Strain detection device

Abstract

The technical problem of the embodiment is to provide a strain detection device capable of improving detection precision. A strain detection device according to an embodiment is provided with: a flexible substrate; and first, second, third, and fourth sensor patterns each having a plurality of strain gauges arranged in a row, the first, second, third, and fourth sensor patterns being disposed on the substrate. The first strain gauge of the first sensor pattern, the second strain gauge of the second sensor pattern, the third strain gauge of the third sensor pattern, and the fourth strain gauge of the fourth sensor pattern are disposed so as to face each other in the thickness direction of the substrate. The first strain gauge and the fourth strain gauge are symmetrically arranged relative to the center position of the thickness direction of the base material, and the second strain gauge and the third strain gauge are symmetrically arranged relative to the center position of the thickness direction of the base material.

Description

[0001] Related Applications

[0002] This application is based on Japanese Patent Application No. 2023-128717 (filing date: August 7, 2023) and claims the priority of the said application. The present application incorporates the entire contents of the said application by citing the said application. Technical Field

[0003] Embodiments of the present invention relate to a strain sensing device. Background Art

[0004] As an example of a strain detection device, a flexible film-shaped or sheet-shaped strain gauge sensor is known. The strain gauge sensor has strain gauges arranged on the surface of a strip-shaped flexible sheet substrate and a plurality of signal lines for energizing the strain gauges. In addition, a plurality of strain gauges are provided on the surface and back of the sheet. The strain gauges on the surface side are arranged opposite to the strain gauges on the back side. By winding the strain gauge sensor around a curved object to be measured and detecting the resistance change of each strain gauge, the curved shape of the object to be measured can be checked. Summary of the invention

[0005] An object of an embodiment of the present invention is to provide a strain detection device capable of improving detection accuracy.

[0006] The strain detection device according to the embodiment includes: a flexible substrate including a plurality of insulating layers; a first sensor pattern including a plurality of first strain gauges arranged in a row at intervals in a first direction and a plurality of wirings connected to the first strain gauges, and provided on the substrate; a second sensor pattern including a plurality of second strain gauges arranged in a row at intervals in the first direction and a plurality of wirings connected to the second strain gauges, and stacked on the substrate and facing the first sensor pattern with the insulating layer interposed therebetween; a third sensor pattern including a plurality of third strain gauges arranged in a row at intervals in the first direction and a plurality of wirings connected to the third strain gauges, and stacked on the substrate and facing the second sensor pattern with the insulating layer interposed therebetween; a fourth sensor pattern including a plurality of fourth strain gauges arranged in a row at intervals in the first direction and a plurality of wirings connected to the fourth strain gauges, and stacked on the substrate and facing the third sensor pattern with the insulating layer interposed therebetween; and a controller for applying voltages to the first, second, third, and fourth strain gauges via the plurality of wirings and reading detection values ​​of the respective strain gauges. The first strain gauge, the second strain gauge, the third strain gauge and the fourth strain gauge are arranged opposite to each other in the thickness direction of the substrate, the first strain gauge and the fourth strain gauge are arranged symmetrically with respect to the center position of the thickness direction of the substrate, and the second strain gauge and the third strain gauge are arranged symmetrically with respect to the center position of the thickness direction of the substrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 It is a perspective view of the strain gauge sensor device according to the embodiment.

[0008] Figure 2 is a longitudinal cross-sectional view of the strain gauge sensor device.

[0009] Figure 3 is along Figure 2 A cross-sectional view of the strain gauge sensor device along line AA.

[0010] Figure 4 It is a longitudinal sectional view of a strain gauge sensor device according to a modification.

[0011] Figure 5 FIG. 1 is a development diagram schematically showing strain gauges and wirings of a second sensor pattern and a third sensor pattern of the strain gauge sensor device according to the embodiment.

[0012] Figure 6 is a perspective view schematically showing a stacked structure of a sensor pattern of a first sensor sheet in the strain gauge sensor device.

[0013] Figure 7 is a block diagram of a controller of the strain gauge sensor device.

[0014] Figure 8 FIG. 1 is a top view showing the first to fourth sensor patterns of the strain gauge sensor device and the analog front end of the controller in an expanded manner, illustrating a scanning operation during detection.

[0015] Fig. 9 is a circuit diagram of a differential detection circuit in the analog front end.

[0016] Fig.10 It is a side view schematically showing a state where the strain gauge sensor device is installed on the surface of a measured object.

[0017] Fig.11 FIG. 1 is a diagram schematically showing a portion of the strain gauge sensor device in a state where the strain gauge sensor device is installed on the surface of a measured object.

[0018] Fig.12 FIG. 1 is a top view showing the first to fourth sensor patterns of the strain gauge sensor device and the analog front end of the controller in an expanded manner, illustrating a scanning operation during detection.

[0019] Fig.13A It is schematically shown by Fig.11 FIG. 1 is a diagram showing an example of strain detection by strain gauges in the second and third layers of a portion of a strain gauge sensor device.

[0020] Fig. 13B It is schematically shown by Fig.11 FIG. 1 is a diagram showing an example of strain detection by strain gauges in the first and fourth layers of a portion of a strain gauge sensor device.

[0021] Fig.14 The figure shows the curved surface shape obtained by plotting the curvature radius calculated based on the detection value of the strain detected by the strain gauges of the second layer and the third layer.

[0022] Fig.15 The figure shows the curved surface shape obtained by plotting the curvature radius calculated based on the detection value of the strain detected by the strain gauges of the first layer and the fourth layer.

[0023] Fig.16 This is a diagram showing the curved surface form obtained by plotting the average values ​​of the curvature radii calculated as final data.

[0024] Fig.17 is a diagram schematically showing the dynamic range of the inner strain gauge and the outer strain gauge. DETAILED DESCRIPTION

[0025] Next, refer to the attached Figure 1 The embodiments of the present invention will be described in detail.

[0026] It should be noted that the disclosure is only an example, and the content of appropriate changes that can be easily thought of by those skilled in the art while maintaining the main idea of ​​the invention is naturally included in the scope of the present invention. In addition, in order to make the description clearer, the drawings schematically show the width, thickness, shape, etc. of each part compared with the actual aspect, but the drawings are only examples and do not limit the interpretation of the present invention. In addition, in this specification and the drawings, the same elements as those described in the existing drawings are represented by the same reference numerals, and their detailed description is appropriately omitted.

