JPWO2017057598A1 - Capacitive sensor - Google Patents

Abstract

The capacitive sensor (1) is a pair of an elastomeric dielectric layer (20) and a pair of electrode layers (01X to 08X, 01Y to 08Y) that are arranged with the dielectric layer (20) sandwiched in the thickness direction. The electrode units (30, 40) are provided, and the pressure sensitive part (D) is set in a part where the electrode layers (01X to 08X, 01Y to 08Y) face each other with the dielectric layer (20) therebetween. In a pressure range greater than 0 MPa and less than or equal to 0.015 MPa, the sensitivity of the capacitive sensor (1) is 7.5 × 10 −11 F / MPa to 7.5 × 10 −10 F / MPa, and the dielectric layer (20 ) Satisfies the pressure-strain curve represented by the following formula (I). Pk = ε0 × S / (d0 × a) × {εrk / (1-k) −εr0} (I)

Description

  The present invention relates to a capacitive sensor used as, for example, a load distribution sensor or a touch sensor.

  As the dielectric layer of the capacitive sensor, resin, elastomer, foamed material thereof, or the like is used. In order to detect a small load using a capacitance type sensor, the change in the thickness of the dielectric layer is large even with a small load, that is, the spring constant in the load input direction of the dielectric layer (= load change amount / deformation amount). Hereinafter, it is simply referred to as “spring constant”). For this reason, for example, as disclosed in Patent Document 1, a foam having a small spring constant is often used as a dielectric layer for detecting a small load as compared with a solid body.

JP2015-007562A JP 2012-173100 A JP 2010-223953 A Japanese Utility Model Publication No. 5-35303 Japanese Patent Laid-Open No. 62-298736 Japanese Patent No. 4944190

FIG. 21 shows an example of a pressure-strain curve when a conventional dielectric layer made of urethane foam is compressed in the thickness direction. In FIG. 21, the vertical axis represents the pressure applied to the dielectric layer, and the horizontal axis represents the strain of the dielectric layer. In this specification, the “strain” of the dielectric layer is a ratio of the deformation length Δd to the initial length (no load state) length d ₀ when the dielectric layer is compressed in the thickness direction ( Δd / d ₀ ). The pressure-strain curve corresponds to a so-called SS (stress-strain) curve.

  As shown in FIG. 21, the pressure-strain curve of the conventional dielectric layer has two inflection points. For this reason, the behavior of displacement with respect to pressure is different between a region where the pressure is low and a region where the pressure is large. For example, in a region where the strain is small, the pressure rise is large. In other words, the strain hardly changes in the region where the pressure is small. That is, the amount of displacement is small. As described above, according to the conventional dielectric layer, since the change in the capacitance is small in the region where the pressure is small, the small load cannot be accurately detected.

  In this regard, Patent Document 2 discloses a dielectric layer made of a foam having a plurality of through holes penetrating in the thickness direction. By forming the through-hole, the spring constant of the entire dielectric layer becomes small, and it becomes easy to detect a small load. However, if the spring constant is too small, the dielectric layer is crushed above a certain load, and a load beyond that cannot be detected. In addition, the relative dielectric constant of the entire dielectric layer is reduced by the amount of the through hole. For this reason, it is necessary to increase the electrode area in order to obtain a desired capacitance. In this case, the number of pressure-sensitive portions in the entire sensor must be reduced, and measurement with high resolution is difficult.

  On the other hand, Patent Document 3 discloses a columnar dielectric layer made of a solid body. Also in this case, since the spring constant of the dielectric layer becomes small, it becomes easy to detect a small load. However, since the dielectric layer is crushed when the load increases, it is difficult to detect a large load. In addition, since the height of the column is extremely small, it is difficult to manufacture the column with high accuracy, which may cause variations in output.

  Patent Document 6 discloses a capacitive sensor having a first electrode layer and a second electrode layer separated by a dielectric structure. In the dielectric structure, a plurality of dielectric elements are spaced apart from each other in order to form a gap between the first electrode layer and the second electrode layer. The sensor described in Patent Document 6 is used as a tactile input device, and gives a feeling of operation (tactile feedback) to an input person when a dielectric element is crushed by a predetermined load and further falls. It is aimed. The sensor described in Patent Document 6 is not suitable as a load sensor for detecting a small load to a large load because the dielectric element is easily crushed. Further, according to paragraph [0037] of Patent Document 6, it is described that the sensor has a dual aspect of a state in which the signal intensity increases linearly and a state in which the signal intensity increases nonlinearly with an increase in pressure. Yes. This feature is nothing but the subject of the present invention that “the behavior of displacement with respect to pressure differs between a region where the pressure is low and a region where the pressure is large”.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a capacitive sensor that has a wide load detection range and can detect a small load with high accuracy.

In order to solve the above problems, a capacitive sensor of the present invention includes an elastomeric dielectric layer, and a pair of electrode units each having an electrode layer disposed between the dielectric layer in the thickness direction. A capacitive sensor in which a pressure-sensitive portion is set at a portion where the electrode layer faces through the dielectric layer, and the capacitance sensor is in a pressure range of greater than 0 MPa and less than or equal to 0.015 MPa. The sensitivity is 7.5 × 10 ⁻¹¹ F / MPa or more and 7.5 × 10 ⁻¹⁰ F / MPa or less, and the dielectric layer satisfies the pressure-strain curve represented by the following formula (I): To do.
_{P k = ε 0 × S /} (d 0 × a) × {ε rk / (1-k) -ε r0} ··· (I)
k: Strain when the dielectric layer is compressed in the thickness direction [-]
P _k : Pressure applied to the dielectric layer compressed with strain k [MPa]
S: Electrode area in pressure-sensitive part [m ² ]
d ₀ : thickness of dielectric layer before compression [m]
a: Sensitivity of capacitive sensor [F / MPa]
ε ₀ : dielectric constant of vacuum [F / m]
ε _r0 : relative dielectric constant [−] of the dielectric layer before compression
ε _rk : dielectric constant of the dielectric layer when compressed with strain k [−]
Here, the electrode area in the pressure-sensitive portion is the total area of a pair of electrode layers facing each other with the dielectric layer interposed therebetween. When there are a plurality of pressure-sensitive parts, the electrode area is one of them.

  The present inventor conducted extensive research on a dielectric layer capable of detecting a small load more accurately, and obtained an ideal pressure-strain curve required for the dielectric layer. Below, the derivation | leading-out method of the ideal pressure-strain curve shown by said Formula (I) is demonstrated.

First, when the dielectric layer is compressed at a certain pressure, when the pressure is P _k [MPa] and the strain is k [−], the capacitance C _k [F] is expressed by the following equation (a).
C _k = ε ₀ ε _rk S / d _k (a)
S: Area of electrodes facing each other across the dielectric layer [m ² ]
ε ₀ : dielectric constant of vacuum [F / m]
ε _rk : dielectric constant of the dielectric layer when compressed with strain k [−]
d _k : thickness of dielectric layer when compressed with strain k [m]
Here, when the thickness of the dielectric layer in a no-load state before compression is d ₀ [m], d _k = d ₀ × (1−k) can be expressed. Therefore, the equation (a) is expressed by the following equation (b): Become.
C _k = ε ₀ ε _rk S / {d ₀ × (1-k)} (b)
Next, the relationship between the ideal pressure and electrostatic capacity as a sensor (the behavior of the electrostatic capacity with respect to the pressure) is as follows. The sensitivity of the sensor is 7.5 × 10 ⁻¹¹ F / MPa or more in the pressure range to be measured. It is 5 × 10 ⁻¹⁰ F / MPa or less and the capacitance changes linearly with respect to pressure. These are expressed by the following formula (c).
C _k = a × P _k + b (c)
a: Sensor sensitivity [F / MPa]
Here, since b is a capacitance in a no-load state (strain k = 0), when the relative dielectric constant of the dielectric layer in the no-load state before compression is ε _r0 [−], from the equation (a), b = ε ₀ ε _r0 S / d ₀ Substituting this into equation (c) yields the following equation (d).
_{C k = a × P k +} ε 0 ε r0 S / d 0 ··· (d)
From the equations (b) and (d), the following equation (e) is derived.
ε ₀ ε _rk S / {d ₀ × (1−k)} = a × P _k + ε ₀ ε _r0 S / d ₀ (e)
When formula (e) is transformed, the following formula (f) is obtained.
P _k = ε ₀ ε _rk S / {d ₀ × (1−k) × a} −ε ₀ ε _r0 S / (d ₀ × a) (f)
When the constant term and the variable term in the formula (f) are separately expressed, the above formula (I) is obtained.
_{P k = ε 0 × S /} (d 0 × a) × {ε rk / (1-k) -ε r0} ··· (I)
For example, when the relative dielectric constant of the dielectric layer is constant regardless of the strain k, ε _rk = ε _r0 is substituted into the equation (f) to obtain the following equation (g).
_{P k = ε 0 ε r0 S} / {d 0 × (1-k) × a} -ε 0 ε r0 S / (d 0 × a)
= Ε ₀ ε _r0 S / (d ₀ × a) × 1 / (1-k) −ε ₀ ε _r0 S / (d ₀ × a) (g)
When the constant term ε ₀ ε _r0 S / (d ₀ × a) in equation (g) is α and −ε ₀ ε _r0 S / (d ₀ × a) is β, the following equation (II) is obtained (β = −α).
P _k = α × 1 / (1-k) + β (II)
Therefore, when the relative dielectric constant of the dielectric layer is constant regardless of the strain k, the above formula (I) is expressed by the formula (II).

In FIG. 1, the model figure of the pressure-strain curve shown by Formula (I) is shown. In FIG. 1, the vertical axis represents the pressure (P _k ) applied to the dielectric layer, and the horizontal axis represents the strain (k) of the dielectric layer. As shown in FIG. 1, the pressure-strain curve represented by the formula (I) does not have a rising portion in a region where the pressure is low as seen in a conventional dielectric layer, and increases monotonously in a wide pressure range. To do. Therefore, the capacitance type sensor satisfying the pressure-strain curve of the formula (I) exhibits a behavior in which the capacitance changes linearly with respect to pressure in a wide range from a small load to a large load. That is, even in a region where the pressure is small, since the change in capacitance is large, a small load can be accurately detected.

