JP5622471B2 - Resistance increasing sensor and method of manufacturing the same - Google Patents

Description

The present invention relates to a resistance increasing sensor capable of detecting bending deformation of a measurement object and a method for manufacturing the same .

  Patent Document 1 discloses a resistance increasing sensor capable of detecting a load applied to a measurement object. FIG. 16 shows a front view of the resistance increasing sensor described in the document. As shown in FIG. 16, the resistance increasing sensor 100 includes a restraint plate 101, a sensor main body 102, two electrodes 103 a and 103 b, two wirings 104 a and 104 b, and a connector 105. The restraint plate 101 is fixed to a measurement object (not shown).

  The sensor main body 102 has an elastomer and a large number of conductive fillers. Many conductive fillers are filled in an elastomer. In an undeformed state (non-deformed state), a large number of three-dimensional conductive paths are formed in the sensor main body 102 by a large number of conductive fillers being connected. In the deformed state (the state in which the deformed state is deformed with respect to the undeformed state), the conductive filler moves. For this reason, the conductive path is easily interrupted. Therefore, the electrical resistance of the sensor body 102 increases.

  When the measurement object is bent and deformed by the load, the sensor main body 102 is also bent and deformed. For this reason, the electrical resistance of the sensor main body 102 increases. The electrical resistance of the sensor body 102 is transmitted to an arithmetic device (not shown) via the electrodes 103a and 103b, the wirings 104a and 104b, and the connector 105. The arithmetic device detects the load applied to the measurement object from the increase in the electrical resistance.

JP 2008-70327 A

However, according to the resistance increasing sensor 100 described in the same document, the variation in the detected electrical resistance was large. That is, even when the load applied to the measurement object is equal, the detected electrical resistance is likely to vary. The resistance increasing sensor and the manufacturing method thereof according to the present invention have been completed in view of the above problems. It is an object of the present invention to provide a resistance increasing type sensor having a small variation in electric resistance and a method for manufacturing the same.

  (1) In order to solve the above-mentioned problem, the resistance increasing type sensor of the present invention has a base material made of resin or elastomer and a conductive filler filled in the base material, and the amount of bending deformation increases. A sensor body whose electrical resistance increases as it goes, at least two electrodes connected to the sensor body and outputting an electric quantity related to the electrical resistance, and laminated on one surface of the sensor body, and elastic deformation of the one surface And a restraint plate that restrains the sensor body, wherein the sensor body extends in the juxtaposition direction, with the direction in which the two electrodes are aligned being the juxtaposition direction and the direction orthogonal to the juxtaposition direction being the orthogonal direction. And a plurality of detectors arranged in the orthogonal direction.

  In the non-deformed state (the undeformed state), a large number of three-dimensional conductive paths are formed in the sensor body by connecting a large number of conductive fillers. In the deformed state (the state in which the deformed state is deformed with respect to the undeformed state), the conductive filler moves. For this reason, the conductive path is easily interrupted. Therefore, the electrical resistance of the sensor body increases with respect to the undeformed state.

  The resistance increasing sensor of the present invention includes a restraining plate. The restraining plate restricts free elastic deformation of one surface of the sensor body. For this reason, in the deformed state, bending deformation is induced in the sensor body. In particular, when the thickness of the sensor body is small, the compression deformation of the sensor body can be almost ignored. For this reason, bending deformation is dominant in elastic deformation of the sensor body.

  The base material of the sensor body is made of resin or elastomer. For this reason, the resistance increase type sensor of this invention is excellent in workability. The resistance increasing sensor of the present invention has a high degree of freedom in shape design. Therefore, even if the shape of the measurement object is complicated, the resistance increasing sensor of the present invention can be arranged.

  The sensor body includes a plurality of detection units. Each of the plurality of detection units extends in the juxtaposition direction. The plurality of detection units are arranged in a direction orthogonal to each other. For this reason, according to the resistance increasing type sensor of the present invention, as compared with the resistance increasing type sensor having a single detecting unit (see FIG. 16), when the total area of the detecting unit is equal, variation in electric resistance is reduced. be able to.

  (1-1) Preferably, in the configuration of the above (1), the conductive filler is spherical, and the base material is filled in a substantially single particle state with a high filling rate. Good. Here, the “substantially single particle state” means that 50% by mass or more when the total weight of the conductive filler is 100% by mass exists not in the form of aggregated secondary particles but in the form of single primary particles. It means that Further, “high filling rate” means that the conductive filler is blended in a state close to closest packing. In addition, “spherical” includes not only a true sphere and a substantially true sphere, but also an oval sphere, an oval sphere (a shape in which a pair of opposing hemispheres are connected by a cylinder), a partial sphere, a sphere having a different radius for each part, Etc. are included. According to this configuration, the conductive path is easily interrupted when switching from the non-deformed state to the deformed state. For this reason, the sensitivity of the resistance increasing type sensor can be improved.

  (2) Preferably, in the configuration of (1), the plurality of detection units may be electrically connected in parallel between two adjacent electrodes. In the case of parallel connection, if the electrical resistances of the detection units (1, 2,..., N) are R1, R2,..., Rn and the combined electrical resistance is R, 1 / R = 1 / R1 + 1 / R2 + ... + 1 / Rn. For this reason, even if the electric resistance of an arbitrary detection unit varies, variations in the entire sensor body can be reduced. Therefore, variation in the combined electrical resistance R can be reduced. Moreover, according to this structure, since the some detection part is connected in parallel, even if it increases the number of arrangement | positioning of a detection part, the synthetic | combination electrical resistance R does not increase easily.

  (3) Preferably, in the configuration of (1), the plurality of detection units may be electrically connected in series between two adjacent electrodes. In the case of series connection, R = R1 + R2 +... + Rn, where R1, R2,..., Rn and the combined electrical resistance are R, where R1, R2,. . For this reason, even if the electric resistance of an arbitrary detection unit varies, variations in the entire sensor body can be reduced. Therefore, variation in the combined electrical resistance R can be reduced. Moreover, according to this structure, the some detection part is connected in series like one stroke writing. For this reason, even if the number of arrangement | positioning of a detection part is increased, it is not necessary to change the structure of the connection part of a sensor main body and an electrode.

  (4) Preferably, in the configuration according to any one of (1) to (3), the base material further includes an elastically deformable cover film that covers the other surface of the sensor body facing away from the one surface. Is a resin, and the conductive filler is filled in the base material at a filling rate of 30% by volume or more with the volume of the sensor body being 100% by volume, and the sensor body is bent and deformed. When doing so, it is better to have a configuration in which a crack is formed in advance so as to cut a conductive path formed by a plurality of the conductive fillers.

  According to this configuration, the conductive filler is filled in the base material at a filling rate of 30% by volume or more. That is, a large amount of conductive filler is blended in the sensor body. For this reason, the sensor main body has high conductivity in an undeformed state.

  The sensor body is previously cracked. The crack is formed in a direction that cuts the conductive path when the sensor body is bent and deformed. FIG. 1A shows an enlarged schematic view of the vicinity of a crack in the sensor body in an undeformed state. FIG. 1B shows an enlarged schematic view of the vicinity of a crack in the deformed sensor body. However, FIGS. 1A and 1B are schematic diagrams for explaining the resistance increasing sensor of this configuration. 1A and 1B are not intended to limit the present configuration in any way, for example, the shape of a crack, the extending direction of a crack, the shape of a conductive filler, the shape of a conductive path, and the extending direction of a conductive path. Absent.

  As shown in FIG. 1A, the sensor body 800 includes a base material 801, a conductive filler 802, and a crack 803. In the undeformed state, a conductive path p is formed in the sensor body 800 by contact between the conductive fillers 802. The crack 803 is formed in a direction crossing the left-right direction (extension direction during bending deformation) in the drawing.

