JP2018159715A - Force sensor and method of configuring bridge circuit of force sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a force sensor in which a plurality of strain gauges can be provided on a strain inducer by preventing positional deviation of the strain gauges.SOLUTION: A force sensor 10 comprises: a plurality of strain gauges 22; and a strain inducer 11 including a principal surface 11a on which the strain gauges 22 are provided. The strain inducer 11 includes: a force receiving part 12 for receiving force; a fixed part 13 fixed to the force receiving part 12; and a beam part 14 coupling the power receiving part 12 and the fixed part 13 together. The strain gauges 22 are provided only on the principal surface 11a of the beam part 14. A bridge circuit detecting a force component in a prescribed direction is configured by strain gauges 22 provided at four positions symmetrical to each other with respect to a center line of the beam part 14.SELECTED DRAWING: Figure 3

Description

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

  Japanese Patent No. 6047703 (Patent Document 1) describes a configuration in which strain gauges are provided on both surfaces (front surface and back surface) of a strain generating body. Specifically, out of the strain generating body configured to include the force receiving portion, the fixing portion, and the arm portion connecting them, the front and back surfaces of the arm portion (that is, the front and back surfaces of the strain generating body) Each has a strain gauge.

Patent No. 6047703

  When the bridge circuit is configured by strain gauges provided on both surfaces of the arm portion as in the force sensor described in Patent Document 1, the strain gauges on the front surface and the strain gauges on the back surface are symmetrical (match in plan view). It is important to provide the detection accuracy. However, for example, even if an attempt is made to attach a strain gauge to each side of the arm portion, there is a possibility that a positional deviation may occur, and productivity is reduced if highly accurate position adjustment is performed.

  An object of the present invention is to provide a force sensor in which a plurality of strain gauges are provided on a strain generating body while preventing positional displacement. One and other objects and novel features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

  Of the inventions disclosed in the present application, the outline of typical ones will be briefly described as follows.

A force sensor according to one solution of the present invention includes a plurality of strain gauges and a strain generating body having a main surface on which the plurality of strain gauges are provided, and the strain receiving body receives force. Part, a fixed part fixed to the force receiving part, and a beam part connecting the force receiving part and the fixed part, wherein the plurality of strain gauges are the beam part And a bridge circuit that detects a force component in a predetermined direction by four of the plurality of strain gauges that are symmetrical to each other with respect to the center line of the beam portion. It is provided as follows. According to this, since a plurality of strain gauges are provided only on one surface (here, the main surface), positional deviation can be prevented and detection accuracy can be ensured.
A bridge circuit configuration method for a force sensor according to one solution of the present invention includes a plurality of strain gauges, and a strain generating body having a main surface on which the plurality of strain gauges are provided. A plurality of strain gauges, comprising: a force receiving portion that receives a force; a fixing portion that is fixed to the force receiving portion; and a beam portion that connects the force receiving portion and the fixing portion. Is a bridge circuit configuration method of a force sensor provided on the main surface of the beam portion and provided at positions symmetrical to each other with respect to the center line of the beam portion. A bridge circuit that detects force components in a predetermined direction is configured by four positions that are symmetrical with respect to the center line of the beam portion.

  In the force sensor, a force component Fx in the x-axis direction, a force component Fy in the y-axis direction, a force component Fz in the z-axis direction, a moment component Mx around the x-axis, a moment component My around the y-axis, and z In detecting the moment component Mz around the axis, the plurality of strain gauges includes a first bridge circuit group including a plurality of bridge circuits that detect Fz, Mx, and My, and a plurality of that detects Fx, Fy, and Mz. More preferably, the second bridge circuit group is divided into a second bridge circuit group including the bridge circuit. According to this, it is possible to prevent misalignment of a plurality of strain gauges constituting the first bridge circuit group and the second bridge circuit group, and to separately detect force components (including moment components) in six axes. .

  Further, in the force sensor, the beam portion includes: an arm connected to the force receiving portion; and a flexure extending in a direction intersecting with the extending direction of the arm and connected to the fixed portion. It is more preferable to have it. According to this, as compared with a beam portion without flexure (that is, only an arm), distortion due to bending, shearing, and twisting can be generated more and the detection accuracy can be ensured.

