CN110857896B

CN110857896B - Force sensor

Info

Publication number: CN110857896B
Application number: CN201810908703.2A
Authority: CN
Inventors: 由井夏树; 向井优; 牧野泰育
Original assignee: Leptrino Co ltd; Sintokogio Ltd
Current assignee: Leptrino Co ltd; Sintokogio Ltd
Priority date: 2018-08-10
Filing date: 2018-08-10
Publication date: 2023-05-02
Anticipated expiration: 2038-08-10
Also published as: CN110857896A

Abstract

The invention provides a force sensor. Provided is a technique which can improve the productivity of a force sensor and can improve the reliability. The force sensor (10) is provided with: a strain body (20) having a front surface (20 a) and an rear surface (20 b); and a plurality of strain gauges (30) provided on the front surface (20 a) and the back surface (20 b). The strain body (20) is configured to include: a force receiving part (21) for receiving force; a fixing part (22) fixed relative to the stress part; an arm (23) connecting the force receiving portion and the fixing portion; and a bending portion (24) extending in a direction intersecting the extending direction of the arm portion and connected to the fixing portion. A plurality of strain gauges (30) are provided on the arm (23), and include a bending strain gauge that detects bending of the arm (23) and a shearing strain gauge that detects shearing of the arm (23). The strain gauges form a bridge circuit.

Description

Force sensor

Technical Field

The present invention relates to a force sensor (also referred to as a force-dividing meter), and more particularly to a technique effective for a 6-axis force sensor adapted to detect 6 components of force components in an x-axis direction, a y-axis direction, and a z-axis direction and moment components around each axis.

Background

Japanese patent application laid-open No. 57-169643 (hereinafter referred to as "patent document 1") describes a technique relating to a multi-component force gauge using strain gauges. The force-dividing gauge is configured to measure an external force based on only bending strain by studying the shape of an arm portion that connects a base portion and a frame body in a cross shape in a plan view (see, lines 12 to 16 on the upper left side of the third page of the specification of patent document 1). For this reason, strain gauges (i.e., bending strain gauges) for detecting bending strain are bonded to 4 surfaces (front surface, back surface, and both side surfaces) around the axis of the arm portion of the quadrangular prism, respectively, in order to detect external forces in each direction by using bending strain (see the upper right row 19 to the lower left row 3 in the third page of the description of patent document 1).

Patent document 1: japanese patent laid-open No. 57-169643

As in the technique described in patent document 1, in the conventional force-dividing gauge, the shape of the arm is exclusively studied, and the external force is measured based on the bending strain of the arm, so that the shear strain generated in the arm can be suppressed and captured by the bending strain. This is because it is considered that the force-dividing gauge is a member for detecting and detecting a minute change (output) due to an external force, and is effective for detecting and detecting a bending strain that generates a change greater than a shear strain.

However, in the technique described in patent document 1, it is easy to attach (bond) strain gauges to the front and back surfaces of the arm portions of the quadrangular prism (the surfaces formed by the 4 arm portions having a cross shape in a plan view), but it is difficult to attach strain gauges to 2 side surfaces (surfaces perpendicular to the upper and lower surfaces) of the arm portions. This is because the space on the side surface side of the arm, that is, the space enclosed by the base, the frame, and the arm is narrow (has an obstacle) when strain is applied. Therefore, when the strain gauge is attached to the 2 side surface (inner side surface) of the arm portion, the working man-hour increases. In addition, wiring layout of the strain gauge is difficult, and malfunction due to disconnection or the like is likely to occur.

Disclosure of Invention

The invention aims to provide a technology capable of improving the productivity of a force sensor and improving the reliability. The above and other objects and novel features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

In order to solve the above problems, a force sensor as a solution of the present invention includes: a strain body having a surface and an interior; and a plurality of strain gauges provided on the front surface and the back surface, the strain body including: a force receiving portion for receiving force; a fixing part fixed relative to the stress part; an arm portion connecting the force receiving portion and the fixing portion; and a bending portion extending in a direction intersecting the extending direction of the arm portion and connected to the fixing portion, wherein the plurality of strain gauges includes a predetermined number of bending strain gauges for detecting bending of the arm portion and a predetermined number of shearing strain gauges for detecting shearing of the arm portion, and the strain gauges form a bridge circuit.