  As shown in FIG. 1B, in the deformed state, the sensor body 800 is extended in the left-right direction. For this reason, the crack 803 opens. Therefore, the contact between the conductive fillers 802 is cut off, and the conductive path p is cut. As a result, the electrical resistance of the sensor body 800 increases.

  Thus, according to this configuration, when strain is input to the sensor body, the conductive path is cut mainly by the opening of the crack without waiting for elastic deformation of the base material (however, the resistance increase of this configuration is increased) The type sensor does not exclude the case where the conductive path is cut by elastic deformation of the base material. Therefore, response delay is unlikely to occur.

  Further, since the conductive path is cut mainly by the opening of the crack, it is possible to detect even a small distortion with high accuracy compared to the case where the conductive path is cut only depending on the elastic deformation of the base material.

  The speed of elastic deformation of the base material is affected by the ambient temperature. In this respect, the conductive path of the resistance increasing type sensor of this configuration is cut mainly by the opening of the crack. For this reason, the dependence of the response speed on the ambient temperature is small as compared with the case where the conductive path is cut only depending on the elastic deformation of the base material.

  The sensor body is covered with a cover film. For this reason, deterioration of the sensor body is suppressed. Further, the cover film can be elastically deformed. Therefore, when switching from the deformed state to the undeformed state, the sensor body is easily restored to the original shape, assisted by the elastic restoring force of the cover film. In addition, an open crack can easily return to its original state.

  The sensor body and the restraining plate are stacked. By adjusting the thickness of the restraint plate, the amount of distortion of the sensor body during bending deformation can be adjusted. For this reason, the sensitivity of the resistance increasing sensor can be adjusted.

  Moreover, the sensor main body is previously cracked at the time of manufacture. For this reason, a new crack is hard to be formed at the time of bending deformation. Therefore, the sensitivity of the resistance increasing sensor is unlikely to change.

  (4-1) Preferably, in the configuration of (4) above, the conductive filler may have an average particle size of 0.05 μm or more and 100 μm or less.

  When the particle size of the conductive filler is small, the reinforcing effect on the base material is increased. For this reason, a crack is hard to be formed. Further, since the breaking strain of the sensor body (strain when a crack occurs in the sensor body) increases, the increase in electrical resistance is more likely to depend on the elastic deformation of the sensor body than the opening of the crack. Further, when the sensor main body is arranged by applying a paint to the restraining plate, it is difficult to convert the sensor material including the base material and the conductive filler into a paint when the sensor main body is manufactured. From such a viewpoint, it is desirable that the average particle diameter of the conductive filler is 0.05 μm or more. If it carries out like this, it will become easy to form a crack along the interface of a conductive filler. Moreover, it becomes easy to open a crack in the interface of an electroconductive filler, and the fracture | rupture distortion of a sensor main body can be made small. The average particle diameter of the conductive filler is more preferably 0.5 μm or more, and further preferably 1 μm or more.

  On the other hand, when the average particle diameter of the conductive filler exceeds 100 μm, the number of conductive paths in the non-deformed state is reduced, and the contact state of the conductive filler is less likely to change due to bending deformation, resulting in a change in electrical resistance. Become slow. In addition, it is difficult to reduce the thickness of the sensor body, that is, the thickness of the detection unit. For this reason, it becomes difficult to increase the density of cracks. The average particle diameter of the conductive filler is more preferably 30 μm or less, and further preferably 10 μm or less. In addition, as an average particle diameter, the particle diameter (D50) from which an integrated weight will be 50% in the cumulative particle size curve of an electroconductive filler is employ | adopted.

  (4-2) Preferably, in the configuration of the above (4), the conductive filler is preferably spherical carbon. By making the shape of the conductive filler spherical, the conductive filler can be blended in the base material in a state close to closest packing. Thereby, a three-dimensional conductive path is easily formed, and desired conductivity is easily developed. In addition, the contact state of the conductive filler tends to change with respect to the elastic deformation of the sensor body. For this reason, the change in electrical resistance is large. Further, as the spherical carbon, those having few surface functional groups are desirable. When there are few functional groups on the surface, breakage is likely to occur at the interface with the base material, and cracks are likely to be formed in the sensor body.

  (4-3) Preferably, in the configuration of the above (4), in the sensor body, when a plurality of unit sections having a length of 2 mm or less continuous in the juxtaposition direction are divided, the cracks are in the unit sections. It is better to have a configuration in which at least one is formed.

  As described above, the sensitivity of the resistance increasing type sensor depends on the density of cracks formed in the sensor body (the number of cracks per unit length in the arrangement direction of the two electrodes). The reason why the length of the unit section is set to 2 mm or less is that when it exceeds 2 mm, the density of cracks is reduced and the sensitivity of the resistance increasing sensor is lowered. In other words, it is difficult to achieve a desired sensitivity. More preferably, the length of the unit section is 1 mm or less. This further improves the sensitivity of the resistance increasing type sensor.

  (5) Preferably, in the configuration of (4) above, the crack is preferably formed by deforming the precursor of the sensor body along the mold surface of the crack forming mold. . Here, the “sensor body precursor” means a sensor body that is completed. For example, when the sensor body is formed by a printing method, it refers to a coating film.

  The variation in electrical resistance depends on the density of cracks. That is, as the density of cracks increases, the locus of deformation of the sensor body becomes more stable. For this reason, variation in electrical resistance is reduced. The sensitivity of the resistance increasing sensor also depends on the crack density. That is, the greater the crack density, the higher the sensitivity of the resistance increasing sensor.

  According to this configuration, the crack is formed by deforming the sensor body along the mold surface of the crack forming mold. FIG. 2 shows a cross-sectional view of the detection unit before crack formation. FIG. 3 shows a cross-sectional view of the detection part after crack formation. However, FIG. 2 and FIG. 3 are schematic diagrams for explaining the resistance increasing sensor of this configuration. 2 and 3 do not limit the present configuration in any way, such as the shape of the detection unit, the restraint plate, the shape of the crack forming mold, and the shape of the mold surface.

  As shown in FIG. 2, the detection unit 70 is stacked on the upper surface of the restraint plate 71. Both the detection unit 70 and the restraining plate 71 have a flat plate shape extending in the left-right direction. As shown in FIG. 3, the mold surface (outer peripheral surface) 720 of the crack-forming mold 72 has a curved shape that swells upward. By pressing the lower surface 710 of the restraining plate 71 against the mold surface 720, a crack is formed in the detection unit 70.

Here, when the distance between adjacent cracks is L, the thickness of the detection part is d, the width in the orthogonal direction of the detection part is b, and the compressive fracture stress of the detection part is σEb, the surface pressure required to form the crack (Surface pressure when pressing the lower surface 710 against the mold surface 720) P is expressed by the following equation (1).

If the surface pressure P exceeds the compressive fracture stress σEb, compressive fracture occurs before the crack is formed. Therefore, the surface pressure P ≦ the compressive fracture stress σEb. In order to increase the density of cracks, it is necessary to make the distance L between adjacent cracks as small as possible. In order to minimize the distance L, it is necessary to press the restraint plate 71 against the mold surface 720 with a surface pressure P as large as possible within a range not exceeding the compressive fracture stress σEb. When the maximum value Pmax = σEb of P is substituted into the equation (1), the minimum value Lmin of the distance L is expressed by the following equation (2).

  From equation (2), it can be seen that the minimum value Lmin of the distance L is determined by the thickness d of the detection unit 70 and the orthogonal direction width b of the detection unit.