The determination as to whether the dielectric layer satisfies the formula (I) may be performed as follows. First, the dielectric layer is compressed at a plurality of pressures in the range of greater than 0 MPa and less than or equal to 0.015 MPa, and the strain with respect to each pressure is measured. In addition, the relative dielectric constant of the dielectric layer at the measured strain is measured. Further, the sensor is configured by disposing electrode layers on both sides in the thickness direction of the dielectric layer, and the sensitivity of the sensor is calculated based on the amount of change in capacitance with respect to the amount of change in pressure. Next, the measured strain (k) and relative dielectric constant (ε _rk ) of the dielectric layer, sensor sensitivity (a), electrode area (S), etc. are substituted into equation (I), and the strain (k) Calculate the pressure (P _k ). Then, the degree of coincidence is calculated by the following formula (III) using the actual measurement value (P _m ) and the calculated value (P _c ) of the pressure having the same strain.
Consistency = actual measurement value of pressure (P _m ) / calculated value of pressure (P _c ) (III)
Here, the degree of coincidence becomes 1 if the actual measurement value and the calculated value completely coincide. The more the two deviate from each other, the greater the coincidence value is or a smaller value. In the present invention, if the degree of coincidence is not less than 0.3 and not more than 3.0, it is considered that the measured value of pressure and the calculated value coincide. Therefore, the dielectric layer satisfies the formula (I) when both the maximum value and the minimum value are within the range of 0.3 to 3.0 among the degrees of coincidence calculated for a plurality of strain values. Judge that.

In the formula (I), the dielectric constants ε _r0 and ε _rk of the dielectric layer vary depending on the material and shape of the dielectric layer. The sensor sensitivity a is considered to depend on the shape of the dielectric layer and the relative dielectric constant. For this reason, the pressure-strain curve of Formula (I) can be satisfied by adjusting the material and shape of the dielectric layer, the electrode area, and the like. For example, even when the dielectric layer is formed of a solid body having a relatively large spring constant or a high-density foam, the load is repeatedly applied by satisfying the pressure-strain curve of formula (I) by devising the shape and the like. It is possible to realize a capacitance type sensor that is difficult to sag even when applied and that can accurately detect a small load.

It is a model figure of the pressure-strain curve shown by Formula (I). It is a permeation | transmission top view of the capacitive type sensor of 1st embodiment. It is a perspective exploded view of the same capacitive sensor. It is a vertical direction sectional view of one protrusion of the dielectric layer. It is a perspective exploded view of the dielectric layer in the capacitive sensor of the second embodiment. It is an up-down direction sectional view of a part of the second dielectric layer constituting the dielectric layer. It is a perspective view of the dielectric layer in the capacitive sensor of 3rd embodiment. It is an up-down direction sectional view for one protrusion of the dielectric layer. It is a graph of the pressure-strain curve measured in the dielectric layer of Examples 1-6 and Comparative Example 1. 4 is a graph showing a calculation line and an actual measurement value of a pressure-strain curve of the dielectric layer of Example 1. It is a graph which shows the calculation line and actual value of the pressure-strain curve of the dielectric layer of Example 2. It is a graph which shows the calculation line and measured value of the pressure-strain curve of the dielectric layer of Example 3. It is a graph which shows the calculation line and measured value of the pressure-strain curve of the dielectric layer of Example 4. It is a graph which shows the calculation line and actual value of the pressure-strain curve of the dielectric layer of Example 5. It is a graph which shows the calculation line and actual value of the pressure-strain curve of the dielectric layer of Example 6. 4 is a graph showing a pressure-strain curve calculation line and an actual measurement value of a dielectric layer of Comparative Example 1; It is the graph which plotted the coincidence degree of the dielectric layer of Examples 1-6 and the comparative example 1 with respect to the actually measured pressure. It is a graph which shows the output of the electrostatic capacitance type sensor of Examples 1-3. It is a graph which shows the output of the capacitive type sensor of Examples 4-6. 6 is a graph showing an output of a capacitive sensor of Comparative Example 1. It is a model figure of the pressure-strain curve of the conventional dielectric layer. It is a perspective exploded view of the capacitive sensor of the fourth embodiment. It is a cross-sectional schematic diagram of the XXIII-XXIII direction in FIG. It is a vertical direction sectional view of a part of the second dielectric layer in the capacitive sensor of the fourth embodiment. It is a perspective exploded view of the capacitive sensor of the fifth embodiment. It is a perspective exploded view of the dielectric layer in the capacitive sensor of the sixth embodiment. It is an up-down direction sectional view of a part of the second dielectric layer constituting the dielectric layer. It is the schematic of the measuring apparatus of the dielectric constant of the dielectric layer of Examples 7-9. It is the schematic of the measuring apparatus of the displacement amount of the dielectric layer of Examples 7-9. It is a graph of the pressure-strain curve measured in the dielectric layer of Examples 7-9 and the comparative example 1. FIG. It is a graph which shows the calculation line and measured value of the pressure-strain curve of the dielectric layer of Example 7. It is a graph which shows the calculation line and measured value of the pressure-strain curve of the dielectric layer of Example 8. It is a graph which shows the calculation line and measured value of the pressure-strain curve of the dielectric layer of Example 9. FIG. It is the graph which plotted the coincidence degree of the dielectric layer of Examples 7-9 with respect to the measured pressure. It is a graph which shows the output of the capacitive type sensor of Examples 7-9.

1: capacitive sensor, 10: connector, 20: dielectric layer, 21: flat plate portion, 22: protrusion, 23: third dielectric layer, 30: first electrode unit, 31: first substrate, 32: First composite unit, 33: first electrode unit, 34: first dielectric layer, 35: flat plate part, 36: fine wire part, 40: second electrode unit, 41: second substrate, 42: second composite unit, 43: second electrode unit, 44: second dielectric layer, 45: flat plate portion, 46: fine wire portion, 50: dielectric layer, 51: first dielectric layer, 52: second dielectric layer, 53: dielectric layer, 54: First dielectric layer, 55: second dielectric layer, 60: dielectric layer, 61: flat plate portion, 62: corrugated portion, 510: flat plate portion, 511: strip-shaped column portion, 520: flat plate portion, 521: strip-shaped column portion, 540 : Flat plate portion, 541: fine wire portion, 550: flat plate portion, 551: fine wire portion, 620: ridge, 01X to 08 : First electrode layer, 01X～08x: first wiring layer, 01Y～08Y: second electrode layer, 01Y～08y: the second wiring layer, D: pressure sensing section.

  Next, an embodiment of the capacitive sensor of the present invention will be described.

<First embodiment>
Next, an embodiment of the capacitive sensor of the present invention will be described. In the following drawings, the vertical direction corresponds to the thickness direction of the dielectric layer of the present invention.

[Configuration of capacitive sensor]
First, the configuration of the capacitive sensor of this embodiment will be described. FIG. 2 shows a transparent top view of the capacitive sensor of the present embodiment. FIG. 3 is a perspective exploded view of the capacitance type sensor. FIG. 4 shows a vertical sectional view of one protrusion of the dielectric layer constituting the capacitance type sensor. For convenience of explanation, the protrusions are exaggerated in FIG.

  As shown in FIGS. 2 and 3, the capacitive sensor 1 includes a dielectric layer 20, a first electrode unit 30, a second electrode unit 40, and a connector 10.

  The dielectric layer 20 is made of solid silicone rubber. The dielectric layer 20 has a flat plate portion 21 and a large number of protrusions 22. The flat plate portion 21 has a square sheet shape. As shown in FIG. 4, the thickness L1 of the flat plate portion 21 is 1 mm. A large number of protrusions 22 protrude from the upper surface of the flat plate portion 21. The large number of protrusions 22 are arranged substantially uniformly over the entire top surface of the flat plate portion 21. The multiple protrusions 22 all have the same shape and size. That is, the protrusion 22 has a truncated cone shape that extends toward the flat plate portion 21. As shown in FIG. 4, the diameter L2 of the upper base of the protrusion 22 is 1.8 mm, the diameter L3 of the lower base is 2.2 mm, and the height L4 is 0.7 mm.

  The first electrode unit 30 is disposed on the upper side of the dielectric layer 20. The first electrode unit 30 includes a first base material 31, eight first electrode layers 01X to 08X, and eight first wiring layers 01x to 08x.

  The first base material 31 is made of thermoplastic polyurethane (TPU) and has a rectangular sheet shape. The thickness of the first base material 31 is 0.2 mm. On the lower surface of the first base material 31, eight first electrode layers 01X to 08X and eight first wiring layers 01x to 08x are arranged. A first protective layer (not shown) is disposed on the lower surface side of the first base material 31 so as to cover the first electrode layers 01X to 08X and the first wiring layers 01x to 08x from below. The first protective layer is made of silicone rubber and has a rectangular sheet shape substantially the same as the size of the first base material 31. The thickness of the first protective layer is 0.03 mm.

  The eight first electrode layers 01X to 08X each contain acrylic rubber and conductive carbon black. The first electrode layers 01X to 08X each have a strip shape with a width of 20 mm. The first electrode layers 01X to 08X each extend in the left-right direction. The first electrode layers 01X to 08X are arranged in parallel to each other with a spacing of 2 mm in the front-rear direction.

  The eight first wiring layers 01x to 08x each contain acrylic rubber and silver powder. The eight first wiring layers 01x to 08x each have a linear shape, and the eight first electrode layers 01X to 08X and the connector 10 are electrically connected. The connector 10 is electrically connected to a control device (not shown).

  The second electrode unit 40 is disposed below the dielectric layer 20. The configuration of the second electrode unit 40 is the same as the configuration of the first electrode unit 30. That is, the second electrode unit 40 has a second base material 41, eight second electrode layers 01Y to 08Y, and eight second wiring layers 01y to 08y.

  The second base material 41 is made of TPU and has a rectangular sheet shape. The thickness of the second base material 41 is 0.2 mm. On the upper surface of the second base material 41, eight second electrode layers 01Y to 08Y and eight second wiring layers 01y to 08y are arranged. A second protective layer (not shown) is disposed on the upper surface side of the second base material 41 so as to cover the second electrode layers 01Y to 08Y and the second wiring layers 01y to 08y from above. The second protective layer is made of silicone rubber and has a rectangular sheet shape substantially the same as the size of the second base material 41. The thickness of the second protective layer is 0.03 mm.