[0027] (Implementation Method)

[0028] As an example of a strain detection device, a strain gauge sensor device according to the embodiment will be described in detail. Figure 1 It is a perspective view of the strain gauge sensor device according to the embodiment.

[0029] As shown in the figure, the strain gauge sensor device 10 constitutes a double-sided strain gauge sensor. The strain gauge sensor device 10 includes: a flexible base substrate 44 in the form of an elongated strip serving as a base material, a first sensor sheet 20A attached to the first main surface (front surface) of the base substrate 44, a second sensor sheet 20B attached to the second main surface (back surface) of the base substrate 44, a pair of flexible wiring boards (FPC) 14, and a relay substrate (drive circuit substrate) 12 connected to the first sensor sheet 20A and the second sensor sheet 20B via the pair of flexible wiring boards 14. For example, the base substrate 44 is an insulating layer formed of a resin such as polyethylene terephthalate (PET) or polyimide to a thickness of about 0.3 to 0.5 mm.

[0030] The first sensor sheet 20A and the second sensor sheet 20B each include a thin and long strip-shaped flexible sheet substrate 22 composed of an insulating layer and two layers of conductor patterns (sensor patterns) CDA, CDB (CDC, CDD) provided on the sheet substrate 22 (see Figure 2 ). The first sensor sheet 20A and the second sensor sheet 20B each have one end (front end) DE in the longitudinal direction X and the other end (base end) PE in the longitudinal direction X. The base end PE of the first sensor sheet 20A and the second sensor sheet 20B is connected to the relay substrate 12. The sensor pattern of each layer includes a plurality of strain gauges G0 to Gn. The plurality of strain gauges G0 to Gn are arranged in a row in the longitudinal direction X at predetermined intervals from the front end DE to the base end PE in the longitudinal direction X of the sheet substrate 22.

[0031] It should be noted that in the figure, the longitudinal direction X and the width direction Y of the sensor sheet represent two directions that are orthogonal to each other. These directions may intersect at an angle other than 90 degrees.

[0032] Figure 2 2 is a longitudinal sectional view of the strain gauge sensor device 10 .

[0033] like Figure 2 As shown, the base substrate 44 has a front surface and a back surface opposite to the front surface. For example, the first sensor sheet 20A is attached to the front surface of the base substrate 44 via an adhesive layer Ad such as a transparent adhesive sheet (OCA). The second sensor sheet 20B is attached to the back surface of the base substrate 44 via an adhesive layer Ad.

[0034] The relay substrate 12 includes a driving circuit 40 and a plurality of wirings provided on one surface side, and a plurality of wirings (not shown) provided on the other surface side. The first sensor pattern CDA and the second sensor pattern CDB of the first sensor sheet 20A are connected to the wirings provided on the upper surface side of the relay substrate 12 via the FPC 14. Similarly, the third sensor pattern CDC and the fourth sensor pattern CDD of the second sensor sheet 20B are connected to the wirings provided on the lower surface side of the relay substrate 12 via the FPC 14.

[0035] Figure 3 is along Figure 2 . As shown in the figure, the first sensor sheet 20A includes: a flexible belt-shaped sheet substrate 22, a first sensor pattern CDA (G0-Gn) provided on one surface of the sheet substrate 22, a first insulating layer IL1 overlapped with the first sensor pattern CDA and stacked on the sheet substrate 22, a second sensor pattern CDB (G0-Gn) provided on the first insulating layer IL1, a second insulating layer IL2 overlapped with the second sensor pattern CDB and stacked on the first insulating layer IL1, and a protective layer (surface protective film) PTL provided on the second insulating layer IL2. Exemplarily, the sheet substrate 22 is formed of polyimide, and the first and second insulating layers IL1 and IL2 are formed of silicon nitride (SiN). Exemplarily, one side of the protective layer PTL of the first sensor sheet 20A is bonded to the base substrate 44 via an adhesive layer Ad.

[0036] Similarly, the second sensor sheet 20B includes: a flexible belt-shaped sheet substrate 22, a fourth sensor pattern CDD provided on one surface of the sheet substrate 22, a first insulating layer IL1 overlapped with the fourth sensor pattern CDD and stacked on the sheet substrate 22, a third sensor pattern CDC provided on the first insulating layer IL1, a second insulating layer IL2 overlapped with the third sensor pattern and stacked on the first insulating layer IL1, and a protective layer (surface protective film) PTL provided on the second insulating layer IL2. Exemplarily, the sheet substrate 22 is formed of polyimide, and the first and second insulating layers IL1 and IL2 are formed of silicon nitride (SiN). Exemplarily, one side of the protective layer PTL of the second sensor sheet 20B is bonded to the base substrate 44 via an adhesive layer Ad.

[0037] The base substrate 44, the adhesive layer Ad, the first sensor sheet 20A and the second sensor sheet 20B are collectively referred to as a substrate, the strain gauge of the first sensor pattern CDA is referred to as a first strain gauge GA, the strain gauge of the second sensor pattern CDB is referred to as a second strain gauge GB, the strain gauge of the third sensor pattern CDC is referred to as a third strain gauge GC, and the strain gauge of the fourth sensor pattern CDD is referred to as a fourth strain gauge GD.

[0038] like Figure 3 As shown, the first strain gauge GA, the second strain gauge GB, the third strain gauge GC and the fourth strain gauge GD are arranged opposite to each other in the thickness direction Z of the substrate with the insulating layer sandwiched therebetween. When the center position of the thickness direction Z of the substrate is the center line C, the first strain gauge GA and the fourth strain gauge GD on the outside are arranged symmetrically with respect to the center line C, and the second strain gauge GB and the third strain gauge GC on the inside are arranged symmetrically with respect to the center line C. That is, when the interval between the first strain gauge GA on the outside and the center line C is d1, the interval between the fourth strain gauge GD on the outside and the center line C is d2, the interval between the second strain gauge GB on the inside and the center line C is d3, and the interval between the third strain gauge GC on the inside and the center line C is d4, it is preferred that d1=d2, and d3=d4. It is also possible that d1≠d3 and d2≠d4.

