CN110857896A - Force sensor - Google Patents
Force sensor Download PDFInfo
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- CN110857896A CN110857896A CN201810908703.2A CN201810908703A CN110857896A CN 110857896 A CN110857896 A CN 110857896A CN 201810908703 A CN201810908703 A CN 201810908703A CN 110857896 A CN110857896 A CN 110857896A
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- strain
- force
- strain gauges
- force sensor
- arm portion
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L5/00—Apparatus for, or methods of, measuring force, work, mechanical power, or torque, specially adapted for specific purposes
- G01L5/16—Apparatus for, or methods of, measuring force, work, mechanical power, or torque, specially adapted for specific purposes for measuring several components of force
- G01L5/161—Apparatus for, or methods of, measuring force, work, mechanical power, or torque, specially adapted for specific purposes for measuring several components of force using variations in ohmic resistance
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L1/00—Measuring force or stress, in general
- G01L1/20—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress
- G01L1/22—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress using resistance strain gauges
- G01L1/225—Measuring circuits therefor
- G01L1/2262—Measuring circuits therefor involving simple electrical bridges
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- General Physics & Mathematics (AREA)
- Force Measurement Appropriate To Specific Purposes (AREA)
Abstract
The invention provides a force sensor. Provided is a technique capable of improving the productivity and reliability of a force sensor. A force sensor (10) is provided with: a strain body (20) having a front surface (20a) and a back surface (20 b); and a plurality of strain gauges (30) provided on the front surface (20a) and the back surface (20 b). The strain body (20) is configured to include: a force receiving portion (21) for receiving a force; a fixing portion (22) fixed to the force receiving portion; an arm (23) connecting the force receiving portion and the fixing portion; and a bending part (24) extending in a direction intersecting the extending direction of the arm part and connected to the fixing part. The plurality of strain gauges (30) are provided on the arm section (23), and include a bending strain gauge for detecting bending of the arm section (23) and a shear strain gauge for detecting shearing of the arm section (23). The strain gauges form a bridge circuit.
Description
Technical Field
The present invention relates to a force sensor (also referred to as a force resolver), and more particularly, to a technique effective for a 6-axis force sensor suitable for detecting 6 components in total of force components in an x-axis direction, a y-axis direction, and a z-axis direction and moment components around each axis.
Background
Jp 57-169643 a (hereinafter referred to as "patent document 1") describes a technique relating to a multi-component force-measuring instrument using a strain gauge. This force component meter is a configuration in which the shape of an arm portion having a cross shape in a plan view connecting a base portion and a frame body is examined, and an external force is measured based on only a bending strain (see lines 12 to 16 on the upper left of the third page of the specification of patent document 1). Therefore, in order to detect external forces in each direction by bending strain, 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 (see the third page of the specification of patent document 1, upper right 19 th row-lower left 3 rd row).
Patent document 1: japanese laid-open patent publication No. 57-169643
As in the technique described in patent document 1, a conventional force-dividing gauge is configured to measure an external force based on a bending strain of an arm portion by devising a shape of the arm portion, so that the external force can be captured by the bending strain while suppressing a shear strain generated in the arm portion. This is because the force-dividing meter is considered to be a member that detects and detects a minute change (output) due to an external force, and is effective for detecting and detecting a bending strain that generates a change larger than a shear strain.
However, in the technique described in patent document 1, although it is easy to attach (adhere) the strain gauge to the front surface and the rear surface of the arm portion of the quadrangular prism (the surface formed by 4 arm portions in a cross shape in a plan view), it is difficult to attach the strain gauge to 2 side surfaces (surfaces orthogonal to the upper and lower surfaces) of the arm portion. This is because the space on the side surface side of the arm portion, that is, the space surrounded by the base portion, the frame body, and the arm portion is narrow (has an obstacle) when the strain gauge is attached. Therefore, the number of working steps increases when the strain gauge is attached to the 2-side surface (inner surface) of the arm portion. In addition, the wiring layout of the strain gauge is also difficult, and operation failure 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 and reliability of a force sensor. 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 problem, a force sensor as a solving means of the present invention includes: a strain body having a surface and an inside; 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 a force; a fixing portion fixed to the force receiving portion; an arm portion connecting the force receiving portion and the fixing portion; and a bending portion extending in a direction intersecting an extending direction of the arm portion and connected to the fixing portion, wherein the plurality of gauges include a predetermined number of bending gauges for detecting bending of the arm portion and a predetermined number of shear gauges for detecting shearing of the arm portion, and the gauges constitute a bridge circuit.