  The eight second electrode layers 01Y to 08Y each contain acrylic rubber and conductive carbon black. The second electrode layers 01Y to 08Y each have a strip shape with a width of 20 mm. The second electrode layers 01Y to 08Y each extend in the front-rear direction. The second electrode layers 01Y to 08Y are arranged in parallel to each other with a spacing of 2 mm in the left-right direction.

  The eight second wiring layers 01y to 08y each contain acrylic rubber and silver powder. The eight second wiring layers 01y to 08y each have a linear shape, and electrically connect the eight second electrode layers 01Y to 08Y and the connector 10.

The peripheral portions of the first base material 31 and the second base material 41 are spot-fused at a predetermined interval. That is, the first base material 31 and the second base material 41 are bonded together in a bag shape. When viewed from above, the first electrode layers 01X to 08X and the second electrode layers 01Y to 08Y are arranged in a lattice pattern. A plurality of pressure-sensitive portions D are set in a portion where the first electrode layers 01X to 08X and the second electrode layers 01Y to 08Y overlap. A total of 64 pressure sensitive parts D are set. The electrode area per pressure sensitive part D is 400 mm ² .

[Capacitive sensor movement]
Next, the movement of the capacitive sensor 1 of this embodiment will be described. First, before a load is applied to the capacitance type sensor 1 (initial state), a voltage is applied to the first electrode layers 01X to 08X and the second electrode layers 01Y to 08Y, and the capacitance is detected for each pressure-sensitive portion D. C is calculated. Subsequently, after the load is applied to the capacitive sensor 1, the electrostatic capacity C is calculated for each pressure-sensitive part D in the same manner. In the pressure-sensitive part D where the load is applied, the distance between the first electrode layer and the second electrode layer is reduced. As a result, the capacitance C of the pressure-sensitive part D increases. Based on the change amount ΔC of the capacitance C, the surface pressure for each pressure sensitive part D is calculated. In this way, the load distribution can be measured.

Although details will be described in the following examples, the sensitivity of the capacitive sensor 1 is 3.5 × 10 ⁻¹⁰ F / MPa in a pressure range of greater than 0 MPa and less than or equal to 0.015 MPa. Moreover, about the value of the some distortion in the said pressure range, among the coincidence calculated by said Formula (III), the maximum value is 1.3 and the minimum value is 0.6. Therefore, the dielectric layer 20 satisfies the pressure-strain curve represented by the above formula (I) in the pressure range of greater than 0 MPa and less than or equal to 0.015 MPa.

[Effects of capacitive sensor]
Next, the function and effect of the capacitive sensor 1 of the present embodiment will be described. In a pressure range of greater than 0 MPa and less than or equal to 0.015 MPa, the capacitive sensor 1 of the present embodiment has a predetermined sensitivity, and the dielectric layer 20 satisfies the pressure-strain curve represented by the above formula (I). Yes. For this reason, the capacitance type sensor 1 exhibits a behavior in which the capacitance changes linearly with respect to the pressure even in a region where the pressure is small. Therefore, according to the capacitive sensor 1, a small load can be accurately detected.

  The dielectric layer 20 is made of a solid body having a relatively large spring constant. For this reason, it is hard to sag even if a repeated load is applied. In addition, the dielectric layer 20 includes a flat plate portion 21 and a plurality of protruding portions 22 that protrude from the surface of the flat plate portion. When pressure is applied, the protrusion 22 is compressed first, and then the flat plate 21 is compressed. For this reason, in the case of a heavy load, the area receiving the pressure increases, and the pressure is distributed by that amount. As a result, the load on the dielectric layer 20 is reduced, and sag is suppressed. The protruding portion 22 has a truncated cone shape that extends toward the flat plate portion 21. For this reason, the protrusion part 22 is torn from the flat plate part 21, is not easily detached, and is not easily buckled. Therefore, the dielectric layer 20 is excellent in durability. Further, as the pressure increases, the protrusion 22 is crushed and the air layer in the pressure sensitive part D is reduced. As a result, the relative permittivity increases, and the capacitance increases. Therefore, according to the capacitive sensor 1, a large load can be detected with high sensitivity.

<Second embodiment>
The capacitive sensor of the present embodiment is different from the capacitive sensor of the first embodiment only in the configuration of the dielectric layer. Therefore, the difference will be mainly described here. FIG. 5 shows a perspective exploded view of a dielectric layer constituting the capacitance type sensor of the present embodiment. FIG. 6 is a vertical sectional view of a part of the second dielectric layer constituting the dielectric layer. For convenience of explanation, in FIG. 5, the band-shaped column portion is exaggerated.

  As shown in FIG. 5, the dielectric layer 50 includes a first dielectric layer 51 and a second dielectric layer 52. The first dielectric layer 51 and the second dielectric layer 52 are stacked in the vertical direction. The lower second dielectric layer 52 is made of solid silicone rubber. The second dielectric layer 52 has a flat plate portion 520 and a number of strip-like column portions 521. The flat plate portion 520 has a square sheet shape. As shown in FIG. 6, the thickness L1 of the flat plate portion 520 is 0.3 mm. A large number of strip-like column parts 521 are arranged on the upper surface of the flat plate part 520. A large number of strip-like column portions 521 each have a square columnar shape and extend in the left-right direction. A large number of strip-like column portions 521 are arranged in parallel with each other at a predetermined interval in the front-rear direction. The size of the strip-shaped column part 521 is the same. That is, as shown in FIG. 6, the height L2 of the strip-shaped column portion 521 is 1 mm, the width L3 is 1 mm, and the interval L4 between the adjacent strip-shaped column portions 521 is 6 mm.

  The configuration of the upper first dielectric layer 51 is the same as the configuration of the second dielectric layer 52. That is, the first dielectric layer 51 is made of solid silicone rubber, and has a flat plate portion 510 and a number of strip-like column portions 511.

  The first dielectric layer 51 is arranged in a state where it is rotated by 90 ° in the plane direction (front / rear / left / right direction) with respect to the second dielectric layer 52. Therefore, when the dielectric layer 50 is viewed from the upper side or the lower side, a large number of strip-shaped column portions 511 of the first dielectric layer 51 and a large number of the strip-shaped column portions 521 of the second dielectric layer 52 are arranged in a grid pattern. ing.

Although details will be described in the following examples, the sensitivity of the capacitive sensor of the present embodiment is 2.4 × 10 ⁻¹⁰ F / MPa in a pressure range of greater than 0 MPa and less than or equal to 0.015 MPa. Moreover, about the value of the some distortion in the said pressure range, among the coincidence calculated by said Formula (III), the maximum value is 1.5 and the minimum value is 0.8. Therefore, the dielectric layer 50 satisfies the pressure-strain curve represented by the above formula (I) in the pressure range of greater than 0 MPa and less than or equal to 0.015 MPa.

  Thus, in the pressure range of greater than 0 MPa and less than or equal to 0.015 MPa, the capacitive sensor of the present embodiment has a predetermined sensitivity, and the dielectric layer 50 has a pressure-strain curve represented by the above formula (I). Is pleased. For this reason, according to the capacitive sensor of this embodiment, a small load can be detected accurately. The first dielectric layer 51 and the second dielectric layer 52 constituting the dielectric layer 50 are both made of a solid body having a relatively large spring constant. For this reason, the dielectric layer 50 is difficult to sag even when a repeated load is applied.

  The dielectric layer 50 includes a first dielectric layer 51 and a second dielectric layer 52 that are stacked in the thickness direction. The first dielectric layer 51 and the second dielectric layer 52 are both flat plate portions 510 and 520, A plurality of strip-shaped column portions 511 and 521 arranged in parallel and spaced apart from each other on the surface of the flat plate portions 510 and 520, and when viewed through the dielectric layer 50 in the thickness direction, the first dielectric The layer 51 and the second dielectric layer 52 are arranged such that the plurality of strip-shaped column portions 511 of the first dielectric layer 51 and the plurality of strip-shaped column portions 521 of the second dielectric layer 52 are in a cross-beam shape. The dielectric layer 50 of the present embodiment is compressed not in a line but in a dot shape. For this reason, even if the width | variety of the strip | belt-shaped column parts 511 and 521 is comparatively large, it compresses with a small load. Therefore, it is possible to improve the durability of the strip-shaped column portions 511 and 521 and, consequently, the dielectric layer 50 while maintaining a desired sensitivity. In addition, the dielectric layer 50 has high durability against shearing force applied during use. Furthermore, the dielectric layer 50 can be manufactured relatively easily by pressing, injection molding, or the like.

<Third embodiment>
The capacitive sensor of the present embodiment is different from the capacitive sensor of the first embodiment only in the configuration of the dielectric layer. Therefore, the difference will be mainly described here. FIG. 7 is a perspective view of a dielectric layer constituting the capacitance type sensor of this embodiment. FIG. 8 shows a vertical cross-sectional view of one protrusion on the dielectric layer. For convenience of explanation, the waveform portion is exaggerated in FIG.

  As shown in FIG. 7, the dielectric layer 60 is made of urethane foam. The dielectric layer 60 has a flat plate portion 61 and a corrugated portion 62. The flat plate portion 61 has a square sheet shape. As shown in FIG. 8, the thickness L1 of the flat plate portion 61 is 1.1 mm. The corrugated portion 62 is disposed on the upper surface of the flat plate portion 61. The corrugated portion 62 is formed from a large number of protrusions 620. Each of the many protrusions 620 has a mountain-shaped cross section, and extends in the front-rear direction. The multiple protrusions 620 are arranged in parallel to each other in the left-right direction. The tops of the ridges 620 have a curved surface shape, and the adjacent ridges 620 are continuous with each other on a curved surface. The sizes of the protrusions 620 are all the same. That is, as shown in FIG. 8, the height L2 of the protrusion 620 is 1.65 mm, and the width L3 is 7 mm.

Although details will be described in the following examples, the sensitivity of the capacitive sensor of the present embodiment is 5.3 × 10 ⁻¹⁰ F / MPa in the pressure range of greater than 0 MPa and less than or equal to 0.015 MPa. Moreover, about the value of the some distortion in the said pressure range, among the coincidence calculated by said Formula (III), the maximum value is 1.9 and the minimum value is 0.6. Therefore, the dielectric layer 60 satisfies the pressure-strain curve represented by the above formula (I) in the pressure range of greater than 0 MPa and less than or equal to 0.015 MPa.

