JP4728705B2 - Shock detection optical fiber sensor and load concentration plate - Google Patents

Description

  The present invention relates to an impact detection optical fiber sensor for detecting an impact, a manufacturing method thereof, and a load concentrating plate.

  The impact detection sensor is provided in a vehicle such as an automobile, and is for detecting (sensing) an impact at the time of collision with another vehicle or an obstacle.

  As an impact detection sensor, an electric sensor that includes a pressure sensor, an acceleration sensor, or a strain gauge and detects an impact by observing changes in pressure, acceleration, or strain measured by the sensors is generally known. An optical fiber type that includes an optical fiber made of glass (quartz or the like) or plastic and detects an impact by observing a change in the amount of light transmitted through the optical fiber is generally known.

  As an optical fiber type impact detection sensor, an optical fiber is spirally wound around the outer circumference of a soft cylindrical body, and when the cylindrical body is deformed by impact, the bending loss increases due to the reduction in the bending radius of the optical fiber. There is something that detects impact. Some optical fibers are sandwiched by corrugated plates and an impact is detected by a change in bending loss or compression loss of the optical fiber. This type of optical fiber type impact detection sensor is also described in Patent Document 1.

JP-T-2002-531812

  By the way, among the above-described conventional shock detection sensors, the electric type sensor detects the shock and the electric signal detected by the sensor is easily affected by electromagnetic noise, and distinguishes between the electric signal to be detected and the electromagnetic noise. There was a problem that it may become difficult. In addition, the electrical signal has a problem that transmission loss is large.

  In order to solve these problems, the present applicants have previously proposed an impact detection optical fiber sensor using an optical fiber that is not easily affected by electromagnetic noise and has a small transmission loss (Japanese Patent Application No. 2004-261232). .

  As shown in FIG. 7, the impact detection optical fiber sensor 70 includes an optical fiber 71 for detecting impact, a light source (not shown) connected to one end of the optical fiber 71, and the other end of the optical fiber 71. A connected light receiver (not shown) and a load concentrating plate 72 provided along the longitudinal direction of the optical fiber 71 are provided. The optical fiber 71 and the load concentration plate 72 are covered and integrated with a molding material 73, and the optical fiber 71, the load concentration plate 72, and the molding material 73 constitute a sensor unit 74.

  A plurality of protrusions 75 are formed on one surface (the upper side in FIG. 7) of the load concentration plate 72 at predetermined intervals along the longitudinal direction of the optical fiber 71. The heights of the protrusions 75 are all equal, and the optical fiber 71 and the protrusions 75 are in contact with each other.

  When an impact load is applied to the sensor unit 74 due to a collision with another vehicle or an obstacle, the optical fiber 71 is pressed against the projection 75 side of the load concentrating plate 72 to bend or compress. Then, since bending loss and compression loss corresponding to the impact occur in the optical fiber 71, the presence / absence and magnitude of the impact can be detected from the loss amount. The amount of loss of the optical fiber 71 can be measured by observing a change in the amount of transmitted light transmitted through the optical fiber 71.

  However, the impact detection optical fiber sensor 70 shown in FIG. 7 has a problem that the detection sensitivity varies depending on the direction in which the impact is applied. That is, when an impact is applied with an inclination with respect to the front surface of the sensor unit 74 (upper side in FIG. 7), the optical fiber 71 is slightly displaced in the lateral direction (width direction) of the load concentration plate 72, and the impact is detected by the sensor unit. Compared with the case where the optical fiber 71 is applied straight from the front of 74, the force for pressing the optical fiber 71 against the projection 75 side of the load concentration plate 72 is reduced. Therefore, depending on the impact application direction, bending and compression acting on the optical fiber 71 may be insufficient, and the impact may be underestimated.

  Therefore, an object of the present invention is to provide an impact detection optical fiber sensor that can suppress variations in detection sensitivity due to a shift in the direction of impact application.

To achieve the above object, the invention of claim 1 is directed to an optical fiber for detecting an impact, a light source connected to one end of the optical fiber, and a light receiver connected to the other end of the optical fiber. , Bei example the load concentration plate having a plurality of projections in contact with the provided the optical fiber at a predetermined distance along the longitudinal direction of the optical fiber, in the projection, in order to prevent lateral displacement of the optical fiber In the impact detection optical fiber sensor having the groove, the groove has a contact surface that comes into surface contact with the outer periphery of the optical fiber.

According the invention of claim 2 is a further optical fiber impulse sensor according to claim 1 Symbol mounting comprising a molding material covering the optical fiber and the load concentration plate.

A third aspect of the present invention, along the longitudinal direction of the optical fiber have a plurality of projections in contact with the provided the optical fiber at a predetermined distance, in the projection, in order to prevent lateral displacement of the optical fiber A load concentrating plate in which a groove is formed, wherein the groove has a contact surface that comes into contact with the outer periphery of the optical fiber by surface contact .

