JP2008102090A - Deformation sensor system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a deformation sensor system that can prevent restraining of a detectable external-force applied part and can reduce the number of members corresponding to an element for detecting the external force. <P>SOLUTION: This deformation sensor system comprises a sensor body 12 that is made of rubber elastic material whose electric resistance increases with increase in elastic deformation amount and has a predetermined region elastically deforming when the external force is received, a plurality of electrodes 13a-13h separately arranged so as to grip the predetermined region of the sensor body 12, and a detecting section 22 for detecting that the external force is received by the predetermined region based on the variation in electric resistance of the sensor body 12 by the external force between the electrodes 13a-13h when voltage is applied between the electrodes 13a-13h. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a deformation sensor system that can be used for, for example, a pressure-sensitive sensor.

  Conventional pressure-sensitive sensors include, for example, Japanese Utility Model Laid-Open No. 5-36331 (Patent Document 1), Japanese Patent Application Laid-Open No. 5-81977 (Patent Document 2), Japanese Patent Application Laid-Open No. 11-115678 (Patent Document 3), and the like. One disclosed in Japanese Laid-Open Patent Publication No. 2001-56259 (Patent Document 4).

  The pressure-sensitive sensors described in Patent Literature 1 and Patent Literature 2 have a configuration in which a pressure detection convex portion is formed on the surface of a pressure-sensitive conductive elastomer member, and an electrode is disposed on the back side thereof. This pressure-sensitive conductive elastomer is made of a material that exhibits insulation when no pressure is applied, and exhibits conductivity as the internal conductive particles approach each other when pressure is applied and the electrical resistance value gradually decreases. That is, when pressure is applied to the pressure detection convex portion, the distance between the front surface and the back surface is shortened, so that the pressure-sensitive conductive elastomer member exhibits conductivity. Then, the change from the insulating property to the conductive property is detected by the electrode on the back surface side, and the application of pressure is detected.

  Moreover, the pressure-sensitive sensor described in Patent Document 3 includes an upper pressure-sensitive ink and a lower pressure-sensitive ink, and the two are separated when no pressure is applied. The application of pressure is detected by changing the electrical resistance.

In addition, the pressure-sensitive sensor described in Patent Document 4 includes a lower film on which a wiring pattern is formed, and an upper film on which a pressure-sensitive resistor is formed so as to be arranged so as to overlap the lower film. It has. That is, when no pressure is applied, the wiring pattern and the pressure-sensitive resistor are separated from each other, so that they are not conducted. When the pressure is applied, the wiring pattern and the pressure-sensitive resistor are brought into contact with each other. Therefore, the application of pressure is detected based on the electrical signal generated by conduction.
Japanese Utility Model Publication No. 5-36331 Japanese Patent Laid-Open No. 5-81977 JP 11-115678 A JP 2001-56259 A

  However, in any conventional pressure-sensitive sensor, a member corresponding to a pressure detection element is disposed at a pressurization site. For example, in Patent Document 1 and Patent Document 2, an electrode (pressure detection element) that detects a change to conductivity is arranged on the back side of the pressurization site. In Patent Document 3, upper pressure-sensitive ink and lower pressure-sensitive ink corresponding to a pressure detection element are arranged at a pressurization site. Also in patent document 4, the contact site | part of the wiring pattern and pressure-sensitive resistance corresponded to a pressure detection element is arrange | positioned at the pressurization site | part.

  As described above, according to the configuration in which the pressure detection element is arranged at the pressurizing part, it is possible to detect the pressure applied to the part where the pressure detecting element is arranged, but it is possible to detect the pressure addition to the other part. It cannot be detected. In other words, the pressure application sites that can be detected are limited. For example, when a pressure-sensitive sensor that detects pressure application to all parts of a predetermined surface is configured, it is necessary to arrange a large number of pressure detection elements at all parts of the surface. Even if a large number of electrodes are arranged in all the parts of the surface in this way, the parts of pressure application that can still be detected are limited when viewed in smaller units. Therefore, in the conventional configuration, the pressure application site is limited. Even if it is possible to arrange a large number of pressure detection elements so as not to limit a portion where a certain amount of pressure is applied, in this case, a large number of pressure detection elements are required, resulting in an increase in cost.

  The present invention has been made in view of such circumstances, and is a deformation sensor that can limit the number of external force application sites that can be detected and can reduce the number of members that correspond to elements that detect external force. The purpose is to provide a system.

  Therefore, the present inventor has eagerly studied to solve this problem, and as a result of repeated trial and error, has come up with the idea of developing a new rubber elastic material and detecting a change in electric resistance of the rubber elastic material. It came to complete.

  That is, the deformation sensor system of the present invention is made of a rubber elastic material whose electric resistance increases as the amount of elastic deformation increases, and includes a sensor body having a predetermined area that elastically deforms when receiving an external force, and a predetermined area of the sensor body. When a voltage is applied between the plurality of electrodes that are spaced apart so as to sandwich the electrode, the external force is applied to the predetermined region based on the change in the electrical resistance of the sensor body due to the external force between the electrodes. And a detecting unit for detecting.

  First, the reason why the deformation sensor system of the present invention can detect that the sensor body has received a predetermined external force when receiving an external force will be described.

  As described above, the sensor body in the present invention is made of a rubber elastic material whose electric resistance increases as the amount of elastic deformation increases. That is, this rubber elastic material has the smallest electric resistance when not deformed, and the electric resistance becomes large when deformed. Therefore, when a constant voltage is applied to the rubber elastic material, the largest current flows when there is no deformation, and the current value decreases according to the deformation.