[0039] It should be noted that, in the substrate, the first sensor sheet 20A and the second sensor sheet 20B may also have a structure in which one side of each protective layer PTL is bonded to the base substrate 44 via an adhesive layer Ad. Figure 4 As shown, the base substrate may be omitted, and the first sensor sheet 20A and the second sensor sheet 20B may be bonded to each other via an adhesive layer Ad such as a transparent adhesive sheet (OCA).

[0040] Figure 5 2 is a plan view schematically showing the second sensor pattern CDB of the first sensor sheet 20A and the third sensor pattern CDC of the second sensor sheet 20B. Figure 6 2 is a perspective view schematically showing a stacked structure of the first sensor pattern CDA and the second sensor pattern CDB in the first sensor sheet 20A.

[0041] like Figure 5 As shown, according to the present embodiment, the first sensor sheet 20A and the second sensor sheet 20B are configured to have the same shape, size and sensor pattern. The pattern structure is described by taking the second sensor pattern CDB of the first sensor sheet 20A and the third sensor pattern CDC of the second sensor sheet 20B as representatives. Each sensor pattern has a plurality of strain gauges G0 to Gn. The plurality of strain gauges G0 to Gn are arranged in a row with a spacing L in the long side direction X from one end (front end) DE to the other end (base end) PE of the sheet substrate 22. Each of the strain gauges G0 to Gn extends in a meandering or rectangular wave shape in the width direction Y, and has one end (sometimes referred to as the first end) E1 and the other end (sometimes referred to as the second end) E2 in the width direction Y. Each strain gauge G0 to Gn has a desired resistance value and generates a resistance change corresponding to the strain.

[0042] Each sensor pattern includes a plurality of power lines VL0 to VLn, a plurality of ground lines GNL0 to GNLn, a plurality of first signal lines Sa0 to San, and a plurality of second signal lines Sb0 to Sbn extending in the longitudinal direction X along the columns of the strain gauges G0 to Gn.

[0043] The power lines VL0 to VLn are located on one end side of the strain gauges G0 to Gn. The power lines VL0 to VLn have one end connected to the first end E1 of the strain gauges G0 to Gn and the other end extending to the base end PE of the sheet base 22, and extend substantially parallel to each other.

[0044] The first signal lines Sa0 to San are located between one end of the strain gauges G0 to Gn and the power lines VL0 to VLn. The first signal lines Sa0 to San have one end connected to the first end E1 of the strain gauges G0 to Gn and the other end extending to the base end PE of the sheet substrate 22, and extend almost parallel to each other.

[0045] The ground wires GNL0 to GNLn are located on the other end side of the strain gauges G0 to Gn. The ground wires GNL0 to GNLn have one end connected to the second end E2 of the strain gauges G0 to Gn and the other end extending to the base end PE of the sheet base 22, and extend substantially parallel to each other.

[0046] The second signal lines Sb0 to Sbn are located between the other ends of the strain gauges G0 to Gn and the ground lines GNL0 to GNLn. The second signal lines Sb0 to Sbn respectively have one end connected to the second end E2 of the strain gauges G0 to Gn and the other end extending to the base end PE of the sheet substrate 22, and extend almost parallel to each other.

[0047] As described later, in this embodiment, the ground lines GNL0 to GNLn of the second sensor pattern CDB are electrically connected to the power lines VL0 to VLn of the third sensor pattern CDC via through holes SH at the positions of the relay substrate 12. Thus, the strain gauges of the second sensor pattern CDB are connected in series with the strain gauges of the third sensor pattern.

[0048] like Figure 2 and Figure 3 As shown, in the first sensor sheet 20A, the first sensor pattern CDA (G0-Gn) is formed on the sheet substrate 22, and the first insulating layer IL1 overlaps with the first sensor pattern CDA and is stacked on the sheet substrate 22. The second sensor pattern CDB is formed on the first insulating layer IL1, and the second insulating layer IL2 overlaps with the second sensor pattern CDB and is stacked on the first insulating layer IL1.

[0049] like Figure 6As shown, the strain gauges G0 to Gn of the second sensor pattern CDB are respectively located at positions opposing the strain gauges G0 to Gn of the first sensor pattern CDA in the thickness direction of the first sensor sheet 20A.

[0050] The power lines VL0~VLn, ground lines GNL0~GNLn, first signal lines Sa0~San and second signal lines Sb0~Sbn of the second sensor pattern CDB are respectively located at positions slightly offset in the width direction Y relative to the power lines VL0~VLn, ground lines GNL0~GNLn, first signal lines Sa0~San and second signal lines Sb0~Sbn of the first sensor pattern CDA.

[0051] The power lines VL0 to VLn, the ground lines GNL0 to GNLn, the first signal lines Sa0 to San, and the second signal lines Sb0 to Sbn of the second sensor pattern CDB respectively have a front end portion DA connected to the strain gauges G0 to Gn and a base end portion PA extending to the base end PE of the sheet substrate 22. Each front end portion DA is provided on the first insulating layer IL1, and the base end portion PA is provided on the sheet substrate 22. Each front end portion DA is electrically connected to the base end portion PA via a contact hole CH provided in the first insulating layer IL1.

[0052] In this way, the base end side portion PA of the power lines VL0~VLn, ground lines GNL0~GNLn, first signal lines Sa0~San and second signal lines Sb0~Sbn of the second sensor pattern CDB is located on the same plane as the power lines VL0~VLn, ground lines GNL0~GNLn, first signal lines Sa0~San and second signal lines Sb0~Sbn of the first sensor pattern CDA, that is, located on the sheet substrate 22, and is connected to the common wiring of FPC14.

[0053] The third sensor pattern CDC and the fourth sensor pattern CDD of the second sensor sheet 20B are formed in the same shape, the same size, and the same structure as the first sensor pattern CDA and the second sensor pattern CDB of the above-described first sensor sheet 20A.

[0054] like Figure 2As shown in FIG. 1 , the first sensor sheet 20A and the second sensor sheet 20B configured as above are attached to the front and back surfaces of the base substrate 44 and are opposed to each other with the base substrate 44 interposed therebetween. That is, the two layers of strain gauges G0 to Gn of the first sensor sheet 20A are opposed to the two layers of strain gauges G0 to Gn of the second sensor sheet 20B with the base substrate 44 interposed therebetween. Here, preferably, when viewed from a direction perpendicular to the surface of the base substrate 44, at least a portion of the strain gauges G0 to Gn of the first sensor sheet 20A and the strain gauges G0 to Gn of the second sensor sheet overlap each other. Alternatively, preferably, the strain gauges G0 to Gn of each of the sensor sheets 20A and 20B overlap while allowing at least a shift in the longitudinal direction X and without shifting in the width direction Y. Alternatively, more preferably, the strain gauges G0 to Gn of each of the sensor sheets 20A and 20B overlap while without shifting in both the longitudinal direction X and the width direction Y.

