WO2008031836A1

WO2008031836A1 - Sensor strip

Info

Publication number: WO2008031836A1
Application number: PCT/EP2007/059560
Authority: WO
Inventors: Henryk Frenzel; Benjamin L' HÉNORET; Helmut Nowsch; Georg Osterholt
Original assignee: Continental Automotive Gmbh
Priority date: 2006-09-15
Filing date: 2007-09-12
Publication date: 2008-03-20
Also published as: DE102006043344B3

Abstract

The invention relates to a sensor strip comprising at least one optical waveguide (11) and a turning point. The turning point is optically coupled to the optical waveguide (11) at a first free end of the optical waveguide (11). The turning point is a prism (9).

Description

description

Sensorband

The invention relates to a sensor band that has at least one optical waveguide.

Research has shown that a high proportion of road deaths affects pedestrians. For this reason, legislative initiatives are underway aimed at making pedestrian protection devices compulsory in the event of a collision with a vehicle in modern motor vehicles.

A particularly high risk of injury to a pedestrian in the event of a collision with a vehicle is a very small distance between a typically easily ver ^¬ formable hood and a rigid engine block. The arrangement of more and more components in the engine compartment and very compact vehicles have to It ^follows that the engine compartment is densely packed with very rigid bodies. In the event of a collision with a pedestrian, so there is a high risk of severe head injuries if it collides with his head on the hood and thus comes in contact with the under-hood befindli ^¬ chen components.

A sufficiently large distance between the hood and the components arranged underneath it, for example, about 10 cm, however, can reduce the risk of injury strong because the hood can absorb the deformation sufficiently much Ener ^¬ energy and can brake the pedestrian so comparatively gently.

In order to increase safety for pedestrians in road traffic, for example, the Association of European Automobile Manufacturers (ACEA) has committed itself to the European Union authorities through measures in the vehicle sector to halve the number of road deaths in the area of pedestrians by 2010. One measure for this is the construction of vehicles with appropriately spaced hoods. Due to the required compactness of vehicles, however, this is often not possible.

In order to ensure sufficient damping in the event of a collision with a pedestrian, it has been proposed, in the event of a detected impact of a person on the vehicle, to raise the hood by more than 10 cm from its closed position so as to provide a sufficient range of deformation. A major challenge for such security systems is the need for them to be reliably ^¬ the one hand, but are also very cost-effective.

As an actuator for lifting the hood, for example, from an article in the journal "Automotive Engineer", April 2004, page 48 et seq., Known to provide a spring-based Aktu ^¬ ator whose spring is biased and is released in the event of a detected collision with the Follow this to raise the bonnet accordingly. Over it ^¬ out, however, py rotechnische actuators are also known from the above article.

CA 2 424 708 A1 discloses a method and apparatus for detecting a collision between a vehicle and an object. Optical fibers are arranged along a front bumper of the vehicle. The Lichtleit ^¬ fibers include in their fiber cladding light exit areas, which are arranged along the optical fibers. A collision leads to a bending of the optical fibers. The attenuation of the light transmitted in the optical fibers changes by the bending of the optical fiber when the optical fiber is bent in the light exit region. From the thus modulated light, a signal is obtained, which is processed in a signal processor. A safety device, eg for lifting a bonnet, can be activated in this way. The object of the invention is to provide a sensor tape, wel ^¬ Ches is simple and inexpensive to manufacture.

The object is solved by the features of the independent claims. Advantageous developments of the invention are characterized in the subclaims.

The invention is characterized by a sensor strip which has at least one optical waveguide and a reversal point on ^¬ and the reversal point is optically coupled to the at least one Lichtwel ^¬ lenleiter. The optical coupling between the reversal point and the at least one lightwave ^¬ conductor takes place at a first free end of the optical waveguide. The turning point is characterized by being a prism.

This has the advantage that the prism, as a reversal point, allows ^better design possibilities as a reversal point in the form of a loop. At a reversal point in the form of a loop, the sensor band is bent around the loop. In this context, it may be necessary to ensure with increased effort that the detachment of the at least one optical waveguide or of the sensor band from the loop is prevented. On the other hand, through the

Bending of the sensor band around the loop on an attenuation of the guided in the sensor strip light. In the case of a loop as a reversal point, furthermore, a minimum bending radius of the sensor strip is to be taken into consideration, whereby the size of the loop is fixed and can not be further reduced. In the case of a prism as a reversal point, the light guided in the sensor band is deflected, wherein the size of the prism can be substantially arbitrarily small. In a prism as a reversal point is essentially the attenuation of the overall sensor in bands led light, ie, light loss as a result of ex ^¬ clear curvature of the sensor tape is eliminated. A further advantage of the reversal ^{valves designed} as prisms is their very good optical properties with small dimensions. The reversal point can be very compact by the use of the prism. For example, the weight of the prism is reduced by half compared with the weight of a loop. The weight and thus the mass plays a significant role in the occurrence of vibration. The influence of the vibrations is considerably reduced by the use of the prism. The use of the prism is a technologically simple and priced extremely favorable Lö ^¬ solution.