  According to the present invention, there is an excellent effect that variation in detection sensitivity due to displacement in the direction of impact application can be suppressed.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  The impact detection optical fiber sensor of the present embodiment is provided in a vehicle such as an automobile, and is for detecting the presence / absence and magnitude of an impact at the time of collision with another vehicle or an obstacle.

  FIG. 1 is a schematic view of an impact detection optical fiber sensor including a load concentration plate according to an embodiment of the present invention. 2A is a side sectional view, FIG. 2B is a sectional view taken along line IIb-IIb in FIG. 2A, and FIG. 2C is a sectional view taken along IIc in FIG. It is -IIc sectional view taken on the line. FIG. 3 shows a load concentrating plate, (a) is a plan view, (b) is a front view, and (c) is a side sectional view.

  As shown in FIG. 1, an impact detection optical fiber sensor 1 of the present embodiment includes a sensor unit 3 having a plastic optical fiber (hereinafter referred to as POF) 2 for detecting an impact, and a light source 4 connected to one end of the POF 2. And a light receiver 5 connected to the other end of the POF 2. In the present embodiment, the POF 2 is arranged in a U-shaped folded shape, and the sensor portions 3 are respectively formed on the straight portions of the POF 2. The light source 4 and the light receiver 5 are connected to signal lines 6 that connect the light source 4 and the light receiver 5 to the outside of the sensor, respectively.

  In this embodiment, a heat-resistant plastic optical fiber (hereinafter referred to as HPOF) having heat resistance is used as POF2. Further, a light emitting element (hereinafter referred to as LED) such as a semiconductor laser or a light emitting diode was used as the light source 4, and a light receiving element (hereinafter referred to as PD) such as a photodiode was used as the light receiver 5. Further, an electric signal line such as a metal signal line was used as the signal line 6. Here, since these LED 4, PD 5, and electric signal line 6 are arranged in a place where no impact is applied, it is also possible to have a structure that shields electromagnetic noise.

  As shown in FIG. 2, the HPOF 2 of the present embodiment includes a core portion 7 having a substantially circular cross section for propagating light, and a clad portion 8 having a substantially circular cross section provided so as to cover the outer periphery of the core portion 7. It consists of and. The clad portion 8 is provided concentrically with the core portion 7.

  As the core portion 7, a synthetic resin excellent in heat resistance (for example, an acrylic resin, a cross-linked acrylic resin (thermosetting acrylic resin), or a silicone resin) can be used. As the clad portion 8, a synthetic resin (for example, a fluorine-based resin such as an ethylene propylene resin) having a refractive index lower than that of the core portion 7 and excellent in heat resistance, water resistance, and mechanical properties is used. it can.

  The sensor unit 3 includes a load concentration plate 10 provided so as to extend along the longitudinal direction of the HPOF 2, and a mold material 11 that covers the HPOF 2 and the load concentration plate 10 and integrates them. . The load concentrating plate 10 is formed with a plurality of protrusions 12 that come into contact with the HPOF 2 at predetermined intervals along the longitudinal direction of the HPOF 2 so as to support an impact load applied to the HPOF 2. As the load concentration plate 10, a material harder than HPOF 2 such as iron (for example, cold rolled steel plate), hard plastic, brass, or stainless steel can be used. Further, as the molding material 11, a synthetic resin (for example, silicone rubber) that is softer than HPOF2 and has flexibility can be used.

  As shown in FIG. 3, the load concentrating plate 10 of the present embodiment has a connection formed between a plurality of substantially I-shaped holes 13 formed at predetermined intervals in the longitudinal direction and the adjacent holes 13. And a projecting portion 15 formed at both ends of the connecting portion 14 and extending in the longitudinal direction. The connecting portion 14 and the protruding portion 15 constitute the protrusion 12.

  Grooves 16 for preventing lateral displacement of HPOF 2 (shift in the width direction of the load concentration plate 10) are formed in the protrusion 12 along the longitudinal direction of the load concentration plate 10. The groove 16 has a contact surface 17 that comes into contact with the outer periphery of the HPOF 2 by surface contact (see FIG. 3B). In the present embodiment, the contact surface 17 abuts on the outer periphery of the HPOF 2 by surface contact by forming the contact surface 17 into a cross-sectional R shape that is curved with a radius of curvature substantially equal to the radius of the HPOF 2. Note that the contact surface 17 may be formed in a cross-sectional R shape that is curved with a radius of curvature (slightly) larger than the radius of the HPOF 2.

  A planar portion 16a having a planar shape in a side view is formed on the bottom portion at the center in the longitudinal direction of the groove 16 (see FIG. 3C). Further, at the bottoms at both ends in the longitudinal direction of the groove 16, an R-shaped portion 16b having an R shape in a side view is formed to prevent the HPOF2 from being cut when the HPOF2 is bent (FIG. 3C). )reference).

