Navigation system for vehicles

Abstract: In a vehicular navigation system for suggesting a route to a destination according to an already set route with the purpose of searching the optimal route in response to changes of traffic conditions near the present position of the vehicle, the system comprises a present position calculating means 4A for calculating the present position of the vehicle, an information storage unit 3 for storing suggested road data 3B for suggesting the route, a traffic information acquiring means 4F for acquiring traffic information 5, a route searching means 4B for searching the optimal route from the present position to the destination based on a navigation program 3A, the suggested road data, and the acquired traffic information, and an area setting means 4C for setting a given range near the present position of the vehicle, whereby said route searching means selects and acquires traffic information corresponding to the suggested road data within the preset area among the suggested road data, and searches the route by converting the suggested road data based on the acquired traffic information.

Description: The present invention relates to a technical field of a vehicular navigation system, by which it is possible to search the optimal route from the present position of the automotive vehicle to a destination and to guide the vehicle along the optimal route to the destination. The vehicular navigation system searches a route from the present position or from the starting point to the destination based on input of data such as destination data and suggests a route according to the searched optimal route, thus providing a driver with information on the route to the destination when the driver is driving the vehicle on an unknown or an unfamiliar route. In this route searching, if the driver encounters traffic congestion or traffic restriction on the way, the optimal route can be searched again. For example, it is proposed in JP-A-7-182596 or JP-A-62-95423 that, in case traffic information such as traffic jam information is received and a congested section point is detected ahead of the advancing route on the optimal route already set, it is tried to advise not to pass through the congested section or to make it difficult to pass through the congested section by increasing cost (e.g. length) of road data of that section and to search again another route to avoid the congested section. In JP-A-6-186049, it is disclosed that a route from the present position to the destination is searched again with respect to the route already suggested by adding VICS (Vehicle Information & Communication System) information. In the system as disclosed by the above JP-A-7-182596 and JP-A-62-95423, it is described that, only in case where there is traffic jam information on the already suggested route, the road data of the route is updated and the route is searched again. In case traffic jam information is detected on a route ahead of the advancing direction during route guidance and the destination can be reached earlier if the vehicle runs along a byroad or makes a detour, the system is effective to find out such a byroad or a detour. However, when the presently suggested route has been searched by adding traffic jam information and it has been suggested at the searching to make a detour of a main road because the main road, usually not jammed, is currently jammed because of construction work or traffic accident as shown in Fig. 15 (A), and in case the traffic jam has been already dissolved while the vehicle was running along the already suggested route, such information is not given even though the vehicle can reach the destination earlier by running along the main road. Also, in the system proposed in JP-A-6-186049, the above system is disadvantageous in that much time is required for searching the route because re-searching must be carried out by adding traffic jam information on a wide area including the present position and the destination, thereby traffic jam information of zones remote from the present position and unnecessary for the searching is also added. Incidentally, VICS is now in the stage of practical application and its service area is gradually expanding. Thus, it is an important problem how efficiently real-time road traffic information can be utilized for searching an optimal navigation route within short time. To solve the above problems, it is an object of the present invention to provide a vehicular navigation system, by which it is possible to search the optimal route within short time based upon changes of traffic conditions near the present position of the vehicle. To attain the above object, as shown in Fig. 1 (A), the vehicular navigation system according to Claim 1 of the present invention for suggesting a route to a destination inputted according to an already set route comprises a present position calculating means 4A for calculating the present position of the vehicle, an information storage unit 3 for storing a suggested road data 3B for searching the route, a traffic information acquiring means 4F for acquiring a traffic information 5, a route searching means 4B for searching the optimal route from the present position to the destination according to a navigation program 3A, said suggested road data 3B and said acquired traffic information 5, and an area setting means 4C for setting a given range of area near the present position of the vehicle, whereby said route searching means 4B selects and acquires traffic information corresponding to the suggested road data within the preset area among said suggested road data 3B, and searches the route by converting the suggested road data based on the traffic information thus acquired. Also, as shown in Fig. 1 (B), the vehicular navigation system according to Claim 2 of the present invention for suggesting a route to a destination inputted according to the preset route comprises a present position calculating means 4A for calculating the present position of the vehicle, an information storage unit 3 for storing a suggested road data 3B for searching the route, a traffic information acquiring means 4F for acquiring a traffic information 5, a route searching means 4B for searching the optimal route from the present position to the destination according to a navigation program 3A, said suggested road data and said acquired traffic information, and an area setting means 4C for setting a given range of area near the present position of the vehicle, a neighborhood searching data acquiring means 4D for acquiring the suggested road data 3B within the preset area, and a neighborhood searching data memory means 4E for storing said acquired neighborhood searching data, whereby said route searching rneans 4B selects and acquires traffic information corresponding to the neighborhood searching data and searches the route by converting the neighborhood searching data based on the acquired traffic information 5. According to the present invention, an area including the present position is set and traffic information is acquired on data of roads within said area, and if traffic congestion information is detected on said road data, the traffic congestion information is added. Therefore, it is possible to search the optimal route not only according to changes on the route where the vehicle is currently running but also according to changes of traffic conditions near the present position because the route is searched again. For example, searching can be carried out again even in case where a route had been suggested because traffic congestion was found on the other road at the time of the initial searching, while traffic congestion on said other road has been dissolved during driving and it is judged that the destination can be reached earlier if the vehicle is driven along said other road from the present position. Traffic congestion information is changing every moment while the vehicle is driven and traffic congestion information of a road remote from the present position is unnecessary. In the present invention, traffic congestion information on the road near the present position is acquired and road data is