JP5302501B2 - Vehicle exterior member deformation sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sensor capable of accurately detecting a deformation in an exterior member of a vehicle due to collision and the like. <P>SOLUTION: The vehicle exterior member deformation sensor 20 is composed of: a sensor body 201 which has an elastomer and spherical conductive fillers blended in the elastomer at a high filling rate so as to be in an approximately single-particle state, and can be elastically deformed such that its electric resistance increases as the amount of its elastic deformation increases; and electrodes A, B and M which are connected to the sensor body 201 and can output the electric resistance. Then, the sensor 20 is disposed at the exterior member 900 present outside the vehicle 9. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

  The present invention relates to a sensor capable of detecting deformation of an exterior member of a vehicle due to a collision or the like.

The automobile is equipped with an occupant protection system for protecting the occupant in the event of a collision. The occupant protection system includes a sensor that detects an impact, an occupant protection ECU (electronic control unit) that determines whether or not there is a collision based on a signal from the sensor, and an occupant protection device such as an airbag. . Here, as a sensor that detects an impact, for example, there is an acceleration sensor that detects acceleration at the time of a collision (appropriately including deceleration, the same applies hereinafter) (see Patent Document 1). There is also a load sensor that detects a load at the time of collision using an optical fiber (see Patent Document 2).
JP-A-6-56000 JP 2006-142876 A

  For example, when a vehicle collides forward with another vehicle or the like, acceleration occurs in the forward direction (traveling direction) of the vehicle. Further, when another vehicle collides from the side, acceleration occurs in the left-right direction of the vehicle. The acceleration sensor detects the generated acceleration, and the occupant protection ECU determines whether or not it is a collision based on the acceleration value. That is, according to the acceleration sensor, the presence or absence of a collision is indirectly determined from the acceleration. However, other than the collision, for example, the acceleration is generated by a traveling state such as riding on a curb or traveling on a rough road. For this reason, even when there is no collision, it is determined that the collision has occurred due to the generated acceleration, and the occupant protection device may malfunction.

  In addition, the acceleration sensors are usually scattered and installed in the vehicle body. Further, the acceleration sensor cannot detect the acceleration unless it receives the acceleration. For this reason, when a part away from the installation position collides partially, the acceleration is difficult to detect and the collision cannot be accurately recognized.

  On the other hand, in an optical fiber sensor, when an optical fiber is deformed by a collision, a loss of light transmitted from one end of the optical fiber to the other end increases. The occupant protection ECU determines whether or not there is a collision based on the light loss value. However, it is difficult to route the optical fiber sensor over a wide range, and the wiring path is complicated. In particular, when the installation location is a curved surface, it is difficult to route. Further, as described above, the optical fiber sensor performs collision determination using deformation of the optical fiber. Here, the deformation amount of the optical fiber is relatively small. For this reason, the detection range of the optical fiber sensor is relatively narrow. Further, when trying to detect a collision position using an optical fiber sensor, an independent light emitting source and light receiving source are required according to the detected position. For this reason, an occupant protection system becomes expensive.

  This invention is made | formed in view of such a situation, and makes it a subject to provide the sensor which can detect the deformation | transformation of the exterior member by the collision of a vehicle etc. correctly.

(1) The vehicle exterior member deformation sensor of the present invention (hereinafter referred to as “the exterior member deformation sensor of the present invention” as appropriate) is composed of an elastomer, a substantially single particle state in the elastomer, and the entire sensor body. And a spherical conductive filler blended at a filling rate of 30 vol% or more and 65 vol% or less when the volume of the material is 100 vol%, and the amount of elastic deformation increases in all deformations due to compression, extension and bending An elastically deformable sensor body whose electrical resistance increases in accordance with the electrode, and an electrode connected to the sensor body and capable of outputting the electrical resistance, the sensor body comprising the elastomer and the conductive filler. It consists of an elastomer composition as an essential component, and in the percolation curve representing the relationship between the blending amount of the conductive filler and the electrical resistance of the elastomer composition The amount of the conductive filler blended at the second inflection point at which the electrical resistance change is saturated (saturated volume fraction: φs) is 35 vol% or more, and is disposed on the exterior member exposed outside the vehicle. It is possible to detect the deformation of (corresponding to claim 1).

  The exterior member deformation sensor of the present invention is disposed on an exterior member of a vehicle. The exterior member is exposed to the outside of the vehicle and forms an outer shell of the vehicle body. For this reason, when the vehicle collides with a collision target such as a person or an object, the exterior member is deformed first. Therefore, according to the exterior member deformation sensor of the present invention, a collision or the like can be detected at an early stage.

The sensor body in the exterior member deformation sensor of the present invention (hereinafter appropriately referred to as “sensor body in the present invention”) is elastically deformable and includes an elastomer and a spherical conductive filler. In this specification, “elastomer” includes rubber and thermoplastic elastomer. Further, the conductive filler is blended in the elastomer in a substantially single particle state and at a filling rate of 30 vol% or more and 65 vol% or less when the entire volume of the sensor body is 100 vol% . Here, the “substantially single particle state” means that 50% by weight or more when the total weight of the conductive filler is 100% by weight exists not in the form of aggregated secondary particles but in the form of single primary particles. It means that Further, hereinafter, “high filling rate” means that the conductive filler is blended in a state close to closest packing.
The sensor body in the present invention is made of an elastomer composition having a saturated volume fraction (φs) of 35 vol% or more. Generally, when an electrically conductive filler is mixed with an insulating elastomer to form an elastomer composition, the electrical resistance of the elastomer composition varies depending on the blending amount of the conductive filler. In FIG. 3, the relationship between the compounding quantity of an electroconductive filler and an electrical resistance in an elastomer composition is shown typically.
As shown in FIG. 3, when the conductive filler 102 is mixed with the elastomer 101, the electrical resistance of the elastomer composition is almost the same as the electrical resistance of the elastomer 101 at first. However, when the blending amount of the conductive filler 102 reaches a certain volume fraction, the electric resistance rapidly decreases and an insulator-conductor transition occurs (first inflection point). A blending amount of the conductive filler 102 at the first inflection point is referred to as a critical volume fraction (φc). Further, when the conductive filler 102 is further mixed, from a certain volume fraction, the change in electrical resistance is reduced and the change in electrical resistance is saturated (second inflection point). The blending amount of the conductive filler 102 at the second inflection point is referred to as a saturated volume fraction (φs). Such a change in electrical resistance is called a percolation curve and is considered to be due to the formation of a conductive path P1 by the conductive filler 102 in the elastomer 101.
For example, if the conductive filler aggregates and forms an aggregate due to the small particle size of the conductive filler or poor compatibility between the conductive filler and the elastomer, one-dimensional conductive A path is easily formed. In such a case, the critical volume fraction (φc) of the elastomer composition is relatively small, such as about 20 vol%. Similarly, the saturated volume fraction (φs) is also relatively small. In other words, when the critical volume fraction (φc) and the saturated volume fraction (φs) are small, the conductive filler hardly exists as primary particles, and secondary particles (aggregates) are easily formed. Therefore, in this case, it is difficult to blend a large amount of the conductive filler in the elastomer. That is, it is difficult to mix the conductive filler in a state close to closest packing. Further, when a large amount of a conductive filler having a small particle diameter is blended, the aggregated structure grows three-dimensionally, so that the change in conductivity with respect to deformation becomes poor.
In this respect, the saturated volume fraction (φs) of the elastomer composition forming the sensor body is as large as 35 vol% or more. For this reason, the conductive filler is stably present in the elastomer in a substantially single particle state. Therefore, the conductive filler can be blended in a state close to closest packing. Moreover, in the sensor main body in this invention, the filling rate of an electroconductive filler is 30 vol% or more and 65 vol% or less. Thereby, the conductive filler is blended in the elastomer in a state close to closest packing. Therefore, a three-dimensional conductive path by the conductive filler is easily formed in the sensor body.

  As described above, when the conductive filler is blended in a substantially single particle state and at a high filling rate, a three-dimensional conductive path is formed by contact between the conductive fillers via the elastomer component (film). The Therefore, the sensor body in the present invention has high conductivity in a state where no load is applied (hereinafter referred to as “no-load state” as appropriate), in other words, in a natural state where the sensor body is not deformed. Note that “elastic deformation” in this specification includes all deformation due to compression, extension, bending, and the like.