[0055] The wiring of the first sensor pattern CDA and the second sensor pattern CDB of the first sensor sheet 20A extends to the upper surface of the relay substrate 12 via the FPC 14. The wiring of the third sensor pattern CDC and the fourth sensor pattern CDD of the second sensor sheet 20B extends to the back surface of the relay substrate 12 via the FPC 14. In the present embodiment, the ground lines GNL0 to GNLn of the first sensor pattern CDA are electrically connected to the power lines VL0 to VLn of the fourth sensor pattern CDD through the plated through holes SH formed as connection lines on the relay substrate 12, respectively. In addition, the ground lines GNL0 to GNLn of the second sensor pattern CDB are electrically connected to the power lines VL0 to VLn of the third sensor pattern CDC through the plated through holes SH formed as connection lines on the relay substrate 12, respectively.

[0056] It should be noted that the connection wire is not limited to the plated through hole SH, and a wiring pattern on the relay substrate 12 or the like may be used. In addition, the following structure may be adopted: the FPC 14 on the second sensor sheet 20B side is also connected to the upper surface side of the relay substrate 12, so that the ground wires GNL0 to GNLn of the first sensor sheet 20A and the power supply wires VL0 to VLn of the second sensor sheet 20B are connected via the wiring on the relay substrate 12 instead of the plated through hole. In addition, the following structure may be adopted: the FPC 14 on the first sensor sheet 20A side and the FPC 14 on the second sensor sheet 20B side are connected to the drive circuit 40 provided on the upper surface side of the relay substrate 12, and the ground wires GNL0 to GNLn of the first sensor sheet 20A and the power supply wires VL0 to VLn of the second sensor sheet 20B are connected in the drive circuit 40.

[0057] Next, a driving circuit (controller) that drives the first sensor sheet 20A and the second sensor sheet 20B configured as described above will be described. Figure 7 is a block diagram schematically showing a drive circuit of the strain gauge sensor device 10, Figure 8 is a block diagram showing the first to fourth sensor patterns, the selector of the controller, and the analog front end. Figure 8 In order to simplify the drawing, the power lines VL0 to VLn of each sensor pattern are collectively represented as one power line, and the ground lines GNL0 to GNLn are collectively represented as one power line.

[0058] like Figure 7 As shown, the drive circuit 40 provided on the relay substrate (control circuit substrate) 12 includes a selector SEL, an analog front end (AFE: signal adjustment circuit) 30 , a timing controller 34 , a communication interface 36 , and the like.

[0059] The communication interface 36 is connected to an external host controller 38 wirelessly or by wire, receives a driving signal (Setting) from the host controller 38 , and sends detection data (Data) to the host controller 38 .

[0060] The timing controller 34 outputs a driving signal to the selector SEL and the analog front end 30 according to the driving signal (Setting).

[0061] The selector SEL is composed of a plurality of shift registers, multiplexers, etc. The selector SEL sequentially connects the power supply lines VL0 to VLn of the first and second sensor patterns CDA and CDB in the first sensor sheet 20A to the power supply according to the drive signal from the timing controller 34, and sequentially applies voltages Pw0 to Pwn to the strain gauges G0 to Gn. In synchronization with this, the selector SEL sequentially reads the detection signals (voltage values) Rxa0 to Rxan and Rxb0 to Rxbn of one end side and the other end side of the strain gauges G0 to Gn through the first signal lines Sa0 to San and the second signal lines Sb0 to Sbn.

[0062] The voltages Pw0 to Pwn supplied to the power lines VL0 to VLn of the first and second sensor patterns CDA and CDB are sequentially applied to the power lines VL0 to VLn of the third and fourth sensor patterns CDC and CDD via the ground lines GNL0 to GNLn and the connection line SH. In synchronization with the above reading, the selector SEL sequentially reads the detection signals (voltage values) Rxc0 to Rxcn and Rxd0 to Rxdn of one end side and the other end side of the strain gauges G0 to Gn via the first signal lines Sa0 to San and the second signal lines Sb0 to Sbn of the third and fourth sensor patterns CDC and CDD in the second sensor sheet 20B.

[0063] like Figure 8As shown, the analog front end 30 includes a readout circuit 31, differential detection circuits 30a and 30b, an AD converter 32, a digital filter 33, a memory 37, and the like. Fig. 9 : is a circuit diagram of a differential detection circuit in an analog front end. As shown in the figure, according to the present embodiment, the analog front end 30 includes a differential detection circuit (subtraction circuit) 30a for processing the detection signal of the first sensor sheet 20A and a differential detection circuit (subtraction circuit) 30b for processing the detection signal of the second sensor sheet 20B. The analog front end 30 performs signal adjustment (amplification, AD conversion, filtering) on ​​the detection signals Rxa, Rxb and the detection signals Rxc, Rxd of each strain gauge G0~Gn sent by the selector SEL according to the drive signal, and outputs them to the communication interface 36. At this time, the voltage drop value of each strain gauge G is required to calculate the curvature radius, so the difference of the detection values ​​Rxa, Rxb of each strain gauge G0~Gn and the difference of the detection values ​​Rxc, Rxd of the strain gauges G0~Gn are obtained through the differential detection circuits 30a and 30b, and the signal is output.

[0064] like Figure 7 As shown, the host controller 38 includes a reading circuit 38a, a memory 38b, an operation processing unit 38c, etc. The reading circuit 38a reads the output signal (differential data) sent by the communication interface 36 and stores it in the memory 38b. The operation processing unit 38c, such as a CPU, performs operation processing such as data shaping and surface calculation based on the differential data, and calculates the strain (curvature radius), surface morphology (surface coordinates), etc. of the object detected by the first and second sensor sheets 20A and 20B. The memory 38b stores the differential data, the calculated curvature radius, the surface morphology, the detection operation program, etc.

[0065] Next, the detection operation mode of the strain gauge sensor device 10 is described.

