Device for detecting the crossing of a road marking for motor vehicle

p0001The present invention relates to a device for detecting the crossing of a marking line on the floor separating traffic lanes for the motor vehicle.

p0002Sometimes a motorist traveling for example towards the right traffic to a highway, inadvertently encroach on the road to the left traffic crossing the marker line that separates these two pathways. This may create a situation of danger, especially when another vehicle is about to perform an overtaking maneuver. Similarly, the motorist may also encroach on the emergency stop and cross the road marking line that separates the path of right traffic highway of said channel emergency stop. This can also create a situation of danger, especially when another vehicle is stopped on the emergency stop lane.

p0003To alert motorists of the situation of impending danger, it has been proposed to replace conventional marking lines that are smooth with rough marker lines. When the wheels of a motor vehicle encroach on such rough marker lines, they produce an audible sound characteristic inside the vehicle cabin and informs the driver that he is in the process of committing a trajectory deviation. The noise stops as soon as the driver has corrected its course and returned to his lane.

p0004The appearance of rough marker lines constituted real progress in road safety. Unfortunately, given the extent of the road network, the roads can be equipped with such marking lines. In addition, the noise produced by the wheels of the motor vehicle when encroach on a rough marker line can be covered by engine noise or the sound of the car radio, so that the driver can not be informed the dangerous situation in which it is located.

p0005To overcome the drawbacks of passive safety systems such as rough marker lines, automakers offered onboard active safety systems in vehicles. Tests have been made in this direction with a camera installed in the vehicle and filming continuously the road which runs under the wheels of the vehicle. Such a system, however, requires a complex computer system to analyze the images produced by the camera and detecting the crossing of a boundary line, which makes it particularly expensive and difficult to implement.

p0006Another known active security system includes a plurality of infrared transmitters associated with photodetectors and arranged in the front bumper of the vehicle. Each sensor of this system consists of a master unit comprising a transmitter and a receiver, and a slave housing also consists of a transmitter and a receiver, which allows the electronic sharing in order to dephase emissions and avoid mutual glare sensors. In a preferred embodiment of this system, seven double sensors, that is to say, seven pairs of master and slave boxes, are arranged at regular distance intervals from each other under the vehicle so as to cover the entire width said vehicle.

p0007The objective of the system described above does not anticipate the detection of a lateral drift of the vehicle, but to generate an alarm from the time one of the wheels of said vehicle crosses a road marking delineation traffic lanes. For this purpose, the transmitters each emit infrared light beam toward the floor. These infrared light beams are then reflected on the floor and are directed to the photodetectors which, depending on the amount of reflected light, are capable of determining if the light is reflected on the road surface (e.g., concrete ) or on a horizontal white strip marking. According to information collected by this system and the state of the vehicle (speed, prior indication of an overtaking maneuver by commissioning flashing lights or not), the system activates one or other of two vibrators arranged in the driver's seat to signal to him that he is in the process of crossing a horizontal boundary marking of traffic lanes with his right hand, his left respectively.

p0008The path monitoring system described above has the advantage of quickly inform the driver significant differences path of his vehicle to his file on the roadway, discrepancies, the causes can be varied: drowsiness, drowsiness, distraction. Such a system is less expensive than a system using a trajectory tracking camera but remains relatively complex to implement. Indeed, this system has no less than fourteen master and slave boxes, making the wiring of such a particularly complex system and significantly increases the time of installation and the number of parts necessary for mounting under the bumper of the vehicle. This multiplication of the number of elementary sensors also the problem of the long term reliability of such a system. In addition, a dual sensor comprised of a master unit and a slave unit constitutes an inseparable insofar as the master unit operating characteristics are calibrated with respect to those of the slave box. Thus, in case of failure of such a dual sensor following a breakdown or damage to the front bumper, it must simultaneously replace both master and slave boxes. Therefore, the masters and slaves boxes must be stored in pairs, which raises inevitable inventory management problems.

