JP6664742B2 - Force sensor - Google Patents

Description

  The present invention relates to a technology that is effective when applied to a strain gauge type force sensor.

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

  In a conventional six-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 an arm portion of a flexure element. Therefore, a large number of strain gauges are provided, and the wiring of the strain gauges becomes very complicated, resulting in a high price.

  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 an arm portion of a flexure element (see JP-A-2006-70673).

JP-A-2006-70673

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

  The present invention has been made in view of the above circumstances, and has a configuration in which a displacement caused by providing a plurality of strain gauges in a predetermined arrangement on two opposing surfaces in an arm portion of a strain generating body is eliminated, thereby preventing displacement of the strain gauge. It is an object of the present invention to provide a force sensor having a configuration capable of improving productivity.

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

  The force sensor according to the disclosure includes a strain body having three or more beam portions provided at positions that are rotationally symmetric with respect to a central axis, and a plurality of strain gauges provided on an outer surface of the beam portion. Provided, the strain body has 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, An arm portion connected to a force receiving portion, and flexure portions connected to both sides of the arm portion in a direction intersecting with an extending direction of the arm portion, wherein the plurality of strain gauges are fixed to the plurality of strain gauges. It is provided only on the outer surface at a position adjacent to the outer peripheral surface of the portion.

  According to the force sensor disclosed herein, 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 opposite surfaces of the arm portion. This eliminates the displacement caused by this. 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 to be provided is reduced by half, so that productivity is greatly improved and cost is significantly reduced.

FIG. 1 is a perspective view showing an example of the force sensor according to the first embodiment of the present invention. FIG. 2A is a plan view of the force sensor according to the embodiment, and FIG. 2B is a front view of FIG. 2A. 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 according to the 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. FIG. 6A is a plan view of the force sensor of the embodiment, and FIG. 6B is a front view of FIG. 6A. FIG. 7 is a bottom view of the force sensor according to the embodiment. FIG. 8 is a perspective view showing an example of the force sensor according to the fourth embodiment of the present invention. FIG. 9A is a plan view of the force sensor according to the embodiment, and FIG. 9B is a front view of FIG. 9A. FIG. 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 is a diagram illustrating Fx, Fy, and Mz included in the force sensor according to the present invention. FIG. 4 is an explanatory diagram of a detection bridge circuit.

  The force sensor 1 according to the first to fourth embodiments described below includes force components Fx, Fy, in three-axis directions of a rectangular coordinate system (x-axis, y-axis, z-axis) in a three-dimensional space. This is a six-axis force sensor that can simultaneously detect a total of six components Fz and moment components Mx, My, and Mz around 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 of a case where three beam units 20 are provided at positions 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) (signal processing part and wiring are not shown). In all the drawings for describing the embodiments, members having the same functions are denoted by the same reference numerals, and the repeated 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. A distortion body 2. The flexure element 2 of the present embodiment is a plate-shaped body, and has a force receiving portion 12 located on the central axis P1, a fixing portion 19 fixed to the force receiving portion 12, and a fixing portion with the force receiving portion 12. A beam section 20 for connecting the section 19 with the beam section 20. The three beam portions 20 are arranged at positions that are rotationally symmetric with respect to the central axis P1 of the strain body 2. Similarly, three fixing portions 19 are arranged. The flexure element 2 has a shape that is rotationally symmetric with respect to the center axis P1.

  1 and 2A, a portion surrounded by a broken line indicates one of the beam portions 20. The beam section 20 includes an arm section 14 connected to the force receiving section 12 and a flexure section 16 connected to both sides of the arm section 14 in an X-axis direction intersecting the Y-axis direction in which the arm section 14 extends. , 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 flexure element 2 is set so that the beam section 20 can be regarded as an elastic body when the force receiving section 12 and the fixing section 19 are regarded as rigid bodies.

  As shown in FIG. 2A, the width of the flexure portion 16 (18) in the Y-axis direction is set smaller than the width of the arm portion 14 in the X-axis direction. Then, as shown in FIG. 2B, the height of the flexure portions 16 (18) in the Z-axis direction is set to be larger than the width 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 fixing 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, there is no shielding on the outer side surface 20a. Therefore, the outer side surface 20a is easy to arrange the plurality of strain gauges 41 to 48 and is easy to cope with downsizing of the strain body 2.

