WO2023106236A1

WO2023106236A1 - Strain gauge module

Info

Publication number: WO2023106236A1
Application number: PCT/JP2022/044578
Authority: WO
Inventors: 位小野; 誠北爪; 桂介國府田; 智貴樋上
Original assignee: ミネベアミツミ株式会社
Priority date: 2021-12-08
Filing date: 2022-12-02
Publication date: 2023-06-15

Abstract

This strain gauge module comprises: a film-like strain detection device that is attached to an object to be measured, has a terminal on an upper surface thereof, and is for detecting strain that occurs in the object to be measured; and a thin-plate metal substrate that has an upper surface and a lower surface. The film-like strain detection device is mounted on the upper surface of the thin-plate metal substrate with an adhesive therebetween. The lower surface is an attachment surface for the object to be measured, and a thin-walled section having a partially reduced plate thickness is formed on the lower surface of the thin-plate metal substrate.

Description

strain gauge module

The present invention relates to strain gauge modules.

As a film-like device, for example, a strain gauge having a resistor formed on a flexible base material such as polyimide is known (see, for example, Patent Document 1). Such film-like devices are required to have improved detection sensitivity.

JP 2018-185346 A

The present invention has been made in view of the above points, and aims to provide a strain gauge module with excellent detection sensitivity.

The strain gauge module (1) comprises a film-shaped strain detection device (30) attached to an object to be measured and having terminals (34, 35) on the upper surface for detecting strain occurring in the object to be measured; a thin metal substrate (10) having a bottom surface (10a) and a bottom surface (10b); A strain detection device (30) is mounted, the lower surface (10b) is used as a mounting surface for the measurement object, and a thin plate thickness is partially reduced on the lower surface (10b) of the thin metal substrate (10). A portion (11) is formed.

It should be noted that the reference numerals in parentheses above are attached for easy understanding, and are merely examples, and are not limited to the illustrated embodiment.

According to the disclosed technology, it is possible to provide a strain gauge module with excellent detection sensitivity.

1 is a top view illustrating a strain gauge module according to a first embodiment; FIG. 1 is a cross-sectional view (Part 1) illustrating the strain gauge module according to the first embodiment; FIG. It is a figure explaining surface roughness Ra and the thickness of an adhesive agent. It is a figure explaining a resistor area|region. It is a figure explaining the agreement of the center of gravity of a thin plate metal substrate and a resistor area|region. FIG. 2 is a cross-sectional view (part 2) illustrating the strain gauge module according to the first embodiment; FIG. 2 is a bottom view illustrating the strain gauge module according to the first embodiment; FIG. It is a bottom view (1) which illustrates the variation of thin part shape. FIG. 11 is a bottom view (Part 2) illustrating variations of the shape of the thin portion; FIG. 11 is a bottom view (No. 3) illustrating variations of the shape of the thin portion; It is a measurement result (1) of the output of the film-shaped strain detection device. It is a measurement result (2) of the output of the film-shaped strain detection device. It is a measurement result (3) of the output of the film-shaped strain detection device. It is a measurement result (4) of the output of the film-shaped strain detection device. It is a measurement result (5) of the output of the film-shaped strain detection device. FIG. 11 is a plan view illustrating a strain gauge module according to a modified example of the second embodiment; FIG. 10 is a diagram showing a rate of change in strain detection sensitivity; FIG. 10 is a diagram illustrating a processing system for signals output from the strain gauge module according to the second embodiment; FIG. 10 is a diagram (Part 1) exemplifying the output voltage of the strain gauge module according to the comparative example; FIG. 11 is a diagram (part 2) exemplifying the output voltage of the strain gauge module according to the comparative example; FIG. 11 is a diagram (part 1) illustrating the output voltage of the strain gauge module according to the second embodiment; FIG. 11 is a diagram (part 2) illustrating the output voltage of the strain gauge module according to the second embodiment; It is a measurement result of the output of the film-shaped strain detection device.

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

<First embodiment>
(Strain gauge module)
FIG. 1 is a top view illustrating the strain gauge module according to the first embodiment. FIG. FIG. 2 is a cross-sectional view (Part 1) illustrating the strain gauge module according to the first embodiment, showing a cross section along line AA in FIG. FIG. 3 is a diagram for explaining the surface roughness Ra and the thickness of the adhesive. FIG. 4 is a diagram for explaining the resistor region.

1 and 2, the strain gauge module 1 has a thin plate metal substrate 10, an adhesive 20, and a film strain detection device 30. The strain gauge module 1 is attached to an object to be measured, and the film-shaped strain detection device 30 can detect strain occurring in the object to be measured.

The thin metal substrate 10 is a member on which the film strain detection device 30 is arranged. Specifically, the thin metal substrate 10 has an upper surface 10a and a lower surface 10b. A film-shaped strain detection device 30 is mounted on the upper surface 10a of the thin metal substrate 10, and the lower surface 10b serves as a mounting surface for an object to be measured.

Here, the thin metal substrate refers to a metal substrate having a thickness of 200 μm or less. The thickness of the thin metal substrate 10 is preferably 20 μm or more and 120 μm or less, more preferably 20 μm or more and 80 μm or less, and even more preferably 20 μm or more and 50 μm or less. The thickness of the thin plate metal substrate 10 referred to here is the thickness of a region other than the thin portion 11 which will be described later.

By setting the thickness of the thin metal substrate 10 to 20 μm or more, distortion can be stably detected. By setting the thickness of the thin metal substrate 10 to 120 μm or less, strain can be detected with high sensitivity. Further, by making the thickness of the thin metal substrate 10 thinner, the strain can be detected with higher sensitivity. Moreover, if the thickness of the thin metal substrate 10 is 20 μm or more and 80 μm or less, it can be easily fixed even to a curved object to be measured. If the thickness of the thin plate metal substrate 10 is 20 μm or more and 50 μm or less, it can be more easily fixed even to a curved object to be measured.