  Thus, in order to increase the density of cracks, there are means of (A) reducing the thickness of the detection unit 70 and (B) reducing the orthogonal width of the detection unit 70. There are also means for (C) reducing the radius of curvature of the mold surface 720 of the crack forming mold 72 and (D) reducing the thickness of the restraint plate 71.

  In this regard, according to the resistance increasing type sensor of the present invention, the sensor body includes a plurality of detection units. Each of the plurality of detection units extends in the juxtaposition direction. The plurality of detection units are arranged in a direction orthogonal to each other. For this reason, according to this structure, when the total area of a detection part is equal compared with the resistance increase type sensor (refer FIG. 16) which has a single detection part, the orthogonal | vertical direction width | variety of a detection part can be made small. (Corresponding to the means (B) above). Therefore, the density of cracks can be increased. That is, variation in electrical resistance can be reduced. In addition, the sensitivity of the resistance increasing sensor can be improved.

  (6) Preferably, in the configuration of (4) or (5), it is better to have a configuration in which strain is input in advance to the sensor body.

  When the sensor body is bent, an elastic region appears in the initial stage of bending deformation, and a region greater than the breaking strain appears in the subsequent stage.

  FIG. 4 is a schematic graph showing the relationship between the strain amount of the sensor body and the electrical resistance. However, FIG. 4 does not limit this configuration at all. As shown in FIG. 4, the amount of distortion increases as the sensor body is bent. As the amount of strain increases, the electrical resistance also increases.

  Here, as indicated by an arrow Y1 in the figure, in the initial stage of bending deformation, the electrical resistance rises in a substantially quadratic curve with respect to the strain amount. For this reason, as shown by a point X1 in the figure, the responsiveness of the electrical resistance to the strain amount at the beginning of the bending deformation is lowered. The region indicated by the arrow Y1 is estimated as the elastic region of the sensor body.

  Further, as indicated by an arrow Y2 in the figure, in the stage after the initial stage of the bending deformation, the electrical resistance rises substantially linearly with respect to the strain amount. In addition, as shown by a point X2 in the figure, the responsiveness of the electrical resistance to the strain amount is higher than that of the point X1. In addition, it is estimated that the area | region shown by arrow Y2 is an area | region more than the fracture | rupture distortion beyond the elastic area | region of a sensor main body.

  Therefore, compared to the case where only the elastic region of the sensor body is used as the detection region for bending deformation, the region above the breaking strain of the sensor body is used (when only the region above the breaking strain is used, and the elastic region). And the region where the strain equal to or greater than the breaking strain is used together), the change in electrical resistance when the same strain amount is input becomes larger. For this reason, the sensitivity of the resistance increasing sensor is improved. In addition, since the electrical resistance rises substantially linearly with respect to the strain amount, the strain amount can be easily calculated from the electrical resistance.

  In this regard, according to this configuration, distortion is input to the sensor body in advance. For this reason, the total strain amount at the time of bending deformation of the sensor body is the sum of the strain amount input in advance and the strain amount accompanying the bending deformation. That is, the total strain amount of the sensor main body is larger than the case of only the strain amount accompanying the bending deformation. Thereby, it becomes easy to use the area | region beyond the fracture | rupture distortion of a sensor main body as a detection area. That is, it becomes easy to shift the detection region to a region where the relationship between the strain amount and the electrical resistance is linear (distortion offset). Therefore, according to this configuration, the sensitivity of the resistance increasing sensor is improved. Moreover, it becomes easy to calculate the amount of strain, and hence the shape of the sensor body during bending deformation, from the electrical resistance.

  (7) Preferably, in the configuration of any one of the above (1) to (6), it is preferable that five or more detection units are arranged. As will be apparent from the examples described later, when five or more detectors are arranged, the coefficient of variation (= standard deviation) in electrical resistance compared to a resistance increasing sensor (see FIG. 16) having a single detector. / Average value) can be reduced to 1/2 or less.

  Further, when ten or more detection units are arranged, the coefficient of variation of the electrical resistance can be reduced to 1/3 or less as compared with a resistance increasing sensor (see FIG. 16) having a single detection unit. Furthermore, when 20 or more detection units are arranged, the coefficient of variation of electrical resistance can be reduced to ¼ or less as compared with a resistance increasing sensor (see FIG. 16) having a single detection unit.

ADVANTAGE OF THE INVENTION According to this invention, the resistance increase type sensor with a small dispersion | variation in electrical resistance, and its manufacturing method can be provided.

(A) is the schematic diagram which expanded the vicinity of the crack in the sensor main body of an undeformed state. (B) is the schematic diagram which expanded the vicinity of the crack in the sensor main body of a deformation | transformation state. It is sectional drawing of the detection part before crack formation. It is sectional drawing of the detection part after crack formation. It is a schematic graph showing the relationship between the distortion amount of a sensor main body, and an electrical resistance. It is a front view of a resistance increase type sensor of a first embodiment. It is VI-VI sectional drawing of FIG. It is an enlarged view in the circle VII of FIG. It is sectional drawing seen from the downward direction of the resistance increase type sensor before the collision of a collision object. It is sectional drawing seen from the downward direction of the resistance increase type sensor after the collision of a collision object. It is a front view of the resistance increase type sensor of 2nd embodiment. It is the schematic diagram of the first half of the bending hardening process of the manufacturing method of the resistance increase type sensor of 3rd embodiment. It is a schematic diagram of the latter half of the process. It is a graph which shows the relationship between the number of strip | lines and an electrical resistance ratio at the time of connecting a detection part in parallel. It is a graph which shows the relationship between the number of strips at the time of connecting a detection part in series, and an electrical resistance ratio. It is a graph which shows the relationship between the number of strip | lines and the case of a case where a detection part is connected in parallel, and a case where it connects in series. It is a front view of the conventional resistance increase type sensor.

Embodiments of a resistance increasing sensor and a method for manufacturing the same according to the present invention will be described below.

<First embodiment>
[Configuration of resistance increasing sensor]
First, the configuration of the resistance increasing sensor of this embodiment will be described. FIG. 5 shows a front view of the resistance increasing type sensor of the present embodiment. For convenience of explanation, the cover film 25 is removed and shown. FIG. 6 is a cross-sectional view taken along the line VI-VI in FIG. As shown in FIGS. 5 and 6, the resistance increasing sensor 1 includes a restraint plate 20, a sensor body 21, electrodes 22 a and 22 b, wirings 23 a and 23 b, a connector 24, and a cover film 25. ing.

  The restraint plate 20 is made of polyimide (PI) and has a strip shape extending in the left-right direction. The left-right direction corresponds to the juxtaposition direction of the present invention. The thickness of the restraint plate 20 is about 300 μm. A connector 24 is disposed at the lower left end of the restraint plate 20. The restraint plate 20 is fixed to a bumper cover (not shown).

  The sensor main body 21 includes five detection units 210 to 214. Each of the detection units 210 to 214 has a strip shape extending in the left-right direction. The detection units 210 to 214 are juxtaposed in the vertical direction. The vertical direction corresponds to the orthogonal direction of the present invention. The thickness of each of the detection units 210 to 214 is about 100 μm. The detection units 210 to 214 are fixed to the surface (rear surface) of the restraining plate 20. The “front surface” of the sensor body 21 corresponds to “one surface” of the sensor body of the present invention. The “rear surface” of the sensor body 21 corresponds to the “other surface” of the sensor body of the present invention.

  The sensor body 21 includes an epoxy resin and a large number of carbon beads. The epoxy resin is included in the base material of the present invention. Carbon beads are included in the conductive filler of the present invention. Many carbon beads are filled in an epoxy resin. The filling rate of the carbon beads is about 45% by volume when the volume of the sensor body 21 is 100% by volume.