Thus, a force sensor can be provided in which strain gauges are not provided on the side surfaces (surfaces orthogonal to the front and rear surfaces) of the arm, but only on the front and rear surfaces of the arm of the strain gauge. Therefore, productivity of the force sensor can be improved. In addition, since there is no problem caused by attaching strain gauges to the side surfaces of the arm portions, the reliability of the force sensor can be improved.

In the force sensor according to the above-described one aspect, it is preferable that the bending strain gauge has a detection direction of the bending strain gauge as an extending direction of the arm portion, and the shearing strain gauge has a detection direction of the shearing strain gauge as a direction of 45 ° with respect to the extending direction of the arm portion.

In the force sensor according to the above-described one aspect, it is preferable that the force sensor is configured by integrating a predetermined number of the bending strain gauges and a predetermined number of the shearing strain gauges so as to be adhered to the front surface and the rear surface of the arm. Thereby improving productivity as compared with attaching strain gauges one by one.

In the force sensor according to the above-described one aspect, it is more preferable that a predetermined number of the bending strain gauges form a first bridge circuit, and a predetermined number of the shearing strain gauges form a second bridge circuit. The arm is bent (flexed), sheared, and twisted by a force, but a bridge circuit is formed by the arrangement of a predetermined number of strain gauges and the connection to the arm, so that the bending (flexed) and twisting generated in the arm are eliminated, for example, and the shearing stress can be detected.

In the force sensor according to the first aspect, the force receiving portion and the fixing portion are preferably configured to be concentric, and the 3 arm portions are preferably arranged at equal intervals in the circumferential direction of the force receiving portion and the fixing portion so as to have a Y-shape in a plan view. When the number of arm portions is small as 3, the number of strain gauges provided in the strain gauge body becomes small as a whole, and the number of steps such as attaching the strain gauge is also small, so that productivity can be improved, and production cost can be reduced.

Or more preferably, the force receiving portion and the fixing portion are configured to be concentric, and the 4 arm portions are disposed at equal intervals in the circumferential direction of the force receiving portion and the fixing portion so as to be cross-shaped in a plan view. In a 6-axis force sensor in which 3 arms are formed in a Y-shape in a plan view, in order to detect 6 components in total of force components in the x-axis direction, the Y-axis direction, and the z-axis direction and moment components around each axis, it is necessary to perform matrix operation on outputs of strain gauges provided to the respective arms. In this regard, in a 6-axis force sensor in which 4 arm portions are formed in a cross shape in a plan view, each component can be detected without performing matrix operation.

In the force sensor according to the above-described one aspect, it is preferable that a voltage of 1 to 10V is applied to the first bridge circuit and the second bridge circuit. By applying a voltage of 1 to 10V to the bridge circuit formed in the arm portion, the shear stress can be easily and accurately detected.

According to the present invention, productivity of the force sensor can be improved, and reliability can be improved.

Drawings

Fig. 1 is a schematic plan view of the main part of the force sensor according to embodiment 1 of the present invention.

Fig. 2 is a schematic top view of the inside of the main part of the force sensor shown in fig. 1.

Fig. 3 is a schematic perspective view of the main part of the force sensor shown in fig. 1.

Fig. 4 is a block diagram of a signal processing unit included in the force sensor shown in fig. 1.

Fig. 5 is a diagram for explaining a bridge circuit provided in the force sensor shown in fig. 1.

Fig. 6 is a table showing a detection of a bridge circuit included in the force sensor shown in fig. 1.

Fig. 7 is a schematic plan view of the main part of the force sensor according to embodiment 2 of the present invention.

Fig. 8 is a schematic top view of the inside of the main portion of the force sensor shown in fig. 7.

Fig. 9 is a schematic plan view of the main part of the force sensor according to embodiment 3 of the present invention.

Fig. 10 is a schematic top view of the inside of the main portion of the force sensor shown in fig. 9.

Fig. 11 is a detection table of a bridge circuit provided in the force sensor shown in fig. 9.

Description of the reference numerals

10. 10A, 10B … force sensors; 20 … strain variant; 20a … surface; 20b …;20c … outer sides; 20d … inner side; 21 … central portion (force receiving portion); 22 … frame (fixing portion); 23. 23A, 23B, 23C, 23D … arm; 24 … elastic part; 30 … strain gauge; 31. 31A, 31B, 31C, 31D,31E, 31F … bridge circuits; 32 … integral measuring instrument; 40 … signal processing part.

