State of the art A vehicle, particularly a motor vehicle, intended to operate on roads in general or on land has to be provided with a speed monitoring instrument (speedometer) situated within the driver's field of vision. Such a speedometer usually shows the vehicle speed in km/h by the position of a pointer relative to a speed scale graduated in km/h on the instrument panel.

Also known is a speedometer which primarily shows the vehicle's speed of motion by means of a movable needle pointer but may also be designed to provide the vehicle's driver with other supplementary visual information.

An example of such an indicating instrument is described in the US patent no.

6320500. The instrument described there involves the use of a pointer supported centrally on the instrument panel to show the vehicle's road speed, while an array of indicators (individually controllable light sources) is used for indicating supplementary information. This supplementary information takes the form of the same vehicle's relative speed with respect to another vehicle in front, i. e. a vehicle which is ahead of, and travelling in the same direction as, the vehicle which is fitted with the instrument. The light sources which constitute the indicators consist of light emitting diodes (LEDs) which, when fired simultaneously, form an arcuate

row of points of light which is composed of LED points and whose longitudinal extent along the speed scale shows by how many km/h the speed of the vehicle fitted with the instrument differs from that of the vehicle in front, i. e. the value of the relative speed between the two vehicles.

A disadvantage of this known indicating instrument is that it can only provide one item of supplementary information (the relative speed) in addition to the road speed of the vehicle fitted with the instrument.

A so-called Adaptive Cruise Control System (ACC or AICC) makes it possible to register a vehicle in front, its speed and the distance between it and a vehicle fitted with the system. The system then adapts the latter vehicle's speed so that it will coincide with the speed of the vehicle in front. The distance between the two vehicles is adapted according to a predetermined time interval which, combined with the speed of the vehicle in front, makes it possible to determine the desirable mutual distance between the vehicles. Presentation of this kind of information to the driver of the vehicle fitted with the system is important from a safety point of view (active safety, ergonomics).

Objects of the invention The primary object of the invention is to provide an indicating instrument which not only shows by means of a needle-type pointer the speed of motion of a vehicle which is fitted with the instrument but also provides the driver quickly and clearly with such supplementary information concerning a vehicle in front, thereby increasing his attentiveness and consequently contributing to safer and more comfortable driving, e. g. by obviating the need for sudden speed changes (particularly deceleration).

A relating second object of the invention is to provide such an indicating instrument whereby supplementary information is presented to the driver without using any needle pointer.

A further object of the invention is that the indicating instrument could be used for indicating at least two further vehicle-related speed parameters (in addition to the road speed of the vehicle fitted with the instrument), at least one of which should be able to provide supplementary information concerning the vehicle fitted with the instrument.

Description of the invention According to the invention, the objects mentioned above may be achieved with an indicating instrument of the kind indicated in the introduction which exhibits the features indicated in the characterising part of patent claim 1. Dependent claims 2- 8 relating to claim 1 indicate supplementary features which may distinguish embodiments of the indicating instrument.

What primarily distinguishes the invention is that the instrument panel incorporates not only the needle pointer which indicates the road speed of the vehicle fitted with the instrument but also an indicating area which becomes visible to the driver (the observer) when it lights up. The visible extent of this indicating area varies depending on at least two different speed values (speed parameters). One of these two speed values is a speed which in some way pertains to (or is related to) the vehicle fitted with the instrument, while the other is a speed which applies to another vehicle. The illuminable indicating area has at least two different and clearly visible demarcating edges, the contrasting effect of which relative to the instrument panel makes them form indicating delineations with respect to the speed scale on the instrument panel.

The instrument panel is preferably provided with an array of firable light emitting means situated appropriately within a surface area of the instrument panel relatively near to the edges. The illuminated indicating area thus consists of whichever of the array of light emitting means are fired (i. e. emit light) at the particular moment. The expression"light emitting means"in this context means quite generally a light source which, when fired/activated, emits visible light and can therefore be used to provide visual information.

Examples of such light emitting means which are suitable in this context include light emitting diodes (LEDs), floating crystals and other more or less"spot- shaped"light generating means or units. In cases where LEDs are used, they need to have at least two different operating states, the diodes being fired in one operating state and extinguished in the other. In certain contexts it may be appropriate to use LEDs which light up in a first colour in one operating state, and in a second colour in another operating state. Instead of LEDs which light up in different colours in different operating states, it is possible to conceive of using LEDs which light up with clearly different intensities in their different operating states.

The speed pertaining to a vehicle fitted with the instrument may be a speed which is desirable for some particular reason (i. e. a set speed) for the vehicle, and the speed applicable to another vehicle may be the speed of a vehicle which is ahead of the vehicle fitted with the instrument.

In the case of indicating instruments with a circular instrument panel, it is probably often appropriate that the illuminable indicating area should take the form of a relatively narrow strip of indicating area in the form of a circular arc. The short sides of this area (i. e. its ends) then constitute the indicating edges whose positions relative to the speed scale on the instrument panel indicate readable speed values.

One indicating edge may then be used to show a set speed for the vehicle fitted

with the instrument, while the other indicating edge is used to indicate the speed of a vehicle in front. Examples of set speeds for the vehicle fitted with the instrument include the maximum permissible speed within applicable speed limits, the most economic travelling speed (lowest fuel consumption), the appropriate average speed for the vehicle to complete, with a certain margin, a certain journey within a certain time, and so on.

Brief description of drawing The instrument will now be exemplified below by describing an embodiment of an indicating instrument according to the invention, depicted in the attached drawing, which consists entirely of a schematic diagram of an indicating instrument of a circular type.

Description of a preferred embodiment The indicating instrument 2 depicted in the drawing is of a circular type and has an instrument panel 4 with a centrally supported needle pointer 6, the tip of which sweeps across a speed scale 8 at or adjacent to the outer edge of the instrument panel 4. The indicating instrument is a speedometer intended for a dashboard in a motor vehicle and provided with a speed scale 8 graduated in km/h. On the instrument panel 4 there is a strip of indicating area 10 in the form of a curving circular arc capable of maximum illumination, which in the example depicted extends approximately from speed 10 km/h to speed 90 km/h. An activated (i. e. illuminated) portion 12 of this maximum indicating area 10 is depicted as extending approximately from speed 20 km/h to speed 80 km/h

The indicating area 10 depicted is composed of an array of illuminable (firable/extinguishable) light emitting means 13 which in this case take the form of light emitting diodes, which are therefore placed side by side in an arcuate row (or in two or more concentric rows situated close to one another). The thus momentarily illuminated portion 12 of the maximum-illumination indicating area 10 has an arcuate longitudinal extent whose magnitude depends on two different speed values, namely a lower limit value indicated by the"lower"demarcating edge (short side) 14 of the area 12, and an upper limit value indicated by the "upper"demarcating edge (short side) 16 of the area 12. The lower limit value (at 14) is in this case the speed of motion of another vehicle which is ahead of, and travelling in the same direction as, the vehicle fitted with the instrument.

The upper limit value (at 16) is a set speed (i. e. a desired speed) for the vehicle fitted with the instrument. Depending on whether these two speeds increase or decrease, the demarcating/indicating edges 14 and 16 will shift to lower or higher speed values on the speed scale 8. The shifting of these limit values takes place by the firing or extinguishing of more or fewer of the means 13 which constitute the array of light emitting means.