  For example, a conventional pressure-sensitive conductive resin has a large electric resistance in an uncompressed state, and the electric resistance decreases when deformed by compression. This can be explained from the configuration of the pressure-sensitive conductive resin as follows. That is, the pressure sensitive conductive resin is composed of a resin and a conductive filler blended in the resin. Here, the filling rate of the conductive filler is low. For this reason, the conductive fillers are separated from each other in a no-load state. That is, in the no-load state, the electric resistance of the pressure sensitive conductive resin is large. When a load is applied and the pressure-sensitive conductive resin is deformed, the conductive fillers are brought into contact with each other to form a one-dimensional conductive path. This reduces the electrical resistance.

  On the other hand, the electrical resistance of the sensor body according to the present invention increases as the amount of elastic deformation increases. The reason is considered as follows. FIG. 1 and FIG. 2 show changes in the conductive path of the sensor body according to the present invention before and after applying a load as a model. However, what is shown in FIGS. 1 and 2 is an example of the sensor main body, and the sensor main body, the shape and material of the conductive filler in the present invention are not limited at all.

  As shown in FIG. 1, in the sensor main body 100, most of the conductive fillers 102 are present in the state of primary particles in the elastomer 101. Moreover, the filling rate of the conductive filler 102 is high, and it is blended in a state close to closest packing. Thereby, in a no-load state, a three-dimensional conductive path P is formed in the sensor body 100 by the conductive filler 102. Therefore, in the no-load state, the electrical resistance of the sensor body 100 is small. On the other hand, as shown in FIG. 2, when a load is applied to the sensor main body 100, the sensor main body 100 is elastically deformed (the dotted line frame in FIG. 2 indicates the no-load state in FIG. 1). Here, since the conductive filler 102 is blended in a state close to closest packing, there is almost no space where the conductive filler 102 can move. Therefore, when the sensor main body 100 is elastically deformed, the conductive fillers 102 repel each other, and the contact state between the conductive fillers 102 changes. As a result, the three-dimensional conductive path P collapses and the electrical resistance increases.

  The exterior member deformation sensor of the present invention provided with such a sensor body is subject to various deformations such as compression, expansion, bending, etc. that occur in the exterior member of the vehicle based on an increase in the electrical resistance of the sensor body output from the electrode. Can be detected directly. In addition, a load or the like that causes the deformation can be detected. Here, “electric resistance can be output” means that electric resistance can be output directly or indirectly. That is, not only the case where the electrical resistance is directly output from the electrode but also the case where the other electrical quantity related to the electrical resistance such as voltage or current is output.

  The sensor body in the present invention uses an elastomer as a base material. For this reason, the exterior member deformation sensor of this invention is excellent in workability, and has a high freedom degree of shape design. Therefore, it is easy to dispose the exterior member having a complicated shape, and a load and deformation in a wide region of the exterior member can be detected. For example, if the exterior member deformation sensor of the present invention is arranged over the entire circumference of the vehicle, collisions from the front, rear, side, etc. can be detected without exception. Further, by adjusting the number and arrangement of the electrodes connected to the sensor main body, finer sensing can be performed, and the load application position and the deformation position can be specified.

  In the exterior member deformation sensor of the present invention, the electrical resistance value in a no-load state can be set within a predetermined range by adjusting the type of elastomer or conductive filler, the filling rate of the conductive filler, and the like. For this reason, the range of detectable load and elastic deformation amount, that is, the detection range can be increased. In addition, since the increase behavior of the electrical resistance with respect to the elastic deformation amount can be adjusted, a desired response sensitivity can be realized.

  The exterior member deformation sensor of the present invention has high conductivity in a no-load state. That is, the exterior member deformation sensor of the present invention is in a conductive state in a no-load state. For this reason, in a no-load state, operation diagnosis is easier as compared with a sensor having low conductivity (for example, a sensor using a conventional pressure-sensitive conductive resin). That is, in the case of a sensor having low conductivity in a no-load state, it is difficult to determine whether the sensor is normal or abnormal (for example, whether a circuit is disconnected) in the no-load state. For this reason, it is necessary to dare to apply a relatively high voltage to a sensor having low conductivity. Alternatively, it is necessary to check the energized state by operating the sensor on a trial basis. Therefore, the operation diagnosis is complicated. On the other hand, the exterior member deformation sensor of the present invention has high conductivity in a no-load state. For this reason, it is easy to discriminate between normal and abnormal in a no-load state. Therefore, operation diagnosis is easy. For example, when an engine is operated, an operation diagnosis can be easily performed by allowing a current to flow through a circuit incorporating the exterior member deformation sensor of the present invention in conjunction with turning on an ignition switch of the vehicle. Can do.

  (2) Preferably, in the configuration of (1), the exterior member may be at least one of a bumper cover and a door panel (corresponding to claim 2). For example, when the exterior member deformation sensor of the present invention is disposed on the bumper cover, it is possible to quickly detect a collision from the front and rear of the vehicle. Moreover, when arrange | positioning at a door panel, the collision from the vehicle side can be detected rapidly. According to this configuration, since the collision can be detected earlier, the occupant protection device can be driven quickly.

  (3) Preferably, in the configuration of (1) or (2), the sensor body may be configured to be elastically bendable (corresponding to claim 3). According to this configuration, it is possible to detect a change in electrical resistance when the exterior member is bent and deformed. In addition, it is easy to ensure a large amount of elastic deformation in the bending deformation as compared with simple compression deformation and expansion deformation. For this reason, according to this structure, the load which acts on an exterior member and the bending deformation of an exterior member can be detected with high precision.

  (4) Preferably, in the configuration of (3), the sensor body includes a fixed surface fixed to the exterior member and a back surface facing away from the fixed surface, It is good to set it as the structure by which the restraint member which restrains the elastic deformation of this back surface is arrange | positioned (corresponding to claim 4). Here, “fixed to the exterior member” includes both an aspect in which the sensor main body is directly fixed to the exterior member and an aspect in which the sensor main body is indirectly fixed via some fixing member ( The same applies to the configuration of (5) below). According to this configuration, the elastic deformation of the back surface of the sensor body is restricted by the restraining member. This increases the difference between the amount of elastic deformation of the fixed surface and the amount of elastic deformation of the back surface. As a result, the amount of elastic deformation of the entire sensor body increases, and the amount of increase in electrical resistance also increases. That is, it becomes easy to detect the load acting on the exterior member and the deformation caused thereby.

  (5) Preferably, in the configuration of (3), the sensor main body includes a fixed surface fixed to the exterior member, and a back surface facing away from the fixed surface. The surface may be configured to be exposed (corresponding to claim 5). According to this configuration, the sensor main body is securely fixed to the exterior member by the fixing surface. Therefore, the bending deformation of the exterior member can be accurately detected. Further, since the restraining member as in the configuration (4) is not arranged, the configuration is simplified and the manufacturing cost can be suppressed.

  (6) Preferably, in any one of the configurations (1) to (5), the sensor body has a long shape, and a plurality of the electrodes are arranged along the longitudinal direction of the sensor body. (Corresponding to claim 6). According to this configuration, for example, finer sensing is possible by arranging the electrodes at predetermined intervals in the longitudinal direction of the sensor body. Also, it is possible to specify the load application position and the deformation position.

(7) Preferably, in any one of the configurations (1) to (6) , the conductive filler may be a carbon bead (corresponding to claim 7 ). 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.

(8) Preferably, in any one of the configurations (1) to (7) , the conductive filler may have an average particle size of 0.05 μm or more and 100 μm or less (corresponding to claim 8 ). . According to this configuration, the conductive filler hardly aggregates and tends to exist in a primary particle state. In addition, an average particle diameter means the average particle diameter of the electroconductive filler which exists in the state of a primary particle.

(9) Preferably, in any one of the constitutions (1) to (8) , the elastomer is silicone rubber, ethylene-propylene copolymer rubber, natural rubber, styrene-butadiene copolymer rubber, acrylonitrile-butadiene copolymer. It is good to set it as the structure containing 1 or more types chosen from rubber | gum and acrylic rubber (corresponding to claim 9 ). According to this configuration, the compatibility between the elastomer and the conductive filler is good. For this reason, it becomes easy for a conductive filler to exist in the state of a primary particle.

  Hereinafter, embodiments of the exterior member deformation sensor of the present invention will be described. First, an embodiment of the exterior member deformation sensor of the present invention will be described, and then a sensor body constituting the exterior member deformation sensor of the present invention will be described in detail.

<Exterior member deformation sensor>
In the embodiment described below, the exterior member deformation sensor of the present invention is incorporated into an occupant protection system for an automobile.

(1) 1st embodiment First, arrangement | positioning of the exterior member deformation | transformation sensor of this embodiment is demonstrated. FIG. 4A shows a transparent top view of a vehicle in which the exterior member deformation sensor is arranged. FIG. 4B shows a transparent side view of the vehicle. In FIG. 4 and subsequent figures, the direction is defined with reference to the traveling direction of the vehicle 9.

