JP2017161286A - Strain gauge and force transducer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a strain gauge equipped with a shorting adjustment pattern part that reduces the effect of a resistance value change due to strain deformation.SOLUTION: There is provided a strain gauge equipped with a loopback pattern part for strain detection and a shorting adjustment pattern part for resistance adjustment, where the shorting adjustment pattern part includes a plurality of resistance wirings in which resistors are arranged in parallel and selectively cut off, each resistance wiring forming a line symmetrical shape, with a perpendicular of a line segment linking their start and end points as an axis of symmetry, having at least partly a component in a direction that intersects each of the line segment linking the start and end points and the axis of symmetry, the strain gauge being arranged in a strain body so that the direction of shearing force applied to the strain body and the axis of symmetry are parallel.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a strain gauge affixed to a strain generating portion that is elastically deformed by receiving a force, and a force transducer using the strain gauge.

  Conventionally, a strain gauge used for a force transducer or the like and provided in a strain generating part forms a Wheatstone bridge circuit by a folded pattern part and a terminal part whose resistance value changes when strain is applied, and applies an applied voltage. Thus, a voltage proportional to the strain of the strain generating portion caused by the force applied to the force transducer is output.

  For example, the circuit formation of the strain gauge having the folded pattern portion and the terminal portion is performed by photolithography by laminating a metal foil on an insulating base. For this purpose, it is generally masked with a resist and formed by etching. Actually, each error occurs with respect to the desired pattern size due to image distortion in photolithography, blur, uncertainties of chemicals during development during resist formation, and side etching variations during metal foil etching. The resistance value between the terminals varies. Therefore, in order to create a balanced state of the Wheatstone bridge circuit, it is necessary to adjust the resistance value between the terminal portions. For actual adjustment, for example, a method has been used in which an adjustment pad is provided between the folded pattern portion and the terminal portion, and trimming is performed by laser beam irradiation to adjust the resistance value and maintain the bridge balance.

  For this resistance value adjustment, Patent Document 1 and Patent Document 2 disclose a plurality of resistor wiring patterns arranged in parallel and selectively cut between conductive films.

JP 58-208633 A International Publication No. 2014/107597

  However, the strain gauges disclosed in the inventions of Patent Literature 1 and Patent Literature 2 are a plurality of parallel short circuits that are selectively cut in the same direction as the maximum sensitivity direction of the folded pattern portion having high sensitivity to strain. An adjustment pattern portion is provided. In this way, when a strain gauge that does not particularly consider the arrangement of the short-circuit adjustment pattern portion is used in the force transducer for measuring shear stress, a plurality of parallel resistance wirings in the short-circuit adjustment pattern portion that are selectively cut are provided. When it is thin, the resistance value changes significantly due to strain, and there is a problem in that the sensitivity to strain in the entire strain gauge changes before and after cutting.

  An object of the present invention is to provide a strain gauge in which a short-circuit adjustment pattern portion for performing resistance value adjustment reduces the influence on the sensitivity of strain, and a force transducer using the strain gauge.

The strain gauge according to claim 1 achieves the above-described object,
A folded pattern portion for detecting distortion formed by a resistor;
A strain gauge disposed on a strain-generating body that is deformed by receiving a shearing force with a short-circuit adjustment pattern portion for resistance adjustment,
The short-circuit adjustment pattern unit has a plurality of resistance wirings arranged in parallel and selectively cut,
Each resistance wiring has at least one line-symmetric shape with a perpendicular line segment connecting the start point and the end point of each resistance line as a symmetry axis, and in a direction intersecting the line segment and the symmetry axis line connecting the start point and the end point. Having ingredients at least in part,
The shearing force is applied to the strain generating body so that the direction of the shear force applied to the strain generating body is substantially parallel to the axis of symmetry.

  In order to achieve the above object, the strain gauge according to claim 2 is configured so that the wiring widths of the resistance wirings arranged in parallel include different ones.

  In order to achieve the above-described object, the strain gauge according to claim 3 is configured such that each resistance wiring is at least one of an arc shape and a linear shape, each having a passage point that intersects the symmetry axis. Yes.

  In order to achieve the above-described object, the strain gauge according to claim 4 is configured such that each resistance wiring is formed in an angle of 90 degrees with a point intersecting with the symmetry axis as a passing point, and is linear. .

The force transducer according to claim 5 achieves the above object,
A strain body that deforms under shear force;
It is comprised with the strain gauge as described in any one of Claim 1 to 4 attached to a strain body.

  According to the strain gauge of claim 1, since the plurality of parallel resistance wirings in the short-circuit adjustment pattern portion to be selectively cut are symmetrical about the line parallel to the direction of the shear stress, the shear stress Thus, a strain gauge in which a change in resistance value of the short-circuit adjustment pattern portion is reduced can be realized.

