JP2023157950A - Strain gauge, sensor module, and bearing mechanism - Google Patents

Abstract

To provide a strain gauge capable of accurately detecting strain in multiple directions.SOLUTION: A strain gauge disclosed herein comprises a flexible substrate, and a plurality of resistors linearly formed on one surface of the substrate, the resistors being configured to cross each other in a same plane.SELECTED DRAWING: Figure 1

Description

The present invention relates to a strain gauge, a sensor module, and a bearing mechanism.

2. Description of the Related Art Strain gauges that are attached to an object to be measured to detect strain in the object are known. A strain gauge includes a resistor that detects strain, and the resistor is formed on a base material made of, for example, an insulating resin.

It is also possible to detect strain in multiple directions by stacking a plurality of strain gauges so that their grid directions intersect (for example, see Patent Document 1).

JP2016-31326A

However, when a plurality of strain gauges are stacked such that their grid directions intersect with each other, measurement errors occur due to positional deviations during stacking.

The present invention has been made in view of the above points, and an object of the present invention is to provide a strain gauge that can accurately detect strain in multiple directions.

The present strain gauge has a flexible base material and a plurality of resistance parts formed in a straight line on one side of the base material, and each of the resistance parts intersects on the same plane. are conductive to each other.

According to the disclosed technology, it is possible to provide a strain gauge that can accurately detect strain in multiple directions.

FIG. 2 is a plan view illustrating a strain gauge according to the first embodiment. FIG. 1 is a cross-sectional view illustrating a strain gauge according to a first embodiment. FIG. 7 is a schematic diagram illustrating a sensor module according to a second embodiment. FIG. 7 is a schematic diagram illustrating a method of using a sensor module according to a second embodiment. FIG. 7 is a plan view illustrating a strain gauge according to a third embodiment. FIG. 7 is a schematic diagram illustrating a sensor module according to a fourth embodiment. FIG. 7 is a perspective view illustrating a bearing mechanism according to a fifth embodiment. FIG. 7 is a cross-sectional view illustrating a bearing mechanism according to a fifth embodiment.

Hereinafter, embodiments for carrying out the invention will be described with reference to the drawings. In each drawing, the same components are given the same reference numerals, and redundant explanations may be omitted.

<First embodiment>
FIG. 1 is a plan view illustrating a strain gauge according to a first embodiment. FIG. 2 is a cross-sectional view illustrating the strain gauge according to the first embodiment, and shows a cross section taken along line AA in FIG. Referring to FIGS. 1 and 2, the strain gauge 1 includes a base material 10, a resistor 30 (resistance parts 31 and 32), and terminal parts 41, 42, 43, and 44.

In this embodiment, for convenience, in the strain gauge 1, the side on which the resistor 30 of the base material 10 is provided is referred to as the upper side or one side, and the side on which the resistor 30 is not provided is referred to as the lower side or the other side. side. Further, the surface on the side where the resistor 30 of each part is provided is defined as one surface or the top surface, and the surface on the side where the resistor 30 is not provided is defined as the other surface or the bottom surface. However, the strain gauge 1 can be used upside down or placed at any angle. In addition, plan view refers to the object viewed from the normal direction of the upper surface 10a of the base material 10, and planar shape refers to the shape of the object viewed from the normal direction to the upper surface 10a of the base material 10. shall be.

The base material 10 is an insulating member that serves as a base layer for forming the resistor 30 and the like, and has flexibility. The thickness of the base material 10 is not particularly limited and can be appropriately selected depending on the purpose, and may be, for example, about 5 μm to 500 μm. In particular, it is preferable that the thickness of the base material 10 is 5 μm to 200 μm, since the strain sensitivity error of the resistor 30 can be reduced.

The base material 10 is made of, for example, PI (polyimide) resin, epoxy resin, PEEK (polyetheretherketone) resin, PEN (polyethylene naphthalate) resin, PET (polyethylene terephthalate) resin, PPS (polyphenylene sulfide) resin, polyolefin resin, etc. It can be formed from an insulating resin film. Note that the film refers to a member having a thickness of about 500 μm or less and having flexibility.

Here, "formed from an insulating resin film" does not prevent the base material 10 from containing fillers, impurities, etc. in the insulating resin film. The base material 10 may be formed, for example, from an insulating resin film containing filler such as silica or alumina.

However, if the base material 10 does not need to have flexibility, the base material 10 may contain SiO ₂ , ZrO ₂ (including YSZ), Si, Si ₂ N ₃ , Al ₂ O ₃ (including sapphire). , ZnO, perovskite ceramics (CaTiO ₃ , BaTiO ₃ ), and the like may be used.

The resistor 30 is a thin film formed in a predetermined pattern on the base material 10, and is a sensing portion that causes a change in resistance when subjected to strain. The resistor 30 may be formed directly on the upper surface 10a of the base material 10, or may be formed on the upper surface 10a of the base material 10 via another layer.

