, wherein the connecting portion and the fixing portion are provided at a position surrounding the outer surface. A table disposed on the central axis and connected to the force receiving portion; and a base disposed on a position opposite to the table on the central axis and connected to the fixed portion. The force sensor according to claim 1 or 2, characterized in that The table, the strain generating body, and the base are integral structures;
The force sensor according to claim 4. A first bridge circuit that detects a force component Fz in the Z-axis direction, a moment component Mx around the X axis, and a moment component My around the Y axis of the force received by the force receiving portion;
A second bridge circuit that detects a force component Fx in the X-axis direction, a force component Fy in the Y-axis direction, and a moment component Mz around the Z-axis of the force received by the force receiving portion;
The plurality of strain gauges include a first strain gauge, a second strain gauge, a third strain gauge, and a fourth strain gauge constituting the first bridge circuit,
It has a 5th strain gauge, a 6th strain gauge, a 7th strain gauge, and an 8th strain gauge which constitute the 2nd bridge circuit. The force sensor according to item. The first strain gauge, the third strain gauge, the second strain gauge, the fourth strain gauge, the fifth strain gauge, the seventh strain gauge, and the sixth strain gauge. The force sensor according to claim 6, wherein the eighth strain gauge is provided at a position that is line-symmetric with respect to the central axis. The first strain gauge, the second strain gauge, the third strain gauge, the fourth strain gauge, the fifth strain gauge, the seventh strain gauge, and the sixth strain gauge. The said 8th strain gauge is provided in the position which becomes axisymmetric with respect to the centerline of the said outer surface in the direction orthogonal to the said center axis | shaft. Force sensor.

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