  FIG. 7 shows an enlarged view in a circle VII in FIG. As schematically shown in FIG. 7, a large number of cracks C <b> 1 are formed in the sensor body 21 in advance. The crack C <b> 1 is arranged so as to extend in the direction intersecting the juxtaposition direction, that is, in the thickness direction (front-rear direction) of the sensor body 21. About two cracks C <b> 1 are formed in the unit section U <b> 1 having a length of 2 mm that is continuous in the left-right direction of the sensor body 21.

  5 and 6, the electrodes 22a and 22b each have a strip shape extending in the vertical direction. The electrodes 22a and 22b are interposed between the restraint plate 20 and the sensor main body 21, respectively. The electrode 22 a is connected to the left end of the sensor body 21. The electrode 22 b is connected to the right end of the sensor body 21. In other words, the five detection units 210 to 214 are installed between the pair of left and right electrodes 22a and 22b. The wiring 23 a connects the electrode 22 a and the connector 24. The wiring 23b connects the electrode 22b and the connector 24. An arithmetic device (not shown) is connected to the connector 24.

  The cover film 25 is made of acrylic rubber and has a strip shape extending in the left-right direction. The cover film 25 covers the restraint plate 20, the sensor main body 21, the electrodes 22a and 22b, and the wirings 23a and 23b from the rear. The cover film 25 has a thickness of about 20 μm.

[Manufacturing method of resistance increasing sensor]
Next, a manufacturing method of the resistance increasing sensor 1 of the present embodiment will be described. The manufacturing method of the resistance increasing type sensor 1 of the present embodiment includes a paint preparation process, a printing process, a curing process, a crack forming process, and a cover film printing process.

  In the paint preparation step, a sensor paint, an electrode paint, a wiring paint, a connector paint, and a cover film paint are prepared. Specifically, the sensor paint was prepared by using 100 parts by mass of an epoxy resin pre-curing resin (“Pernox (registered trademark) ME-562” manufactured by Nippon Pernox Co., Ltd .; liquid) and a curing agent (“Percure (registered trademark)” manufactured by the same company. ) HV-562 "; liquid" 150 parts by mass and 225 parts by mass of carbon beads ("Nika beads (registered trademark) ICB0520" manufactured by Nippon Carbon Co., Ltd., average particle diameter of about 5 m)) are mixed by blade stirring. To do. “Dotite (registered trademark) FA-312” manufactured by Fujikura Kasei Co., Ltd. is used for the electrode paint, the wiring paint, and the connector paint. The cover film paint is prepared as follows.

  First, 100 parts by mass of an acrylic rubber polymer (“Nippol (registered trademark) AR51” manufactured by Nippon Zeon Co., Ltd.) and 1 mass of stearic acid (“Lunac (registered trademark) S30” manufactured by Kao Corporation) as a vulcanization aid And 2.5 parts by mass of a vulcanization accelerator zinc dimethyldithiocarbamate (“Noxeller (registered trademark) PZ” manufactured by Ouchi Shinsei Chemical Co., Ltd.) and ferric dimethyldithiocarbamate (“Noxeller TTFE” manufactured by the company) ) 0.5 parts by mass is mixed with a roll kneader to prepare an elastomer composition. Next, the prepared elastomer composition is dissolved in 312 parts by mass of a printing solvent, ethylene glycol monobutyl ether acetate.

  In the printing process, a paint other than the cover film paint is printed on the surface of the restraint plate 20 using a screen printer. First, electrode paint, wiring paint, and connector paint are printed on the surface of the restraint plate 20 in order. Next, the constraining plate 20 after printing the paint is left in a drying furnace at about 140 ° C. for about 30 minutes to cure the coating film. In this manner, the electrodes 22a and 22b, the wirings 23a and 23b, and the connector 24 are formed. Subsequently, the sensor paint is printed on the surface of the restraint plate 20 on which the electrodes 22a, 22b and the like are formed.

  In the curing step, the constraining plate 20 on which the sensor paint is printed is heated to cure the coating film. Specifically, the restraint plate 20 on which the coating film of the sensor paint is formed is placed in a drying furnace and held at about 140 ° C. for 1 hour to primarily cure the coating film. Then, it hold | maintains at about 170 degreeC for 2 hours, and carries out secondary hardening of the coating film.

  In the crack forming step, a crack is formed in the coating film. The coating film is included in the “sensor body precursor” of the present invention. Specifically, as shown in FIG. 3, the mold surface of the crack forming mold has a curved surface. On the other hand, the restraint plate 20 has a flat plate shape. A crack is formed in the coating film by pressing the restraint plate 20 against the mold surface. In this way, the sensor body 21 is produced.

  In the cover film printing process, the cover film paint prepared in the paint preparation process is printed using a screen printer. First, a cover film paint is printed so as to cover the surfaces of the restraint plate 20, the sensor main body 21, the electrodes 22a and 22b, and the wirings 23a and 23b. Next, the constraining plate 20 after printing the paint is left in a drying furnace at about 150 ° C. for about 30 minutes to cure the coating film. In this way, the cover film 25 is formed. The resistance increasing type sensor 1 is manufactured through the above steps.

[Movement of resistance increasing sensor]
Next, the movement of the resistance increasing sensor 1 of the present embodiment will be described. FIG. 8 is a cross-sectional view (corresponding to the VI-VI cross section of FIG. 5) as seen from below the resistance increasing type sensor before the collision of the collision object. FIG. 9 is a cross-sectional view of the resistance increasing type sensor viewed from below after the collision of the collision object.

  As shown in FIGS. 8 and 9, the resistance increasing sensor 1 is installed on the rear surface 900 of the bumper cover 90 of the automobile. The restraint plate 20 is attached to the rear surface 900. When the colliding object O collides with the bumper cover 90 from the front, the bumper cover 90 is deformed so as to sink backward. The deformation of the bumper cover 90 is transmitted to the resistance increasing type sensor 1. That is, the deformation of the bumper cover 90 is transmitted to the sensor main body 21 and the cover film 25 through the restraint plate 20. By transmitting the deformation, the sensor main body 21 is curved so as to protrude rearward together with the restraining plate 20 and the cover film 25.

  In the pre-collision state (non-deformed state) shown in FIG. 8, a large number of conductive paths are formed in the sensor body 21 due to the contact between the carbon beads. Therefore, the electrical resistance of the sensor body 21 is relatively small. On the other hand, in the post-collision state (deformed state) shown in FIG. 9, the sensor body 21 is bent at the initial stage of the collision, so that a crack in the sensor body 21 is opened. For this reason, the conductive path is cut. In addition, the conductive path is cut by changing the contact state between the conductive fillers. Thereby, the detected electrical resistance becomes larger than the state before the collision. Therefore, the bending deformation of the sensor main body 21, that is, the bumper cover 90, can be detected from the output electric resistance. In addition, the calculation device can calculate the collision load.

[Function and effect]
Next, the effect of the resistance increasing type sensor 1 of this embodiment will be described. The sensor main body 21 includes five detection units 210 to 214. Each of the detection units 210 to 214 extends in the left-right direction. The detection units 210 to 214 are arranged in the vertical direction. According to the resistance increasing sensor 1 of the present embodiment, as compared with a resistance increasing sensor having a single detection unit extending in the left-right direction, variation in electrical resistance is reduced when the total area of the detection unit is equal. be able to.