The resistor 30 includes resistance parts 31 and 32. That is, the resistor 30 is a general term for the resistors 31 and 32, and is referred to as the resistor 30 when there is no need to particularly distinguish between the resistors 31 and 32. In addition, in FIG. 1, the resistance parts 31 and 32 are shown in a satin pattern for convenience.

The resistance section 31 is a thin film formed in a straight line on the upper surface 10a of the base material 10 with its longitudinal direction facing the X direction. The resistance portion 32 is a thin film formed in a straight line with its longitudinal direction facing the Y direction. The resistance portion 31 and the resistance portion 32 are orthogonal to each other on the same plane and are electrically connected to each other. For example, the resistive portion 31 and the resistive portion 32 can be patterned so as to intersect each other approximately at the center in the longitudinal direction.

The resistor 30 can be formed of, for example, a material containing Cr (chromium), a material containing Ni (nickel), or a material containing both Cr and Ni. That is, the resistor 30 can be formed from a material containing at least one of Cr and Ni. Examples of materials containing Cr include a Cr mixed phase film. Examples of materials containing Ni include Cu--Ni (copper nickel). An example of a material containing both Cr and Ni is Ni--Cr (nickel chromium).

Here, the Cr mixed phase film is a film in which Cr, CrN, Cr ₂ N, etc. are mixed in phase. The Cr mixed phase film may contain inevitable impurities such as chromium oxide.

The thickness of the resistor 30 is not particularly limited and can be appropriately selected depending on the purpose, and may be, for example, about 0.05 μm to 2 μm. In particular, it is preferable that the thickness of the resistor 30 is 0.1 μm or more, since the crystallinity of the crystal forming the resistor 30 (for example, the crystallinity of α-Cr) is improved. Further, it is more preferable that the thickness of the resistor 30 is 1 μm or less, since cracks in the film constituting the resistor 30 due to internal stress and warpage from the base material 10 can be reduced. The width of the resistor 30 is not particularly limited and can be appropriately selected depending on the purpose, and may be, for example, about 0.1 μm to 1000 μm (1 mm).

For example, when the resistor 30 is a Cr mixed phase film, the stability of the gauge characteristics can be improved by using α-Cr (alpha chromium), which is a stable crystalline phase, as the main component. Furthermore, since the resistor 30 has α-Cr as its main component, the gauge factor of the strain gauge 1 is 10 or more, and the gauge factor temperature coefficient TCS and resistance temperature coefficient TCR are within the range of -1000 ppm/°C to +1000 ppm/°C. It can be done. Here, the term "main component" means that the target substance occupies 50% by mass or more of all the materials constituting the resistor, but from the viewpoint of improving gauge characteristics, the resistor 30 contains 80% by weight of α-Cr. It is preferable to include the above. Note that α-Cr is Cr having a bcc structure (body-centered cubic lattice structure).

The terminal portion 41 extends from one end of the resistor portion 31, and is formed into a substantially circular shape with a wider width than the resistor portion 31 in plan view. The terminal portion 43 extends from the other end of the resistance portion 31, and is formed in a substantially circular shape with a wider width than the resistance portion 31 in plan view. The terminal parts 41 and 43 are a pair of electrodes for outputting to the outside a change in the resistance value of the resistance part 31 caused by strain, and are connected to, for example, a flexible substrate for external connection, a lead wire, or the like. The upper surfaces of the terminal parts 41 and 43 may be coated with a metal that has better solderability than the terminal parts 41 and 43. Note that although the resistive portion 31 and the terminal portions 41 and 43 are given different symbols for convenience, both can be integrally formed using the same material in the same process. Note that the planar shape of the terminal portions 41 and 43 is not limited to a circular shape, but may be a rectangular shape or the like.

The terminal portion 42 extends from one end of the resistor portion 32, and is formed into a substantially circular shape with a wider width than the resistor portion 32 in plan view. The terminal portion 44 extends from the other end of the resistance portion 32, and is formed in a substantially circular shape with a wider width than the resistance portion 32 in plan view. The terminal parts 42 and 44 are a pair of electrodes for outputting to the outside a change in the resistance value of the resistance part 32 caused by strain, and are connected to, for example, a flexible substrate for external connection, a lead wire, or the like. The upper surfaces of the terminal parts 42 and 44 may be coated with a metal that has better solderability than the terminal parts 42 and 44. Note that although the resistor portion 32 and the terminal portions 42 and 44 are given different symbols for convenience, both can be integrally formed from the same material in the same process. Note that the planar shape of the terminal portions 42 and 44 is not limited to a circular shape, but may be rectangular or the like.

A cover layer 60 (insulating resin layer) may be provided on the upper surface 10a of the base material 10 so as to cover the resistor 30 and expose the terminal portions 41 to 44. Providing the cover layer 60 can prevent mechanical damage to the resistor 30. Further, by providing the cover layer 60, the resistor 30 can be protected from moisture and the like. Note that the cover layer 60 may be provided so as to cover the entire portion except the terminal portions 41 to 44.