  As shown in FIG. 4, the front bumper 90 of the vehicle 9 has a front bumper sensor unit 2, the left front door 91L has a left front door sensor unit 3L, the left rear door 92L has a left rear door sensor unit 4L, and the right front door. 91R includes a right front door sensor unit 3R, a right rear door 92R includes a right rear door sensor unit 4R, and a rear bumper 93 includes a rear bumper sensor unit 5 (in FIG. 4, for convenience of explanation, these sensors are included). Shown with hatched units). Further, an occupant protection ECU (hatched for convenience of explanation in FIG. 4) 6 is embedded under a substantially central floor of the vehicle 9.

  The front bumper sensor unit 2, the left front door sensor unit 3L, the left rear door sensor unit 4L, the right front door sensor unit 3R, the right rear door sensor unit 4R, the rear bumper sensor unit 5, and the occupant protection ECU 6 are respectively connected by harnesses.

  The front bumper sensor unit 2 and the rear bumper sensor unit 5 are each extended along the left-right direction (vehicle width direction) of the vehicle. The left and right end portions of the front bumper sensor unit 2 and the rear bumper sensor unit 5 are arranged around the sides of the vehicle 9, respectively. The left front door sensor unit 3L, the left rear door sensor unit 4L, the right front door sensor unit 3R, and the right rear door sensor unit 4R are each extended along the front-rear direction of the vehicle.

  Next, the arrangement of the front bumper sensor unit 2 built in the front bumper 90 will be described in detail. The arrangement, configuration, movement, and effect of the rear bumper sensor unit 5 built in the rear bumper 93 are the same as those of the front bumper sensor unit 2. Therefore, hereinafter, only the front bumper sensor unit 2 will be described, and the description of the rear bumper sensor unit 5 will also be used.

  FIG. 5 shows a transparent perspective view of the vicinity of the front bumper 90 of the vehicle 9. For convenience of explanation, the front bumper sensor unit 2 is indicated by a bold line. As shown in FIG. 5, the front bumper sensor unit 2 is disposed along the back surface (rear surface) of the bumper cover 900 of the front bumper 90.

  FIG. 6 shows a rear view of the bumper cover 900. FIG. 7 is a cross-sectional view taken along the line VII-VII in FIGS. 5 and 6. As shown in FIGS. 6 and 7, the front bumper 90 includes a bumper cover 900, an energy absorber 901, and a bumper reinforcement 903.

  The bumper reinforcement 903 is made of an aluminum alloy and has a long rectangular tube shape. The bumper reinforcement 903 is extended in the vehicle width direction. The left and right ends of the bumper reinforcement 903 are fixed to the front end of a steel front side member 904.

  The energy absorber 901 is made of foamed PP (polypropylene) and has a long shape. The energy absorber 901 extends in the vehicle width direction. The energy absorber 901 is fixed to the front surface of the bumper reinforcement 903. A groove portion 902 extending in the vehicle width direction is recessed in the front surface of the energy absorber 901.

  The bumper cover 900 is made of an olefin resin and has a long shape. The bumper cover 900 extends in the vehicle width direction. The bumper cover 900 covers the energy absorber 901.

  The front bumper sensor unit 2 is fixed to a portion facing the groove 902 of the energy absorber 901 on the back surface of the bumper cover 900. In other words, the front bumper sensor unit 2 is accommodated in the groove 902.

  Next, the configuration of the front bumper sensor unit 2 will be described. FIG. 8 shows an enlarged view in a circle VIII in FIG. As shown in FIGS. 6 to 8, the front bumper sensor unit 2 includes a front bumper sensor 20, a bridge circuit 21, and an amplifier 22. Among these, the front bumper sensor 20 is included in the exterior member deformation sensor of the present invention.

  The front bumper sensor 20 includes an electrode film part 200, a sensor main body 201, a restraining film part 202, and a connector 203. The electrode film unit 200 includes a base film 200a and a cover film 200b. The base film 200a is made of polyimide and has a strip shape extending in the left-right direction. The base film 200a is fixed to the back surface (rear surface) of the bumper cover 900.

  The cover film 200b is made of polyimide and has a strip shape extending in the left-right direction. The cover film 200b covers the surface (rear surface) of the base film 200a. In the center of the cover film 200b in the width direction (vertical direction), a rectangular long hole 200c extending in the left-right direction is formed.

  The sensor main body 201 has a long plate shape extending in the left-right direction. The sensor body 201 is fixed to the surface of the base film 200a while being accommodated in the long hole 200c of the cover film 200b. The contact surface of the sensor body 201 with the base film 200a corresponds to the fixed surface of the present invention.

  The sensor body 201 is made of an elastomer composite material in which carbon beads (“Nika Beads ICB0520” manufactured by Nippon Carbon Co., Ltd., average particle diameter of about 5 μm) are blended in EPDM. The filling rate of the carbon beads is 48 vol% when the volume of the sensor main body 201 is 100 vol%. In the percolation curve of an elastomer composition in which carbon beads are mixed with EPDM (ethylene-propylene-diene terpolymer), the critical volume fraction (φc) is 43 vol%, and the saturated volume fraction (φs) is 48 vol%. It is.

  An electrode A is attached to the left end of the sensor body 201, an electrode B is attached to the right end, and an electrode M is attached between the electrodes A and B. More specifically, each of the electrodes A, B, and M is made of metal and has a strip shape extending vertically. The electrodes A, B, and M are interposed between the sensor main body 201 and the base film 200a, and between the cover film 200b and the base film 200a. The electrodes A, B, M and the connector 203 are each connected by a conducting wire. The conducting wires are interposed between the cover film 200b and the base film 200a, respectively. The sensor body 201 is divided into a left section 201L and a right section 201R by the electrodes A, B, and M. The left section 201L is disposed between the electrode A and the electrode M. The right section 201R is disposed between the electrode M and the electrode B.

  The restraint film portion 202 is made of polyimide and has a strip shape extending in the left-right direction. The restraining film portion 202 is fixed to the surface (that is, the rear surface) opposite to the base film 200a side in the sensor body 201. The contact surface of the sensor body 201 with the restraining film portion 202 corresponds to the back surface of the present invention. The restraining film part 202 is included in the restraining member in the present invention.

  The connector 203 is connected to the left side of the electrode film part 200. As described above, the connector 203 is connected to the electrodes A, M, and B. The bridge circuit 21 and the amplifier 22 are formed as a single component in structure. The bridge circuit 21 and the amplifier 22 are connected to the left side of the connector 203.

  Next, the arrangement of the left front door sensor unit 3L built in the left front door 91L will be described in detail. The arrangement, configuration, movement, and effects of the left rear door sensor unit 4L built in the left rear door 92L, the right front door sensor unit 3R built in the right front door 91R, and the right rear door sensor unit 4R built in the right rear door 92R. Is the same as the left front door sensor unit 3L. Therefore, only the left front door sensor unit 3L will be described below, and the left rear door sensor unit 4L, the right front door sensor unit 3R, and the right rear door sensor unit 4R will also be described.

  FIG. 9 shows a transparent perspective view of the vehicle 9 when the door is opened near the left front door 91L. For convenience of explanation, the left front door sensor unit 3L is indicated by a bold line. As shown in FIG. 9, the left front door sensor unit 3L is disposed along the back surface (right surface) of the front door outer panel 910 of the left front door 91L.

  FIG. 10 shows a rear view of the front door outer panel 910. FIG. 11 is a cross-sectional view taken along the line XI-XI in FIGS. 9 and 10. As shown in FIGS. 10 and 11, the left front door 91 </ b> L includes a front door outer panel 910, a front door inner panel 911, and an opening weather strip outer 912.

  Both the front door outer panel 910 and the front door inner panel 911 are made of steel plates. The peripheral edge of the front door outer panel 910 and the peripheral edge of the front door inner panel 911 are joined. The opening weatherstrip outer 912 is made of rubber and has an annular shape. The opening weather strip outer 912 is fixed along the periphery of the front door inner panel 911. When the door is closed, the opening weather strip outer 912 is in elastic contact with the side outer panel 913.

  The left front door sensor unit 3L is fixed to the back surface of the front door outer panel 910. That is, the left front door sensor unit 3L is accommodated in a bag-like space secured between the front door outer panel 910 and the front door inner panel 911.

  Next, the configuration of the left front door sensor unit 3L will be described. The difference between the configuration of the left front door sensor unit 3L and the configuration of the front bumper sensor unit 2 is that two electrodes are arranged instead of three.

