JP4783097B2 - Shock detection optical fiber sensor - Google Patents

Description

  The present invention relates to an impact detection optical fiber sensor for sensing an impact caused by an object to be measured.

  An impact detection sensor that is provided in a vehicle such as an automobile and detects an impact when the vehicle collides with another vehicle or an obstacle has been studied (for example, Patent Document 1).

  As a conventional impact detection sensor, there is one in which an optical fiber is wound around a support having elasticity, a light emitting element is connected to one end of the optical fiber, and a light receiving element is connected to the other end (for example, Patent Document 2). When an impact is applied to this sensor, the support is deformed, and the optical fiber is deformed at the same time. This deformation changes the amount of light passing through the optical fiber, and an impact is detected from this change.

  As this optical fiber, a plastic fiber (POF) can be used (for example, Patent Document 3).

JP-T-2002-531812 Japanese Patent Laid-Open No. 9-26370 JP-A-5-249352

  When a large impact is applied to the sensor, there is an impact resistance problem that the POF is cut.

  On the other hand, in order to prevent the POF from being cut, it is conceivable to improve the impact resistance by making it difficult to apply a load to the POF due to an impact. However, in this case, there is a problem that a minute impact cannot be detected. .

  Therefore, an object of the present invention is to provide an impact detection optical fiber sensor that improves the sensor sensitivity.

  Another object of the present invention is to provide an impact detection optical fiber sensor having impact resistance and improved sensor sensitivity.

The present invention has been devised to achieve the above object. The invention of claim 1 is a wave having a plastic optical fiber and a plurality of protrusions attached to one or both sides of the plastic optical fiber in the longitudinal direction. and biasing plate, a sensor unit and the plastic optical fiber with the above wave plate becomes covered with molding material, a light emitting element connected to one end of the plastic optical fiber, which is connected to the other end of the plastic optical fiber The impact detection optical fiber sensor includes a light receiving element, and the plurality of protrusions are configured by combining smooth R-shaped protrusions having different heights in at least two stages .

According to a second aspect of the invention, the plastic optical fiber core diameter of 1.5 mm, to the optical fiber thickness of 0.35mm of clad layer, the thickness of the clad layer is 15μm thin of claim 1 It is an impact detection optical fiber sensor.

According to a third aspect of the present invention, the cross section of the core and the clad layer of the plastic optical fiber is elliptical so that the minor axis is orthogonal to the corrugated plate. The shock detection optical fiber sensor according to the first or second aspect It is.

  According to the present invention, it is possible to improve sensor sensitivity while ensuring impact resistance.

  Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

  FIG. 1A is a side view of a main part of an impact detection optical fiber sensor showing a preferred first embodiment of the present invention, and FIG. 1B is a transverse sectional view thereof.

  As shown in FIGS. 1A and 1B, an impact detection optical fiber sensor 1 according to the first embodiment includes a sensor unit 3 for detecting an impact having a plastic optical fiber (POF) 2. And a light emitting element such as a semiconductor laser (not shown) connected to one end of the POF 2 and a light receiving element such as a photodiode (not shown) connected to the other end of the POF 2. In the present embodiment described below, a heat-resistant plastic optical fiber (HPOF) having heat resistance is used as POF2.

  The POF 2 has an optical transmission characteristic that changes in response to an impact. The POF 2 is configured by covering the outer periphery of a core 4 having a circular cross section with a clad layer 5, and the cross section is formed concentrically. As the core 4, a synthetic resin excellent in heat resistance, for example, an acrylic resin, a crosslinked acrylic resin (thermosetting acrylic resin), or a silicone resin is used. As the cladding layer 5, a synthetic resin excellent in heat resistance, water resistance, and mechanical properties, for example, a fluorine resin such as a fluoroethylene propylene resin (FEP) is used.

  Now, in order to improve the sensor sensitivity, the sensor 1 has the cladding layer 5 of the POF 2 as thin as possible within a range in which light does not leak from the POF 2 and the POF 2 has a sufficient strength. It is thinner than the clad layer by several percent or more, preferably 4% or more.

  In POF2, for example, the thickness of the cladding layer 5 is reduced by 15 μm compared to a general POF having a core diameter of 1.5 mm and a cladding layer thickness of 0.35 mm. In this case, the thickness of the cladding layer 5 is 0.335 mm.