Detailed Description

In the following embodiments of the present invention, description will be made by dividing the embodiment into a plurality of parts and the like as necessary, but in principle, they are not independent of each other, and a part or all of the modified examples of one and the other have a detailed relationship. Therefore, in all the drawings, the same reference numerals are given to the components having the same functions, and the repetitive description thereof will be omitted. The number of the constituent elements (including the number, the numerical value, the amount, the range, etc.) is not limited to a specific number, but may be a specific number or more or less, unless otherwise specifically indicated, or may be clearly limited to a specific number in principle, or the like. In addition, when the shape of the constituent elements is described, the content or the like which is actually similar or analogous to the shape or the like is included, except for the case where the shape is particularly explicitly described and the case where the shape is considered to be clearly not in principle.

(embodiment 1)

In embodiment 1 of the present invention, a force sensor (a sensor for detecting an inertial force is also referred to as an acceleration sensor, an angular velocity sensor, or other motion sensor) that is suitable for detecting (measuring) a component of at least one of the magnitude and the direction of a force received by an object will be described. Specifically, a description will be given of a 6-axis force sensor applied to a system capable of simultaneously detecting 6 components of force components in a 3-axis direction of an orthogonal coordinate system (x-axis, y-axis, z-axis) in a three-dimensional space and moment components in a direction around the 3-axis.

The force sensor 10 of the present embodiment will be described with reference to fig. 1 to 6. Fig. 1 and 2 are schematic plan views of main portions of the force sensor 10, and fig. 3 is a schematic perspective view thereof. As shown in fig. 1 to 3, the force sensor 10 includes a strain body 20 that generates strain by applying force, and a plurality of strain gauges 30 that detect strain of the strain body 20. Fig. 4 is a block diagram of the signal processing unit 40 included in the force sensor 10. The signal processing unit 40 is provided in a housing (not shown) to which the strain body 20 is attached, for example, and processes outputs from the plurality of strain gauges 30. Fig. 5 is a diagram for explaining the bridge circuit 31 provided in the force sensor 10. Fig. 6 is a table of detection of the bridge circuit 31 of the force sensor 10. The bridge circuit 31 is configured using a predetermined number of strain gauges 30, and its output signal is processed by a signal processing unit 40.

As shown in fig. 1 to 3, the strain body 20 is a circular plate-like body having a front surface 20a (first surface), a rear surface 20b (second surface opposite to the first surface), and an outer surface 20c (outer peripheral surface). The strain body 20 includes a central portion 21 having a center O of the strain body 20, a frame portion 22 concentric around the central portion 21, and a plurality of arm portions 23 (also referred to as beams) connecting the central portion 21 and the frame portion 22. In a more specific shape of each portion of the strain body 20, the central portion 21 is a circular plate shape, the frame portion 22 is a ring shape, and the arm portion 23 is a quadrangular prism shape.

In the present embodiment, the arm portions 23 are arranged at equal intervals (every 120 ° in the circumferential direction of the center O) in the circumferential directions of the center portion 21 and the frame portion 22 so as to form a Y-shape in 3 plan views. That is, 3 arm portions 23 (23A, 23B, 23C) extend radially from the center O between the center portion 21 and the frame portion 22. The strain body 20 includes an elastic portion 24 (bending portion) interposed between the frame portion 22 and the arm portion 23 so that the arm portion 23 is regarded as an elastic body when the central portion 21 and the frame portion 22 are regarded as rigid bodies. The elastic portion 24 is connected to the arm portion 23 and extends in a direction intersecting the extending direction of the arm portion 23 so as to have a T shape in plan view.

Such a strain body 20 is obtained by forming a through hole or the like in a material having spring characteristics such as an aluminum alloy, an alloy steel, or a stainless steel using an NC (Numerical Control: numerical control) processing machine, for example. Thus, a space (through portion) for forming the central portion 21, the frame portion 22, and the arm portion 23, and a space (through portion having a slit shape in a plan view) for forming the elastic portion 24 are formed in the strain body 20. By forming these spaces, strain body 20 has inner surface 20d (surface orthogonal to front surface 20a and rear surface 20b, inner wall surface of the through portion) in addition to outer surface 20 c.

In the force sensor 10 of the present embodiment, the center portion 21 is used as a force receiving portion of the strain body 20, the frame portion 22 is used as a fixing portion fixed to the force receiving portion, and the arm portion 23 is used as a portion for generating strain. That is, the strain body 20 is configured to bend (flex), shear, or twist the arm portion 23 by a force. That is, bending (deflection) occurs in the extending direction of the arm portion 23, shearing occurs in the 45 ° direction with respect to the extending direction of the arm portion 23, and twisting occurs in the circumferential direction of the arm portion 23. The stress portion and the fixing portion of the strain body 20 may be a central portion 21 and the stress portion may be a frame portion 22.