  According to the strain gauge of claim 2, in addition to the above-described effect, by providing a plurality of types of thicknesses of the plurality of parallel resistance wires in the short-circuit adjustment pattern portion to be selectively cut, a resistance adjustment option Strain gauge with increased can be realized.

  According to the strain gauge of claim 3, in addition to the above effect, the shape of the plurality of parallel resistance wirings in the short-circuit adjustment pattern portion to be selectively cut has a degree of freedom. Even so, it is possible to realize a strain gauge provided with a short-circuit adjustment pattern portion that prevents conduction failure due to application of a large stress.

According to the strain gauge of claim 4, in addition to the above-described effect, the plurality of parallel resistance wirings in the short-circuit adjustment pattern portion to be selectively cut are symmetric with an angle of 90 degrees. Since the symmetry axis coincides with the shear stress direction, it is possible to realize a strain gauge in which the resistance value change due to the shear stress of the short-circuit adjustment pattern portion is extremely small.

According to the force transducer of the fifth aspect, a high-accuracy force transducer can be realized by using the strain gauge in which the resistance value change due to the shear stress of the short-circuit adjustment pattern portion is reduced.

It is a top view of the strain gauge which concerns on the 1st Embodiment of this invention. It is a detailed enlarged view of a short circuit adjustment pattern portion of the strain gauge according to the first embodiment of the present invention. It is a detailed enlarged view of a short-circuit adjustment pattern part of a strain gauge according to a second embodiment of the present invention. It is a short circuit adjustment pattern part detailed enlarged view of the strain gauge which concerns on the 3rd Embodiment of this invention. It is a partial cross section perspective view of the force transducer using the strain gauge of the present invention.

  Hereinafter, a strain gauge and a force transducer of the present invention will be described with reference to the accompanying drawings. However, the present invention is not limited to the following embodiments.

  FIG. 1 is a plan view of a strain gauge according to the first embodiment of the present invention. The strain gauge 2 has a resistor pattern formed on a film base material serving as a base, mainly folded pattern portions 201a and 201b for strain detection, and terminal portions 202a and 202b for taking out signals and connecting to a power source. 202c, and short-circuit adjustment pattern portions 203a and 203b for resistance adjustment are provided symmetrically. The strain gauge 2 is formed by providing folded pattern portions 201a and 201b having a maximum sensitivity direction of 90 degrees on one film substrate, and is used as a strain gauge for detecting a shear force, for example. .

  In this embodiment, the film base material used as a base is a polyimide film, for example, and a resistor is a metal and uses the alloy of copper and nickel. If necessary, a polyimide insulating layer may be applied or laminated as a protective layer covering a part of the resistor.

  The short-circuit adjustment pattern portion 203a is a portion that is selectively cut by laser trimming. The cutting position is specified by recognizing the positioning mark 204a and the positioning mark 205a with a camera or the like and determining which line to perform laser trimming and which pattern to cut. The short-circuit adjustment pattern portion 203b is also selectively cut by laser trimming in the same manner as the short-circuit adjustment pattern portion 203a by the positioning mark 204b and the positioning mark 205b.

The laser for laser trimming is a laser having a wavelength suitable for trimming metal, which is a resistor. For example, laser light output from the laser is shaped into a predetermined size by a beam expander, and a galvano scanner is mounted. After that, the laser beam is condensed by the fθ lens and irradiated onto the workpiece to perform laser trimming.

  FIG. 2 is an enlarged detailed view of a portion of the short-circuit adjustment pattern portion 203a of the strain gauge 2 according to the first embodiment of the present invention. The short-circuit adjustment pattern unit 203a is configured by a plurality of resistance wires arranged in parallel. The resistance wiring (straight line) 206c is formed in a straight line in an oblique direction from the start point SP, changes its direction at the passing point PP, becomes a resistance wiring (straight line) 206d, and merges at the end point EP. The passing point PP is on the vertical bisector of the line segment connecting the start point SP and the end point EP, and the resistance wiring (straight line) 206c and the resistance wiring (straight line) 206d are the vertical bisect of the line segment connecting the starting point SP and the end point EP. The symmetric line is symmetrical with respect to the symmetric axis ML. The resistance wiring (straight line) 206c and the resistance wiring (straight line) 206d having the same wiring width are provided in parallel on the upper side of FIG. If the straight line 206e and the resistance wiring (straight line) 206f are arranged in parallel, it is possible to create a variation in resistance value change due to cutting.