updated. Accordingly, it is possible to select only useful information, to perform re-searching for finding the optimal route, and to shorten the processing time. Fig. 1 is a block diagram of a vehicular navigation system according to the present invention; Fig. 2 is a general block diagram showing an example of the vehicular navigation system, to which the present invention is applied; Fig. 3 shows a suggested road searching data file of the present invention; Fig. 4 show VICS transmitting data in the present invention; Fig. 5 represents drawings for explaining an example, in which road data of an information storage unit of the present invention is linked to the VICS transmitting data; Fig. 6 is a chart for explaining a flow of the entire vehicular navigation system according to the present invention; Fig. 7 is a drawing for explaining suggested road numbering data acquired by the route searching of Fig. 6; Fig. 8 is a flow chart showing a processing of neighborhood searching data setting in Fig. 6; Fig. 9 is a diagram for explaining setting of a neighborhood area for acquiring neighborhood searching data of Fig. 8; Fig. 10 is a flow chart showing a processing of acquisition of traffic information of Fig. 6; Fig. 11 is a drawing for explaining conversion of searching cost of traffic jam information in the processing of Fig. 10; Fig. 12 is a flow chart to show re-search processing in Fig. 6; Fig. 13 is a flow chart to show an aspect of another embodiment of re-search processing in the present invention; Fig. 14 represents drawings for showing another embodiment for setting a neighborhood area; Fig. 15 represents drawings for explaining a concrete example of effects of the present invention; Fig. 16 is a drawing for explaining an example of route category selection screen related to a variation of the present invention; Fig. 17 is a drawing for explaining an example of searching condition input screen related to a variation of the present invention; Fig. 18 is a drawing for explaining an example of facility data registered for each category related to a variation of the present invention; Fig. 19 is a drawing for explaining optimal route searching mode passing through a utilization facility related to a variation of the present invention; Fig. 20 is a drawing to show an example of how to determine a searching range related to a variation of the present invention; Fig. 21 is a flow chart to show a main routine of a flow of processing from route searching to route guidance related to a variation of the present invention; Fig. 22 is a flow chart showing a subroutine (A-1) for optimal route searching of the main routine related to a variation of the present invention; Fig. 23 is a flow chart to show a subroutine (A-2) when searching condition for the subroutine (A-1) is set; and Fig. 24 is a flow chart to show a subroutine (B) for route searching by taking road conditions of the subroutine (A-1) into account. In the following, description will be given on embodiments of the present invention in connection with the drawings. Fig. 2 represents a general block diagram of an example of a vehicular navigation system, to which the present invention is applied. The vehicular navigation system according to the present invention comprises an input/output unit 1 for inputting and outputting information related to route guidance, a present position detecting unit 2 for detecting or receiving information relating to the present position of the vehicle, and an information storage unit 3 for storing navigation data necessary for calculating the route, display/audio guiding data required for route guidance and program (OS and/or application), etc., and a central processing unit 4 for performing display/audio guidance processing necessary for route search processing and route guidance and also for controlling the entire system. First, description will be given on arrangement of each component. The input/output unit 1 instructs navigation processing to the central processing unit 4 by intention of the driver so that guiding information can be given from at least one of audio data and/or screen data when the driver considers as necessary and also prints out the data after the processing. As the means to fulfill these functions, the input unit comprises a touch switch 11 and an operating switch for inputting the destination data on telephone number or on coordinate on a map or for requesting route guidance. Naturally, it may be an input unit such as a remote controller. The output unit comprises a display unit 12 for displaying the inputted data on screen or for automatically displaying route guidance on screen in response to a request of the driver, a printer for printing out data processed at the central processing unit 4 or data stored in the information storage unit 3, and a speaker 16 for issuing audio information of route guidance. Here, a voice recognizing unit for achieving voice input or a recording card reader for reading data recorded on an IC card or a magnetic card may be-added. Or, a data communication unit may be added, which is used to send or receive data to or from an information source such as personal computer where data specific to the driver such as map data, destination data, etc. are stored. The display unit 12 comprises a color CRT and a color liquid crystal display unit and outputs color display pictures necessary for navigation such as a route setting picture, a sector map picture, an intersection picture, based on map data and guidance data processed by the central processing unit 4. It also displays buttons for setting the route guidance, guiding in the route guidance or switching of pictures. In particular, transit intersection information such as transit intersection name is given in pop art color display on the sector map picture as necessary. This display unit 12 is provided in an installment panel near the driver's seat. The driver can confirm the present position of the vehicle by watching the displayed map and can acquire information on the route, along which the vehicle should be driven. Also, a touch switch (input unit) 11 to match the display of functional button is provided on the display unit 12, and by touching the button, a signal is inputted to carry out the above operation. The input signal generating means consisting of this button and the touch switch 11 constitutes an input unit, but detailed description is not given here. The present position sensing unit 2 senses or receives information related to the present position of the automotive vehicle, and it comprises an absolute heading sensor 24 having a geomagnetic sensor and the like, a relative heading sensor 25 having a steering sensor, gyro, etc., a distance sensor 26 for detecting running distance for number of revolutions of wheels, a GPS receiver 21 utilizing satellite navigation system or global positioning system (GPS), and a communication unit 5. The communication unit 5 comprises a VICS receiver 22, serving as traffic information acquiring means, or a data transceiver 23. The VICS receiver 22 receives road traffic information by means of FM multiplex, radio beacon, optical beacon, and the data transceiver 23 is, for example, a portable telephone set or a personal computer. Information necessary for navigation is sent to or received from a traffic information center (such as ATIS) at a request of the driver. The information storage unit 3 is an external storage unit where navigation program and data are stored in an external storage medium such as CD-ROM (hereinafter simply referred as "CD"), optical CD, IC card, etc. The navigation program comprises a map drawing unit, a route searching unit, a route guidance unit, a present position calculating unit, a destination setting operation control unit, etc. It has an application sector for processing signal of navigation and an OS sector. Here, programs for executing processings such as route searching, display output control necessary for route guidance, programs for carrying out audio output control necessary for audio guidance and data necessary for it, and further, display information data necessary for route guidance and map display are stored. Also, all