  That is, the state where the external force is not applied to the predetermined region of the sensor body (hereinafter referred to as “no load state”) has the smallest electrical resistance between the electrodes. Therefore, when a voltage is applied between the electrodes in this no-load state, the current flows most easily between the electrodes. Thus, current flows between the electrodes in a no-load state. On the other hand, when an external force is applied to a predetermined area of the sensor body (hereinafter referred to as “load state”), the predetermined area of the sensor body is elastically deformed by the external force, and as a result, the electrical resistance of the predetermined area of the sensor body is large. Become. Furthermore, even if the amount of change in the electrical resistance varies depending on the position where the external force is received, the electrical resistance between the electrodes always increases as a result of receiving the external force. Then, when the applied voltage is constant, the current flowing between the electrodes is reduced by receiving an external force.

  Here, when a voltage is applied between the electrodes, the detection unit detects a change in the electrical resistance of the sensor main body due to an external force between the electrodes. For example, the detection unit detects a current flowing between the electrodes when a voltage is applied between the electrodes. In this case, the detection unit detects the maximum current in the no-load state, and detects a smaller current in the load state. Therefore, regardless of the position where the external force is received, the detection unit can reliably detect a change in electrical resistance between the electrodes.

  Thus, the electrical resistance between the electrodes changes when a predetermined region of the sensor body receives an external force. Furthermore, since a change in electrical resistance between the electrodes can be detected, it can be reliably detected that an external force has been applied to a predetermined region of the sensor body. In other words, even if an external force is received at any position within a predetermined region of the sensor body, it can be detected that the external force has been received. Thus, according to the deformation | transformation sensor system of this invention, it can avoid limiting the external force addition site | part which can be detected.

  Furthermore, depending on the size of the predetermined region, if there are at least two electrodes, it can be detected that an external force has been applied. Even if the area for receiving the external force is enlarged, it is only necessary to arrange the electrodes so that the predetermined area is interposed therebetween, so that the number of electrodes in the present invention is greatly reduced compared to the number of conventional pressure detection elements. be able to.

  By the way, as a conventional rubber elastic material, for example, Patent Document 1 and Patent Document 2 disclose pressure-sensitive conductive elastomers. This pressure-sensitive conductive elastomer is made of a material that exhibits insulation in a no-load state and exhibits conductivity as the internal conductive particles approach each other and the electrical resistance value gradually decreases in the loaded state. . Whether a known elastomer having such properties can be applied to the sensor body of the present invention will be examined.

  If a plurality of electrodes are arranged so as to sandwich a predetermined region that receives an external force in the elastomer, no current flows between the electrodes in a no-load state. This is because the elastomer between the electrodes exhibits insulating properties. And only when it deform | transforms by pressurization over the whole between electrodes, an electric current flows between electrodes. That is, when only a part between the electrodes is pressurized and deformed, no current flows between the electrodes. Therefore, when pressure is applied only to a part between the electrodes, it is impossible to detect pressure application. That is, a known elastomer cannot be applied to the sensor body of the present invention.

  Here, in the deformation sensor system of the present invention described above, a plurality of electrodes are used. In particular, the number of electrodes may be three or more, and the detection unit may detect a position that receives an external force based on a change in electrical resistance. By using three or more electrodes, a plurality of paths can be formed as paths between the electrodes. That is, the detection unit can detect a change in electrical resistance between the electrodes of the plurality of paths. And the influence on the change of the electrical resistance in each between the electrodes of a some path | route changes with the position which received external force. Based on this degree of influence, the position where the external force is received can be detected.

  Thus, in the case of detecting the position of the external force, the electrodes are preferably set as follows. That is, the electrode has a first direction electrode group including a plurality of first direction electrode pairs arranged on a predetermined surface so as to sandwich a predetermined region in a predetermined first direction, and on the predetermined surface, And a second direction electrode group including a plurality of second direction electrode pairs arranged so as to sandwich a predetermined region in a second direction orthogonal to the first direction. That is, the path between the electrodes in the first direction electrode group and the path between the electrodes in the second direction electrode group are arranged to be orthogonal to each other. Thus, by forming a path between a plurality of electrodes in two orthogonal directions, that is, by forming a path between the electrodes in a matrix, the position of the external force can be easily detected.

  Furthermore, as described above, when the number of electrodes is three or more, the detection unit may detect the position of the external force and the magnitude of the external force at the position based on the change in electrical resistance. By setting the number of electrodes to 3 or more, as described above, a plurality of paths can be formed as paths between the electrodes. That is, the detection unit can detect a change in electrical resistance between the electrodes of the plurality of paths. And the influence on the change of the electrical resistance in each between the electrodes of a some path | route changes with the position which received external force.

  Furthermore, even if the magnitude of the external force is the same, if the position where the external force is received is different, the influence on the change in electrical resistance between the electrodes of the plurality of paths is different. However, the relationship between the magnitude of the external force and the position of the external force is a unique relationship. Specifically, the farther the distance from the electrode, the smaller the effect on the change in electrical resistance due to the magnitude of the external force, and the closer the distance from the electrode, the effect on the change in electrical resistance due to the magnitude of the external force. Becomes larger. Thus, based on the relationship between the position of the electrode and the position that receives the external force, the magnitude of the external force at that position can determine the degree of influence on the change in electrical resistance. Based on the degree of influence, the detection unit can detect the position where the external force is received and the magnitude of the external force at that position.

  As described above, when detecting the position of the external force and the magnitude of the external force at the position, the detection unit may be configured as follows. That is, the detection unit calculates the magnitude of the external force at each position on the predetermined surface based on the coefficient storage unit that stores the coefficient according to the position on the predetermined surface in the predetermined region and the change in the coefficient and the electric resistance. And an external force calculating unit.

  That is, the degree of influence of the magnitude of the external force at the position determined based on the relationship between the position of the electrode and the position receiving the external force on the change in electrical resistance corresponds to the coefficient stored in the coefficient storage unit. This coefficient corresponds to the relationship between the position of the electrode and the position where the external force is received, that is, two separation distances that can be grasped in advance. That is, a coefficient corresponding to this influence degree is determined and stored in advance. Then, in addition to the actual change in electrical resistance between the electrodes, the external force at the position actually received can be calculated by correcting with a coefficient corresponding to the position.

