Abstract:
The method for displaying speed variables in a motor vehicle includes automatically selecting and displaying one of a number of different possible speed scales on a speedometer according to the physical units for speed values employed at the current location of the vehicle. An acoustic and/or optical alarm signal is produced when the vehicle passes from one governmental region in which one set of physical units is used to another in which a different set is used. In addition, speed limits at the current location may be displayed on the speed scale itself by highlighting an appropriate scale mark or producing a scale mark of a different length or color. The current location may be obtained from an on-board GPS. The speed limits and physical units for speed values at the current location are retrieved from a data storage media according to that location. The speed limits may be updated by radio connection. Digital display devices for speed values with similar features are disclosed.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a method of automatically adjusting displayed data, especially vehicle speed data, in a vehicle with a combined instrument and, more particularly, to a method of displaying vehicle speed information in a vehicle that takes account of changes in vehicle location and speed variable units between regions in which the vehicle is travels. 
     2. Prior Art 
     It is already well known to display the actual speed of a vehicle and with it the maximum speed for many localities, for example 50 km/hr, on a display device in the vehicle. This display occurs, e.g. by a red mark or a red bar, which is put on the scale of the display device, so that the speed scale value of 50 km/hr is specially marked for a user of the vehicle. Furthermore it is possible to provide special markings on the vehicle speed scale at certain special vehicle speed values, such as a maximum speed of 30 km/hr in residential areas or of 130 km/hr as posted or recommended speed on the autobahn in Germany or on an expressway. If the user of the vehicle now drives the vehicle into a different country, generally different values are used for the speed limits for the various classes of roads and streets in the different country. Furthermore even the physical units of the speed limits, which are posted on signs, may be different. For example, speed limits may be in miles per hour instead of kilometers per hour. Thus it becomes difficult for the user of the vehicle to correlate the actual speed of the vehicle with the allowed speed limits. Primarily the speed limits from the country in which the vehicle originated or from which the vehicle traveled remain emphasized on the display device and can irritate the driver of the vehicle, since they are no longer applicable. Furthermore it is also known in the art to provide a speed scale on the display device in several different physical units, for example miles per hour and kilometers per hour. The user of the vehicle must then determine-the actual speed value indicated on the display device by selecting the correct physical units based on his knowledge of the region in which the vehicle is located. Furthermore he may be irritated by marked speed limits on the display device that are not applicable to the region in which the vehicle is currently located. This is also true when there is no change in the physical units by which speed values are displayed but only a change in the allowed maximum speed limits. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a method of automatically adjusting vehicle speed values displayed in a vehicle according to vehicle location, i.e. according the particular governmental region or country through which the vehicle is currently traveling. 
     According to the invention the method of displaying speed information in a vehicle, especially a motor vehicle, includes the steps of: 
     a) determining a current actual position of the vehicle with a positioning device; 
     b) locating the current actual position of the vehicle determined in step a) on a digital map; 
     c) identifying a region, such as state, country or city area, in which the current actual position is located on the digital map; and 
     d) displaying automatically on a display device at least one of an actual current speed of the vehicle and allowed speed limits in the region for at least one type of road or street in physical units used in the region identified in step c). 
     The method according to the invention with the features of the appended claims has the advantage that the driver is always informed regarding the actual vehicle speed, without requiring him or her to select between speed scale values in two different physical units. Because of this feature of the invention it is easy for the driver to react to traffic signs, which indicate speed limits. The actual speed of the vehicle is then always displayed by the display device with the physical units for speed that are used in the region or area in which the vehicle is is currently located. Furthermore in preferred embodiments of the method the driver is informed of the optimum maximum speed for certain street or road types in the region through which the vehicle is traveling. Irritation of the driver caused by display of a maximum speed or speed limit on the speed scale which is in units that are not used in the region in which the vehicle is located is therefore avoided. Furthermore the claimed method is advantageous for the manufacture of speed display devices used in the vehicle, since different display devices are not required to provide country-specific speed units and country-specific speed limits for different countries. Different speed physical units and speed limits are automatically displayed with the same display device coupled with e.g. a global positioning device. 