  The strain generating element 2 is obtained by, for example, forming a through-hole or the like in a springy material such as an aluminum alloy, an alloy steel, or a stainless steel using an NC (Numerical Control) machine. Here, for example, a plate-like body having a circular outer shape is subjected to cutting, laser machining, electric discharge machining, or a combination 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. Is molded. The strain body 2 has a space (through portion) for partitioning each of the force receiving portion 12, the fixing portion 19, and the beam portion 20. In the present embodiment, the outer peripheral surface of the flexure element 2 is constituted by the outer peripheral surface 20a of the radial side surface of the beam portion 20 which is located away from the central axis P1 and the outer peripheral surface 19f of the fixing portion 19. I have. The force sensor 1A is assembled to, for example, an industrial robot or the like by passing a bolt or the like through a through hole 19a formed in the fixing 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 flexure element 2, strain (bending, shearing, torsion) due to stress (bending, shearing, torsion) occurs in the beam portion 20. For example, bending (deflection) distortion is generated in the radiation direction (extending direction) of the beam portion 20 and a direction orthogonal thereto, shear distortion is generated in a 45 ° direction with respect to the radiation direction of the beam portion 20, and Causes torsional distortion in the circumferential direction. In the force sensor 1 </ b> A, a plurality of strain gauges 41 to 48 are provided only on the outer surface 20 a of the beam unit 20 when detecting these strains. The outer side surface 20a is formed in the direction in which the arm 14 extends. The outer side surface 20a is formed at a position apart from the central axis P1 on 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 may be formed by using a polyimide having flexibility. One covered with an epoxy resin film can be used. Such strain gauges 41 to 48 are attached to the outer surface 20a of the beam unit 20 using an adhesive, and detect and detect distortion from a change in resistance when the metal thin film is deformed due to the distortion of the beam unit 20. can do. Further, as the strain gauges 41 to 48, semiconductor strain gauges using a semiconductor thin film can be used. Further, as the strain gauges 41 to 48, a metal thin film gauge may be directly formed on the outer surface 20a of the beam section 20 using a sputtering method or a vacuum evaporation method.

  According to the present embodiment, since the plurality of strain gauges 41 to 48 are provided only on the outer surface 20a at a position adjacent to the outer peripheral surface 19f of the fixing portion 19, the plurality of strain gauges are arranged in a predetermined arrangement on the two facing surfaces in the arm portion. The configuration is such that the displacement caused by providing the gauge is eliminated. Therefore, the displacement of the strain gauge can be prevented. Further, by providing a plurality of strain gauges 41 to 48 only on the outer side surface 20a, the number of strain gauges to be provided is reduced by half, so that productivity is greatly improved and cost is significantly reduced. Furthermore, since there is no shielding on the outer surface 20a, it is easy to arrange a plurality of strain gauges 41 to 48 by directly forming a metal thin film gauge using a sputtering method or a vacuum evaporation method. By using a sputtering method or a vacuum evaporation method, productivity is significantly 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 arrange the plurality of strain gauges 41 to 48 and to reduce the size of the strain body 2. Easy to respond.

  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 of the fixing 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 to 48, the plurality of strain gauges 41 to 48 can be prevented from being accidentally contacted.

  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, and a Z-axis of the force received by the force receiving unit 12 when the center axis P1 and the Z axis are made to coincide with each other. A direction component Fz, 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 for detecting Fz, Mx, and My shown in FIG. 10A, and a second bridge circuit 22 for detecting Fx, Fy, and Mz shown in FIG. 10B. And In the present embodiment, the first bridge circuit 21 and the second bridge circuit 22 including the strain gauges 41 to 48 are provided for each of the three beam units 20 in order to separate and detect the force components in the six axial directions. .

  The first bridge circuit 21 for detecting 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 an arrangement area 16a corresponding to the flexure part 16 one-to-one and an arrangement area 18a corresponding to the flexure part 18 one-to-one. . As a result, the ability to detect distortion generated by the pair of flexure sections 16 and 18 can be increased.