Thus, the strain gauge is not provided on the side surface (surface orthogonal to the front surface and the back surface) of the arm portion, and the strain gauge is provided only on the front surface and the back surface of the arm portion of the strain body. Therefore, the productivity of the force sensor can be improved. Further, since there is no problem caused by the strain gauge being attached to the side surface of the arm portion, the reliability of the force sensor can be improved.
In the force sensor of the above-described solving means, it is more preferable that the bending strain gauge is arranged such that a detection direction of the bending strain gauge is set to an extending direction of the arm portion, and the shear strain gauge is arranged such that the detection direction of the shear strain gauge is set to a direction of 45 ° with respect to the extending direction of the arm portion.
In the force sensor according to the above-described solution, it is more preferable that a predetermined number of the bending strain gauges and a predetermined number of the shear strain gauges be combined so as to be attached to the front surface and the rear surface of the arm portion. This can improve productivity as compared with attaching the strain gauges one by one.
In the force sensor of the above-described solution, it is more preferable that the first bridge circuit is configured by using a predetermined number of the bending strain gauges, and the second bridge circuit is configured by using a predetermined number of the shearing strain gauges. Although the arm portion is bent (flexed), sheared, and twisted by the force, the arm portion is connected to the arrangement of a predetermined number of strain gauges to form a bridge circuit, and thus, for example, the bending (flexing) and twisting occurring in the arm portion are eliminated, and the stress due to shearing can be detected.
In the force sensor according to the above-described solving means, it is preferable that the force receiving portion and the fixing portion are formed concentrically, and 3 arm portions are arranged at equal intervals in a circumferential direction of the force receiving portion and the fixing portion so as to form a Y shape in a plan view. When the number of arm portions is as small as 3, the number of strain gauges provided on the strain body as a whole is reduced, and the number of steps for attaching the strain gauges is reduced, whereby productivity can be improved, and production cost can be reduced.
Or more preferably, the force receiving portion and the fixing portion are formed concentrically, and 4 arm portions are arranged at equal intervals in the circumferential direction of the force receiving portion and the fixing portion so as to form a cross shape in plan view. In a 6-axis force sensor in which 3 arm portions are formed in a Y shape in plan view, in order to detect force components in the x-axis direction, the Y-axis direction, and the z-axis direction and moment components around the respective axes by 6 components in total, it is necessary to perform matrix operation on outputs of strain gauges provided in the respective arm portions. In this regard, in a 6-axis force sensor in which 4 arms are formed into a cross shape in a plan view, each component can be detected without performing matrix operation.
In the force sensor of the above-mentioned solution, it is preferable that a voltage of 1 to 10V is applied to the first bridge circuit and the second bridge circuit. A voltage of 1-10V is applied to a bridge circuit formed on an arm portion, so that stress caused by shearing can be easily and accurately detected.
According to the present invention, the productivity of the force sensor can be improved, and the reliability can be improved.
Drawings
Fig. 1 is a schematic plan view of a main part of a force sensor according to embodiment 1 of the present invention.
Fig. 2 is a schematic plan view of the inside of the main part of the force sensor shown in fig. 1.
Fig. 3 is a schematic perspective view of a main part of the force sensor shown in fig. 1.
Fig. 4 is a configuration 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 detection table of a bridge circuit included in the force sensor shown in fig. 1.
Fig. 7 is a schematic plan view of a main part of a force sensor according to embodiment 2 of the present invention.
Fig. 8 is a schematic plan view of the back side of the main part of the force sensor shown in fig. 7.