In an advantageous embodiment, the at least one optical waveguide of the sensor band is designed as a pair of optical waveguides. The at least one optical waveguide pair has a first optical waveguide, which is arranged parallel to a second optical waveguide. The prism is arranged such that it optically couples the first optical waveguide to the second optical waveguide, to be precise at the respective first free ends of the first and second optical waveguides of the at least one optical waveguide pair. The use of the optical waveguide pair eliminates a curvature of the sensor band and also the consequent damping of the light guided in the sensor band. The advantage of the pair of optical waveguides is that light from the first optical waveguide is directed through the prism into the second optical waveguide of the pair of optical waveguides and an attenuation of the light in the pair of optical waveguides can be detected. For example, when the sensor strip is bent, the light is attenuated by the bending of the first optical waveguide of the optical waveguide pair in its light exit region. The thus modulated light is then transmitted by the second optical waveguide of the pair of optical fibers and obtained therefrom a signal.

In a further advantageous embodiment, the sensor band has an evaluation unit at a second free end of the at least one optical waveguide. The evaluation The unit is optically coupled to the second free end of the at least one optical waveguide or to the second free ends of the first and second optical waveguides of the at least one optical waveguide pair. By bending the optical waveguide in its light exit region, the light is attenuated in the optical waveguide. From the attenuated light a signal is obtained in the evaluation, which can be used for example to activate a safety device.

In a further advantageous embodiment, the evaluation unit has a light source and a light sensor. The evaluation unit is adapted to light in the first optical fiber of a fiber-optic cables couple terpaares from the light ^¬ source and couple light from the second light waveguide in the light sensor. The light of the light source is coupled into the first optical waveguide and has a wavelength and an intensity. After reflection in the prism, the light from the second optical waveguide is coupled out into the light sensor. The light sensor converts the light into an electric current. The signal thus obtained can be processed further in the evaluation unit.

The prism is characterized in that it is designed as a roof prism or a Porro prism. The light is reflected in a roof prism or the Porro prism by double reflection ^¬ . The roof prism or Porro prism deflects an incident light beam at an angle of 180 °, regardless of the angle of incidence of the light beam. Light rays are ^reflected back in the roof prism or porro prism in the opposite direction at the same angle.

Advantageously, the prism made of the plastic polymethyl methacrylate. Polymethyl methacrylate is a splitter ^¬ free and lightweight material, which has good cutting ability. Polymethyl methacrylate has a better Transmis ^¬ sion of light on when, for example, normal glass, it is elastic and impact resistant and thus weather and age ^¬ resistant.

In a further advantageous embodiment, the sensor band has a plurality of pairs of optical fibers. In this together ^¬ menhang it is advantageous when the sensor strip has a centrally located pair of optical waveguides. Further light ^¬ waveguide pairs are then symmetrically to the centrally arranged ^¬ optical waveguide pair growing spaced apart zueinan- arranged. This allows reflection of the light from the respective first optical waveguide into the second optical waveguide of the optical waveguide pair. If the Sen ^¬ sorband bent, for example, as a result of an impact ei ^¬ nes object, it is possible by a combination of all Sig--dimensional, which are obtained from the attenuation of the light of all Lichtwellenlei ^¬ terpaare, a three-dimensional image of the rebounding on ^¬ object to create. From this combination it is possible to reconstruct the depth and width of the sensor belt deflection and thereby distinguish between a small and a large object, for example the distinction between a stone and a child or an adult human being.

In a further advantageous embodiment, the prism is adapted to the light rays back into the same

Reflect optical fiber. The return of the light in the same optical waveguide leads to a considerable saving of material costs. The sensor band is reduced in size and thus also the space occupied by the sensor band when installed in, for example, a front bumper of a vehicle.

In this context, the evaluation unit has a light source ^¬, which is integrated in the light sensor. The light source and the light sensor form a unit, so that the coupling and decoupling of the light in the Lichtwellenlei ^¬ ter or from the optical waveguide at the same location is possible. In a further advantageous embodiment, the sensor band for pedestrian impact protection in automobiles is integrated. The sensor band detects, for example, the impact of a pedestrian and dampens the impact of the pedestrian on the car ^¬ mobile by activating a safety device which leads to lifting the hood.

Embodiments of the invention are explained below with reference to the schematic drawings. Show it:

FIG. 1 is a plan view of a vehicle;

2A shows an impact sensor device, FIG. 2B shows a second impact sensor device

FIG. 3 shows a reversal point of the sensor band,

FIG. 4 shows a third impact sensor device.

Elements of the same construction or function are provided across the figures with the same reference numerals.