  Thus, in the pressure range of greater than 0 MPa and less than or equal to 0.015 MPa, the capacitive sensor of the present embodiment has a predetermined sensitivity, and the dielectric layer 60 has a pressure-strain curve represented by the above formula (I). Is pleased. For this reason, according to the capacitive sensor of this embodiment, a small load can be detected accurately. The dielectric layer 60 is made of a foam having a relatively small spring constant. For this reason, the capacitive sensor of the present embodiment is easier to detect a small load.

  The dielectric layer 60 includes a flat plate portion 61 and a corrugated portion 62 including a plurality of protrusions 620 arranged in parallel to each other on the surface of the flat plate portion 61. The tops of the protrusions 620 have a curved surface shape, and the adjacent protrusions 620 are continuous with each other on a curved surface. Thereby, both sensitivity and durability can be achieved.

<Fourth embodiment>
The main difference between the capacitive sensor of the present embodiment and the capacitive sensor of the first embodiment is the configuration and manufacturing method of the dielectric layer. Therefore, the difference will be mainly described here. FIG. 22 is an exploded perspective view of the capacitive sensor of this embodiment. FIG. 23 is a schematic cross-sectional view in the XXIII-XXIII direction in FIG. FIG. 24 shows a vertical sectional view of a part of the second dielectric layer. For convenience of explanation, in FIG. 22, the thin line portion of the dielectric layer is indicated by a dotted line. FIG. 23 shows a cross section of the stacked state of the first composite unit and the second composite unit.

  As shown in FIGS. 22 and 23, the capacitive sensor 1 includes a first composite unit 32, a second composite unit 42, and a connector 10. The first composite unit 32 and the second composite unit 42 are stacked in the vertical direction.

  The first composite unit 32 includes a first electrode unit 33 and a first dielectric layer 34. The first dielectric layer 34 is stacked below the first electrode unit 33. The first electrode unit 33 includes a first base material 31, eight first electrode layers 01X to 08X, and eight first wiring layers 01x to 08x. Since these configurations are the same as those in the first embodiment, description thereof is omitted. However, in the present embodiment, the width of the first electrode layers 01X to 08X is 14 mm, and the interval between adjacent electrode layers is 14 mm.

  The first dielectric layer 34 has a flat plate portion 35 and a large number of thin wire portions 36. The flat plate portion 35 is made of silicone rubber and has a rectangular sheet shape substantially the same as the size of the first base material 31. The flat plate portion 35 is laminated on the lower side of the first base material 31 so as to cover the first electrode layers 01X to 08X and the first wiring layers 01x to 08x from the lower side. The thickness of the flat plate part 35 is 0.03 mm. The flat plate portion 35 corresponds to the first protective layer of the first embodiment. The many thin wire portions 36 are made of silicone rubber and are disposed on the lower surface of the flat plate portion 35. Each of the many thin wire portions 36 has a linear shape and extends in the front-rear direction. The large number of thin line portions 36 are arranged in parallel to each other at a predetermined interval in the left-right direction. The large number of thin line portions 36 are arranged so as to be orthogonal to the first electrode layers 01X to 08X. The multiple thin wire portions 36 all have the same shape and size. That is, the thin wire portion 36 has a trapezoidal cross section, the height L2 of the thin wire portion 36 is 0.09 mm, the width L3 is 0.4 mm, and the interval L4 between adjacent thin wire portions 36 is 2.4 mm ( (See FIG. 24).

  The first electrode unit 33 and the first dielectric layer 34 are integrally manufactured by a printing method. That is, the first composite unit 32 screen-prints the first electrode layers 01X to 08X, the first wiring layers 01x to 08x, the flat plate portion 35, and the numerous fine wire portions 36 in this order on the lower surface of the first base material 31. Manufactured.

  The configuration of the second composite unit 42 is the same as the configuration of the first composite unit 32. That is, the second composite unit 42 includes a second electrode unit 43 and a second dielectric layer 44. The second dielectric layer 44 is laminated on the upper side of the second electrode unit 43. The second electrode unit 43 includes a second base material 41, eight second electrode layers 01Y to 08Y, and eight second wiring layers 01y to 08y. Since these configurations are the same as those in the first embodiment, description thereof is omitted. However, in this embodiment, the width of the second electrode layers 01Y to 08Y is 14 mm, and the interval between adjacent electrode layers is 14 mm.

  The configuration of the second dielectric layer 44 is the same as the configuration of the first dielectric layer 34. That is, the second dielectric layer 44 has a flat plate portion 45 and a large number of thin wire portions 46. The flat plate portion 45 is laminated on the upper side of the second base material 41 so as to cover the second electrode layers 01Y to 08Y and the second wiring layers 01y to 08y from the upper side. As shown in FIG. 24, the thickness L1 of the flat plate portion 45 is 0.03 mm. The flat plate portion 45 corresponds to the second protective layer of the first embodiment. A large number of thin wire portions 46 are arranged on the upper surface of the flat plate portion 45. Each of the many thin wire portions 46 has a linear shape and extends in the left-right direction. The large number of thin line portions 46 are arranged in parallel with each other at a predetermined interval in the front-rear direction. The large number of thin line portions 46 are arranged so as to be orthogonal to the second electrode layers 01Y to 08Y. The multiple thin wire portions 46 all have the same shape and size. That is, as shown in FIG. 24, the thin wire portion 46 has a trapezoidal cross section, the height L2 of the thin wire portion 46 is 0.09 mm, the width L3 is 0.4 mm, and the interval L4 between the adjacent thin wire portions 46. Is 2.4 mm.

  The second electrode unit 43 and the second dielectric layer 44 are integrally manufactured by a printing method. That is, the second composite unit 42 screen-prints the second electrode layers 01Y to 08Y, the second wiring layers 01y to 08y, the flat plate portion 45, and the many thin wire portions 46 in this order on the upper surface of the second base material 41. Manufactured.

  The dielectric layer of the capacitive sensor 1 is a laminate of the first dielectric layer 34 and the second dielectric layer 44. When the capacitive sensor 1 is viewed from the upper side or the lower side, the thin line portion 36 of the first dielectric layer 34 and the thin line portion 36 of the second dielectric layer 44 are arranged in a cross-beam shape, and intersecting portions In contact.

The peripheral portions of the first base material 31 and the second base material 41 are spot-fused at a predetermined interval. That is, the first base material 31 and the second base material 41 are bonded together in a bag shape. The electrode area per pressure-sensitive part D where the first electrode layers 01X to 08X and the second electrode layers 01Y to 08Y overlap is 196 mm ² (see FIG. 2 above).

Although details will be described in the following examples, the sensitivity of the capacitive sensor 1 is 7.5 × 10 ⁻¹⁰ F / MPa in a pressure range of greater than 0 MPa and less than or equal to 0.015 MPa. Moreover, about the value of the some distortion in the said pressure range, among the coincidence calculated by said Formula (III), the maximum value is 1.7 and the minimum value is 0.9. Therefore, the dielectric layers 34 and 44 satisfy the pressure-strain curve represented by the above formula (I) in the pressure range of greater than 0 MPa and less than or equal to 0.015 MPa.

  Thus, in the pressure range of greater than 0 MPa and less than or equal to 0.015 MPa, the capacitive sensor 1 has a predetermined sensitivity, and the dielectric layers 34 and 44 satisfy the pressure-strain curve represented by the above formula (I). doing. For this reason, according to the capacitive sensor 1, a small load can be accurately detected.

  The first dielectric layer 34 is manufactured integrally with the first electrode unit 33 by a screen printing method. The same applies to the second dielectric layer 44. Thereby, a dielectric layer can be made thin and lightweight. If the dielectric layer is thin, the sensitivity of the sensor can be increased while ensuring flexibility. Therefore, even a hard material having a relatively large spring constant can be used as a material for the dielectric layer, and the range of material selection is widened. When a hard material is used, the compression is suppressed and it is difficult to sag, so that durability is improved. Moreover, according to the printing method, a dielectric layer can be manufactured in the same series of steps such as an electrode layer and a wiring layer. Thereby, compared with the case where it manufactures separately from an electrode unit, manufacture becomes easy and it is suitable for mass production. In addition, the number of parts is reduced, and the process of fixing the dielectric layer and the electrode unit can be reduced.

  Both the flat plate portion 35 and the thin wire portion 36 of the first dielectric layer 34 are made of silicone rubber. The same applies to the second dielectric layer 44. Since the flat plate portion 35 and the thin wire portion 36 are made of the same material, the adhesiveness is high, and the thin wire portion 36 is difficult to peel off during use and is difficult to cut. Therefore, the first dielectric layer 34 and the second dielectric layer 44 are excellent in durability. The first dielectric layer 34 has a thin line portion 36, and the second dielectric layer 44 also has a thin line portion 46. Thereby, compared with the case where it forms only from a flat plate part, a softness | flexibility improves and it is easy to detect a small load.

<Fifth embodiment>
The capacitive sensor of this embodiment is different from the capacitive sensor of the fourth embodiment only in that a third dielectric layer is added as a dielectric layer. Therefore, the difference will be mainly described here. FIG. 25 is an exploded perspective view of the capacitive sensor of this embodiment. For convenience of explanation, in FIG. 25, the thin line portion of the dielectric layer is indicated by a dotted line.

  As shown in FIG. 25, the capacitive sensor 1 includes a first composite unit 32, a second composite unit 42, a third dielectric layer 23, and a connector 10. The third dielectric layer 23 is interposed between the first composite unit 32 and the second composite unit 42. The third dielectric layer 23 is made of TPU and has a rectangular sheet shape substantially the same as the size of the first base material 31 and the second base material 41. The thickness of the third dielectric layer 23 is 0.2 mm. The dielectric layer of the capacitive sensor 1 is a laminate of the first dielectric layer 34, the second dielectric layer 44, and the third dielectric layer 23. The third dielectric layer 23 is included in the concept of a flat plate portion.

Although details will be described in the following examples, the sensitivity of the capacitive sensor 1 is 3.8 × 10 ⁻¹⁰ F / MPa in a pressure range of greater than 0 MPa and less than or equal to 0.015 MPa. Moreover, about the value of the some distortion | strain in the said pressure range, the maximum value is 1.2 and the minimum value is 0.6 among the coincidence calculated by said Formula (III). Therefore, the dielectric layers 34, 23, and 44 satisfy the pressure-strain curve represented by the above formula (I) in the pressure range of greater than 0 MPa and less than or equal to 0.015 MPa.