[0066] Fig.10 Schematically shows a state where the strain gauge sensor device 10 is set on the surface of the object 50 to be measured. As shown in the figure, the object 50 to be measured has a surface 50a curved in a wavy or sinusoidal shape. The strain gauge sensor device 10 is closely arranged on the surface 50a of the object 50 to be measured, and detects the curved surface morphology of the object 50. In this case, the strain gauge sensor device 10 is set in a state where the second sensor sheet 20B is in contact with the surface 50a of the object 50 to be measured. In addition, exemplarily, each sensor pattern of the first sensor sheet 20A and the second sensor sheet 20B has approximately 4 to 8 strain gauges G0 to Gn. The interval L between adjacent strain gauges is, for example, 5 to 20 mm, and more preferably approximately 10 to 15 mm.

[0067] Fig.11This is a diagram schematically showing a portion of the strain gauge sensor device 10 set on the surface 50a of the object 50. As shown in the figure, the neutral plane of the base substrate 44 is bent with a radius of curvature r when it is set on the surface 50a. The neutral plane refers to a surface that neither stretches (stretches) nor contracts (compresses) before and after the strain gauge sensor device is bent (that is, the strain after bending is zero). In this embodiment, the neutral plane is located at the center (thickness×1 / 2) of the thickness direction of the base substrate 44.

[0068] The strain gauge (sometimes referred to as the first strain gauge) GA of the first sensor pattern CDA and the strain gauge (sometimes referred to as the second strain gauge) GB of the second sensor pattern in the first sensor sheet 20A located on the outer peripheral side are opposed in the radial direction (thickness direction) with the insulating layer sandwiched therebetween. The strain gauge (sometimes referred to as the third strain gauge) GC of the third sensor pattern CDC and the strain gauge (sometimes referred to as the fourth strain gauge) GD of the fourth sensor pattern CDD in the second sensor sheet 20B located on the inner peripheral side are opposed in the radial direction (thickness direction) with the insulating layer sandwiched therebetween. That is, the four strain gauges GA, GB, GC, and GD stacked in four layers are spaced apart in the radial direction and opposed to each other. The strain gauge GA is located on the outermost periphery, the strain gauge GD is located on the innermost periphery, and the two layers of strain gauges GB and GC are located between them. When the interval d between the two layers of strain gauges facing each other is constant, the thickness of the strain gauge sensor device is 3d.

[0069] When the distance between the outermost strain gauge GA and the neutral plane is d1, the distance between the innermost strain gauge GD and the neutral plane is d2, the distance between the middle strain gauge GB and the neutral plane is d3, and the distance between the middle strain gauge GC and the neutral plane is d4, preferably d1=d2, and d3=d4. d1≠d3, d2≠d4 are also acceptable.

[0070] In the detection operation mode, the strain gauges G0 to Gn are driven in sequence by scanning the driving power line and the signal line, and the detection values ​​of the strain gauges G0 to Gn are read in sequence. In detail, during the detection, the timing controller 34 inputs the start signal and the clock signal synchronized therewith into the selector SEL according to the instruction from the host controller 38, and drives (Setting) the strain gauges G0 to Gn of the first and second sensor sheets 20A and 20B in sequence within one frame period.

[0071] like Figure 8As shown, the selector SEL first applies voltage to the two strain gauges GA and GD located on the outside and performs strain detection. The selector SEL drives the power line VL0 of the first sensor pattern CDA, that is, applies the power supply voltage to the power line VL0, and applies the desired voltage Pw0 to the strain gauge G0. As a result, the current I is energized to the strain gauge G0 for a certain period of time. At the same time, the selector SEL obtains the detection signal (voltage value) Rxa0 of one end of the strain gauge G0 and the detection signal (voltage value) Rxb0 of the other end of the strain gauge G0 via the first signal line Sa0 and the second signal line Sb0.

[0072] The ground line GNL0 of the first sensor pattern CDA is connected to the power line VL0 of the fourth sensor pattern CDD of the second sensor sheet 20B. More specifically, the strain gauge G0 (GA) of the first sensor pattern CDA and the strain gauge G0 (GD) of the fourth sensor pattern CDD are connected in series via the ground line GNL0 of the first sensor pattern CDA, the connection line (plated through hole) SH, and the power line VL0 of the fourth sensor pattern CDD. Therefore, when the strain gauge G0 of the first sensor pattern CDA is driven, the strain gauge G0 of the fourth sensor pattern CDD is synchronously driven, and the current I is also energized to the strain gauge G0. At the same time, the selector SEL obtains the detection signal (voltage value) Rxc0 of one end of the strain gauge G0 and the detection signal (voltage value) Rxd0 of the other end of the strain gauge G0 via the first signal line Sa0 and the second signal line Sb0 of the fourth sensor pattern CDD.

[0073] The acquired detection signals Rxa0, Rxb0, Rxc0 and Rxd0 are sent to the analog front end 30. The difference between the detection values ​​Rxa and Rxb is detected and adjusted by the differential detection circuit 30a. The difference between the detection values ​​Rxc and Rxd is detected and adjusted by the differential detection circuit 30b. The adjusted differential value is stored in the memory 37.

[0074] Then, the selector SEL drives the power line VL1 of the first sensor pattern CDA, and applies a desired voltage Pw1 to the strain gauge G1 of the first sensor pattern CDA and the strain gauge G1 of the fourth sensor pattern CDD, respectively. As a result, the current I is energized to the two opposing strain gauges G1 for a certain period of time. At the same time, the selector SEL obtains the detection signal Rxa1 of one end of the strain gauge G1 and the detection signal Rxb1 of the other end of the strain gauge G1 via the first signal line Sa1 and the second signal line Sb1 of the first sensor pattern CDA. At the same time, the selector SEL obtains the detection signal Rxc1 of one end of the strain gauge G1 and the detection signal Rxd1 of the other end of the strain gauge G1 via the first signal line Sa1 and the second signal line Sb1 of the fourth sensor pattern CDD.

[0075] The acquired detection signals Rxa1, Rxb1, Rxc1 and Rxd1 are sent to the analog front end 30. The difference between the detection values ​​Rxa and Rxb is detected and adjusted by the differential detection circuit 30a. The difference between the detection values ​​Rxc and Rxd is detected and adjusted by the differential detection circuit 30b. The adjusted differential value is stored in the memory 37.