  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 each other with respect to the central axis P1. According to this, the resistance values of the strain gauges 41 to 48 having a line symmetrical positional relationship can be similarly changed with respect to the force component Fz in the Z-axis direction. Further, since the first bridge circuit 21 and the second bridge circuit 22 are configured, when no force acts on the force receiving unit 12, it is possible to cancel an unnecessary output signal so as not to be generated.

  A first strain gauge 41 and a second strain gauge 42, a third strain gauge 43 and a fourth strain gauge 44, a fifth strain gauge 45 and a seventh strain gauge 47, and a sixth strain gauge 46. And the eighth strain gauge 48 are provided at symmetrical positions with respect to a center line P2 in a 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 a line symmetrical positional relationship can be similarly changed with respect to the force component Fx in the X-axis direction. Further, since the first bridge circuit 21 and the second bridge circuit 22 are configured, when no force acts on the force receiving unit 12, it is possible to cancel an unnecessary output signal so as not to be generated.

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

  All of the fifth strain gauge 45, the sixth strain gauge 46, the seventh strain gauge 47, and the eighth strain gauge 48 are arranged such that the direction in which the strain is detected matches the direction in which the arm 14 extends. Is done.

  Then, as shown in FIG. 10A, when the input signal BV is applied to the first bridge circuit 21, the output signal Vo becomes unbalanced due to a change in the resistance value of the strain gauges 41 to 44. Change. In the force sensor 1A, stress is generated in the beam portion 20, but since the first bridge circuit 21 is formed, the force sensor 1A has an interference removal function and a temperature assurance function, and when detecting stress due to bending (bending), for example. , Cancels the stress caused by shearing.

  Further, as shown in FIG. 10B, when the input signal BV is applied to the second bridge circuit 22, the output signal Vo becomes unbalanced due to a change in the resistance value of the strain gauges 45 to 48. Change. In the force sensor 1A, stress is generated in the beam section 20, but since the second bridge circuit 22 is formed, the beam section 20 is provided with an interference removal function and a temperature assurance function. (Bending).

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

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

  According to Table 1, the first bridge circuit 21 confirms that the resistance values of the strain gauges 41 to 44 increase and decrease in the Z-axis direction force component Fz, the X-axis moment component Mx, and the Y-axis moment component My. , Fz, Mx, and 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 are calculated as a second component. 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. The output signal Vo is set to “1” when there is a bridge output (unbalanced output), and is set to “0” when the value is 0 or when the value is small.

  According to Table 2, the second bridge circuit 22 confirmed that the resistance values of the strain gauges 41 to 44 increased or decreased 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 (Fz, Mx, My) that are difficult to detect with the second bridge circuit 22 are detected by the first bridge circuit 21, and components (Fx) that are difficult to detect with the first bridge circuit 21. , Fy, Mz) are detected by the second bridge circuit 22 in a complementary configuration. By configuring the first bridge circuit 21 and the second bridge circuit 22 in this manner, it is possible to separate and detect the six-axis direction force components.

  Here, when one set of the strain gauges 41 to 48 is provided, the three sets are arranged to be rotationally symmetric with respect to the central axis P1. This makes it possible to make the same arrangement of the bridge circuit of the strain gauges 41 to 48 on each outer surface 20a, so that the workability when providing the strain gauges 41 to 48 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 becomes easy. 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.

  FIG. 3 is a perspective view (schematic diagram) showing an example of the 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) (signal processing part and wiring are not shown). In the second embodiment, a description will be given focusing on differences from the first embodiment.

  In the present embodiment, for example, a columnar body is subjected to cutting, laser machining, electric discharge machining, or a combination thereof to form an elevating unit including a force receiving portion 12, a fixing portion 19, a connecting portion 9, and a beam portion 20. The strain body 2 is formed. The strain body 2 has a space (through portion) for partitioning each of the force receiving portion 12, the fixing portion 19, the connecting portion 9, and the beam portion 20.