  Further, according to the resistance increasing sensor 1 of the present embodiment, the detection units 210 to 214 are electrically connected to each other in parallel between the electrode 22a and the electrode 22b. In the case of parallel connection, if the electrical resistances of the detection units 210 to 214 are Ra, Rb, Rc, Rd, Re, and the combined electrical resistance is R, 1 / R = 1 / Ra + 1 / Rb + 1 / Rc + 1 / Rd + 1 / Re. . For this reason, even if the electric resistances of the arbitrary detection units 210 to 214 vary, variations in the sensor body 21 as a whole can be reduced. Therefore, variation in the combined electrical resistance R can be reduced. Further, according to the resistance increasing sensor 1 of the present embodiment, since the detection units 210 to 214 are connected in parallel, the combined electrical resistance R is unlikely to increase even if the number of the detection units 210 to 214 is increased.

  Further, according to the resistance increasing sensor 1 of the present embodiment, the filling rate of the carbon beads is about 45% by volume when the volume of the sensor body 21 is 100% by volume. For this reason, in the undeformed state, a three-dimensional conductive path is formed in the sensor main body 21 by contact between the carbon beads. That is, the sensor main body 21 has high conductivity in an undeformed state.

  In addition, a crack C1 is formed in the sensor body 21 in advance. When the sensor body 21 is extended in the left-right direction by bending deformation, the crack C1 is opened. Thereby, the contact between the carbon beads is cut off, and the conductive path is cut. As a result, the electrical resistance increases.

  As described above, in the sensor main body 21 of the resistance increasing sensor 1 of the present embodiment, when strain is input due to bending deformation, the conductive path is cut without waiting for elastic deformation of the base material. Therefore, response delay is unlikely to occur.

  In addition, since the conductive path is cut mainly by the opening of the crack C1, it is possible to detect even a small distortion with higher accuracy than in the case where the conductive path is cut only depending on the elastic deformation of the base material. .

  The speed of elastic deformation of the base material is affected by the ambient temperature. In this regard, the conductive path of the resistance increasing type sensor 1 of the present embodiment is cut mainly by the opening of the crack C1. For this reason, the dependence of the response speed on the ambient temperature is small as compared with the case where the conductive path is cut only depending on the elastic deformation of the base material.

  The sensor body 21 is covered with a cover film 25. Thereby, deterioration of the sensor main body 21 is suppressed. The cover film 25 can be elastically deformed. Therefore, when unloaded after bending deformation, the sensor main body 21 is easily restored to the original shape, assisted by the elastic restoring force of the cover film 25. Further, the opened crack C1 is also likely to return to the original state.

  The sensor body 21 is disposed on the rear surface of the restraint plate 20. By adjusting the thickness of the restraint plate 20, the sensitivity of the resistance increasing sensor 1 can be adjusted. For example, as shown in FIG. 9, when the center of curvature at the time of bending deformation is on the front side of the constraining plate, increasing the thickness of the constraining plate 20 increases the amount of distortion of the sensor body 21 during bending deformation. That is, as shown in FIG. 9, when the total thickness of the restraint plate 20 and the sensor body 21 is t, and the radius of curvature from the center of curvature during bending deformation to the front surface of the restraint plate 20 is R, the strain amount ε is ε = T / R. For this reason, when the thickness of the restraint plate 20 is increased, the amount of distortion of the sensor body 21 during bending deformation increases. Thereby, the sensitivity of the resistance increasing sensor 1 can be improved.

  The sensor main body 21 is previously formed with a crack C1 at the time of manufacture. For this reason, it is difficult to form a new crack C1 during bending deformation. Therefore, the sensitivity of the resistance increasing type sensor 1 is hardly changed.

  Further, according to the resistance increasing sensor 1 of the present embodiment, the sensor body 21 includes the five detection units 210 to 214. Each of the five detection units 210 to 214 extends in the left-right direction. The five detection units 210 to 214 are arranged in the vertical direction. For this reason, when the total area of a detection part is equal compared with the resistance increase type sensor which has the single detection part extended in the left-right direction, the vertical direction width | variety of the detection parts 210-214 can be made small. Therefore, the density of the crack C1 can be increased. That is, variation in electrical resistance can be reduced. In addition, the sensitivity of the resistance increasing sensor 1 can be improved.

  The average particle diameter of the carbon beads is about 5 μm. For this reason, it becomes easy to form the crack C1 along the interface of carbon beads. Further, the crack C1 is easily opened at the interface of the carbon beads, and the breaking strain of the sensor body 21 can be reduced. In addition, the number of conductive paths in an undeformed state is unlikely to decrease. Further, the contact state of the carbon beads tends to change with respect to bending deformation. In addition, the thickness of the sensor main body 21 can be easily reduced.

  Carbon beads are spherical. For this reason, carbon beads are blended in the base material in a state close to closest packing. Therefore, a three-dimensional conductive path is easily formed, and desired conductivity is easily developed. Further, the contact state of the carbon beads tends to change with respect to the elastic deformation of the sensor body 21. For this reason, the change of electrical resistance becomes large. Carbon beads have few functional groups on the surface. For this reason, breakage is likely to occur at the interface with the base material, and the crack C <b> 1 is likely to be formed in the sensor body 21.

  Further, according to the resistance increasing type sensor 1 of the present embodiment, as shown in FIG. 7, about two cracks C <b> 1 are formed in the unit section U <b> 1 having a length of 2 mm that is continuous in the left-right direction of the sensor body 21. Yes. For this reason, the sensitivity of the resistance increasing sensor 1 is high.

<Second embodiment>
The difference between the resistance increasing sensor of this embodiment and the resistance increasing sensor of the first embodiment is that the sensor body extends in a zigzag shape between the two electrodes. Here, only differences will be described.

  FIG. 10 shows a front view of the resistance increasing type sensor of the present embodiment. For convenience of explanation, the cover film is removed and shown. In addition, about the site | part corresponding to FIG. 5, it shows with the same code | symbol. As shown in FIG. 10, the electrode 22 a is disposed at the upper left corner of the restraint plate 20. The electrode 22b is disposed at the lower right corner of the restraining plate 20. The sensor body 21 connects the electrodes 22a and 22b in a zigzag manner. The sensor main body 21 includes five detection units 210 to 214. Each of the detection units 210 to 214 has a strip shape extending in the left-right direction. The detection units 210 to 214 are juxtaposed in the vertical direction. The right end of the detection unit 210 and the right end of the detection unit 211, the left end of the detection unit 211 and the left end of the detection unit 212, the right end of the detection unit 212 and the right end of the detection unit 213, the left end of the detection unit 213 and the left end of the detection unit 214 are respectively It is connected. That is, the detection units 210 to 214 are connected in series.

  The resistance increasing type sensor 1 of the present embodiment has the same effects as the resistance increasing type sensor of the first embodiment with respect to the parts having the same configuration. According to the resistance increasing sensor 1 of the present embodiment, the detection units 210 to 214 are electrically connected in series with each other between the electrode 22a and the electrode 22b. In the case of series connection, if the electrical resistances of the detection units 210 to 214 are Ra, Rb, Rc, Rd, Re, and the combined electrical resistance is R, R = Ra + Rb + Rc + Rd + Re. For this reason, even if the electric resistances of the arbitrary detection units 210 to 214 vary, variations in the sensor body 21 as a whole can be reduced. Therefore, variation in the combined electrical resistance R can be reduced.

  Moreover, according to the resistance increasing type sensor 1 of this embodiment, the five detection parts 210-214 are connected in series like one-stroke writing. For this reason, even if the number of arrangement | positioning of the detection parts 210-214 is increased, it is not necessary to change the structure of the connection part of the sensor main body 21 and electrode 22a, 22b.