  When the strain gauge 2 is arranged on the strain generating body so that the shearing force direction Txy received by the short-circuit adjustment pattern portion 203a is parallel to the symmetry axis ML, the resistance wiring (straight line) 206c is tensile stress, and the resistance wiring (straight line) 206d. Works to be subjected to compressive stress, and the strain detected by both is canceled out. In the first embodiment, since the resistance wiring (straight line) 206c and the resistance wiring (straight line) 206d are provided at an angle of 45 degrees with respect to the shearing force direction Txy, the canceling effect is maximized.

  FIG. 3 is an enlarged detail view of the short-circuit adjustment pattern portion of the strain gauge according to the second embodiment of the present invention. In addition to the first embodiment, the resistance wiring (straight line) 206c and the resistance wiring (straight line) 206d are added with one row of the same pattern. That is, three rows of parallel resistors are provided, and the cutting can be performed twice along the trimming planned line TL, so that the resistance can be adjusted in finer steps. The resistance wiring (straight line) 207c and the resistance wiring (straight line) 207d have the same line width as the resistance wiring (straight line) 206c and the resistance wiring (straight line) 206d. By changing the line width as described above, it is possible to further increase the variation of the resistance value change by cutting.

  FIG. 4 is an enlarged detail view of the short-circuit adjustment pattern portion of the strain gauge according to the third embodiment of the present invention. The resistance wiring (arc) 206g is formed as an arc having a radius R from the start point SP, passes through the passing point PP, and merges at the end point EP at an arc resistance wiring (arc) 206h having the same radius R. The passing point PP is on the perpendicular bisector of the line segment connecting the start point SP and the end point EP, and the resistance wiring (arc) 206g and the resistance wiring (arc) 206h are the vertical bisect of the line segment connecting the start point SP and the end point EP. The symmetric line is symmetrical with respect to the symmetric axis ML. In the case of this arc-shaped pattern, although the shearing force canceling effect is slightly lower than that in the first embodiment, the stress near the passing point PP is relaxed, so that it is used for a strain gauge that receives a large strain. Pattern cutting can be prevented.

  That is, these resistance wirings have a line-symmetric shape with a perpendicular line connecting the start point SP and the end point EP as the symmetry axis ML, and components in directions intersecting with the line segment connecting the start point SP and the end point EP and the symmetry axis ML, respectively. The linear type of the first embodiment and the arc type of the third embodiment may be combined, or the linear type and the arc type are arranged in series. It may be.

  FIG. 5 is a partially sectional perspective view showing an embodiment of a force transducer using a strain gauge of the present invention. The force transducer to which the present invention is applied measures the torque force applied to the rotary shaft 1 such as the torque detector 20, and has a built-in speed reducer that can be connected to a motor (not shown). Here, it is represented by a perspective view of a cut section excluding some members.

  The rotating shaft 1 is connected to a motor (not shown) and transmits power to the load side, and a rotating shaft strain generating portion 1a provided so as to be distorted by twisting is provided in a part thereof, and the rotating shaft flange portion 1b is provided. It is provided in the vicinity of the rotating shaft strain generating portion 1a. The rotary shaft 1 is rotatable by bearings 15 provided on the covers 18 and 19.

  The strain gauge 2 is attached to the cylindrical surface of the rotating shaft strain generating portion 1a, detects the strain of the rotating shaft strain generating portion 1a that is deformed in response to the generation of torque of the rotating shaft 1, and forms a part of the Wheatstone bridge circuit. It is composed. The strain gauges 2 are attached to the cylindrical surface of the rotating shaft strain generating portion 1a so as to be symmetric with respect to the central axis of the rotating shaft 1, and are attached at four positions, and the angle formed by each is 90 degrees.

  The adjustment board 3 is a single wiring board fixed to the rotary shaft flange 1b, has a substantially C shape with a part of an annular shape cut out, and is electrically connected to the strain gauge 2. Has been.

  The rotation-side circuit board 4 has an annular shape, and is fixed to the rotation shaft 1 by a support column 14 standing on the rotation shaft flange 1b in the axial direction of the rotation shaft 1, and the adjustment substrate 3 and 2 described later. Wiring from the secondary coil 13 is made. The rotation-side circuit board 4 includes a power supply rectifier circuit, an amplifier circuit that amplifies an output signal from the Wheatstone bridge circuit, an A / D converter circuit that digitally converts the signal, and a transmission that calculates these and transmits them as a torque value wirelessly The circuit is installed.

  The stationary circuit board 16 is fixed to the cover 18 and arranged to face the rotation circuit board 4, and receives a torque value from the rotation circuit board 4, a circuit that supplies power to the rotation circuit board 4. The receiving circuit has an output circuit for outputting the received torque value to the outside. These circuits mounted on the fixed side circuit board 16 are collectively referred to as a fixed side circuit.