  In the present embodiment, the adjacent fixing portions 19 are connected by the connecting portion 9. The force receiving part 12, the beam part 20, the fixing part 19, and the connecting part 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 at a position apart from the central axis P1 in the radial side surface of the beam portion 20. Two connecting portions 9 and two fixing portions 19 are provided at positions surrounding the outer side surface 20a. The outer peripheral surface 19f of the fixing portion 19 and the outer peripheral surface 19g of the connecting portion 9 constitute the outer peripheral portion of the strain body 2. 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, one or both of the outer peripheral surface 19f and the outer peripheral surface 19g provided at a position farther from the central axis P1 than the plurality of strain gauges 41 to 48 are gripped. By doing so, it is possible to prevent erroneous contact with the plurality of strain gauges 41 to 48. Furthermore, 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 composed of the outer peripheral surface 19f and the outer peripheral surface 19g, Erroneous contact with any of the strain gauges 41 to 48 can be prevented.

  Slits 19b are formed on both surfaces of the flexure portions 16 and 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. Due to the slit 19b, both surfaces of the flexure portions 16 and 18 in the direction orthogonal to the central axis P1 and the fixed portion 19 are loosely coupled to each other, so that the flexure portions 16 and 18 are easily elastically deformed. Has become. Therefore, the strain gauges 41 to 48 have a structure in which strain can be easily detected.

  In addition, 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 provided.

(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 flexure element 2, This is an example of a structure in which the base 8 and the base 8 are integrated.

  FIG. 5 is a perspective view (schematic diagram) showing an example of the 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 schematic diagram, and 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 the present embodiment, for example, a cylindrical element body is subjected to cutting, laser processing, electric discharge machining, or a combination thereof, and the like, and is subjected to a strain generating body 2 having a force receiving portion 12, a fixed portion 19, and a beam portion 20, The table 6 and the base 8 are integrally formed. In addition, a space (through portion) for partitioning each of the force receiving portion 12, the fixing portion 19, the beam portion 20, the table 6, and the base 8 is formed.

  In the present embodiment, the table 6 is disposed on the central axis P1 and is connected to the force receiving portion 12. The base 8 is arranged 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 section 12, the beam section 20, the fixing section 19, the connecting section 19d, and the base 8 are an integral structure.

  With this configuration, the number of man-hours for incorporating the flexure element 2 into the table 6 and the base 8 can be reduced. In addition, since the table 6, the flexure element 2 and the base 8 are an integral structure, parts such as bolts and screws for assembling the flexure element 2 and the table 6 and the flexure element 2 and the base 8 are used. Can be reduced. Furthermore, the performance is improved because assembly errors due to the assembly of parts are eliminated. And such a force sensor 1C becomes easy to handle. Further, the flexure element 2 is protected by the table 6 and the base 8, so that a robust structure is provided.

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

  Of the surface of the base 8 in the Z-axis direction, on the surface opposite to the force receiving portion 12, four mounting holes 8a are formed at predetermined intervals at positions that are rotationally symmetric with respect to the central axis P1. The mounting hole 8a is for mounting 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 P1 than the outer peripheral surface of the table 6 and are provided at a position closer to the central axis P1 than the outer peripheral surface of the base 8. Thereby, when handling the force sensor 1 </ b> C, it is possible to prevent the plurality of strain gauges 41 to 48 from being erroneously contacted. 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 the plurality of strain gauges 41 to 48 from being erroneously contacted.

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

  Further, since the flexure element 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 19d is formed in the fixing portion 19 of the strain body 2. The fixing portion 19 of the strain body 2 is connected to the base 8 via a connecting portion 19d. Here, the force receiving portion 12 has a regular hexagonal shape in plan view.

(Fourth embodiment)
The above-described first to third embodiments are examples in which the strain body 2 has three beam portions 20, and have shown an example of a so-called Y beam structure. The force sensor 1 (1D) of the fourth embodiment is an example in which the strain 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 the force sensor 1D according to the present embodiment, FIG. 9 (A) is a plan view (schematic diagram) thereof, and FIG. 9 (B) is a front view thereof. It is a figure (schematic diagram) (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, for example, the prism element 2 is subjected to cutting, laser processing, electric discharge machining, or a combination thereof to form the strain generating element 2. The four beam portions 20 are arranged at rotationally symmetric positions with respect to the center axis P1 of the force receiving portion 12 in the Z-axis direction.

