JP2014085259A - Strain gauge, strain measuring device and strain gauge type converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a strain gauge, a strain measuring device and a strain gauge type converter capable of suppressing influence of noise and improving the accuracy of measurement with a simple configuration.SOLUTION: A strain gauge 1 includes: a sensor unit 10 having a base part 11 composed of an insulating material and a pattern part 12 composed of a resistive element disposed on one surface side of the base part 11; and a filmy intermediate member 2 having an insulator layer 21 and a shield layer 22 formed by a conductor which is disposed on one side of the insulator layer 21 so as to be opposed to the other surface side of the base part 11 of the sensor unit 10.

Description

  The present invention relates to a strain gauge, a strain measuring apparatus, and a strain gauge transducer that can suppress the influence of disturbance noise when measuring strain of a measurement object using a strain gauge.

  Strain gauges are sensors that detect and detect minute deformations (strains) that occur in metals, etc., by replacing them with electrical signals. It is known as a useful means such as confirmation of strength and safety (for example, Non-Patent Document 1).

  Such a strain gauge is generally configured as shown in FIGS. 9A is a perspective view of a strain gauge, FIG. 9B is a cross-sectional view thereof, and FIG. 10A is a diagram showing a configuration of a strain measuring apparatus using the strain gauge. FIG.10 (b) is explanatory drawing which shows the influence of the noise in a strain gauge measuring apparatus.

  As shown in FIGS. 9A and 9B, the strain gauge (sensing part) 10 is schematically formed on a base part 11 formed of an insulating material and on the base part 11. And a lead wire 13 connected to the pattern portion 12. Moreover, the pattern part 12 is coat | covered with the cover film 18, and the said base part 11 is stuck by the adhesive agent A on the surface of the measuring objects 14, such as a structure.

  As shown in FIG. 10A, the strain gauge 10 is incorporated in a Wheatstone bridge circuit 15, a bridge voltage is applied to the input terminal of the bridge circuit 15 by a bridge power supply unit 17, and an amplifier 16 is connected to the output terminal. Has been.

  In such a configuration, for example, in a state where the strain gauge 10 is adhered to the metal measurement object 14, the base portion 11 of the strain gauge 10 is an insulator (dielectric). A capacitance C is generated between the object 14 to be measured. That is, the pattern portion 12 serves as one electrode and the measurement object 14 serves as the other electrode, and a capacitance C is generated therebetween.

  By the way, the measurement object 14 may be exposed to an electric field, a magnetic field, or an electromagnetic wave. As shown in FIG. 10B, the noise N enters the strain gauge 10 side from the measurement object 14 by the electric field, the magnetic field, or the electromagnetic wave. There are things to do. That is, the noise N is transmitted from the measurement object 14 to the pattern portion 12 of the strain gauge 10 via the capacitance C. In addition, even if the measurement object does not receive noise, noise M may be generated on the side of the amplifier 16 due to wrapping around from another device. In this case, using the amplifier as a reference is equivalent to receiving noise on the measurement object side.

  The strain gauge detects a minute deformation as a change in electric resistance and outputs it as a weak electric signal. The voltage output from the bridge circuit 15 is generally at a level of μV and is extremely small. For this reason, the output voltage is susceptible to noise, and measurement errors and variations are likely to occur.

  For this reason, various countermeasures have been considered in the strain gauge in order to suppress the influence of noise. For example, there has been proposed a shield structure in which an electronic circuit including an amplifier is covered with a metal member to block electromagnetic noise (see Patent Document 1).

Edited by Japan Nondestructive Inspection Association, “Strain Measurement 1”, “Strain Measurement 2”, “Strain Measurement 3”

JP 2010-133736 A

  However, even in the case of the shield structure as described above, when the common terminal of the amplifier is connected to another device, the noise received by the measurement object cannot be suppressed. Furthermore, noise cannot be suppressed even when it is difficult to form a shield structure integrally, such as when the amplifier is away from the measurement object.