Specifically, when the force Fx in the x-axis direction is applied to the center portion 21, which is the force receiving portion of the counterpart body 20, the

arm portions

23B and 23C are deformed by the force, and the elastic portion 24 is deflected in the arm portion 23A, so that no strain is generated. When the force Fy in the y-axis direction is applied, the

arm portions

23A, 23B, and 23C are deformed by the force. When the force Fz in the z-axis direction is applied, the

arm portions

23A, 23B, and 23C are uniformly deflected. When the torque Mx in the x-axis direction is applied, only torsion is generated in the arm portion 23A, and the

arm portions

23B and 23C are deflected by applying the torque thereto. When the moment My in the y-axis direction is applied, the moment acts on each of the

arm portions

23A, 23B, and 23C, and the arm portions flex. When the moment Mz in the z-axis direction is applied, the

arm portions

23A, 23B, and 23C are uniformly deflected.

In such a strain body 20, a plurality of strain gauges 30 are provided on the front surface 20a and the rear surface 20b of the strain body 20. As the strain gauge 30, for example, a member obtained by covering a wiring pattern of a metal thin film (metal foil or the like) of a Cu (copper) -Ni (nickel) alloy or a ni—cr (chromium) alloy with a flexible polyimide or an epoxy resin film is used. Such a strain gauge 30 is attached to the arm portion 23 using an adhesive, and can detect and detect strain from a change in resistance when the metal thin film is deformed by the strain of the arm portion 23. Further, a semiconductor strain gauge using a semiconductor thin film instead of a metal thin film can be used as the strain gauge 30. In addition, as a method for mounting the strain gauge 30 without bonding, a metal thin film gauge may be directly formed on the front surface 20a and the back surface 20b of the strain body 20 by vacuum vapor deposition or sputtering.

In the present embodiment, the strain gauge 30 is provided to the arm portion 23 such that the detection direction (sensing direction) thereof is the same as the bending (flexing) generation direction and the shearing generation direction of the arm portion 23. In fig. 1 and 2, the detection direction (sensing direction) of the strain gauge 30 at each position is shown by an arrow. Specifically, as shown in fig. 1 and 2, a strain gauge 30 (referred to as a bending strain gauge) that detects bending (flexing) of the arm portion 23 is disposed in each of the positions Aa, ab, ac, ad, ba, bb, bc, bd, ca, cb, cc, cd of the strain body 20 so that the detection direction becomes the extending direction of the arm portion 23. In each of the positions Da, db, dc, dd, ea, eb, ec, ed, fa, fb, fc, fd of the strain bodies 20, a strain gauge 30 (referred to as a shear strain gauge) for detecting shearing of the arm portion 23 is disposed so that the detection direction is 45 ° with respect to the extending direction of the arm portion 23 (or 135 ° direction). In this way, even if the same strain gauge 30 is used for the plurality of strain gauges 30, the bending strain gauge and the shearing strain gauge can be included by the arrangement of the detection directions.

In the arm portion 23A extending in the direction parallel to the x-axis direction shown in fig. 1 and 2, a predetermined number (four) of strain gauges 30 (bending strain gauges) are arranged one by one at positions Ba to Bd on the center portion 21 side, and a predetermined number (four) of strain gauges 30 (shearing strain gauges) are arranged one by one at positions Ea to Ed on the frame portion 22 side, and 8 strain gauges 30 are provided in total. The strain gauge 30 at the position Ba, bc, ea, eb is located on the surface 20a (see fig. 1) of the strain body 20 (arm portion 23A), and the position Ba and the position Bc have a symmetrical relationship with respect to the center line of the arm portion 23A in the extending direction in a plan view. Therefore, the detection direction of the strain gauge 30 at the position Ba and the detection direction of the strain gauge 30 at the position Bc are in parallel relation, and the detection direction of the strain gauge 30 at the position Ea and the detection direction of the strain gauge 30 at the position Eb are in a crossing relation on the center line of the arm portion 23A. The strain gauge 30 at the position Bb, bd, ec, ed is located on the rear surface 20b (see fig. 2) of the strain body 20 (arm 23A), and the position Bb and the position Bd have a symmetrical relationship with respect to the center line of the arm 23A in the extending direction in a plan view, and the position Ec and the position Ed have a symmetrical relationship. Therefore, the detection direction of the strain gauge 30 at the position Bb and the detection direction of the strain gauge 30 at the position Bd are in parallel relation, and the detection direction of the strain gauge 30 at the position Ec and the detection direction of the strain gauge 30 at the position Ed are in a crossing relation on the center line of the arm portion 23A. The strain gauge 30 is similarly arranged in the other 2

arm portions

23B and 23C.