  In the force sensor, any one of the plurality of strain gauges is more preferably provided in the flexure. According to this, when a plurality of strain gauges are provided only on one surface (here, the main surface), the flexibility is easily improved by providing the flexure in addition to the arm so that the strain can be easily detected. be able to.

  In the force sensor, it is more preferable that the plurality of strain gauges are provided at positions symmetrical to each other with respect to the center line of the beam portion. According to this, the resistance value of the strain gauge having a symmetrical positional relationship can be similarly changed, and the output (unnecessary information) can be canceled by configuring the bridge circuit with the strain gauge.

  Of the inventions disclosed in the present application, effects obtained by typical ones will be briefly described as follows. According to one solution of the present invention, it is possible to provide a plurality of strain gauges on a strain generating body while preventing positional deviation.

It is explanatory drawing of the basic structure of the strain body which comprises the force sensor which concerns on this invention. It is explanatory drawing about the stress which generate | occur | produces in a prism, (a) is the state which applied the prism to the coordinate system, (b) is the distortion by Fx (-), (c) is the distortion by Fx (+), (d) Indicates distortion due to My (−), (e) indicates distortion due to Mx (−), and (f) indicates distortion due to Mz (−). It is a schematic plan view of the principal part of the force sensor which concerns on one Embodiment of this invention. FIG. 4 is an enlarged view of a portion surrounded by a circle c shown in FIG. 3. It is explanatory drawing of the bridge circuit with which the force sensor shown in FIG. 3 is provided, (a) is for Fz, Mx, My detection, (b) is for Fx, Fy, Mz detection. 4 is a detection table of a bridge circuit included in the force sensor shown in FIG. 3. It is explanatory drawing of an example which arrange | positions several strain gauges in the beam part of a strain body. It is explanatory drawing of an example which arrange | positions several strain gauges in the beam part of a strain body. It is explanatory drawing of an example which arrange | positions several strain gauges in the beam part of a strain body. It is a typical perspective view of the principal part of the force sensor which concerns on other embodiment of this invention. 11 is a detection table of a bridge circuit included in the force sensor shown in FIG. 10.

  In the following embodiments of the present invention, the description will be divided into a plurality of sections when necessary. However, in principle, they are not irrelevant to each other, and one of them is related to some or all of the other modifications, details, etc. It is in. For this reason, the same code | symbol is attached | subjected to the member which has the same function in all the figures, and the repeated description is abbreviate | omitted. In addition, the number of components (including the number, numerical value, quantity, range, etc.) is limited to that specific number unless otherwise specified or in principle limited to a specific number in principle. It may be more than a specific number or less. In addition, when referring to the shape of a component, etc., it shall include substantially the same or similar to the shape, etc., unless explicitly stated or in principle otherwise considered otherwise .

(Basic structure)
In the embodiment of the present invention, force components Fx, Fy, Fz in the three-axis direction of the orthogonal coordinate system (x-axis, y-axis, z-axis) in the three-dimensional space and moment components Mx, My, Mz around the three axes. This is applied to a 6-axis force sensor that can detect a total of 6 components simultaneously. First, the basic structure of the strain body 11 constituting the force sensor 10 (6-axis force sensor) will be described mainly with reference to FIG. FIG. 1 is an explanatory view (main part schematic plan view) of the basic structure of the strain-generating body 11 constituting the force sensor 10.

  The strain body 11 includes a force receiving portion 12 that receives a force, a fixing portion 13 that is fixed to the force receiving portion 12, and a beam portion 14 that connects the force receiving portion 12 and the fixing portion 13. Configured as a plate. The beam portion 14 extends in an arm 15 (first structural member) connected to the force receiving portion 12 and a direction intersecting the extending direction of the arm 15 (orthogonal direction in FIG. 1). And a flexure 16 (second structural member) connected to the head. FIG. 1 shows a center line a of the arm 15 parallel to the extending direction of the arm 15 (also a center line a of the beam portion 14) and a center line b of the flexure 16 parallel to the extending direction of the flexure 16 (center). It is also an intersection line b with respect to the line a). Since the beam portion 14 is configured to have the flexure 16 with respect to the arm 15, compared with a beam portion without the flexure 16 (that is, only the arm), distortion due to bending, shearing, and twisting in the beam portion 14 is further increased. It can be generated greatly, and the detection accuracy can be ensured.