The surface roughness Ra of the upper surface 10a of the thin metal substrate 10 is preferably 3 μm or more and 20 μm or less, more preferably 3 μm or more and 10 μm or less, and even more preferably 3 μm or more and 5 μm or less. By setting the surface roughness Ra of the upper surface 10a of the thin metal substrate 10 to 3 μm or more and 20 μm or less, it is possible to reduce the influence of the surface roughness Ra of the upper surface 10a of the thin metal substrate 10 on the film strain detection device 30. , strain can be measured easily and accurately.

Here, the surface roughness Ra is a kind of numerical value representing surface roughness, and is called arithmetic mean roughness. Specifically, as shown in FIG. It is the arithmetic mean of the absolute values of the heights measured from the surface, which is the average line.

As the material of the thin plate metal substrate 10, SUS (stainless steel/iron-based alloy) having high hardness (easily transmitting strain) is suitable for transmitting strain, but the material is not limited thereto. A copper alloy or the like may also be used. In addition, SUS is suitable in that it is easily available. The size of the thin metal substrate 10 is not particularly limited, but is larger than the size of the film strain detection device 30 in plan view.

The film strain detection device 30 is mounted on the upper surface 10a of the thin metal substrate 10 with an adhesive 20 interposed therebetween. As the adhesive 20, for example, an epoxy resin or the like can be used. The bending elastic modulus of the adhesive 20 can be, for example, 3 GPa or more and 20 GPa or less. Adhesive 20 may contain a filler if needed. When the adhesive 20 contains a filler, the contained filler may be an inorganic filler or an organic filler. When the adhesive 20 contains an inorganic filler, the filler diameter is preferably 5 μm or less, and when it contains an organic filler, the filler diameter is preferably 10 μm or less.

The thickness T of the adhesive 20 is preferably 30 μm or less. If the thickness T of the adhesive 20 is 30 μm or less, the distortion of the thin metal substrate 10 can be efficiently transmitted to the film-like distortion detection device 30 . As shown in FIG. 3, the thickness T of the adhesive 20 is the distance from the top surface 10a of the thin metal substrate 10 to the bottom surface of the base material 31 from the tip of the convex portion indicated by the solid line, excluding abnormal protrusions (spikes). is. The unevenness indicated by broken lines in FIG. 3 is a virtual image. 3, that is, the gaps between the unevenness of the upper surface 10a of the thin metal substrate 10 are filled with the adhesive 20. As shown in FIG.

It is preferable that the entire lower surface of the film-shaped strain detection device 30 is adhered to the upper surface 10 a of the thin metal substrate 10 with an adhesive 20 . At this time, the variation in the thickness of the adhesive 20 is preferably ±5 μm or less. As a result, the entire film-shaped strain detection device 30 is flatly held on the upper surface 10a of the thin metal substrate 10, so that the strain of the thin metal substrate 10 can be transmitted to the film-shaped strain detection device 30 more efficiently. can.

The film strain detection device 30 has a substrate 31, a resistor 32, wiring 33, and

terminals

34 and 35. The size of the film-shaped strain detection device 30 is not particularly limited, but from the viewpoint of miniaturization of the strain gauge module 1, the film-shaped strain detection device 30 is also preferably small. It can be square or rectangular with a length of about 1.5 mm to 2 mm.

The base material 31 is a member that serves as a base layer for forming the resistor 32 and has flexibility. The thickness of the base material 31 is not particularly limited and can be appropriately selected according to the purpose. The base material 31 can be formed from, for example, an insulating resin film such as PI (polyimide) resin.

The resistor 32 is a thin film formed on the upper surface of the base material 31, and is a sensing part that undergoes strain and changes in resistance. The resistor 32 may be formed directly on the top surface of the base material 31 or may be formed on the top surface of the base material 31 via another layer. The thickness of the resistor 32 is not particularly limited and can be appropriately selected depending on the purpose.

In the resistor 32, a plurality of elongated portions are arranged in the same longitudinal direction (the direction perpendicular to line AA in the example of FIG. 1) at predetermined intervals, and the ends of adjacent elongated portions are staggered. It is a structure that is connected to and folded back in a zigzag as a whole. The longitudinal direction of the plurality of elongated portions is the grid direction, and the direction perpendicular to the grid direction is the grid width direction (in the example of FIG. 1, the direction of line AA).

The resistor 32 can be made 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 32 can be made of a material containing at least one of Cr and Ni. Materials containing Ni include, for example, Cu—Ni (copper nickel). Materials containing both Cr and Ni include, for example, Ni—Cr (nickel chromium).

A Cr mixed phase film may be used as the resistor 32 . Here, the Cr mixed phase film is a film in which Cr, CrN, Cr ₂ N, or the like is mixed. The Cr mixed phase film may contain unavoidable impurities such as chromium oxide. When a Cr mixed-phase film is used as the resistor 32, the sensitivity of the film strain detection device 30 can be increased and the size can be reduced.

The

terminals

34 and 35 are formed on the upper surface near the ends of the wiring 33 . The

terminals

34 and 35 are connected to both ends of the resistor 32 via wiring 33 made of copper or the like, and are formed, for example, in a rectangular shape in plan view.

Terminals

34 and 35 are a pair of electrodes for outputting a change in the resistance value of resistor 32 caused by strain. The

terminals

34 and 35 are made of copper or the like, for example. A gold film or the like may be laminated on the surface of copper or the like.

As shown in FIG. 2 , the strain gauge module 1 may have a resin portion 36 covering the film strain detection device 30 on the thin metal substrate 10 . The resin portion 36 can be formed, for example, so as to expose part or all of the

terminals

34 and 35 of the film strain detection device 30 . By providing the resin portion 36 covering the film-shaped strain detection device 30 on the thin metal substrate 10, the mechanical strength of the

terminals

34 and 35 of the film-shaped strain detection device 30 is improved and the resistance of the film-shaped strain detection device 30 is improved. Environmental properties (humidity, gas) can be improved.