  Thus, in the pressure range of greater than 0 MPa and less than or equal to 0.015 MPa, the capacitive sensor 1 has a predetermined sensitivity, and the dielectric layers 34, 23, and 44 are pressure-strain curves represented by the above formula (I). Is satisfied. For this reason, according to the capacitive sensor 1, a small load can be accurately detected.

  The third dielectric layer 23 is made of TPU that is harder than silicone rubber. By interposing the third dielectric layer 23, the shape-retaining property of the capacitive sensor 1 is improved, wrinkles are hardly generated, and the handling property is improved. The third dielectric layer 23 is made of TPU, whereas the thin wire portions 36 and 46 are made of silicone rubber. Since both are easy to slide, peeling of the thin wire portions 36 and 46 due to a shearing force at the time of contact hardly occurs. On the other hand, the third dielectric layer 23 is made of the same material as the first base material 31 of the first electrode unit 33 and the second base material 41 of the second electrode unit 43. For this reason, the circumference | surroundings of the 3rd dielectric layer 23, the 1st base material 31, and the 2nd base material 41 can be fixed by spot fusion, and can be fixed easily.

  For example, when the measurement object is small, it may enter the gap between the thin line portions 36, and the load may not be accurately detected. However, when the flat plate-like third dielectric layer 23 is interposed between the opposing thin wire portions 36 and 46 as in this embodiment, embedding of the measurement object between the thin wire portions is suppressed, and detection accuracy is increased. Can be improved. Further, the capacitance is reduced by the amount of the third dielectric layer 23 interposed. This can be used to adjust the capacitance.

  For example, when the electrode layer is long, the wiring layer may be extended in the longitudinal direction of the electrode layer in order to suppress an increase in electrical resistance. In this case, the thickness increases as the wiring layers are stacked. Therefore, if the wiring layer is not sufficiently covered by the flat plate portion 35, the opposing wiring layers may come into contact with each other and become conductive. However, when the flat third dielectric layer 23 is interposed between the opposing thin wire portions 36 and 46 as in this embodiment, conduction is suppressed even if the wiring layer is not sufficiently covered. can do.

<Sixth embodiment>
The main difference between the capacitive sensor of this embodiment and the capacitive sensor of the first embodiment is the configuration of the dielectric layer. Therefore, the difference will be mainly described here. FIG. 26 is a perspective exploded view of a dielectric layer in the capacitive sensor of this embodiment. FIG. 27 shows a vertical sectional view of a part of the second dielectric layer constituting the dielectric layer.

  As shown in FIG. 26, the dielectric layer 53 includes a first dielectric layer 54 and a second dielectric layer 55. The first dielectric layer 54 and the second dielectric layer 55 are stacked in the vertical direction. The first dielectric layer 54 has a flat plate portion 540 and a large number of thin wire portions 541. The flat plate portion 540 is made of TPU and has a rectangular sheet shape substantially the same as the size of the first base material 31 constituting the first electrode unit 30. The thickness of the flat plate portion 540 is 0.2 mm. The many thin wire portions 541 are made of silicone rubber and are disposed on the lower surface of the flat plate portion 540. Each of the many thin wire portions 541 has a linear shape and extends in the front-rear direction. The large number of thin line portions 541 are arranged in parallel to each other at a predetermined interval in the left-right direction. Many thin wire | line parts 541 are arrange | positioned so that it may orthogonally cross with the 1st electrode layers 01X-08X. The multiple thin wire portions 541 all have the same shape and size. That is, the thin wire portion 541 has a trapezoidal cross section, the height L2 of the thin wire portion 541 is 0.11 mm, the width L3 is 0.4 mm, and the interval L4 between adjacent thin wire portions 541 is 2.4 mm ( (See FIG. 27). A large number of thin line portions 541 are screen-printed on the lower surface of the flat plate portion 540.

  The configuration of the second dielectric layer 55 is the same as the configuration of the first dielectric layer 54. That is, the second dielectric layer 55 has a flat plate portion 550 and a large number of thin wire portions 551. As shown in FIG. 27, the thickness L1 of the flat plate portion 550 is 0.2 mm. Many thin wire | line parts 551 are arrange | positioned at the upper surface of the flat plate part 550. FIG. The large number of thin line portions 551 each have a linear shape and extend in the left-right direction. The large number of thin line portions 551 are arranged in parallel with each other at a predetermined interval in the front-rear direction. The large number of thin line portions 551 are arranged so as to be orthogonal to the second electrode layers 01Y to 08Y. All the thin line portions 551 have the same shape and size. That is, as shown in FIG. 27, the fine wire portion 551 has a trapezoidal cross section, the height L2 of the fine wire portion 551 is 0.11 mm, the width L3 is 0.4 mm, and the distance L4 between adjacent thin wire portions 551. Is 2.4 mm. A large number of thin line portions 551 are screen-printed on the upper surface of the flat plate portion 550. When the dielectric layer 53 is viewed from the upper side or the lower side, the fine line portion 541 of the first dielectric layer 54 and the fine line portion 551 of the second dielectric layer 55 are arranged in a cross-beam shape and contact at the intersecting portion. ing.

In the present embodiment, the width of the first electrode layers 01X to 08X is 14 mm, and the interval between adjacent electrode layers is 14 mm. The electrode area per pressure-sensitive part D where the first electrode layers 01X to 08X and the second electrode layers 01Y to 08Y overlap is 196 mm ² (see FIG. 2 above).

Although details will be described in the following examples, the sensitivity of the capacitive sensor of the present embodiment is 4.5 × 10 ⁻¹⁰ F / MPa in a pressure range greater than 0 MPa and less than or equal to 0.015 MPa. Moreover, about the value of the some distortion | strain in the said pressure range, the maximum value is 1.3 and the minimum value is 0.5 among the coincidence calculated by said Formula (III). Therefore, the dielectric layer 53 satisfies the pressure-strain curve represented by the above formula (I) in the pressure range of greater than 0 MPa and less than or equal to 0.015 MPa.

  Thus, in the pressure range of greater than 0 MPa and less than or equal to 0.015 MPa, the capacitive sensor of the present embodiment has a predetermined sensitivity, and the dielectric layer 53 has a pressure-strain curve represented by the above formula (I). Is pleased. For this reason, according to the capacitive sensor of this embodiment, a small load can be detected accurately.

  The first dielectric layer 54 is manufactured by screen printing a large number of thin line portions 541 on the lower surface of the flat plate portion 540. The same applies to the second dielectric layer 55. Unlike the fourth and fifth embodiments, the fine line portion is printed on a base material separate from the electrode unit. For this reason, there is no restriction due to the lower layer during printing, and the thickness of the dielectric layer and the selection range of the material are widened and the manufacturing is facilitated. In addition, the fine line portion can be printed uniformly with high dimensional accuracy without being affected by the unevenness of the lower layer.

<Other forms>
The embodiment of the capacitive sensor of the present invention has been described above. However, the embodiment is not limited to the above embodiment. Various modifications and improvements that can be made by those skilled in the art are also possible.

[Dielectric layer]
As the dielectric layer, an elastomer or a thermoplastic elastomer having a relatively high relative dielectric constant may be used. For example, a material having a relative dielectric constant of 2.5 or more (measurement frequency 25 kHz) is suitable. Examples of such elastomers include urethane rubber, silicone rubber, nitrile rubber, hydrogenated nitrile rubber, acrylic rubber, natural rubber, isoprene rubber, ethylene-propylene copolymer rubber, butyl rubber, styrene-butadiene rubber, fluorine rubber, epichlorohydrin rubber, Examples include chloroprene rubber, chlorinated polyethylene, and chlorosulfonated polyethylene. Examples of the thermoplastic elastomer include polyolefin, polyvinyl chloride, polyurethane, polyester, polyamide, fluorine, nitrile, and styrene. Among these, urethane rubber, silicone rubber, hydrin rubber, and acrylic rubber are preferable because both dielectric constant and flexibility are satisfied. When the dielectric layer is composed of a plurality of layers, the material of each layer may be the same or different.

  The elastomer or thermoplastic elastomer may be a solid body or a foamed body. The “foamed urethane” in the present specification is included in a foamed urethane rubber. For example, a foam is preferable from the viewpoint of excellent flexibility. Moreover, you may employ | adopt as an elastomer what has a crosslinked structure through ring-moving molecules, such as a polyrotaxane. The ring-moving molecule has a cyclic molecule and a linear molecule. Cyclic molecules can move along linear molecules. At least a portion of the polymer chain of the elastomer crosslinks with the cyclic molecule. As the cyclic molecule moves, the cross-linking point moves, so that stress is less likely to concentrate on the cross-linking point even if the expansion and contraction are repeated. Therefore, according to the elastomer having a cross-linked structure via a ring-moving molecule, a dielectric layer having both flexibility and sag resistance can be realized.

  The dimensions, such as the shape and thickness of the dielectric layer are such that the sensitivity of the capacitive sensor falls within a predetermined range according to the material and satisfies the pressure-strain curve represented by the above formula (I). It may be determined as appropriate. For example, considering the use of measuring human foot pressure distribution and body pressure distribution (from babies to adults), and sensor mounting, portability, ease of installation, etc., the thickness of the dielectric layer is It is desirable to be 0.1 mm or more. More preferable thickness is 0.2 mm or more, 0.4 mm or more, 0.5 mm or more. The thickness of the dielectric layer is preferably 5.0 mm or less, and more preferably 3.0 mm or less. Here, the thickness of the dielectric layer is the total thickness when a plurality of layers are stacked.

  In the fourth and fifth embodiments, the protective layer of the electrode unit in the other embodiments functions as a flat plate portion of the dielectric layer. In the capacitive sensor of the present invention, the elastomer layer disposed between the electrode layers is handled as follows. That is, in principle, an elastomer layer disposed between electrode layers is regarded as a dielectric layer. However, if there is a dielectric layer manufactured separately from the electrode unit and the thickness of the elastomer layer in one electrode unit is less than 1/10 of the thickness of the dielectric layer, the elastomer layer is dielectric. Not considered a layer. For example, in the sixth embodiment, a 0.03 mm protective layer (elastomer layer) is disposed on each of the pair of electrode units, but a 0.62 mm thick dielectric layer manufactured separately from the electrode units. 53, and the thickness of the protective layer in one electrode unit is smaller than 1/10 of the thickness of the dielectric layer 53, the protective layer is not regarded as a dielectric layer in any of the pair of electrode units.