  In particular, the external force calculation unit includes a coefficient at a predetermined position on a predetermined surface, between virtual first direction electrode pairs arranged so as to pass through a predetermined position on the predetermined surface and sandwich a predetermined region in a predetermined first direction. Changes in electrical resistance, and changes in electrical resistance between virtual second direction electrode pairs arranged so as to sandwich a predetermined region in a second direction orthogonal to the first direction through a predetermined position on a predetermined surface Based on this, the magnitude of the external force at the position on the predetermined surface may be calculated.

  More specifically, the coefficient storage unit stores a first coefficient related to the first direction corresponding to the position on the predetermined surface and a second coefficient related to the second direction corresponding to the position on the predetermined surface, and the external force calculation unit The magnitude of the external force may be calculated according to equation (1).

  By doing in this way, the external force in the said position can be calculated reliably and easily.

  Further, the external force calculation unit determines the magnitude of the external force at a position on the predetermined plane based on the coefficient, the change in electrical resistance between the virtual first direction electrode pair, and the change in electrical resistance between the virtual second direction electrode pair. When calculating, it is better to do as follows. That is, the electrode has a first direction electrode group including a plurality of first direction electrode pairs arranged on a predetermined surface so as to sandwich a predetermined region in a predetermined first direction, and on the predetermined surface, And a second direction electrode group including a plurality of second direction electrode pairs arranged so as to sandwich a predetermined region in a second direction orthogonal to the first direction. Further, the external force calculation unit calculates the change in electrical resistance between the virtual first direction electrode pairs based on the change in electrical resistance of the adjacent first direction electrode pairs positioned so as to sandwich the predetermined position, The change in the electrical resistance between the directional electrode pairs is calculated based on the change in the electrical resistance of the adjacent second directional electrode pairs located so as to sandwich the predetermined position.

  Here, the change in the electrical resistance between the virtual first direction electrode pair passing through the predetermined position is related to the change in the electrical resistance of the adjacent first direction electrode pair located so as to sandwich the predetermined position, and the interpolation relation is Have. That is, the external force calculation unit interpolates the change in electrical resistance between the virtual first direction electrode pairs passing through the predetermined position based on the change in the electrical resistance of the adjacent first direction electrode pairs located so as to sandwich the predetermined position. Can be calculated. In addition, the change in electrical resistance between the virtual second direction electrode pairs passing through a predetermined position is related to the change in the electrical resistance of adjacent second direction electrode pairs positioned so as to sandwich the predetermined position, and has an interpolation relationship. is doing. That is, the external force calculation unit interpolates the change in electrical resistance between the virtual second direction electrode pairs passing through the predetermined position based on the change in the electrical resistance of the adjacent second direction electrode pair positioned so as to sandwich the predetermined position. Can be calculated.

  That is, by arranging the first direction electrode pair and the second direction electrode pair at appropriate intervals, the magnitude of the external force between them can be calculated.

  Here, in the above description, the magnitude of the external force at an arbitrary position on the predetermined surface can be calculated. However, it may be sufficient to calculate the magnitude of the external force at a specific position instead of an arbitrary position. In such a case, the following may be performed.

  That is, the electrode has a first direction electrode group including a plurality of first direction electrode pairs arranged on a predetermined surface so as to sandwich a predetermined region in a predetermined first direction, and on the predetermined surface, And a second direction electrode group including a plurality of second direction electrode pairs arranged so as to sandwich a predetermined region in a second direction orthogonal to the first direction. The coefficient storage unit stores the coefficient at the intersection of the line segment connecting each first direction electrode pair and the line segment connecting each second direction electrode pair. Further, the external force calculation unit includes a coefficient at each intersection, a change in electrical resistance between the first direction electrode pairs passing through each intersection, and a change in electrical resistance between the second direction electrode pairs passing through each intersection. Based on the above, the magnitude of the external force at each intersection is calculated.

  Thereby, the magnitude of the external force only at the intersection of the line segment connecting the first direction electrode pairs and the line segment connecting the second direction electrode pairs can be calculated reliably and easily. Specifically, it is very easy to set the coefficient and calculate the magnitude of the external force.

  When the rubber elastic material of the sensor main body is an elastomer having a predetermined rubber and a spherical conductive filler blended in a substantially single particle state and with a high filling rate in the elastomer. Good. Here, the “substantially single particle state” means that 50% by mass or more when the total mass of the conductive filler is 100% by mass exists not as aggregated secondary particles but as single primary particles. That means. In addition, “mixed at a high filling rate” means that the conductive filler is blended in a close-packed state.

  In this way, the conductive filler is blended at a high filling rate (close to the most dense state), and is present in the state of primary particles in the elastomer, so that the sensor body is conductive when no pressure is applied. A three-dimensional conductive path is formed by the filler. On the other hand, at the time of pressurization to the sensor body, the sensor body is elastically deformed. And since the conductive filler is mix | blended in the state close | similar to a close-packed state, conductive fillers repel each other by this elastic deformation, and the contact state of conductive fillers changes. As a result, the three-dimensional conductive path when no pressure is applied collapses and the electrical resistance increases. That is, the rubber elastic material can have a property that electric resistance increases as the amount of elastic deformation increases.

  According to the deformation sensor system of the present invention, it is possible to detect that an external force has been received regardless of the position of the sensor body that is in a predetermined region. That is, it is possible not to limit the external force application site that can be detected. Furthermore, according to the modified sensor system of the present invention, the number of electrodes in the present invention is greatly increased compared to the number of conventional pressure detection elements and the like because the electrodes need only be arranged so as to intervene a predetermined region of the sensor body. Can be reduced to

  Next, the present invention will be described in more detail with reference to embodiments.

(1) Overall Configuration of Deformation Sensor System The overall configuration of the deformation sensor system of this embodiment will be described with reference to FIGS. 1 and 2. FIG. 1 is an overall configuration diagram of a deformation sensor system. Fig.2 (a) shows the AA sectional drawing of FIG. 1 in the state (no-load state) in which the sensor main body 12 is not receiving pressing external force. FIG. 2B is a cross-sectional view taken along line AA of FIG. 1 in a state where the sensor body 12 receives a pressing external force (load state).