  In FIG. 1, two flexures 16 are connected to one arm 15 in one beam portion 14. The connection portion between the arm 15 and the force receiving portion 12, the connection portion between the arm 15 and the flexure 16, and the connection portion between the flexure 16 and the fixing portion 13 are formed in a fillet shape in order to adjust the characteristics of the force sensor 10. Has been. These connecting portions may be chamfered, and the shape is arbitrary as long as the characteristics can be adjusted. In addition, since distortion also occurs at the connected portion, the connected portion is assumed to be included in the beam portion 14.

  Here, assuming that the arm 15 and the flexure 16 are prismatic structural members, a method of detecting stress generated in the prism will be described with reference to FIG. FIG. 2 is an explanatory diagram of the stress generated in the prism, and FIG. 2A shows a state in which the prism is applied to the coordinate system. FIG. 2B to FIG. 2F show how to distort when a force (including moment) is applied to a prism with the AB plane fixed. FIG. 2B shows distortion caused by Fx (−: minus direction, the same applies hereinafter), and FIG. 2C shows distortion caused by Fx (+: positive direction, same applies hereinafter). 2D shows distortion due to My (−), FIG. 2E shows distortion due to Mx (−), and FIG. 2F shows distortion due to Mz (−).

  In the following description, it is assumed that an element (strain gauge) for detecting strain is provided by forming a bridge circuit on the BC plane of the prism (main surface 11a which is one side of the strain-generating body 11). When Fx force is applied to the prism (see, for example, FIG. 2B and FIG. 2C), the resistance values of all strain gauges provided on the BC plane similarly change. For this reason, the bridge circuit output (unnecessary information) can be canceled by configuring the bridge circuit on the BC plane. For example, when Mx is applied, the prism is twisted as shown in FIG. At this time, since the strain gauge itself provided on the BC plane of the prism is twisted, the resistance value change of the strain gauge is zero or negligible. On the other hand, bending strain (FIG. 2 (d)) and shear strain (FIG. 2 (f)) can be detected by a strain gauge provided on the BC surface.

  In order to construct a force sensor 10 (6-axis force sensor) that detects and detects force components (including moment components) in 6-axis directions, there are three or more structures having beam portions 14. It is sufficient that one or more combinations of bending strain and shear strain can be detected. In addition, as long as bending strain and shear strain can be detected in the beam portion 14, the strain gauge may be provided on at least one of the arm 15 and the flexure 16 constituting the beam portion 14. In this way, even if a plurality of strain gauges are provided only on the main surface 11a (one surface) of the beam portion 14 (strain body 11), bending strain and shear strain can be detected. The force sensor 10 to be detected can be established.

(Embodiment 1)
The force sensor 10 according to this embodiment will be described with reference to FIGS. FIG. 3 is a schematic plan view of the strain body 11 which is a main part of the force sensor 10. FIG. 4 is an enlarged view of a circle c shown in FIG. FIG. 5 is an explanatory diagram of the bridge circuits 20 and 21 included in the force sensor 10. FIG. 5A illustrates an FzMxMy bridge circuit 20 (first bridge circuit) that detects Fz, Mx, and My, and FIG. Shows an FxFyMz bridge circuit 21 (second bridge circuit) for detecting Fx, Fy and Mz. FIG. 6 is a detection table of the FzMxMy bridge circuit 20 and the FxFyMz bridge circuit 21 of the force sensor 10. The force sensor 10 is a processing unit (not shown) having a CPU (Central Processing Unit) and a storage unit such as a ROM and a RAM in order to process the output signals of the bridge circuits 20 and 21 (for example, matrix calculation). ).

  The force sensor 10 according to the present embodiment includes a plurality of strain gauges 22 and a strain body 11 having a main surface 11a on which the plurality of strain gauges 22 are provided. The strain body 11 is a plate-like body whose outer shape is, for example, a circle (others may be a rectangle or a polygon), a main surface 11a (also referred to as a front surface or a first surface), and an opposite surface (a back surface, a first surface). 2 surfaces) and an outer surface (outer peripheral surface, third surface). In the present embodiment, the strain body 11 includes a central portion 12 as the force receiving portion 12, a concentric (annular) frame portion 13 around the central portion 12 as the fixing portion 13, a central portion 12 and the frame portion 13. And a plurality of beam portions 14 connecting the two. The beam portion 14 is provided radially from the center O of the central portion 12 toward the frame portion 13 and includes an arm 15 and a flexure 16.