A vehicle 1 has an impact sensor device 2 (FIG. 1). The impact sensor device 2 has a rich Sensierungsbe- 4 which is ^¬ arranged along a bumper 3 of the vehicle 1 at. By means of the Sensierungsbereichs 4 can detect a collision of an impacting object 5 on the sensor device ^¬ bulging. 2 The impact object 5 can be, for example, a pedestrian. Further, the vehicle has an evaluation unit 6, are evaluated in the delivered by the impact sensor device 2 measured signals, and is recognized on an impact of the impact object 5 according to the course of the jewei ^¬ time measurement signal and, if appropriate, initiated action for protecting the impact object 5 or of the vehicle occupants become. These measures may be, for example, a slight lifting of a hood of the vehicle 1 or an ignition of one or more airbags. The impact sensor device 2 comprises the evaluation unit 6, a sensor band 7 and a prism 9 (FIG. 2A). The Auswer ^¬ teeinheit 6 is disposed at one end of the sensor belt 7 and includes optical and electrical coupling points, a

Light source 12 and a light sensor 13, for forming Bezie ^¬ hung as coupling light into or out of the sensor 7. This band implies that the sensor tape 7 must be deflected at a different location. The sensor band 7 has a prism 9 as a reversal point. The light source 12 and the light sensor 13 are optically coupled to the sensor band 7.

In this refinement, the sensor strip 7 is realized from an optical waveguide pair 15 which has a first optical waveguide 16 and a second optical waveguide 17. The light from the light source 12 of the evaluation unit 6 is coupled into the first optical waveguide 16, deflected by the prism 9 in the second optical waveguide 17 and coupled into the light sensor 13 of the evaluation unit 6.

The sensor strip 7 has the sensing region 4, in which light exit regions 8 along the first optical waveguide 16 are arranged in this embodiment. It is also possible to arrange the light exit regions 8 along the second light waveguide 17 of the optical waveguide pair 15.

Light having a wavelength of, for example, 266 nm from the light source 12 is coupled into the first optical waveguide 16. By bending the sensor band 7 in the sen- sierungsbereich 4, the attenuation of the light in the first optical waveguide 16 and thus in the sensor band 7 changes. The thus modulated light is coupled from the second optical waveguide 17 in the light sensor 13. The evaluation unit 6 is made ^¬ out of the change in the attenuation of the light to gain a signal that is further processed, for example, in a signal processor. In a second exemplary embodiment (FIG. 2B), the sensor strip 7 is realized by an optical waveguide 11. The optical waveguide 11 has the light exit regions 8 in the sensing region 4. In this embodiment, the evaluation unit 6 is set up to light the same

Point to couple into the optical waveguide 11 and decouple. The light source 12 is integrated in this embodiment in the light sensor 13.

Light of the light source 12 is coupled into the optical waveguide 11 and deflected by the prism 9 in the same optical waveguide 11. In this embodiment, the optical waveguide 11 has a diameter of 1 mm. It is possible to realize a plurality of optical waveguides 11 as a sensor band 7, so that the light is deflected by the prism 9 into the respective sel ^¬ ben optical waveguide 11.

As the optical waveguide of the sensor strip 7, for example, polymer optical fibers, ie optical waveguides made of synthetic material, are used.

FIG. 3 shows a detailed illustration of the deflection of the light in the sensor band 7 through the prism 9. The construction and function of the prism 9 are shown below with reference to the design of the sensor band 7 in FIG. 2A, but applies to all configurations of the sensor band 7.

The prism 9 is a roof prism in this embodiment. The surfaces of the prism 9 are mutually perpendicular to each other. Such a prism 9 may be viewed in three dimensions flektionseigenschaften as an extension of the RE of a plane as an incident light beam is deflected at an angle of 180 ° 14 regardless of the incident angle to the prism ^¬. 9

The first optical waveguide 16 as well as the second optical waveguide 17 of the optical waveguide pair 15 are glued to the prism 9 with an optical adhesive. The prism 9 points To holes on, in which the first optical waveguide 16 and the second optical waveguide 17 are used. The position of the first optical waveguide 16 and the second lightwave ^¬ conductor 17 to each other, and the offset of the first Lichtwel- lenleiters 16 and the second optical waveguide 17 zueinan ^¬ are taken into account when sticking to the prism 9. The coupling losses, which arise by coupling and decoupling of the light at the prism 9, depend on the material of the prism and on the offset of the first optical waveguide 16 and the second optical waveguide 17 from each other. Ideally, the tolerance when coupling the light into the prism is zero.

Light beams 14 from the first optical waveguide 16 are coupled in the prism 9. After two total reflection then coupling the reflected light into the second optical waveguide 17. The second optical waveguide transmits the light back into the evaluation unit 6, in which the light is coupled into the light sensor 13.