  The present invention has been made in view of the above problems, and provides a strain gauge, a strain measurement device, and a strain gauge transducer that can suppress the influence of noise and increase measurement accuracy with a simple configuration. With the goal.

  The strain gauge according to claim 1 includes a sensing portion including a base portion formed of an insulating material, and a pattern portion made of a resistor provided on one surface side of the base portion, and an insulating layer. A thin-film intermediate member provided on one surface side of the insulator layer and a shield layer formed of a conductor disposed opposite to the other surface side of the base portion in the sensitive portion It was characterized by comprising.

The intermediate member is generally interposed between the sensing part and the measurement object. The shield layer can be formed by metal foil, sputtering, or the like, but the formation method and configuration are not particularly limited. What is necessary is just to be formed with the material which has electroconductivity.
According to this invention, it is possible to provide a strain gauge capable of suppressing the influence of noise and increasing the measurement accuracy with a simple configuration.
The strain gauge according to claim 2 is the strain gauge according to claim 1, wherein the sensing part and the intermediate member are integrated.

  According to this invention, a strain gauge having a shield layer can be handled as a single component, and an advantageous effect for handling can be expected without increasing the number of components.

  The strain gauge according to claim 3 is the strain gauge according to claim 1, wherein the intermediate member is attached to the measurement object, and then the sensing part is attached to the shield layer of the intermediate member. Features.

  According to this invention, since the sensitive part and the intermediate member are separated, for example, various patterns of gauges (sensitive part) can be appropriately selected and used, and it is expected to improve adaptability. it can.

  According to a fourth aspect of the present invention, in the strain measuring apparatus, the shield layer in the intermediate member of the strain gauge according to any one of the first to third aspects and the amplifier side to which the output of the sensing part is connected are connected in common. It is characterized by that.

  A strain gauge transducer according to a fifth aspect includes a strain gauge according to any one of the first to third aspects, a measuring object to which the strain gauge is attached, and a strain gauge. And a configured bridge circuit.

  A strain gauge transducer is a device that changes the magnitude of force into an electric signal, and includes a load cell, a pressure sensor, a torque sensor, a displacement sensor, and the like. For example, a measurement object in a load cell corresponds to a so-called strain body. In addition, there are various types of load cells such as a column type and a diaphragm type, but the applicable type is not particularly limited.

  According to the present invention, it is possible to provide a strain gauge, a strain measurement device, and a strain gauge transducer that can suppress the influence of noise and increase the measurement accuracy with a simple configuration.

1 is a schematic perspective view showing a strain gauge according to a first embodiment of the present invention. It is a typical top view which shows the strain gauge. It is a typical sectional view showing the strain gauge. It is a perspective view which decomposes | disassembles and shows the same strain gauge. It is explanatory drawing which shows the structure which suppresses the influence of the noise in the distortion measuring device. Similarly, it is explanatory drawing which shows the structure of another Example. It is a perspective view which shows the strain gauge type converter which concerns on the 2nd Embodiment of this invention, and shows the state by which the strain gauge was affixed on the measuring object (strain body). It is a block block diagram of the distortion measuring device. A general strain gauge (sensitive part) is shown, (a) is a perspective view, and (b) is a sectional view. The strain gauge measuring apparatus using the same strain gauge (sensitive part) is shown, (a) is a block diagram, (b) is explanatory drawing which shows the influence of noise.

  Hereinafter, a strain gauge and a strain measuring apparatus according to a first embodiment of the present invention will be described with reference to FIGS. This embodiment shows a basic embodiment of the present invention.

1 shows a schematic perspective view of the strain gauge, FIG. 2 shows the same plan view, FIG. 3 shows the same sectional view, and FIG. 4 shows the same exploded perspective view. FIG. 5 is an explanatory view showing a configuration for suppressing the influence of noise in the strain measuring apparatus, and FIG. 6 is an explanatory view showing another embodiment.
As shown in FIGS. 1 to 4, the strain gauge 1 includes a sensitive part 10 and an intermediate member 2.