  More specifically, in the strain body 11, the four beam portions 14 are arranged in the circumferential direction of the central portion 12 and the frame portion 13 (center O) so that the four beam portions 14 have a cross shape (X shape, cross shape) in plan view. Are arranged every 90 ° in the circumferential direction). Then, the arm 15 constituting the beam portion 14 extends radially from the center O, and the flexure 16 constituting the beam portion 14 extends in a direction intersecting with the extending direction of the arm 15. Thus, in the strain body 11, the flexure 16 is interposed between the frame portion 13 and the arm 15 so that the beam portion 14 can be regarded as an elastic body when the central portion 12 and the frame portion 13 are regarded as rigid bodies. A beam portion 14 is provided.

  Such a strain body 11 is obtained by forming a through-hole etc. in springy materials, such as aluminum alloy, alloy steel, and stainless steel, for example using NC (Numerical Control) processing machine. Thereby, in the strain body 11, spaces (penetrating portions) for partitioning the central portion 12, the frame portion 13, and the beam portion 14 are formed. By forming these spaces, the strain body 11 has an inner surface (a surface orthogonal to the main surface 11a and the opposite surface, an inner wall surface of the penetrating portion) with respect to the outer surface.

  In the force sensor 10, stress (strain such as bending, shearing, and twisting) can be generated in the beam portion 14 by applying a force to the central portion 12 (power receiving portion 12) of the strain generating body 11. For example, bending (deflection) occurs in the radial direction (extending direction) of the beam portion 14 and a direction orthogonal thereto, shearing occurs in a 45 ° direction with respect to the radial direction of the beam portion 14, and the beam portion 14. Torsion occurs in the circumferential direction. The force sensor 10 has a configuration in which a plurality of strain gauges 22 are provided only on the main surface 11a of the beam portion 14 when detecting these strains.

  As the strain gauge 22, 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, a flexible polyimide or epoxy resin is used. What was covered with the film can be used. Such a strain gauge 22 is affixed to the beam part 14 using an adhesive agent, and can detect and detect strain from a resistance change when the metal thin film is deformed by receiving the distortion of the beam part 14. Moreover, as the strain gauge 22, it is only necessary to separately detect strain (bending / shearing), and therefore a semiconductor strain gauge using a semiconductor thin film instead of a metal thin film can be used. Further, as a mounting method not based on the adhesion of the strain gauge 22, a metal thin film gauge may be directly formed on the main surface 11a of the beam portion 14 (strain body 11) using a sputtering method or a vacuum deposition method. Thus, even with various strain gauges 22, the force sensor 10 is provided only on one surface (ie, the main surface 11 a) of the strain-generating body 11, thereby preventing misalignment and ensuring detection accuracy. can do.

  Here, the force sensor 10 includes an FzMxMy bridge circuit 20 and an FxFyMz bridge circuit 21, and a plurality of strain gauges 22 are provided so as to be divided into an FzMxMy bridge circuit 20 and an FxFyMz bridge circuit 21. According to this, positional displacement of the plurality of strain gauges 22 constituting the FzMxMy bridge circuit 20 and the FxFyMz bridge circuit 21 can be prevented, and force components (including moment components) in six axis directions can be separated and detected. In the present embodiment, an FzMxMy bridge circuit 20 and an FxFyMz bridge circuit 21 are provided in each of the four beam portions 14 in order to separate force components in the six-axis directions (at least one set may be sufficient).

  Specifically, as shown in FIGS. 4 and 5A, the FzMxMy bridge circuit 20 is configured by the four strain gauges 22 (22a, 22b, 22c, 22d). Each of the strain gauges 22a, 22b, 22c, and 22d corresponds to the positions indicated by the symbols a, b, c, and d in the FzMxMy bridge circuit 20 shown in FIG. The FzMxMy bridge circuit 20 is configured by the strain gauges 22a, 22b, 22c, and 22d so as to be captured as a detection table of FIG.