p0009The present invention aims to overcome the aforementioned problems as well as others by providing a trajectory of a motor vehicle monitoring system which, in particular, to limit the number of parts to be used.

p0010To this end, the present invention relates to a device for detecting the crossing of a road marking delimiting traffic lanes of a road for a motor vehicle, characterized in that it comprises at least a housing to be disposed under the vehicle and comprising means for projecting two light beams onto the carriageway in two distinct zones do not overlap, and separate means for sensing each of the two light beams after reflection on the carriageway.

p0011Thanks to these features, the present invention allows to group the master and slave functions dual sensors of the prior art in a single housing, which greatly simplifies wiring of such a system and allows substantial savings, including terms of number of pieces of fixing and assembly / disassembly time. In addition, the casings of the invention are interchangeable, which greatly simplifies inventory management of such cases.

p0012According to a first embodiment, the present invention relates to a kind of the detection device described hereinbefore, characterized in that the at least one housing, having a general axis of symmetry, contains a single light source emitting a primary light beam towards the floor, and at least one photodetector for detecting the light after reflection on the carriageway, two first optical devices whose optical axes are inclined at a first value relative to the general axis of symmetry of the housing being disposed on the path the primary light beam at the output of the light source so as to split said primary light beam into two secondary light beams guided onto the carriageway in two distinct zones, and two second optical devices whose optical axes are inclined at a second value with respect to the general axis of symmetry of the housing being disposed on the path of the secondary light beams after they are reflected on to the floor and before they reach the at least one photodetector.

p0013According to a second embodiment, the present invention relates to a device of the type described hereinbefore, characterized in that the at least one housing, having a general axis of symmetry, contains two light sources each emitting a light beam towards the floor, and at least one photodetector for detecting the light after reflection on the carriageway, two first optical devices whose optical axes are inclined at a first value relative to the general axis of symmetry of the box being each disposed on the path of one of the light beams at the output of the corresponding light source, so as to guide said two light beams onto the carriageway in two distinct zones, and two second optical devices whose optical axes are inclined at a second value with respect to the general axis of symmetry of the housing being disposed on the path of the light beams after they are reflected on to the floor and before they reach the at least one photodetector.

p0014Other characteristics and advantages of the present invention appear more clearly from the following detailed description of a trajectory deviation detecting device of a motor vehicle according to the invention, this example being given purely illustrative and pulls not limited only in conjunction with the accompanying drawings in which:<ul><li>Figure 1 is a schematic bottom view of the front bumper of a motor vehicle fitted with the path deviation detecting device according to the present invention;</li><li>Figure 2 is a schematic diagram illustrating the forward and return paths of the light beams from the detection device according to the invention and reflected from the roadway on which the motor vehicle;</li><li>Figure 3 is a perspective view of one of the units constituting the detection system of the invention;</li><li>Figure 4 is a front view of the housing shown in Figure 3;</li><li>Figure 5 is a sectional view along the line VV of the housing shown in Figure 4;</li><li>Figure 6 is a sectional view along the line VI-VI of the box shown in Figure 4;</li><li>7a-7c are schematic front views respectively in section along the lines AA 'and BB' of the path drift detection box according to a first embodiment; </li><li>8a-8c are schematic front views respectively in section along the lines AA 'and BB' of the path drift detection box according to a second embodiment, and</li><li>Figures 9a-9c are schematic front views respectively in section along the lines AA 'and BB' of the path drift detection box according to a third embodiment.</li></ul>

p0015The present invention proceeds from the general inventive idea of ​​grouping in a single housing the master and slave elements dual sensors of the prior art. With this feature, it halves the number of boxes to be installed in a vehicle to detect potential thereof path deviations, which can significantly reduce the number of fasteners and assembly time / disassembly. Furthermore, the housings constituting the device according to the invention are interchangeable, which simplifies inventory management.

