WO2008101934A1

WO2008101934A1 - Impact sensor for a motor vehicle

Info

Publication number: WO2008101934A1
Application number: PCT/EP2008/052022
Authority: WO
Inventors: Thomas Beyer
Original assignee: Continental Automotive Gmbh
Priority date: 2007-02-21
Filing date: 2008-02-19
Publication date: 2008-08-28
Also published as: DE102007008507A1

Abstract

In the case of an impact sensor (1) for a motor vehicle, which sensor comprises an optical fibre bundle (2) which can be fitted in the external region of the motor vehicle such that it extends there along a longitudinal direction, wherein the sensor (1) outputs a signal upon an impact of an object against the external region, the impact deflecting the optical fibre bundle (2) by a certain amount transversely with respect to the longitudinal direction, it is provided that the optical fibre bundle (2) is accommodated in a tension- and compression-resistant, flexurally elastic hollow profile (3) running along the longitudinal direction, and is fixed in the longitudinal direction.

Description

description

Impact sensor for a motor vehicle

The invention relates to an impact sensor for a motor vehicle, comprising an optical fiber bundle, which is attachable in the outer region of the motor vehicle, so that it extends along a longitudinal direction, wherein the sensor in an impact of an object on the outer region, the Lichtleitfaserbündel deflects by a certain amount transverse to the longitudinal direction, emits a signal.

In order to protect passengers of a motor vehicle in an accident, today many restraint means, such as airbags or belt tensioners are used. A sensor detects an accident and triggers the restraints. In practice, acceleration sensors are used for this purpose which measure an acceleration of the motor vehicle and activate the retaining means when a threshold value is exceeded.

For several years, accidents involving pedestrians have been studied more closely, as they often cause serious or fatal injuries in motor vehicle accidents.

Research has shown that severe injury to pedestrians often results from impact with a hood or windshield. Although the bonnet can sometimes give way to the weight of the impact, rigid components are often arranged underneath, which are usually at a small distance from the bonnet. Thus, a desirable in itself, gentle cushioning of the pedestrian on the hood is not possible. Moreover, from an aerodynamic point of view, it is not possible to provide the engine hood with crash structures that could protect the pedestrian in the event of a collision. In order to effectively protect the pedestrian, it has been proposed in recent years, to accommodate an airbag in the windshield or lift the hood in an impact, and thus protect the pedestrian from rigid components and to cushion the impact.

These retention or protection means are also triggered by a sensor. Since the above-mentioned acceleration threshold, as used for the activation of an airbag and belt tensioner, is too large to collisions with a light object, such. For example, to detect a pedestrian, it is necessary to develop special sensors that meet such requirements.

For this purpose, it has been proposed to combine a plurality of optical fibers to form an optical fiber bundle and to mount them in the outer area of a motor vehicle so that they detect a possible impact there. A light source feeds light with a defined intensity into one end of the optical fiber bundle, which has a known transmission behavior. Upon impact of an object on the optical fiber bundle, the transmission behavior deteriorates, for example due to damage or kinking and consequent light extraction from the fiber, and the intensity of the light measured at the other end of the optical fiber bundle by a photodiode decreases. Such a sensor, as he also corresponds to the above-mentioned genus, z. B. from the publication of Siemens Restraint Systems GmbH "A fiber-optic sensor system for the activation of active systems for pedestrian protection" known in the Internet under www.siemens-restraint-systems.de/de/xt- download / VDI_Berlin_2003_FG-Schutz_FOS. pdf is available.

Furthermore, DE 100 23 588 A1 discloses an intrusion sensor for detecting an accident severity in vehicles. This sensor comprises two spaced-apart optical fibers, which are each covered by a plastic sheath, which is on its ner facing the respective light guide side has a serrated profile. A light source feeds light of a defined intensity into the optical fibers, and at the other end of the light guide a photodiode measures the transmitted intensity. If the plastic jacket is squeezed, for example upon impact of an object, its profile penetrates into the light guide and damages it. As a result of the damage, light emerges from the light guide and the transmitted intensity decreases. The severity of the accident is calculated from the defined intensity of the light guide. In a small impact, only one optical fiber is damaged, in a stronger impact both. In order to be able to make a statement about the severity of the impact even if both optical fibers are damaged, an impact velocity is additionally determined. Here, the distance of the light guide serves as a known size and from a detected time difference in which the optical fibers have changed their transmission behavior, the speed is calculated. If its amount is greater than a predetermined threshold, the restraints are triggered.