The cover layer 60 can be formed from an insulating resin such as a PI resin, an epoxy resin, a PEEK resin, a PEN resin, a PET resin, a PPS resin, or a composite resin (eg, a silicone resin or a polyolefin resin). The cover layer 60 may contain filler or pigment. The thickness of the cover layer 60 is not particularly limited and can be appropriately selected depending on the purpose, and may be, for example, about 2 μm to 30 μm.

In the strain gauge 1, the resistance section 31 can detect the strain in the X direction as a change in resistance value, and output it from the terminal sections 41 and 43, which are a pair of electrodes. Further, the resistance section 32 can detect the strain in the Y direction as a change in resistance value, and output it from the terminal sections 42 and 44, which are a pair of electrodes.

However, as shown in FIG. 1, the resistance part 31 and the resistance part 32 are orthogonal on the same plane as an example, and the resistance part 31 and the resistance part 32 are formed in a straight line and are on the same plane. It is sufficient if they intersect. In this case, the resistance section 31 and the resistance section 32 can detect strain in each longitudinal direction. For example, the resistance section 31 can be formed in a straight line with its longitudinal direction facing the X direction, and the resistance section 32 can be formed in a straight line with its longitudinal direction inclined at 45 degrees with respect to the X direction.

Note that based on the strain detected by the resistance section 31 and the strain detected by the resistance section 32, the strain in a direction different from the longitudinal direction of the resistance sections 31 and 32 can be determined by calculation.

In order to manufacture the strain gauge 1, first, the base material 10 is prepared, and the planar resistor 30 and terminal parts 41 to 44 shown in FIG. 1 are formed on the upper surface 10a of the base material 10. The materials and thicknesses of the resistor 30 and the terminal portions 41 to 44 are as described above. The resistor 30 and the terminal portions 41 to 44 can be integrally formed of the same material.

The resistor 30 and the terminal parts 41 to 44 can be formed by, for example, forming a film by magnetron sputtering using a raw material capable of forming the resistor 30 and the terminal parts 41 to 44 as a target, and patterning it by photolithography. The resistor 30 and the terminal parts 41 to 44 may be formed using a reactive sputtering method, a vapor deposition method, an arc ion plating method, a pulsed laser deposition method, or the like instead of the magnetron sputtering method.

From the viewpoint of stabilizing the gauge characteristics, before forming the resistor 30 and the terminal parts 41 to 44, a film with a thickness of about 1 nm to 100 nm is deposited as a base layer on the upper surface 10a of the base material 10 by, for example, conventional sputtering. It is preferable to form the functional layer in vacuum. Note that the functional layer is patterned into the planar shape shown in FIG. 1 together with the resistor 30 and the terminal sections 41 to 44 by photolithography after forming the resistor 30 and the terminal sections 41 to 44 on the entire upper surface of the functional layer.

In the present application, the functional layer refers to a layer that has a function of promoting crystal growth of at least the upper layer of the resistor 30. Preferably, the functional layer further has a function of preventing oxidation of the resistor 30 due to oxygen and moisture contained in the base material 10 and a function of improving the adhesion between the base material 10 and the resistor 30. The functional layer may further include other functions.

Since the insulating resin film constituting the base material 10 contains oxygen and moisture, especially when the resistor 30 contains Cr, Cr forms a self-oxidation film, so the functional layer has the function of preventing oxidation of the resistor 30. It pays to be prepared.

The material of the functional layer is not particularly limited as long as it has the function of promoting at least the crystal growth of the resistor 30, which is the upper layer, and can be selected as appropriate depending on the purpose. For example, Cr (chromium), Ti ( Titanium), V (vanadium), Nb (niobium), Ta (tantalum), Ni (nickel), Y (yttrium), Zr (zirconium), Hf (hafnium), Si (silicon), C (carbon), Zn ( Zinc), Cu (copper), Bi (bismuth), Fe (iron), Mo (molybdenum), W (tungsten), Ru (ruthenium), Rh (rhodium), Re (rhenium), Os (osmium), Ir ( One or more types selected from the group consisting of iridium), Pt (platinum), Pd (palladium), Ag (silver), Au (gold), Co (cobalt), Mn (manganese), and Al (aluminum). Mention may be made of metals, alloys of any of the metals in this group, or compounds of any of the metals in this group.

Examples of the above-mentioned alloy include FeCr, TiAl, FeNi, NiCr, and CrCu. Further, examples of the above-mentioned compounds include TiN, TaN, Si ₃ N ₄ , TiO ₂ , Ta ₂ O ₅ , SiO ₂ and the like.

The functional layer can be formed into a vacuum film by, for example, a conventional sputtering method using a raw material capable of forming the functional layer as a target and introducing Ar (argon) gas into a chamber. By using the conventional sputtering method, the functional layer is formed while etching the upper surface 10a of the base material 10 with Ar, so that the amount of the functional layer formed can be minimized and an effect of improving adhesion can be obtained.