In order to suppress the output (offset) of the film-shaped strain detection device 30 when strain is not applied, the resin portion 36 is made of a material that does not contain a filler, or a material that contains an inorganic or organic filler of 3 μm or less. It is preferably formed from The resin portion 36 is preferably made of a material having a hardness of D90 to A15 suitable for strain propagation and a tensile strength of 0.3 MPa to 10 MPa. Such materials include, for example, thermosetting or photosetting silicone-based resins and epoxy-based resins. By using such a low-stress resin as the material of the resin portion 36, the influence of the coating with the resin portion 36 on the characteristics (sensitivity) of the film strain detection device 30 can be reduced.

[Positional relationship between thin metal substrate and resistor region]
The thin metal substrate 10 preferably has a rectangular shape in plan view. By forming the thin plate metal substrate 10 in a rectangular shape in plan view, it is possible to detect longitudinal strain with high sensitivity. In FIG. 1 , the thin metal substrate 10 has a rectangular shape in plan view, and a straight line L1 indicates a line passing through the midpoints of the opposing short sides of the thin metal substrate 10 . That is, the straight line L1 is a line that bisects the thin metal substrate 10 in the longitudinal direction. A straight line L2 indicates a line passing through the midpoints of the opposed long sides of the thin metal substrate 10 . That is, the straight line L2 is a line that bisects the thin metal substrate 10 in the lateral direction. The intersection of the straight lines L1 and L2 passes through the center of gravity Gp of the thin metal substrate 10 in plan view. The center of gravity here is the center of gravity in plan view, that is, the center of gravity of a plane figure. For example, the center of gravity Gp of the thin metal substrate 10 is the center of gravity of the rectangle shown in FIG. 1 without considering the thickness of the thin metal substrate 10 .

The film-shaped strain detection device 30 has a resistor region R on its upper surface. As shown in FIG. 4 , on the upper surface of the base material 31 , a rectangular region in plan view where the resistor 32 is formed is the resistor region R. As shown in FIG. Resistor region R is the smallest rectangular region that can be drawn to include all resistors 32 . Gr shown in FIG. 4 indicates the center of gravity Gr of the resistor region R. FIG.

As shown in FIG. 5 , in the strain gauge module 1 , the resistor 32 preferably includes a portion that overlaps the center of gravity Gp of the thin metal substrate 10 . Furthermore, in the strain gauge module 1, it is preferable that the center of gravity Gp of the thin metal substrate 10 and the center of gravity Gr of the resistor region R coincide with each other. In the present application, "the center of gravity of A and the center of gravity of B are coincident" includes, of course, the case where the center of gravity of A and the center of gravity of B are completely coincident in plan view. and the center of gravity of B is within the range of 50 μm. Moreover, the direction of deviation may be arbitrary, and it is sufficient if the center of gravity of B is positioned within a radius of 50 μm with respect to the center of gravity of A. FIG.

Further, when the thin metal substrate 10 and the resistor region R are rectangular in plan view, the fact that the center of gravity Gp of the thin metal substrate 10 and the center of gravity Gr of the resistor region R are coincident means that the diagonal line of the thin metal substrate 10 and the intersection of the diagonal lines of the resistor region R coincide with each other. The permissible amount of deviation between the intersection of the diagonal lines of the thin metal substrate 10 and the intersection of the diagonal lines of the resistor region R is the same as in the above case. That is, if the amount of deviation between the intersections of the two diagonal lines is within the range of 50 μm, the intersections of the two diagonal lines are considered to match.

The center of gravity Gp of the thin metal substrate 10 is the point where strain is most concentrated when the thin metal substrate 10 is attached to the object to be measured and the thin metal substrate 10 receives strain from the object to be measured. Therefore, since the center of gravity Gp of the thin plate metal substrate 10 and the center of gravity Gr of the resistor region R coincide with each other, the strain detection sensitivity of the film strain detection device 30 can be improved. That is, the strain gauge module 1 with excellent detection sensitivity can be realized. This effect can be obtained even when the thin metal substrate 10 is not rectangular in plan view.

From the viewpoint of further improving the strain detection sensitivity of the film strain detection device 30, it is preferable that the center of gravity Gr of the resistor region R is located within a radius of 20 μm from the center of gravity Gp of the thin metal substrate 10, and the resistance is located within a radius of 10 μm. It is more preferable that the center of gravity Gr of the resistor region R is located, and more preferably that the center of gravity Gr of the resistor region R is located within a radius of 5 μm. preferable.

Arrow D shown in FIG. 1 indicates the vibration propagation direction. When the thin metal substrate 10 has a rectangular shape in plan view, it is preferable that the vibration propagation direction D and the longitudinal direction of the thin metal substrate 10 match. Moreover, it is preferable that the vibration propagation direction D and the grid direction of the resistors 32 formed in the resistor region R match. In other words, it is preferable that the longitudinal direction of the thin metal substrate 10 and the grid direction of the resistors 32 formed in the resistor region R match. Due to such a relationship, the detection sensitivity of strain in the vibration propagation direction D can be improved.

[Positional relationship between thin metal substrate and thin part]
FIG. 6 is a cross-sectional view (part 2) illustrating the strain gauge module according to the first embodiment, showing a cross section taken along line BB of FIG. 7 is a bottom view illustrating the strain gauge module according to the first embodiment; FIG.

6 and 7, a thin portion 11 is formed on the lower surface 10b of the thin plate metal substrate 10 so as to be recessed from the lower surface 10b toward the upper surface 10a. In the example of FIGS. 6 and 7, the thin portion 11 includes a first portion 11a, a second portion 11b, and a third portion 11c.

In plan view, the first portion 11a is an elongated portion that is inclined with respect to the straight line L1. The second portion 11b is an elongated portion that is inclined with respect to the straight line L1 at an angle different from that of the first portion 11a. The first portion 11a and the second portion 11b intersect so as to pass through the center of gravity Gp of the thin plate metal substrate 10 and form, for example, an X shape. The third portion 11 c is formed at a position including the center of gravity Gp of the thin metal plate substrate 10 . The third portion 11c has, for example, a rectangular shape, but may have a circular shape, an elliptical shape, or the like.