  As shown in FIG. 1, the deformation sensor system includes a sensor structure 10, a control unit 20, and a monitor 30. Here, the deformation sensor system of the present invention includes the sensor structure 10 and the detection unit 22 of the control unit 20.

  The sensor structure 10 includes a mounting plate 11, a sensor main body 12, a plurality of electrode pairs 13 a to 13 h, a connector 14, and wiring 15. As shown in FIGS. 1 and 2 (a) and 2 (b), the mounting plate 11 has a rectangular flat plate shape, and is made of a resilient foaming material or a cushioning material. That is, as shown in FIG. 2B, when the upper surface (the upper side surface of FIG. 2) of the mounting plate 11 is pressed, the pressing portion is deformed into a concave shape. For example, the mounting plate 11 is disposed on a flat base.

The sensor body 12 is made of a rubber elastic material whose electrical resistance increases as the amount of elastic deformation increases. The sensor body 12 is formed in a rectangular shape, particularly a square plate shape in the present embodiment. Further, the sensor main body 12 has a square shape smaller than the mounting plate 11. And the sensor main body 12 is arrange | positioned so that it may overlap with the mounting board 11 in the center part among the upper surfaces of the mounting board 11. FIG.
Here, the upper surface of the sensor body 12, that is, the flat spreading surface forms a force receiving surface 12 a that can receive a pressing external force downward in FIGS. 2 (a) and 2 (b). That is, when the force receiving surface 12a of the sensor main body 12 receives a pressing external force in the normal direction of the force receiving surface 12a, as shown in FIG. Bending elastically deforms so that the part curves toward the lower side of FIG. In other words, when the force receiving surface 12a receives a pressing external force, the sensor body 12 as a whole can be bent and elastically deformed (corresponding to a predetermined region in the present invention). The details of the rubber elastic material of the sensor main body 12 will be described in the item of “(2) Material description of the sensor main body 12” described later.

  The electrode pairs 13a to 13h are a plurality of electrodes fixed in contact with the sensor body 12 at the periphery of the sensor body 12 (that is, the periphery of the force receiving surface 12a), and are spaced apart from each other. It consists of a pair of electrodes. Specifically, each of the electrode pairs 13a to 13h has an end connected to the peripheral edge of the force receiving surface 12a, and extends outward from a connection point to the peripheral edge of the force receiving surface 12a. Is arranged). Furthermore, the electrode pairs 13a to 13h are arranged so as not to overlap the force receiving surface 12a when viewed from the direction of the pressing external force received by the sensor body 12.

  That is, all these electrodes are not arranged in a region of the sensor body 12 that undergoes bending elastic deformation when the force receiving surface 12a of the sensor body 12 receives a pressing external force. Therefore, even when the force receiving surface 12a of the sensor body 12 receives a pressing external force, these electrodes do not receive the pressing external force directly.

  These electrode pairs 13a to 13h are specifically composed of four electrode pairs (eight electrodes) arranged to face each other with the sensor body 12 sandwiched in the Y direction (vertical direction in FIG. 1). The first direction electrode group includes a second direction electrode group including four electrode pairs (eight electrodes) disposed to face each other with the sensor main body 12 interposed therebetween in the X direction (left and right direction in FIG. 1). Note that the X direction and the Y direction are directions orthogonal to each other. The four electrode pairs constituting the first direction electrode group are a first electrode pair 13a, a second electrode pair 13b, a third electrode pair 13c, and a fourth electrode pair 13d. And these electrode pairs 13a-13d are arrange | positioned at equal intervals in order toward the right side from the left side of FIG. Further, the four electrode pairs constituting the second direction electrode group are a fifth electrode pair 13e, a sixth electrode pair 13f, a seventh electrode pair 13g, and an eighth electrode pair 13h. And these electrode pairs 13e-13h are arrange | positioned at equal intervals in order toward the lower side from the upper side of FIG.

  The connector 14 is a member for electrical connection with the control unit 20 described later. This connector 14 is disposed at the lower left corner of FIG. 1 on the upper surface of the mounting plate 11 and outside the peripheral edge of the sensor body 12. That is, the connector 14 is disposed at a position separated from the sensor body 12.

  The wiring 15 has one end connected to each electrode constituting the electrode pairs 13 a to 13 h and the other end connected to the connector 14. Each wiring 15 is disposed on the upper surface of the mounting plate 11 and outside the peripheral edge of the sensor main body 12. That is, the wiring 15 is not disposed in a region of the sensor body 12 that undergoes bending elastic deformation when the force receiving surface 12a of the sensor body 12 receives a pressing external force, like the electrodes. Therefore, even when the force receiving surface 12a of the sensor body 12 receives a pressing external force, the wiring 15 does not receive the pressing external force directly.

The control unit 20 includes a power supply circuit 21, a detection unit 22, and an output unit 23. The power supply circuit 21 is electrically connected to the respective electrode pairs 13a to 13h and a resistance change amount detection unit 22a of the detection unit 22 described later via the connector 14 and the wiring 15, and applies the DC voltage Vin. Circuit.
The detection unit 22 detects the electrical resistance of the sensor body 12 between the respective electrode pairs 13a to 13h, and calculates the magnitude of the pressing external force received by the force receiving surface 12a of the sensor body 12 based on the detected electrical resistance. To do. The output unit 23 displays on the monitor 30 based on the pressing external force at an arbitrary position of the force receiving surface 12a calculated by the detection unit 22. That is, a surface corresponding to the force receiving surface 12a of the sensor body 12 is displayed on the monitor 30, and a part that has received the pressing external force is displayed using various colors or displayed using light and dark colors. Or Details of the control unit 20 will be described in an item “(4) Detailed description of the control unit 20” described later.