  More specifically, the strain gauge 22 a and the strain gauge 22 c are provided at positions that are symmetric with respect to the center line a of the beam portion 14. Further, the strain gauge 22 b and the strain gauge 22 d are provided at positions that are symmetric with respect to the center line a of the beam portion 14. The strain gauge 22a and the strain gauge 22b are provided at positions aligned in the extending direction of the beam portion 14 (the direction along the center line a). Further, the strain gauge 22c and the strain gauge 22d are provided at positions aligned in the extending direction of the beam portion 14. These strain gauges 22a, 22b, 22c, and 22d are electrically connected (wired) as the FzMxMy bridge circuit 20. According to this, the resistance value of the strain gauge 22 having a symmetrical positional relationship can be changed similarly, and the output (unnecessary information) can be canceled by configuring the FzMxMy bridge circuit 20 with the strain gauge 22. Can do.

  In the FzMxMy bridge circuit 20, as shown in FIG. 5A, the strain gauges 22a and 22d connected in series at the positions a and d and the strain gauges 22b and 22c connected in series at the positions b and c are connected to the input signal BV. Are connected in parallel. Further, the strain gauges 22a and 22b connected in series at the positions a and b and the strain gauges 22c and 22d connected in series at the positions c and d are connected in parallel to the output signal Vo. In the FzMxMy bridge circuit 20 to which the input signal BV is applied, the output signal Vo changes when the resistance values of the strain gauges 22a, 22b, 22c, and 22d become unbalanced. In the force sensor 10, stress is generated in the beam portion 14, but the FzMxMy bridge circuit 20 is configured to provide an interference removal function and a temperature guarantee function, and for example, when detecting stress due to bending (deflection). The stress due to shear is canceled.

  As shown in FIGS. 4 and 5B, the FxFyMz bridge circuit 21 is configured by the four strain gauges 22 (22A, 22B, 22C, and 22D). Each of the strain gauges 22A, 22B, 22C, and 22D corresponds to the positions indicated by reference signs A, B, C, and D in the FxFyMz bridge circuit 21 shown in FIG. The FxFyMz bridge circuit 21 is configured by the strain gauges 22A, 22B, 22C, and 22D so as to be understood as a detection table of FIG. In addition, when the plurality of strain gauges 22 are provided only on one surface (here, the main surface 11a) of the strain generating body 11, in the present embodiment, the flexure 16 that easily detects strain is also used in addition to the arm 15. Provided. Thereby, the freedom degree for providing the some strain gauge 22 can be improved. In FIG. 4, the strain gauges 22A, 22B, 22C, and 22D are schematically shown regardless of their detection directions.

  More specifically, the strain gauge 22 </ b> A and the strain gauge 22 </ b> D are provided at positions that are symmetric with respect to the center line a of the beam portion 14. Further, the strain gauge 22B and the strain gauge 22C are provided at positions symmetrical to each other with respect to the center line a of the beam portion 14. The strain gauges 22 </ b> A and 22 </ b> B are provided at positions aligned in the extending direction of the beam portion 14 (direction along the center line a), and provided at positions symmetrical to the center line b of the flexure 16. It is done. Further, the strain gauge 22D and the strain gauge 22C are provided at positions aligned in the extending direction of the beam portion 14, and are provided at positions symmetrical to each other with respect to the center line b of the flexure 16. These strain gauges 22A, 22B, 22C, and 22D are electrically connected (wired) as the FxFyMz bridge circuit 21. According to this, the resistance value of the strain gauge 22 having a symmetrical positional relationship can be similarly changed, and the output (unnecessary information) can be canceled by configuring the FxFyMz bridge circuit 21 with the strain gauge 22. Can do.

  In the FxFyMz bridge circuit 21, as shown in FIG. 5B, the strain gauges 22A and 22D connected in series at the positions A and D and the strain gauges 22B and 22C connected in series at the positions B and C are connected to the input signal BV. Are connected in parallel. Further, the strain gauges 22A and 22B connected in series at the positions A and B and the strain gauges 22C and 22D connected in series at the positions C and D are connected in parallel to the output signal Vo. In the FxFyMz bridge circuit 21 to which the input signal BV is applied, the output signal Vo changes when the strain gauges 22A, 22B, 22C, and 22D are in an unbalanced state due to the change in resistance value. In the force sensor 10, stress is generated in the beam portion 14, but the FxFyMz bridge circuit 21 is configured to provide an interference removal function and a temperature guarantee function. For example, when detecting stress due to shearing, bending ( The stress due to bending is canceled.

