Patent Publication Number: US-2015073636-A1

Title: Navigation device and navigation method

Description:
TECHNICAL FIELD 
     The present invention relates to a navigation device and a navigation method which perform route guidance. 
     BACKGROUND ART 
     Recently, for preserving the global environment by preventing environmental destruction and global warming, low-emission vehicles are spreading worldwide. Among others, development and sales have been encouraged especially for electric vehicles (abbreviated as EVs) which do not discharge exhaust gas. 
     Navigation devices used in vehicles including the electric vehicles have functions of searching for and displaying a route from the current position of the vehicle to a charging station equipped with a charging facility to enable charging of a battery installed in the vehicle (hereinafter, referred to as “in-vehicle battery”) at sites other than the user&#39;s house. 
     When an electric vehicle is to be used for, for example, driving a relatively long distance, the in-vehicle battery may need to be charged at the starting point, the destination, or between the starting point and the destination depending on the capacity of the in-vehicle battery or the like. For this reason, under the situation without sufficient charging facilities, the navigation devices are required to display exhaustion of battery capacity, perform guidance to a charging station, or the like while the vehicle is traveling. 
     Conventional techniques for such a navigation device are disclosed, for example, in Patent Documents 1 to 6. 
     Patent Document 1 discloses a navigation system for an electric vehicle which, when the remaining battery capacity becomes a certain level or less, calculates a distance the own vehicle is capable of traveling, and identifies a position of a charging station that is around the current position of the own vehicle according to the reachability. 
     Patent Document 2 discloses a charging station information providing apparatus which extracts a charging station that is around the current position of the electric vehicle from stored charging stations, and provides the position of the extracted charging station and availability information of chargers installed in the charging station. 
     Patent Document 3 discloses an in-vehicle navigation device which generates a charging station status icon indicative of charger usage in a charging station acquired via communication means, and displays the charging station status icon at the position of the charging station on an image of a map displaying the surroundings of the own vehicle position. 
     Patent Document 4 discloses a navigation device provided with a charging facility consideration key that narrows down searched out facilities to facilities provided with battery charging facilities. 
     Patent Document 5 discloses a vehicle navigation device which specifies charging stations having charging units which can charge a battery, informs an occupant of the charging stations, sets a charging station specified by the occupant as a destination, and searches out and displays a route to the charging station of destination. 
     Patent Document 6 discloses a navigation device that performs guidance to a charging facility in the vicinity of a specified destination or a specified transit point instead of guidance to the destination or the transit point. 
     PRIOR ART DOCUMENTS 
     Patent Documents 
     
         
         Patent Document 1: Japanese Patent Application Laid-Open No. 09-210702 (1997) 
         Patent Document 2: Japanese Patent Application Laid-Open No. 2003-262525 
         Patent Document 3: Japanese Patent Application Laid-Open No. 2011-164050 
         Patent Document 4: Japanese Patent Application Laid-Open No. 2010-286449 
         Patent Document 5: Japanese Patent Application Laid-Open No. 2011-203174 
         Patent Document 6: Japanese Patent Application Laid-Open No. 2011-237186 
       
    
     SUMMARY OF INVENTION 
     Problems to be Solved by the Invention 
     The above-described techniques disclosed in Patent Documents 1 to 6 have the following problems. The navigation system disclosed in Patent Document 1 merely identifies a position of a service station corresponding to a charging station for identification, and does not search for a route. Therefore, the navigation system cannot inform the user of a route to the charging station. 
     The charging station information providing apparatus disclosed in Patent Document 2 merely provides the position of the extracted charging station and the availability information of chargers installed in the charging station, and does not search for a route. Therefore, the charging station information providing apparatus cannot inform the user of a route to the charging station. 
     The in-vehicle navigation device disclosed in Patent Document 3 is configured to display information about a position and availability of a charging unit, so that it can inform the user of information as to whether or not the battery can be charged. However, the technique disclosed in Patent Document 3 is a technique of displaying the charging station status icon, and is not a technique of route search. Even with the technique disclosed in Patent Document 3, it is impossible to inform the user of information as to which route is the best route from the current position of the vehicle to a charging station where the battery can be charged. 
