WO2022113197A1 - Compression sensor - Google Patents

Abstract

[Problem] To provide a compression sensor that can have both flexibility that exhibits compression deformation due to a slight force, and compression resistance when a large force has been repeatedly applied thereto. [Solution] A compression sensor that comprises a spacer and a pair of electrodes separated by the spacer with a gas layer therebetween, and measures compression force working on the sensor by measuring an electrostatic capacity between the electrodes, wherein the spacer material has an ultimate compressive stress of at least 1.0×10¹ MPa, a compression modulus of at most 5.0×10² MPa, and a compression limit of at least 20%.

Description

Compression sensor

The present invention relates to a compression sensor.

Since conventional strain gauges (metal wire type and piezoelectric type) lack flexibility, there is a risk of damage due to shear stress that causes displacement, and it has been difficult to apply them to the surface of robot hands.

In Patent Document 1, a pair of panel electrodes integrally molded inside the outer skin cover, an elastic frame spacer provided inside the peripheral edge of the outer skin cover, and an elastic frame spacer provided inside the frame spacer between the panel electrodes. A weight sensor with multiple elastic support spacers has been described, and it has been proposed to measure the force acting on the sensor by measuring the capacitance between a pair of panel electrodes separated by spacers. There is.

Japanese Unexamined Patent Publication No. 2017-120244

However, it was difficult for the spacer of Patent Document 1 to have both the flexibility to compress and deform with a slight force and the compression resistance when a large force is repeatedly applied. For this reason, it has been difficult to apply it to the hand part of an industrial robot or a construction machine that grips a heavy object, or to measure the load on the sole of a walking / traveling robot to which a high load is applied.

Therefore, an object of the present invention is to provide a compression sensor capable of achieving both flexibility of compression and deformation with a small force and compression resistance when a large force is repeatedly applied.

The present invention includes a spacer and a pair of electrodes separated by a gas layer, and the spacer material is a compression sensor that measures the compressive force acting on the sensor by measuring the electrostatic capacitance between the electrodes. The compression limit stress is 1.0 × 10 ¹ MPa or more, and the compressive elastic modulus is 5.0 × 10 ² MPa or less.

Here, the spacer material preferably has a compression limit ratio of 20% or more.

The spacer material preferably has a compression limit stress of 2.0 × 10 ¹ MPa or more.

The spacer material preferably has a compressive elastic modulus of 2.0 × 10 ² MPa or less.

The spacer material is preferably a material formed of crosslinked polyrotaxane.

It is preferable to have a dielectric elastomer layer in addition to the gas layer between the pair of electrodes. The dielectric elastomer layer is preferably formed of crosslinked polyrotaxane.

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Since the compressive elastic modulus is as low as 5.0 × 10 ² MPa or less, it can be easily compressed and deformed with a slight force, and this slight force can be measured.
Since the compression limit stress is as high as 1.0 × 10 ¹ MPa or more, large repetitive forces can be measured with good reproducibility.
When the compression limit ratio is 20% or more, the resolution of the sensor is high.
When a crosslinked polyrotaxane having a high dielectric constant is used for the dielectric elastomer layer, the capacitance greatly fluctuates even at the stage where the gas layer is compressed, and the resolution is improved.

According to the present invention, it is possible to provide a compression sensor capable of achieving both flexibility of compression and deformation with a small force and compression resistance when a large force is repeatedly applied.

FIG. 1 is a perspective view showing a crosslinked polyrotaxane molded product used in Examples and a compression test method thereof. FIG. 2 is a graph showing a load-displacement curve in a compression test of the crosslinked polyrotaxane molded product. FIG. 3 is a micrograph of the crosslinked polyrotaxane molded product after a predetermined load is applied and unloaded. FIG. 4A is a graph showing a load-displacement curve in a compression test of a polyurethane molded product as a comparative example, and FIG. 4B is a graph showing an enlarged curve of the IVb portion of FIG. 4A. FIG. 5 is a micrograph of the polyurethane molded product after a predetermined load is loaded and unloaded. FIG. 6A is a cross-sectional view of the compression sensor of the first embodiment, and FIG. 6B is a cross-sectional view of the compression sensor of the second embodiment. FIG. 7A is a perspective view using the compression sensor of the embodiment for the robot hand, and FIG. 7B is a perspective view of using the compression sensor of the embodiment for the shoe insole.