However, this is an example of a method for forming the functional layer, and the functional layer may be formed by other methods. For example, before forming the functional layer, the upper surface 10a of the base material 10 is activated by plasma treatment using Ar or the like to obtain an effect of improving adhesion, and then the functional layer is formed into a vacuum film by magnetron sputtering. You may also use the method of

The combination of the material of the functional layer and the materials of the resistor 30 and the terminal parts 41 to 44 is not particularly limited and can be selected as appropriate depending on the purpose. For example, it is possible to use Ti as the functional layer and to form a Cr mixed phase film containing α-Cr (alpha chromium) as the main component as the resistor 30 and the terminal portions 41 to 44.

In this case, for example, the resistor 30 and the terminal portions 41 to 44 can be formed by magnetron sputtering using a raw material capable of forming a Cr mixed phase film as a target and introducing Ar gas into a chamber. Alternatively, the resistor 30 and the terminal portions 41 to 44 may be formed by reactive sputtering using pure Cr as a target and introducing an appropriate amount of nitrogen gas together with Ar gas into the chamber.

In these methods, the growth plane of the Cr mixed phase film is defined by the functional layer made of Ti, and it is possible to form a Cr mixed phase film mainly composed of α-Cr, which has a stable crystal structure. Furthermore, the gauge characteristics are improved by diffusing Ti constituting the functional layer into the Cr mixed phase film. For example, the gauge factor of the strain gauge 1 can be set to 10 or more, and the gauge factor temperature coefficient TCS and resistance temperature coefficient TCR can be in the range of -1000 ppm/°C to +1000 ppm/°C. Note that when the functional layer is formed of Ti, the Cr mixed phase film may contain Ti or TiN (titanium nitride).

Note that when the resistor 30 is a Cr mixed-phase film, the functional layer made of Ti has the function of promoting crystal growth of the resistor 30 and the function of preventing oxidation of the resistor 30 due to oxygen and moisture contained in the base material 10. , and the function of improving the adhesion between the base material 10 and the resistor 30. The same holds true when Ta, Si, Al, or Fe is used instead of Ti as the functional layer.

In this way, by providing a functional layer below the resistor 30, it becomes possible to promote the crystal growth of the resistor 30, and it is possible to manufacture the resistor 30 having a stable crystalline phase. As a result, in the strain gauge 1, the stability of the gauge characteristics can be improved. Further, by diffusing the material constituting the functional layer into the resistor 30, the gauge characteristics of the strain gauge 1 can be improved.

After forming the resistor 30 and the terminal portions 41 to 44, a cover layer 60 covering the resistor 30 and exposing the terminal portions 41 to 44 is provided on the upper surface 10a of the base material 10 as necessary, so that the strain gauge 1 is completed. The cover layer 60 is, for example, laminated with a semi-cured thermosetting insulating resin film on the upper surface 10a of the base material 10 so as to cover the resistor 30 and expose the terminal parts 41 to 44, and then harden by heating. It can be manufactured by The cover layer 60 is made by applying a liquid or paste thermosetting insulating resin to the upper surface 10a of the base material 10 so as to cover the resistor 30 and exposing the terminal parts 41 to 44, and then heating and hardening the resin. You may also create one.

In this way, in the strain gauge 1, the resistance parts 31 and 32 are each formed in a straight line, intersect on the same plane, and are electrically connected to each other. Accordingly, by sequentially connecting the resistive parts 31 and 32 to the bridge circuit, it is possible to detect the strain in the longitudinal direction of each of the resistive parts 31 and 32 based on the change in the resistance value of the resistive parts 31 and 32. . That is, the strain gauge 1 can realize a multi-axis gauge that can detect strain in two directions.

Conventionally, when detecting strain in two directions, for example, two strain gauges were fabricated and stacked on top of each other so that their grid directions intersect. Differences in the position of the strain gauges in the stacking direction caused measurement errors. On the other hand, in the strain gauge 1, the resistance parts 31 and 32 are patterned simultaneously on the same surface, so the manufacturing process can be simplified and measurement errors due to positional deviation etc. can be made less likely to occur.

Furthermore, in the strain gauge 1, since the resistance parts 31 and 32 are patterned on the same surface, the strain gauge 1 can be made smaller than a structure in which a plurality of strain gauges are pasted together. As a result, it can be easily attached to a desired measurement position.

In addition, in the strain gauge 1, especially when the resistor 30 is formed from a Cr mixed phase film, the sensitivity of the resistance value to strain is lower than when the resistor 30 is formed from Cu-Ni or Ni-Cr. (The amount of change in the resistance value of the resistor 30 with respect to the same strain) is significantly improved. When the resistor 30 is formed from a Cr mixed-phase film, the sensitivity of the resistance value to strain is approximately 5 to 10 times that when the resistor 30 is formed from Cu-Ni or Ni-Cr. . Therefore, by forming the resistor 30 from a Cr mixed phase film, it becomes possible to detect strain with high accuracy.

<Second embodiment>
In the second embodiment, an example of a sensor module in which a selection circuit is mounted on the strain gauge of the first embodiment is shown. Note that in the second embodiment, descriptions of components that are the same as those in the already described embodiments may be omitted.