data necessary for navigation such as map data, intersection data, road data, various types of guidance data, etc. are stored. More concretely, a program for setting a destination or a transit point based on position information from the present position sensing unit 2 or on input signal from the input unit 11 and for executing route searching using the suggested road data, a program for converting the suggested road data based on traffic information acquired from the communication unit 5 and for executing the route searching again, and a program for determining audio output timing or content of audio phrase along the route are stored. By starting the programs stored in the information storage unit 3, functions for navigation in the present invention are carried out. In an aspect of the present embodiment, programs for executing the functions of the present invention are stored in the information storage unit 3, which is an external storage medium. The central processing unit 4 comprises a CPU 40 for executing various arithmetic operations and a flash memory 41 for reading and storing programs from CD of the information storage unit 3. The flash memory 41 erases the existing program and makes it reloadable even when programs on CD have been changed. There are provided a first ROM 43a for storing programs to perform program check of the flash memory 41 and to update (program reading means), a RAM 42 for temporarily storing route guidance information such as coordinates of the preset destination, road code number, etc. or data under arithmetic processing, and a second ROM 43b where display information data necessary for route guidance and map display are stored. The programs for updating as described above may be stored in the external storage unit. Further, there are provided an image memory 44 for storing image data used for screen display to display unit, an image processor 45 for picking up image data from the image memory based on display control signal from the CPU 40 and for outputting to the display unit 12 after image processing, an audio processor 46 synthesizing audio phrase read from RAM 42 based on audio output control signal from CPU 40 and sentence, sound, etc. getting together and for converting them to analog signal and for outputting them to the speaker 16, a communication interface 47 to send or receive input/output data to or from the communication unit 5, a sensor input interface 48 for picking up sensor signal of the present position sensing unit 2, and a clock 49 for registering data and time to internal dialog information. In the central processing unit 4, when the data acquired by each sensor in the present position sensing unit 2 is received through the sensor input interface 48, CPU 40 calculates coordinates of the present position at constant interval based on these data, and the results are temporarily written in RAM 42. The present position coordinates are the ones processed by map matching, taking detection error of each data into account. Output values of each type of sensor are corrected at all times. Route guidance is performed by screen display and audio output. The driver can select whether audio output is to be given or not. Fig. 3 shows a suggested road (guidance) data file where data necessary for calculating the route by route searching unit and for carrying out route guidance are stored. Fig. 3 (A) shows data structure, and Fig. 3 (B) represents a diagram for explaining the data. In the present invention, as shown in Fig. 9, the suggested road data are divided into a plurality of blocks Bn, each covering an area of 3 to 10 km in radius, and the data are controlled for each block. For each of block numbers (from 1 to n), there are road numbers (1 to m). For each road number, there are data including coordinates of the starting point and the terminal point, roads having the same starting point, roads having the same terminal point, length, road attribute, width, road not requiring guidance, prohibition information such as no entry, one way, etc., address and size of node data etc. The above road number is set to outward course and return course for each road between intersections (branch points). The road attribute is the data indicating information on road type such as a national road, an overpass, an underpass, number of lanes, etc. The node data is coordinate data, which consists of longitude and latitude data of each of the node number when the road is divided into a plurality of nodes. Fig. 4 shows transmitting data transmitted from VICS. VICS transmits road traffic information at real time by means of FM multiplex, radio beacon, and optical beacon to each vehicle. FM multiplex transits crude information over a very wide area, while radio beacon and optical beacon provide detailed information for a narrow area within about 10 km in radius around the position where the beacon is installed. The information is received when the vehicle passes through the installed position of the beacon. To each link number assigned to each road, VICS transmitting data include degree of congestion (e.g. closed to traffic, congested, jammed, heavy traffic, normal traffic, etc.), the foremost position of congested section, length of congested section, traffic restriction (construction information, closed to traffic, etc.), and traveling time (time required when running at the predetermined speed). In addition, traffic information may be acquired by making access to the traffic information center (such as ATIS) by means of the data transceiver (such as portable telephone) 23. In so doing, traffic information can be acquired whenever the user wants to have such information, and the optimal route can be requested based on the traffic information. Incidentally, the road data of Fig. 3 stored in CD of the information storage unit 3 does not generally correspond at 1:1 to the link number of VICS in Fig. 4, and it is necessary to make them match each other. Fig. 5 (A) is a correspondence table, showing how the link number transmitted from VICS corresponds to the link of the road data stored in CD, and Fig. 5 (B) is given for explaining such correspondence. Specifically, as shown in Fig. 5 (B), CD link numbers 3, 4 and 5 are linked so that the road having VICS link number 1 corresponds to the road numbers 3, 4 and 5 in CD-ROM. The linking mode is not limited to the above, and the link number transmitted from VICS and the road data stored in CD may be coordinated in advance. In this case, a frame for storing the data relating to congestion information of VICS may be provided in the suggested road data shown in Fig. 3, and the data obtained from VICS may be stored in it as the suggested road data. Fig. 6 is a flow chart for explaining a flow of the entire vehicular navigation system of the present invention. When the navigation program is started by CPU 40 of the central processing unit 4, the present position is detected by the present position sensing unit 2. A map of the neighborhood around the present position is displayed, and the present position (starting point) data is acquired (Step S1). Next, the destination is set using telephone number, address, facility name, registered place, etc. (Step S2), and route searching (initial searching) from the present position to the destination (Step S3) is carried out. The route to the destination is set as a guidance road number data as road number string for guidance as shown in Fig. 7. When the route is determined, guidance/display of the route to the destination are carried out while tracing the present position by the present position sensing unit 2 (Steps S4 and S5). Next, after the predetermined time has elapsed, processings for the neighborhood searching data setting and traffic information acquisition are performed (Steps S6 - S8). Fig. 8 shows a flow of processing of the neighborhood searching data setting of Step S7 in Fig. 6, and Fig. 9 is a diagram for explaining setting of an area to acquire the neighborhood searching data of Fig. 8. After the road data of the present position of the vehicle has been acquired in Step S14, it is judged which block the present position P (Fig. 9) belongs to (Step S15) and in Step