[1] Spacer The material of the spacer is not particularly limited as long as it has the above-mentioned compression characteristics, and various dielectric elastomers can be used.
The dielectric elastomer is not particularly limited, and examples thereof include silicone elastomer, styrene-based thermoplastic elastomer, natural rubber, nitrile rubber, acrylic rubber, urethane rubber, urea rubber, fluororubber, and crosslinked polyrotaxane. Of these, crosslinked polyrotaxane is particularly preferable because it is easy to obtain the above-mentioned compression characteristics.

In the above, polyrotaxane is a molecular assembly having a structure in which a linear molecule penetrates a cyclic molecule so as to be relatively slidable, and the cyclic molecule is not detached by the blocking groups arranged at both ends of the linear molecule (for example). International Publication No. 2005/080469), also known as a slide ring material. The polyrotaxane is not limited to those having a specific cyclic molecule, a linear molecule, and a blocking group.
Examples of the cyclic molecule include cyclodextrin, crown ether, cyclophane, calixarene, cucurbituril, cyclic amide and the like.
Examples of the linear molecule include polyethers such as polyethylene glycol, polypropylene glycol and polytetrachloride, polyesters such as polylactic acid, polyamides such as 6-nylon, diene polymers such as polyisoprene and polybutadiene, polyethylene and polypropylene. , Polyvinyl alcohol, polyvinyl methyl ether, vinyl polymers such as polyisobutylene, polydimethylsiloxane, and the like can be exemplified.
The blocking groups include dinitrophenyl groups, cyclodextrins, adamantan groups, trityl groups, fluoresceins, pyrenes, and substituted benzenes (alkyl, alkyloxy, hydroxy, halogen, cyano, sulfonyl, carboxyl as substituents). , Amino, phenyl and the like can be exemplified), polynuclear aromatics which may be substituted (the same as above can be exemplified as the substituent), steroids and the like can be exemplified.
Currently, the most common polyrotaxane uses cyclodextrin as a cyclic molecule and polyethylene glycol as a linear molecule.

The crosslinked polyrotaxane is one in which the cyclic molecules of adjacent polyrotaxanes are crosslinked with a crosslinking agent. The cross-linking agent is not limited to a specific one.
Examples of the cross-linking agent include cyanul chloride, trimeoyl chloride, terephthaloyl chloride, epichlorohydrin, dibromobenzene, glutaaldehyde, aliphatic polyfunctional isocyanate, aromatic polyfunctional isocyanate, trilein diisosocyanate, hexamethylene diisocyanate, and divinyl. Block copolymers containing sulfones, 1,1'-carbonyldiimidazoles, alkoxysilanes and their derivatives, and polysiloxanes (polycaprolactone-polysiloxane block copolymers, polyadipates-polysiloxane block copolymers, Polyethylene glycol-polysiloxane block copolymer, etc.) can be exemplified.

[2] Dielectric Elastomer Layer The material of the dielectric elastomer layer is not particularly limited, and various dielectric elastomers can be used.
The dielectric elastomer is not particularly limited, but the one exemplified in the above [1] can also be exemplified. Of these, crosslinked polyrotaxane is particularly preferable because it has a high dielectric constant.

[3] Electrode The material of the electrode is not particularly limited, but can be deformed according to compression deformation, such as a conductive film made of conductive particles, a conductive coating film containing conductive particles, and conductivity including conductive particles. Examples thereof include a sex elastomer molded product.
Here, the conductive particles are not particularly limited, and examples thereof include particles such as carbon black, carbon nanotubes, platinum, gold, silver, copper, and nickel.
The resin component of the conductive coating film is not particularly limited, and examples thereof include phthalic acid-based, acrylic-based, urethane-based, epoxy-based, and vinyl-based resins.
The elastomer component of the conductive elastomer molded product is not particularly limited, but the dielectric elastomer exemplified in the above [1] can be exemplified.