     Preferred embodiments of the method with advantageous additional features are described hereinbelow and claimed in the appended claims. 
     It is especially advantageous if an acoustic and/or optical warning signal is produced when the display of the actual vehicle speed and/or the speed limits or maximum allowed speed values changes. The user of the vehicle is thus signaled that he should now consider another speed limit and/or other physical units being used in the region in which the vehicle is now currently located. Furthermore the warning signal avoids a sudden and unexpected change of the speed display that could otherwise confuse the driver. 
     It is further provided in preferred embodiments of the method that the display of the actual vehicle speed and/or the allowed maximum speed values occurs in a display device that comprises a freely programmable combined instrument. This combined instrument advantageously comprises a display screen so that the method according to the invention can be performed without mechanical or structural arrangements, for example not a speedometer with a pointer, with which speed values are indicated. 
     Preferred embodiments of the method according to the invention also advantageously include updating the speed limit data stored in the vehicle by means of a radio connection of by means of a data carrier. Then since allowed maximum speed values can change in certain region or also the position of region boundaries can change, it is also possible to update stored data in order to permit the display of the correct speed limits. 
     In a preferred embodiment of the method according to the invention whether or not a region boundary has been crossed by the vehicle is tested more frequently in a border zone for the region than in the central part of the region. When the vehicle is located within the region in an area outside of the border zone, passing over the region border or boundary is very unlikely in a certain predetermined time interval. A frequent test or inquiry into whether or not the vehicle has crossed over the region boundary is thus not required and takes unnecessary processor capacity when the vehicle is located in the central part of the region. In contrast a region change is much more likely in a border zone of the region in which the vehicle is currently located, so that more frequent testing to determine which region the vehicle is located in is required. According to this preferred embodiment of the invention then the change of the display of the actual vehicle speed and region speed limits is possible more rapidly in response to a change of the region in which the vehicle is located. 
     It is also advantageous when the display of the actual vehicle speed and/or the speed limits occurs according to the type, conditions and characteristics of the vehicle. Thus different maximum permitted speeds can be displayed by the display device according to the vehicle weight, engine size and trailer operation, so that the vehicle is not driven too fast by the driver. 
     Furthermore in a preferred embodiment of the method the driver is informed of the speed limit for the type of road or street on which the vehicle is currently traveling. Thus the driver does not need to make a decision regarding the type or class of the street or road on which the vehicle is traveling currently himself or herself in order to know the speed limit. 
     It is advantageous particularly to provide the acoustic and/or optical warning signal to the driver as soon as he or she exceeds the current maximum permitted speed in the region through which the vehicle is passing. Because of this feature of the method unintended speeding at speeds above the speed limit because the driver does not observe the speed display device is prevented. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     The objects, features and advantages of the invention will now be illustrated in more detail with the aid of the following description of the preferred embodiments, with reference to the accompanying figures in which: 
     FIG. 1 a  is a flow chart of the overall or general steps of the method according to the invention for display of speed information in a vehicle; 
     FIG. 1 b  is a flow chart showing details of a vehicle position determining part of the method shown in FIG. 1 a  according to the invention; 
     FIG. 1 c  is a flow chart showing details of the display device adjustment part of the method shown in Fig. 1 a;    
     FIGS. 2 a ,  2   b ,  2   c  and  2   d  are action views of a display device illustrating the method according to the invention for display of speed information in the vehicle; and 
     FIG. 3 is a block diagram of a device for performing the method according to the invention for display of speed information in a vehicle. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     One embodiment of a method for display of speed information in a vehicle is shown in FIG. 1 a . The region or area in which the vehicle is located is determined in locating step  1 . This region or area can be, for example, a state, a country or a city or metropolitan region, in which respective predetermined speed limits exist for corresponding road or street types. Furthermore, parts of the region or area may have special speed limits, for example the so-called tempo-30-zones or work zones. A first decision step  2  occurs following the locating step  1 . Whether or not the vehicle has crossed the boundary of the region or area in which the last test was performed is tested in the first decision step  2 . If the vehicle has crossed a region boundary or if there is no current region or area in memory, for example, if it is the first time that the method according to the invention is being performed, the method branches to adjustment step  3 . An adjustment of the display device for display of the actual vehicle speed and/or the allowed speed limits occurs in the adjustment step  3 . After the adjustment step  3  the method proceeds or branches to a second decision step  4 . Like the first decision step  2  the second decision step  4  branches according to whether or not the region boundaries in which the vehicle is traveling have been crossed. With the aid of the position of the vehicle determined in the locating step  1  in the second decision step  4  whether or not the vehicle is in a boundary zone of the region or area is determined. If that is the case, then the method branches to the method step  5 . In the method step  5  a first time interval (pause) is established, after which the method according to the invention is restarted the next time. This first time interval is dependent on the size of the boundary zone and the average speed of the vehicle passing through it. Since a vehicle navigation device performs the locating step  1  and also the navigation process for the driver of the vehicle, the entire process according to the invention can frequently also be performed by this device, when the vehicle navigation requires frequent position determination. When it is established in the second decision step that the vehicle is not located in a boundary zone of the region, a second time interval or pause is set up in step  6  which is greater than the first time interval. For a vehicle, which e. g. moves outside of a strip of 15 km from the boundary, performing the method according to the invention after a second time interval of about 15 minutes is sufficient for the purpose of adjusting the display device. Within a boundary zone of 15 kilometers, e.g. a testing after a first time interval of about one minute is sufficient. After the first method step  5  and the second method step  6  the method ends with the halt or a pause and restart after the previously set up first and/or second time interval in step  7 . 
     The locating step  1  is shown in further detail in FIG. 1 b . For example, a GPS locating device and/or a composition navigate device determines the geographic position of the vehicle in a first position-determining step  11 , e.g. from GPS satellite signals. In a second position-locating step  12  this determined vehicle position is located on a digital map or chart that includes region boundaries, which is present in the memory in the vehicle. Finally the region in which the vehicle is located is determined from the position of the vehicle located on the digital map in a region-determining step  13 . Then the particular physical units for speed values and speed limits for that region are retrieved or otherwise obtained. 
     The display adjustment  3  performed in the method according to the invention is shown in more detail in FIG. 1 c . Data regarding the vehicle, such as weight, engine size or whether or not a trailer is attached, are transmitted in a first step  31 . The physical units for speed values and the speed limits for different classes of roads or streets in the region in which the vehicle is located are determined in a second step  32 , considering the vehicle data transmitted in the first step. The physical units for speed values and the speed limits are stored in a memory unit in the vehicle. In a third step  33 , a decision step, whether or not a current adjustment of the actual displayed vehicle speeds or the speed limits is required is tested. If an adjustment is required, the representation of the speed in the display device in the appropriate physical units is changed into the appropriate physical units in step  34 . Moreover at least one maximum speed is displayed in the display device, which is the speed limit for a particular type of street or road, so that e.g. the maximum permitted speed is 50 km/hr in places in Germany. Subsequently a warning or signaling step  35  occurs. By acoustic or optical warning the driver is advised that the display of the actual vehicle speed and/or the allowed maximum speed for at least one road class has changed. The driver might otherwise be confused by a sudden change of the display without warning. This is avoided by including the warning step  35  in the method according to the invention. After the warning step  35  the method branches or proceeds to the decision step  4  shown in FIG. 1 a. Since the second decision step is already shown in FIG. 1 a , it is only indicated with dashed lines in FIG. 1 c . The second decision step  4  is also reached from the third decision step  33  when no changes in the display are required. 
     A speed display device  101  in a motor vehicle including a speedometer is shown in FIG. 2 a . A first scale  103  with scale values  104  and first scale marks or divisions  106  are shown on the display  101  in FIG. 2 a . Only one scale value  10   104  and one first scale division  106  are designated with respective reference numbers in FIG. 2 a  for convenience and simplicity. A second scale mark  107  is especially emphasized by making it longer and wider than the first scale marks  106 . Furthermore for that purpose the scale mark  107  can be in a different color, for example red, yellow or orange, from the color of the scale marks  106 , which e.g. can be white, as the sole emphasizing means or as a highlighting means. 