S16, it is judged whether this is the first time to acquire the neighborhood searching data or not. If it is the first time, it should proceed to Step S18. If not, it is judged whether the block of the present position has changed or not from the last time in Step S17. If not changed, it should proceed to the next processing. If changed, proceed to Step S18. Then, in Step S18, the road data of the block, to which the present position belongs, and an area BA (Fig. 9) including 9 blocks adjacent to this block is acquired, and it is stored in the memory (RAM 42) as the neighborhood searching data. The processing in Fig. 8 is to set an area for acquiring the neighborhood searching data to select traffic information corresponding to the neighborhood searching data (to be described later), while this may be applied for setting an area to select neighborhood information for searching among the traffic information acquired. In such case, the suggested road data is converted based on the acquired traffic information to search the route. Returning to Step S8 in Fig. 6, the processing of VICS traffic information acquisition is carried out. This is explained referring to Fig. 10. In Step S30, it is judged whether FM multiplex broadcasting has been received or not. If received, VICS data is stored in memory (Step S31), and it is judged whether beacon has been received in Step S32. If received, VICS data is stored in memory (Step S33). Next, the present position data is acquired in Step S34, and neighborhood searching data of an area BA of 9 blocks near the present position as explained in Fig. 8 and Fig. 9 is acquired in Step S35. Next, number of blocks of VICS congestion information already at hand is acquired in Step S36, and it is judged in Step S37 whether it is a block in the area where the block has been acquired. If it is a block in the area, it should proceed to Step S39. If not, data is deleted for each block. The processings in Steps S36 to S38 are such that, in case congestion information is stored for 4 blocks among the previous 9 blocks, for example, it is turned to n = 4 and those blocks overlapped on the current 9 blocks are acquired. Next, based on VICS information in the neighborhood area as set in Step S39, the suggested road data is converted. If there is congestion information on the road with VICS link number 1 as explained in Fig. 5, weighted constant α 1 , α 2 or α 3 is added to CD link number or it is multiplied by weighting coefficient to increase searching cost of the road data according to the degree of congestion information. More concretely, converted distance of the road corresponding to CD link number with congestion information is increased. In case there is traffic restriction information such as "closed to traffic", the value of α is increased to infinity to make the road not selectable. In the above, cost is changed and data is converted for the suggested road data based on congestion information, while coefficient may be used to multiply the road data where congestion information is acquired during execution of route searching. Description is now given on the above searching cost. In general, the searching cost is set by required passing time, distance, easiness to drive (such as road width, type of road such as national road), and toll for that road (number). Therefore, if the searching cost has been set by distance, for instance, the data of easiness to drive such as difference of road width, type of road, etc. are converted to distance. Even when the physical length is the same, converted distance is shorter in expressway than in main road, for instance, while it is longer in branch road. In case there is congestion information as described above with respect to the converted distance, distance is increased by a constant value or by a multiplying factor and the searching cost is increased to make it difficult to select that road from the candidate roads for the optimal route. Next, the data acquired previously is checked in Step S40. This is to maintain the effective information among the congestion information acquired previously and already stored and to make it reflected in the searching. More concretely, for example, in case the data acquired previously is detailed information by beacon and the information acquired this time is crude data by FM multiplex, the previous data is maintained without updating. Naturally, if the data acquired this time and the data previously acquired are identical with each other and there is change in the data, the currently acquired data is considered effective. The data thus acquired is controlled for each block as neighborhood searching data in Step S41. When the above processing of traffic information acquisition has been completed, it is judged whether there is traffic congestion in the neighborhood area set in Step S9 of Fig. 6. If there is no congestion, proceed to Step S10. If there is congestion, re-searching processing of Step S11 is carried out. This is explained referring to Fig. 12. First, the neighborhood searching data of the present position of the vehicle is read (VICS conversion data in Fig. 11) in Step S51. The previous guidance route string (guidance road number data of Fig. 7) is acquired, and advancing direction at each intersection in the direction returning to the previously suggested route and the searching cost are calculated in Step S53. This is calculated in such manner as to reduce the searching cost of the road to return toward the advancing direction, for example. Next, the road and the direction of the present position of the vehicle are acquired in Step S54, and an intersection connected to the road of the present position in advancing direction is selected in Step S55. Based on the advancing direction to each intersection and the searching cost, a route to return to the previously suggested route is determined, and a suggested route road string is re-prepared in Step S56. When the above re-searching processing has been completed, it is judged whether the re-searched route is different from the previous route or not in Step S12 of Fig. 6. It not different, proceed to Step S10. If different, the route should be rewritten. It is then judged whether the destination can be reached or not in Step S10, and the processings of Steps S4 to S13 are repeated until the destination is reached. Fig. 13 is a flow chart to show a processing in another embodiment of the re-search processing according to the present invention. In the re-search processing explained in Fig. 12, searching is carried out only by neighborhood searching data, and a route to avoid traffic congestion ahead of the road may not be searched in some cases. Therefore, in the embodiment shown in Fig. 13, the road and the direction of the present position of the vehicle are acquired in Step S61, and a destination road is acquired in Step S62. Then, suggested road data between the present position and the destination is read in Step S63. In this case, the data converted by VICS is used as the neighborhood searching data, and the data stored in advance is used for the other data. In Step S64, an intersection connected to the road of the present position in advancing direction is selected. Based on the advancing direction up to each intersection and the searching cost, all routes leading to the destination are determined, and the suggested route road string is re-prepared in Step S65. Further, in case a route connected to the initial route avoiding traffic congestion in advancing direction cannot be searched by the neighborhood searching data only, the initial route may be maintained on display and may be used as an inductive route, or the area of the neighborhood searching data currently stored may be enlarged. Or, it may be switched over to all-route searching to the destination as shown in Fig. 13. Fig. 14 shows another embodiment to acquire the neighborhood searching data. In case the area is set in blocks as shown in the above embodiment, processing can be carried out faster, while there is difference in the range ahead of the present position in the upper and the lower portions of the block. In Fig. 14 (A), it is tried to acquire the data