With the lower surface 10b of the thin metal substrate 10 as a reference, the maximum depth of the thin portion 11 can be 10% or more of the thickness of the thin metal substrate 10. The maximum depth of the thin portion 11 may be 50% or less of the thickness of the thin metal substrate 10 with respect to the lower surface 10 b of the thin metal substrate 10 . The thin portion 11 can be formed by an appropriate method such as a corrosion method, an electropolishing method, or a blasting method.

In the first portion 11a and the second portion 11b, the shape of the vertical cross section taken in the direction perpendicular to the longitudinal direction is, for example, rectangular, semicircular (U-shaped), or triangular (V-shaped). , a trapezoidal shape, or the like. In the third portion 11c, the shape of the longitudinal section taken along the straight line L1 or L2 is, for example, rectangular, semicircular (U-shaped), triangular (V-shaped), trapezoidal, or the like. may be

In the thin portion 11, the depth of the deepest portion is preferably substantially constant regardless of location. For example, in the thin portion 11, the depth of the deepest portion of the first portion 11a, the depth of the deepest portion of the second portion 11b, and the depth of the deepest portion of the third portion 11c are preferably the same. .

In the structure in which the film-shaped strain detection device 30 is adhered to the thin metal substrate 10, the sensitivity characteristics of the film-shaped strain detection device 30 may be attenuated. In the strain gauge module 1, by forming the thin portion 11 on the lower surface 10b of the thin plate metal substrate 10, the attenuated strain can be recovered or amplified by concentrating the attenuated strain. As a result, the characteristic fluctuation of the film-shaped strain detection device 30 can be suppressed, and the strain gauge module 1 with excellent stability and high sensitivity can be realized.

The effect of recovering or amplifying the attenuated strain is obtained by forming a thin portion on the lower surface 10b of the thin metal substrate 10. Therefore, the shape of the thin portion for obtaining the above effects is not limited to the shape of the thin portion 11 . However, from the viewpoint of enhancing the above effect, it is preferable that the thin portion has a line-symmetrical shape with respect to a straight line passing through the center of gravity Gp of the thin plate metal substrate 10 in plan view.

Examples of the straight line passing through the center of gravity Gp of the thin metal substrate 10 include the straight line L1 and the straight line L2. The straight line passing through the center of gravity Gp of the thin plate metal substrate 10 is not limited to the straight line L1 or the straight line L2. can be particularly enhanced. The thin portion 11 is symmetrical with respect to the straight lines L1 and L2.

In addition, from the viewpoint of further enhancing the above effect, the thin portion 11 is formed at a position including the center of gravity Gp of the thin metal substrate 10 in plan view, and the resistor 32 overlaps with the center of gravity Gp of the thin metal substrate 10. preferably included. It is preferable that the center of gravity Gt1 of the thin portion 11 and the center of gravity Gp of the thin plate metal substrate 10 coincide with each other. It is particularly preferable that the center of gravity Gt1 of thin portion 11, the center of gravity Gp of thin plate metal substrate 10, and the center of gravity Gr of resistor region R coincide with each other.

Also, from the viewpoint of further enhancing the above effect, the thin portion is preferably a combination of two or more patterns. For example, the thin portion 11 is a combination of three patterns: a first portion 11a that is a first pattern, a second portion 11b that is a second pattern, and a third portion 11c that is a third pattern. .

Since the bottom layer of the strain gauge module 1 is the thin metal substrate 10, the lower surface 10b of the thin metal substrate 10 is attached to the object to be measured by applying a liquid or film (tape) adhesive or adhesive to the object to be measured. can be easily fixed as The thickness of the adhesive or pressure-sensitive adhesive can be, for example, about 25 μm.

That is, unlike conventional strain gauges, the strain gauge module 1 does not have a bottom layer made of flexible resin (such as polyimide), so it can be easily attached to the object to be measured. Moreover, since polyimide is a difficult-to-adhere material, a special adhesion method (heating and pressure) is required to attach it to the object to be measured. No method is required.

When the strain gauge module 1 is adhered to the object to be measured, it is preferable to apply the adhesive to the entire lower surface 10b of the thin plate metal substrate 10 and to fill the entire inside of the thin portion 11 with the adhesive. . As a result, no gap is formed inside the thin portion 11 , so strain from the object to be measured can be efficiently transmitted to the thin metal substrate 10 . Examples of the adhesive used for bonding the strain gauge module 1 and the object to be measured include epoxy-based resin and the like.

In addition, the thin metal substrate 10 should be adhered to the object to be measured in a substantially flat state, for example, with an adhesive within a thickness range of about 3 to 100 μm, with a thickness variation of about ±5 μm. is preferred. Thereby, strain from the object to be measured can be efficiently transmitted to the thin metal substrate 10 .

[Variation of thin part shape]
8 to 10 are bottom views illustrating variations of the shape of the thin portion. The shape of the thin portion may be the shape of the thin portion 11 shown in FIG. 7 or the like, the shape of the thin portions 12 to 14 shown in FIGS. 8 to 10, or any other shape. good too.

A strain gauge module 1A shown in FIG. 8 has the same structure as the strain gauge module 1 except that a thin portion 12 is formed instead of the thin portion 11. The thin portion 12 is a combination of two patterns including a first portion 12a and a second portion 12b. The first portion 12a has a substantially semicircular shape that draws an arc toward the straight line L1 side. The second portion 12b is symmetrical with the first portion 12a with respect to the straight line L1. Each of the first portion 12a and the second portion 12b is symmetrical with respect to the straight line L2. It is preferable that the center of gravity Gt2 of the thin portion 12 and the center of gravity Gp of the thin plate metal substrate 10 match.

A strain gauge module 1B shown in FIG. 9 has the same structure as the strain gauge module 1 except that a thin portion 13 is formed instead of the thin portion 11. The thin portion 13 is a combination of three patterns including a first portion 13a, a second portion 13b, and a third portion 13c. The first portion 13a has a substantially semi-elliptical shape that draws an arc toward the straight line L1 side. The second portion 13b is symmetrical with the first portion 13a with respect to the straight line L1. The third portion 13c has a substantially rectangular shape and is provided at a position bridging the first portion 13a and the second portion 13b. The third portion 13 c is formed at a position including the center of gravity Gp of the thin metal plate substrate 10 . The thin portion 13 is symmetrical with respect to the straight lines L1 and L2. It is preferable that the center of gravity Gt3 of the thin portion 13 and the center of gravity Gp of the thin plate metal substrate 10 match.

