LIGHTING SYSTEM FOR A MOTOR VEHICLE

The invention relates to a lighting system for a motor vehicle, to provide three lighting functions in which the color temperature is the same, comprising a projector headlamp in which is arranged a high-pressure discharge lamp which is connected to at least one ballast. Present-day lighting systems for motor vehicles employ different technologies, such as halogen lamps and xenon lamps, to perform the requisite lighting functions of daytime running light, low-beam light and high-beam light. Because of this, different colors of light and different color temperatures are obtained when a change is made between the different lighting functions, such as from daytime running light to low-beam light for example. Also, because of the at least two lamp systems that are required, a considerable amount of overall space is required.

One possible way of avoiding different colors of light and different color temperatures is to use the same lamp technology for all the lighting functions. For all-xenon lighting however, it would be very expensive to do this. What is more, the overall size of the headlamp would be very large, due to the second ballast that would be required for a dual- function xenon headlamp and a third ballast that would be required for a triple-function xenon headlamp.

It is to this problem that the invention aims to provide a remedy. It is the object of the invention to provide a lighting system for a motor vehicle which provides three lighting functions and, in doing so, is of small overall size and can be produced at low cost. In accordance with the invention, this object is achieved by providing precisely one high- pressure discharge lamp and the projector headlamp having two masks which can be moved into the beam path of the said projector headlamp. In the case of bi-xenon headlamps, it is known for the beam path to be acted on selectively by means of a movable mask that can be moved into the beam path of the projector headlamp, by which means the "low-beam light" and "high-beam light" functions can be obtained with only one high-pressure discharge lamp. By providing a further mask, which can be separately actuated, a third, "daytime running light" function becomes possible, the beam path of the projector headlamp being screened off

in a way that is suited to the statutory requirements. Rather than a mask, what may also be used to act on the beam path are a filter element and/or a mirror and/or a diffusing lens.

The invention creates a lighting system for a motor vehicle which provides three lighting functions in which the color is the same and the color temperature is the same and which, at the same time, is of small overall size and can be produced at low cost.

In one form of the invention, the masks are mounted by means of respective points of pivot, with the points of pivot being arranged on opposite sides. By these means, it becomes possible for the masks to be separately actuated without interfering with one another. A control unit is preferably provided by means of which the masks can be actuated in such a way that the functions of daytime running light, low-beam light and high- beam light can be obtained. This enables the lighting system to be operated in a convenient way.

In one form of the invention, the ballast is designed to be dimmable. In this way, it becomes possible for a selective change to be made in the supply current to the lamp by the use of only one ballast, by which means it is possible for regulation of the brightness of the high-pressure discharge lamp to be achieved.

Advantageously, a light sensor is provided that is connected to the control unit of the masks. By this means, it becomes possible for the masks to be actuated as a function of the external lighting conditions. In this way, the mask that is provided for the daytime running light function can be pivoted automatically to the requisite position.

In a further form of the invention, means are provided to generate a defined sequence of initial ignitions to produce a bright flashed light. It is possible in this way for the extremely bright initial ignitions of the arc of the high-pressure discharge lamp, which are fired in succession without the lamp going into a stable operating state, to be deliberately strung together into a sequence. Studies have shown that a sudden flash of light which is triggered in front of a vehicle causes an object to stand out in such a way that the driver can perceive it at a considerably earlier point in time. By generating a sequence of initial ignitions, a flashed light can be produced which makes distant objects perceptible to the driver at an earlier point in time. Studies have shown that a frequency of one to twelve initial ignitions per second, and in particular of seven initial ignitions per second, is able to make distant objects visible at a particularly early point in time. The means of generating a defined sequence of initial ignitions is preferably a triggered switch.

The frequency of the defined sequence of initial ignitions is advantageously able to be set. This makes it possible for the frequency to be varied, as a function of the distance away at which an object is situated for example. By means of a timer module that is provided as an option, the generation of the flashed light can, in addition, be limited to times when critical situations occur when objects suddenly appear in the path of a motor vehicle.