Fig. 9 is a schematic plan view of a main part of a force sensor according to embodiment 3 of the present invention.
Fig. 10 is a schematic plan view of the back surface of the main part 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 body; 20a … surface; 20b …; 20c … outer side; 20d … medial side; 21 … central part (force-receiving part); 22 … frame portion (fixed portion); 23. 23A, 23B, 23C, 23D … arm portions; 24 … elastic portion; 30 … strain gauge; 31. 31A, 31B, 31C, 31D, 31E, 31F … bridge circuit; 32 … integral measuring instrument; 40 … signal processing section.
Detailed Description
In the following embodiments of the present invention, although a plurality of portions are described as necessary, they are not independent from each other in principle, and some or all of the modifications of one and the other have a detailed relationship. Therefore, in all the drawings, the same reference numerals are given to members having the same functions, and redundant description thereof will be omitted. The number of the constituent elements (including the number, numerical value, amount, range, and the like) is not limited to a specific number, and may be equal to or larger than a specific number or smaller than a specific number, except when the number is specifically indicated or when the number is clearly limited to a specific number in principle. In addition, when a shape such as a component is referred to, the shape includes a similar or similar matter to the shape or the like in reality, except for a case where the shape is specifically indicated and a case where it is considered that the shape is obviously not in principle.
(embodiment mode 1)
In embodiment 1 of the present invention, a force sensor (also referred to as a motion sensor such as an acceleration sensor or an angular velocity sensor if the sensor detects an inertial force) suitable for detecting (measuring) at least one component of the magnitude or direction of a force applied to an object will be described. Specifically, a 6-axis force sensor that can simultaneously detect 6 total components of a force component in the 3-axis direction and a moment component around the 3-axis direction in an orthogonal coordinate system (x-axis, y-axis, and z-axis) in a three-dimensional space will be described.
The force sensor 10 of the present embodiment is described with reference to fig. 1 to 6. Fig. 1 and 2 are schematic plan views of main parts 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 when a force is applied, and a plurality of strain gauges 30 that detect the strain of the strain body 20. Fig. 4 is a configuration 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 detection table 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 output signals thereof are 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 on the opposite side of the first surface), that is, 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 formed concentrically 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. More specifically, each portion of the strain body 20 has a disc-like shape in the central portion 21, an annular frame portion 22, and a quadrangular prism-like shape in the arm portion 23.
In the present embodiment, the arm portions 23 are arranged at equal intervals in the circumferential direction of the central portion 21 and the frame portion 22 (every 120 ° in the circumferential direction of the center O) so as to form a Y shape in a 3-piece plan view. That is, 3 arm portions 23(23A, 23B, 23C) extend radially from the center O between the central portion 21 and the frame portion 22. The strain body 20 includes an elastic portion 24 (bent 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 form 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 aluminum alloy, alloy steel, or stainless steel, using an NC (Numerical Control) machine, for example. Thus, the strain body 20 forms a space (through portion) for forming the central portion 21, the frame portion 22, and the arm portion 23, and a space (through portion in a narrow slit shape in a plan view) for forming the elastic portion 24. By forming these spaces, the strain body 20 has an inner surface 20d (a surface perpendicular to the front surface 20a and the inner surface 20b, an inner wall surface of the penetrating portion) in addition to the outer surface 20 c.
In the force sensor 10 of the present embodiment, the strain body 20 uses the central portion 21 as a force receiving portion that receives a force, the frame portion 22 as a fixing portion that is fixed to the force receiving portion, and the arm portion 23 as a portion that generates a strain. That is, the strain body 20 is configured to generate bending (bending), shearing, and twisting of the arm portion 23 by a force. That is, bending (flexure) 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 force receiving portion and the fixing portion of the strain body 20 may use the central portion 21 as the fixing portion and the frame portion 22 as the force receiving portion.