However, a disadvantage of this sensor is that even with smaller collisions, which in and of themselves do not necessitate triggering of the retaining means, at least one of the optical fibers is irreparably damaged. A costly replacement of the entire sensor is then required.

Proceeding from this, the object of the invention is to provide a sensor which is attachable in the outer region of a motor vehicle and provides a signal which can be used to assess the impact, wherein the sensor is not necessarily damaged in a collision and is easily replaceable.

According to the invention this object is achieved with a sensor of the type mentioned, in which the optical fiber bundle in a tension and compression stiff, bending elastic, along the Housed longitudinally extending hollow profile and fixed in the longitudinal direction.

The accommodation of the optical fiber bundle in the hollow profile proves to be particularly favorable, since the optical fiber bundle is fixed in a defined position, and thus its exact position is known for each segment of the optical fiber bundle. Furthermore, the placement in a flexurally elastic hollow profile avoids a strong punctual load on the optical fiber bundle, as a result of which a more precise statement about a collision can be made and the retention means are activated as required. In addition, the optical fiber bundle is now largely protected from unwanted damage, so it is regularly intact after an impact and does not need to be replaced. In addition, a larger area is covered by the hollow profile, in which an impact is registered. Furthermore, the optical fiber bundle can already be introduced into the hollow profile and fixed therein prior to attachment to the motor vehicle. Thus, possible assembly errors are reduced and there is a simultaneous transport and installation protection. The tensile and compressive rigidity of the hollow profile allows the optical fiber bundle to be braced relative to the hollow profile, which prevents slipping and slipping out.

In a preferred embodiment, the optical fiber bundle is positively and / or non-positively fixed in the hollow profile. Thus, a secure and reliable fixation of the sensor in its defined position.

In a likewise preferred embodiment of the invention, the optical fiber bundle is fixed at one end of the hollow profile with the aid of a deflection device form and / or kraftschlüs- sig. It is thus possible to cover a larger measuring range with an optical fiber bundle. Next to be used clamping or clamping means saved, and necessary Mounting steps reduced because only one side of the hollow profile, an element for clamping and / or clamping is necessary.

In an advantageous development of the invention, the deflection device has a fir-tree-shaped partial region, which is inserted into the hollow profile and fixes the optical fiber bundle between the hollow profile and the deflection device by clamping.

It is furthermore particularly favorable if the deflecting device has a fir-tree-shaped partial region which is inserted into the hollow profile and fixes the optical fiber bundle between the hollow profile and the deflecting device in a clamping manner. Thus, the deflection can be fixed itself, without additional components are necessary or the hollow profile must have a holder. Further, by the clamping of the deflection roller and the sensor, in the region of the deflection roller, a secure fixing of the position of the sensor is made. He therefore can not slip from the deflection or there are no other components necessary to prevent this.

In addition, the optical fiber bundle can be glued or laminated onto the deflection device.

In a further advantageous embodiment, a protective clip is inserted with a fir-tree-shaped portion in the hollow profile and thereby positively and / or non-positively fixed thereto, wherein the protective clip supports the deflection and the optical fiber bundle placed around the deflection device there positive and / or non-positive fixed. Advantageously, the protective clip has a fir tree geometry, it can thus support the deflection and at the same time protect the optical fiber bundle from damage. Furthermore, a positive and / or non-positive fixation, caused by the protective clip and the deflection Device, a quick and easy installation of both the optical fiber bundle on the deflection and in the hollow profile.

In a preferred embodiment of the invention, a clamping element is inserted at one end into the hollow profile, which clamps the optical fiber bundle there. This results in a safe, quick and easy mounting option, if no deflection is desired or required.

It is also particularly advantageous if the clamping element has a fir-tree-shaped portion for insertion into the end of the hollow profile. Thus, a positive and / or non-positive connection can be ensured, which is easy and quick to install.