  In this embodiment, assuming that 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. This makes it easy to attach a measurement 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 in which the mounting hole or the like is inserted into the through hole 19a formed in the fixing portion 19 through a bolt or the like. , Even if the measuring jig or the like is largely displaced, it does not come into contact with the fixing portion 19. A cut-out portion 19e is formed at a lower portion of the fixing portion 19. Accordingly, the flexure portions 16 and 18 do not abut on the mounting table or the like in a state where the flexure sections 16 and 18 are assembled to the mounting table or the like through bolts or the like in the through holes 19a formed in the fixing section 19. Here, the strain body 2 has a square shape in plan view. Note that the present invention is not limited to this example, and the strain body 2 can be formed in a circular shape in plan view.

  The present invention is not limited to the embodiments described above, and various changes can be made without departing from the present invention. For example, in the above-described embodiment, a case where the present invention is applied to a six-axis force sensor is described. The present invention is not limited to this, and can be applied to a force sensor having 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. The configuration is not limited to this, and a configuration having five or more beam units 20 can be adopted. The strain generating element 2 is not limited to the above-described cutting, laser processing, electric discharge machining, or a combination thereof, and may employ a known processing technique such as an etching method, a die casting method, a press processing, and a 3D printer technique.

  For example, when a plurality of strain gauges 41 to 48 forming a bridge circuit are provided in the beam section, a predetermined number of strain gauges connected in advance to form a bridge circuit are attached as bridge-formed strain gauges ASSY (assembly). 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 outer surface 20a is formed by using the sputtering method or the vacuum evaporation method. By forming the strain gauges 41 to 48 at the same time, the productivity is remarkably improved, and it is also possible to prevent mutual displacement of the strain gauges by the simultaneous formation.

1, 1A, 1B, 1C, 1D Force sensor 2 Flexure element 6 Table 8 Base 9 Connecting part 12 Force receiving part 14 Arm part 16, 18 Flexure part 16a, 18a Arrangement area 19 Fixed part 19f Outer peripheral surface 19g Connecting 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 Central axis

Claims (8)

A flexure element having three or more beam portions provided at positions that are rotationally symmetric with respect to the central axis, and a plurality of strain gauges provided on an outer surface of the beam portion;
The strain body has 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 has an arm portion connected to the force receiving portion, and a flexure portion connected to both sides of the arm portion in a direction intersecting with an extending direction of the arm portion,
The force sensor, wherein the plurality of strain gauges are provided only on the outer surface at a position adjacent to the outer peripheral surface of the fixing portion. 2. The force sensor according to claim 1, wherein the plurality of strain gauges are provided in a pair of arrangement areas corresponding to the flexure unit on a one-to-one basis. 3. A connection portion connected to the adjacent fixed portions, further comprising:
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 arranged on the central axis and connected to the force receiving portion, and a base arranged at a position opposite to the table on the central axis and connected to the fixing portion, further comprising: The force sensor according to claim 1 or claim 2, wherein The table, the flexure element, and the base are an integral structure,
The force sensor according to claim 4, wherein: A first bridge circuit for detecting 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 unit;
A second bridge circuit for detecting 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 unit;
The plurality of strain gauges include a first strain gauge, a second strain gauge, a third strain gauge, and a fourth strain gauge that configure the first bridge circuit;
The semiconductor device according to any one of claims 1 to 5, further comprising a fifth strain gauge, a sixth strain gauge, a seventh strain gauge, and an eighth strain gauge constituting the second bridge circuit. A force sensor according to any one of the preceding claims. The first strain gauge and the third strain gauge, the second strain gauge and the fourth strain gauge, the fifth strain gauge and the seventh strain gauge, and the sixth strain gauge The force sensor according to claim 6, wherein the strain gauge and the eighth strain gauge are provided at positions that are line-symmetric with respect to the center axis. The first strain gauge and the second strain gauge, the third strain gauge and the fourth strain gauge, the fifth strain gauge and the seventh strain gauge, and the sixth strain gauge 8. The apparatus according to claim 6, wherein the strain gauge and the eighth strain gauge are provided at positions that are line-symmetric with each other with respect to a center line of the outer surface in a direction orthogonal to the center axis. 9. Force sensor.

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