  In the said 1st-3rd embodiment, the form which combined the projection part, the waveform part, or the strip | belt-shaped column part with the flat plate part was shown. However, only a flat plate portion, that is, a flat dielectric layer may be used. The dielectric layer preferably has at least a flat plate portion. Further, as shown in the above embodiment, the protrusions, corrugations, strip-shaped pillars, etc. may be disposed only on one surface in the thickness direction of the flat plate portion, but are disposed on both surfaces in the thickness direction of the flat plate portion. It may be.

  The dielectric layer may be manufactured separately from the electrode unit or may be manufactured integrally with the electrode unit. Examples of the former method include a pressing method, an injection molding method, a screen printing method, a metal mask printing method, and a cutting method. Examples of the latter method include screen printing, metal mask printing, ink jet printing, and liquid injection molding (dispensing).

  The raw material form of the elastomer and the thermoplastic elastomer is solid or liquid. In the case of a solid form, a press working method can be used, or a screen printing method or the like can be used by adding a solvent to form a liquid. On the other hand, when it is liquid, it is not necessary to add a solvent. Therefore, it can bridge | crosslink in a bridge | crosslinking process as it is, without passing through the drying process of a solvent, and a process can be simplified. Liquid elastomers include liquid silicone rubber, liquid ethylene-propylene rubber, liquid ethylene-propylene-diene rubber, liquid acrylic rubber, liquid isoprene rubber, liquid butadiene rubber, liquid chloroprene rubber, liquid styrene-butadiene rubber, liquid nitrile rubber, liquid Examples thereof include urethane rubber and liquid butyl rubber. Moreover, since a liquid elastomer can be crosslinked not only by heat but also by light such as ultraviolet rays, a crosslinked product can be obtained in a relatively short time.

  In the first embodiment, the frustoconical protrusions extending toward the flat plate portion are arranged. In this case, the upper base of the protrusion may be a curved surface instead of a flat surface. Further, the inclination of the cone may not be linear. For example, the inclination near the upper base or the lower base may be made gradually smaller than the inclination of other parts, and the vicinity of the upper base or the lower base may be formed into an R shape. By adopting the R shape, the durability of the protrusion is improved. Further, the shape of the protrusion is not limited to the truncated cone shape, and may be, for example, a truncated pyramid shape, a cone shape, or a pyramid shape. In the case of a truncated pyramid shape, the upper base may be a flat surface or a curved surface. As shown in the first embodiment, the plurality of protrusions may be arranged on the surface of the flat plate part at a predetermined interval, or arranged so that the protrusions are continuous with no gap therebetween. Also good. By arranging a plurality of protrusions continuously, the entire surface can be provided with unevenness like a so-called profile processed product.

  In the second embodiment, two dielectric layers (first dielectric layer and second dielectric layer) in which a plurality of strip-shaped column portions are arranged on the surface of the flat plate portion are stacked and used. However, any one of the first dielectric layer and the second dielectric layer may be used. Further, the shape of the belt-like column part is not limited to the rectangular column shape, and may be, for example, a columnar shape or a cylindrical shape.

  In the said 4th-6th embodiment, the dielectric layer in which many thin wire | line parts were formed in the flat plate part was used. The arrangement form, number, dimensions, etc. of the thin wire portions are not particularly limited. In the fourth to sixth embodiments, the thin wire portion is arranged so as to be orthogonal to the adjacent electrode layer via the flat plate portion, but may be arranged parallel to the adjacent electrode layer. In particular, as in the fourth and fifth embodiments, when the dielectric layer is printed over the electrode layer, if it is arranged parallel to the electrode layer, the influence of the unevenness of the lower layer is reduced during printing, and the fine line portion is accurately Can print well. For example, when the electrode layer is long, the wiring layer may be extended in the longitudinal direction of the electrode layer in order to suppress an increase in electrical resistance. In this case, since the electrode layer and the wiring layer are laminated, the unevenness increases. Further, the sensitivity of the sensor may change due to the difference in the thickness of the dielectric layer where the wiring layer and the thin line portion of the dielectric layer overlap. In such a case, it is preferable to arrange the thin line portion parallel to the electrode layer.

  The number and size of the thin wire portions may be appropriately determined so as to obtain a desired sensitivity according to the measurement object in consideration of the relationship with the electrode layer. In order to detect the load of a small object, the thin line portion should be formed as densely as possible. For example, in the fourth and fifth embodiments, the load of a smaller object can be detected by changing the width of the thin wire portion to 0.3 mm and the interval between adjacent thin wire portions to 1.1 mm.

  As in the fourth and fifth embodiments, the dielectric layer and the electrode unit can be manufactured integrally, and the protective layer of the electrode layer can function as a flat plate portion of the dielectric layer. In this case, if the thin wire portion is made of the same material as that of the protective layer (flat plate portion), the adhesion can be improved, and the durability of the dielectric layer and thus the sensor can be improved. On the other hand, when the dielectric layer and the electrode unit are manufactured separately as in the sixth embodiment, if the flat part of the dielectric layer is made of the same material as the base of the electrode unit, the flat part and the base are thermally fused. Can be easily fixed by wearing. In addition, the third dielectric layer added in the fifth embodiment is also easily fixed by thermal fusion with the base material by using the same material as the base material of the electrode unit.

  In the fifth embodiment, the third dielectric layer is interposed between the first composite unit having the first dielectric layer and the second composite unit having the second dielectric layer. However, a composite unit may be disposed on one side and an electrode unit may be disposed on the other side, and a flat dielectric layer may be interposed therebetween. Further, a dielectric layer may be further disposed between the first dielectric layer and the second dielectric layer of the sixth embodiment.

[First electrode unit, second electrode unit]
In the above embodiment, an electrode layer or the like is formed on the base material to form an electrode unit. However, an electrode unit or the like may be formed directly on the dielectric layer to form an electrode unit. That is, an electrode unit may be formed by forming an electrode layer, a wiring layer, a protective layer, and the like on both surfaces in the thickness direction of the dielectric layer. Moreover, in the said embodiment, although the protective layer was included in the electrode unit, a protective layer is not necessarily required. Moreover, the arrangement form of the electrode layer and the wiring layer in the electrode unit is not particularly limited. That is, when an electrode layer is arranged in an arbitrary size and shape, and the pair of electrode units are seen through in the stacking direction, the electrode layers overlap with each other across the dielectric layer, so that at least one pressure sensitive It is only necessary to set the part.

  Base materials include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyimide, polyethylene and other resin films, silicone rubber, butyl rubber, acrylonitrile-butadiene copolymer rubber, elastomer sheet such as ethylene-propylene copolymer rubber, polyurethane Sheets made of thermoplastic elastomers such as polyesters, polyesters, polyamides, polystyrenes, polyolefins, and polyvinyl chlorides, and stretchable fabrics made of such thermoplastic elastomers, PET, nylon, and the like are suitable.

  As a protective layer, in consideration of flexibility and tensile permanent strain, urethane rubber, acrylic rubber, silicone rubber, ethylene-propylene copolymer rubber, natural rubber, styrene-butadiene copolymer rubber, acrylonitrile-butadiene copolymer rubber, Nitrile rubber, hydrogenated nitrile rubber, epichlorohydrin rubber, chlorosulfonated polyethylene, chlorinated polyethylene and the like are suitable.

  The electrode layer is desirably flexible and stretchable from the viewpoint of easily following the deformation of the dielectric layer. For example, the electrode layer may be formed including an elastomer and a conductive material. The electrode layer may be a mode in which a conductive material layer and an elastomer layer are laminated in addition to a mode in which a conductive material is dispersed in an elastomer. In the latter embodiment, a part of the elastomer may be impregnated in the conductive material layer.

  Elastomers include urethane rubber, acrylic rubber, silicone rubber, ethylene-propylene copolymer rubber, natural rubber, styrene-butadiene copolymer rubber, acrylonitrile-butadiene copolymer rubber (nitrile rubber), epichlorohydrin rubber, and chlorosulfonated polyethylene. Chlorinated polyethylene is preferred. Examples of the conductive material include silver, gold, copper, nickel, rhodium, palladium, chromium, titanium, platinum, iron, metal particles made of these alloys, metal oxide particles made of zinc oxide, titanium oxide, etc., titanium carbonate A metal carbide particle composed of silver, gold, copper, platinum, nickel, etc., a conductive carbon material such as conductive carbon black, carbon nanotube, graphite, and graphene may be appropriately selected. . One of these can be used alone, or two or more can be mixed and used.

  The wiring layer is also preferably flexible and stretchable. For example, the wiring layer may be configured to include an elastomer and a conductive material. The wiring layer only needs to be electrically connected to the electrode layer. In addition to being connected to one end of the electrode layer, the wiring layer may be extended from the one end of the electrode layer to a predetermined length and stacked on the electrode layer. .

  As the elastomer, urethane rubber, acrylic rubber, silicone rubber, ethylene-propylene copolymer rubber, natural rubber, styrene-butadiene copolymer rubber, nitrile rubber, epichlorohydrin rubber, chlorosulfonated polyethylene, chlorine as well as the electrode layer Polyethylene etc. are suitable. As with the electrode layer, the conductive material may be appropriately selected from metal particles, metal oxide particles, metal carbide particles, metal nanowires, and conductive carbon materials. One of these can be used alone, or two or more can be mixed and used.

[Capacitive sensor]
In the capacitive sensor of the above embodiment, the sensitivity is 7.5 × 10 ⁻¹¹ F / MPa or more and 7.5 × 10 ⁻¹⁰ F / MPa or less in a pressure range of greater than 0 MPa and less than or equal to 0.015 MPa. The dielectric layer satisfies the formula (I). Therefore, when the load range of 0.015 MPa or less is included in the measurement pressure range, the effect of the present invention can be fully exhibited. Needless to say, the capacitive sensor of the present invention can be used to measure a pressure larger than the pressure range.