  The sensor unit 3 is composed of the POF 2 and the corrugated plate 6 in a state where the corrugated plate 6 having a plurality of protrusions is attached to one side of the POF 2 (the back surface in FIGS. 1A and 1B). It is covered with a molding material 7 such as resin. Here, as a method of covering with the molding material, the POF 2 and the corrugated plate 6 may be integrated and molded integrally with the molding material, or the corrugated plate 6 is first covered with the molding material, and then the POF 2 is used as the molding material. You may make it insert in the provided space.

  The corrugated plate 6 has a plurality of planar protrusions 8 as protrusions formed on the surface thereof at regular intervals along the longitudinal direction. The planar protrusion 8 has a substantially trapezoidal shape in a side view, and is configured by forming a planar portion 10 on the upper part of the trapezoid. The heights of the planar projections 8 are the same, and when the corrugated plate 6 is attached to the POF 2, the POF 2 and the planar portions 10 come into contact with each other.

  As the shape of the corrugated plate, R-shaped planar protrusions in which smooth R-shaped portions 9 having a constant radius of curvature are formed at both ends in the longitudinal direction of the planar portion 10 of the planar protrusion 8 may be used.

  As the corrugated plate 6, for example, hard plastic (Rockwell hardness (JIS K 7202) R scale 118, M scale of about 80), brass (BS), stainless steel (SUS), or the like is used.

  The operation of the first embodiment will be described.

  In the sensor 1, when an impact (or load) is applied to the sensor unit 3 (from above in FIGS. 1A and 1B), the POF 2 is pressed against the planar protrusion 8 of the corrugated plate 6, and the core When 4 is deformed, bending loss or compression loss corresponding to the impact occurs in POF 2. The amount of bending loss or compression loss is incident on the light emitting element from one end of POF2 and received by the light receiving element on the other end of POF2, and the change (attenuation) in the amount of transmitted light transmitted through POF2 is observed. To measure. The presence / absence and magnitude of an impact applied to the sensor unit 3 are determined from the measured loss amount and detected.

  The attenuation of the transmitted light amount of the POF 2 occurs when the core 4 is deformed, and the core 4 is deformed when the POF 2 is crushed by the planar protrusion 8. Since the clad layer 5 is softer than the core 4 (lower elastic modulus), the clad layer 5 starts to deform first, and the core 4 begins to deform with a delay. If the clad layer is thick, a delay occurs in the deformation of the core, and the sensor sensitivity decreases.

  However, in the sensor 1, the cladding layer 5 is made as thin as possible within a range in which light does not leak from the POF 2 and the POF 2 has sufficient strength. Specifically, the cladding layer 5 is made 4% or more thinner than a cladding layer of a general POF. Therefore, the transmitted light amount of POF 2 can be attenuated with a small impact (low load), and the sensor sensitivity is high. This is the same even if the corrugated plate having only the R-shaped projection described in the background art is used instead of the corrugated plate 6 having the planar-shaped projection 8.

  For example, by using POF 2 in which the thickness of the cladding layer 5 is reduced by 15 μm, compared to a general POF having a core diameter of 1.5 mm and a cladding layer thickness of 0.35 mm, the static load on the sensor unit 3 can be reduced. When applied, the sensor 1 has a sensor sensitivity (loss, dB) about 1.5 times that of the conventional sensor.

  Furthermore, in the sensor 1, since all the projections of the corrugated plate 6 are planar projections 8, when a large impact is applied to the sensor unit 3, stress applied to the POF 2 is dispersed by the planar portion 10 of the planar projections 8. POF2 is difficult to cut. That is, according to the sensor 1, it is possible to improve sensor sensitivity while ensuring impact resistance.

  The same applies to the case of using a planar projection having no R-shaped portion 9 as the projection. However, when the planar protrusion 8 is used, the stress applied to the POF 2 in the R-shaped portion 9 is more dispersed than in the case where the planar protrusion without the R-shaped portion 9 is used, so that the POF 2 is less likely to be cut.

  A second embodiment will be described.

  As shown in FIG. 2, the impact detection optical fiber sensor 21 is formed by processing a general POF having a concentric cross section instead of the POF 2 of FIG. 1, and corrugating the cross section of the core 24 and the cladding layer 25. The sensor unit 23 is configured by using a POF 22 molded in an elliptical shape so that the minor axis is orthogonal to the plate 6. Other configurations of the sensor 21 are the same as those of the sensor 1 of FIG.