  The sensing part 10 corresponds to a so-called existing strain gauge, a base part 11, a pattern part 12 formed on one surface side of the base part 11, and a lead wire 13 connected to the pattern part 12 and led out. Are formed in a thin film shape.

  The base portion 11 is formed in a substantially rectangular shape by an insulating material, for example, a polyimide resin, and the thickness dimension is about 20 μm. The base portion 11 may be formed of an insulating material such as phenol resin or epoxy resin, and the shape is not limited to a rectangular shape, and may be formed in an arc shape or the like.

  The pattern portion 12 is a resistor formed on one surface side of the base portion 12, that is, on the surface. The pattern portion 12 is continuously folded along the longitudinal direction of the base portion 11 to form a meandering shape, and a pair of lead wire connecting portions 12a is formed on one end portion side. The pattern portion 12 is not limited to being formed in a meandering shape. If a predetermined resistance value is obtained, it may be formed by another pattern.

  Moreover, the pattern part 12 is formed with the metal foil which is a resistance material, for example, is formed with the thickness dimension of about 5 micrometers by the photonicked copper nickel type alloy foil. The resistance value of the pattern portion 12 changes in accordance with the strain generated in the measurement object 14.

The lead wire 13 is connected to the lead wire connecting portion 12a in the pattern portion 12 by soldering or the like. A cover film 18 is provided so as to cover the pattern portion 12 and the lead wire connecting portion 12a. As a material of the cover film 18, a polyimide resin, a polyester resin, or the like can be used.
The intermediate member 2 includes an insulator layer 21 and a shield layer 22 provided on one surface side of the insulator layer 21 and is formed in a thin film shape.

  The insulator layer 21 is formed in, for example, a substantially rectangular shape with polyimide resin, like the base portion 11 in the sensing portion 10, and has a size larger than the base portion 11 and a thickness of about 20 μm. . The insulator layer 21 can be formed of an insulating material such as a phenol resin or an epoxy resin.

  The shield layer 22 is formed of a conductor, specifically, is formed of a thin metal foil having conductivity, and is provided on substantially the entire surface of one surface side of the insulator layer 21. A pair of lead wire connecting portions 22 a to which the lead wires 23 are connected are formed on one end side of the shield layer 22. This lead wire connecting portion 22a is used when connecting the shield layers 22 to each other when a common connection is made with the amplifier 16 side described later or when a plurality of strain gauges 1 are used.

  Specifically, the metal foil of the shield layer 22 is made of a material such as conductive copper, an aluminum alloy, or a nickel alloy, and is attached to the insulator layer 21. The thickness dimension of the shield layer 22 is about 5 μm. The shield layer 22 may be formed in a film shape by sputtering.

  The intermediate member 2 configured as described above has the shield layer 22 disposed so as to face the other surface side of the base portion 11 in the sensing portion 10. Specifically, as representatively shown in FIG. 4 showing a state in which the sensing part 10 and the intermediate member 2 are disassembled, the shield layer 22 side of the intermediate member 2 and the base part 11 in the sensing part 10 A predetermined adhesive is interposed between the surface side and the sensing part 10, thereby being bonded to the intermediate member 2 and integrated. The means for integrating the sensing part 10 and the intermediate member 2 is not limited to the case where an adhesive is used. Other means may be used.

  In a state where the sensing part 10 and the intermediate member 2 are integrated, the region where the shield layer 22 of the intermediate member 2 is formed is opposed to at least the region where the pattern part 12 of the sensing part 10 is formed. At the same time, the lead wire connecting portion 22a protrudes from one end of the sensing portion 10 and extends.

Further, the area _{S 1} of the sensing part 10, the area _{S 2} of the shielding layer 22, the relationship between the area _{S 3} of the insulator layer 21, the area of the area _{S 1} <shielding layer 22 of the sensing part 10 _{S 2} <it becomes the area S ₃ of the insulator layer 21, are sequentially dimension increases. Therefore, by increasing the area S ₃ of the insulator layer 21 can be improved ensuring insulation.