FIG. 3 is a schematic diagram illustrating a sensor module according to the second embodiment. In FIG. 3, the strain gauge 1 (see FIGS. 1 and 2) is simplified and only the terminal portions 41 to 44 are illustrated.

Referring to FIG. 3, the sensor module 5 includes a strain gauge 1 and a selection circuit 2.

The selection circuit 2 includes, for example, switches SW ₁ and SW ₂ , input terminals I ₁ to I ₄ , output terminals O ₁ and O ₂ , a control terminal CNT, and power supply terminals VDD and VSS (positive terminal and negative terminal). It is an IC equipped with the following. Power at a predetermined voltage is supplied to the power terminals VDD and VSS from outside the sensor module 5. The control terminal CNT and the output terminals O ₁ and O ₂ can be electrically connected to the outside of the sensor module 5 . The selection circuit 2 can be mounted, for example, on the upper surface 10a side or the lower surface 10b side of the base material 10 of the strain gauge 1.

In the selection circuit 2, input terminals I ₁ and I ₃ are connected to terminal portions 41 and 43, which are a pair of electrodes of the resistance portion 31. Furthermore, the input terminals I ₂ and I ₄ are connected to terminal portions 42 and 44, which are a pair of electrodes of the resistance portion 32.

The switches SW ₁ and SW ₂ are switches that are switched in conjunction with each other according to an H/L signal input from the outside to the control terminal CNT.

For example, when an H signal is input from the outside to the control terminal CNT, SW ₁ connects the input terminal I ₁ and the output terminal O ₁ , and SW ₂ connects the input terminal I ₃ and the output terminal O ₂ ( state shown in FIG. 3). In this case, the output terminals O ₁ and O ₂ are connected to terminal sections 41 and 43, which are a pair of electrodes of the resistance section 31, and the resistance value of the resistance section 31 can be measured via the output terminals O ₁ and O ₂ . Become.

On the other hand, when an L signal is input from the outside to the control terminal CNT, SW ₁ connects input terminal I ₂ and output terminal O ₁ , and SW ₂ connects input terminal I ₄ and output terminal O ₂ . In this case, the output terminals O ₁ and O ₂ are connected to terminal sections 42 and 44, which are a pair of electrodes of the resistance section 32, and the resistance value of the resistance section 32 can be measured via the output terminals O ₁ and O ₂ . Become.

FIG. 4 is a schematic diagram illustrating how to use the sensor module according to the second embodiment. Referring to FIG. 4, the sensor module 5 can be connected to a measuring section 7 placed outside the sensor module 5.

The measurement section 7 includes a bridge circuit 71, an analog front end section 72, and a control section 73.

The bridge circuit 71 includes fixed resistors R ₁ , R ₂ , and R ₃ on three sides, and the other side is connected to the output terminals O ₁ and O ₂ of the selection circuit 2 of the sensor module 5 . Further, a DC voltage V is applied between a pair of diagonal points of the bridge circuit 71. With this configuration, between the other pair of diagonal points of the bridge circuit 71, an analog voltage corresponding to the distortion of the resistor section 31 or 32 selected in the selection circuit 2 is output. The voltage output from the bridge circuit 71 is input to the analog front end section 72.

Note that although here, the connection between the strain gauge 1 and the bridge circuit 71 is a 1-gauge, 2-wire type, the connection is not limited to this.

The analog front end section 72 includes, for example, an amplifier, an analog/digital conversion circuit (A/D conversion circuit), an external communication function (for example, a serial communication function such as I ² C), and the like. The analog front end section 72 may include a temperature compensation circuit. The analog front-end section 72 may be implemented as an IC or may be constructed from individual parts.

In the analog front end section 72, the voltage output from the bridge circuit 71 is amplified by an amplifier, and then converted into a digital signal by an A/D conversion circuit and output. If the analog front end section 72 includes a temperature compensation circuit, a temperature compensated digital signal is output.

The control unit 73 can input an H signal or an L signal to the control terminal CNT of the selection circuit 2 of the sensor module 5 to switch the switches SW ₁ and SW ₂ . The control unit 73 can be configured to include, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), a main memory, and the like.

In this case, various functions of the control unit 73 can be realized by reading a program recorded in a ROM or the like into the main memory and executing it by the CPU. However, part or all of the control unit 73 may be realized only by hardware. Further, the control unit 73 may be physically configured by a plurality of devices.

In this way, the switches SW ₁ and SW ₂ of the selection circuit 2 can be switched by an H signal or an L signal input from the outside to the control terminal CNT of the selection circuit 2 of the sensor module 5. Thereby, the resistance value of the resistance part 31 and the resistance value of the resistance part 32 of the strain gauge 1 can be selectively measured. That is, strain in the X direction and strain in the Y direction can be selectively measured.

<Third embodiment>
The third embodiment shows an example of a strain gauge in which the number of strain detection directions is increased compared to the first embodiment. Note that, in the third embodiment, descriptions of the same components as those in the already described embodiments may be omitted.