In a likewise preferred embodiment of the invention, a two-part clamp surrounds the fiber optic bundle near one end of the hollow profile and fixes the fiber optic bundle between the two connected terminal parts frictionally, wherein the terminal can not slip into the hollow profile. Since necessary forces for clamping need not be applied through the hollow profile, this is not loaded transversely to the sensor, but only has to apply possible forces for tensioning the sensor in the longitudinal direction. Thus, the hollow profile is less heavily loaded in the end and thus it can be made simpler in structure. Furthermore, by refraining from introducing parts into the hollow profile, it is largely independent of its internal geometry. It can thus be used identical parts for different hollow profiles, which development costs and costs are reduced.

It is particularly favorable if the optical fiber bundle has along the longitudinal direction at least one subregion with a changed cross section of the bundle, over which a structural interlocking with the hollow profile for fixing the optical fiber Bündeis is realized in the hollow profile. Advantageously, thus eliminating the assembly of additional components. It is thus faster, easier and assembly errors are avoided. In an advantageous development, the hollow profile has along the longitudinal direction at least one partial area with a changed cross-section, over which an impact damper of the motor vehicle realizes a structural locking mechanism for fixing the hollow profile to the impact damper. A fixation of the hollow profile on the impact damper is thus possible quickly and in a defined position and assembly errors are largely excluded.

The configuration and arrangement of the optical fiber bundle in the hollow profile according to the invention achieves a production-tolerant longitudinal alignment of the optical fiber bundle on the vehicle, so that an exact statement about the transverse position of an impact location at z. B. the vehicle front is reached.

The invention will be explained in more detail by way of example with reference to the drawing in principle. Show it:

Fig. 1 an impact sensor;

FIG. 2 shows an optical fiber bundle of the impact sensor of FIG. 1 in an impact; FIG.

3 shows a deflection device for the optical fiber bundle;

FIG. 4 shows a deflection device similar to that of FIG. 3, but with a fir-tree-shaped partial region for attachment; FIG.

Fig. 5 shows a protective clip for e.g. the deflection device of Fig. 3 with a fir-tree-shaped portion for

mounting; 6 shows a clamping element with a fir-tree-shaped partial area for longitudinal fixing of the optical fiber bundle;

7 shows a two-part clamp for longitudinal fixing of the optical fiber bundle;

8 shows an optical fiber bundle with a fixing form for locking the optical fiber bundle in the hollow profile, and

9 shows an impact damper and a hollow profile for adjusting the impact sensor along its longitudinal direction extending over a vehicle front.

FIG. 1 shows an impact sensor 1 for a motor vehicle (not shown), which has a tension-resistant and pressure-resistant, flexurally elastic hollow profile 3, as well as a received therein, here of a plurality of optical fibers L (not shown) z. B. band-shaped optical fiber bundle 2 comprises. The impact sensor 1 is mounted in the outer area of the motor vehicle (eg along the front of the vehicle) and detects an impact C of an object on the outside area.

For this purpose, light of a light source 4 having a defined intensity is fed into the optical fiber bundle 2 at one end thereof. At the other end of the optical fiber bundle 2, a light receiver 5, for example a photodiode receiver, is arranged, which receives the transmitted light and an intensity-dependent signal to an evaluation unit

(not shown) transmitted. When analyzing the intensity, all optical fibers can be tested at once, in groups, or individually, for a loss of intensity, as required.

As usual, each optical fiber L is sheathed with a reflective sheath 6 that transmits the light into the optical fiber L reflected back. However, for each fiber in a longitudinal section, which is to be monitored for an impact, this sheath 6 is removed or replaced by an absorbent sheath, as shown schematically in FIG. 2 on an optical fiber L. If, as also shown in FIG. 2, the optical fiber bundle 2 is bent, for example as a result of an impact C of an object, a part of the fed-in light I decouples from the optical fiber (s) whose cladding 6 is removed or modified in the affected section and the intensity of the transmitted light thus decreases in the affected fiber (s). The modified-length longitudinal section is located at a different location for each optical fiber of the bundle so that over the entire length of the bundle 2 an impact C with a spatial resolution defined by the length of the individual longitudinal sections can be detected. This basic mode of operation of the sensor comprising the optical fiber bundle 2 is described in the already cited publication by Siemens Restraint GmbH "A Fiber-Optical Sensor System for the Control of Active Systems for Pedestrian Protection", to which reference is made in full.