(2) Material Description of Sensor Main Body 12 Next, a rubber elastic material used for the sensor main body 12, that is, a rubber elastic material having a property that electric resistance increases as the amount of elastic deformation increases, will be described in detail with reference to FIG. explain. FIG. 3A shows a schematic cross-sectional view of the sensor main body 12 in a no-load state, and FIG. 3B shows a schematic cross-sectional view of the sensor main body 12 in a loaded state. In addition, in FIG.3 (b), the shape of the sensor main body 12 of a no-load state is shown with a broken line.

  The rubber elastic material of the sensor main body 12 includes an elastomer 12b made of a predetermined rubber and a spherical conductive filler 12c blended in a substantially single particle state with a high filling rate in the elastomer. is there. Here, the elastomer 12b itself made of a predetermined rubber has an insulating property. Further, “substantially single particle state” and “compounding at a high filling rate” have the above-mentioned meanings.

  And in a no-load state, as shown to Fig.3 (a), many of the conductive fillers 12c exist in the primary particle state in the elastomer 12b. Moreover, the filling rate of the conductive filler 12c is high and is blended in the most dense state. Thereby, in the no-load state, the sensor body 12 is formed with a three-dimensional conductive path Ps by the conductive filler 12c. Therefore, in the no-load state, the electrical resistance of the sensor body 12 is reduced.

  On the other hand, as shown in FIG. 3B, when an external force (for example, a pressing external force) is applied to the force receiving surface 12a of the sensor body 12, the sensor body 12 is elastically deformed. Here, since the conductive filler 12c is blended in a state close to the most dense state, there is almost no space where the conductive filler 12c can move. Therefore, when the sensor body 12 is elastically deformed, the conductive fillers 12c repel each other, and the contact state between the conductive fillers 12c changes. As a result, the three-dimensional conductive path Ps formed in the no-load state collapses, and the electrical resistance of the sensor body 12 increases.

  Here, in the sensor main body 12, as the blending amount of the conductive filler 12c is increased with respect to the elastomer 12b, the electric resistance of the sensor main body 12 decreases. Specifically, considering the case where the conductive filler 12c is blended with a predetermined amount of the elastomer 12b, the electric resistance of the sensor body 12 shows a large value when the blending amount of the conductive filler 12c is small. That is, the electrical resistance of the sensor body 12 in this case is almost equal to the electrical resistance of the elastomer 12b itself in a state where the conductive filler 12c is not blended.

  Then, when the blending amount of the conductive filler 12c is increased and the blending amount reaches a predetermined volume fraction, the electrical resistance of the sensor body 12 is rapidly reduced, and an insulator-conductor transition occurs (first). One change pole). The blending amount (volume%) of the conductive filler 12c at the first inflection point is called a critical volume fraction. Further, when the blending amount of the conductive filler 12c is further increased, the change amount of the electric resistance of the sensor body 12 is reduced from the predetermined volume fraction, and the change of the electric resistance is saturated (second inflection point). . The blending amount (volume%) of the conductive filler 12c at the second inflection point is referred to as a saturated volume fraction. Such a change in the electrical resistance of the sensor body 12 is called a percolation curve, and is considered to be due to the formation of a conductive path Ps (shown in FIG. 3A) by the conductive filler 12c in the elastomer 12b. . And in order to be able to form conductive path Ps appropriately in a no-load state, a saturation volume fraction shall be 35 volume% or more.

  From another viewpoint, when the volume of the entire sensor body 12 is 100% by volume, the filling rate of the conductive filler 12c is preferably 30% by volume to 65% by volume. Similarly in this case, since the conductive filler 12c exists in the state of primary particles and is blended in a state close to the most dense state, the conductive path Ps can be appropriately formed in a no-load state.

  A specific example of the rubber elastic material forming the sensor body 12 is given below. First, 85 parts by weight of oil exhibition EPDM (“Esprene (registered trademark) 6101” manufactured by Sumitomo Chemical Co., Ltd.), 34 parts by mass of oil exhibition EPDM (“Esplen 601” manufactured by Sumitomo Chemical Co., Ltd.), and EPDM (“Esplen 505 manufactured by Sumitomo Chemical Co., Ltd.) ”) 30 parts by mass, 5 parts by mass of zinc oxide (both manufactured by Hakusui Chemical Co., Ltd.), 1 part of stearic acid (“ Lunac (registered trademark) S30 ”manufactured by Kao Corporation), paraffinic process oil (Nihon Sun Oil Co., Ltd.) 20 parts by mass of “Samper (registered trademark) 110”) was masticated with a roll kneader.

  Next, 270 parts by mass of carbon beads (“Nika Beads ICB0520” manufactured by Nippon Carbon Co., Ltd.), an average particle diameter of about 5 μm and a sulfur content of D90 / D10 = 3.2) are added and mixed in a roll kneader. Dispersed. Furthermore, as a vulcanization accelerator, 1.5 parts by mass of zinc dimethyldithiocarbamate (“Noxeller (registered trademark) PZ-P” manufactured by Ouchi Shinsei Chemical Co., Ltd.), tetramethylthiuram disulfide (“Sunseller (registered by Sanshin Chemical Co., Ltd.)) (Trademark) TT-G ") 1.5 parts by mass, 0.5 part by mass of 2-mercaptobenzothiazole (" Noxeller MP "manufactured by Ouchi Shinsei Chemical Co., Ltd.) and sulfur (" Sunfax T "manufactured by Tsurumi Chemical Co., Ltd.) −10 ”) and 0.56 parts by mass were added, mixed and dispersed by a roll kneader to prepare an elastomer composition.

  The critical volume fraction of the elastomer composition in the percolation carp was about 43% by volume, and the saturated volume fraction was about 48% by volume. Next, the elastomer composition was formed into a predetermined size (in this embodiment, a square plate shape), and the sensor body 12 was formed by press vulcanization at a predetermined temperature. The filling rate of carbon beads in the molded sensor body 12 was about 48% by volume when the volume of the sensor body 12 was 100% by volume.