  As a molding method of the POF 22, for example, a corrugated plate 6 is attached to one side of a general POF, the POF is heated to a high temperature (about 150 ° C.), and both the core and the clad are softened and softened. A method including a step of compressing with a flat plate from the upper side in FIG. 2 and returning to normal temperature while the POF is compressed, and molding a POF 22 having an elliptical cross section is employed.

  In the POF 22, for example, the thickness of the clad layer 25 in the minor axis direction is made 15 μm thinner than a general POF having a core diameter of 1.5 mm and a clad layer thickness of 0.35 mm. In this case, the thickness of the cladding layer 25 in the minor axis direction is 0.335 mm.

  Also with this sensor 21, the thickness in the minor axis direction of the cladding layer 25 is made as thin as possible within a range in which light does not leak from the POF 22 and the POF 22 has sufficient strength. can get.

  Further, in the sensor 21, since the cross section of the POF 22 is elliptical, the contact area between the POF 22 and the corrugated plate 6 is larger than that of the POF having a circular cross section, and the sensor 21 is oblique (parallel to the short axis of the POF 22). The POF 22 remains on the surface of the corrugated plate 6 even when a load is applied in the direction (not in the direction) (the POF 22 is not easily displaced from the surface of the corrugated plate 6), so that the core 24 can be efficiently deformed. That is, the sensor 21 has higher sensor sensitivity than the sensor 1 of FIG.

  A third embodiment will be described.

  As shown in FIG. 3A and FIG. 3B, the impact detection optical fiber sensor 31 includes a planar protrusion 8 and an R-shaped protrusion 32 as protrusions instead of the corrugated plate 6 of FIG. The sensor unit 33 is configured by using a corrugated plate 36 formed by alternately combining two types of protrusions at regular intervals along the longitudinal direction.

  As described above, the planar protrusion 8 has a substantially trapezoidal shape in a side view, the smooth R-shaped portion 9 having a constant radius of curvature is formed at both ends in the longitudinal direction, and the planar portion 10 is formed at the central portion. Configured. The R-shaped protrusion 32 is a smooth protrusion having a substantially semicircular shape in a side view and a constant radius of curvature. As the protrusions, instead of the planar protrusion 8, a planar protrusion in which a planar part is formed in the longitudinal direction (the R-shaped part 9 is not formed) may be used.

  As the sensor 31, the POF 22 of FIG. 2 may be used instead of the POF 2, or a general POF may be used. Other configurations of the sensor 31 are the same as those of the sensor 1 of FIG.

  In the structure of the sensor 31, since the elastic coefficient of the molding material 7 is smaller than that of the POF 2 and the corrugated plate 36, the load applied to the POF 2 is mainly supported by the corrugated plate 36.

  When the impact is applied, the planar protrusion 8 has a larger area to receive the load than the R-shaped protrusion 32, and therefore the load applied to the unit area is reduced. Therefore, the sensor 31 has a larger impact when the POF 2 is cut than the conventional sensor using the corrugated plate having only the R-shaped protrusion, and the impact resistance is improved.

  Here, if the corrugated plate has only the planar protrusion 8, the impact resistance is improved, but the loss of the POF 2 is reduced, and the sensor sensitivity may be lowered. Therefore, in the sensor 31, desired sensor sensitivity and impact resistance can be obtained by using the corrugated plate 36 in which the planar projection 8 for improving the impact resistance and the R-shaped projection 32 for improving the sensor sensitivity are alternately formed. Is obtained. That is, the sensor 31 is a sensor in which both sensor sensitivity and impact resistance are balanced.

  Further, the impact resistance of the sensor 31 can be increased by increasing the radius of curvature of the R-shaped protrusion 32 as well. In the R-shaped protrusion 32, as the load is applied and the POF 2 is deformed, the area that receives the load increases. However, as the radius of curvature increases, the amount of increase in the area that receives the load increases.

  Further, in the sensor 31, the radius of curvature of the R-shaped portion 9 of the planar protrusion 8, the length of the planar portion 10, the pattern (for example, the interval between the protrusions) and / or the radius of curvature of the R-shaped protrusion 32, and the pattern are used as sensor sensitivity. By adjusting (setting) in advance according to the impact resistance, desired sensor sensitivity and impact resistance can be obtained.

  A fourth embodiment will be described.