<Third embodiment>
The difference between the resistance increasing sensor of the present embodiment and the resistance increasing sensor of the first embodiment is that strain is input in advance to the sensor body. Here, only differences will be described. The manufacturing method of the resistance increase type sensor of this embodiment has a coating-material preparation process, a printing process, a bending hardening process, an unloading process, and a cover film printing process.

  In the paint preparation process, as in the first embodiment, a sensor paint, an electrode paint, a wiring paint, a connector paint, and a cover film paint are prepared. In the printing process, as in the first embodiment, a paint other than the cover film paint is printed on the surface of the restraint plate.

  In the bending hardening process, first, the restraint plate 20 is bent so that the coating film of the sensor paint is on the inside. Next, the coating film is cured by heating in that state. In FIG. 11, the schematic diagram of the first half of a bending hardening process is shown. FIG. 12 shows a schematic diagram of the latter half of the process.

  First, as shown in FIGS. 11 and 12, the constraining plate 20 on which the coating film 30 of the sensor paint is formed is attached to the mold surface (inner peripheral surface) 310 of the C-shaped crack forming mold 31. At this time, the front surface 200 of the restraining plate 20 is brought into contact with the mold surface 310 of the crack forming mold 31. Next, the crack forming mold 31 is placed in a drying furnace and held at about 140 ° C. for 1 hour to primarily cure the coating film 30. Subsequently, the coating film 30 is second-cured by holding at about 170 ° C. for 2 hours.

  In the unloading step, first, the restraint plate 20 is peeled from the crack forming die 31 together with the cured coating film 30. Then, the restraint plate 20 and the cured coating film 30 are returned from the curved state to the original planar state (see FIG. 11 above). Through this step, strain is input and cracks are formed in the cured coating film 30 (sensor body 21). In this way, the sensor body 21 is formed.

  In the cover film printing step, the cover film paint is printed as in the first embodiment. The resistance increasing type sensor 1 is manufactured through the above steps.

  The resistance increasing type sensor of this embodiment has the same effects as the resistance increasing type sensor of the first embodiment with respect to the parts having the same configuration. According to the resistance increasing type sensor 1 of the present embodiment, strain is input to the sensor body in advance. For this reason, the total strain amount at the time of bending deformation of the sensor body is the sum of the strain amount input in advance and the strain amount accompanying the bending deformation. That is, the total strain amount of the sensor main body is larger than the case of only the strain amount accompanying the bending deformation. Thereby, it becomes easy to use the area | region beyond the fracture | rupture distortion of a sensor main body as a detection area. That is, it becomes easy to shift the detection region to a region where the relationship between the strain amount and the electrical resistance is linear (distortion offset). Therefore, the sensitivity of the resistance increasing sensor is improved. Moreover, it becomes easy to calculate the amount of strain, and hence the shape of the sensor body during bending deformation, from the electrical resistance.

<Others>
The embodiment of the resistance increasing type sensor and the manufacturing method thereof according to the present invention has been described above. However, the embodiment is not particularly limited to the above embodiment. Various modifications and improvements that can be made by those skilled in the art are also possible.

  In the above embodiment, the number of strips of the sensor body (the number of detectors 210 to 214) is five. However, the number of strips is not particularly limited. It may be 10, 20 or the like. As the number of strips increases, the variation in the combined electrical resistance can be reduced. Moreover, the greater the number of strips, the greater the density of cracks. Also in this respect, the variation in the combined electric resistance can be reduced. In addition, the sensitivity of the resistance increasing sensor 1 can be improved.

  In the above embodiment, the electrodes 22a and 22b, the wirings 23a and 23b, the connector 24, and the sensor main body 21 are printed on the surface of the restraint plate 20. However, the method for forming these members is not particularly limited to the printing method. For example, a dipping method, a spray method, a bar coating method, or the like may be employed as a method of forming from a paint. Further, instead of the paint, the above members may be separately prepared and attached to the restraining plate 20. For example, the sensor body 21 press-molded with a mold may be attached to the restraining plate 20.

  In the above embodiment, in order to increase the density of the cracks C1, the vertical widths of the detection units 210 to 214 are reduced. However, the density of the cracks C1 may be increased by reducing the thickness in the front-rear direction of the detection units 210 to 214. Further, as shown in FIG. 3, the density of the cracks C1 may be increased by decreasing the radius of curvature of the mold surface 720 of the crack forming mold 72. In this way, a large number of cracks C1 can be formed. For this reason, the density of the crack C1 can be increased. Further, the density of the cracks C1 may be increased by reducing the thickness of the restraint plate 20 in the front-rear direction.

  The material of the cover film 25 is not particularly limited. Any insulating material may be used. Further, the cover film 25 may not be disposed. What is necessary is just to set suitably also about the number of electrodes 22a and 22b, and an arrangement place. For example, three or more electrodes 22a and 22b may be arranged at equal intervals, and the electrical resistance may be measured between a pair of adjacent electrodes 22a and 22b.

  The restraining plate 20 only needs to be able to restrain the elastic deformation of one surface of the sensor main body 21. In addition to the PI of the above embodiment, a resin film having flexibility such as polyethylene (PE), polyethylene terephthalate (PET), polyethylene naphthalate (PEN) is suitable. The thickness of the constraining plate 20 is desirably 10 μm or more and 500 μm or less, for example.

  The shape and size of the sensor body 21 are not particularly limited. What is necessary is just to determine these suitably according to the use of the resistance increase type sensor 1, etc. For example, the thickness of the sensor main body 21 is desirably 10 μm or more and 500 μm or less from the viewpoint of miniaturization and thinning of the resistance increasing sensor 1. 250 μm or less is more preferable. When the thickness of the sensor body 21 is reduced, the bending deformation inducing effect by the restraint plate 20 is easily exhibited.

  The base material of the sensor body 21 may be appropriately selected from resin and elastomer in consideration of compatibility with the conductive filler. In particular, when the sensor body 21 is formed from sensor paint, it is desirable to select a material that can be made into paint. That is, it is preferable to select a material that is liquid or a material that is soluble in a solvent.

  For example, as a thermoplastic resin, PE, polypropylene (PP), polyvinyl chloride (PVC), polystyrene (PS), polyvinyl acetate (PVAc), polytetrafluoroethylene (PTFE), acrylonitrile-butadiene-styrene (ABS) resin, Acrylic resin, polyamide (PA), polyacetal (POM), polycarbonate (PC), polyphenylene oxide (PPO), PET, polybutylene terephthalate (PBT), amorphous fluororesin, amorphous polyester resin, phenoxy resin, etc. It is done. Among these, polyamide, amorphous fluororesin, amorphous polyester resin, phenoxy resin, and the like are preferable because they are soluble in a solvent.

  Examples of the thermosetting resin include epoxy resin, alkyd resin, phenol resin, urea resin, melamine resin, unsaturated polyester resin, polyurethane, and PI. Of these, epoxy resins are preferred. The epoxy resin before curing is often a liquid having a relatively low viscosity. Therefore, it can be made into a paint without using a solvent. In addition, the compatibility with the conductive filler is also good. For this reason, it is easy to mix | blend an electroconductive filler with a high filling rate in a substantially single particle state. Examples of the epoxy resin include bisphenol type epoxy resins (A type, F type, AD type), alicyclic epoxy resins, novolac type epoxy resins, polyglycidyl ethers obtained by reacting polyhydric alcohols with epichlorohydrin, and the like. It is done.