(3) Regarding Change in Electrical Resistance of Sensor Body 12 Next, the characteristics of the change in electrical resistance of the sensor body 12 formed as described above will be described with reference to FIGS. FIG. 4 is a diagram for explaining a change in electrical resistance of the sensor body 12. FIG. 5 is a diagram showing the relationship of the change in electrical resistance with respect to the curvature C of the sensor body 12.

  First, as shown in FIG. 4, the sensor main body 12 was formed into a long plate shape, and the electrodes 13 were arranged at both ends thereof. In this case, a state is considered in which a pressing external force is applied to the central portion of the sensor main body 12 and the sensor main body 12 is bent and elastically deformed so as to bend downward in FIG. At this time, when the length in the longitudinal direction of the sensor body 12 in the unloaded state is L, the separation distance between both ends of the sensor body 12 in the loaded state is L1, and the difference between L and L1 is the bending strain distance S, The curvature C (%) is defined by the following equation (2).

  And in the state which changed the curvature C by changing the pressing external force suitably, the electrical resistance between the electrodes 13 at that time was measured. As a result, as shown in FIG. 5, the electrical resistance between the electrodes 13 increases as the curvature C increases. From this, it can be said that the electrical resistance increases as the elastic deformation amount of the sensor body 12 increases.

(4) Detailed Configuration of Control Unit 20 Next, a detailed configuration of the control unit 20 in the deformation sensor system will be described with reference to FIGS. 1 and 6 to 8. FIG. 6 is a diagram for explaining a resistance change amount detection unit 22 a that constitutes the detection unit 22 of the control unit 20. FIG. 7 is a diagram illustrating the resistance change amount detection unit 22a and the external force calculation unit 22c. FIG. 8 is a diagram illustrating the coefficients Kx and Ky stored in the coefficient storage unit 22b.

  As shown in FIG. 1, the control unit 20 includes a power supply circuit 21, a detection unit 22, and an output unit 23. The power supply circuit 21 is electrically connected to the respective electrode pairs 13a to 13h and a resistance change amount detection unit 22a of the detection unit 22 described later via the connector 14 and the wiring 15, and applies the DC voltage Vin. Circuit.

  The detection unit 22 includes a resistance change amount detection unit 22a, a coefficient storage unit 22b, and an external force calculation unit 22c. The resistance change amount detection unit 22a is electrically connected to the power supply circuit 21 and the electrode pairs 13a to 13b. Then, as shown in FIG. 6, the resistance change amount detection unit 22a constitutes a Wheatstone bridge circuit in which the electrical resistance of the sensor body 12 between the electrode pairs 13a to 13h is the first resistance R1. However, both end electrodes of the first resistor R1 are sequentially switched from the first electrode pair 13a to the eighth electrode pair 13h. That is, the first resistor R1 here is the electrical resistance of the sensor body 12 between the first electrode pair 13a, the electrical resistance of the sensor body 12 between the second electrode pair 13b, ..., between the seventh electrode pair 13g. The electrical resistance of the sensor body 12 and the electrical resistance of the sensor body 12 between the eighth electrode pair 13h are sequentially switched.

  Here, as described above, the sensor body 12 is made of a rubber elastic material whose electrical resistance increases as the amount of elastic deformation increases. Therefore, the electrical resistance of each sensor body 12 between the electrode pairs 13a to 13h changes according to the amount of bending elastic deformation caused by the pressing external force. In addition, the second resistor R2, the third resistor R3, and the fourth resistor R4 constituting the Wheatstone bridge circuit have constant resistance values. Here, the value obtained by multiplying the first resistor R1 and the fourth resistor R4 is set to be equal to the value obtained by multiplying the second resistor R2 and the third resistor R3.

  In FIG. 6, the applied voltage Vin is a DC voltage applied by the power supply circuit 21. The resistance change amount detection unit 22a detects the bridge intermediate potential difference Vm. That is, the bridge intermediate potential difference Vm changes with a change in the electrical resistance of the sensor body 12 between the respective electrode pairs 13a to 13h. That is, when a voltage is applied between the electrode pairs 13a to 13h, the resistance change amount detection unit 22a changes the electrical resistances ΔRx1 to ΔRx4 and ΔRy1 of the sensor body 12 between the electrode pairs 13a to 13h. ΔRy4 can be detected.

  As shown in FIG. 7, the electrical resistance changes ΔRx1, ΔRx2, ΔRx3, and ΔRx4 are the electrical resistance changes of the sensor body 12 between the electrode pairs 13a, 13b, 13c, and 13d, respectively. Further, the electrical resistance changes ΔRy1, ΔRy2, ΔRy3, and ΔRy4 are the electrical resistance changes of the sensor body 12 between the electrode pairs 13e, 13f, 13g, and 13h, respectively.

  The coefficient storage unit 22b stores a first coefficient Kx and a second coefficient Ky corresponding to the position of the force receiving surface 12a of the sensor body 12. The first coefficient Kx is a coefficient related to the electrode pairs 13a to 13d arranged in parallel in the X direction, that is, a coefficient related to the Y direction according to the position of the force receiving surface 12a. The second coefficient Ky is a coefficient related to the electrode pairs 13e to 13h arranged in parallel in the Y direction, that is, a coefficient related to the X direction according to the position of the force receiving surface 12a.

  The coefficients Kx and Ky will be described in detail with reference to FIG. Here, the second electrode pair 13b will be described as an example. The influence of the electrical resistance of the sensor body 12 between the second electrode pair 13b varies depending on the position where the external force is received. For example, the change amount ΔRx2 of the electrical resistance between the second electrode pair 13b when P1 receives a predetermined pressing external force F is equal to the electrical resistance between the second electrode pair 13b when P2 receives the same pressing external force F. Less than the change amount ΔRx2. This is because as the positions P1 and P2 of the pressing external force F are farther from the electrodes constituting the second electrode pair 13b, the degree of influence that appears as the amount of change in electrical resistance is smaller. That is, the relationship between the change amount ΔRx2 of the electrical resistance between the second electrode pair 13b and the position P3 of the pressing external force F can be defined as shown in Expression (3).