  That is, the left front door sensor unit 3L includes a left front door sensor 30L, a bridge circuit 31L, and an amplifier 32L. Among these, the left front door sensor 30L is included in the exterior member deformation sensor of the present invention.

  The left front door sensor 30L includes an electrode film part 300, a sensor main body 301, a restraining film part 302, and a connector 303. The electrode film unit 300 includes a base film 300a and a cover film 300b. The base film 300a is made of polyimide and has a strip shape extending in the front-rear direction. The base film 300a is fixed to the back surface (right surface) of the front door outer panel 910. The cover film 300b is made of polyimide and has a strip shape extending in the front-rear direction. The cover film 300b covers the surface (right surface) of the base film 300a. In the center of the width direction (vertical direction) of the cover film 300b, a rectangular long hole 300c extending in the front-rear direction is formed.

  The sensor main body 301 has a long plate shape extending in the front-rear direction. The sensor main body 301 is fixed to the surface of the base film 300a while being accommodated in the long hole 300c of the cover film 300b. The contact surface of the sensor body 301 with the base film 300a corresponds to the fixed surface of the present invention. The material of the sensor body 301 is the same as that of the sensor body 201.

  An electrode a is attached to the rear end of the sensor body 301, and an electrode b is attached to the front end. More specifically, the electrodes a and b are each made of metal and have a strip shape extending vertically. The electrodes a and b are interposed between the sensor main body 301 and the base film 300a, and between the cover film 300b and the base film 300a. The electrodes a and b and the connector 303 are each connected by a conducting wire. The conducting wires are interposed between the cover film 300b and the base film 300a, respectively.

  The restraint film portion 302 is made of polyimide and has a strip shape extending in the left-right direction. The restraint film portion 302 is fixed to the surface (that is, the right surface) opposite to the base film 300a side of the sensor body 301. The contact surface of the sensor main body 301 with the restraining film portion 302 corresponds to the back surface of the present invention. The restraining film part 302 is included in the restraining member in the present invention.

  The connector 303 is connected in front of the electrode film unit 300. As described above, the connector 303 is connected to the electrodes a and b. The bridge circuit 31L and the amplifier 32L are structurally formed as a single component. The bridge circuit 31L and the amplifier 32L are connected in front of the connector 303.

  Next, the electrical configuration of the occupant protection system of this embodiment will be described. FIG. 12 shows a block diagram of the occupant protection system of the present embodiment. As shown in FIG. 12, the occupant protection system 1 of this embodiment includes a front bumper sensor unit 2, a left front door sensor unit 3L, a left rear door sensor unit 4L, a right front door sensor unit 3R, and a right rear door sensor unit 4R. A rear bumper sensor unit 5, an occupant protection ECU 6, an airbag device 70, and an active headrest device 71.

  As described above, the front bumper sensor unit 2 includes the front bumper sensor 20, the bridge circuit 21, and the amplifier 22. FIG. 13 shows a circuit diagram of the front bumper sensor unit 2. As shown in FIG. 13, the sensor body 201 of the front bumper sensor 20 is divided into a left section 201L and a right section 201R. The left section 201L is disposed between the electrode A and the electrode M. The right section 201R is disposed between the electrode M and the electrode B. The left section 201L is equivalent to the resistance R (AM), and the right section 201R is equivalent to the resistance R (MB).

  Resistors R <b> 1 to R <b> 3 are arranged in the bridge circuit 21. A Wheatstone bridge circuit is configured by the resistors R1 to R3 and the resistor R (AM) or the resistor R (MB). That is, the resistor R (AM) and the resistor R (MB) are connected to the high potential side of the resistor R1 so that they can be switched alternately. A power supply voltage Vcc is supplied to one end of the Wheatstone bridge circuit. The power supply voltage Vcc is supplied from a 5V power supply (not shown) of the occupant protection ECU 6. The other end of the Wheatstone bridge circuit is grounded (GND).

  Note that the power supply voltage Vcc and the electrical resistance values of the resistors R1 to R3 are each known. For this reason, by measuring the potential difference between the intermediate potential V1 between the resistor R2 and the resistor R3 and the intermediate potential V2 between the resistor R (AM) or the resistor R (MB) and the resistor R1, the left side section 201L is substantially increased. The resistance R (AM) of the right side or the resistance R (MB) of the right section 201R can be measured.

  The amplifier 22 receives intermediate potentials V1 and V2. The potential difference ΔV between the intermediate potentials V1 and V2 is amplified by the amplifier 22 and input to the A / D (analog / digital) converter 600 of the occupant protection ECU 6 as analog voltage data.

  As described above, the left front door sensor unit 3L includes the left front door sensor 30L, the bridge circuit 31L, and the amplifier 32L. FIG. 14 shows a circuit diagram of the left front door sensor unit 3L. As shown in FIG. 14, the section from the electrode a to the electrode b of the sensor body 301 of the left front door sensor 30L is equivalent to the resistance r (ab).

  Resistors r1 to r3 are arranged in the bridge circuit 31L. A Wheatstone bridge circuit is configured by the resistors r1 to r3 and the resistor r (ab). A power supply voltage Vcc is supplied to one end of the Wheatstone bridge circuit. The power supply voltage Vcc is supplied from a 5V power supply (not shown) of the occupant protection ECU 6. The other end of the Wheatstone bridge circuit is grounded (GND).

  The power supply voltage Vcc and the electric resistance values of the resistors r1 to r3 are known. Therefore, by measuring the potential difference between the intermediate potential v1 between the resistor r2 and the resistor r3 and the intermediate potential v2 between the resistor r (ab) and the resistor r1, the resistance r (ab) of the sensor body 301 is substantially measured. Can be measured.

  Intermediate potentials v1 and v2 are input to the amplifier 32L. The potential difference Δv between the intermediate potentials v1 and v2 is amplified by the amplifier 32L and input to the A / D converter 600 of the occupant protection ECU 6 as analog voltage data.

  Returning to FIG. 12, the occupant protection ECU 6 includes a CPU (central processing unit) 60, an airbag drive circuit 61a, and a headrest drive circuit 61b. In the CPU 60, an A / D converter 600, a RAM (Random Access Memory) 601 and a ROM (Read Only Memory) 602 are arranged.

  The A / D converter 600 is an analog voltage input from each of the front bumper sensor unit 2, the left front door sensor unit 3L, the left rear door sensor unit 4L, the right front door sensor unit 3R, the right rear door sensor unit 4R, and the rear bumper sensor unit 5. Convert data to digital data.

  The RAM 601 temporarily stores the converted digital data. On the other hand, the ROM 602 stores an occupant protection program (airbag deployment program, headrest drive program) in advance. In addition, occupant protection thresholds (airbag deployment voltage threshold th1, airbag deployment voltage change rate threshold th2, headrest drive voltage threshold th3, headrest drive voltage change rate threshold th4) ) Is stored. As the airbag deployment voltage threshold th1 and the airbag deployment voltage change rate threshold th2, two types of values are stored depending on the type of collision (forward collision, side collision), respectively. ing.

  The airbag drive circuit 61 a is connected to the airbag device 70. The vehicle 9 actually includes a left front seat front airbag device, a left front seat side airbag device, a left front seat curtain airbag device, a left rear seat side airbag device, a left rear seat curtain airbag device, and a right front seat. A total of 10 airbag devices, a front airbag device, a right front seat side airbag device, a right front seat curtain airbag device, a right rear seat side airbag device, and a right rear seat curtain airbag device, are arranged. An airbag drive circuit is individually arranged for the airbag device. Here, for convenience of explanation, only an arbitrary airbag drive circuit 61a and an airbag device 70 are shown.

  The airbag drive circuit 61a includes a switching element (not shown). The airbag drive circuit 61a generates heat in a squib (not shown) of the airbag device 70. The generated squib ignites an inflator (not shown). Due to the inflated pressure of the inflator thus ignited, the bag body of the airbag device 70 is inflated into the vehicle interior.

  The headrest drive circuit 61 b is connected to the active headrest device 71. The vehicle 9 is actually provided with a total of four active headrest devices, a left front seat active headrest device, a left rear seat active headrest device, a right front seat active headrest device, and a right rear seat active headrest device, A headrest drive circuit is individually arranged for each active headrest device. Here, for convenience of explanation, only an arbitrary headrest driving circuit 61b and an active headrest device 71 are shown. The headrest drive circuit 61 b is connected to the active headrest device 71.

  The headrest drive circuit 61b includes a switching element (not shown). The headrest drive circuit 61b pushes the headrest forward with respect to the seat back via a cable inserted through a pillar of the headrest (not shown).