A strain gauge module 1C shown in FIG. 10 has the same structure as the strain gauge module 1 except that a thin portion 14 is formed instead of the thin portion 11. The thin portion 14 is a combination of three patterns including a first portion 14a, a second portion 14b, and a third portion 14c. The first portion 14a has a substantially semicircular shape that draws an arc toward the peripheral portion of the thin plate metal substrate 10 . The second portion 14b is symmetrical with the first portion 14a with respect to the straight line L1. The third portion 14c is rectangular and symmetrical with respect to the straight lines L1 and L2. The third portion 14 c is formed at a position including the center of gravity Gp of the thin metal plate substrate 10 . The thin portion 14 is symmetrical with respect to the straight lines L1 and L2. It is preferable that the center of gravity Gt4 of the thin portion 14 and the center of gravity Gp of the thin plate metal substrate 10 match.

[Change in detection sensitivity]
In the strain gauge module 1, changes in detection sensitivity of the film strain detection device 30 were investigated.

First, the output of the film-shaped distortion detection device 30 was measured when the film-shaped distortion detection device 30 was directly attached to the object to be measured. Next, as a comparative example, a strain gauge module having the same structure as the strain gauge module 1 except that the thin portion is not formed (for convenience, referred to as the strain gauge module 100) is manufactured, and the film is attached to the object to be measured. The output of the shape distortion detection device 30 was measured.

Fig. 11 shows the measurement results. In FIG. 11, the measurement result of the film-shaped strain detection device 30 alone is indicated by a dashed line (single device), and the measurement result of the strain gauge module 100 according to the comparative example is indicated by a dashed line (without thin portion). In FIG. 11, the vertical axis represents the amount of change in the value (output) obtained by converting the resistance value of the film-shaped distortion detection device 30 into analog/digital (for convenience, output). showing. In FIG. 11, the horizontal axis is elapsed time.

In FIG. 11, when comparing the dashed line (single device) representing the measurement result of the film-shaped strain detection device 30 alone with the dashed line (without the thin portion) representing the measurement result of the strain gauge module 100 according to the comparative example, the comparative example It has been found that the related strain gauge module 100 has an output attenuated by about 2% as compared with the film-shaped strain detection device 30 alone.

Next, the strain gauge module 1 formed with the thin portion 11 shown in FIGS. 6 and 7 was produced, and the output of the film-shaped strain detection device 30 when attached to the measurement object was measured. The measurement results are indicated by a solid line (thin portion 11) in FIG. Note that FIG. 12 shows the dashed line (single device) and the dashed line (without the thin portion) shown in FIG. 11 for comparison. The same applies to FIGS. 13 to 15 below.

Next, the strain gauge module 1A having the thin portion 12 shown in FIG. 8 was produced, and the output of the film-shaped strain detection device 30 when attached to the measurement object was measured. The measurement results are indicated by a solid line (thin portion 12) in FIG. In addition, the strain gauge module 1B having the thin portion 13 shown in FIG. 9 was produced, and the output of the film-shaped strain detection device 30 was measured when it was attached to the object to be measured. The measurement results are indicated by a solid line (thin portion 13) in FIG. Also, a strain gauge module 1C having a thin portion 14 shown in FIG. 10 was produced, and the output of the film-shaped strain detection device 30 was measured when the module was attached to a measurement object. The measurement results are indicated by a solid line (thin portion 14) in FIG.

　In FIGS. 12 to 15, when comparing the dashed line (without the thin portion) and the solid line (each thin portion), the solid line (each thin portion) exceeds the dashed line (without the thin portion). 12 to 15, when the thin portions 11 to 14 are formed, the output of the film strain detection device 30 increases more than when the thin portions are not formed. That is, by forming a thin portion recessed from the lower surface 10b toward the upper surface 10a on the lower surface 10b of the thin metal substrate 10, the strain attenuated by the structure in which the film strain detection device 30 is adhered to the thin metal substrate 10 (broken line ( It was confirmed that detection sensitivity can be improved by recovering or amplifying (no thin portion)).

In addition, in the thin portion 11 shown in FIGS. 6 and 7, it is mainly the first portion 11a and the second portion 11b that contribute to the improvement of detection sensitivity. However, by forming the third portion 11c, the flow of the adhesive filled inside the thin portion 11 is improved, so that the entire thin portion 11 can be uniformly filled with the adhesive.

<Second embodiment>
In the second embodiment, an example of a strain gauge module in which a thin portion is not formed on the lower surface of the thin plate metal substrate is shown.

In the strain gauge module 1 shown in FIGS. 1 and 2, the thin portion may not be formed on the bottom surface of the thin plate metal substrate 10 . Also in this case, detection sensitivity can be increased by reducing the amount of deviation between the center of gravity Gp of the thin plate metal substrate 10 and the center of gravity Gr of the resistor region R. FIG.

Note that the positional relationship between the resistor region R and the

terminals

34 and 35 is not limited to the example in FIG. For example, as in a strain gauge module 1A shown in FIG. 16, the positions of the

terminals

34 and 35 may be different in the longitudinal direction of the thin plate metal substrate 10 . Of course,

terminals

34 and 35 may be in positions other than those of FIGS. The point is that the center of gravity Gp of the thin plate metal substrate 10 and the center of gravity Gr of the resistor region R only need to coincide with each other.

[Change in detection sensitivity]
In the strain gauge module 1, the displacement between the center of gravity Gp of the thin metal substrate 10 and the center of gravity Gr of the resistor region R is 5 μm in the longitudinal direction of the thin metal substrate 10, and the center of gravity Gp of the thin metal substrate 10 and the resistors The rate of change in the detection sensitivity of the film-shaped strain detection device 30 when the stress changes was investigated in the case where the deviation amount of the region R from the center of gravity Gr is 50 μm in the longitudinal direction of the thin plate metal substrate 10 . No thin portion is formed on the lower surface of the thin metal substrate 10 .