  As shown in FIGS. 4A and 4B, the impact detection optical fiber sensor 41 has an R-shaped protrusion (high protrusion) 42H having a high height as a protrusion instead of the corrugated plate 6 of FIG. And corrugation formed by alternately combining two types of protrusions having different heights in two stages, an R-shaped protrusion (low protrusion) 42L having a height lower than that of the high protrusion 42H, along the longitudinal direction. The sensor unit 43 is configured using the plate 46.

  The heights of the high protrusions 42H are the same. When the corrugated plate 46 is attached to the POF 2, the POF 2 and the top of the high protrusions 42H are in contact with each other. The height of each low protrusion 42L is also the same.

  As the sensor 41, the POF 22 of FIG. 2 may be used instead of the POF 2, or a general POF may be used. Other configurations of the sensor 41 are the same as those of the sensor 1 of FIG.

  In the sensor 41, when a shock is applied when the impact is applied, the POF 2 comes into contact with only the high protrusion 42H, and the load received by the POF 2 due to the impact is supported only by the high protrusion 42H.

  In addition, as shown in FIG. 5, when the impact is large as in the case of applying a large impact S, at the beginning of load application, POF2 comes into contact with only the high protrusion 42H and then is crushed. When the deformation is greater than the difference between the height and the height of the low protrusion 42L, the high protrusion 42H and the low protrusion 42L come into contact. When POF2 comes into contact with the high protrusions 42H and the low protrusions 42L, the area that receives the load increases, so the load applied to the unit cross-sectional area of POF2 is reduced.

  Thus, in the sensor 41, the load applied to the POF 2 is supported by a small area (only the high protrusion 42H) in the case of a minute impact, and the load applied to the POF 2 is large (the high protrusion 42H and the low protrusion) in the case of a large impact. 42L). Therefore, the sensor 41 can detect a minute impact with high sensitivity, and the impact resistance when a large impact is applied is improved. That is, the sensor 41 is a sensor in which the sensor sensitivity and the impact resistance are well balanced.

  Further, in the sensor 41, a desired sensor can be obtained by adjusting in advance the curvature radius, height and pattern of the high protrusion 42H and the curvature radius, height and pattern of the low protrusion 42L in accordance with the sensor sensitivity and impact resistance. Sensitivity and impact resistance can be obtained.

  In addition, the sensor sensitivity and impact resistance can be adjusted more finely by changing the height of the protrusions not only in two stages but also in three or more stages.

  In the above-described embodiment, the example in which the corrugated plate is attached to one side of the POF has been described, but the corrugated plate may be attached to both sides of the POF. In this case, the sensor sensitivity is further improved.

FIG. 1A is a side view of a main part of an impact detection optical fiber sensor showing a preferred first embodiment of the present invention, and FIG. 1B is a transverse sectional view thereof. It is a cross-sectional view of the main part showing a second embodiment. FIG. 3A is a side view of the main part showing the third embodiment, and FIG. 3B is a cross-sectional view thereof. FIG. 4A is a side view of the main part showing the fourth embodiment, and FIG. 4B is a transverse sectional view thereof. It is a cross-sectional view of the main part of the impact detection optical fiber sensor shown in FIG. 4 when a large impact is applied.

Explanation of symbols

1 Impact detection optical fiber sensor 2 Plastic optical fiber (POF)
3 Sensor part 4 Core 5 Clad layer 6 Corrugated plate 7 Mold material

Claims (3)

A plastic optical fiber, a corrugated plate having a plurality of protrusions attached to one or both sides in the longitudinal direction of the plastic optical fiber, and a sensor unit that covers the plastic optical fiber and the corrugated plate with a molding material; includes a light emitting element connected to one end of the plastic optical fiber and a light receiving element connected to the other end of the plastic optical fiber, the plurality of projections are different in height from each other in at least two stages, An impact detection optical fiber sensor comprising a combination of smooth R-shaped protrusions . 2. The impact detection optical fiber sensor according to claim 1 , wherein the plastic optical fiber has a thickness of 15 [mu] m thinner than an optical fiber having a core diameter of 1.5 mm and a cladding layer thickness of 0.35 mm . 3. The impact detection optical fiber sensor according to claim 1, wherein a cross section of the core and the cladding layer of the plastic optical fiber is elliptical so that a short axis is orthogonal to the corrugated plate .

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