  Next, the movement of the occupant protection system 1 of the present embodiment will be described. First, the normal traveling of the vehicle 9 will be described. A 5V power source of the occupant protection ECU 6 is connected to each of the front bumper sensor unit 2, the left front door sensor unit 3L, the left rear door sensor unit 4L, the right front door sensor unit 3R, the right rear door sensor unit 4R, and the rear bumper sensor unit 5. For this reason, as shown in FIGS. 13 and 14, the power supply voltage Vcc is supplied to the sensor main body (for example, 201 and 301) of each sensor unit. During normal running, each sensor body is in a natural state with no load.

  Here, during normal running, as shown in FIG. 1, the conductive filler 102 is filled in a state close to closest packing. For this reason, a large number of conductive paths P are formed. Therefore, the electrical resistance value of each sensor body is a minimum value.

  The potential difference ΔV between the intermediate potentials V1 and V2 is amplified by the amplifier 22 and the potential difference Δv between the intermediate potentials v1 and v2 is amplified by the amplifier 32L, and is always transmitted to the CPU 60 of the occupant protection ECU 6 as shown in FIG. Yes. Then, it is digitally converted by the A / D converter 600 and temporarily stored in the RAM 601. On the other hand, as described above, the ROM 602 stores the airbag deployment voltage threshold th1, the airbag deployment voltage change rate threshold th2, the headrest drive voltage threshold th3, and the headrest drive voltage change rate threshold. The value th4 is stored.

  The CPU 60 compares the potential difference (specifically, the potential difference after amplification and digital conversion, hereinafter the same in the present embodiment) ΔV and Δv with the airbag deployment voltage threshold th1. During normal traveling, the potential difference ΔV of the front bumper sensor unit 2 is set so that the airbag deployment voltage threshold th1 (for frontal collision). In addition, the potential difference Δv of each door sensor unit is set to be the airbag deployment voltage threshold th1 (for side collision). In addition, the CPU 60 compares the potential difference ΔV with the headrest driving voltage threshold th3. During normal running, the potential difference ΔV of the rear bumper sensor unit 5 is set to satisfy the headrest driving voltage threshold th3.

  Further, the CPU 60 calculates the rate of change of the potential differences ΔV and Δv (= potential difference change differential value (V / ms)) ΔV ′ and Δv ′. Then, the change rates ΔV ′ and Δv ′ are respectively compared with the airbag deployment voltage change rate threshold th2. During normal running, the change rate ΔV ′ of the front bumper sensor unit 2 <the airbag deployment voltage change rate threshold value th2 (for front collision) is set. Further, the change rate Δv ′ of each door sensor unit <the airbag deployment voltage change rate threshold th2 (for side collision) is set. In addition, the CPU 60 compares the change rate ΔV ′ with the headrest driving voltage change rate threshold th4. During normal driving, the change rate ΔV ′ of the rear bumper sensor unit 5 is set to satisfy the voltage change rate threshold th4 for driving the headrest.

  Next, the front collision will be described. For example, when a collision object (not shown) collides with the left side of the front bumper 90 of the vehicle 9, the left side of the bumper cover 900 is curved and deformed so as to be recessed backward. For this reason, as shown in FIG. 6, the left section 201L of the sensor body 201 of the front bumper sensor unit 2 is also curved and deformed so as to be recessed rearward. As shown in FIG. 13, when the left section 201L is curved and deformed, the electrical resistance value of the resistance R (AM) increases accordingly.

  More specifically, at the time of a forward collision, the conductive fillers 102 repel each other as shown in FIG. For this reason, the conductive path P collapses. Therefore, the electric resistance value of the resistor R (AM) becomes larger than that during normal running.

  In addition, as shown in FIGS. 6 and 8, a restraining film portion 202 is fixed to the surface of the sensor main body 201. For this reason, the expansion deformation near the surface (rear surface) of the sensor body 201 due to the collision is restrained by the restraining film portion 202. Specifically, the restraint film portion 202 restricts the extension deformation near the surface of the sensor main body 201, and the sensor main body 201 undergoes shear deformation. Therefore, the deformation amount of the left section 201L with respect to the normal traveling is further increased. As described above, since both surfaces of the sensor body 201 are constrained, a large strain concentration is induced, and the electric resistance value of the resistor R (AM) is further increased.

  As the electric resistance value of the resistor R (AM) increases, the amount of voltage drop of the power supply voltage Vcc when passing through the resistor R (AM) increases accordingly. Therefore, the intermediate potential V2 is lower than that during normal traveling.

  When the intermediate potential V2 becomes low and the potential difference ΔV ≧ the airbag deployment voltage threshold th1 and the change rate ΔV ′ ≧ the airbag deployment voltage change rate threshold th2, the switching of the airbag drive circuit 61a is performed. The element is turned on. For this reason, the bag body of the airbag apparatus 70 swells in the vehicle interior. Specifically, when an occupant is seated only in the right front seat (driver's seat), the bag body of the right front seat front airbag device bulges into the vehicle interior. Further, when a passenger is seated in the right front seat and the left front seat (passenger seat), the bags of the right front seat front airbag device and the left front seat front airbag device are inflated into the vehicle interior. The movement of the occupant protection system 1 at the time of forward collision (right side), at the time of left collision, and at the time of right collision is the same as the movement at the time of forward collision (left side). Therefore, explanation is omitted here.

  Next, the case of a rear collision will be described. For example, when a collision target (not shown) collides with the left side of the rear bumper 93 of the vehicle 9, the left section of the sensor body of the rear bumper sensor (not shown) is curved and deformed so as to be recessed forward, as in the case of the front collision. For this reason, the electrical resistance value in the left section increases. As shown in FIG. 13, when the electric resistance value in the left section increases, the intermediate potential V <b> 2 becomes lower by that amount than in normal running.

  When the intermediate potential V2 becomes low and the potential difference ΔV ≧ headrest driving voltage threshold th3 and the change rate ΔV ′ ≧ headrest driving voltage change rate threshold th4, the headrest drive circuit 61b causes the active headrest device to 71 is driven. That is, the headrest drive circuit 61b pushes the headrest forward with respect to the seat back via a cable inserted through a pillar of the headrest (not shown). Specifically, when an occupant is seated only in the right front seat, the right front seat active headrest device is driven. Further, when an occupant is seated in the right front seat and the left front seat, the right front seat active headrest device and the left front seat active headrest device are driven.

  Next, the function and effect of the exterior member deformation sensor of this embodiment will be described. As shown in FIG. 1, each sensor unit is disposed on the inner surface of the exterior member that forms the outer shell of the vehicle 9. For this reason, a collision can be detected quickly. In addition, each sensor is disposed over substantially the entire circumference of the vehicle 9. Therefore, collisions from the front, rear, and side can be detected without exception. Also, exterior members such as the bumper cover 900 and the front door outer panel 910 in which the sensor unit is arranged are compared with members constituting an impact transmission path at the time of collision (for example, bumper reinforcement, crash box, side impact protection beam, etc.). And low rigidity. That is, it is easy to deform. For this reason, according to this embodiment, a deformation | transformation, ie, a collision, can be detected more rapidly. Furthermore, in this embodiment, the collision determination is performed by inputting the potential difference itself to the occupant protection ECU 6. For this reason, compared with the case where collision determination is performed after the potential difference is once converted into electric resistance, the time from the collision until the airbag device 70 and the active headrest device 71 are driven can be shortened.

  Further, as shown in FIG. 6, the sensor body 201 of the front bumper sensor 20 is divided into a left section 201L and a right section 201R by electrodes A, B, and M. For this reason, the deformation position of the front bumper 90 can be specified, and the collision can be determined independently for each section.

  Further, when the ignition switch of the vehicle 9 is turned on to operate the engine, a current flows through each sensor unit and is always energized. Thereby, an operation diagnosis can be easily performed.

  In addition, there are fewer misjudgments as compared to the case of performing collision discrimination using an acceleration sensor. That is, in the case of acceleration, even if it is not a collision, it can be considered that it changes abruptly, for example, when the vehicle climbs over a step. On the other hand, the exterior member deformation sensor of the present embodiment can reliably detect the deformation of the exterior member of the vehicle 9 that inevitably occurs in response to the event of a collision. For this reason, there are few erroneous discrimination | determination compared with the case where collision discrimination is performed using an acceleration sensor. Further, since there are few misclassifications, there is little need to dare to complicate the circuit in order to suppress misclassification.

  In addition, since the deformation can be detected regardless of the magnitude of the acceleration, even when the vehicle collides with an obstacle or the like during slow driving, the collision can be reliably detected. For example, even when the rear bumper 93 slowly collides with an obstacle during back parking and the rear bumper 93 is gradually deformed, the rear bumper sensor unit 5 can detect the deformation. Therefore, damage to the rear bumper 93 or the obstacle can be suppressed.