  The elastomer can be appropriately selected from rubber and thermoplastic elastomer. For example, as rubber, natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), acrylonitrile-butadiene copolymer rubber (NBR), styrene-butadiene copolymer rubber (SBR), ethylene-propylene copolymer rubber [Ethylene-propylene copolymer (EPM), ethylene-propylene-diene terpolymer (EPDM), etc.], butyl rubber (IIR), halogenated butyl rubber (Cl-IIR, Br-IIR, etc.), hydrogenated nitrile rubber (H-NBR), chloroprene rubber (CR), acrylic rubber (AR), chlorosulfonated polyethylene rubber (CSM), hydrin rubber, silicone rubber, fluorine rubber, urethane rubber, synthetic latex and the like. Examples of the thermoplastic elastomer include various thermoplastic elastomers such as styrene, olefin, urethane, polyester, polyamide, and fluorine, and derivatives thereof. Of these, EPDM, NBR, and silicone rubber, which have good compatibility with the conductive filler, are preferable. Liquid IR, liquid BR, and RTV type (room temperature curable type) silicone rubber are suitable in that they are liquid before curing and can be made into a paint without using a solvent.

  The conductive filler is not particularly limited as long as it has conductivity. Examples thereof include fine particles such as carbon materials and metals. Of these, one can be used alone, or two or more can be used in combination. For example, the aspect ratio of the conductive filler (the ratio of the long side to the short side) is preferably in the range of 1 or more and 2 or less. This is because when the aspect ratio is larger than 2, a one-dimensional conductive path is easily formed by contact between the conductive fillers. In particular, from the viewpoint of bringing the filling state of the conductive filler in the base material closer to the close-packed filling state, it is advisable to adopt particles having a true sphere or a shape very close to a true sphere (substantially true sphere) as the conductive filler. .

  The filling rate of the conductive filler is preferably 30% by volume or more when the entire volume of the sensor body 21 is 100% by volume. When the amount is less than 30% by volume, the conductive filler is hardly compounded in a state close to the closest packing, and desired conductivity is hardly exhibited. In addition, the change in the electric resistance with respect to the elastic deformation of the sensor main body 21 becomes slow, and it becomes difficult to control the increase behavior of the electric resistance. It is more preferable that it is 35% by volume or more. On the other hand, the filling rate of the conductive filler is desirably 65% by volume or less when the entire volume of the sensor body 21 is 100% by volume. If it exceeds 65% by volume, the sensor main body 21 is difficult to elastically deform. Moreover, mixing with a base material becomes difficult, and molding processability falls. Furthermore, it becomes difficult to prepare the sensor paint. It is more preferable that it is 55 volume% or less.

  In the base material, it is desirable that the conductive filler is present in a primary particle state without being aggregated as much as possible. Therefore, when selecting the conductive filler, it is preferable to consider the average particle diameter, compatibility with the base material, and the like. For example, the average particle diameter of the conductive filler existing in the state of primary particles is desirably 0.05 μm or more and 100 μm or less. If it is less than 0.05 μm, it tends to aggregate and form secondary particles. It is preferable that the thickness is 0.5 μm or more, further 1 μm or more. On the other hand, when the average particle diameter exceeds 100 μm, the translational movement (parallel movement) of the conductive filler due to elastic deformation becomes relatively smaller than the particle diameter, and the change in electric resistance against elastic deformation becomes slow. Moreover, it becomes difficult to reduce the thickness of the sensor body 21. It is preferable that it is 60 μm or less, and further 30 μm or less.

  For example, carbon beads are suitable as the conductive filler. Carbon beads have good conductivity and are relatively inexpensive. Moreover, since it has a substantially spherical shape, it can be blended at a high filling rate. Specifically, Osaka Gas Chemical Co., Ltd. mesocarbon micro beads [MCMB6-28 (average particle size of about 6 μm), MCMB10-28 (average particle size of about 10 μm), MCMB25-28 (average particle size of about 25 μm)], Carbon micro beads manufactured by Nippon Carbon Co., Ltd .: Nika beads (registered trademark) ICB, Nika beads PC, Nika beads MC, Nika beads MSB [ICB 0320 (average particle size of about 3 μm), ICB 0520 (average particle size of about 5 μm), ICB 1020 (average particle size of about 10 μm) PC0720 (average particle size of about 7 μm), MC0520 (average particle size of about 5 μm)], Nisshinbo carbon beads (average particle size of about 10 μm), and the like.

  The sensor body 21 can be manufactured, for example, as follows. When a thermoplastic resin is selected as the base material, a heat-melted thermoplastic resin is mixed with a conductive filler and, if necessary, an additive, and then subjected to press molding, injection molding, or the like. When a thermosetting resin is selected as the base material, a curing agent and, if necessary, an additive are added to the pre-curing resin and mixed, and then cured by press molding or the like. On the other hand, when an elastomer is selected as the base material, first, additives such as a vulcanization aid and a softening agent are added to the elastomer and kneaded. Subsequently, after adding a conductive filler and kneading, a crosslinking agent and a vulcanization accelerator are further added and kneaded to obtain an elastomer composition. Next, the elastomer composition is formed into a sheet shape, filled in a mold, and press vulcanized.

  Further, in order to reduce the thickness of the sensor main body 21, it is desirable to form it from sensor paint. That is, first, a sensor paint containing a base material forming component such as resin or elastomer is prepared. Next, the prepared sensor paint is applied to a substrate such as the restraining plate 20 and dried. In addition, what is necessary is just to harden, after apply | coating a sensor coating material, when a thermosetting resin is used. When an elastomer is used, the crosslinking reaction may be advanced simultaneously with or after drying.

  Various methods can be adopted as a method of applying the sensor paint. For example, in addition to printing methods such as inkjet printing, flexographic printing, gravure printing, screen printing, pad printing, and lithography, dipping, spraying, bar coating, and the like can be given. For example, when a printing method is employed, it is possible to easily separate the applied part and the non-applied part. Also, printing of large areas, thin lines, and complicated shapes is easy. Furthermore, since the sensor body 21, the electrodes 22a and 22b, and the wirings 23a and 23b can be formed by the same method, it is easy to integrate the components. Among the printing methods, a high-viscosity paint can also be used, and the screen printing method is preferred because the coating thickness can be easily adjusted.

  Next, an electrical resistance measurement simulation performed on the resistance increasing sensor of the present invention will be described.

<Sample>
The samples of Examples 1 to 3 are resistance increasing sensors in which detection units are connected in parallel as in the resistance increasing sensor of the first embodiment (see FIG. 5). The samples of Examples 4 to 6 are resistance increasing sensors in which detection units are connected in series, similarly to the resistance increasing sensor (see FIG. 10) of the second embodiment. The sample of Reference Example 1 is a resistance increasing sensor having a single detection unit, similarly to the conventional resistance increasing sensor (see FIG. 16). However, a large number of cracks are formed in the sensor body of the resistance increasing sensor of Reference Example 1. For this reason, it is not publicly known. The total area of the detection part of the samples of Examples 1 to 6 and Reference Example 1 is constant. Further, unless otherwise specified below, the arrangement, shape, and material of the constituent members of each sample are constant. Hereinafter, the configuration of each sample will be described with reference to FIGS. 5 to 10 and FIG. 16.

[Example 1]
The configuration of the sample of Example 1 is the same as the configuration of the resistance increasing sensor of the first embodiment. That is, the restraint plate 20 is made of PI. The plate thickness is 300 μm. The detectors 210 to 214 are arranged in five stripes. The thickness of each of the detection units 210 to 214 is 100 μm. The widths in the short direction of the detection units 210 to 214 are each 1 mm. Each of the detection units 210 to 214 has a total length in the longitudinal direction of 50 mm.