within a given distance from the present position. More concretely, such a data is acquired, in which coordinates of the terminal point (either the starting point or the end point, or both) and coordinates of the present position are within a given distance. In Fig. 14 (B), priority is given on searching in an area ahead in advancing direction (because the vehicle is rarely driven backward), and the position serving as reference in form of rectangle or circle is set within a given distance from a point ahead of the present position. More concretely, ahead in advancing direction by a given distance (in straight line) or from the present position, a point serving as reference ahead of the present position by a given distance is offset. In Fig. 14 (C), based on the advancing direction of the present position, data of a fan-shaped area is acquired at a given angle. Fig. 15 represents drawings for explaining examples of effects of the present invention. As shown in Fig. 15 (A), in case traffic congestion data in main road was received and a route bypassing a general road (thick line) was re-searched as the optimal route, and if an information is received, which indicates that traffic congestion on the main road has been dissolved at the time point when the vehicle P has advanced to a position shown in Fig. 15 (B), the main road can be re-searched and suggested as the optimal route. In the above, description has been given on embodiments of the present invention, while it is needless to say that the present invention is not limited to the above embodiments, and various changes can be made. For example, the acquisition of traffic information in Step S8 of Fig. 6 may be carried out after the setting of the destination in Step S3. Also, setting of the neighborhood data and acquisition of traffic information are carried out at a given time interval in Steps S6 to S8 in Fig. 6, while these processing may be carried out at a point before a branch point of an intersection by a given distance. When traffic congestion has been detected in a nearby area in Step S9 of Fig. 6, the information may be notified by audio output or screen display, or when the present route has been changed in Step S13, the change may be notified by audio output or screen display. In so doing, the user can accurately recognize changes of traffic information or information such as route change. In the above embodiments, programs such as navigation programs for carrying out the present invention are stored in an external storage unit, and the programs are read in flash memory in the central processing unit to execute various processings, while the programs may be stored in ROM in the central processing unit. Further, in the above embodiments, in case information by VICS is utilized, the information transmitted from a VICS center is updated at a given time interval. Therefore, VICS information may be received at a given time interval to match the above timing. Also, it may be designed in such manner that traffic information can be acquired when information of the road with very changeable traffic conditions (e.g. expressway or main road such as national road) is added in advance to the suggested road data and such road is present in the area currently acquired. Further, in the above embodiments, initial searching is carried out in Step S3 of Fig. 6, and this route is regarded as an inductive road, while the route may be inputted manually. Also, traffic information may be added or may not be added to the initial searching. In case route searching is carried out by connecting the system with a home television set and the system is then used as a vehicular navigation system, and if some time is required until route induction is started after the initial searching, it may be designed in such manner that initial searching is carried out without adding traffic information, and after it is judged that the route induction or guidance has been started after the vehicle begins to be driven, the traffic information may be added and route searching may be carried out as described in the above embodiments. Next, description will be given on a variation of the present invention referring to Figs. 16 to 24. This variation relates particularly to a vehicular navigation system, by which it is possible to find out a filling station or a convenience store near the present position of the vehicle by inputting the intended purpose and to search the optimal route passing by the searched facility by considering road conditions such as traffic congestion information acquired from outside. As such a vehicular navigation system, it has been proposed a system, by which it is possible to calculate the route from the present position to the destination utilizing external information and to determine the optimal route from a plurality of routes thus calculated. It is sometimes tried to find out facilities for filling fuel or getting some food and drinks on the way to the destination using a vehicular navigation system. In such case, it is necessary to search the facility for each intended purpose by retrieval function. As the result of the retrieval, there are the cases where there is no candidate facility on the route or such facility is at a point deviated from the suggested route. When it is necessary to go out of the suggested route to go to the facility, re-searching is carried out to find a route having such facility as a transit point. A vehicular navigation system having such a function is proposed, for example, in JP-A-2-3899. For example, in case it is wanted to stop at a filling station on the way, the user must select a facility from a plurality of filling stations, and the selected station must be set as a destination. In case it is set as a transit point, the user may not be able to obtain information on the filling station selected as the optimal because dynamic information (such as traffic congestion) of the road is not available. Accordingly, even when the user can drive the vehicle smoothly from the present position to the filling station, the user finds trouble if there is traffic jam on the route from the filling station to the destination. Or, the restaurant as originally selected may be closed because of holiday or because it is out of business hour, and re-searching must be carried out, or the restaurant may be too crowded and much time may be required for waiting. In this way, unless business information of the selected facility is not added, the user may waste much time and may arrive the destination much later than originally expected. It is an object of the present variation of the invention to provide a vehicular navigation system, by which it is possible to guide the vehicle along the optimal route to the destination by setting the selected facility to visit on the way as a transit point and by considering road conditions acquired from outside. It is another object of the variation of the present invention to provide a vehicular navigation system, by which it is possible to guide to the destination along the optimal route by setting the selected facility to visit on the way to the destination as a transit point and by considering road condition acquired from outside, and by adding information relating to the selected facility. To attain the above objects, a first aspect of the variation of the present invention comprises a destination setting means for setting a destination, an intended purpose inputting means for inputting the intended purpose, a first memory means for storing map information and guidance information, a second memory means for receiving and storing road conditions such as traffic congestion outside information, a present position sensing means for sensing the position of the vehicle, a facility searching means for searching near a facility search base point based on the intended purpose inputted by the intended purpose inputting means, and a first correlation quantity calculating means for searching a route from the present position to the facility by considering outside information stored in the second memory means with respect to a facility searched by the facility searching means and for obtaining correlation