p0016Figure 1 is a schematic bottom view of the front bumper of a motor vehicle (not shown) fitted with the path deviation detecting device according to the present invention. Designated as a whole by the general reference numeral 1, this bumper is provided with a plurality of housings 2 arranged at substantially regular distance intervals along said bumper 1 so as to cover the total width of the motor vehicle thus equipped . In the example shown in Figure 1, the housings 2 are the number of September It goes without saying that this example is given for illustrative purposes only and that the number of cases 2 may vary depending on, geometry the bumper 1 and the vehicle dimensions.

p0017Figure 2 is a schematic diagram illustrating the forward and return paths of the light beams from one of the housings 2 constituting the detection device according to the invention, these beams being reflected from the roadway on which the motor vehicle. Indeed, and as will be described in detail later, each housing 2 comprises means for projecting two light beams 4 and 6 on the floor 8 in two distinct zones 10 and 12 do not overlap, and means for sensing the two light beams 14 and 16 after reflection on the floor 8.

p0018As can be seen upon review of Figure 2, the light beams 4 and 6 from the housing 2, and the beams 14 and 16 resulting from the reflection of light on the floor 8 are inclined at a value α, β, respectively, relative to the general axis of symmetry zz 'of the housing 2, so that the focusing regions 10 and 12 do not overlap, and a light beam produced by one of the light sources does not come dazzle the photodetector cooperating with the other light source. Preferably but not limited to, light beams will form with the axis of symmetry zz 'of the housing 2 at the same angle of about 6 °. By a suitable choice of the optical characteristics of the system (focal lengths and diameters of the lenses; distances between the lenses and photodetectors; height of the photodetectors with respect to the floor), it can be ensured that a light beam produced by one of the sources light will not be detected by the photodetector cooperating with the other light source.

p0019The focusing regions 10 and 12 of the beams on the roadway typically form light spots having a diameter of about five centimeters. More light spot on the floor will be smaller, the better the resolution of the system. However, adjustment of optical systems will be tricky. On the contrary, the more light spot is, the more tolerance on the alignment of optical systems will be. But in the latter case the system resolution will be less. We must find a compromise. Moreover, the measurement accuracy will be better as these spots will be distributed to the most regular intervals possible distance. It is noted on the other hand at the level of the focus points 10 and 12, a part of the light emitted diffuse and therefore can not be collected by the housing 2. The latter comprises in turn a 18 extended by a cable connector 20 that connects the electronic processing circuits signals (not shown) which are embedded in the vehicle. Like, for reasons related to the ergonomics of where the housing 2 to be fixed, it is not assured that the axis of symmetry zz 'said housing 2 is perfectly vertical, it can be provided the opportunity to rotate the housing 2 about a horizontal axis yy 'in order to better adjust its position. Similarly, to avoid dirt projections from the floor damaging said box 2, it is also possible to mount it slightly inclined from the vertical.

p0020Figure 3 is a perspective view and dissociated state of a housing 2. The latter consists essentially of a solid body 24 of substantially rectangular shape, an optical block 26 and a cover 28. the optical block 26 includes a base 30 whose outline conforms to the general external shape of the body 24 of the housing 2 and on which stand two optical transmission tubes 32 and 34 and two optical reception tubes 36 and 38 . the optical unit is intended to be inserted in the body 24 which has, for this purpose, recesses 32a, 34a and 36a, 38a respectively for receiving the transmission tubes 32, 34 and the receiving tubes 36 and 38 . the various elements constituting a housing 2 according to the invention may be made of any suitable material such as, notably, of the injected or molded plastic.

p0021Figures 5 and 6 are sectional views respectively according to the lines VV and VI-VI of the housing 2, the front face 40 is shown in Figure 4. As can be seen in these two figures, lenses 32b, 34b and 36b, 38b are provided at the end of the emission tube 32, 34, respectively receiving 36, 38. These lenses can be of mineral or organic type, to be fitted one to each end of the tubes or come from integral with the optical block 26. in the latter case, the optical block 26 is preferably but not exclusively carried out by injecting a plastic material transparent to the wavelength used and additionally may be opaque to the wavelengths not desired. It will be understood that each optical tube may include a more complex lens system comprising two or more lenses.