In the present embodiment, for example, one bridge circuit 31 shown in fig. 5 (the table in fig. 6 is referred to as a bridge circuit 31A) is configured by using a predetermined number (four) of strain gauges 30 (bending strain gauges) provided at positions Aa to Ad. For example, one bridge circuit 31 shown in fig. 5 (referred to as a bridge circuit 31D in the table of fig. 6) is configured by a predetermined number (four) of strain gauges 30 (shear strain gauges) provided at positions Da to Dd. The bridge circuit 31 shown in fig. 5 is provided with the strain gauge 30 at a position a, b, c, d, and is electrically connected (wired).

Specifically, the strain gauges 30 connected in series at the positions a and d and the strain gauges 30 connected in series at the positions b and c are connected in parallel with respect to the input signal Vi. The strain gauges 30 connected in series at the positions a and b and the strain gauges 30 connected in series at the positions c and d are connected in parallel with respect to the output signal Vo. In the bridge circuit 31 to which the input signal Vi of 1 to 10V is applied, for example, the output signal Vo changes when the resistance value of the strain gauge 30 changes to an unbalanced state. Although bending (flexing), shearing, and torsion are generated in the arm portion 23 due to the force, in the present embodiment, the bridge circuit 31 constituting the strain gauge 30 has a disturbance removal function and a temperature assurance function, and for example, bending (flexing) and torsion are eliminated when stress due to shearing is detected. By applying a voltage of 1 to 10V, the shear stress can be accurately detected.

In the present embodiment, the position a of the bridge circuit 31 corresponds to the position Aa of the strain body 20, the position b corresponds to the position Ab, the position c corresponds to the position Ac, and the position d corresponds to the position Ad. In this way, in order to clarify the correspondence, the position symbol a, b, c, d (lower case letter) of the bridge circuit 31 and the 2 nd (lower case letter) of the position symbol Aa, ab, ac, ad of the strain body 20 are respectively associated. The bridge circuit 31 composed of the strain gauges 30 provided at the positions Aa to Ad of the strain body 20 corresponds to the detection table of the bridge circuit 31A shown in fig. 6. In order to clarify the correspondence, the symbol (capital letter) of the bridge circuit 31A in fig. 6 is associated with the 1 st (capital letter) of the position symbol Aa, ab, ac, ad of the strain body 20. The same applies to the

other bridge circuits

31B, 31C, 31d,31e, 31F corresponding to the positions Ba to Bd, ca to Cd, da to Dd, ea to Ed, fa to Fd.

Fig. 6 is a detection table showing detection results of the bridge circuits 31A to 31F when forces Fx, fy, fz, moments Mx, my, mz in the respective directions are applied to the strain body 20 of the force sensor 10. In the detection table shown in fig. 6, the resistance values of the strain gauges 30 in the positions Aa to Ad (bridge circuit 31A), ba to Bd (bridge circuit 31B), ca to Cd (bridge circuit 31C), da to Dd (bridge circuit 31D), ea to Ed (bridge circuit 31E), fa to Fd (bridge circuit 31F) are set to "+" when they are increased, "-" when they are decreased, and "0" when they are not changed. The output signal Vo of the bridge circuits 31A to F is set to "1" when unbalanced output of the bridge is generated, and is set to "0" when unbalanced output is not generated.

Here, the signal processing unit 40 that calculates the force acting on the force receiving unit (the central unit 21) from the output signals Vo of the bridge circuits 31A to 31F will be described with reference to fig. 4. The bridge circuits 31A to 31F and the signal processing section 40 are electrically connected by wiring. In the signal processing section 40, signals (analog signals) from the bridge circuits 31A to 31F (CH 1 to CH 6) are amplified by the respective amplifiers 41 (AMP 1 to AMP 6), and then the analog signals are converted into digital signals by the a/D converter 42 and sent to the CPU 43. By using the amplifier 41 in this way, even a weak output shear strain can be detected.