     The display of speed values on the first scale  103  occurs by means of a pointer or hand  102 , which can move over the entire first scale  103 . A physical unit indicator  108  shows the physical units for the speeds indicated by means of the pointer  102 . For example, the indicated unit could be “km/hr”. A first maximum speed or speed limit symbol  105  is also displayed on the display device  101 . A driver of the vehicle is informed of the speed limit of 50 km/hr both by the second scale mark  107  and by the first speed limit symbol  105 . The display of the second scale mark  107  and the first speed limit symbol  105  can occur permanently in a region in which a maximum speed or speed limit of 50 km/hr exists for a particular class of streets, e.g. all inner city streets. Thus it is completely possible to designate the maximum posted speed by an additional display or blending in of a symbol not shown in the figures for “city” or “locality”, so that it is apparent for the directly that the street class “inner city” streets are designated. Furthermore it is also possible that then only one type of display occurs when the vehicle is located in a closed built-up region and the maximum speed there is 50 km/hr. This type of display is also possible for other road or street classes, thus e.g. for an express way or limited access high-speed highway. 
     Different views of the display device  101  are shown in FIGS. 2 b  to  2   d . The respective views differ from that of FIG. 2 a  according to the method of the invention, but the same reference characters for the same elements. 
     The displace device  101  shown in FIG. 2 b  is in a state in which the physical units for the speed of the vehicle have changed to miles per hour since the vehicle has moved to a region in which those units are used. Furthermore now the speed limit in this area is 30 mph for the inner city. A second scale  113  with scale values  114  and first scale mark  116  as well as a second scale mark  117  is now shown on the display device (which of course is different from the first scale shown in FIG. 1 a  because of the change of units). The second scale mark  117  is now located on an appropriate place on the second scale  113 . The unit symbol “mph” is now displayed in the physical unit indicator  108 . Furthermore a warning symbol  115  is observable in the display device  101 , which notifies the driver of the change in the illustrated variables on the display device  101 . After a predetermined time, e.g. after about five minutes, the method assumes that the driver has been made aware of the change and thus the warning symbol is then turned off. 
     The display device  101  shown in FIG. 2 c  displays a speed limit of 80 km/hr since according to FIG. 2 a  a change in the region has taken place. The physical unit indicator  108  in this case remains unchanged from that in FIG. 2 a . A second speed limit symbol  135  and a second scale value  134  however are now displayed. Furthermore a second scale mark  137  appears at a suitable location in the first scale  103 . In addition to the change of the display device a warning tone or sound is produced which signals the driver that the speed limit has changed as a result of the change of the region in which the vehicle is located. 
     A third scale  124  with a first scale mark  127  and an associated first scale value  128  is shown on the display device  101  in FIG. 2 d . Furthermore a second scale value  124  and an associated second scale mark  127  are highlighted or emphasized, for example, by use of a color for them that is different from that used for the remainder of the display device, by enlargement and/or by widening them. A trailer symbol  129  is also visible in the display device  101 . A trailer would be detected when the vehicle data was tested and the display device  101  would then indicate the trailer symbol  129 . The third scale  123  would be adjusted, especially in regard to the scale values of the third scale, in this embodiment to a now current speed limit of 80 km/hr. The speed limit is highlighted or emphasized by the second scale mark  127 . The expansion of the scale provides the user with an improved readability for reading the actual vehicle speed. The scale expansion is permitted since the vehicle with the trailer most probably does not exceed the maximum permitted speed by about more than twice. A suitable change in a display device, as is shown in FIG. 2 d , can then occur when the regions change. This change in the display device occurs when the vehicle moves from one region, in which there is no special speed limit provided for a vehicle with a trailer, e.g. within work area, in which the speed limit is the same for all vehicle, e.g. 10 km/hr to 25 km/hr, into a region, in which a special speed limit is provided for a vehicle with a trailer. 
     If the highlighted or emphasized speed as shown in FIGS. 2 a  to  2   d  is exceeded, thus an optical and/or acoustic warning can be generated for the driver, considering predetermined speed tolerance limits. 