  The sensor body 21 includes an epoxy resin and a large number of carbon beads. The filling rate of the carbon beads is about 45% by volume when the volume of the sensor body 21 is 100% by volume. A large number of cracks C1 are formed in the sensor body 21 in advance. About two cracks C <b> 1 are formed in the unit section U <b> 1 having a length of 2 mm that is continuous in the left-right direction of the sensor body 21. The cover film 25 is made of acrylic rubber and has a strip shape extending in the left-right direction.

[Example 2]
The second embodiment is different from the first embodiment in that the detection units 210 to 214 are arranged in 10 lines instead of 5 lines. Further, the widths in the short direction of the detection units 210 to 214 are different from each other in that the width is 0.5 mm instead of 1 mm. About the point other than these, it is the same.

[Example 3]
The third embodiment is different from the first embodiment in that the detection units 210 to 214 are arranged in 20 lines instead of 5 lines. Further, the widths in the short direction of the detection units 210 to 214 are different from each other in that the width is not 0.25 mm but 0.25 mm. About the point other than these, it is the same.

[Example 4]
The configuration of the sample of Example 4 is the same as the configuration of the resistance increasing sensor of the second embodiment. That is, the restraint plate 20 is made of PI. The plate thickness is 300 μm. The detectors 210 to 214 are arranged in five lines in a single stroke. The thickness of each of the detection units 210 to 214 is 100 μm. The widths in the short direction of the detection units 210 to 214 are each 1 mm. Each of the detection units 210 to 214 has a total length in the longitudinal direction of 50 mm.

  The sensor body 21 includes an epoxy resin and a large number of carbon beads. The filling rate of the carbon beads is about 45% by volume when the volume of the sensor body 21 is 100% by volume. A large number of cracks C1 are formed in the sensor body 21 in advance. About two cracks C <b> 1 are formed in the unit section U <b> 1 having a length of 2 mm that is continuous in the left-right direction of the sensor body 21. The cover film 25 is made of acrylic rubber and has a strip shape extending in the left-right direction.

[Example 5]
The fifth embodiment is different from the fourth embodiment in that the detection units 210 to 214 are arranged in ten lines instead of five. Further, the widths in the short direction of the detection units 210 to 214 are different from each other in that the width is 0.5 mm instead of 1 mm. About the point other than these, it is the same.

[Example 6]
The sixth embodiment is different from the fourth embodiment in that the detection units 210 to 214 are arranged in 20 lines instead of 5 lines. Further, the widths in the short direction of the detection units 210 to 214 are different from each other in that the width is not 0.25 mm but 0.25 mm. About the point other than these, it is the same.

[Reference Example 1]
The configuration of the sample of Reference Example 1 is the same as the configuration of the conventional resistance increasing sensor. That is, in Reference Example 1, a single detection unit (sensor body) 102 is arranged. The width of the detection unit 102 in the short direction is 5 mm.

<Simulation method>
For each sample, electrical resistance measurement simulation was performed by the Monte Carlo method. Assuming that the variation in the electrical resistance of the single detection units 210 to 214, 102 (the variation in the ± direction when the average value is 100%) is uniformly distributed in a range of ± 33.3%, the variation is included. The average value, standard deviation, maximum value, and minimum value of the combined resistance value of each sample were determined by 2000 trials.

<Simulation results>
Table 1 shows the simulation results.

  In Table 1, the range indicates the maximum value-minimum value. The coefficient of variation is the standard deviation / average value. FIG. 13 is a graph showing the relationship between the number of strips and the electrical resistance ratio when the detection units are connected in parallel. FIG. 14 is a graph showing the relationship between the number of strips and the electrical resistance ratio when the detection units are connected in series. FIG. 15 is a graph showing the relationship between the number of strips and the coefficient of variation when the detection units are connected in parallel and when connected in series. The average values, maximum values, and minimum values in Table 1, FIG. 13, and FIG. 14 are the electric resistance ratios (relative values) when the average value of the electric resistance of a single detection unit is 100%. is there.

  As shown in Table 1 and FIG. 13, in the case of parallel connection, the range and variation become smaller as the number of strips increases. The average value is substantially constant. As shown in Table 1 and FIG. 14, in the case of series connection, the electrical resistance ratio increases as the number of strips increases. This increases the range. However, the variation is reduced. As shown in Table 1 and FIG. 15, in the case of parallel connection, the variation coefficient decreases as the number of strips increases. Similarly, in the case of serial connection, the coefficient of variation decreases as the number of strips increases. That is, in the case of parallel connection and in the case of series connection, the relative variation decreases as the number of strips increases.

1: Increased resistance type sensor.
20: Restraint plate, 21: Sensor body, 22a: Electrode, 22b: Electrode, 23a: Wiring, 23b: Wiring, 24: Connector, 25: Cover film, 30: Coating film, 31: Mold for crack formation, 70: Detection part, 71: Restraint plate, 72: Mold for crack formation, 90: Bumper cover.
200: Front surface, 210-214: Detection unit, 310: Mold surface, 710: Lower surface, 720: Mold surface, 800: Sensor body, 801: Base material, 802: Conductive filler, 803: Crack, 900: Rear surface.
C1: Crack, O: Colliding object, U1: Unit section.

Claims (7)

A sensor body having a base material made of a resin or an elastomer, and a conductive filler filled in the base material, the electrical resistance increasing as the amount of bending deformation increases;
At least two electrodes connected to the sensor body and outputting an electrical quantity related to the electrical resistance;
A constraining plate that is laminated on one surface of the sensor body and restrains elastic deformation of the one surface;
A resistance increasing sensor comprising:
The direction in which the two electrodes are arranged is a juxtaposed direction, and the direction orthogonal to the juxtaposed direction is an orthogonal direction,
The sensor body has a plurality of detection units extending in the juxtaposed direction and arranged in the orthogonal direction,
In at least the base material of the sensor body, when the sensor body is bent and deformed, a crack is formed in advance so as to cut a conductive path formed by connecting a plurality of the conductive fillers ,
The resistance increasing sensor , wherein the crack is formed by deforming a precursor of the sensor body along a mold surface of a crack forming mold .   The resistance increasing sensor according to claim 1, wherein the plurality of detection units are electrically connected in parallel to each other between two adjacent electrodes.   The resistance increasing sensor according to claim 1, wherein the plurality of detection units are electrically connected in series between two adjacent electrodes. Further, the other surface of the sensor main body facing away from the one surface is covered with an elastically deformable cover film,
The base material is resin;
The resistance increasing type according to any one of claims 1 to 3, wherein the conductive filler is filled in the base material at a filling rate of 30% by volume or more with the volume of the sensor body being 100% by volume. Sensor. The resistance increasing sensor according to any one of claims 1 to 4, wherein strain is input to the sensor body in advance. The resistance increasing sensor according to any one of claims 1 to 5, wherein five or more detection units are arranged.   A sensor body having a base material made of a resin or an elastomer, and a conductive filler filled in the base material, the electrical resistance increasing as the amount of bending deformation increases;
  At least two electrodes connected to the sensor body and outputting an electrical quantity related to the electrical resistance;
  A constraining plate that is laminated on one surface of the sensor body and restrains elastic deformation of the one surface;
A method of manufacturing a resistance increasing sensor comprising:
  The direction in which the two electrodes are arranged is a juxtaposed direction, and the direction orthogonal to the juxtaposed direction is an orthogonal direction,
  The sensor body has a plurality of detection units extending in the juxtaposed direction and arranged in the orthogonal direction,
  By deforming the precursor of the sensor body along the mold surface of the crack forming mold, when the sensor body is bent and deformed, a conductive path formed by connecting the plurality of conductive fillers is cut. And a method of manufacturing a resistance increasing sensor, further comprising a crack forming step of forming a crack in the sensor body.

Images