     As described above, the techniques disclosed in Patent Documents 1 to 3 cannot inform the user of a route to the charging station. Therefore, there may be disadvantages to the user such that the user cannot arrive at a desired charging station in the shortest time. 
     The navigation device disclosed in Patent Document 4 requires the user to instruct the navigation device to search for charging facilities for the purpose of narrowing the facilities down to a facility equipped with battery charging facilities, and to set the searched out charging facility as the destination. Therefore, operation is complicated. 
     The vehicle navigation device disclosed in Patent Document 5 requires the user to specify a charging station as the destination from among the informed charging stations. Therefore, operation is complicated. 
     The navigation device disclosed in Patent Document 6 does not search for a route to a charging facility corresponding to a charging station unless the user specifies a destination or a transit point, and therefore, operation is complicated. Moreover, unless the user sets the destination or the transit point again after being guided to the charging station, guidance to a destination or a transit point will not be performed. 
     The techniques disclosed in Patent Documents 1 to 6 do not take into account the remaining battery capacity required when traveling to a charging station after arrival at the destination. Therefore, the vehicle may be incapable of traveling after arrival at the destination. 
     An object of the present invention is to provide a navigation device and a navigation method with which a site where an electric vehicle can be charged after arrival at the destination can be previously recognized before arriving at a destination. 
     Means for Solving the Problems 
     A navigation device according to the present invention is a navigation device used in an electric vehicle, the device including: a Central Processing Unit; a memory having stored therein instructions which, when executed by the Central Processing Unit, cause the Central Processing Unit to carry out steps of: acquiring a current position; receiving, as an input, a destination; and searching for a route from the acquired current position, via the destination inputted, to a post-arrival chargeable site where a battery of the electric vehicle is capable of being charged after arrival at the destination. 
     A navigation method according to the present invention includes: acquiring a current position of an electric vehicle; and searching for a route from the acquired current position, via a destination, to a post-arrival chargeable site where a battery of the electric vehicle is capable of being charged after arrival at the destination. 
     Effects of the Invention 
     With the navigation device according to the present invention, the navigation device is used in an electric vehicle, and the device includes: a Central Processing Unit; a memory having stored therein instructions which, when executed by the Central Processing Unit, cause the Central Processing Unit carry out steps of: acquiring a current position; receiving, as an input, a destination; and searching for a route from the acquired current position, via the destination inputted, to a post-arrival chargeable site. As a result, post-arrival chargeable site can be previously recognized before arriving at the destination. Therefore, measures can be previously taken, for example, to prevent the electric vehicle from being incapable of traveling after arrival at the destination. 
     The navigation method according to the present invention acquires a current position of an electric vehicle, and searches for a route from the acquired current position, via a destination, to a post-arrival chargeable site. As a result, the post-arrival chargeable site can be previously recognized before arriving at the destination. Therefore, measures can be previously taken, for example, to prevent the electric vehicle from being incapable of traveling after arrival at the destination. 
     The object, features, aspects, and advantages of the present invention will become more apparent from the following detailed description and the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a block diagram illustrating a configuration of a navigation device  100  according to a first embodiment of the present invention. 
         FIG. 2  is a diagram illustrating a current position screen  200 . 
         FIG. 3  is a diagram illustrating a menu screen  210 . 
         FIG. 4  is a diagram illustrating a facility type screen  220 . 
         FIG. 5  is a diagram illustrating a facility list screen  230 . 
         FIG. 6  is a diagram illustrating a facility surroundings screen  240 . 
         FIG. 7  is a diagram illustrating a whole route screen  250 . 
         FIG. 8  is a flowchart showing a route guidance procedure in an underlying technology of the present invention. 
         FIG. 9  is a flowchart showing the route guidance procedure in the underlying technology of the present invention. 
         FIG. 10  is a diagram illustrating a whole route screen  300 . 