In the CPU43, 6 components (Fx, fy, fz, mx, my, mz) of the force acting on the force receiving portion (the central portion 21) are calculated by referring to the calibration matrix (correction matrix) from the memory 44. The result of the signal processing unit 40 can be output as a digital signal from the CPU43, or can be output as an analog signal using the D/a converter 45.

The signal processing unit 40 thus has a calibration function of correcting the output signal Vo from the bridge circuits 31A to 31F. As shown in the following expression, the force F acting on the force receiving portion (the center portion 21) can be obtained by multiplying the calibration matrix C by the value V obtained by a/D converting the detection values from the bridge circuits 31A to 31F.

[ 1]

F＝C×V…(1)

[ 2]

F＝[F _X F _Y F _Z M _X M _Y M _Z ] ^T …(2)

[ 3]

[ 4]

V＝[V ₁ V ₂ V ₃ V ₄ V ₅ V ₆ ] ^T …(4)

The calibration matrix C is pre-calculated as a matrix inherent to each force sensor 10. Specifically, the calibration matrix C can be calculated from the condition of applying a rated load of 6 components to the force sensor 10 and the detection result of the deformation amount of the strain body 20 at this time. By using such a calibration matrix C, the force acting on the force receiving portion (central portion 21) of the force sensor 10 can be measured with high accuracy.

As described above, according to the present embodiment, the strain gauge 30 is not provided on the inner side surface 20d of the arm portion 23, but the strain gauge 30 can be provided only on the

surfaces

20a, 20b of the strain body 20 (arm portion 23) having no obstacle. Therefore, the strain gauge 30 does not need to be provided in a narrow space surrounded by the center portion 21, the frame portion 22, and the arm portion 23, and therefore productivity of the force sensor 10 can be improved. In addition, since there is no problem (for example, disconnection) caused by attaching the strain gauge 30 to the inner surface 20d of the arm portion 23, the reliability of the force sensor 10 can be improved.

As described later in embodiment 3, the strain body 20 can be configured by using 4 arm portions 23. However, when the number of strain gauges 30 provided in the strain body 20 is small as compared with the present embodiment in which 4 arm portions 23 are formed by 3 arm portions, the number of steps for attaching the strain gauges 30 and the like is small, and productivity of the force sensor 10 can be improved. In addition, the production cost of the force sensor 10 can also be reduced.

(embodiment 2)

In embodiment 1, the case where the strain gauges 30 are attached to the arm 23, respectively, will be described. In embodiment 2 of the present invention, a case where an integral measuring instrument 32 configured by integrating a predetermined number of strain gauges 30 is attached to an arm 23 will be described with reference to fig. 7 and 8. Fig. 7 and 8 are schematic plan views of the main portions of the force sensor 10A.

The force sensor 10A of the present embodiment includes a sheet-like integrated meter 32 formed by integrating a predetermined number of strain gauges 30 so as to be adhered to the front surface 20A (see fig. 7) and the rear surface 20B (see fig. 8) of each arm 23 (23A, 23B, 23C). That is, a predetermined number of strain gauges 30 are arranged on the same surface of the sheet-like base material. For example, the integral measuring instrument 32 attached to the surface 20a of the arm 23A includes four strain gauges 30 in total, i.e., strain gauges 30 (bending strain gauges) at positions Ba and Bc and strain gauges 30 (shearing strain gauges) at positions Ea and Eb. The integral measuring instrument 32 attached to the rear surface 20b of the arm 23A includes four strain gauges 30 in total, i.e., strain gauges 30 (bending strain gauges) at positions Bb and Bd and strain gauges 30 (shearing strain gauges) at positions Ec and Ed. The integral measuring instrument 32 is attached to the other 2

arm portions

23B and 23C in the same manner.

By using such an integral gauge 32, productivity can be improved as compared with attaching strain gauges 30 one by one. After the integral measuring instrument 32 is attached to each arm 23, each strain gauge 30 is electrically connected so as to constitute each bridge circuit 31A to 31F (see fig. 5 and 6).

Embodiment 3

In embodiment 1, the case where the 3 arm portions 23 are formed in a Y shape in plan view is described. In embodiment 3 of the present invention, a case where 4 arm portions 23 are formed in a cross shape (cross shape) in a plan view will be described with reference to fig. 9 to 11. Fig. 9 and 10 are schematic plan views of the main parts of the force sensor 10B, and fig. 11 is a detection table of the bridge circuit 31 of the force sensor 10B.