FIG. 5 is a plan view illustrating a strain gauge according to the third embodiment. Note that the cross-sectional shape of the strain gauge according to the third embodiment is the same as that in FIG. 2, so illustration thereof is omitted. Referring to FIG. 5, the strain gauge 1A differs from the strain gauge 1 (see FIGS. 1 and 2) in that the number of pairs of a resistor portion and a pair of terminal portions is increased from two to four. That is, the strain gauge 1A is a multi-axis gauge that can detect strain in four directions.

In the strain gauge 1A, the resistor 30A is a thin film formed in a predetermined pattern on the base material 10, and is a sensitive part that causes a resistance change in response to strain. The resistor 30A may be formed directly on the upper surface 10a of the base material 10, or may be formed on the upper surface 10a of the base material 10 via another layer. The material, thickness, manufacturing method, etc. of the resistor 30A can be the same as those of the resistor 30.

The resistor 30A includes resistance parts 31, 32, 33, and 34. That is, the resistor 30A is a general term for the resistors 31, 32, 33, and 34, and is referred to as the resistor 30A when there is no need to distinguish between the resistors 31, 32, 33, and 34. In addition, in FIG. 5, 31, 32, 33, and 34 are shown in a satin pattern for convenience.

The resistance section 31 is a thin film formed in a straight line on the upper surface 10a of the base material 10 with its longitudinal direction facing the X direction. The resistance portion 32 is a thin film formed in a straight line with its longitudinal direction facing the Y direction. The resistance section 33 is a thin film formed on the upper surface 10a of the base material 10 in a straight line in a direction in which an angle θ ₁ between the longitudinal direction and the X direction is -45 degrees. The resistance portion 34 is a thin film formed in a straight line on the upper surface 10a of the base material 10 in a direction in which an angle θ ₂ between the longitudinal direction and the X direction is +45 degrees. Note that counterclockwise rotation is defined as a positive angle here.

The resistance parts 31, 32, 33, and 34 cross each other on the same plane and are electrically connected to each other. The resistor parts 31, 32, 33, and 34 can be patterned, for example, so that they intersect at substantially the center in the longitudinal direction. That is, the resistance parts 31, 32, 33, and 34 are each formed in a straight line, intersect on the same plane, and are electrically connected to each other, and the angle between adjacent resistance parts is 45 degrees.

The terminal portion 45 extends from one end of the resistance portion 33, and is formed in a substantially circular shape with a wider width than the resistance portion 33 in plan view. The terminal portion 47 extends from the other end of the resistance portion 33, and is formed in a substantially circular shape with a wider width than the resistance portion 33 in plan view. The terminal parts 45 and 47 are a pair of electrodes for outputting a change in the resistance value of the resistance part 33 caused by strain to the outside, and are connected to, for example, a flexible substrate for external connection, a lead wire, or the like. The upper surfaces of the terminal parts 45 and 47 may be coated with a metal that has better solderability than the terminal parts 45 and 47. Note that although the resistive portion 33 and the terminal portions 45 and 47 are given different symbols for convenience, they can be integrally formed using the same material in the same process. Note that the planar shape of the terminal portions 45 and 47 is not limited to a circular shape, but may be a rectangular shape or the like.

The terminal portion 46 extends from one end of the resistor portion 34, and is formed in a substantially circular shape with a wider width than the resistor portion 34 in plan view. The terminal portion 48 extends from the other end of the resistance portion 34, and is formed into a substantially circular shape with a wider width than the resistance portion 34 in plan view. The terminal parts 46 and 48 are a pair of electrodes for outputting to the outside a change in the resistance value of the resistance part 34 caused by strain, and are connected to, for example, a flexible substrate for external connection, a lead wire, or the like. The upper surfaces of the terminal parts 46 and 48 may be coated with a metal that has better solderability than the terminal parts 46 and 48. Note that although the resistor portion 34 and the terminal portions 46 and 48 are given different symbols for convenience, they can be integrally formed using the same material in the same process. Note that the planar shape of the terminal portions 46 and 48 is not limited to a circular shape, but may be a rectangular shape or the like.

A cover layer 60 (insulating resin layer) may be provided on the upper surface 10a of the base material 10 so as to cover the resistor 30A and expose the terminal portions 41 to 48. Providing the cover layer 60 can prevent mechanical damage to the resistor 30A. Further, by providing the cover layer 60, the resistor 30A can be protected from moisture and the like. Note that the cover layer 60 may be provided so as to cover the entire portion except the terminal portions 41 to 48.

In the strain gauge 1A, the resistance section 31 can detect the strain in the X direction as a change in resistance value, and can output it from the terminal sections 41 and 43, which are a pair of electrodes. Further, the resistance section 32 can detect the strain in the Y direction as a change in resistance value, and output it from the terminal sections 42 and 44, which are a pair of electrodes. The resistance section 33 can detect the strain in the direction in which the angle θ ₁ with the X direction is -45 degrees as a change in resistance value, and output it from the terminal sections 45 and 47, which are a pair of electrodes. The resistance section 34 can detect the strain in the direction in which the angle θ ₂ with the X direction is +45 degrees as a change in resistance value, and output it from the terminal sections 46 and 48, which are a pair of electrodes.