  As described above, whether or not the dielectric layer satisfies the formula (I) is determined by whether or not the degree of coincidence calculated by the formula (III) is 0.3 or more and 3.0 or less. The degree of coincidence is more preferably 0.5 or more and 2.0 or less. If the degree of coincidence is 0.5 or more and 2.0 or less, the sensitivity approaches constant within the measurement pressure range, so the calibration curve for converting the pressure from the capacitance easily matches the actual phenomenon, and the measurement accuracy is improved. More improved.

  The capacitive sensor may be used as it is in the above embodiment, but may be used by being housed in an exterior cover. When housed in the exterior cover, it is possible to reduce a sense of incongruity when the sensor comes into contact with a human body, and safety, antifouling properties, and design properties are improved. Suitable materials for the exterior cover include resins and elastomers such as vinyl chloride and TPU, elastic fabrics using elastic fibers such as polyurethane and polyester, and laminates of elastomers and elastic fabrics.

Hereinafter, the present invention will be described more specifically with reference to examples. First, 10 types of dielectric layers with different materials, shapes, dimensions, etc. were manufactured. Table 1 shows details of the 10 types of dielectric layers produced. Tables 2 and 3 show the values of the relative dielectric constant with respect to the strain in each dielectric layer.

[Example 1]
The dielectric layer of Example 1 is the same as the dielectric layer 20 in the first embodiment (see FIGS. 3 and 4). That is, the dielectric layer of Example 1 includes a flat plate portion and a large number of protrusions. The flat plate portion has a square sheet shape with a length of 120 mm, a width of 120 mm, and a thickness (L1) of 1 mm. The diameter (L2) of the upper base of the frustoconical protrusion is 1.8 mm, the diameter (L3) of the lower base is 2.2 mm, and the height (L4) is 0.7 mm.

[Example 2]
The dielectric layer of Example 2 is the same as the dielectric layer 50 in the second embodiment except for the thickness of the flat plate portion (see FIGS. 5 and 6). That is, the dielectric layer of Example 2 is composed of a first dielectric layer and a second dielectric layer laminated in the vertical direction. Each of the first dielectric layer and the second dielectric layer includes a flat plate portion and a number of strip-like column portions. The flat plate portion has a square sheet shape with a length of 120 mm, a width of 120 mm, and a thickness (L1) of 0.15 mm. The height (L2) of the many strip-shaped column portions is 1 mm, the width (L3) is 1 mm, and the interval (L4) between the adjacent strip-shaped column portions is 6 mm.

[Example 3]
The dielectric layer of Example 3 is the same as the dielectric layer 50 in the second embodiment (see FIGS. 5 and 6). That is, the dielectric layer of Example 3 is composed of a first dielectric layer and a second dielectric layer stacked in the vertical direction. Each of the first dielectric layer and the second dielectric layer includes a flat plate portion and a number of strip-like column portions. The flat plate portion has a square sheet shape with a length of 120 mm, a width of 120 mm, and a thickness (L1) of 0.3 mm. The height (L2) of the many strip-shaped column portions is 1 mm, the width (L3) is 1 mm, and the interval (L4) between the adjacent strip-shaped column portions is 6 mm.

[Example 4]
The dielectric layer of Example 4 is the same as that of the dielectric layer 60 in the third embodiment except for the thickness of the flat plate portion and the dimensions of the protrusions (see FIGS. 7 and 8 above). That is, the dielectric layer of Example 4 is composed of a flat plate portion and a corrugated portion. The flat plate portion has a square sheet shape with a length of 120 mm, a width of 120 mm, and a thickness (L1) of 1.7 mm. A large number of ridges forming the corrugated portion have a mountain-shaped cross section that is gentler than the ridge 620 in the third embodiment, and adjacent ridges are continuous with curved surfaces. The height (L2) of the ridge is 1.0 mm, and the width (L3) is 7 mm.

[Example 5]
The dielectric layer of Example 5 is the same as the dielectric layer 60 in the third embodiment (see FIGS. 7 and 8). That is, the dielectric layer of Example 5 includes a flat plate portion and a corrugated portion. The flat plate portion has a square sheet shape with a length of 120 mm, a width of 120 mm, and a thickness (L1) of 1.1 mm. The height (L2) of many ridges forming the corrugated portion is 1.65 mm, and the width (L3) is 7 mm.

[Example 6]
The dielectric layer of Example 6 is made of foamed hydrin rubber and has a flat plate shape. The size of the dielectric layer of Example 6 is 120 mm long, 120 mm wide, and 2.10 mm thick.

[Example 7]
The dielectric layer of Example 7 is the same as the dielectric layer in the fourth embodiment (see FIGS. 22 to 24). That is, the dielectric layer of Example 7 is a laminate of the first dielectric layer in the first composite unit and the second dielectric layer in the second composite unit. Each of the first dielectric layer and the second dielectric layer includes a flat plate portion and a large number of thin wire portions. The flat plate portion has a rectangular sheet shape with a length of 900 mm, a width of 700 mm, and a thickness (L1) of 0.03 mm. The height (L2) of many thin wire | line parts is 0.09 mm, width (L3) is 0.4 mm, and the space | interval (L4) between adjacent thin wire | line parts is 2.4 mm.

[Example 8]
The dielectric layer of Example 8 is the same as the dielectric layer in the fifth embodiment (see FIG. 25). That is, the dielectric layer of Example 8 is a laminate of the first dielectric layer in the first composite unit, the second dielectric layer in the second composite unit, and the third dielectric layer disposed therebetween. . Each of the first dielectric layer and the second dielectric layer includes a flat plate portion and a large number of thin wire portions. The flat plate portion has a rectangular sheet shape with a length of 900 mm, a width of 700 mm, and a thickness (L1) of 0.03 mm. The height (L2) of many thin wire | line parts is 0.09 mm, the width (L3) is 0.4 mm, and the space | interval (L4) between adjacent thin wire | line parts is 2.4 mm (refer above-mentioned FIG. 24). The third dielectric layer has a rectangular sheet shape with a length of 900 mm, a width of 700 mm, and a thickness of 0.2 mm.

[Example 9]
The dielectric layer of Example 9 is the same as the dielectric layer 53 in the sixth embodiment (see FIGS. 26 and 27). That is, the dielectric layer of Example 9 is composed of a first dielectric layer and a second dielectric layer laminated in the vertical direction. Each of the first dielectric layer and the second dielectric layer includes a flat plate portion and a large number of thin wire portions. The flat plate portion has a rectangular sheet shape with a length of 900 mm, a width of 700 mm, and a thickness (L1) of 0.2 mm. The height (L2) of many thin wire | line parts is 0.11 mm, width (L3) is 0.4 mm, and the space | interval (L4) between adjacent thin wire | line parts is 2.4 mm.

[Comparative Example 1]
The dielectric layer of Comparative Example 1 is made of urethane foam and has a flat plate shape. The size of the dielectric layer of Comparative Example 1 is 120 mm long, 120 mm wide, and 3.00 mm thick.

  In Table 1, the sensitivity a of the sensor was measured as follows. First, in Examples 1 to 6, 9 and Comparative Example 1, as in the above embodiment, the first electrode unit is disposed on the upper surface of each dielectric layer, and the second electrode unit is disposed on the lower surface. Was made. In Examples 7 and 8, the electrode unit is integrated with the first and second dielectric layers. Therefore, for Example 7, the first composite unit and the second composite unit are stacked, and for Example 8, the first composite unit, the third dielectric layer, and the second composite unit are stacked. Used as a capacitive sensor. Then, a plurality of square plate-shaped metal weights having a mass of 0.3 kg and an 86 mm square were prepared. A resin plate is disposed on one surface of the metal weight. The one surface overlaps four belt-like electrode layers having a width of 20 mm (4 × 4 = 16 pressure-sensitive portions). Next, the metal weight was placed on the capacitance type sensor with one surface on which the resin plate was placed facing down, and the capacitance of the pressure sensitive portions at the four central locations was measured. Subsequently, the capacitance at the four locations was measured while increasing the number of metal weights and changing the pressure. The average value of the measured capacitances at four locations was calculated, and the average value was defined as the capacitance with respect to the pressure. Then, the sensitivity a of the sensor was calculated from the amount of change in capacitance with respect to the amount of change in pressure.

The dielectric constant ε _{0 of the} vacuum necessary for calculating the constant term of the formula (I) was 8.85 × 10 ⁻¹² [F / m]. The relative dielectric constants shown in Table 2 are as follows. For Examples 1 to 6 and Comparative Example 1, the dielectric layer was placed in a sample holder (Solartron, type 12962A), and the dielectric constant measurement interface (made by the company, type 1296) And a frequency response analyzer (manufactured by the company, model 1255B). The relative dielectric constant was measured while changing the strain applied to the dielectric layer. The measurement frequency was 25 kHz and the measurement voltage was 1V.

  In Examples 7 to 9, since the thickness of the dielectric layer was small, the relative dielectric constant was measured as follows with the electrode unit integrated. FIG. 28 shows a schematic diagram of a relative dielectric constant measuring apparatus. As shown in FIG. 28, the sample 71 to be measured is arranged on a base 70 made of acrylic resin. The sample 71 is a laminated body (capacitive sensor) in which electrode units are integrated on both upper and lower sides of a dielectric layer, and includes one pressure-sensitive part. The upper and lower electrode layers of the sample 71 are each connected to a dielectric constant measuring device 75. As the dielectric constant measurement device 75, the above-described dielectric constant measurement interface and frequency response analyzer were used (measurement frequency 25 kHz, measurement voltage 1 V). On the upper surface of the sample 71, a first acrylic plate 72 for making the pressure load area to the sample 71 constant is disposed, and a second acrylic plate 73 is further disposed thereon. The 2nd acrylic board 73 was arrange | positioned in order to make the measurement of the displacement amount mentioned later, and the pressure addition conditions the same. Thereby, a pressure of 0.00027 MPa is applied to the sample 71. With this state (state in which the weight 74 is not placed) as the strain of the dielectric layer being zero, the weight 74 of various masses was placed on the second acrylic plate 73, and the relative dielectric constant was measured while increasing the pressure applied to the dielectric layer. . Strain-dielectric constant data was obtained by combining the obtained pressure-dielectric constant data with pressure-strain data obtained by a laser displacement meter described later.