  That is, according to the expression (3), when the position P of the pressing external force F is located between the two electrodes constituting the second electrode pair 13b on the line segment connecting the electrodes constituting the second electrode pair 13b. However, the amount of change ΔRx2 in electrical resistance is the smallest. On the other hand, when the position P of the pressing external force F is located in the vicinity of one of the electrodes constituting the second electrode pair 13b on the line segment connecting the electrodes constituting the second electrode pair 13b, the amount of change in electrical resistance is greatest. ΔRx2 increases. And from the vicinity of the electrode to the intermediate position between the two electrodes, it changes almost in a multiplier manner. That is, the farther the position P of the pressing external force F is farther from the electrodes constituting the second electrode pair 13b, the greater the change width of the electrical resistance change ΔRx2.

  Thus, even if the force receiving surface 12a of the sensor body 12 receives the same pressing external force, the amount of change in electrical resistance between the electrode pairs 13a to 13h varies depending on the position. Therefore, by converting this relationship into a coefficient and multiplying the coefficient by the detected amount of change in electrical resistance, the calculated value can be the same pressing force regardless of where the pressing force is applied. If an external force is received, interpolation is performed so that the values are the same. That is, the coefficients Kx and Ky are coefficients corresponding to the relationship between the position of the force receiving surface 12a of the sensor body 12 and the amount of change in electrical resistance between the electrode pairs 13a to 13h depending on the position. The reason for having the first coefficient Kx and the second coefficient Ky is that, even if the position of the force receiving surface 12a of the sensor main body 12 is the same, the first electrode pair 13a to the fourth electrode arranged to face each other in the Y direction. This is because the amount of change in electrical resistance is different between the pair 13d and the fifth electrode pair 13e to the eighth electrode pair 13h arranged to face each other in the X direction.

  When the voltage Vin is applied by the power supply circuit 21, the external force calculation unit 22c detects ΔRx1 to ΔRx4 and ΔRy1 to ΔRy4 detected by the resistance change amount detection unit 22a and the first coefficient Kx stored in the coefficient storage unit 22b. Based on the second coefficient Ky, the magnitude of the pressing external force F at each position of the force receiving surface 12a of the sensor body 12 is calculated.

  Calculation of the magnitude of the pressing external force F by the external force calculator 22c will be described with reference to FIG. Here, a case where the magnitude of the pressing external force F at the predetermined position P of the force receiving surface 12a of the sensor main body 12 of FIG. 7 is calculated by the external force calculating unit 22c will be described as an example. Of the coefficients Kx and Ky stored in the coefficient storage unit 22b, the first coefficient at the predetermined position P is Kxp, and the second coefficient is Kyp.

  First, it is assumed that the virtual first direction electrode pair 13x is disposed to face the periphery of the sensor body 12 at a position that passes through the predetermined position P and is separated in the Y direction (the vertical direction in FIG. 7). Then, the change amount ΔRx (v) of the electrical resistance between the virtual first direction electrodes 13x is calculated according to the equation (4).

  That is, the change amount ΔRx (v) of the electrical resistance between the virtual first direction electrodes 13x is calculated based on the change amount of the electrical resistance of the electrode pair of the adjacent first direction electrode group located so as to sandwich the predetermined position P. Is done. In FIG. 7, the change amount ΔRx (v) of the electric resistance is calculated based on the change amounts ΔRx1 and ΔRx2 of the electric resistance between the first electrode pair 13a and the second electrode pair 13b. The distance between the first electrode pair 13a and the second electrode pair 13b is calculated by linear interpolation.

  Further, it is assumed that the virtual second direction electrode pair 13y is disposed opposite to the peripheral portion of the sensor body 12 at a position that passes through the predetermined position P and is separated in the X direction (left and right direction in FIG. 7). Then, the change amount ΔRy (v) of the electrical resistance between the virtual second direction electrodes 13y is calculated according to the equation (5).

  That is, the change amount ΔRy (v) of the electrical resistance between the virtual second direction electrodes 13y is calculated based on the change amount of the electrical resistance of the electrode pair of the adjacent second direction electrode group located so as to sandwich the predetermined position P. Is done. In FIG. 7, the change amount ΔRy (v) of the electric resistance is calculated based on the change amounts ΔRy1 and ΔRy2 of the respective electric resistances between the fifth electrode pair 13e and the sixth electrode pair 13f. The distance between the fifth electrode pair 13e and the sixth electrode pair 13f is calculated by linear interpolation.

  And the external force calculation part 22c calculates the magnitude | size of the press external force Fp in the predetermined position P according to Formula (6).

  In this way, the external force calculation unit 22c calculates the magnitude of the pressing external force F for the entire force receiving surface 12a of the sensor body 12. Then, the output unit 23 outputs the magnitude of the pressing external force at each position of the force receiving surface 12 a calculated by the external force calculating unit 22 c to the monitor 30. At this time, as shown in FIG. 1, the monitor 30 displays a brighter color as the position where the pressing external force is larger. That is, it is possible to grasp that the position displayed brightly on the monitor 30 is a position that has received a pressing external force on the force receiving surface 12a. It is also possible to determine how much the force receiving surface 12a has received a pressing external force.

  In the embodiment described above, the magnitude of the pressing external force at an arbitrary position on the force receiving surface 12a of the sensor body 12 is calculated and displayed. In addition, when it is sufficient to calculate the magnitude of the pressing external force only at a specific position of the force receiving surface 12a, the following can also be performed. In this case, for example, the electrodes are arranged so that the intersection between the first direction electrode pair and the second direction electrode pair is at the specific position, and the first coefficient Kx and the second coefficient Ky of the intersection are used, You may make it calculate the magnitude | size of the pressing external force of a specific position. The method for calculating the pressing external force is substantially the same as in the above embodiment.