         FIG. 11  is a diagram illustrating a whole route screen  310 . 
         FIG. 12  is a flowchart showing a route guidance procedure in the first embodiment of the present invention. 
         FIG. 13  is a flowchart showing the route guidance procedure in the first embodiment of the present invention. 
         FIG. 14  is a flowchart showing the route guidance procedure in the first embodiment of the present invention. 
         FIG. 15  is a flowchart showing the route guidance procedure in the first embodiment of the present invention. 
         FIG. 16  is a flowchart showing the route guidance procedure in the first embodiment of the present invention. 
         FIG. 17  is a flowchart showing the route guidance procedure in the first embodiment of the present invention. 
         FIG. 18  is a flowchart showing a route guidance procedure in a second embodiment of the present invention. 
         FIG. 19  is a flowchart showing the route guidance procedure in the second embodiment of the present invention. 
         FIG. 20  is a flowchart showing the route guidance procedure in the second embodiment of the present invention. 
         FIG. 21  is a flowchart showing the route guidance procedure in the second embodiment of the present invention. 
         FIG. 22  is a flowchart showing the route guidance procedure in the second embodiment of the present invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     First Embodiment 
       FIG. 1  is a block diagram illustrating a configuration of a navigation device  100  according to the first embodiment of the present invention. The navigation device  100  is used in a vehicle, and is used as an in-vehicle navigation device. In this embodiment, the navigation device  100  is an in-vehicle navigation composite device which has a navigation function of performing route guidance and an Audio Visual (abbreviated as: AV) function of performing reproduction or the like of audio and video. 
     Specifically, the navigation device  100  is used in an electric vehicle (EV). Here, the “electric vehicle” may be a vehicle which is solely powered by electric energy or a hybrid vehicle which is powered by electric energy and another type of energy. For example, the electric vehicle may be a plug-in hybrid vehicle which can be charged by supplying electric power from an external electric power source such as a home wall socket. Hereinafter, a vehicle equipped with the navigation device  100  will be referred to as “own vehicle”. 
     The navigation device  100  includes a navigation device body  1 , a Global Positioning System (abbreviated as GPS) receiver  3 , a self-contained navigation sensor  4 , a traffic information transceiver  6 , a display  16 , and a speaker  18 . The display  16  and the speaker  18  carry out the step of outputting the searched out route. 
     The navigation device body  1  includes a control unit  2 , a current position detector  5 , an information storage  7 , an information update unit  8 , an information input unit  9 , an instruction input unit  10 , a facility search unit  11 , a route calculator  12 , a guidance unit  13 , an information rendering unit  14 , a display controller  15 , an audio controller  17 , and an EV information input unit  19 . 
     The control unit  2  carries out the step of judging whether traveling from the current position via the destination to the post-arrival chargeable site, based on the battery charging information. The current position detector  5  carries out the step of acquiring a current position. The instruction input unit  10  carries out the step of receiving, as an input, a destination. The route calculator  12  carries out the step of searching for a route from the acquired current position, via the destination inputted, to a post-arrival chargeable site where a battery of the EV is capable of being charged after arrival at the destination. The guidance unit  13  carries out the step of guiding the route searched out by the route calculator  12 . The EV information input unit  19  carries out the step of acquiring a battery charging information about charged amount of the battery of the EV. 
     The control unit  2  is implemented by a Central Processing Unit (abbreviated as CPU). The control unit  2  has a built-in memory (not shown). According to a control program stored in the memory, the control unit  2  integrally controls the current position detector  5 , the information storage  7 , the information update unit  8 , the facility search unit  11 , the route calculator  12 , the guidance unit  13 , the information rendering unit  14 , the display controller  15 , and the audio controller  17 , which are included in the navigation device body  1 . 
     The GPS receiver  3  receives radio signals transmitted from GPS satellites. The GPS receiver  3  provides the received radio signals to the current position detector  5 . The radio signals provided to the current position detector  5  are used when a satellite navigation system is applied to measurement of the current position of the own vehicle. 