FIG. 17 is a diagram showing the rate of change in strain detection sensitivity. As shown in FIG. 17, when the amount of deviation between the center of gravity Gp of the thin plate metal substrate 10 and the center of gravity Gr of the resistor region R is 5 μm in the longitudinal direction of the thin plate metal substrate 10, the detection sensitivity when the stress is 100 is The rate of change is about -2%. On the other hand, when the amount of deviation between the center of gravity Gp of the thin plate metal substrate 10 and the center of gravity Gr of the resistor region R is 50 μm in the longitudinal direction of the thin plate metal substrate 10, the change rate of the detection sensitivity when the stress is 100 is is about -5%.

If the rate of change in detection sensitivity when the stress is 100 is about −5%, it can be used in practice. Therefore, from the data in FIG. It can be said that the amount of deviation of the resistor region R from the center of gravity Gr is 50 μm in the longitudinal direction of the thin plate metal substrate 10 .

Further, the smaller the amount of deviation between the center of gravity Gp of the thin plate metal substrate 10 and the center of gravity Gr of the resistor region R, the better the detection sensitivity. It can be said that sufficient sensitivity is obtained when the thickness of the thin metal substrate 10 is 5 μm in the longitudinal direction.

Note that the rate of change in the strain detection sensitivity is maximized when the center of gravity Gp of the thin metal substrate 10 and the center of gravity Gr of the resistor region R are deviated in the longitudinal direction of the thin metal substrate 10 . Therefore, it can be said that the amount of deviation between the center of gravity Gp of the thin metal substrate 10 and the center of gravity Gr of the resistor region R that is permissible for the strain gauge module 1 is within the range of 50 μm in all directions.

[Example of signal processing process]
An example of a signal processing process using a strain gauge module will now be described. FIG. 18 is a diagram illustrating a signal processing system output from the strain gauge module according to the second embodiment. Although the strain gauge module 1 is used in FIG. 18, the strain gauge module 1A may be used.

As shown in FIG. 18, the output of strain gauge module 1 is connected to bridge box 150 . For example, the

terminals

34 and 35 of the film strain detection device 30 mounted on the strain gauge module 1 are connected to the bridge box 150 by wires or the like. Bridge box 150 is connected to signal processing section 200 . The signal processing section 200 has a bridge voltage 210, a distortion amplifier 220, and an A/D converter 230, for example.

For example, a bridge circuit is arranged in the bridge box 150, one side of the bridge circuit is composed of the resistor 32 connected between the

terminals

34 and 35, and the other three sides are composed of fixed resistors. A bridge circuit in the bridge box 150 is supplied with a DC voltage from a bridge voltage 210 . As a result, an analog signal corresponding to the resistance value of the resistor 32 can be obtained as the output of the bridge circuit.

The analog signal obtained by the bridge box 150 is input to the distortion amplifier 220 and amplified by the distortion amplifier 220 . The analog signal amplified by the distortion amplifier 220 is converted to a digital signal by the A/D converter 230, input to the computer 300, and subjected to predetermined calculations. For example, a storage device 400 is connected to the computer 300, and results of calculations by the computer 300 are stored.

19A and 19B are diagrams illustrating output voltages of strain gauge modules according to comparative examples. 19A shows the output voltage from the bridge box 150 when the strain gauge module according to the comparative example is connected in place of the strain gauge module 1 in FIG. 18, and FIG. 19B shows the output voltage from the strain amplifier 220. is the output voltage. The strain gauge module according to the comparative example is similar to the strain gauge module 1 except that the amount of deviation between the center of gravity Gp of the thin plate metal substrate 10 and the center of gravity Gr of the resistor region R is 100 μm in the longitudinal direction of the thin plate metal substrate 10 . They have the same structure.

20A and 20B are diagrams illustrating output voltages of the strain gauge module according to the second embodiment. 20A is the output voltage output from the bridge box 150 of FIG. 18, and FIG. 20B is the output voltage output from the distortion amplifier 220 of FIG. Here, the strain gauge module 1 is used in which the amount of deviation between the center of gravity Gp of the thin metal substrate 10 and the center of gravity Gr of the resistor region R is 5 μm in the longitudinal direction of the thin metal substrate 10 .

The strain gauge module 1 has a high detection sensitivity because the amount of deviation between the center of gravity Gp of the thin plate metal substrate 10 and the center of gravity Gr of the resistor region R is smaller than that of the strain gauge module according to the comparative example. Therefore, as can be seen by comparing FIG. 19A and FIG. 20A, the strain gauge module 1 can obtain a larger amplitude output voltage from the bridge box 150 than the strain gauge module according to the comparative example.

Also, when using the strain gauge module 1 which has high detection sensitivity and can obtain a large amplitude output voltage from the bridge box 150, the gain of the strain amplifier 220 can be made lower than when using the strain gauge module according to the comparative example. Therefore, as can be seen by comparing FIG. 19B and FIG. 20B, the use of the strain gauge module 1 reduces the influence of noise from the strain amplifier 220 more than the use of the strain gauge module according to the comparative example. An output voltage with a high S/N ratio can be obtained. As a result, using the strain gauge module 1 enables highly accurate strain detection.

<Third embodiment>
The third embodiment shows an example of a strain gauge module using a thin plate substrate 10A made of amorphous material or nanocrystalline material instead of the thin plate metal substrate 10 shown in the first and second embodiments. Note that the plan view and the cross-sectional view are the same as those in FIGS. 1 and 2, so illustration thereof is omitted. The thin portion may not be formed on the lower surface of the thin plate substrate 10A.