In this way, in the strain gauge 1A, the resistance parts 31, 32, 33, and 34 are each formed in a straight line, intersect on the same plane, and are electrically connected to each other. is 45 degrees. As a result, by sequentially connecting the resistor parts 31, 32, 33, and 34 to the bridge circuit, the resistor parts 31, 32, 33, and and 34 can be detected. Further, based on the detection results of the strains in the resistance sections 31, 32, 33, and 34, the magnitude and direction of the principal strain can be calculated. Other effects are similar to those of the first embodiment.

<Fourth embodiment>
The fourth embodiment shows an example of a sensor module in which a selection circuit is mounted on the strain gauge of the third embodiment. Note that, in the fourth embodiment, descriptions of the same components as those of the already described embodiments may be omitted.

FIG. 6 is a schematic diagram illustrating a sensor module according to the fourth embodiment. In FIG. 6, the strain gauge 1A (see FIG. 5) is simplified and only the terminal portions 41 to 48 are illustrated.

Referring to FIG. 6, the sensor module 5A includes a strain gauge 1A and a selection circuit 2A.

The selection circuit 2A includes, for example, switches SW ₁ and SW ₂ , input terminals I ₁ to I ₈ , output terminals O ₁ and O ₂ , control terminals CNT ₁ and CNT ₂ , power terminals VDD and VSS (positive terminal and a negative electrode terminal). Power at a predetermined voltage is supplied to the power terminals VDD and VSS from outside the sensor module 5A. The control terminals CNT ₁ and CNT ₂ and the output terminals O ₁ and O ₂ can be electrically connected to the outside of the sensor module 5A. The selection circuit 2A can be mounted, for example, on the upper surface 10a side or the lower surface 10b side of the base material 10 of the strain gauge 1A.

In the selection circuit 2A, input terminals I ₁ and I ₅ are connected to terminal portions 41 and 43, which are a pair of electrodes of the resistance portion 31. Furthermore, the input terminals I ₂ and I ₆ are connected to terminal portions 42 and 44, which are a pair of electrodes of the resistance portion 32. Further, the input terminals I ₃ and I ₇ are connected to terminal portions 45 and 47, which are a pair of electrodes of the resistance portion 33. Further, the input terminals I ₄ and I ₈ are connected to terminal portions 46 and 48, which are a pair of electrodes of the resistance portion 34.

The switches SW ₃ and SW ₄ are switches that are switched in conjunction with each other according to the combination of H/L signals that are externally input to the control terminals CNT ₁ and CNT ₂ .

For example, when an H signal is input from the outside to the control terminal CNT ₁ and an H signal is input from the outside to the control terminal CNT ₂ , SW ₃ connects the input terminal I ₁ and the output terminal O ₁ , and SW ₄ connects the input terminal I ₅ and the output terminal _O2 (the state shown in FIG. 6). In this case, the output terminals O ₁ and O ₂ are connected to terminal sections 41 and 43, which are a pair of electrodes of the resistance section 31, and the resistance value of the resistance section 31 can be measured via the output terminals O ₁ and O ₂ . Become.

Also, when an H signal is input from the outside to the control terminal CNT ₁ and an L signal is input from the outside to the control terminal CNT ₂ , SW ₃ connects the input terminal I ₂ and the output terminal O ₁ , and SW ₄ connects the input terminal I ₆ and the output terminal _O2 . In this case, the output terminals O ₁ and O ₂ are connected to terminal sections 42 and 44, which are a pair of electrodes of the resistance section 32, and the resistance value of the resistance section 32 can be measured via the output terminals O ₁ and O ₂ . Become.

Further, when an L signal is input from the outside to the control terminal CNT ₁ and an H signal is input from the outside to the control terminal CNT ₂ , SW ₃ connects the input terminal I ₃ and the output terminal O ₁ , and SW ₄ connects the input terminal I ₇ and output terminal _O2 . In this case, the output terminals O ₁ and O ₂ are connected to terminal sections 45 and 47, which are a pair of electrodes of the resistance section 33, and the resistance value of the resistance section 33 can be measured via the output terminals O ₁ and O ₂ . Become.

Further, when an L signal is input from the outside to the control terminal CNT ₁ and an L signal is input from the outside to the control terminal CNT ₂ , the SW ₃ connects the input terminal I ₄ and the output terminal O ₁ , and the SW ₄ connects the input terminal I ₈ and output terminal _O2 . In this case, the output terminals O ₁ and O ₂ are connected to the terminal parts 46 and 48, which are a pair of electrodes of the resistance part 34, and the resistance value of the resistance part 34 can be measured via the output terminals O ₁ and O ₂ . Become.