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 deformation body 20, the arm portions 23B and 23C are deformed by applying a force thereto, and the arm portion 23A is not strained because the elastic portion 24 is bent. When a force Fy in the y-axis direction is applied, the arm portions 23A, 23B, and 23C are deformed by applying a force thereto. When a force Fz in the z-axis direction is applied, the arm portions 23A, 23B, and 23C are uniformly deflected. When the moment Mx in the x-axis direction is applied, only twisting occurs in the arm portion 23A, and the arm portions 23B and 23C are not deflected. When the moment My in the y-axis direction is applied, the arm portions 23A, 23B, and 23C are respectively subjected to a moment and are deflected. When the moment Mz in the z-axis direction is applied, the arm portions 23A, 23B, and 23C are uniformly deflected.
In the strain body 20, the 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 flexible polyimide or epoxy resin film can be used to cover 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. The 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 receiving the strain of the arm portion 23. In addition, 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, the method of mounting the strain gauge 30 without using adhesive may be such that the thin metal film gauge is directly formed on the front surface 20a and the rear surface 20b of the strain body 20 by vacuum deposition or sputtering.
In the present embodiment, the strain gauge 30 is provided in the arm portion 23 so that the detection direction (sensing direction) thereof is the same as the generation direction of bending (deflection) or the generation direction of shearing in 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, strain gauges 30 (referred to as bending strain gauges) for detecting bending (flexure) of the arm portions 23 are disposed at positions Aa, Ab, Ac, Ad, Ba, Bb, Bc, Bd, Ca, Cb, Cc, and Cd of the strain body 20 so that the detection direction is the extending direction of the arm portions 23. Further, at each of the positions Da, Db, Dc, Dd, Ea, Eb, Ec, Ed, Fa, Fb, Fc, and Fd of the strain body 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 ° direction (or 135 ° direction) with respect to the extending direction of the arm portion 23. Even if the same strain gauge 30 is used among the plurality of strain gauges 30, the strain gauges may include a bending strain gauge and a shearing strain gauge depending on the arrangement of the detection direction.
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 side of the center portion 21, and a predetermined number (four) of strain gauges 30 (shearing strain gauges) are arranged one by one at positions Ea to Ed on the side of the frame portion 22, and a total of 8 strain gauges 30 are provided. The strain gauges 30 at the positions Ba, Bc, Ea, and Eb are located on the surface 20a (see fig. 1) of the strain body 20 (arm 23A), and the position Ba and the position Bc are in a symmetrical relationship, and the position Ea and the position Eb are in a symmetrical relationship, with respect to the center line of the extension direction of the arm 23A in a plan view. Therefore, the detection direction of strain gauge 30 at position Ba and the detection direction of strain gauge 30 at position Bc are in parallel, and the detection direction of strain gauge 30 at position Ea and the detection direction of strain gauge 30 at position Eb intersect on the center line of arm 23A. The strain gauges 30 at the positions Bb, Bd, Ec, and Ed are located on the back surface 20b (see fig. 2) of the strain body 20 (arm portion 23A), and the position Bb and the position Bd are in a symmetrical relationship, and the position Ec and the position Ed are in 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 Bb and the detection direction of the strain gauge 30 at the position Bd are in parallel, 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 intersect on the center line of the arm portion 23A. In addition, the strain gauge 30 is similarly disposed in the other 2 arm portions 23B and 23C.
In the present embodiment, one bridge circuit 31 (bridge circuit 31A shown in the table of fig. 6) shown in fig. 5 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 (bridge circuit 31D shown in the table of fig. 6) shown in fig. 5 is configured by a predetermined number (four) of strain gauges 30 (shear strain gauges) provided at the positions Da to Dd, for example. The bridge circuit 31 shown in fig. 5 has strain gauges 30 disposed at positions a, b, c, and d, and is electrically connected (wired).
Specifically, the series connected strain gauges 30 at the positions a and d and the series connected strain gauges 30 at the positions b and c are connected in parallel 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 to the output signal Vo. In the bridge circuit 31 to which the input signal Vi of a voltage of 1 to 10V is applied, for example, the output signal Vo changes when the resistance value of the strain gauge 30 changes to become unbalanced. Although the arm portion 23 is bent (flexed), sheared, and twisted by the force, in the present embodiment, the bridge circuit 31 constituting the strain gauge 30 has a disturbance removing function and a temperature securing function, and eliminates the bending (flexing) and twisting when, for example, a stress due to shearing is detected. The stress due to shearing can be accurately detected by applying a voltage of 1-10V.