  The primary side core 10 is made of a U-shaped magnetic body having a U-shaped cross section, which is fixed by being fitted into a primary side core holder 17 attached to the fixed side circuit board 16. A primary coil 11 is wound between the protrusions of the primary core 10, and the coil is connected to the fixed circuit board 16.

  On the other hand, the rotary shaft 1 is provided with a secondary core 12 coaxially with the rotary shaft 1, and a secondary coil 13 is wound thereon. The wiring from the secondary coil 13 is made along the support column 14 and connected to the rotating circuit board 4.

The circuit that supplies power to the rotating circuit board 4 in the fixed circuit board 16 is a switching circuit. When the primary coil 11 is energized with the current converted to alternating current, an alternating magnetic field is generated, and this alternating magnetic field rotates. A current is induced in the secondary coil 13 by passing through the shaft-side secondary core 12. The induced current is supplied to the strain gauge 2, the amplification circuit, the A / D conversion circuit, and the transmission circuit in the rotation side circuit board 4 through a rectification circuit provided in the rotation side circuit board 4. With the above mechanism, power is supplied to the rotating shaft 1 side in a non-contact manner.

  In actual torque measurement, when torque is applied to the rotating shaft 1, the rotating shaft strain generating portion 1 a of the rotating shaft 1 is distorted according to the magnitude of the torque, and the magnitude of this strain is the resistance value of the strain gauge 2. As a change, it is output from the Wheatstone bridge circuit unit, amplified by the amplifier circuit of the rotation side circuit board 4, A / D converted and then digitized, and transmitted to the fixed side circuit board 16 as a torque value. The detected distortion is converted into an electric signal.

As described above, since the strain gauge according to the present embodiment includes the short-circuit adjustment pattern portion that reduces the influence of the resistance value change due to the shear strain deformation, the strain gauge has a small influence on the sensitivity of the strain due to the resistance value adjustment. Can be realized. Moreover, it becomes possible to provide a highly accurate force transducer by using this strain gauge.

  The present invention is not limited to the above-described embodiments shown in the drawings and can be applied to a force transducer such as a load cell in which measurement is performed by shear strain deformation, and is within the scope of the gist of the present invention. It is possible to implement in various modifications.

  The present invention can be applied to a force transducer using a strain gauge.

DESCRIPTION OF SYMBOLS 1 Rotating shaft 1a Rotating shaft strain generating part 1b Rotating shaft collar 2 Strain gauge 3 Adjustment board 4 Rotating side circuit board 10 Primary side core 11 Primary side coil 12 Secondary side core 13 Secondary side coil 14 Column 15 Bearing 16 Fixed side circuit board 17 Primary side core holder 18 Cover 19 Cover
20 Torque detector

201a, 201b Folding pattern portions 202a, 202b, 202c Terminal portions 203a, 203b Short-circuit adjustment pattern portions 204a, 204b, 205a, 205b Positioning marks 206c, 206d Resistance wiring (straight line)
207c, 207d, 207e, 207f Resistance wiring (straight line)
206g, 206h Resistance wiring (arc)
207g, 207h Resistance wiring (arc)

SP Start point EP End point PP Passing point TL Trimming planned line ML Symmetry axis Txy Shearing force direction

Claims (5)

A folded pattern portion for detecting distortion formed by a resistor;
A strain gauge disposed on a strain-generating body that is deformed by receiving a shearing force with a short-circuit adjustment pattern portion for resistance adjustment,
The short-circuit adjustment pattern portion has a plurality of resistance wirings arranged in parallel and selectively cut,
Each of the resistance wirings has at least one line-symmetric shape with a perpendicular line that connects a starting point and an ending point of each resistance wiring as a symmetric axis, and a line segment that connects the starting point and the ending point and the symmetric axis line Each having at least a portion of the components in the intersecting direction;
The strain gauge is arranged on the strain body so that the direction of the shear force applied to the strain body and the axis of symmetry are substantially parallel.   The strain gauge according to claim 1, wherein wiring widths of the respective resistance wirings arranged in parallel include different ones.   3. The strain gauge according to claim 1, wherein each of the resistance wirings is at least one of an arc shape and a linear shape, with a point intersecting with the symmetry axis as a passing point.   3. The strain gauge according to claim 1, wherein each of the resistance wirings has an angle of 90 degrees with a point intersecting with the symmetry axis as a passing point, and has a linear shape. 4. A strain body that deforms under shear force;
A force transducer comprising: the strain gauge according to any one of claims 1 to 4 attached to the strain generating body.