The prism 9 is molded from polymethylmethacrylate. This plastic is easy to cut and has very good opti ^¬ cal properties. Polymethyl methacrylate is also known under the trade name Plexiglas or acrylic glass.

The weight of the prism 9 compared to the sensor band 7 plays a significant role in the occurrence of vibration. Characterized that the prism 9 is made of a lightweight material, NaEM ^¬ Lich polymethyl methacrylate, the weight of the prism 9 is very small. A small weight considerably reduces the influence of vibrations. The prism 9 bie ^¬ tet also good constructive design possibilities, as the reversal point of Sen ^¬ sorbandes can be kept small by its relatively small size.

The sensor strip 7 is realized in a third embodiment of a plurality of parallel optical waveguide pairs 15 (Figure 4). To a centrally arranged pair of optical waveguides 15 wei ^¬ tere pairs of optical waveguides 15 symmetrically to the center of ^¬ ordered optical fiber pair 15 are increasingly spaced apart from each other. The optical fiber pairs 15 each have ^¬ weils a first optical waveguide 16 and a second optical waveguide 17th The optical waveguide pairs 15 are arranged on a carrier jacket 10.

Light of the light source 12 of the evaluation unit 6 is transmitted from the first optical waveguide 16 to the prism 9. In the prism 9 there is a total reflection twice and the light is coupled into the second optical waveguide 17. The light is guided back into the light sensor 13 from the second optical waveguide 17. The light source is, for example, a light emitting diode which outputs a light having a wavelength of 266 nm. One or more light sources 12 may be used. The light sensor 13 is, for example, a ^photodiode .

In this embodiment, the first optical waveguides 16 of the respective pairs of optical waveguides 15 Lichtaustrittsbe ^¬ rich 8. If the sensor band is bent in the sensing region 4, an attenuation of the light occurs in the optical waveguide pair 15. The so modulated light is coupled from the depending ^¬ weiligen second optical fiber 17 in the evaluation unit 6 in the light sensor 13 and obtained therefrom a signal. From the combination of the signals obtained from several optical fiber pairs 15, the width and depth of the bend is reconstructed. This can be made between a large and small impact object 5 a distinc ^¬ dung.

In order to allow a reliable calculation of the size of the impact object 5, four pairs of optical fibers 15 are arranged as described above. By using a plurality of optical fiber pairs 15, it is possible to achieve a better location ^¬ sauflösung, that is, a distinction whether an impact object 5 bounces right or left on a shock absorber of a vehicle is possible.

Claims

New patent claims 1 to 9

1. sensor band (7), comprising:

at least one optical waveguide (11) which is designed as an optical waveguide pair (15) and in that the at least one optical waveguide pair (15) has a first optical waveguide (16) which is arranged parallel to a second optical waveguide (17),

a reversal point, which is a prism (9), which is arranged such that it optically couples the first optical waveguide (16) to the second optical waveguide (17), specifically at the respective first free ends of the respective first optical waveguides (16 ) and second optical waveguides (17) and - light exit regions (8) through which at a Verbie ^¬ tion of the sensor strip (7) attenuation of the light by bending at least the first optical waveguide (16) of the optical fiber pair (15) in the Lichtaus ^¬ tittsbereichen (8).

2. sensor strip (7) according to claim 1, characterized in that the sensor strip (7) at a second free end of mindes ^¬ least one optical waveguide (11) has an evaluation unit (6) optically with at least one of the at least ei ^¬ NEN Optical waveguide (11) can be coupled.

3. sensor strip (7) according to claim 2, characterized in that the evaluation unit (6) has a light source (12) and a light sensor (13) and is adapted to the light from the light source (12) in the first Lichtwellenlei ^¬ ter (16) and to couple light from the second optical waveguide (17) into the light sensor (13).

4. Sensor strip (7) according to claim 1, characterized in that the pri sma (9) a roof Pri sma or a Porro Pri sma i st.

5. sensor strip (7) according to claim 1 and 4, characterized in that the prism (9) comprises polymethyl methacrylate.

6. sensor strip (7) according to claim 1, characterized in that the sensor strip (7)

- A centrally arranged pair of optical waveguides (15) on ^¬ has, - further pairs of optical waveguides (15) symmetrically to the centrally arranged pair of optical waveguides (15) are arranged spaced from each other growing.

7. sensor strip (7) according to claim 1, characterized in that the prism (9) is adapted to reflect the light back into the same optical waveguide (11).

8. sensor strip (7) according to claim 1 and 2, characterized in that the evaluation unit (6) comprises a light source (12) which is integrated in a light sensor (13) and the evaluation unit (6) is adapted to the light the same point in the at least one optical waveguide (11) and couple out of the same at least one optical waveguide (11).

9. sensor strip (7) according to any one of the preceding claims, characterized in that the sensor strip (7) is integrated for pedestrian impact protection in automobiles.