     An apparatus for performing the method according to the invention is shown in FIG. 3. A vehicle locating device  201  comprises a vehicle position determining device  202 , which evaluates data which it receives via a first radio antenna  204  or by means of vehicle sensors  206 . The position determining device  202  preferably is at least temporarily connected with GPS satellites by means of the first radio antenna  204 . Furthermore the locating device  101  is connected with a main processor  203 , a memory  207 , a data storage means drive  208  and a second radio antenna  205 . The locating device  201  is also connected with a display device  211  by a display processor  209  for the displayed information. The display processor  209  for the displayed information is also connected to a loud speaker  212 . 
     The locating device  201  can e.g. be part of a navigation system, which is already present in a vehicle and need not be additionally installed for the method according to the invention. The position determining unit  202  calculates the current geographic position of the vehicle from the data provided by the GPS satellites, which the locating device  201  receives via the first radio antenna  204 . The region or area (having the same predetermined speed limits and/or physical units for speed values) is determined from the current geographic position of the vehicle by means of a digital map. The digital map correlates respective geographic positions with corresponding regions or areas and is stored in the memory  207 . The memory  207  can similarly be a hard disk or a CD drive. The main processor  203  now determines the data, which are relevant for the speed display device, by means of vehicle sensors  206 . For example, besides the actual vehicle speed, whether or not a trailer is attached, whether or not fog lights are lit and whether or not chains are being used are also relevant data. If these latter conditions exist, special speed limits for the vehicle are provided. Furthermore the main processor  203  determines which physical units are used for the vehicle speed values from the location of the vehicle on the digital map. Furthermore the main processor  203  determines the speed limits for the individual classes of streets and roads in the region in which the vehicle is located, i.e. the speed limits for the express way or freeway, high speed highway, country road, residential street or inner city street. The vehicle data received from the vehicle sensors  206  are considered. These data are input to the display processor  209 , which especially controls the display device  211 . When a change of the display occurs, an acoustic warning is generated by means of the loud speaker  212 . The display device  211  now may show a changed speed scale, changed scale values, changed physical units as well as additional warning symbols and/or speed limit symbols. The display device  211  comprises a display controller and a display medium, for example a display screen provided by a liquid crystal display device, a plasma screen or a cathode ray tube. The embodiments with the display screen permit a very simple change of the display by means of the method according to the invention, since the display device  211  only needs to show a different image in the display screen. 
     Furthermore it is also possible to use a commercial combined apparatus with mechanical display elements for the display device  211 . The control of the pointer  102  must then be adjusted to the suitable physical units shown in the physical unit indicator  108 . The physical units are shown in a small display device or by a characteristic illuminated symbol field in the primary display device. For example, a speed limit can be made visible by background lighting in a different color at the scale mark associated with the corresponding speed limit. Warning symbols and/or speed limit symbols can be displayed by means of a plurality of individually controllable symbol fields on the display device. 
     The speed limit data stored in the memory  207  may be updated by means of the second radio connection  205 , so that a driver is not given incorrect information. It is also possible to update the speed limit information by means of a data carrier or storage medium, such as CD. This data carrier would be inserted in a data carrier drive  208 . It would store actual information regarding the latest allowed speed limits in various regions, including the physical units for the speed limit values. For the situation in which it is not possible to determine the vehicle location, for example when it is inside of a parking garage, the display device  209  displays information from the display that occurred at the last time when it was possible to determine the location of the vehicle. 
     The term “region” means an area of the earth having governmentally defined boundaries over which the vehicle may travel and in which at least the governmentally prescribed physical units of speed values are the same and in preferred embodiments the speed limits on the same type of streets or roads are the same. 
     The disclosure in German Patent Application 199 50 156.4-51 of Oct. 19, 1999 is incorporated here by reference. This German Patent Application describes the invention described hereinabove and claimed in the claims appended hereinbelow and provides the basis for a claim of priority for the instant invention under 35 U.S.C. 119. 
     While the invention has been illustrated and described as embodied in a method of automatically adjusting a vehicle speed display according to vehicle location, it is not intended to be limited to the details shown, since various modifications and changes may be made without departing in any way from the spirit of the present invention. 
     Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention. 
     What is claimed is new and is set forth in the following appended claims.