[3] Gas layer The gas in the gas layer is not particularly limited, and examples thereof include air and a low dielectric constant gas having a dielectric constant lower than that of air. Examples of the low dielectric constant gas include nitrogen and carbon dioxide gas.

Hereinafter, examples of the compression sensor embodying the present invention will be described in the following order. The present invention is not limited to the present embodiment.
<1> Fabrication of crosslinked polyrotaxane molded article used in Examples <2> Polyurethane molded article as a comparative example <3> Measurement of compression characteristics of crosslinked polyrotaxane molded article and polyurethane molded article <4> Fabrication of compression sensor of Example 1 <5> Fabrication of compression sensor of Example 2 <6> Operation and effect of compression sensor of Example <7> Usage of compression sensor of Example

<1> Preparation of Crosslinked Polyrotaxane Molded Product Used in Examples A polyrotaxane composition similar to Example 2 of JP-A-2017-66318, which was previously proposed by the present applicant, was prepared.
That is, first, the polyrotaxane A disclosed in the same publication, the block copolymer B containing polysiloxane, and the polymer C not containing polysiloxane were prepared.
Specifically, polyrotaxane A contains cyclodextrin as a cyclic molecule, polyethylene glycol as a linear molecule, and blocking groups are arranged at both ends of the linear molecule. The polyrotaxane A of this example has a caprolactone group in order to further obtain solubility and compatibility.
The block copolymer B containing polysiloxane has improved moisture resistance by polysiloxane (silicone component), and specifically, a block of polycaprolactone-polydimethylsiloxane-polycaprolactone having a terminal block isocyanate group. It is a copolymer. The addition of the copolymer B is optional.
Polymer C, which does not contain polysiloxane, has high compatibility with polyrotaxane, and by including this, high dielectric constant and low elasticity are realized. Specifically, polypropylene glycol having a terminal block isocyanate group is used. be. The addition of the polymer C is optional.
These and other components were added in the following formulation (formulation value is parts by mass), stirred, and defoamed well to prepare a polyrotaxane composition solution.
Polyrotaxane A 10
Polysiloxane block copolymer B 10.6
Polymer C 9
Polypropylene glycol diol 4.7
Methyl cellosolve 25.3
Dibutyltin dilauryl acid 0.015
DBL-C31 (manufactured by GELEST) 0.15
IRGANOX1726 (manufactured by BASF) 0.45

The above polyrotaxane composition solution was applied onto a polyethylene terephthalate (PET) plate by a slit die coater method to form a polyrotaxane molded product (film) having a thickness of 50 μm. Subsequently, the polyrotaxane molded product with a PET plate was crosslinked and cured in an oven at 130 ° C. under reduced pressure for 5 hours, and the cured crosslinked polyrotaxane molded product (dielectric elastomer molded product) was peeled off from the PET plate.

<2> Polyurethane molded product as a comparative example As the polyurethane molded product as a comparative example, a polyurethane film (trade name “Touch Grace Film”, thickness 25 μm) manufactured by Takeda Sangyo Co., Ltd. was used.

<3> Measurement of Compression Characteristics of Crosslinked Polyrotaxane Molded Body and Polyurethane Molded Body The crosslinked polyrotaxane molded body and the polyurethane molded body were cut into test pieces having dimensions of 10 mm × 10 mm, respectively.
As shown in FIG. 1, a test piece was placed on the table of a compression tester, and an indenter was pressed against the test piece to displace it, and a compression test was performed. The tip of the indenter is a circular surface with a diameter of 100 μm, so the indenter area is 7.85 × 10 ^-9 m ² .

FIG. 2 shows the displacement-load curve of the crosslinked polyrotaxane molded product in the above compression test, and the compression characteristics were obtained from the curve and shown in Table 1 below. First, the load at the bending point where the curve of the same curve rises is about 300 mN, and as will be described later, no internal structural change was observed before the bending point, so the load at the bending point is the compression limit load (a). The compression limit stress (referred to as b) was obtained by dividing a by the indenter area. Further, the displacement at the yield point is defined as the compression limit displacement (c), the displacement at the a / 2 load (d) is defined as the 1/2 compression limit displacement (e), and the displacement difference c-. e (referred to as f) was obtained. Then, 2 × f / t was defined as the compression limit rate (referred to as g), and b / g was defined as the compressive elastic modulus (referred to as h).