  FIG. 6 shows detection results of the FzMxMy bridge circuit 20 and the FxFyMz bridge circuit 21 when the components Fx, Fy, Fz, Mx, My, and Mz are added to the force receiving portion 12 of the strain body 11 of the force sensor 10. The detection table is shown.

  In FIG. 6, for example, the FzMxMy bridge circuit 20 and the FxFyMz bridge circuit 21 provided in the first beam unit 14 in the clockwise direction in the plan view of the strain body 11 are “20-1” and “21-1”, respectively. Similarly, the second one is “20-2” “21-2”, the third one is “20-3”, “21-3”, the fourth one is “20-4”, “21-4”. "

  For example, “a1”, “b1”, “c1”, and “d1” of the FzMxMy bridge circuit 20-1 correspond to the strain gauges 22a, 22b, 22c, and 22d provided in the first beam section 14, respectively. Yes. The same applies to the FzMxMy bridge circuits 20-2, 20-3, and 20-4. For example, “A1”, “B1”, “C1”, and “D1” of the FxFyMz bridge circuit 21-1 correspond to the strain gauges 22A, 22B, 22C, and 22D provided in the first beam section 14, respectively. Yes. The same applies to the FxFyMz bridge circuits 21-2, 21-3, and 21-4.

  Then, when the resistance value of each strain gauge 22 constituting the FzMxMy bridge circuit 20 and the FxFyMz bridge circuit 21 is increased, it is detected as “+”, when it decreases, it is detected as “−”, and when it is small, it is detected as “0”. Results are shown. The output signal Vo of the FzMxMy bridge circuit 20 and the FxFyMz bridge circuit 21 is “1” when there is a bridge output (unbalanced output), and “0” when the value is 0 or small.

  From the detection table shown in FIG. 6, the FzMxMy bridge circuit 20 can detect Fz, Mx, and My. Further, the FxFyMz bridge circuit 21 can detect Fx, Fy, and Mz. In the force sensor 10, components (Fz, Mx, My) that are difficult to detect with the FxFyMz bridge circuit 21 are detected with the FzMxMy bridge circuit 20, and components (Fx, Fy, Mz) that are difficult to detect with the FzMxMy bridge circuit 20 are detected with the FxFyMz bridge. A complementary configuration is detected by the circuit 21. As described above, according to the force sensor 10 in which the FzMxMy bridge circuit 20 and the FxFyMz bridge circuit 21 (a plurality of strain gauges 22) are provided on the main surface 11a of the beam portion 14, the displacement is prevented and the force in the six axial directions is prevented. Components can be separated and detected.

  Note that the arrangement of the plurality of strain gauges 22 constituting the FzMxMy bridge circuit 20 and the FxFyMz bridge circuit 21 only on the main surface 11a in the beam portion 14 is not limited to the case shown in FIG. 4, but is also shown in FIGS. The case shown in FIG. FIGS. 7, 8, and 9 are explanatory diagrams of an example in which a plurality of strain gauges 22 are arranged in the beam portion 14 of the strain body 11, and are schematic plan views of main parts of the strain body 11. As shown in FIGS. 7 to 9, the combination (shape and direction) of the FzMxMy bridge circuit 20 and the FxFyMz bridge circuit 21 allows the strain gauge 22 to be provided only on the main surface 11a of the beam portion 14, It suffices if the force component can be separated and detected.

  In FIG. 7, strain gauges 22 a, 22 b, 22 c and 22 d constituting the FzMxMy bridge circuit 20 and strain gauges 22 A, 22 B, 22 C and 22 D constituting the FxFyMz bridge circuit 21 are provided on the arm 15 of the beam unit 14. In particular, the strain gauge 22a, the strain gauge 22A, the strain gauge 22B, and the strain gauge 22b are sequentially arranged in the vicinity of the center line a of the beam portion 14 from the center portion 12 side in the extending direction of the beam portion 14 (direction along the center line a). Provided. Further, the strain gauge 22c, the strain gauge 22D, the strain gauge 22C, and the strain gauge 22d are sequentially arranged in the vicinity of the center line a of the beam portion 14 from the center portion 12 side in the extending direction of the beam portion 14 (direction along the center line a). Provided.