The method of using the sensor module 5A is similar to the method described with reference to FIG. 4, except that the control section 73 controls the control terminals CNT ₁ and CNT ₂ of the selection circuit 2A.

In this way, the switches SW ₃ and SW ₄ of the selection circuit 2A can be switched by the combination of H/L signals input from the outside to the control terminals CNT ₁ and CNT ₂ of the selection circuit 2A of the sensor module 5A. Thereby, the resistance value of the resistance part 31, the resistance value of the resistance part 32, the resistance value of the resistance part 33, and the resistance value of the resistance part 34 of the strain gauge 1A can be selectively measured. That is, it is possible to selectively measure strain in the X direction, strain in the Y direction, and strain in directions where the angle with the X direction is ±45 degrees.

<Fifth embodiment>
In the fifth embodiment, an example of a bearing mechanism having a strain gauge is shown. Note that, in the fifth embodiment, descriptions of components that are the same as those in the already described embodiments may be omitted.

FIG. 7 is a perspective view illustrating a bearing mechanism according to a fifth embodiment. FIG. 8 is a cross-sectional view illustrating a bearing mechanism according to a fifth embodiment.

Referring to FIGS. 7 and 8, the bearing mechanism 100 includes a rotating shaft 110 (shaft), a bearing 120 (bearing), and a strain gauge 1. The rotating shaft 110 is rotatably supported by a bearing 120. A strain gauge 1 is attached to the side wall of the bearing 120.

By attaching the strain gauge 1 to the side wall of the bearing 120, vibrations of the bearing 120 can be detected. The life of the bearing 120 is greatly affected by vibrations in addition to the original rolling fatigue life. By attaching the strain gauge 1 to the bearing 120 and detecting vibration, it is possible to predict the life of the bearing 120 based on the results of vibration detection by the strain gauge 1.

Furthermore, by feeding back the vibration information obtained from the strain gauge 1, it is possible to avoid adverse effects on various products using the bearing 120. In particular, since the strain gauge 1 is a two-axis gauge, it is possible to simultaneously detect a vibration component in a direction perpendicular to the rotation axis 110 and a vibration component in the direction of the rotation axis 110. As a result, it is possible to predict the life of the bearing 120 with higher accuracy.

Furthermore, a strain gauge 1A can be used instead of the strain gauge 1. If the bearing mechanism 100 is unbalanced, it tends to vibrate in a direction perpendicular to the rotating shaft 110, and if it is out of alignment, vibrations occur in the direction of the rotating shaft 110.

Since vibrations have characteristics in the direction in which they occur depending on the type of abnormality, it is preferable to measure each of the three directions: vertical, horizontal, and axial. By using the strain gauge 1A, it is possible to simultaneously detect vibrations in three directions, and therefore the ability to isolate vibration sources can be greatly improved.

As described above, in the bearing mechanism 100, by attaching the strain gauge 1 or 1A to the side wall of the bearing 120 and detecting the vibration of the bearing 120, it is possible to accurately detect the abnormal mode of vibration occurring in the bearing 120. can.

Note that the sensor module 5 or 5A may be used instead of the strain gauge 1 or 1A.

Although the preferred embodiments have been described in detail above, they are not limited to the embodiments described above, and various modifications may be made to the embodiments described above without departing from the scope of the claims. Variations and substitutions can be made.

For example, the bridge circuit 71 may be incorporated into the sensor module 5 or 5A. Further, the bridge circuit 71 and the analog front end section 72 may be incorporated into the sensor module 5 or 5A. In this case, for example, the bridge circuit 71 and the analog front end section 72 can be integrated into an IC and mounted on the upper surface 10a or the lower surface 10b of the base material 10.

Further, in the multi-axis gauge, the number of resistance parts is not limited to two or four, and may be three or five or more.

1, 1A strain gauge, 2, 2A selection circuit, 5, 5A sensor module, 7 measurement section, 10 base material, 10a upper surface of base material, 10b lower surface of base material, 30, 30A resistor, 31 to 34 resistor section, 41 to 48 terminal section, 60 cover layer, 71 bridge circuit, 72 analog front end section, 73 control section, 100 bearing mechanism, 110 rotating shaft, 120 bearing

Claims (4)

a flexible base material;
a plurality of resistance parts formed linearly on one side of the base material,
A strain gauge in which each of the resistance parts intersects on the same plane and is electrically connected to each other. The strain gauge according to claim 1, wherein a pair of electrodes are formed at both ends of each of the resistor sections. comprising the strain gauge according to claim 2 and a selection circuit,
The selection circuit is
an input terminal connected to the pair of electrodes of each of the resistor parts;
a switch that selects the pair of electrodes of any one of the resistor parts from among the pair of electrodes of each of the resistor parts connected to the input terminal, and connects the selected electrode to the pair of output terminals. sensor module. The strain gauge according to claim 1 or 2, or the sensor module according to claim 3,
a rotating shaft;
a bearing rotatably supporting the rotating shaft;
A bearing mechanism that detects vibrations of the bearing using the strain gauge or the sensor module.

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