quantity by said route, a second correlation quantity calculating means for searching a route from the facility to the destination by considering outside information stored in the second memory means with respect to the facility searched by the facility searching means and for obtaining correlation quantity by said route, and a facility determining means for determining the facility based on calculated value of the correlation quantity obtained by the first and the second correlation quantity calculating means. A second aspect of the variation of the present invention comprises a destination setting means for setting a destination, an intended purpose inputting means for inputting the intended purpose, a first memory means for storing map information and guidance information, a second memory means for storing map information and guidance information, a second memory means for receiving and storing road conditions such as traffic congestion as outside information, a third memory means for storing information relating to the suggested facility, a present position sensing means for sensing the present position of the vehicle, a facility searching means for searching the facility near a facility search base point based on the intended purpose inputted by the intended purpose inputting means, a first correlation quantity calculating means for searching a route from the present position to the facility by considering outside information stored in the second memory means and using the information relating to the suggested facility stored in the third memory means as judging condition with respect to the facility searched by the facility searching means and for obtaining correlation quantity by said route, a second correlation quantity calculating means for searching a route from the facility to the destination by considering outside information stored in the second memory means and using the information relating to the suggested facility stored in the third memory means as judging condition with respect to the facility searched by the facility searching means and for obtaining correlation quantity by said route, and a facility determining means for determining the facility based on calculated value of correlation quantity calculating means. A third aspect of the variation of the present invention is identical with the system according to the first and the second aspects of the invention, wherein there is provided a searching condition inputting means for inputting searching condition including a facility searching base point, said facility searching means searches the facility based on searching condition inputted from the searching condition inputting means. By the above arrangement, it is possible to search a facility corresponding to the intended purpose based on guidance information stored in advance by the facility searching means when the intended purpose is inputted by the intended purpose inputting means in case the user wants to go to a facility such as a filling station, a convenience store, etc. on the way to the destination. Also, it is possible to calculate correlation quantity from the present position to the facility with the facility as a transit point and based on correlation quantity from the facility to the destination by considering road conditions such as traffic jam information acquired form outside by the first and the second correlation quantity calculating means and by adding information relating to the selected facility to the road conditions. Further, the facility determining means determines the optimal facility from calculated value of correlation quantity obtained. In case the searching condition inputting means is provided, the present position or the destination can be set as the facility search base point, or the time required can be set, and the optimal route searching can be carried out. According to the present variation of the invention, the user can arrive the facility within short time on the way from the present position to the destination without selecting by himself because the route with the shorter time required is searched and suggested when the user wants to visit such facility on the way to the destination. In the present system, an estimated position can be calculated based upon various types of sensor signals and GPS data for sensing the present position of the vehicle, and the present position is determined by finding the position on the road through correlation of the estimated position and road and GPS data on map. Also, the present system is provided with a function to judge whether the vehicle is approaching the suggested point already set with respect to the position of the vehicle on road lane. Specifically, timing for intersection information display output data such as distance before the intersection on the suggested route, automatic audio output such as intersection passing judgment, or passing intersection name is judged. Based upon the results of the judgment, guidance command is issued to the image processor and the audio processor. When the request signal is inputted, audio guidance of the present position is issued to the audio processor. In the audio guidance of the present system, audio data read from the information storage unit 3 (phrase; sentence, sound, etc. put together) are synthesized and are converted to analog signals to output from the audio output unit. Next, description will be given on the function of electronic control unit for carrying out the optimal route searching with a facility to visit on the way as a transit point. Fig. 16 represents an example of a category selection screen. Fig. 17 shows an example of a searching condition inputting screen. A selection screen 5A comprises a selection key 50 for selecting a facility classified for the intended purpose, and a searching condition specifying key 51 for specifying whether searching condition to the selected facility is set or not. When category of the facility is selected on the selection screen and the column "no searching condition" is specified, searching of the facility is started based on the facility search base point determined in advance (normally, the present position). When the category of the facility is selected and the column "searching condition present" is specified, the searching condition input screen as shown in Fig. 17 appears. On the searching condition input screen 6A, there are provided a facility search base point specifying key 60 for specifying at which point searching of the facility is to be specified, a designation specifying key 62 for specifying the time required to arrive the facility to be utilized. In the present example, a filling station with a designation "JOMO" has been selected near the destination within 30 minutes from the present position. When the user wants to visit a filling station or a convenience store while driving to the destination, and if the facility is selected on the screen and the searching condition is set, it is possible to search a facility near the facility search base point such as the present position of the vehicle and to suggest the optimal route searching to the destination via such facility. This route searching is executed by taking the received road condition into account. The facility searching data. include facility name data, position (coordinate) data, road data, designation data, business data, etc. for each facility classified by category as shown in Fig. 18. As the business data, data such as business day, business starting time, business termination time, crowded hours, etc. are included. In searching the facility having the above business data such as restaurant, it is possible to exclude the facilities out of business hours or in crowded hours or to give information on average waiting time at the facility when the facility in crowded business hours is included in the candidate facilities. In the utilization mode of business data, the driving time to the selected facility is obtained to determine expected time of arrival at the selected facility based on the driving time and the present time. By comparing and calculating the expected time of arrival and business data, the