[0076] Afterwards, the selector SEL sequentially drives the strain gauges G2~Gn of the first sensor pattern CDA and the strain gauges G2~Gn of the fourth sensor pattern CDD, and sequentially obtains the detection signals Rxa2~Rxan, Rxb2~Rxbn, Rxc2~Rxcn and Rxd2~Rxdn of the strain gauges G2~Gn. The acquired detection signals are sequentially sent to the analog front end 30, and after adjustment and differential detection, they are stored in the memory 37.

[0077] like Fig.12 As shown, next, the selector SEL applies voltage to the two strain gauges GB and GC located in the middle layer (inside) to detect strain. Fig.12 In order to simplify the drawing, the power lines VL0 to VLn of the sensor patterns are collectively represented as one power line, and the ground lines GNL0 to GNLn are collectively represented as one power line.

[0078] Specifically, the selector SEL drives the power line VL0 of the second sensor pattern CDB of the first sensor sheet 20A and applies a desired voltage Pw0 to the strain gauge G0. As a result, the current I flows through the strain gauge G0 for a certain period of time. At the same time, the selector SEL obtains a detection signal (voltage value) Rxa0 at one end of the strain gauge G0 and a detection signal (voltage value) Rxb0 at the other end of the strain gauge G0 via the first signal line Sa0 and the second signal line Sb0.

[0079] The ground line GNL0 of the second sensor pattern CDB is connected to the power line VL0 of the third sensor pattern CDC of the second sensor sheet 20B. More specifically, the strain gauge G0 (GB) of the second sensor pattern CDB and the strain gauge G0 (GC) of the third sensor pattern CDC are connected in series via the ground line GNL0 of the second sensor pattern CDB, the connection line (plated through hole) SH, and the power line VL0 of the third sensor pattern CDC. Therefore, when the strain gauge G0 of the second sensor pattern CDB is driven, the strain gauge G0 of the third sensor pattern CDC is synchronously driven, and the current I is also energized to the strain gauge G0. At the same time, the selector SEL acquires the detection signal (voltage value) Rxc0 of one end of the strain gauge G0 and the detection signal (voltage value) Rxd0 of the other end of the strain gauge G0 via the first signal line Sa0 and the second signal line Sb0 of the third sensor pattern CDC.

[0080] The acquired detection signals Rxa0, Rxb0, Rxc0 and Rxd0 are sent to the analog front end 30. The difference between the detection values ​​Rxa and Rxb is detected and adjusted by the differential detection circuit 30a. The difference between the detection values ​​Rxc and Rxd is detected and adjusted by the differential detection circuit 30b. The adjusted differential value is stored in the memory 37.

[0081] Then, the selector SEL drives the power line VL1 of the second sensor pattern CDB, and applies a desired voltage Pw1 to the strain gauge G1 of the second sensor pattern CDB and the strain gauge G1 of the third sensor pattern CDC, respectively. As a result, the current I is energized to the two opposing strain gauges G1 for a certain period of time. At the same time, the selector SEL obtains the detection signal Rxa1 of one end of the strain gauge G1 and the detection signal Rxb1 of the other end of the strain gauge G1 via the first signal line Sa1 and the second signal line Sb1 of the second sensor pattern CDB. At the same time, the selector SEL obtains the detection signal Rxc1 of one end of the strain gauge G1 and the detection signal Rxd1 of the other end of the strain gauge G1 via the first signal line Sa1 and the second signal line Sb1 of the third sensor pattern CDC.

[0082] The acquired detection signals Rxa1, Rxb1, Rxc1 and Rxd1 are sent to the analog front end 30. The difference between the detection values ​​Rxa and Rxb is detected and adjusted by the differential detection circuit 30a. The difference between the detection values ​​Rxc and Rxd is detected and adjusted by the differential detection circuit 30b. The adjusted differential value is stored in the memory 37.

[0083] After that, the selector SEL sequentially drives the strain gauges G2~Gn of the second sensor pattern CDB and the strain gauges G2~Gn of the third sensor pattern CDD, and sequentially obtains the detection signals Rxa2~Rxan, Rxb2~Rxbn, Rxc2~Rxcn and Rxd2~Rxdn of the strain gauges G2~Gn. The acquired detection signals are sequentially sent to the analog front end 30, and after adjustment and differential detection, they are stored in the memory 37.

[0084] As described above, the analog front end 30 sequentially reads out the sent detection signals Rxa1~Rxan, Rxb1~Rxbn and detection signals Rxc1~Rxcn, Rxd1~Rxdn through the readout circuit 31, and converts them into voltage signals, and then converts them into digital data through the AD converter 32 and the digital filter 33. In addition, the analog front end 30 detects the difference between the detection signals Rxa0~Rxan and Rxb0~Rxbn, and the difference between the detection signals Rxc0~Rxcn and Rxd0~Rxdn through the differential detection circuits 30a and 30b. The detected differential data is sequentially stored in the memory 37. When the scanning of one frame period is completed, the analog front end 30 reads out the differential data of one frame from the memory 37 and outputs it to the host controller 38. The host controller 38 calculates the curved surface morphology of the surface 50a of the object 50 to be measured based on the sent data.

[0085] For the curved surface morphology, illustratively, a method for calculating the radius of curvature is described.

[0086] Fig.13A It is a schematic diagram showing the use of Fig.11 The cross-sectional view of the strain gauge sensor in which the radius of curvature is calculated using the detection values ​​of the two middle (inner) layers of strain gauges GB and GC among the four layers of strain gauges shown. Fig. 13B It is a schematic diagram showing the use of Fig.11 A cross-sectional view of a strain gauge sensor in which the radius of curvature is calculated based on the detection values ​​of the strain gauges GA and GD in the outermost inner layer (outer side) of the four-layer strain gauge. The strain gauges GA and GB located on the outer side and the strain gauges GC and GD located on the inner side are opposed in the radial direction (the thickness direction of the substrate) and are curved with different radii of curvature.

[0087] exist Fig.13A , 13B In the mathematical formula shown below, 3d represents the thickness of the substrate, θ represents the strain gauge opening angle, r represents the radius of curvature of the neutral plane, k represents the gauge factor, R0 represents the initial resistance of the strain gauge, and ΔR0 and ΔR'0 represent the resistance change of the strain gauge.