  The strain gauge 1 configured as described above has flexibility and is attached to the surface of the measurement object 14 such as a structure. Specifically, a thermosetting adhesive A is interposed between the insulator layer 21 of the intermediate member 2 and the surface of the measurement object 14, and the strain gauge 1 is attached to the surface of the measurement object 14. The

  Thus, in a state where the strain gauge 1 is adhered to the surface of the measurement object 14, the intermediate member 2 is interposed between the sensing part 10 and the measurement object 14. And if distortion arises in the measuring object 14, the distortion will be transmitted to the pattern part 12 of the sensitive part 10 via the intermediate member 2, and the resistance value of the pattern part 12 will change according to distortion.

  In addition, in the above-mentioned strain gauge 1, although the perception part 10 and the intermediate member 2 were integrated previously, and the case where this was affixed on the measuring object 14 was demonstrated, the perception part 10 and the intermediate member 2 exist. The strain gauge 1 may be separated. In this case, as shown with reference to FIG. 4, first, the intermediate member 2 is attached to the measurement object 14, and then the sensing part 10 is attached from the intermediate member 2. The shield layer 22 is disposed so as to face the other surface side of the base portion 11 in the sensing portion 10.

  As described above, the strain gauge 1 can be configured by combining the intermediate member 2 with the existing sensing part 10. In addition, when the sensing part 10 and the intermediate member 2 are integrated, the strain gauge 1 can be handled as a single component, which is advantageous for handling without increasing the number of components.

  On the other hand, when the sensitive part 10 and the intermediate member 2 are separated, by preparing the intermediate member 2 suitable for the dimensions of various types of strain gauges (sensitive part), various A pattern gauge (sensitive part 10) can be appropriately selected and used, and adaptability can be improved.

  The strain gauge 1 of the present embodiment as described above is attached to the surface of various structures or machines, or attached to a measurement object (straining body) of a load cell as a strain gauge transducer. Can be used.

  Next, the block configuration of the strain measuring apparatus will be described with reference to FIG. The figure shows a part of the block configuration of the strain measuring apparatus and shows a configuration for suppressing the influence of noise.

  The present embodiment is based on the one-gauge two-wire method, and a Wheatstone bridge circuit 15 composed of the strain gauge 1 and the fixed resistance element R using the strain gauge, and a pair of bridge circuits 15. And an amplifier 16 connected to the output terminal.

  The shield layer 22 of the intermediate member 2 in the strain gauge 1 and the amplifier 16 are connected in common by a lead wire 23. Specifically, the lead wire connecting portion 22 a of the shield layer 22 and the common terminal of the amplifier 16 are connected by the lead wire 23.

  An outline of the operation of the strain measuring apparatus configured as described above will be described. In the state where the strain gauge 1 is attached to the measurement object 14, if strain occurs in the measurement object 14, the resistance value of the pattern portion 12 of the sensing unit 10 changes and is weak at the output end of the bridge circuit 15. A measurement signal voltage is output. This measurement signal voltage is amplified by the amplifier 16.

  In this case, as in the case described above with reference to FIGS. 9 and 10, noises N and M may be generated on the measurement object 14 or the amplifier 16 side. However, in this embodiment, since the strain gauge 1 and the amplifier 16 are connected in common by the lead wire 23, even if the noises N and M enter, the strain gauge 1 and the amplifier 16 are at the same potential. Therefore, it can suppress that a measured value is influenced by noise N and M. That is, the influence of noise can be suppressed and the measurement accuracy can be increased.

As shown in FIG. 6, the shield layer 22 of the intermediate member 2 in the strain gauge 1 may be grounded and grounded. In this case, the noise N that enters from the measurement object 14 flows through the lead wire 23 to the ground line, and can prevent the noise N from entering the strain gauge 1. It is possible to suppress the influence and increase the measurement accuracy.
Moreover, the format of the strain measuring device of the present embodiment is not limited to a specific one.