procedure of processing for the facility is determined based on the conditions. Specifically, from the results of calculation, it is judged whether the expected time of arrival falls within the crowded hours or within business hours, and the facilities not complying with the conditions are exempted. Or, if it is within the crowded hours, driver will be notified of the fact and can judge whether to go there or not. In particular, it is possible to store an internal information stored in the information storage unit 3 provided in the system shown in Fig. 2, or to receive the information by the data transceiver 23 in the present position sensing unit 2 from the information center, for example, and to store the information in a non-volatile memory as outside information. By acquiring such variable information from outside, it is possible to rewrite the data regularly and to search the facility based upon the most up-to-date data. Based on the selected category, the facility with a given range near the facility search base point is searched, and route searching is carried out by taking information such as road conditions, business information, etc. into account. From these facilities, the optimal facility to suit the searching condition is determined. In this case, correlation quantity is obtained on the route from the present position to the facility and from the facility to the destination. For the correlation quantity, weighted value is adopted based on the values relating to the time from the present position to the facility and the time from the facility to the destination and physical road conditions such as road type, number of lanes, number of traffic signals, right turn, left turn, etc. Description will be given now on the concept of route searching using the required time as correlation quantity referring to Fig. 19. In the following, the present position is used as the facility search base point. When facilities are found, it is tried to search the optimal route to the destination via the optimal facility selected from all the facilities related. For example, if there are facilities G1 and G2, the time t1 required from the present position to the facility G1, the time t2 to the facility G2, the time T1 from the facility G1 to the destination, and the time T2 from the facility G2 to the destination are obtained. The optimal facility is selected from the time required to go to the destination via the facility G1 (t1 + T1) and the time required to go to the destination via the facility G2 (t2 + T2). To select the facility, it is possible to automatically select it based upon the preset condition from the facilities G1 and G2 or to select the facility by displaying a route via the facility G1 and a route via the facility G2 on map. Next, description will be given on procedure of processing of the present variation. Fig. 21 shows a main routine. Fig. 22 represents a subroutine for optimal transit searching. Fig. 23 shows a subroutine for route searching, taking road condition into account. In Fig. 21, acquisition of the present position (S101), setting of a destination (S102) and information on road condition are acquired from outside, and these are stored in memory (S103). Based on the information, the optimal transit route passing through the facility (transit point) is searched (S104), and the searched route is suggested and displayed (S105). By the optimal transit route searching in Step S104, the routine (A-1) shown in Fig. 22 is started. Then, the category selection screen shown in Fig. 16 is displayed, and a transit point, e.g. a filling station, is selected on this screen (S110). Then, it is specified whether there is searching condition or not (S111). In case searching condition is present, searching condition such as searching point, designation, required time, etc. is set on the searching condition input screen. As the searching condition, there are facility search base point (present position, destination), designation, required time (e.g. time in minutes), time (e.g. time in minutes after the present moment), etc. In case the time in minutes after the present moment is specified, a facility located at the closest point and attainable at the specified time (time of arrival) is searched. If there is no searching condition, transit point data near the present position (data of G1 and G2 in Fig. 19) are acquired (S112). Based on the transit point data, route searching is carried out by taking road conditions into account (S113), and the route with the shortest time required is selected (S114). When the searching condition is specified in Step S111, the optimal route searching routine (A-2) is started. As the searching condition specified in Step S111, it is judged whether the facility search base point is set or not (S120). If already set, the data near the facility search base point is acquired (S121). If not yet set, the data near the present position is acquired (S122). Next, it is judged whether the designation is set or not (S123). If designation is already set, the data agreeing with the designation is acquired from the data found in Steps S121 or S122 (S124). Next, it is judged whether judging conditions for the suggested facility (such as business hours, crowded hours) are present or not (S125). If there is no condition, the optimal route is searched, taking road condition into account (S126). From the expected time of arrival and business data, the data agreeing with the judging conditions is acquired (S127), and the optimal route is searched, taking road condition into account (S128). Here, it is judged whether the required time has been set or not as the searching condition (S129). Based on the result, the route is selected. Specifically, in case the required time has been set, the route with the required time closest to the condition is selected from the candidates of the searched routes (S130). On the other hand, in case the required time is not set, the route with the shorter required time is selected (S131). In the present variation, it is arranged that route searching is carried out based on the acquired data in Step 127. In case judging conditions for the suggested facility depend upon the selection of the driver, the following steps are added: a step to notify when it does not agree with the judging conditions, and a step to select whether route searching including said data should be carried out or not. In the route searching by taking road condition into account (Step S113), the subroutine shown in Fig. 24 is executed. The number (n) of the candidate facilities, e.g. filling stations, near the present position or near the already set facility search base point is set in advance (S140), and the shortest time from the present position to that facility is calculated by taking congestion information as road condition into account (t1 and t2 in Fig. 19) (S141). Taking congestion information from the suggested facility to the destination into account, the shortest time (T1 and T2 in fig. 19) is calculated (S142). The time required from the present position to the destination is acquired (S143). This calculation of time is carried out for a given number (n) of transit points (suggested facilities) among the candidate facilities near the present position (S144). In the above variation, "the time required" is used as selecting condition after route searching, while the time of arrival at the suggested facility may be selected. In the present variation of the invention, the following aspects of embodiment can be adopted: (1) In case there are relatively many candidate facilities, many facilities may be searched if searched in a wide range. On the other hand, if there are relatively few facilities, searching may fail if searched within a narrow range. In this way, the number of searching results may vary according to the extent of searching range, and it is preferable to arrange in such manner that the searching range can be enlarged or reduced. As a result, by reducing the searching time, it will be much easier to set the facility to be utilized. Describing the method to determine the searching range in connection with Fig. 20, it is supposed that radius of a circle