The optical fiber bundle 2 is fixed in the hollow profile 3 in the longitudinal direction, so that the hollow profile 3 and the optical fiber bundle 2 represent a preassembled unit. Various variants are described below, how the optical fiber bundle 2 is fixed in or on the hollow profile 3. These variants can be used individually or in combination.

3, a deflection device 7 is shown, which has a contact surface 8 and a recess 9. The optical fiber bundle 2 rests on the contact surface 8 in a form-fitting manner and is guided and deflected around the recess 9 by the latter. In this case, the optical fiber bundle 2 may be glued or laminated onto the contact surface 8. With the recess 9, the deflection device 7 on the hollow profile fil 3 attached. For this purpose, at one end of the hollow profile 3, a projection 9 corresponding to the recess 9 or pin is provided, which engages in the recess 9 and the deflection device 7, wherein the deflection device 7 is regularly mounted so that the end of the hollow profile 3, which the Lichtleitfaserbündel 2 turns, points away from this.

FIG. 4 shows a protective clip 10 which surrounds the contact surface 8 of the deflecting device 7 with an outer profile 11, this outer region 11 representing a surface corresponding to the contact surface 8 and having a fir-tree-shaped partial region 12 which, referring to FIG the pulley, is located at a pointed end converging. This fir tree-shaped portion 12 is inserted into the hollow section 3. Next, the protective clip 10 has a corresponding with the recess 9 pin 13, the end of which has an undercut 14 which is slightly conical in the end region for better insertion into the recess 9. In addition, the pin 13 in its longitudinal direction on a running over its entire diameter slot which divides the end portion of the pin 13, in two tongues 15 which are bendable to each other. If the protective clip 10 is slipped over the deflecting device 7 and the optical fiber bundle 2, the protective clip 10 lies with the outer region 11 on the optical fiber bundle 2 and the tongues 15 engage with the conical part of the undercut into the recess 9. By further displacement of the protective clip 10, the two tongues 15 are further compressed and slide into the recess 9. At the end of the pin 13 passes through the recess 9, wherein the undercuts 14 protrude transversely across the recess 9 and thus prevent slipping of the deflecting device 7 of the pin 13. If the protective clip 10 is inserted with its fir-tree-shaped partial region 12 into the hollow profile 3, the protective clip 10 is held in a positive and / or non-positive manner by this. At the same time, the fir-tree-shaped part rich 12 the optical fiber bundle 2 in the hollow section 3 and fixed it frictionally.

But also a positive and / or non-positive fixation of the optical fiber bundle 2 by the protective clip 10 and the guide roller 7 is possible. For this purpose, it is necessary that the protective clip with its outer region 11 of the contact surface 8 is modeled so that the outer region 11 after the slipping of the protective clip 10, the optical fiber bundle 2 clamped and thereby fixed non-positively.

FIG. 5 shows a possible embodiment of the deflecting device 7, in which the latter has a fir-tree-shaped partial region 16 at its end converging at a point, which is introduced into the hollow profile 3. Thus, the deflecting device 7 is fixed to the hollow profile 3 and at the same time clamps the optical fiber bundle 2 between the fir-tree-shaped partial region 16 and the hollow profile 3. In addition, bonding between the optical fiber bundle 2 and the contact surface 8 can be formed.

6, a clamping element 17 is shown. The clamping element 17 is wedge-shaped in its basic form, wherein it has a fir-tree-shaped partial area 18 at the pointed end, with which it can be attached to the hollow profile 3 in a positive and / or non-positive manner. Next, the clamping element 17 on a collar K, with which it can be supported against this in engagement in the hollow profile 3. The clamping element 17 is inserted next to the optical fiber bundle 2 into the hollow profile 3 and clamps the optical fiber bundle 2 between itself and the hollow profile 3. Moreover, it is also possible to fix the optical fiber bundle 2 with two clamping elements 17.

Another way of clamping is shown in Fig. 7, wherein here a two-piece clamp 19 is used. The optical fiber bundle 2 is transferred from the terminal 19 gripped, wherein the two terminal parts fix the bundle between them frictionally. For the connection and for generating a clamping force of the two clamping parts, screw connections, adhesive connections, ultrasonic welding connections etc. are possible. But even a combination with a one-sided articulated and / or pluggable connection can cause a clamping action. The clamp can not slip into the hollow profile and thus sets the fiber optic bundle in a pulling direction. With respect to the other direction of pull is at the other end of the hollow profile z. B. provided a similar terminal.