  Here, in this embodiment, the HPOF 2 having a core part 7 having a diameter d1 of 1.5 mm and a clad part 8 having a diameter d2 (that is, a diameter of HPOF2) of 2.2 mm is used. In this case, the shape of the load concentration plate 10 is such that the thickness (plate thickness) T1 is in the range of 0.6 to 2 mm (1.5 mm in this embodiment), and the width (plate width) W is in the range of 5 to 14 mm. Within the range (10 mm in the present embodiment), the length L of the planar portion 16a is within the range of 3 to 5 mm (5 mm in the present embodiment), and the pitch P of the planar portion 16a is within the range of 12.5 to 20 mm (this In this embodiment, the radius of curvature R1 of the R portion 16b is in the range of 1 to 2 mm (1.8 mm in the present embodiment), and the radius of curvature R2 of the contact surface 17 is the radius of the cladding portion 8 (d2 / 2). And the depth D of the groove 16 is preferably in the range of 0.1 to 1.1 mm (0.7 mm in this embodiment).

  Further, it is desirable that the molding material 11 has a thickness T2 of 5 mm or less (5 mm in the present embodiment) and a hardness within a range of 35 ° to 75 ° (around 53 ° in the present embodiment). At that time, it is desirable that the thickness a of the molding material 11 above the HPOF 2 to which the impact is applied is formed to be thicker than the thickness b of the molding material 11 below the load concentration plate 10. In this embodiment, the thickness a of the mold material 11 above the HPOF 2 is set to about twice the thickness b of the mold material 11 below the load concentration plate 10.

  Next, a manufacturing method of the impact detection optical fiber sensor 1 will be described.

  In this embodiment, when the HPOF 2 and the load concentrating plate 10 are covered with the mold material 11 in order to manufacture the impact detection optical fiber sensor 1, the extrusion method is used. In this extrusion method, the HPOF 2 and the load concentrating plate 10 are inserted from the insertion port of an extruder (not shown), and the HPOF 2 and the load concentrating plate 10 covered with raw rubber (mold material 11) are moved to the discharge port side of the extruder. And extrude. When performing this extrusion method, a mandrel (not shown) for controlling (molding) the shape of the molding material 11 is provided on the discharge port side of the extruder. Therefore, when performing the extrusion method, it is necessary to reduce a dimensional error (positional deviation) between the load concentration plate 10 and the core plate.

  Therefore, in this embodiment, when the HPOF 2 and the load concentrating plate 10 are covered with raw rubber, the HPOF 2 is engaged with the groove 16 of the load concentrating plate 10 and the HPOF 2 and the load concentrating plate 10 are connected to the insertion port side of the extruder. And a guide member (not shown) such as a mandrel is engaged with the groove 16 of the load concentration plate 10 on the upstream side in the pushing direction so that the load concentration plate 10 is guided by the guide member. I did it. And if the load concentration board 10 is coat | covered with raw rubber over the full length, they will be left at high temperature, and raw rubber will be hardened. By doing so, it is possible to reduce the dimensional error between the load concentration plate 10 and the core plate, and also to ensure the positional accuracy of the HPOF 2 with respect to the load concentration plate 10 and to reduce manufacturing variation (that is, It is possible to manufacture the impact detection optical fiber sensor 1 with small individual difference and good dimensional accuracy.

  Next, the operation of this embodiment will be described.

  The light output from the LED 4 is incident on the PD 5 via the HPOF 2. The transmitted light amount (light intensity) detected by the PD 5 is transmitted to the outside of the sensor as an electric signal through the electric signal line 6.

  When an impact load is applied to the sensor unit 3 due to a collision with another vehicle or an obstacle, the HPOF 2 is bent between the projections 12 of the load concentration plate 10 as shown in FIG. 4, or the projection as shown in FIG. 12 is pressed and compressed. Then, bending loss (microbend loss) or compression loss corresponding to the impact occurs in HPOF2, and the amount of transmitted light that propagates through HPOF2 changes according to the bending loss or compression loss as shown in FIG.

  Here, in this embodiment, a groove 16 is provided in the protrusion 12 of the load concentration plate 10, and the HPOF 2 is engaged with the groove 16. For this reason, even if the impact is applied to the front surface of the sensor unit 3 (upper side in FIG. 2) as shown by the arrow in FIG. 5, the HPOF 2 is pressed against the inner periphery of the groove 16. It is possible to suppress variations in detection sensitivity due to deviations in the application direction.

  Further, in this embodiment, since the groove 16 has the contact surface 17 that comes into surface contact with the outer periphery of the HPOF 2, the HPOF 2 can be held in surface contact with the groove 16, and an impact load is applied. It is possible to prevent stress concentration of the HPOF2 from occurring and prevent the HPOF2 from breaking.