It is preferable that the thin plate substrate 10A has flatness over the entire surface with no waviness and warpage. As with the thin metal substrate 10, the surface roughness Ra of the upper surface 10a of the thin substrate 10A is preferably 3 μm or more and 20 μm or less, more preferably 3 μm or more and 10 μm or less, and 3 μm or more and 5 μm or less. is more preferable. By setting the surface roughness Ra of the upper surface 10a of the thin plate substrate 10A to 3 μm or more and 20 μm or less, it is possible to reduce the influence of the surface roughness Ra of the upper surface 10a of the thin plate substrate 10A on the film-shaped strain detection device 30, and the strain is reduced. can be measured easily and accurately.

The thin plate substrate 10A is made of amorphous material or nanocrystalline material. Specifically, the material of the thin plate substrate 10A is glass, which is an example of an amorphous material. Alternatively, the material of the thin plate substrate 10A is an amorphous alloy, which is an example of a nanocrystalline material. Amorphous alloys, in particular, are Fe-based, Ni-based, or cobalt-based materials that contain 15 to 30 atomic percent of boron, carbon, silicon, phosphorus, etc., as current materials. It has excellent characteristics in terms of surface, and can be used in a wide range of environments. Amorphous materials such as glasses and amorphous alloys are known to have the property of avoiding strain attenuation due to the crystal structure and recovering or amplifying the strain that has been attenuated. The thin plate substrate 10A using such a material is formed by an appropriate method such as a corrosion method, an electropolishing method, or a mechanical cutting method. The size of the thin plate substrate 10A is not particularly limited, but is larger than the size of the film strain detection device 30 in a plan view.

In the structure in which the film-shaped strain detection device 30 is adhered to the thin plate substrate 10A, the sensitivity characteristics of the film-shaped strain detection device 30 may be attenuated due to the crystal structure (grain boundaries). In the strain gauge module 1, by using an amorphous material or a nanocrystalline material as the material of the thin plate substrate 10A, the property is used to avoid strain attenuation due to the crystal structure, or recover or amplify the strain that has been attenuated. be able to. As a result, the characteristic fluctuation of the film-shaped strain detection device 30 can be suppressed, and the strain gauge module 1 with excellent stability and high sensitivity can be realized.

[Change in detection sensitivity]
In the strain gauge module 1, the thin plate substrate 10A was used in place of the thin plate metal substrate 10, and changes in the detection sensitivity of the film strain detection device 30 were examined. No thin portion is formed on the lower surface of the thin plate substrate 10A.

First, the output of the film-shaped distortion detection device 30 was measured when the film-shaped distortion detection device 30 was directly attached to the object to be measured. Next, as a comparative example, a strain gauge module having the same structure as the strain gauge module 1 except that a metal substrate is used for the thin plate substrate 10A is manufactured (for convenience, referred to as a strain gauge module 100) and attached to the object to be measured. The output of the film strain detection device 30 was measured. Next, the strain gauge module 1 using a glass substrate as the thin plate substrate 10A was produced, and the output of the film-shaped strain detection device 30 was measured when the strain gauge module 1 was attached to the object to be measured.

Fig. 21 shows the measurement results. In FIG. 21, the dashed line 30 indicates the measurement result of the film strain detection device 30 alone, the solid line 100 indicates the measurement result of the strain gauge module 100 according to the comparative example, and the dashed line 1 indicates the measurement result of the strain gauge module 1. showing. In FIG. 21, the vertical axis indicates the amount of change in the value (output for convenience) obtained by converting the resistance value of the film-shaped distortion detection device 30 to analog/digital. showing. In FIG. 21, the horizontal axis is elapsed time.

In FIG. 21, when the measurement result of the film-shaped strain detection device 30 alone (broken line 30 alone) and the measurement result of the strain gauge module 100 (solid line 100) are compared, the strain gauge module 100 shows that the film-shaped strain detection device 30 alone It was found that the output was attenuated by about 2%. On the other hand, in the strain gauge module 1, it was found that the output of the film-shaped strain detection device 30 increased more than that in the strain gauge module 100. FIG. That is, by using the glass substrate as the thin plate substrate 10A, the attenuated strain (solid line 100) when using the metal substrate is recovered or amplified compared to the strain (single dashed line 30) when the metal substrate is not used. It was confirmed that the detection sensitivity can be improved. When the Fe-based amorphous alloy substrate was used as the thin plate substrate 10A, substantially the same results were obtained as when the glass substrate was used as the thin plate substrate 10A.

Although the preferred embodiment has been described in detail above, it is not limited to the above-described embodiment, and various modifications and substitutions can be made to the above-described embodiment without departing from the scope of the claims. can be done.

In addition to the above embodiments, the following additional remarks are disclosed.
(Appendix 1)
A film-shaped strain detection device attached to a measurement object and having terminals and a resistor area on the upper surface for detecting strain occurring in the measurement object; and a thin sheet metal substrate having an upper surface and a lower surface. configured,
The film-shaped strain detection device is mounted on the upper surface of the thin metal substrate via an adhesive, and the lower surface is used as a mounting surface for the measurement object,
A strain gauge module in which the center of gravity of the thin metal substrate coincides with the center of gravity of the resistor region.
(Appendix 2)
The strain gauge module according to appendix 1, wherein the thin metal substrate and the resistor region are rectangular in plan view, and an intersection point of diagonal lines of the thin metal substrate and an intersection point of diagonal lines of the resistor region are aligned.
(Appendix 3)
The thin metal substrate has a rectangular shape in plan view,
3. The strain gauge module according to