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 relationship, the position symbols a, b, c, d (lower case letters) of the bridge circuit 31 and the position symbols Aa, Ab, Ac, Ad of the strain body 20 are respectively associated with the 2 nd (lower case letters). The bridge circuit 31 including the strain gauges 30 provided at the positions Aa to Ad of the strain body 20 corresponds to a detection table of the bridge circuit 31A shown in fig. 6. In this way, in order to clarify the correspondence relationship, the symbol (upper case letter) of the bridge circuit 31A in fig. 6 is associated with the 1 st (upper case letter) of the position symbols Aa, Ab, Ac, Ad of the straining 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 the forces Fx, Fy, Fz and the 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 strain gauges 30 at 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), and Fa to Fd (bridge circuit 31F) of the strain body 20 are set to "+" when the resistance value increases, to "-" when the resistance value decreases, and to "0" when the resistance value does not change. The output signals Vo of the bridge circuits 31A to F are set to "1" when unbalanced output of the bridge occurs, and set to "0" when unbalanced output does not occur.
Here, the signal processing unit 40 that calculates the force acting on the force receiving portion (the center portion 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 unit 40 are electrically connected by wiring. In the signal processing unit 40, signals (analog signals) from the bridge circuits 31A to 31F (CH1 to CH6) are amplified by the amplifiers 41(AMP1 to AMP6), and the analog signals are converted into digital signals by the a/D converter 42 and transmitted to the CPU 43. By using the amplifier 41 in this way, even a shear strain with a weak output can be detected.
The CPU43 refers to the calibration matrix (correction matrix) from the memory 44 and calculates 6 components (Fx, Fy, Fz, Mx, My, Mz) of the force acting on the force receiving portion (central portion 21). The result of the signal processing unit 40 can be output from the CPU43 as a digital signal, and can also be output as an analog signal using the D/a converter 45.
The signal processing unit 40 thus has a calibration function of correcting with reference to the output signals Vo from the bridge circuits 31A to 31F. As shown in the following equation, the force F acting on the force receiving portion (central 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.
[ formula 1]
F＝C×V…(1)
[ formula 2]
F＝[FXFYFZMXMYMZ]T…(2)
[ formula 3]
[ formula 4]
V＝[V1V2V3V4V5V6]T…(4)
The calibration matrix C is calculated in advance as a matrix unique to each force sensor 10. Specifically, the calibration matrix C can be calculated from the condition under which the rated load of 6 components is applied to the force sensor 10 and the detection result of the deformation amount of the strain body 20 at that time. Since such a calibration matrix C is used, 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 surface 20d of the arm portion 23, and the strain gauge 30 can be provided only on the surfaces 20a and 20b of the strain body 20 (arm portion 23) having no obstacle. Therefore, it is not necessary to provide the strain gauge 30 in a narrow space surrounded by the central portion 21, the frame portion 22, and the arm portion 23, and therefore, the productivity of the force sensor 10 can be improved. Further, since there is no problem (e.g., disconnection) caused by the strain gauge 30 being stuck 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, in the case where the number of strain gauges 30 provided in the strain body 20 is small as in the present embodiment in which 3 arm portions 23 are provided for 4 strain gauges, the number of steps for attaching the strain gauges 30 is also small, and the productivity of the force sensor 10 can be improved. In addition, the production cost of the force sensor 10 can also be reduced.
(embodiment mode 2)
In embodiment 1, the case where the strain gauges 30 are attached to the arm portions 23, respectively, has been described. In embodiment 2 of the present invention, a case where an integrated measuring instrument 32 configured by integrating a predetermined number of strain gauges 30 is attached to the arm portion 23 will be described with reference to fig. 7 and 8. Fig. 7 and 8 are schematic plan views of main parts of the force sensor 10A.