In the force sensor 10B (strain body 20) of the present embodiment, the circular center portion 21, which is a force receiving portion, and the annular frame portion 22, which is a fixed portion, are configured concentrically, and the 4 four rectangular-prism-shaped arm portions 23 are disposed at equal intervals (every 90 ° in the circumferential direction of the center O) in the circumferential direction of the center portion 21 and the frame portion 22 so as to be cross-shaped in a plan view. Namely, 4 arm portions 23 (23A, 23B, 23C, 23D) extend radially from the center O between the center portion 21 and the frame portion 22. The strain body 20 includes an elastic portion 24 (bending portion) interposed between the frame portion 22 and the arm portion 23 so that the arm portion 23 is regarded as an elastic body when the central portion 21 and the frame portion 22 are regarded as rigid bodies. The elastic portion 24 actually absorbs the axial strain of the arm portion 23. The elastic portion 24 is connected to the arm portion 23 so as to extend in a direction intersecting the extending direction of the arm portion 23 in a T-shape in plan view. That is, the strain body 20 of the force sensor 10B is configured to bend (flex), shear, or twist the arm portion 23 by a force.

In the present embodiment, the strain gauge 30 is provided to the arm portion 23 such that the detection direction (sensing direction) thereof is the same as the bending (flexing) generation direction and the shearing generation direction of the arm portion 23. In fig. 9 and 10, the detection direction (sensing direction) of the strain gauge 30 at each position is shown by an arrow. Specifically, as shown in fig. 9 and 10, the strain gauge 30 (referred to as a bending strain gauge) that detects bending (flexing) of the arm portion 23 is arranged at each of the positions Ca1, ca2, cb1, cb2, cc1, cc2, cd1, cd2, da, db, dc, dd, ea, eb, ec, ed of the strain body 20 so that the detection direction becomes the extending direction of the arm portion 23. In addition, in each of the positions Aa, ab, ac, ad, ba, bb, bc, bd, fa1, fa2, fb1, fb2, fc1, fc2, fd1, fd2 of the strain body 20, a strain gauge 30 (referred to as a shear strain gauge) that detects shearing of the arm 23 is disposed so that the detection direction becomes 45 ° direction (or 135 ° direction) with respect to the extending direction of the arm 23.

In the arm 23A shown in fig. 9 and 10, strain gauges 30 (bending strain gauges) are arranged one by one at positions Cb2, cc2, ea, eb, and strain gauges 30 (shearing strain gauges) are arranged one by one at positions Bb, bd, fb2, fd2, and a total of 8 are provided. The strain gauges 30 at the positions Cc2, ea, fb2, fd2 are located on the surface 20a (see fig. 9) of the arm 23A, and the positions Cc2 and Ea have a relationship on a center line located in the extending direction of the arm 23A in a plan view, and the positions Fb2 and Fd2 have a symmetrical positional relationship with respect to the center line. The strain gauges 30 at the positions Bb, bd, cb2, eb are located on the rear surface 20b (see fig. 10) of the arm 23A, and the positions Cb2 and Eb have a relationship on the center line of the arm 23A in the extending direction in a plan view, and the positions Bb and Bd have a symmetrical positional relationship with respect to the center line. The strain gauge 30 is similarly arranged in the other 3

arm portions

23B, 23C, and 23D.

In the present embodiment, the strain gauge 30 may be provided only on the

surfaces

20a and 20b of the strain body 20 (arm 23) having no obstacle, instead of providing the strain gauge 30 on the inner side surface 20d of the arm 23. Therefore, the productivity of the force sensor 10B can be improved. In addition, since the strain gauge 30 is not attached to the inner surface 20d of the arm portion 23, the reliability of the force sensor 10B can be improved.

In the present embodiment, for example, a predetermined number (8) of strain gauges 30 (bending strain gauges) provided at positions Ca1, ca2, cb1, cb2, cc1, cc2, cd1, cd2 are used to form one bridge circuit 31 (shown as a bridge circuit 31C in the table of fig. 11) shown in fig. 5. Here, the strain gauge 30 at the position Ca1 and the strain gauge 30 at the position Ca2 are connected in series, corresponding to the position a of the bridge circuit 31 shown in fig. 5. The same applies to other positions Cb1, cb2, cc1, cc2, cd1, cd 2. For example, one bridge circuit 31 shown in fig. 5 (referred to as a bridge circuit 31F in the table of fig. 11) is configured using a predetermined number (8) of strain gauges 30 (shear strain gauges) provided at the positions Fa1, fa2, fb1, fb2, fc1, fc2, fd1, fd 2. Here, the strain gauge 30 at the position Fa1 and the strain gauge 30 at the position Fa2 are connected in series, corresponding to the position a of the bridge circuit 31 shown in fig. 5. The same applies to other positions Fb1, fb2, fc1, fc2, fd1, fd 2.