  In FIG. 8, strain gauges 22 a, 22 b, 22 c and 22 d constituting the FzMxMy bridge circuit 20 and strain gauges 22 A, 22 B, 22 C and 22 D constituting the FxFyMz bridge circuit 21 are provided on the arm 15 of the beam unit 14. In particular, the strain gauge 22A on the outer side of the arm 15 (connection location), the strain gauges 22a and 22b in the vicinity of the center line a, and the strain gauge 22B on the outer side of the arm 15 (connection location) in that order from the central portion 12 side. (In the direction along the center line a). In addition, the strain gauge 22D on the outer side of the arm 15 (connection location), the strain gauges 22c and 22d in the vicinity of the center line a, and the strain gauge 22C on the outer side of the arm 15 (connection location) in that order from the center 12 side. (In the direction along the center line a).

  In FIG. 9, strain gauges 22A, 22B, 22C and 22D constituting the FxFyMz bridge circuit 21 are provided on the arm 15, and strain gauges 22a, 22b, 22c and 22d constituting the FzMxMy bridge circuit 20 are provided at the connection points of the flexure 16. . In particular, strain gauges 22 b, 22 a, 22 c, and 22 d are sequentially provided on the center line b of the flexure 16. The strain gauge 22 a and the strain gauge 22 c are provided at positions symmetrical to each other with respect to the center line a of the beam portion 14, and the strain gauge 22 b and the strain gauge 22 d are provided with respect to the center line a of the beam portion 14. Are provided at positions symmetrical to each other.

(Embodiment 2)
In the first embodiment, the case where the four beam portions 14 are configured in a cross shape (X shape, cross shape) in plan view has been described. In the present embodiment, the case where the three beam portions 14 are configured in a Y shape in plan view will be described with reference to FIGS. 10 and 11. FIG. 10 is a schematic perspective view of a strain body 11A, which is a main part of the force sensor 10A. FIG. 11 is a detection table of the FzMxMy bridge circuit 20 and the FxFyMz bridge circuit 21 included in the force sensor 10A. Below, it demonstrates focusing on the point which is different from the said Embodiment 1. FIG.

  In this embodiment, three beam portions 14 are arranged at equal intervals in the circumferential direction of the central portion 12 and the frame portion 13 (every 120 ° in the circumferential direction of the center O) so as to be Y-shaped in plan view. . Then, the arm 15 constituting the beam portion 14 extends radially from the center O, and the flexure 16 constituting the beam portion 14 extends in a direction intersecting with the extending direction of the arm 15. Thus, in the strain body 11A, the flexure 16 is interposed between the frame portion 13 and the arm 15 so that the beam portion 14 can be regarded as an elastic body when the central portion 12 and the frame portion 13 are regarded as rigid bodies. A beam portion 14 is provided. Although not shown in FIG. 10, a plurality of strain gauges 22 are provided only on the main surface 11a of the beam portion 14 as in the first embodiment (see FIG. 4).

  FIG. 11 shows detection results of the FzMxMy bridge circuit 20 and the FxFyMz bridge circuit 21 when the components Fx, Fy, Fz, Mx, My, and Mz are added to the force receiving portion 12 of the strain body 11A of the force sensor 10A. The detection table is shown.

  In FIG. 11, for example, the FzMxMy bridge circuit 20 and the FxFyMz bridge circuit 21 provided in the first beam section 14 in the clockwise direction in the plan view of the strain body 11A are “20-1” and “21-1”, respectively. Similarly, the second one is “20-2” and “21-2”, and the third one is “20-3” and “21-3”.

  For example, “a1”, “b1”, “c1”, and “d1” of the FzMxMy bridge circuit 20-1 correspond to the strain gauges 22a, 22b, 22c, and 22d provided in the first beam unit 14, respectively. (See FIG. 4). The same applies to the FzMxMy bridge circuits 20-2 and 20-3. Further, for example, “A1”, “B1”, “C1”, and “D1” of the FxFyMz bridge circuit 21-1 correspond to the strain gauges 22A, 22B, 22C, and 22D provided in the first beam section 14, respectively. (See FIG. 4). The same applies to the FxFyMz bridge circuits 21-2 and 21-3.

  From the detection table shown in FIG. 11, the FzMxMy bridge circuit 20 can detect Fz, Mx, and My. Further, the FxFyMz bridge circuit 21 can detect Fx, Fy, and Mz. As described above, according to the force sensor 10A in which the FzMxMy bridge circuit 20 and the FxFyMz bridge circuit 21 (the plurality of strain gauges 22) are provided on the main surface 11a of the beam portion 14, the positional deviation is prevented and the force in the six axial directions is prevented. Components can be separated and detected.