3 (a) to 3 (d) show a predetermined load ((a) 100 mN, (b) 200 mN, (c) 300 mN, (d) 400 mN) on the crosslinked polyrotaxane molded product with the indenter, apart from the compression test. It is a photomicrograph of a crosslinked polyrotaxane molded product when it is loaded and then unloaded, and the circular line shows the edge of the compression range by the indenter (hereinafter referred to as "compression edge") in the photograph (diameter 100 μm). .. No change in internal structure along the compression edge was observed by observing any of the micrographs.

FIG. 4 (a) is a displacement-load curve of the polyurethane molded product in the compression test, and FIG. 4 (b) is an enlarged curve of the IVb portion of (a), and the compression characteristics are obtained from the enlarged curve. It is shown in Table 1 above. First, the load at the bending point where the curve of FIG. 4A rises is about 710 mN, which seems to be stronger than that of the crosslinked polyrotaxane molded product. However, as will be described later, since the internal structural change was observed at a load of 50 mN long before the bending point, the load at the bending point was not set as the compression limit load, and the internal structural change point of the enlarged curve in FIG. 4 (b) was used. The load of 50 mN was evaluated as the compression limit load (referred to as a), and a was divided by the indenter area to obtain the compression limit stress (referred to as b). Further, the displacement due to the internal structural change is defined as the compression limit displacement (c), the displacement due to the a / 2 load (d) is defined as the 1/2 compression limit displacement (e), and the displacement difference c between them. -E (referred to as f) was obtained. Then, 2 × f / t was defined as the compression limit rate (referred to as g), and b / g was defined as the compressive elastic modulus (referred to as h).

5 (a) to 5 (d) show that, apart from the compression test, a predetermined load ((a) 20 mN, (b) 50 mN, (c) 100 mN, (d) 200 mN) is applied to the polyurethane molded product with the indenter. It is a micrograph of the polyurethane molded body when it was loaded and then unloaded, and the circular line is a compression edge (diameter 100 μm). A 20 mN micrograph did not show a clear internal structural change along the compressed edge, but a 50 mN micrograph began to show a clear internal structural change with a large number of granular precipitates appearing along the compressed edge. In the micrograph of 100 mN and 200 nm, the change in the internal structure became remarkable. The precipitate is considered to be a polyol component that did not react with the isocyanate component during the urethane reaction.

As described above, the compression limit load is evaluated by the smaller of the load at the yield point and the load at the internal structural change point. It can be said that the crosslinked polyrotaxane molded product has a higher compression limit stress than polyurethane and does not change to a larger pressure.

<4> Fabrication of Compression Sensor of Example 1 As shown in FIG. 6A, an insulator, an electrode, a dielectric elastomer layer, a frame-shaped spacer, an electrode, and an insulator are laminated in this order from bottom to top. The compression sensor of Example 1 having an air layer as a gas layer sandwiched between a lower electrode and a dielectric elastomer layer and surrounded by a frame of a spacer was produced.

The two insulators are polycarbonate sheets.

The two electrodes are obtained by applying a silicone elastomer composition solution having the following composition (the compounding value is parts by mass) to an insulator by the slit die coater method, and cross-linking and curing the insulator at 100 ° C. for 24 hours. It is 20 μm.
Silicone elastomer 10
Organic solvent (heptane) 300
Carbon particles (Ketchen black) 1

The dielectric elastomer layer is obtained by applying the polyrotaxane composition solution to the upper electrode by a slit die coater method, cross-linking and curing at 130 ° C. × 5 hours (cross-linked polyrotaxane), and has a thickness of 50 μm. Therefore, the dielectric elastomer layer has a compression limit stress of 3.8 × 10 ¹ MPa and a compressive elastic modulus of 1.0 × 10 ² MPa.

The spacer is a molded product formed in a frame shape by the crosslinked polyrotaxane, and has a thickness of 300 μm. Therefore, the spacer has a compression limit stress of 3.8 × 10 ¹ MPa and a compressive elastic modulus of 1.0 × 10 ² MPa.