FIG. 8 shows the optical fiber bundle 2 with a special embodiment of its jacket 20, which has at least one wing 21, which changes the optical fiber bundle 2 in its cross section. If the optical fiber bundle 2 introduced into the hollow section 3, the wing can be automatically or manually engaged with a corresponding recess of the hollow section 3, whereby both realize a mold lock and the optical fiber bundle 2 is fixed to the hollow section 3.

Fig. 9 shows an impact damper 22 of a motor vehicle, on which the hollow profile 3 can be attached. For this purpose, and to be able to make a quick and yet accurate positioning, the impact damper 22 has a groove 23 into which a corresponding projection 24 of the hollow profile 3 engages and is thus fixed. So that the hollow profile 3 in the installed state can not migrate along the groove 23 together with the sensor, the groove 23 is interrupted. Of course, it is also possible that the impact damper 22 has a projection 24 which engages in the hollow profile 3.

The illustrated design options combine the above components or devices with each other so that in Sum the locations of the optical fibers on which the jacket is modified or removed, for. B. relative to the vehicle front have a predetermined position with known tolerance,

Claims

claims

1. Impact sensor (1) for a motor vehicle, which comprises an optical fiber bundle (2), which is attachable in the outer region of the motor vehicle, so that it ent ^¬ extends along a longitudinal direction, wherein the sensor (1) in an impact of an object the outer region, which deflects the optical fiber bundle (2) by a certain amount transversely to the longitudinal direction, emits a signal, characterized in that the

Lichtleitfaserbündel (2) housed in a tension and compression stiff, bending elastic, along the longitudinal direction extending hollow profile (3) and fixed in the longitudinal direction.

2. Device according to claim 1, characterized in that the optical fiber bundle (2) is fixed positively and / or non-positively in the hollow profile (3).

3. Device according to one of claims 1 or 2, characterized in that the light ^¬ leitfaserbündel (2) at one end of the hollow profile (3) by means of a deflection device (7) positively and / or non-positively fixed.

4. Apparatus according to claim 3, characterized in that the deflection device (7) has a fir-tree-shaped portion (16) has, which is inserted into the hollow profile (3) and the Lichtleitfaserbündel (2) between the hollow profile (3) and deflecting device (7) clamped in place.

5. Apparatus according to claim 3, dadurchgekenn - characterized in that a protective clip (10) with a tan ^¬ nenbaumförmigen portion (12) inserted into the hollow profile (3) and thereby positively and / or non-positively is fixed thereto, wherein the protective clip (10) the deflecting device ^¬ (7) holds and fixed around the deflection device (7) Lichtleitfaserbündel (2) there fixed positively and / or non-positively.

6. Device according to claim 2, characterized in that at one end in the hollow profile (3) a clamping element (17) is inserted, which is the

Fiber optic bundle (2) clamped there.

7. Device according to claim 6, characterized in that the clamping element (17) has a tannenbaumförmigen portion (18) for insertion into the end of the hollow profile (3).

8. The device according to claim 2, wherein a two-part clamp (19) surrounds the optical fiber bundle (2) near one end of the hollow profile

(3) engages around and the optical fiber bundle (2) is fixed non-positively between the two connected terminal parts, wherein the clamp (19) can not slip into the hollow profile (3).

9. The device according to claim 1, dadurchgekenn - characterized in that the optical fiber bundle (2) ent ^¬ long the longitudinal direction has at least a partial area with a changed cross-section of the bundle over which with the hollow profile a form-locking mechanism for fixing the optical fiber bundle in the hollow profile (3) is realized ,

10. The device according to claim 1, characterized in that the hollow profile (3) along the longitudinal direction has at least one partial area with a changed cross-section, via which with an impact damper (22) of the motor vehicle a Formgesperre for fixing the hollow profile (3) on the impact damper (22). is realized.

1. A device according to at least one of the preceding claims, d a d u r c h e c e n e c e s in that the deflecting device (7) with the optical fiber bundle (2) is glued.