For Example 9, the relative dielectric constant was measured in a state where the protective layer of the pair of electrode units was laminated on the dielectric layer. For this reason, the measured dielectric constant is different from the dielectric constant of only the dielectric layer. Therefore, the measured dielectric constant was corrected and used as the dielectric constant of the dielectric layer. As a correction formula, the following formula (i) was used. In Table 3 above, ε _r2 calculated by the following equation (i) is shown as the relative dielectric constant ε _rk ′ of the corrected dielectric layer. The correction formula was derived by the following method.

First, assuming that the laminated protective layer and dielectric layer are capacitors connected in series, the total capacitance C is calculated from the capacitance C ₁ of the protective layer and the capacitance C _{2 of the} dielectric layer as follows: (H).
1 / C = 1 / C ₁ + 1 / C ₂ + 1 / C ₁ (h)
Substituting the relational expression C = ε ₀ ε _r S / d for the plate capacitor into the equation (h) and rearranging, the following equation (i) is obtained.
ε _r2 = d ₂ / (d / ε _r -2 × d ₁ / ε _r1 ) (i)
Here, ε _r is the relative permittivity of the whole (measured permittivity), ε _r1 is the relative permittivity of the protective layer (3.2), ε _r2 is the relative permittivity of the dielectric layer, and d is the overall (protective layer) + Dielectric layer + protective layer), d ₁ is the thickness of the protective layer (0.03 mm: regarded as a constant value), and d ₂ is the thickness of the dielectric layer. As described above, d ₂ is represented by d ₂ = d ₀ × (1−k) where d ₀ is the initial thickness and k is the strain.

  About 10 types of dielectric layers, the displacement amount with respect to a load was measured and the pressure-strain curve was created. For Examples 1 to 6 and Comparative Example 1, a load cell was used. About Examples 7-9, the displacement amount was measured as follows in the state which integrated the electrode unit similarly to the measurement of a dielectric constant. FIG. 29 is a schematic diagram of a displacement measuring device. 29, the same members as those in FIG. 28 are denoted by the same reference numerals. As shown in FIG. 29, on the upper surface of the sample 71, a first acrylic plate 72 and a second acrylic plate 73 are arranged in order from the bottom. The second acrylic plate 73 is transparent, and a light receiving portion 76 that receives laser light (indicated by a dotted line in the drawing) emitted from the laser displacement meter 77 is disposed on the lower surface of the right end. Although not shown, the laser displacement meter 77 is composed of a sensor head (“LK-G10” manufactured by KEYENCE), a controller (“LK-G3000V” manufactured by the same company), and a power supply device (“MS2-H50” manufactured by the same company). Yes. In an initial state where the weight 74 is not placed, a pressure of 0.00027 MPa is applied to the sample 71. With this state as a strain 0 of the dielectric layer, weights 74 of various masses were placed on the second acrylic plate 73, and the displacement was measured while increasing the pressure applied to the dielectric layer. The sample 71 includes a TPU base material for forming the electrode layer in addition to the dielectric layer. However, it is assumed that there is no displacement of the base material, and the measured displacement amounts are all of the dielectric layer. The amount of displacement was used.

  FIG. 9 collectively shows the pressure-strain curves actually measured in the dielectric layers of Examples 1 to 6 and Comparative Example 1. In FIG. 30, the pressure-strain curve measured in the dielectric layer of Examples 7-9 and the comparative example 1 is shown collectively. As shown in FIGS. 9 and 30, the pressure-strain curve of the dielectric layer of the comparative example has two inflection points, whereas the pressure-strain curve of the dielectric layer of the example increases almost monotonously. ing.

  Next, pressure-strain curves (calculation lines) were created for the 10 types of dielectric layers according to the formula (I), and the measured pressure-strain curves shown in FIGS. 9 and 30 were compared. In FIG. 10, the calculation line and the measured value in the dielectric layer of Example 1 are shown together. In FIG. 11, the calculation line and the measured value in the dielectric layer of Example 2 are shown together. In FIG. 12, the calculation line and measured value in the dielectric layer of Example 3 are shown together. FIG. 13 shows the calculation lines and measured values in the dielectric layer of Example 4 together. In FIG. 14, the calculation line and measured value in the dielectric layer of Example 5 are shown together. In FIG. 15, the calculation line and the measured value in the dielectric layer of Example 6 are shown together. In FIG. 16, the calculation line and the measured value in the dielectric layer of Comparative Example 1 are shown together. In FIG. 31, the calculation line and measured value in the dielectric layer of Example 7 are shown together. In FIG. 32, the calculation line in the dielectric layer of Example 8 and the measured value are shown together. In FIG. 33, the calculation line and measured value in the dielectric layer of Example 9 are shown together.

  As shown in FIG. 10 to FIG. 15 and FIG. 31 to FIG. 33, according to the dielectric layer of the example, in the load region of 0.015 MPa or less, the actually measured pressure-strain curve is represented by the calculated formula (I). It can be seen that it approximates the pressure-strain curve.

  Further, in order to judge whether each dielectric layer satisfies the formula (I), the degree of coincidence was calculated by the formula (III). In FIG. 17, the graph which plotted the coincidence degree of the dielectric layer of Examples 1-6 and the comparative example 1 with respect to the actually measured pressure is shown. FIG. 34 shows a graph in which the degree of coincidence of the dielectric layers of Examples 7 to 9 is plotted against the actually measured pressure. As shown in FIGS. 17 and 34, the degree of coincidence of the dielectric layers of the examples is within the range of 0.3 or more and 3.0 or less, and further 0.5 or more and 2.0 in the pressure range of 0.015 MPa or less. Within the following range. On the other hand, the degree of coincidence of the dielectric layer of the comparative example greatly exceeded 3.0. Thereby, it was confirmed that the dielectric layer of an Example satisfy | fills the pressure-strain curve shown by Formula (I).

  Next, a capacitive sensor was manufactured using 10 types of dielectric layers, and the output of the sensor with respect to the load was measured. The configuration of the capacitive sensor is the same as that of the above-described embodiment corresponding to the dielectric layer. The produced capacitive sensors were numbered as Examples 1 to 9 and Comparative Example 1 in correspondence with the numbers of the dielectric layers used. In FIG. 18, the output of the capacitive sensor of Examples 1-3 is shown with a graph. In FIG. 19, the output of the capacitive sensor of Examples 4-6 is shown with a graph. FIG. 20 is a graph showing the output of the capacitive sensor of Comparative Example 1. In FIG. 35, the output of the capacitive sensor of Examples 7-9 is shown with a graph.

  As shown in FIG. 20, in the capacitance type sensor of the comparative example that does not satisfy the pressure-strain curve represented by the formula (I), the capacitance value up to about 0.002 MPa is small and the change is small. On the other hand, as shown in FIGS. 18, 19, and 35, in the capacitance type sensor of the example, the capacitance changes almost linearly with respect to the pressure, and is 0.002 MPa or less. It was confirmed that the small load can be measured with high accuracy.

Claims (9)

A dielectric layer made of an elastomer, and a pair of electrode units arranged with the dielectric layer sandwiched in the thickness direction and having an electrode layer on each of the dielectric layers, and pressure sensitive to a portion where the electrode layer faces through the dielectric layer A capacitive sensor in which a part is set,
In a pressure range greater than 0 MPa and less than or equal to 0.015 MPa, the sensitivity of the capacitive sensor is 7.5 × 10 ⁻¹¹ F / MPa to 7.5 × 10 ⁻¹⁰ F / MPa, and the dielectric layer is A capacitance type sensor satisfying a pressure-strain curve represented by the following formula (I):
_{P k = ε 0 × S /} (d 0 × a) × {ε rk / (1-k) -ε r0} ··· (I)
k: Strain when the dielectric layer is compressed in the thickness direction [-]
P _k : Pressure applied to the dielectric layer compressed with strain k [MPa]
S: Electrode area in pressure-sensitive part [m ² ]
d ₀ : thickness of dielectric layer before compression [m]
a: Sensitivity of capacitive sensor [F / MPa]
ε ₀ : dielectric constant of vacuum [F / m]
ε _r0 : relative dielectric constant [−] of the dielectric layer before compression
ε _rk : dielectric constant of the dielectric layer when compressed with strain k [−]   The capacitive sensor according to claim 1, wherein the dielectric layer is made of one kind selected from urethane rubber, silicone rubber, hydrin rubber, and acrylic rubber.   The capacitive sensor according to claim 1, wherein the dielectric layer is made of a foam.   4. The capacitive sensor according to claim 1, wherein the dielectric layer includes a flat plate portion and a protruding portion protruding from a surface of the flat plate portion.   The capacitive sensor according to claim 4, wherein the protruding portion has a truncated cone shape that extends toward the flat plate portion.   The capacitance type according to any one of claims 1 to 3, wherein the dielectric layer includes a flat plate portion and a corrugated portion including a plurality of protrusions arranged in parallel to each other on the surface of the flat plate portion. Sensor.   The capacitive sensor according to claim 6, wherein the tops of the protrusions have a curved shape, and the adjacent protrusions are continuous with each other on a curved surface. The dielectric layer comprises a first dielectric layer and a second dielectric layer laminated in the thickness direction,
Each of the first dielectric layer and the second dielectric layer has a flat plate portion and a plurality of strip-shaped column portions that are arranged in parallel and spaced from each other on the surface of the flat plate portion,
When viewed through the dielectric layer in the thickness direction, the first dielectric layer and the second dielectric layer include a plurality of the strip-shaped column portions of the first dielectric layer and a plurality of the second dielectric layers. The capacitive sensor according to any one of claims 1 to 3, wherein the belt-like column portion is arranged so as to have a cross beam shape. The electrode unit disposed on one side in the thickness direction of the dielectric layer is a first electrode unit, and the electrode unit disposed on the other side in the thickness direction of the dielectric layer is a second electrode unit.
In the first electrode unit, the electrode layer comprises a plurality of first electrode layers arranged in parallel with each other, and in the second electrode unit, the electrode layer comprises a plurality of second electrode layers arranged in parallel with each other,
A direction in which the plurality of first electrode layers and the plurality of second electrode layers intersect each other when the first electrode unit, the dielectric layer, and the second electrode unit are seen through in the stacking direction. The static pressure according to any one of claims 1 to 8, wherein a plurality of the pressure-sensitive portions are set at a portion that extends to the portion where the plurality of first electrode layers and the plurality of second electrode layers overlap. Capacitive sensor.

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