appendix

1 or 2, wherein the longitudinal direction of the thin metal substrate and the grid direction of the resistors formed in the resistor region are aligned.
(Appendix 4)
4. The strain gauge module according to any one of Appendices 1 to 3, wherein the adhesive has a thickness of 30 μm or less.
(Appendix 5)
The entire lower surface of the film strain detection device is adhered to the upper surface of the thin metal substrate with the adhesive,
5. The strain gauge module according to appendix 4, wherein the thickness variation of the adhesive is ±5 μm or less.
(Appendix 6)
6. The strain gauge module according to any one of appendices 1 to 5, wherein the thin metal substrate has a thickness of 20 μm or more and 120 μm or less.
(Appendix 7)
7. The strain gauge module according to any one of Appendices 1 to 6, wherein the surface roughness Ra of the upper surface of the thin metal substrate is 3 μm or more and 20 μm or less.
(Appendix 8)
8. The strain gauge module according to any one of Appendices 1 to 7, wherein the thin metal substrate is made of stainless steel.
(Appendix 9)
9. The strain gauge module according to any one of Appendices 1 to 8, wherein the film strain detection device includes a base material made of polyimide and a resistor formed on the base material.
(Appendix 10)
A film-shaped strain detection device attached to a measurement object and having terminals and a resistor area on the upper surface for detecting strain occurring in the measurement object; and a thin sheet metal substrate having an upper surface and a lower surface. configured,
The film-shaped strain detection device is mounted on the upper surface of the thin metal substrate via an adhesive, and the lower surface is used as a mounting surface for the measurement object,
The strain gauge module, wherein the center of gravity of the resistor region is located within a radius of 50 μm from the center of gravity of the thin metal substrate.
(Appendix 11)
11. The strain gauge module according to claim 10, wherein the displacement of the center of gravity of the resistor region is within 50 μm in the longitudinal direction of the thin metal substrate from the center of gravity of the thin metal substrate.
(Appendix 12)
A film-shaped distortion detection device attached to an object to be measured, having a terminal on the upper surface for detecting distortion occurring in the object to be measured, and a thin plate substrate having an upper surface and a lower surface,
The film-shaped strain detection device is mounted on the upper surface of the thin plate substrate via an adhesive, and the lower surface is used as a mounting surface for the measurement object,
The strain gauge module, wherein the thin substrate is made of amorphous material or nanocrystalline material.
(Appendix 13)
13. The strain gauge module according to appendix 12, wherein the thin substrate has a thickness of 20 μm or more and 120 μm or less.
(Appendix 14)
14. The strain gauge module according to

appendix

12 or 13, wherein the surface roughness Ra of the upper surface of the thin plate substrate is 3 μm or more and 20 μm or less.
(Appendix 15)
15. The strain gauge module according to any one of appendices 12 to 14, wherein the material of the thin plate substrate is glass.
(Appendix 16)
15. The strain gauge module according to any one of appendices 12 to 14, wherein the material of the thin plate substrate is an amorphous alloy.
(Appendix 17)
17. The strain gauge module according to appendix 16, wherein the material of the thin plate substrate is an Fe-based amorphous alloy.
(Appendix 18)
18. The strain gauge module according to any one of appendices 12 to 17, wherein the thin plate substrate has a rectangular shape in plan view.
(Appendix 19)
The film-shaped strain detection device includes a resistor region in which a resistor is formed,
19. The strain gauge module according to any one of appendices 12 to 18, wherein the resistor includes a portion overlapping the center of gravity of the thin plate substrate.
(Appendix 20)
20. The strain gauge module according to appendix 19, wherein the center of gravity of the thin substrate coincides with the center of gravity of the resistor region.
(Appendix 21)
21. The strain gauge module according to appendix 19 or 20, wherein the film strain detection device includes a base material made of polyimide, and the resistor is formed on the base material.

This international application is Japanese Patent Application No. 2021-199467 filed on December 8, 2021, Japanese Patent Application No. 2021-204877 filed on December 17, 2021, and filed on December 17, 2021 It claims priority based on Japanese Patent Application No. 2021-204878, and the entire contents of Japanese Patent Application No. 2021-199467, Japanese Patent Application No. 2021-204877, and Japanese Patent Application No. 2021-204878 incorporated into this international application.

1, 1A, 1B, 1C strain gauge module, 10 thin plate metal substrate, 10a upper surface, 10b lower surface, 11, 12, 13, 14 thin portion, 11a, 12a, 13a, 14a first portion, 11b, 12b, 13b, 14b Second part, 11c, 13c, 14c Third part, 20 Adhesive, 30 Film strain detection device, 31 Base material, 32 Resistor, 33 Wiring, 34, 35 Terminal, 36 Resin part, 150 Bridge box, 200 Signal Processing unit, 210 bridge voltage, 220 distortion amplifier, 230 A/D converter, 300 computer, 400 storage device

Claims

A film strain detection device attached to an object to be measured and having a terminal on the upper surface for detecting strain occurring in the object to be measured; and a thin plate metal substrate having an upper surface and a lower surface,
The film-shaped strain detection device is mounted on the upper surface of the thin metal substrate via an adhesive, and the lower surface is used as a mounting surface for the measurement object,
A strain gauge module in which a thin portion having a partially reduced plate thickness is formed on the lower surface of the thin plate metal substrate.
The strain gauge module according to claim 1, wherein the thin portion has a line-symmetrical shape with respect to a straight line passing through the center of gravity of the thin metal substrate when viewed from above.
The film-shaped strain detection device includes a resistor region in which a resistor is formed,
3. The strain gauge module according to claim 1, wherein the thin portion is formed at a position including the center of gravity of the thin metal plate substrate in a plan view, and the resistor includes a portion overlapping the center of gravity of the thin metal plate substrate.
The strain gauge module according to claim 3, wherein the center of gravity of said thin portion, the center of gravity of said thin plate metal substrate, and the center of gravity of said resistor region are aligned.
The strain gauge module according to claim 3 or 4, wherein the film strain detection device includes a base material made of polyimide, and the resistor is formed on the base material.
The strain gauge module according to any one of claims 1 to 5, wherein the maximum depth of said thin portion is 10% or more of the thickness of said thin plate metal substrate.
The strain gauge module according to any one of claims 1 to 6, wherein the thickness of the thin plate metal substrate other than the thin portion is 20 µm or more and 120 µm or less.
The strain gauge module according to any one of claims 1 to 7, wherein the surface roughness Ra of the upper surface of the thin metal substrate is 3 µm or more and 20 µm or less.
The strain gauge module according to any one of claims 1 to 8, wherein the thin metal substrate is made of stainless steel.
The strain gauge module according to any one of claims 1 to 9, wherein the thin metal substrate has a rectangular shape in plan view.