  For example, when an optical fiber sensor is used for collision detection, the entire length of the optical fiber is not fixed to the measurement object. That is, the optical fiber is fixed to the measurement object via a fastener that is arranged for each predetermined length of the optical fiber. For this reason, in the part between adjacent fasteners, there exists a possibility that an optical fiber may be routed in the state which slackened. In this case, the slack of the optical fiber may reduce detection accuracy. In addition, the detection speed may be delayed. In this respect, each sensor unit of the present embodiment is fixed to the measurement object (for example, the bumper cover 900 of FIG. 8) by the base film (for example, the base film 200a of FIG. 8). Yes. For this reason, there is little possibility that slack will occur in the sensor body. Therefore, the detection accuracy is high. In addition, the detection speed is fast.

  The active headrest device 71 is driven by the rear bumper sensor unit 5. For this reason, the active headrest device 71 is reliably driven without being affected by the posture of the occupant in the seat, compared to a system in which the occupant is pressed against the seat back at the time of a rear collision to mechanically push out the headrest. be able to.

(2) Second Embodiment The difference between this embodiment and the first embodiment is that a bridge circuit and an amplifier are shared for all exterior member deformation sensors. Therefore, only the differences will be described here.

  FIG. 15 shows a block diagram of the occupant protection system of the present embodiment. In addition, about the site | part corresponding to FIG. 12, it shows with the same code | symbol. As shown in FIG. 15, a bridge circuit 62 and an amplifier 63 are arranged in the occupant protection ECU 6.

  FIG. 16 shows a circuit diagram of the bridge circuit 62. As shown in FIG. 16, the bridge circuit 62 is connected to each of the front bumper sensor 20, left front door sensor 30L, left rear door sensor 40L, right front door sensor 30R, right rear door sensor 40R, and rear bumper sensor 50. These sensors are all included in the exterior member deformation sensor of the present invention. Each sensor constitutes a Wheatstone bridge circuit together with resistors R10 to R30. Each sensor is in turn repeatedly incorporated into the Wheatstone bridge circuit.

  The front bumper sensor 20 has three electrodes A, B, and M (see FIG. 6). For this reason, when the front bumper sensor 20 is incorporated in the Wheatstone bridge circuit, the left section 201L (resistance R (AM)) between the electrodes A and M is first, and the right section 201R (resistance) between the electrodes M and B is next. R (MB)) are connected in order. This connection method is the same for the rear bumper sensor 50. Returning to FIG. 15, the intermediate potentials V <b> 10 and V <b> 20 of each sensor are transmitted from the bridge circuit 62 to the amplifier 63. The potential difference between the intermediate potentials V10 and V20 amplified by the amplifier 63 is transmitted to the CPU 60.

  The exterior member deformation sensor of the present embodiment has the same effects as the exterior member deformation sensor of the first embodiment. Further, according to the passenger protection system 1 of the present embodiment, the bridge circuit 62 and the amplifier 63 are shared by all the exterior member deformation sensors. For this reason, the number of parts is small. In addition, the exterior member deformation sensor can be reduced in space and weight as much as the bridge circuit and the amplifier need not be disposed on the bumper or the door.

(3) Others The embodiment of the exterior member deformation sensor of 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.

  For example, in each of the above embodiments, the exterior member deformation sensor of the present invention is disposed on the inner surface of the exterior member, but may be disposed on the outer surface of the exterior member. In this way, for example, as shown in FIG. 8, the load can be directly input from the collision target without using the bumper cover 900 or the base film 200a. For this reason, an occupant protection device can be driven more rapidly. Moreover, when the exterior member deformation sensor is exposed to the outside, a weatherproof cover may be disposed so as to cover at least a part of the sensor body. By doing so, deterioration of the sensor body is suppressed, and durability is improved.

  The configuration of the sensor body is not limited to the above embodiment. This will be described later. Moreover, in the said embodiment, the electrode film part and the restraint film part (restraint member) were made from polyimide (PI) with high insulation. However, these materials are not particularly limited. For example, as the restraining member, a resin film such as polyethylene (PE) or polyethylene terephthalate (PET), a metal plate such as a damping steel plate, or the like can be used. Moreover, the aspect which does not arrange | position a restraint member may be sufficient. Further, the base film to which the sensor body is fixed may be a single layer as in the above-described embodiment, or may be a multiple layer in which a plurality of films are laminated. Furthermore, you may fix a sensor main body directly to an exterior member, without arrange | positioning fixing members, such as a base film.

  In the above embodiment, a single exterior member deformation sensor is disposed in each of the front bumper, the left front door, the left rear door, the right front door, the right rear door, and the rear bumper. You may perform by an exterior member deformation | transformation sensor. Further, the number of electrodes arranged on the exterior member deformation sensor is not particularly limited. According to the exterior member deformation sensor of the present embodiment, deformation can be detected for each interval between a pair of electrodes adjacent in the longitudinal direction, so that the accuracy of identifying a collision location can be improved by increasing the number of electrodes. Can do. Further, when the electrode is fixed to the sensor body, it may be fixed by vulcanization adhesion. If it carries out like this, an electrode can be arrange | positioned simultaneously with the vulcanization molding of a sensor main body.

  Moreover, in the said embodiment, although collision determination was performed only with the exterior member deformation sensor, you may perform collision determination in combination with an acceleration sensor. Further, the collision determination may be performed by inputting the engine speed, the vehicle speed, or the like. That is, the exterior member deformation sensor of the present embodiment may be used as an add-on to an existing occupant protection system.

  Moreover, in the said embodiment, although voltage data was output from the exterior member deformation | transformation sensor, you may output electrical resistance data. Further, when data is output, temperature compensation or the like may be performed as appropriate. In addition to the airbag device and the active headrest device, a seat belt tensioner device or the like may be used as the occupant protection device. Moreover, you may arrange | position the exterior member deformation | transformation sensor of this invention in a side outer panel, a side molding, etc. other than a bumper and a door.

  Moreover, you may use the exterior member deformation | transformation sensor of this invention not only for a passenger | crew protection system but for other systems, such as a pedestrian protection system. In this case, the exterior member deformation sensor may be arranged on an exterior member (for example, a bumper, a hood panel, etc.) for absorbing the impact of the colliding pedestrian. The reason is that this type of exterior member is often designed to be more easily deformed from the viewpoint of pedestrian protection.

<Sensor body>
The sensor main body constituting the exterior member deformation sensor of the present invention has an elastomer and a conductive filler. The elastomer can be appropriately selected from rubber and thermoplastic elastomer. The elastomer is desirably insulative. In addition, when a mixture (elastomer composition) with a conductive filler is prepared, it is desirable to use one having a saturated volume fraction (φs) in a percolation curve of 35 vol% or more. This is because when the saturated volume fraction (φs) is less than 35 vol%, it is difficult to blend the conductive filler in a substantially single particle state with a high filling rate. Further, in the region of the saturated volume fraction (φs) or more, the electric resistance is low and stable conductivity is expressed. Therefore, when the saturated volume fraction (φs) is 35 vol% or more, the range of change in electrical resistance from the conductor to the insulator when deformed is widened. Further, it is more preferable to use a saturated volume fraction (φs) of 40 vol% or more. In addition, the “elastomer composition” in the present specification includes an elastomer and a spherical conductive filler as essential components. That is, a mixture of an elastomer and a spherical conductive filler may be used, or a mixture of an elastomer, a spherical conductive filler, and other additives may be used.

In consideration of the affinity with the conductive filler, an elastomer having a gel fraction represented by the following formula (1) of 15% or less may be used. The gel fraction is more preferably 10% or less.
Gel fraction (%) = (Wg−Wf) / Wf × 100 (1)
[Wg in formula (1) is a solvent-insoluble content (gel content of conductive filler and elastomer) obtained when an elastomer composition obtained by mixing a conductive filler in an elastomer is dissolved in a good solvent for the elastomer. It is weight. Wf is the weight of the conductive filler. In addition, as a good solvent of an elastomer, the thing with the close SP value (solubility parameter) of a solvent and an elastomer is desirable, For example, toluene, tetrahydrofuran, chloroform, etc. are mentioned. ]

  The value of the gel fraction is an indicator of the critical volume fraction (φc) in the percolation curve. That is, when the critical volume fraction (φc) is less than 30 vol%, the gel fraction becomes a relatively large value because a large amount of elastomer adsorbed and bonded to the aggregate of the conductive filler exists. On the other hand, when the critical volume fraction (φc) is 30 vol% or more, the conductive filler exists in a substantially single particle state, so that the amount of elastomer adsorbed and bonded to the aggregate of the conductive filler is small, and the gel The fraction is a relatively small value of 15% or less.