The force sensor 10A of the present embodiment includes a sheet-like integrated measuring instrument 32 in which a predetermined number of strain gauges 30 are integrated so as to be attached to the front surface 20A (see fig. 7) and the rear surface 20B (see fig. 8) of each arm portion 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 integrated measuring instrument 32 attached to the front surface 20a of the arm portion 23A includes four strain gauges 30 (bending strain gauges) at positions Ba and Bc and four strain gauges 30 (shear strain gauges) at positions Ea and Eb in total. The integrated measuring instrument 32 attached to the rear surface 20b of the arm portion 23A includes four strain gauges 30 (bending strain gauges) at positions Bb and Bd and four strain gauges 30 (shear strain gauges) at positions Ec and Ed in total. The other 2 arm portions 23B and 23C are similarly bonded with the integral gauge 32.
By using such an integrated measuring instrument 32, productivity can be improved as compared with attaching the strain gauges 30 one by one. After the integrated measuring instrument 32 is attached to each arm portion 23, each strain gauge 30 is electrically connected to constitute each bridge circuit 31A to 31F (see fig. 5 and 6).
(embodiment mode 3)
In embodiment 1, the case where the 3 arm portions 23 are configured to have a Y-shape in plan view has been described. In embodiment 3 of the present invention, a case where the 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 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 center portion 21 having a circular shape as the force receiving portion and the annular frame portion 22 as the fixed portion are configured to be concentric, and the 4 quadrangular prism-shaped arm portions 23 are arranged at equal intervals in the circumferential direction of the center portion 21 and the frame portion 22 (every 90 ° in the circumferential direction of the center O) so as to form a cross shape in a plan view. That is, 4 arm portions 23(23A, 23B, 23C, 23D) extend radially from the center O between the central portion 21 and the frame portion 22. The strain body 20 includes an elastic portion 24 (bent 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 substantially absorbs the axial strain of the arm portion 23. 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 form a T shape in plan view. That is, the strain body 20 of the force sensor 10B is configured to generate bending (bending), shearing, and twisting of the arm portion 23 by a force.
In the present embodiment, the strain gauge 30 is provided in the arm portion 23 so that the detection direction (sensing direction) thereof is the same as the generation direction of bending (deflection) or the generation direction of shearing in 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, in each of the positions Ca1, Ca2, Cb1, Cb2, Cc1, Cc2, Cd1, Cd2, Da, Db, Dc, Dd, Ea, Eb, Ec, and Ed of the strain body 20, a strain gauge 30 (referred to as a bending strain gauge) for detecting bending (deflection) of the arm portion 23 is disposed so that the detection direction is the extending direction of the arm portion 23. Further, in each of the positions Aa, Ab, Ac, Ad, Ba, Bb, Bc, Bd, Fa1, Fa2, Fb1, Fb2, Fc1, Fc2, Fd1, and Fd2 of the strain body 20, a strain gauge 30 (referred to as a shear strain gauge) for detecting shear of the arm portion 23 is disposed so that the detection direction is 45 ° to the extending direction of the arm portion 23 (or 135 ° direction).