[0088] The following describes the calculation of the curvature radius based on the detection values ​​of the strain gauges GB and GC. Fig.13A As shown, if the length of the strain gauge on the neutral plane of the base substrate 44 in the long side direction X is the initial length of the strain gauge, the middle outer strain gauge GB is bent and deformed to a state of length extension, and the middle inner strain gauge GC is bent and deformed to a state of length reduction.

[0089] If the initial resistance value of strain gauges GB and GC before deformation is R0, the measured voltage of strain gauge GB after deformation (the difference between the voltage value at one end of the strain gauge and the voltage value at the other end) is V B, the measured voltage of the strain gauge GC after deformation is V C , the resistance change of the strain gauge is ΔR0, and the current flowing through the strain gauges GB and GC is I, then the measured voltage V of the strain gauge GB is B and the measured voltage V of the strain gauge GC C as follows:

[0090] .

[0091] If the relationship between the resistance change of the strain gauge and the potential difference between the two ends of each strain gauge is expressed by the following formula:

[0092] .

[0093] Based on the above formula, the rate of change of the strain gauge resistance is calculated by the following formula:

[0094] .

[0095] According to the above relationship, the calculation formula of the curvature radius r of the neutral surface is as follows:

[0096] .

[0097] Fig.14 The curvature radii (curved surface coordinates) P0 to P1 calculated based on the detection values ​​of the strain gauges GB and GC at the positions of the plurality of strain gauges G0 to Gn of the strain gauge sensor device 10 are shown. n The surface shape obtained by drawing.

[0098] A description will be given of a case where the curvature radius is calculated based on the detection values ​​of the strain gauges GA and GD.

[0099] like Fig. 13B As shown, if the length of the strain gauge on the neutral surface of the base substrate 44 in the long side direction X is the initial length of the strain gauge, the outermost strain gauge GA is bent and deformed to a state of length extension, and the innermost strain gauge GD is bent and deformed to a state of length reduction.

[0100] If the initial resistance value of the strain gauges GA and GD before deformation is R0, the measured voltage of the strain gauge GA after deformation (the difference between the voltage value at one end of the strain gauge and the voltage value at the other end) is V A , the measured voltage of the strain gauge GD after deformation is V D , the resistance change of the strain gauge is ΔR'0, and the current flowing through the strain gauges GA and GD is I', then the measured voltage V of the strain gauge GA is A and the resistance value V of the strain gauge GD D as follows:

[0101] .

[0102] If the relationship between the resistance change of the strain gauge and the potential difference between the two ends of each strain gauge is expressed by the following formula:

[0103] .

[0104] Based on the above formula, the rate of change of the strain gauge resistance is calculated by the following formula:

[0105] .

[0106] According to the above relationship, the calculation formula of the curvature radius r' of the neutral surface is as follows:

[0107] .

[0108] Fig.15 The curvature radii P'0 to P'1 calculated based on the detection values ​​of the strain gauges GA and GD at the positions of the plurality of strain gauges G0 to Gn of the strain gauge sensor device 10 are shown. n The surface shape obtained by drawing.

[0109] The host controller 38 calculates the curved surface shape of the surface 50a of the object 50 based on the transmitted data. The curvature radii (curved surface coordinates) P0 to P1 calculated based on the detection values ​​of the strain gauges GB and GC are n The curvature radius (surface coordinates) P'0~P' calculated based on the detection values ​​of the strain gauges GA and GD n The average value ((P0+P'0) / 2, (P1+P'1) / 2, (P2+P'2) / 2...) is calculated to obtain the curvature radius (surface coordinates) of each part as the final data. Fig.16 The curvature radii P0 to P0 calculated as the final data are shown. n The surface shape obtained by drawing.

[0110] Therefore, the strain gauge sensor device 10 can detect the curved surface shape of the entire surface 50 a by sequentially calculating the curvature radii at a plurality of locations on the surface 50 a .

[0111] Next, the formation material of the sensor pattern including the strain gauge is described.

[0112] When the strain gauge GB and the strain gauge GC, and the strain gauge GA and the strain gauge GD of the strain gauge sensor device are formed of the same material and the same resistance value, the closer the strain gauge is to the neutral plane, the smaller the dynamic range of the output value is. Therefore, by making the resistance value of the strain gauge on the inner side close to the neutral plane larger than the resistance value of the strain gauge on the outer side, the dynamic range of the output value of the inner strain gauge can be increased.

[0113] Exemplarily, among the four-layer strain gauges, the strain gauge GB of the second sensor pattern CDB located on the inner side, i.e., located on the center (neutral plane) side in the thickness direction of the strain gauge sensor device, and the strain gauge GC of the third sensor pattern CDC are formed of the same material, and are formed of a material with a large resistance value, such as titanium. Among the four-layer strain gauges, the strain gauge GA of the first sensor pattern CDA located on the outer side, i.e., located away from the center (neutral plane) in the thickness direction of the strain gauge sensor device, and the strain gauge GD of the fourth sensor pattern CDD are formed of the same material, and are formed of a material with a small resistance value, such as aluminum. In this way, the strain gauges GB and GC on the inner side are formed of different materials from the strain gauges GA and GD on the outer side, and the strain gauges GB and GC on the inner side are formed to have a higher resistance than the strain gauges GA and GD on the outer side.

[0114] In the case of this structure, by setting the resistance values ​​of the inner strain gauges GB and GC and the outer strain gauges GA and GD to the optimal resistance values, as shown in FIG. Fig.17 As shown, the dynamic range of the inner strain gauge can be increased and set to the same range as the dynamic range of the outer strain gauge. Therefore, the dynamic range of the inner strain gauges GB and GC can be expanded, and the quantization error during strain detection can be reduced.

[0115] It should be noted that, in the case of a meander-shaped or rectangular-wave-shaped strain gauge, the resistance value increases by increasing the number of teeth. Therefore, by forming the strain gauges GA, GB, GC, and GD with the same material and making the number of teeth of the inner strain gauges GB and GC larger than the number of teeth of the outer strain gauges GA and GD, the inner strain gauges GB and GC can also have a high resistance.