  Specific examples of the elastomer include, for example, 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, one kind may be used alone, or two or more kinds may be used in combination. Of these, EPDM having extremely good compatibility with the conductive filler is preferable. Also suitable are NBR and silicone rubber, which have good compatibility with the conductive filler.

  The conductive filler has a spherical shape. The spherical shape 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 portion, a water droplet shape, and the like. included. 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 this case, the saturated volume fraction (φs) may be less than 35 vol%. Further, from the viewpoint of bringing the filling state of the conductive filler in the elastomer closer to the closest packing state, it is preferable to employ particles having a true sphere or a shape very close to a true sphere (substantially spherical) as the conductive filler.

  The conductive filler is not particularly limited as long as it is conductive particles. 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.

  It is desirable that the conductive filler is not aggregated as much as possible and exists in the form of primary particles. Therefore, when selecting the conductive filler, it is preferable to consider the average particle diameter, compatibility with the elastomer, and the like. For example, the average particle diameter (primary particles) of the conductive filler 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. Moreover, there exists a possibility that the said saturated volume fraction ((phi) s) may be less than 35 vol%. Preferably it is 0.5 micrometer or more, More preferably, it is 1 micrometer or more. On the other hand, when the thickness exceeds 100 μm, the translational motion (parallel motion) of the conductive filler due to elastic deformation becomes relatively smaller than the particle diameter, and the change in electric resistance against the elastic deformation of the sensor body becomes slow. Preferably it is 60 micrometers or less, More preferably, it is 30 micrometers or less. In addition, the critical volume fraction (φc) and the saturated volume fraction (φs) are within the desired ranges by appropriately adjusting the combination of the conductive filler and the elastomer, the average particle diameter of the conductive filler, and the like. Can be adjusted.

  Moreover, as for the value of D90 / D10 in the particle size distribution of an electroconductive filler, it is desirable that it is 1-30. Here, D90 is the particle diameter at which the cumulative weight is 90% in the cumulative particle size curve, and D10 is the particle diameter at which the cumulative weight is 10%. When the value of D90 / D10 exceeds 30, since the particle size distribution becomes broad, the increase behavior of the electric resistance with respect to the elastic deformation amount of the sensor body becomes unstable. Thereby, the reproducibility of detection may be reduced. It is more preferable that the value of D90 / D10 is 10 or less. In addition, when using 2 or more types of particle | grains as an electroconductive filler, the value of D90 / D10 should just be 100 or less.

  As such a conductive filler, for example, carbon beads are suitable. 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 diameter of about 7 μm), MC0520 (average particle diameter of about 5 μm)], Nisshinbo carbon beads (average particle diameter of about 10 μm), and the like.

  The conductive filler is blended in the elastomer at a high filling rate. In order to develop desired conductivity, the conductive filler is desirably blended at a ratio equal to or higher than the critical volume fraction (φc) in the percolation curve. From the viewpoint of blending the conductive filler in a substantially single particle state with a high filling rate, the critical volume fraction (φc) is desirably 30 vol% or more. It is more preferable that it is 35 vol% or more. Therefore, for example, the filling rate of the conductive filler is desirably 30 vol% or more and 65 vol% or less when the entire volume of the sensor body is 100 vol%. In the case of less than 30 vol%, the conductive filler is not blended in a state close to the closest packing, and thus desired conductivity is not exhibited. In addition, the change in the electric resistance with respect to the elastic deformation of the sensor body becomes slow, and it becomes difficult to control the increase behavior of the electric resistance. It is more preferable that it is 35 vol% or more. On the other hand, when it exceeds 65 vol%, mixing with the elastomer becomes difficult, and the molding processability is lowered. In addition, the sensor body is difficult to elastically deform. It is more preferable that it is 55 vol% or less.

  In addition to the elastomer and the conductive filler, various additives may be blended in the sensor body. Examples of the additive include a crosslinking agent, a vulcanization accelerator, a vulcanization aid, an antiaging agent, a plasticizer, a softening agent, and a colorant. In addition to the spherical conductive filler, a conductive filler having an irregular shape (for example, a needle shape) may be blended.

  The sensor body can be manufactured, for example, as follows. 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, filled in a mold, and press vulcanized under predetermined conditions.

  Hereinafter, an impact response experiment using the exterior member deformation sensor of the present invention will be described.

<Experimental equipment and experimental method>
In the experiment, a sensor body produced as follows was used. First, 85 parts by weight (85 g) of oil-extended EPDM (“Esplen (registered trademark) 6101” manufactured by Sumitomo Chemical Co., Ltd.) (34 g) and 34 parts of oil-extended EPDM (“Esplen 601” manufactured by Sumitomo Chemical Co., Ltd.) 34 Part (34 g), 30 parts (30 g) of EPDM (“Esplen 505” manufactured by Sumitomo Chemical Co., Ltd.), 5 parts (5 g) of zinc oxide (manufactured by Hakusui Chemical Co., Ltd.), stearic acid (“Lunac” (registered by Kao Corporation) 1 part (1 g) of trademark S30 ") and 20 parts (20 g) of paraffinic process oil (" Samper (registered trademark) 110 "manufactured by Nippon San Oil Co., Ltd.) were kneaded with a roll kneader. Next, 270 parts (270 g) of carbon beads (“Nika Beads ICB0520” manufactured by Nippon Carbon Co., Ltd., average particle diameter of about 5 μm, D90 / D10 = 3.2 in the particle size distribution) are added and mixed in a roll kneader, Dispersed. Furthermore, as a vulcanization accelerator, zinc dimethyldithiocarbamate (“Noxeller (registered trademark) PZ-P” manufactured by Ouchi Shinsei Chemical Co., Ltd.) 1.5 parts (1.5 g), tetramethylthiuram disulfide (manufactured by Sanshin Chemical Co., Ltd.) "Sunseller (registered trademark) TT-G") 1.5 parts (1.5 g), 2-mercaptobenzothiazole ("Noxeller MP" manufactured by Ouchi Shinsei Chemical) 0.5 parts (0.5 g) And 0.56 part (0.56 g) of sulfur (“Sulfax T-10” manufactured by Tsurumi Chemical Co., Ltd.) were added, mixed and dispersed with a roll kneader to prepare an elastomer composition.

  The volume fraction of carbon beads in the prepared elastomer composition was about 48 vol% when the volume of the entire elastomer composition was 100 vol%. Further, the critical volume fraction (φc) in the percolation curve of the elastomer composition was about 43 vol%, and the saturated volume fraction (φ s) was about 48 vol%. Moreover, when the elastomer composition was dissolved in a solvent (toluene) and the solvent insoluble content was measured, the gel fraction was about 3%.

  Next, the elastomer composition was molded into a band having a predetermined size to obtain a molded body. The molded body was filled in a mold, electrodes were arranged at both ends in the longitudinal direction, and press vulcanized at 170 ° C. for 30 minutes to obtain a sensor main body. The filling rate of carbon beads in the obtained sensor main body was about 48 vol% when the volume of the sensor main body was 100 vol%.

  The fabricated sensor body was attached to the back surface of the bumper cover to form an exterior member deformation sensor, and the responsiveness of the sensor to the impact from the bumper cover surface was evaluated. FIG. 17 shows a layout of the exterior member deformation sensor. FIG. 18 shows a schematic diagram of an external circuit in which the sensor is incorporated.

  As shown in FIG. 17, the exterior member deformation sensor 80 includes a sensor body 801 and electrodes 802 </ b> A and 802 </ b> B, and is fixed to the back surface of the bumper cover 900. The electrode 802A is attached to the left end of the sensor body 801, and the electrode 802B is attached to the right end of the sensor body 801. The acceleration sensor 81 is fixed to the back surface of the bumper cover 900. The acceleration sensor 81 is arranged in the vicinity of the center in the longitudinal direction of the exterior member deformation sensor 80 so as to be separated from the exterior member deformation sensor 80.

  The sensor main body 801 is connected to the Wheatstone bridge circuit shown in FIG. 18 via the electrode 802A and the conducting wire 803A, and via the electrode 802B and the conducting wire 803B. Here, the voltage of the power source Vin and the electric resistance values of the resistors R1, R2, and R3 are each known. By measuring the voltage value of the voltmeter Vm, the electric resistance value of the sensor body 801 is measured.