As shown in fig. 11, in the force sensor 10B of the present embodiment, when the force Fx is applied to the force receiving portion (the central portion 21), only the unbalanced output is generated in the bridge circuit 31A. When the force Fy is applied to the force receiving portion (the center portion 21), only the bridge circuit 31B generates an unbalanced output. When the force Fz is applied to the force receiving portion (the center portion 21), only the bridge circuit 31C generates an unbalanced output. When the moment Mx is applied to the force receiving portion (the center portion 21), only the bridge circuit 31D generates an unbalanced output. When the moment My is applied to the force receiving portion (the center portion 21), only the bridge circuit 31E generates an unbalanced output. When the moment Mz is applied to the force receiving portion (the center portion 21), only the bridge circuit 31F generates an unbalanced output. That is, according to the force sensor 10B, each component can be detected without performing matrix operation as in embodiment 1 described above.

Although the present invention has been specifically described based on the embodiments, the present invention is not limited to the embodiments described above, and various modifications can be made without departing from the spirit and scope of the invention as described below.

In embodiment 1, a case where the present invention is applied to a 6-axis force sensor is described. However, the present invention is not limited to this, and may be applied to, for example, a force sensor (a force component meter) that detects only a force component in the axial direction of the arm and a moment component around the axis.

Claims

1. A force sensor, comprising:

a strain body having a surface and an interior; and

a plurality of strain gauges provided on the front surface and the rear surface,

the strain body includes: a force receiving portion for receiving force; a fixing part fixed relative to the stress part; an arm portion connecting the force receiving portion and the fixing portion; and a bending portion extending in a direction intersecting the extending direction of the arm portion and connected to the fixing portion, wherein the arm portion is configured to be bent at the force receiving portion side and to be sheared at the bending portion side,

the plurality of strain gauges includes first, second, third and fourth bending strain gauges for detecting bending of the arm, and first, second, third and fourth shearing strain gauges for detecting shearing of the arm,

the strain gauges described above form a bridge circuit,

the first and second bending strain gauges are disposed at positions symmetrical to each other with respect to a center line of the arm or on a center line of the arm at the bending generating portion of the surface,

the third and fourth bending strain gauges are provided at positions symmetrical to each other with respect to a center line of the arm or on a center line of the arm at the inner surface of the bending generating portion,

the first and second shear strain gauges are disposed at positions symmetrical to each other with respect to a center line of the arm at the shear generating portion of the surface,

the third and fourth shear strain gauges are disposed at positions symmetrical to each other with respect to a center line of the arm portion at the rear surface of the shear generating portion.

2. The force sensor of claim 1, wherein,

the detection direction of the first, second, third and fourth bending strain gauges is set as the extending direction of the arm,

the detection directions of the first, second, third, and fourth shear strain gauges are set to be 45 ° with respect to the extending direction of the arm.

3. The force sensor according to claim 1 or 2, wherein,

the first and second bending strain gauges and the first and second shearing strain gauges are assembled together so as to be adhered to the surface of the arm portion,

the third and fourth bending strain gauges and the third and fourth shearing strain gauges are joined together so as to be adhered to the back surface of the arm.

4. The force sensor according to claim 1 or 2, wherein,

a first bridge circuit is formed using the first, second, third and fourth bending strain gauges,

and forming a second bridge circuit by using the first, second, third and fourth shearing strain gauges.

5. The force sensor according to claim 1 or 2, wherein,

the force receiving part and the fixing part are concentric,

the 3 arm portions are arranged at equal intervals in the circumferential direction of the force receiving portion and the fixing portion so as to have a Y-shape in a plan view.

6. The force sensor according to claim 1 or 2, wherein,

the force receiving part and the fixing part are concentric,

the 4 arm portions are disposed at equal intervals in the circumferential direction of the force receiving portion and the fixing portion so as to be cross-shaped in a plan view.

7. The force sensor of claim 4, wherein,

and applying a voltage of 1 to 10V to the first bridge circuit and the second bridge circuit.