In the arm portion 23A shown in fig. 9 and 10, the strain gauges 30 (bending strain gauges) are disposed one by one at positions Cb2, Cc2, Ea, Eb, and the strain gauges 30 (shear strain gauges) are disposed one by one at positions Bb, Bd, Fb2, Fd2, and a total of 8 strain gauges are provided. Strain gauges 30 at positions Cc2, Ea, Fb2, and Fd2 are located on surface 20a of arm portion 23A (see fig. 9), and position Cc2 and position Ea have a relationship located on a center line in the extending direction of arm portion 23A in a plan view, and position Fb2 and position 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 back surface 20b (see fig. 10) of the arm portion 23A, the position Cb2 and the position Eb have a relationship of being located on a center line in the extending direction of the arm portion 23A in a plan view, and the position Bb and the position Bd have a symmetrical positional relationship with respect to the center line. The strain gauge 30 is similarly disposed 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 portion 23) having no obstacle, instead of the strain gauge 30 provided on the inner surface 20d of the arm portion 23. Therefore, the productivity of the force sensor 10B can be improved. Further, since there is no problem caused by sticking the strain gauge 30 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, and Cd2 are used to form one bridge circuit 31 (bridge circuit 31C shown in the table of fig. 11) shown in fig. 5. Here, the strain gauge 30 at position Ca1 and the strain gauge 30 at position Ca2 are connected in series, and correspond to position a of the bridge circuit 31 shown in fig. 5. The same applies to other positions Cb1, Cb2, Cc1, Cc2, Cd1 and Cd 2. One bridge circuit 31 (bridge circuit 31F shown in the table of fig. 11) shown in fig. 5 is configured by using a predetermined number (8) of strain gauges 30 (shear strain gauges) provided at positions Fa1, Fa2, Fb1, Fb2, Fc1, Fc2, Fd1, and Fd2, for example. 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 a force Fx is applied to the force receiving portion (the central portion 21), an unbalanced output is generated only in the bridge circuit 31A. When the force Fy is applied to the force receiving portion (the central portion 21), an unbalanced output is generated only in the bridge circuit 31B. When the force Fz is applied to the force receiving portion (the central portion 21), an unbalanced output is generated only in the bridge circuit 31C. When the moment Mx is applied to the force receiving portion (the central portion 21), an unbalanced output is generated only in the bridge circuit 31D. When the moment My is applied to the force receiving portion (the center portion 21), an unbalanced output is generated only in the bridge circuit 31E. When the moment Mz is applied to the force receiving portion (the central portion 21), an unbalanced output is generated only in the bridge circuit 31F. That is, according to the force sensor 10B, each component can be detected without performing matrix operation as in embodiment 1.
While the present invention has been specifically described above based on the embodiments, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the 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 can be applied to, for example, a force sensor (a force-dividing gauge) that detects only a force component in the axial direction of the arm portion and a moment component around the axis.
Claims (7)
1. A force sensor is characterized by comprising:
a strain body having a surface and an inside; and
a plurality of strain gauges disposed on the surface and the inner surface,
the strain body includes: a force receiving portion for receiving a force; a fixing portion fixed to the force receiving portion; an arm portion connecting the force receiving portion and the fixing portion; and a bent portion extending in a direction intersecting with an extending direction of the arm portion and connected to the fixing portion,
the plurality of strain gauges include a predetermined number of bending strain gauges for detecting bending of the arm portion and a predetermined number of shear strain gauges for detecting shearing of the arm portion,
the strain gauges form a bridge circuit.
2. The force sensor of claim 1,
the bending strain gauge is configured such that a detection direction of the bending strain gauge is set to an extending direction of the arm portion,
the shear strain gauge is arranged such that the detection direction of the shear strain gauge is set to be 45 ° with respect to the extending direction of the arm portion.
3. The force sensor of claim 1 or 2,
and a predetermined number of the bending strain gauges and a predetermined number of the shear strain gauges are combined so as to be attached to the front surface and the back surface of the arm portion.
4. The force sensor of any of claims 1-3,
a first bridge circuit is configured using a predetermined number of the above-described bending strain gauges,
the second bridge circuit is configured by using a predetermined number of shear strain gauges.
5. The force sensor according to any one of claims 1 to 4,
the force receiving part and the fixing part are formed concentrically,
the 3 arm portions are arranged in a Y shape in plan view at equal intervals in the circumferential direction of the force receiving portion and the fixing portion.
6. The force sensor according to any one of claims 1 to 4,
the force receiving part and the fixing part are formed concentrically,
the 4 arm portions are arranged at equal intervals in the circumferential direction of the force receiving portion and the fixing portion so as to form a cross shape in plan view.
7. The force sensor of any of claims 4-6,
applying a voltage of 1-10V to the first bridge circuit and the second bridge circuit.
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| CN201810908703.2A CN110857896B (en) | 2018-08-10 | 2018-08-10 | Force sensor |
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| CN201810908703.2A CN110857896B (en) | 2018-08-10 | 2018-08-10 | Force sensor |
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| CN110857896B (en) | 2023-05-02 |
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