  Next, a strain measuring apparatus according to a second embodiment of the present invention will be described with reference to FIGS. In this embodiment, the strain gauge 1 as described above is applied to a load cell 5 as a strain gauge type transducer.

  FIG. 7 is a perspective view showing a state in which a strain gauge is attached to a strain generating body as a measurement object, and FIG. 8 shows a part of a block diagram of the strain measuring device. In addition, the same code | symbol is attached | subjected to the part which is the same as that of 1st Embodiment, or an equivalent part, and the overlapping description is abbreviate | omitted.

  As shown in FIG. 7, the strain body as the measurement object 14 is made of metal and is formed in a substantially cylindrical shape. Four strain gauges 1 are alternately arranged in the vertical direction and the horizontal direction at substantially equal intervals on the cylindrical peripheral surface. That is, the four strain gauges 1 are attached so that the ones positioned in the vertical direction and the ones positioned in the horizontal direction face each other, and the four sensing parts 10 (G1 to G4) are used. Yes.

  As shown in FIG. 8, this embodiment is based on a 4-gauge method, and the Wheatstone bridge circuit 15 is comprised by each sensing part 10 (G1-G4). As described above, the load cell 5 includes the strain generating body of the measurement object 14, the strain gauge 1, and the Wheatstone bridge circuit 15 built in a case (not shown).

  Further, the shield layer 22 of the intermediate member 2 in each strain gauge 1 is connected to each other by a lead wire 23b, and further, the shield layer 22 of the intermediate member 2 in a specific one strain gauge 1 (lower left in FIG. 8). Side) and the amplifier 16 are connected in common by a lead wire 23a.

As described in the first embodiment, the strain gauge 1 in which the sensing part 10 and the intermediate member 2 are separated may be applied. Further, the shield layer 22 of the intermediate member 2 in the strain gauge 1 may be grounded and grounded.
As described above, according to this embodiment, similarly to the first embodiment, it is possible to suppress the influence of noise and increase the measurement accuracy.

  The present invention is not limited to the configuration of each of the embodiments described above, and various modifications can be made without departing from the spirit of the invention. The above embodiments are presented as examples, and are not intended to limit the scope of the invention.

  For example, in the above-described embodiment, the case where the sensitive part uses an existing strain gauge has been described, but this does not prevent the newly designed and manufactured sensitive part from being used. Moreover, the 1 gauge method, the 2 gauge method, the 4 gauge method, etc. can be applied to the connection method of the sensing part, and the special connection method is not limited.

DESCRIPTION OF SYMBOLS 1 ... Strain gauge 2 ... Intermediate member 5 ... Strain gauge type converter (load cell)
DESCRIPTION OF SYMBOLS 10 ... Sensitive part 11 ... Base part 12 ... Pattern part 12a ... Strain gauge lead wire connection part 13, 23 ... Lead wire 14 ... Measurement object 15 ... Wheatstone Bridge circuit 16 ... Amplifier 21 ... Insulator layer 22 ... Shield layer 22a ... Lead wire connecting portion A of intermediate member ... Adhesive N ... Noise M ... Noise

Claims (5)

A sensing part comprising a base part made of an insulating material and a pattern part made of a resistor provided on one surface side of the base part;
A thin film comprising an insulator layer, and a shield layer formed of a conductor provided on one surface side of the insulator layer and disposed opposite to the other surface side of the base portion in the sensing part An intermediate member of
A strain gauge characterized by comprising:   The strain gauge according to claim 1, wherein the sensing part and the intermediate member are integrated.   The strain gauge according to claim 1, wherein the intermediate member is attached to the measurement object, and then the sensitive part is attached to the shield layer of the intermediate member.   4. The strain measuring apparatus according to claim 1, wherein the shield layer of the intermediate member of the strain gauge according to any one of claims 1 to 3 and the amplifier side to which the output of the sensing part is connected are connected in common. A strain gauge according to any one of claims 1 to 3,
A measuring object to which the strain gauge is attached;
A bridge circuit configured using a strain gauge;
A strain gauge type transducer characterized by comprising:

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