Bending sensor and deformed shape measurement method
Provided are a bending sensor that is less dependent on an input speed of a strain and in which a response delay is unlikely to occur, and a deformed shape measurement method using the bending sensor. The bending sensor is configured to include a base material; a sensor body arranged on a surface of the base material and containing a matrix resin and conductive filler particles filled in the matrix resin at a filling rate of 30% by volume or more, and in which three-dimensional conductive paths are formed by contact among the conductive filler particles, and electrical resistance increases as an deformation amount increases; an elastically deformable cover film arranged so as to cover the sensor body; and a plurality of electrodes connected to the sensor body and capable of outputting electrical resistances. In the sensor body, cracks are formed in advance in such a direction that the conductive paths are cut off during a bending deformation.
1. A bending sensor comprising:
a base material;
a sensor body arranged on a surface of the base material and containing a matrix resin and conductive filler particles, the conductive filler particles being 30% by volume or more of the matrix resin, and in which three-dimensional conductive paths are defined by contact among the conductive filler particles and when a deformation amount of the sensor body increases, an electrical resistance increases;
an elastically deformable cover film arranged so as to cover the sensor body;
a strain adjustment plate arranged on a rear surface of the base material;
an adhesion layer bonding the strain adjustment plate and the base material; and
a plurality of electrodes connected to the sensor body and capable of outputting electrical resistances, wherein
cracks are provided in the sensor body along such a direction that the conductive paths are cut off during a bending deformation of the sensor body, the cracks being pre-formed on the sensor body by a deformation of a precursor of the sensor body along a mold surface of a mold for crack formation, and
the base material, the strain adjustment plate, and the adhesion layer are all made from materials having a glass-rubber transition region, in which a storage elastic modulus transitions, on one of a lower temperature side than a lower temperature limit of an operating temperature range of the bending sensor minus 10° C., or on a higher temperature side than an upper temperature limit of the operating temperature range of the bending sensor plus 10° C., and a pre-determined strain is provided in a bending direction in the sensor body.
2. The bending sensor according to claim 1 , wherein the conductive filler particles have an average particle size of 0.05 μm or more and 100 μm or less.
3. The bending sensor according to claim 1 , wherein the conductive filler particles are spherical carbon particles.
4. The bending sensor according to claim 1 , wherein, when a plurality of unit sections each having a length of 2 mm or less are partitioned in the sensor body in a direction along which the electrodes are arranged, at least one crack is provided in each of the unit sections.
5. The bending sensor according to claim 1 , wherein the plurality of the electrodes are a printed conductive paint on the base material.
6. The bending sensor according to claim 5 , wherein the electrodes have such a surface shape that an edge line in a direction along which the sensor body extends has a curved portion.
7. The bending sensor according to claim 1 further comprising wirings respectively connected to the electrodes, the wirings being an etched metal foil.
8. The bending sensor according to claim 1 , wherein, between two of the electrodes, the sensor body has a plurality of detection sections lined up in a perpendicular direction, each of the detection sections extending in a juxtaposing direction, the juxtaposing direction being a direction along which the two electrodes line up, and the perpendicular direction being a direction perpendicular to the juxtaposing direction.
9. The bending sensor according to claim 8 , wherein, between neighboring two of the electrodes, the detection sections are mutually electrically connected in parallel.
10. The bending sensor according to claim 8 , wherein, between neighboring two of the electrodes, the detection sections are mutually electrically connected in series.
11. The bending sensor according to claim 8 , wherein at least five of the detection sections are arranged.
12. A deformed shape measurement method comprising:
a detection process detecting a bending deformation of the bending sensor according to claim 1 for each of a plurality of measurement sections partitioned by the electrodes;
a partial shape calculation process calculating deformed shapes of the measurement sections based on detected deformation data of the measurement sections; and
an entire shape calculation process calculating an entire deformed shape of the bending sensor by joining together the calculated deformed shapes of the measurement sections.