  On the other hand, when time elapses from the impact application, as shown in FIG. 6, the shape of HPOF 2 is restored by the elastic force of the molding material 11, so that the impact detection optical fiber sensor 1 can be used repeatedly.

  By the way, the thickness of the sensor unit 3 that can be mounted (thickness T2 of the molding material 11 (see FIG. 3B)) may be limited due to the layout of the vehicle or the like. In that case, conventionally, although the load resistance (impact resistance) of the sensor unit 3 is lowered, the thickness T2 of the molding material 11 has to be reduced. However, according to the present embodiment, since the lower part of HPOF 2 is immersed in the groove 16, the mold material 11 above the HPOF 2 is not increased without increasing the thickness of the entire sensor unit 3 (thickness D of the entire mold material 11). Thickness a, or only the thickness b (see FIG. 3B) of the molding material 11 below the load concentration plate 10 can be increased, and the load resistance (impact resistance) of the sensor unit 3 can be increased. Can be improved.

  The present invention is not limited to the embodiment described above.

  For example, in the above-described embodiment, the optical fiber 2 is arranged in a U-shaped folded shape, but this is not a limitation. For example, the optical fiber 2 may be arranged linearly.

  Moreover, the cross-sectional shapes of the core part 7, the clad part 8, and the groove 16 are not limited to the above-described embodiment. For example, the core part 7, the clad part 8, and the groove | channel 16 may be formed in other shapes, such as cross-sectional rectangular shape and cross-sectional elliptical shape.

  Further, the shape of the protrusion 12 is not limited to the above-described embodiment. In other words, it is only necessary that the plurality of protrusions 12 be formed along the longitudinal direction of the optical fiber 2. For example, each protrusion 12 may be formed in a mountain shape protruding above the load concentration plate 10 (see FIG. 7). ).

  In the above-described embodiment, a plastic optical fiber is used as the optical fiber 2, but a glass optical fiber can also be used as the optical fiber 2. However, due to the characteristics of glass, the glass optical fiber is likely to be deteriorated in mechanical strength by bending or compression, and the glass optical fiber may be cut when an impact is applied. For this reason, as the optical fiber 2, it is desirable to use a plastic optical fiber that is unlikely to cause a decrease in mechanical strength as in the present embodiment.

  Furthermore, in the above-described embodiment, an electric signal line is used as the signal line 6, but this is not a limitation. For example, an optical signal line such as an optical fiber may be used as the signal line 6.

It is the schematic of the impact detection optical fiber sensor provided with the load concentration board which concerns on one Embodiment of this invention. The sensor part is shown, (a) is a side sectional view, (b) is a sectional view taken along line IIb-IIb in FIG. 2 (a), and (c) is a sectional view taken along line IIc-IIc in FIG. 2 (a). It is arrow sectional drawing. A load concentration board is shown, (a) is a top view, (b) is a front view, (c) is a side sectional view. It is side surface sectional drawing of a sensor part which shows the state by which the optical fiber was bent by the impact application. It is front sectional drawing of a sensor part which shows the state by which the optical fiber was compressed by the impact application. It is a graph which shows the time change of the transmitted light quantity at the time of an impact application. The impact detection optical fiber sensor which the present applicants proposed previously is shown, (a) is side sectional drawing, (b) is a VIIb-VIIb arrow sectional view of Drawing 7 (a), (c ) Is a sectional view taken along line VIIc-VIIc in FIG.

Explanation of symbols

1 Optical fiber sensor for impact detection 2 Optical fiber (POF, HPOF)
4 Light source (LED)
5 Receiver (PD)
10 Load Concentration Plate 11 Mold Material 12 Projection 16 Groove 17 Contact Surface

Claims (3)

An optical fiber for detecting an impact, a light source connected to one end of the optical fiber, a light receiver connected to the other end of the optical fiber, and a predetermined interval along the longitudinal direction of the optical fiber provided Bei example the load concentration plate having a plurality of projections abutting on the optical fiber, in the projection, in the optical fiber impulse sensor having grooves for preventing the lateral displacement of the optical fiber,
The impact detection optical fiber sensor , wherein the groove has a contact surface that comes into contact with the outer periphery of the optical fiber by surface contact . Further optical fiber impulse sensor according to claim 1 Symbol mounting comprising a molding material covering the optical fiber and the load concentration plate. Along the longitudinal direction of the optical fiber have a plurality of projections in contact with the provided the optical fiber at a predetermined distance, in the projection, load concentration plate having grooves for preventing the lateral displacement of the optical fiber In
The load concentrating plate , wherein the groove has a contact surface that contacts the outer periphery of the optical fiber by surface contact .

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