for searching is 100 m around the present position, that width of the radius to be enlarged is 50 m, and that the limit of range to be enlarged is 1000 m. The limit of range can be obtained by setting the predetermined value as the initial value or it can be obtained from the distance between the present position and the destination. In case it exceeds the limit of range, the center of the range may be switched over from the present position to the destination, or it may be arranged so that a message such as "no candidate facility in the neighborhood" may be displayed. (2) It is possible to set the searching range in circular, elliptical or semi-circular shape as desired. In particular, in case elliptical or semi-circular shape is selected, it can be set in such manner that the facilities in opposite direction from (i.e. on opposite side of) the destination may not be set by reducing the searching time and it is limited only to the facilities located in the direction toward (i.e. before) the destination. (3) The searching method can be arranged in such manner that the searching range is enlarged by every 50 m in radius until the optimal facility is found as described in (1) above and the searching is terminated when it is found. (4) Another method is to search up to the limit of range and to find a route having the optimal facility as a transit point on the way. (5) To reduce the searching time, it is effective to arrange that the selecting conditions such as specified facility name, whether it is near the present position or the destination, etc. are automatically or manually set before or after the searching, or that the number of searchings or searching time is limited. In case the number of searchings is limited, priority is given to the searching range. For example, the number of searchings is limited to n = 20, and if this number of searchings is exceeded when the searching range is enlarged, the enlarging of the searching range is stopped at that moment. In particular, when the candidate facilities are automatically selected, the burden on the user can be reduced, and the user can concentrate attention on driving. When all processings are automated, working time can be reduced, and information such as road conditions, business information, etc. can be handled under the condition closer to real time. (6) In selecting the candidate facilities, for example, four routes may be displayed including the specified filling station (specified before searching), a facility near the present position, a facility near the destination as intermediate candidates, and the optimal facility is selected from these candidates. Or, about 10 routes may be displayed starting from the route with the shortest required time, and the optimal facility may be selected from these candidate routes depending upon the conditions such as the specified filling station, position, etc. (7) In choosing the facility search base point shown in Fig. 17, an arbitrary point on map may be set by specifying by cursor in addition to the present position and the destination.

Claims: A vehicular navigation system for suggesting a route to a destination inputted according to an already set route, comprising: a present position calculating means (4A) for calculating the present position of the vehicle; an information storage unit (3) for storing a suggested road data for searching a route; a traffic information acquiring means (4F) for acquiring traffic information; a route searching means (4B) for searching the optimal route from the present position to the destination based on a navigation program, said suggested road data and said acquired traffic information; and an area setting means (4C) for setting a given range of area near the present position of the vehicle, whereby: said route searching means (4B) selects and acquires traffic information corresponding to the suggested road data within the preset area, a reference point of which is the present position of the vehicle, and searches the optimal route from the present position to the destination by converting the suggested road data corresponding to the acquired traffic information. A vehicular navigation system for suggesting a route to a destination inputted according to an already set route, comprising: a present position calculating means (4A) for calculating the present position of the vehicle: an information storage unit (3) for storing a suggested road data for searching a route; a traffic information acquiring means (4F) for acquiring traffic information; a route searching means (4B) for searching the optimal route from the present position to the destination based on a navigation program, said suggested road data and said acquired traffic information; an area setting means (4C) for setting a given range of area near the present position of the vehicle, a neighborhood data acquiring means for acquiring suggested road data within said preset area, a reference point of which is the present position of the vehicle; and a neighborhood searching data memory means (4E) for storing said acquired neighborhood searching data, whereby: said route searching means (4B) selects and acquires traffic information corresponding to the neighborhood searching data and searches the optimal route from the present position to the destination by converting the neighborhood searching data corresponding to the acquired traffic information. A vehicular navigation system according to Claim 1 or 2, wherein said traffic information is acquired at a given time interval. A vehicular navigation system according to Claim 2, wherein said neighborhood searching data is acquired and updated at a given time interval. A system according to any of Claims 1 to 4, wherein said suggested road data is divided into a plurality of blocks and is stored, and said area is set for each block. A system according to any of Claims 1 to 5, wherein said area is within a given distance from the present position of the vehicle. A system according to any of Claims 1 to 6, wherein said area is within a given angle from the present position to the advancing direction. A system according to any of Claims 1 to 7, wherein said area is within a given distance from a point located ahead of the present position by a given distance and in a given direction. A system according to any of Claims 1 to 8, wherein a searching cost is added in advance to said suggested road data, and said route searching means (4B) searches the route by converting the searching cost of the road data with acquired traffic information among said suggested road data. A system according to any of Claims 1 to 9, wherein said route searching means (4B) searches the route in case it is judged that traffic information corresponding to the suggested road data within the preset area has been acquired. A system according to any of Claims 1 to 10,it is notified that traffic information corresponding to the suggested road data within the preset area has been acquired. A system according to any of Claims 1 to 11,wherein it is notified that the route has been changed in case the route searched by said route searching means has been turned to a route different from the initial route. A system according to any of Claims 2 to 12, wherein said route searching means (4B) searches the route only based on the neighborhood searching data and searches to connect to the initial route from the present position, and if connected to the initial route, the new route is considered as an inductive route, and if not connected, the initial route is considered as an inductive route. A system according to any of Claims 2 to 13, wherein said route searching means (4B) searches the route based on the neighborhood data, searches the route to connect it to the initial route from the present position, and if connected to the initial route, the new route is considered as an inductive route, and if not connected, route searching is performed with the suggested road data to the destination.

Inventors: KATO SHINICHI, MUTSUGA KATSUHIKO, KATO, SHINICHI, MUTSUGA, KATSUHIKO
Applicants: AISIN AW CO, AISIN AW CO., LTD.
Application year: 1996
Main classification: G01C21
IPC codes: G08G1, G01C21