The air layer is made of air and has a thickness of 300 μm, which is equal to that of the spacer.

The compression sensor of Example 1 is easily compressed and deformed by an external force, and the air layer is first compressed, and then the dielectric elastomer layer is in contact with the lower electrode and then compressed, and is static at any stage. External force can be detected by fluctuating the electric capacity.

<5> Fabrication of Compression Sensor of Example 2 In the compression sensor of Example 2 shown in FIG. 6B, the air layer of Example 1 is a gas layer made of a low dielectric constant gas having a dielectric constant lower than that of air. It is replaced with a low dielectric constant gas layer, and the others are the same as in Example 1.

<6> Actions and effects of the compression sensor of Examples The compression sensors of Examples 1 and 2 have a low compressive elastic modulus of 5.0 × 10 ² MPa or less, so that they are easily compressed and deformed with a slight force, and this slight amount is obtained. Force can be measured.
In addition, since the compression limit stress is as high as ^1.0 × 101 MPa or more, a large force that repeatedly works can be measured with good reproducibility.
Moreover, since the compression limit rate is as high as 20% or more, the resolution of the sensor is high.
Since the crosslinked polyrotaxane having a high dielectric constant is used for the dielectric elastomer layer, the capacitance greatly fluctuates even at the stage where the air layer is compressed, and the resolution is improved.

In addition, the compression sensors of Examples 1 and 2 have the following effects.
-Has durability that can measure vertical stress without breaking.
-Since the compression sensor itself contains an elastomer, it enhances the grip on the gripped object.
-From the amount of deformation of the compression sensor, the gripping force, the weight of the gripping object, etc. can be measured in the stationary state, and the moment of inertia, the speed, the moving amount, etc. can be measured when the gripping object moves so as to cause inertia.
-High resolution, wide dynamic range measurement, and high S / N ratio make it possible to reduce the size of the sensor, and it is possible to mount it in a narrow space and measure the load distribution by arranging it. By measuring the load distribution, the contact surface with the gripping object can be grasped, and the posture and gripping position of the gripping object can be measured and monitored.
-These measurement information can be used for reinforcement learning in combination with AI, and can be used for stable gripping of an object, optimization of a transportation method, and the like.

<7> Usage of the compression sensor of the embodiment The compression sensor of the first and second embodiments can be used in the following embodiments, for example, by taking advantage of the above-mentioned effects.
-As shown in FIG. 7 (a), a compression sensor is attached to the finger of the hand part of an industrial robot or a construction machine for use.
-As shown in Fig. 7 (b), by attaching a compression sensor to the shoe insole or the sole of a heavy-duty robot, posture monitoring during walking / running and measurement of weight transfer during sports can be performed. ..
-In addition, by arranging the compression sensor on the mat-shaped sheet, it is possible to measure the load on the mat and the movement of the center of gravity, and to use it according to various shapes that were difficult with the conventional mat sensor. ..

The present invention is not limited to the above embodiment, and can be appropriately modified and embodied without departing from the spirit of the invention.

Claims (7)

In a compression sensor that includes a spacer and a pair of electrodes separated by a spacer with a gas layer separated, and measures the compressive force acting on the sensor by measuring the electrostatic capacitance between the electrodes, the spacer material is the compression limit stress. Is 1.0 × 10 ¹ MPa or more, and the compressive elastic modulus is 5.0 × 10 ² MPa or less. The compression sensor according to claim 1, wherein the spacer material has a compression limit rate of 20% or more. The compression sensor according to claim 1 or 2, wherein the spacer material has a compression limit stress of 2.0 × 10 ¹ MPa or more. The compression sensor according to claim 1, 2 or 3, wherein the spacer material has a compressive elastic modulus of 2.0 × 10 ² MPa or less. The compression sensor according to any one of claims 1 to 4, wherein the spacer material is made of crosslinked polyrotaxane. The compression sensor according to any one of claims 1 to 5, which has a dielectric elastomer layer in addition to a gas layer between the pair of electrodes. The compression sensor according to claim 6, wherein the dielectric elastomer layer is formed of crosslinked polyrotaxane.

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