  It is also possible to detect only whether or not the force receiving surface 12a receives the pressing external force without calculating the magnitude of the pressing external force at the predetermined position of the force receiving surface 12a. In this case, depending on the relationship with the size of the force receiving surface 12a, there may be a case where only one pair of electrodes is required. Furthermore, it is possible to simply detect the position of the pressing external force without calculating the magnitude of the pressing external force. In this case, it is sufficient that at least three electrodes are arranged so that at least two paths between the electrodes can be formed.

  The deformation sensor system of the present invention can be used as a pressure-sensitive sensor and a load sensor. In addition, it can also be used as a tactile sensor such as a medical robot or an industrial robot. As an example of a tactile sensor, it can be applied to the skin of a humanoid robot.

The whole block diagram of a deformation sensor system is shown. The AA sectional view of Drawing 1 in an unloaded state and a loaded state is shown. The figure explaining the rubber elastic material of the sensor main body 12 is shown. The figure explaining the change of the electrical resistance of the sensor main body 12 is shown. The relationship of the change of the electrical resistance with respect to the curvature C of the sensor main body 12 is shown. The figure explaining the resistance change amount detection part 22a which comprises the detection part 22 of the control part 20 is shown. The figure explaining resistance change amount detection part 22a and external force calculation part 22c is shown. The figure explaining the coefficients Kx and Ky memorize | stored in the coefficient memory | storage part 22b is shown.

Explanation of symbols

10: sensor structure, 20: control unit, 30: monitor,
11: mounting plate, 12: sensor body, 12a: force receiving surface, 12b: elastomer, 12c: conductive filler,
13a to 13h: electrode pairs,
13x: virtual first direction electrode pair, 13y: virtual second direction electrode pair,
14: Connector, 15: Wiring,
21: Power supply circuit, 22: Detection unit, 23: Output unit,
22a: resistance change amount detection unit, 22b: coefficient storage unit, 22c: external force calculation unit,
Ps: conductive path,
Kx: first coefficient, Ky: second coefficient

Claims (10)

A sensor body comprising a rubber elastic material whose electrical resistance increases as the amount of elastic deformation increases, and having a predetermined region that elastically deforms when subjected to an external force;
A plurality of electrodes arranged so as to sandwich the predetermined region of the sensor body;
A detection unit that detects that the external force is applied to the predetermined region based on a change in the electrical resistance of the sensor body due to the external force between the electrodes when a voltage is applied between the electrodes;
A deformation sensor system comprising: The electrode consists of 3 or more,
The deformation sensor system according to claim 1, wherein the detection unit detects a position where the external force is received based on a change in the electrical resistance. The electrode is
A first direction electrode group comprising a plurality of first direction electrode pairs arranged on a predetermined surface so as to be spaced apart from each other in the predetermined first direction;
A second direction electrode group comprising a plurality of second direction electrode pairs disposed on the predetermined surface so as to sandwich the predetermined region in a second direction orthogonal to the first direction;
A deformation sensor system according to claim 2.   The deformation sensor system according to claim 2, wherein the detection unit detects a position of the external force and a magnitude of the external force at the position based on a change in the electrical resistance. The detector is
A coefficient storage unit that stores a coefficient according to a position on a predetermined surface in the predetermined area;
An external force calculation unit that calculates the magnitude of the external force at each position on the predetermined surface based on the coefficient and the change in the electrical resistance;
A deformation sensor system according to claim 4.   The external force calculation unit is a virtual first direction electrode disposed at a predetermined position on the predetermined surface and spaced apart so as to pass through the predetermined position on the predetermined surface and sandwich the predetermined region in a predetermined first direction. Changes in the electrical resistance between the pairs, and virtual second direction electrode pairs disposed so as to be spaced apart from each other in a second direction that passes through a predetermined position on the predetermined surface and is orthogonal to the first direction The deformation sensor system according to claim 5, wherein the magnitude of the external force at a position on the predetermined surface is calculated based on a change in the electric resistance between the two. The coefficient storage unit stores a first coefficient related to the first direction according to a position on the predetermined plane and a second coefficient related to the second direction according to a position on the predetermined plane,
The deformation sensor system according to claim 6, wherein the external force calculation unit calculates the magnitude of the external force according to Equation (1).

The electrode is
A first direction electrode group comprising a plurality of first direction electrode pairs arranged on a predetermined surface so as to be spaced apart from each other in the predetermined first direction;
A second direction electrode group comprising a plurality of second direction electrode pairs disposed on the predetermined surface so as to sandwich the predetermined region in a second direction orthogonal to the first direction;
With
The external force calculator is
Calculating a change in the electrical resistance between the virtual first direction electrode pair based on the change in the electrical resistance of the adjacent first direction electrode pair positioned so as to sandwich the predetermined position;
The change in the electrical resistance between the virtual second direction electrode pairs is calculated based on the change in the electrical resistance of the adjacent second direction electrode pairs located so as to sandwich the predetermined position. The deformation sensor system described. The electrode is
A first direction electrode group comprising a plurality of first direction electrode pairs arranged on a predetermined surface so as to be spaced apart from each other in the predetermined first direction;
A second direction electrode group comprising a plurality of second direction electrode pairs disposed on the predetermined surface so as to sandwich the predetermined region in a second direction orthogonal to the first direction;
With
The coefficient storage unit stores the coefficient at an intersection of a line segment connecting each of the first direction electrode pairs and a line segment connecting each of the second direction electrode pairs,
The external force calculation unit includes the coefficient at each intersection, the change in the electrical resistance between the first direction electrode pairs passing through each intersection, and the second direction electrode pair passing through each intersection. The deformation sensor system according to claim 5, wherein the magnitude of the external force at each of the intersections is calculated based on a change in the electric resistance between the two.   The rubber elastic material has an elastomer made of a predetermined rubber, and a spherical conductive filler blended in the elastomer in a substantially single particle state with a high filling rate. The deformation sensor system according to claim 1.

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