  Although the present invention has been specifically described above based on the embodiments, it is needless to say that the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the invention.

  For example, in the above embodiment, the case where the present invention is applied to a 6-axis force sensor has been described. Not limited to this, a force sensor that detects (measures) at least one component of the magnitude or direction of the force received by an object (if an inertial force is detected, a motion sensor such as an acceleration sensor or an angular velocity sensor) It can also be applied to.

  For example, in the above-described embodiment, the case where the central portion is applied as the force receiving portion and the frame portion is applied as the fixed portion has been described. The present invention is not limited to this, and the present invention can also be applied to the frame portion as the force receiving portion and the central portion as the fixed portion. In this case, the flexure constituting the beam portion is provided on the central portion side as the fixed portion.

  For example, in the above-described embodiment, when a plurality of strain gauges constituting the bridge circuit are provided in the beam portion, it is conceivable that a predetermined number of strain gauges are attached to each other so as to constitute the bridge circuit. However, the present invention is not limited to this, and a predetermined number of strain gauges connected in advance to form a bridge circuit can be attached as a single piece (bridge forming gauge). Since the present invention has a configuration in which a strain gauge is provided only on the main surface of the strain generating body, workability is further improved and productivity can be improved. Further, connection failure can be prevented, and the reliability of the force sensor can be improved.

10, 10A force sensor 11, 11A strain generating body 12 force receiving portion (central portion)
13 Fixed part (frame part)
14 beam unit 15 arm 16 flexure 20 FzMxMy bridge circuit (first bridge circuit)
21 FxFyMz bridge circuit (second bridge circuit)
22 Strain gauge

Claims (5)

A plurality of strain gauges, and a strain generating body having a main surface provided with the plurality of strain gauges,
The strain body includes a force receiving portion that receives a force, a fixing portion that is fixed to the force receiving portion, and a beam portion that connects the force receiving portion and the fixing portion. ,
The plurality of strain gauges are provided only on the main surface of the beam portion, and force in a predetermined direction is provided by four positions of the plurality of strain gauges that are symmetrical with respect to the center line of the beam portion. A force sensor comprising a bridge circuit configured to detect a component. The force sensor according to claim 1,
Detects force component Fx in the x-axis direction, force component Fy in the y-axis direction, force component Fz in the z-axis direction, moment component Mx around the x-axis, moment component My around the y-axis, and moment component Mz around the z-axis In doing so, the plurality of strain gauges includes a first bridge circuit group including a plurality of bridge circuits that detect Fz, Mx, and My, and a plurality of bridge circuits that detect Fx, Fy, and Mz. A force sensor provided to be divided into two bridge circuit groups. The force sensor according to claim 1 or 2,
The beam portion includes an arm connected to the force receiving portion, and a flexure extending in a direction intersecting with the extending direction of the arm and connected to the fixed portion. A characteristic force sensor. A plurality of strain gauges, and a strain generating body having a main surface provided with the plurality of strain gauges,
The strain body includes a force receiving portion that receives a force, a fixing portion that is fixed to the force receiving portion, and a beam portion that connects the force receiving portion and the fixing portion. ,
The force sensor has a bridge circuit configuration method in which the plurality of strain gauges are provided on the main surface of the beam portion and are provided at positions symmetrical to each other with respect to a center line of the beam portion,
A bridge circuit for a force sensor, comprising a bridge circuit that detects force components in a predetermined direction based on four of the plurality of strain gauges that are symmetrical with respect to a center line of the beam portion. Configuration method. The force sensor bridge circuit configuration method according to claim 4,
Detects force component Fx in the x-axis direction, force component Fy in the y-axis direction, force component Fz in the z-axis direction, moment component Mx around the x-axis, moment component My around the y-axis, and moment component Mz around the z-axis In doing so, the plurality of strain gauges includes a first bridge circuit group including a plurality of bridge circuits that detect Fz, Mx, and My, and a plurality of bridge circuits that detect Fx, Fy, and Mz. A method of configuring a bridge circuit of a force sensor, characterized by being divided into two bridge circuit groups.

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