p0022The lenses 32b, 34b and 36b, 38b may be symmetrical lenses, in which case their optical axes are perpendicular to their respective input and output faces. Must then mount these inclined lenses, so that their optical axes form with the general axis of symmetry zz 'of the housing angles α, β respectively sought. Alternatively, one can also use lenses that do not exhibit axial symmetry and whose optical axes are naturally inclined at the desired value with respect to the general axis of symmetry zz 'of the housing 2.

p0023Two light sources 40 and 42 are disposed at the bottom emission tubes 32 and 34. It is preferably, but not limitatively, of two diodes emitting light in the infrared range. Similarly, two photoreceptors 44 and 46 are disposed at the bottom of the receiving tubes and used to capture the light emitted by the diodes 40 and 42 after reflection thereof on the roadway. In the example shown in the drawing, the diodes 40 and 42 and photoreceptors 44 and 46 are mounted on the surface of a printed circuit 48 by a well known technique in its Anglo-Saxon name "Surface Mounted Device" or "SMD" : of the 50 electronic components are mounted on the rear side of the PCB 48. Alternatively, the LEDs and photoreceptors may be mounted back on the PCB 48, better known under its technical Anglo-Saxon name "flip chip bonding" . In the latter case, it would still be necessary to practice in the circuit board facing holes diodes and photodetectors respectively.

p0024Figures 7a-7c are schematic views respectively front and in section along the lines AA 'and BB' of a path drift detection box according to a first embodiment of the invention. According to this first embodiment, the housing 2 contains (see figure 7b) two light sources 40 and 42 each emitting a light beam 4.6 in the direction of the floor, and two photodetectors 44 and 46 (Figure 7c) for detecting light 14, 16 after reflection on the floor. Two first optical devices 32b and 34b whose optical axes are inclined at a value α with respect to the general axis of symmetry zz 'of the housing 2 are disposed each on the path of one of the light beams 4,6 in its output of the corresponding light source, so as to guide said two light beams 4,6 onto the carriageway in two distinct zones. Two second optical devices 36b and 38b whose optical axes are inclined at a second value β (which may be equal or different from the value α) relative to the general axis of symmetry zz 'of the housing 2 are, for their , disposed on the path of the light beams 14, 16 after they are reflected on to the floor and before it reaches the photodetectors 44, 46.

p00258a-8c are schematic views respectively front and in section along the lines AA 'and BB' of a path drift detection box according to a second embodiment of the invention. In this second embodiment, the housing 2 contains not a single light source 40 (see Figure 8b) that emits a primary light beam is split into two secondary beams of light 4.6 guided onto the carriageway in two areas distinct nonoverlapping. By against the casing 2 always contains two photodetectors 44 and 46 (Figure 8c) and the second optical devices 36 and 38b associated therewith. Thus, also in this case, a spot of light on the road is a single photodetector.

p0026Finally, Figures 9a-9c are schematic front views respectively in section along the lines AA 'and BB' of a path drift detection box according to a third embodiment of the invention. According to this third embodiment, the housing 2 contains (see Figure 9b) two light sources 40 and 42 which each emit a beam of light 4.6 toward the floor, and the first two optical devices 32b and 34b associated with said sources light 40 and 42. against the casing 2 no longer contains a single photodetector 44 (Figure 9c), the second two optical devices 36b and 38b having, in this case, the function of directing the light beams 14, 16 to the single photodetector 44 after said beams 14,16 are reflected on the floor. This solution is economical because it uses only a single photodetector. It will be understood of course that the two light sources 40 and 42 should not be lit simultaneously so that the photodetector can discriminate the light alternately from the one and the other of these two light sources.

p0027It goes without saying that the invention is not limited to the embodiments which have just been described and that various simple modifications and variants can be envisaged without departing from the scope of the invention. In particular, it may be envisaged to have in oblique front of the optical sources or partitions pierced with a hole.