[0116] According to the strain gauge sensor device 10 of the present embodiment configured as above, the two layers of strain gauges G0 to Gn of the first sensor sheet 20A and the two layers of strain gauges G0 to Gn of the second sensor sheet 20B are opposed to each other in the thickness direction of the substrate, and the strain gauges of the first sensor sheet and the second sensor sheet are connected in series by connecting the power line of the first sensor sheet and the ground line of the second sensor sheet. Therefore, the strain gauges G0 to Gn of the second sensor sheet can be sequentially driven (scanned) in synchronization with the sequential driving (scanning) of the strain gauges G0 to Gn of the first sensor sheet, and strain detection can be performed on the same position at the same time by the two strain gauges facing each other. In addition, during detection, a constant current I can be supplied to the two opposing strain gauges, and the curved surface morphology can be detected with high accuracy by obtaining the difference between the detection signals of the two strain gauges.

[0117] Furthermore, according to the present embodiment, the strain gauge sensor device includes a plurality of layers, here four layers, of strain gauges GA, GB, GC, and GD arranged overlapping in the thickness direction, and the average value of the detection values ​​detected by each pair, for example, the strain gauges GA and GD and the detection values ​​detected by the strain gauges GB and GC is obtained as the final detection data. In this way, by using the average value of the detection values ​​detected at a plurality of different positions in the thickness direction, the strain gauge sensor device can detect the curved surface morphology of the object to be measured with higher accuracy.

[0118] In summary, according to this embodiment, a strain detection device capable of improving detection accuracy can be obtained.

[0119] It should be noted that, although the embodiments of the present invention have been described, the embodiments are presented as examples and are not intended to limit the scope of the invention. The new embodiments can be implemented in various other ways, and various omissions, substitutions, and changes can be made without departing from the scope of the purpose of the invention. The embodiments or their modifications are included in the scope or purpose of the invention, and are included in the invention described in the claims and the scope of their equivalents.

[0120] Based on the above-described configurations as embodiments of the present invention, all configurations obtained by appropriately changing and implementing designs by those skilled in the art also fall within the scope of the present invention as long as the gist of the present invention is included.

[0121] For example, the number of layers of the sensor pattern in the strain gauge sensor device, that is, the number of layers of the strain gauge, is not limited to four layers, and may be six layers, eight layers, ten layers or more layers. The number of arrays of strain gauges in the sensor pattern of the sensor sheet is not limited to the above-mentioned embodiment, and may be selected arbitrarily. The constituent material, size and shape of the sensor sheet are not limited to the above-mentioned embodiment, and may be appropriately changed. The connection line connecting the power line and the ground line is not limited to the plated through hole, and may also be composed of the wiring in the selector SEL.

Claims

1. A strain detection device, comprising: a flexible substrate including a plurality of insulating layers; A first sensor pattern includes a plurality of first strain gauges arranged in a row at intervals in a first direction and a plurality of wirings respectively connected to the first strain gauges, wherein the first sensor pattern is disposed on the substrate; a second sensor pattern including a plurality of second strain gauges arranged in a row at intervals in the first direction and a plurality of wirings respectively connected to the second strain gauges, the second sensor pattern being stacked on the substrate and facing the first sensor pattern with an insulating layer interposed therebetween; a third sensor pattern including a plurality of third strain gauges arranged in a row at intervals in the first direction and a plurality of wirings respectively connected to the third strain gauges, the third sensor pattern being stacked on the substrate and facing the second sensor pattern with an insulating layer interposed therebetween; a fourth sensor pattern including a plurality of fourth strain gauges arranged in a row at intervals in the first direction and a plurality of wirings respectively connected to the fourth strain gauges, the fourth sensor pattern being stacked on the substrate and facing the third sensor pattern with an insulating layer interposed therebetween; as well as a controller that applies voltage to the first strain gauge, the second strain gauge, the third strain gauge, and the fourth strain gauge via the plurality of wirings and reads a detection value of each strain gauge, The first strain gauge, the second strain gauge, the third strain gauge, and the fourth strain gauge are arranged opposite to each other in the thickness direction of the substrate. The first strain gauge and the fourth strain gauge are symmetrically arranged with respect to a center position in a thickness direction of the substrate, and the second strain gauge and the third strain gauge are symmetrically arranged with respect to a center position in a thickness direction of the substrate.

2. The strain detection device according to claim 1, wherein: The plurality of wirings of the first sensor pattern include a plurality of power lines and a plurality of first signal lines respectively connected to the first ends of the first strain gauges, and a plurality of ground lines and a plurality of second signal lines respectively connected to the second ends of the first strain gauges. The plurality of wirings of the fourth sensor pattern include a plurality of power lines and a plurality of first signal lines respectively connected to the first ends of the fourth strain gauges, and a plurality of ground lines and a plurality of second signal lines respectively connected to the second ends of the fourth strain gauges. The first strain gauges are each connected in series with the fourth strain gauge via a ground line of the first sensor pattern and a power line of the fourth sensor pattern.

3. The strain detection device according to claim 2, wherein: The plurality of wirings of the second sensor pattern include a plurality of power lines and a plurality of first signal lines respectively connected to the first ends of the second strain gauges, and a plurality of ground lines and a plurality of second signal lines respectively connected to the second ends of the second strain gauges. The plurality of wirings of the third sensor pattern include a plurality of power lines and a plurality of first signal lines respectively connected to one end of the third strain gauge, and a plurality of ground lines and a plurality of second signal lines respectively connected to the other end of the third strain gauge. The second strain gauges are each connected in series with the third strain gauge via a ground line of the second sensor pattern and a power line of the third sensor pattern.

4. The strain detection device according to claim 3, wherein: The controller calculates a first measurement value based on a difference value between detection values ​​of the first strain gauge and the fourth strain gauge, calculates a second measurement value based on a difference value between detection values ​​of the second strain gauge and the third strain gauge, and calculates an average value of the first measurement value and the second measurement value.

5. The strain detection device according to claim 2, wherein: The second strain gauge and the third strain gauge are arranged on one side of the center in the thickness direction of the substrate relative to the first strain gauge and the fourth strain gauge. The resistance of the second strain gauge and the third strain gauge is high resistance compared to the resistance of the first strain gauge and the fourth strain gauge.

6. The strain detection device according to claim 5, wherein: The resistance of the second strain gauge is the same as the resistance of the third strain gauge, and the resistance of the first strain gauge is the same as the resistance of the fourth strain gauge.

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