  When an impact is applied to the bumper cover 900 from the back side of the drawing, the bumper cover 900 is deformed, and the exterior member deformation sensor 80 is also deformed accordingly. The deformation of the exterior member deformation sensor 80 is measured by a laser displacement meter (not shown). The electrical resistance value of the exterior member deformation sensor 80 is output to the external circuit from the electrodes 802A, 802B and the like. The acceleration of impact is measured by the acceleration sensor 81.

  Two types of experiments were conducted as follows. In the first experiment, the surface of the bumper cover 900 (the surface in the direction of the back of the paper) was hit with a fist of the hand and an impact was applied (high-speed impact). In FIG. 17, the impact input position is indicated by a dotted circle Z. At this time, the acceleration of the impact, the displacement of the exterior member deformation sensor 80 with respect to the acceleration, and the electric resistance value were measured. In the second experiment, the surface of the bumper cover 900 (surface in the direction opposite to the paper surface) was pressed with the palm of the hand, and an impact was applied (low speed impact). The impact input position was the same as described above. At this time, the acceleration of the impact, the displacement of the exterior member deformation sensor 80 with respect to the acceleration, and the electric resistance value were measured.

<Experimental result>
The experimental results are shown in FIGS. FIG. 19 shows changes over time in acceleration of high-speed impact, displacement of the exterior member deformation sensor, and electrical resistance value in the first experiment. 20 is an enlarged view of the horizontal axis (time: 65 to 85 ms) in FIG. As shown in FIGS. 19 and 20, the electrical resistance value of the exterior member deformation sensor rapidly increased in response to a high-speed impact. Thus, the responsiveness of the exterior member deformation sensor of the present invention is high, and the response delay to impact is so small that it can be ignored. For example, since the operation of the passenger protection system at the time of a collision has a time delay of only a few ms, high-speed response is indispensable for detecting a collision state. The speed of response of the exterior member deformation sensor of the present invention is extremely useful in vehicle collision detection. Further, as shown in FIG. 19, the electric resistance value changes in proportion to the deformation amount of the exterior member deformation sensor. That is, the exterior member deformation sensor of the present invention can directly detect bending deformation.

  FIG. 21 shows the time-dependent changes in the acceleration of the low-speed impact, the displacement of the exterior member deformation sensor, and the electrical resistance value in the second experiment. As shown in FIG. 21, in the case of a low-speed impact of pressing with the palm, no acceleration occurs. However, the electrical resistance value changed in proportion to the deformation amount of the exterior member deformation sensor. Thus, the exterior member deformation sensor of the present invention can detect bending deformation even with a low-speed impact.

It is a schematic diagram which shows the electroconductive path before the load application of the sensor main body in this invention. It is a schematic diagram which shows the conductive path after the load application of the sensor main body. It is a schematic diagram of the percolation curve in an elastomer composition. (A) is a permeation | transmission top view of the vehicle by which the exterior member deformation | transformation sensor of 1st embodiment is arrange | positioned. FIG. 2B is a transparent side view of the vehicle. It is a permeation | transmission perspective view of the front bumper vicinity of a vehicle. It is a reverse view of the bumper cover of the front bumper of a vehicle. It is VII-VII sectional drawing of FIG. 5 and FIG. FIG. 8 is an enlarged view in a circle VIII in FIG. 7. It is a permeation | transmission perspective view at the time of the door opening vicinity of the left front door of a vehicle. It is a reverse view of the front door outer panel of the left front door of a vehicle. It is XI-XI sectional drawing of FIG. 9 and FIG. It is a block diagram of a crew member protection system of a first embodiment. It is a circuit diagram of a front bumper sensor unit. It is a circuit diagram of a left front door sensor unit. It is a block diagram of a crew member protection system of a second embodiment. It is a circuit diagram of the bridge circuit of the passenger protection system. It is an arrangement plan of an exterior member deformation sensor in an example. It is a schematic diagram of the circuit incorporating the same sensor. It is a graph which shows the time-dependent change of the acceleration of a high-speed impact, the displacement of an exterior member deformation | transformation sensor, and an electrical resistance value. 20 is an enlarged graph illustrating the horizontal axis (time: 65 to 85 ms) in FIG. 19. It is a graph which shows the time-dependent change of the acceleration of a low-speed impact, the displacement of an exterior member deformation | transformation sensor, and an electrical resistance value.

Explanation of symbols

1: Occupant protection system 2: Front bumper sensor unit 20: Front bumper sensor (exterior member deformation sensor)
21: Bridge circuit 22: Amplifier 200: Electrode film portion 200a: Base film 200b: Cover film 200c: Long hole 201: Sensor body 201L: Left section 201R: Right section 202: Restraint film section (restraint member) 203: Connector 3L : Left front door sensor unit 3R: Right front door sensor unit 30L: Left front door sensor (exterior member deformation sensor)
30R: Right front door sensor (exterior member deformation sensor)
31L: Bridge circuit 32L: Amplifier 300: Electrode film part 300a: Base film 300b: Cover film 300c: Long hole 301: Sensor body 302: Restraint film part (restraint member) 303: Connector 4L: Left rear door sensor unit 4R: Right Rear door sensor unit 40L: Left rear door sensor (exterior member deformation sensor)
40R: Right rear door sensor (exterior member deformation sensor)
5: Rear bumper sensor unit 50: Rear bumper sensor (exterior member deformation sensor)
6: Crew protection ECU 60: CPU
600: A / D converter 601: RAM 602: ROM
61a: airbag driving circuit 61b: headrest driving circuit 62: bridge circuit 63: amplifier 70: airbag device 71: active headrest device 80: exterior member deformation sensor 81: acceleration sensor 801: sensor body 802A, 802B: electrode 803A , 803B: Conductor 9: Vehicle 90: Front bumper 900: Bumper cover 901: Energy absorber 902: Groove 903: Bumper reinforcement 904: Front side member 91L: Left front door 91R: Right front door 92L: Left rear door 92R: Right rear door 93: Rear bumper 910: Front door outer panel 911: Front door inner panel 912: Opening weather strip outer 913: Side outer panel 100: Sensor body 101: Eras Mar 102: Conductive filler A, B, M: Electrode a, b: Electrode R (AM), R (MB): Resistor r (ab): Resistor R1-R3, R10-R30: Resistor r1-r3: Resistor V1 , V2: Intermediate potential v1, v2: Intermediate potential V10, V20: Intermediate potential Vcc: Power supply voltage Vin: Power supply Vm: Voltmeter P: Conductive path P1: Conductive path

Claims (9)

An elastomer and a spherical conductive filler blended in the elastomer in a substantially single particle state and with a filling rate of 30 vol% or more and 65 vol% or less when the total volume of the sensor body is 100 vol%. An elastically deformable sensor body whose electric resistance monotonously increases as the amount of elastic deformation increases in all deformations caused by compression, extension, and bending with respect to a natural state that has no deformation;
An electrode connected to the sensor body and capable of outputting the electrical resistance,
The sensor body is made of an elastomer composition containing the elastomer and the conductive filler as essential components, and in the percolation curve representing the relationship between the blending amount of the conductive filler and the electrical resistance of the elastomer composition, The blending amount (saturated volume fraction: φs) of the conductive filler at the second inflection point at which the resistance change is saturated is 35 vol% or more,
An exterior member deformation sensor for a vehicle that is disposed on an exterior member that is exposed to the outside of the vehicle and that can detect deformation of the exterior member.   The vehicle exterior member deformation sensor according to claim 1, wherein the exterior member is at least one of a bumper cover and a door panel.   The vehicle exterior member deformation sensor according to claim 1, wherein the sensor body is elastically bendable. The sensor body includes a fixed surface fixed to the exterior member, and a back surface facing away from the fixed surface,
The vehicle exterior member deformation sensor according to claim 3, wherein a restraining member for restraining elastic deformation of the back face is disposed on the back face. The sensor body includes a fixed surface fixed to the exterior member, and a back surface facing away from the fixed surface,
The vehicle exterior member deformation sensor according to claim 3, wherein the back surface is exposed. The sensor body has a long shape,
The vehicle exterior member deformation sensor according to claim 1, wherein a plurality of the electrodes are arranged along a longitudinal direction of the sensor body.   The vehicle exterior member deformation sensor according to any one of claims 1 to 6, wherein the conductive filler is carbon beads.   The vehicle exterior member deformation sensor according to any one of claims 1 to 7, wherein an average particle diameter of the conductive filler is 0.05 µm or more and 100 µm or less. 9. The elastomer according to claim 1, wherein the elastomer includes one or more selected from silicone rubber, ethylene-propylene copolymer rubber, natural rubber, styrene-butadiene copolymer rubber, acrylonitrile-butadiene copolymer rubber, and acrylic rubber. A vehicle exterior member deformation sensor according to claim 1.

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