In an advantageous form of the invention, at least one sensor for the early detection of objects is provided which is connected to the means of generating a defined sequence of initial ignitions. This makes it possible for the flashed light to be activated in a selective way. What are suitable for this purpose are, in particular, infrared cameras, radar devices or even ultrasonic sensors. Early detection of distant objects can be achieved with these known means without causing any visual nuisance to other road users. A distant object having been detected, a flashed light can then be initiated to make the object perceptible to the driver at an early point in time. A camera system that will continue to be suitable and that is familiar in the field of automobiles is also what is called the lidar system which, unlike radar systems, is based on light waves.

Other variants and forms of the invention are specified in the remainder of the dependent claims. An embodiment is shown in the drawing and is described in detail below. The single Figure 1 is a schematic view of a projector module of a projector headlamp. The lighting system for a motor vehicle that has been selected as an embodiment comprises a xenon lamp 1 which is arranged inside a reflector 2. The xenon lamp 1 is provided with an integrated ignition circuit 11. Arranged opposite the reflector 2 is a lens 3.

Arranged between the reflector 2 and the lens 3 are two masks 4, 5 that are able to be pivoted into the beam path of the projector headlamp by means of points of pivot 41, 51. In line with the functions they perform, the masks 4, 5 are of different forms and thus project into the beam path of the projector headlamp in different ways.

The mask 4 corresponds to the mask that is known in the prior art for bi-xenon headlamp systems, which enables a switch to be made between the "low-beam light" and "high-beam light" lighting functions. To perform the "low-beam light" function, the mask 4 is pivoted into the beam path of the projector headlamp; if the mask 4 is situated out of the beam path, then the "high-beam light" function is in operation.

The mask 5 is used to switch between daytime running light and low- beam/high-beam light. If the mask 5 is situated out of the beam path of the projector

headlamp, then either the "low-beam light" or "high-beam light" function is operative, depending on the position of the mask 4. To enable the "daytime running light" function to be performed, the mask 5 is pivoted into the beam path of the projector headlamp. When the mask 5 is in this position, the mask 4 should be pivoted out of the beam path. In an expanded embodiment, a sensor for ambient brightness is provided that is connected to a control system that is set up to control the masks 4, 5. In daylight, the sensor for ambient brightness transmits an appropriate brightness signal to the mask control system, which latter positions the mask 5 in the position for the "daytime running light" function. In this configuration, the lamp 1 performs a daytime running light function which produces the desired attentiveness by having a dazzle effect on the oncoming traffic. At the same time, a dimmable ballast is provided, the supply current from which is regulated down to a lower level in daylight, thus enabling the lamp 1 to be operated at 20 watts in the embodiment.

If the sensor for ambient brightness reports that the surroundings are dark, the mask 5 is pivoted out of the beam path of the projector headlamp. At the same time, the ballast is set to a higher power, which in the embodiment enables the lamp 1 to be operated at 35 watts.

In a further embodiment, the lighting system may be fitted with a means of generating a bright flashed light to enable distant objects to be perceived at an early point in time. For this purpose, the xenon lamp 1 is connected to the ballast via a triggerable switch. The ballast of the lamp 1 is also connected to a radar sensor and, as an option, to a speed sensor. In the event of an object being detected by the radar sensor, the lamp 1 is changed to a flashed mode by means of a sequence of intermediate ignitions.

For this purpose, the ignition circuit 11 is excited at regular intervals by the triggerable switch to cause initial ignition of the lamp 1. Between the initial ignitions, the lamp 1 is not brought into a stable state of operation. Alternatively, the flashed light may also be initiated by means of a sequence of intermediate ignitions. These intermediate ignitions may for example be produced by means of a capacitor that is selectively discharged across the arc of the gas discharge lamp. To supplement this, a timer module may be provided by means of which the duration of the flashed light that is initiated can be set, to three seconds for example.