     The self-contained navigation sensor  4  includes a direction sensor that detects a direction of the own vehicle and a traveled distance sensor that detects a traveled distance by detecting the number of revolutions of the wheels of the own vehicle. The self-contained navigation sensor  4  provides information indicating the direction detected by the direction sensor (hereinafter, referred to as “direction information”) and information indicating the traveled distance detected by the traveled distance sensor (hereinafter, referred to as “traveled distance information”) for the current position detector  5 . The direction information and the traveled distance information provided to the current position detector  5  are used when a self-contained navigation system is applied to detection of the current position and the direction of the own vehicle. 
     Based on the radio signals provided from the GPS receiver  3  and the direction information and the traveled distance information provided from the self-contained navigation sensor  4 , the current position detector  5  detects the current position and the direction of travel of the own vehicle by using the satellite navigation system in combination with the self-contained navigation system, and carrying out map matching based on map information. 
     Here, “map matching” is one method of estimating the most probable position of the own vehicle as the current position of the own vehicle by taking into account road information included in the map information, a travel path of the own vehicle including right turn and left turn, and the like, and comparing these with the detected current position of the own vehicle. In this embodiment, although a case will be described where a hybrid method of using the satellite navigation system in combination with the self-contained navigation system is adopted, a case where only one of the navigation systems is adopted is also possible. 
     The traffic information transceiver  6  transmits and receives traffic information to and from the control unit  2 . Specifically, the traffic information transceiver  6  receives or transmits the traffic information successively or at predetermined timing. The traffic information transceiver  6  receives traffic information provided from, for example, Vehicle Information and Communication System (abbreviated as VICS (registered trademark)) by FM multiplex broadcasting, radio wave beacon, or light beacon. The traffic information includes information of congestion state, congestion distance, traffic regulation, and the time required for travel for each road. 
     The traffic information transceiver  6  is capable of performing communication by using DSRC (Dedicated Short Range Communication). DSRC is a short-range radio technology using radio wave of 5.8 GHz band. Various services can be provided for the user by using DSRC in bi-directional communication or one-way communication between a road side device and an in-vehicle device, i.e., the navigation device  100 . 
     Cases where the traffic information transceiver  6  functions as a transmitter for transmitting the traffic information include a case where the traffic information transceiver  6  transmits information about the own vehicle, for example, the current position, the traveling speed, and other information called probe information. In the case where the traffic information is not bi-directionally exchanged, the traffic information transceiver  6  may be replaced with a traffic information receiver. 
     The information storage  7  is implemented by a Hard Disk Drive (abbreviated as HDD) device. The information storage  7  stores information required for various functions including the navigation function and an entertainment function. 
     The information storage  7  previously includes a map information storage  71  and an AV information storage  72 . The map information storage  71  stores map information representing a map. The AV information storage  72  stores AV information, specifically, information of audio or video, or both of audio and video. The navigation device  100  according to this embodiment is a standalone navigation device which operates based on the map information stored in the map information storage  71 . 
     The map information storage  71  has a plurality of hierarchically organized maps corresponding to predetermined scales as the map information. The map information includes map display information. The map display information includes at least one of “road information” about roads, “facility information” representing types, names, and positions of facilities, “types of character information” representing the names of places, the names of facilities, the names of intersections, and the names of roads, and “types of icon information” representing facilities, route numbers, and the like. The map display information is displayed on the display  16 . 
     The map information storage  71  also stores other information such as guidance information to be used by the guidance unit  13  and information not displayed on the display  16 . The guidance information includes position information of a predetermined key point, and rendering information and audio guidance information of the predetermined key point. The information not displayed on the display  16  includes, for example, information representing a road with line segments called links and points called nodes, and information about a link cost as a load required to travel the link. The information not displayed on the display  16  is not limited thereto, and may include other various kinds of information. 
     The map information and the AV information stored in the information storage  7  can be changed, and can be partly updated, partly added, partly deleted, completely deleted, or completely updated by the information update unit  8  based on an instruction from the control unit  2 . 
     The information update unit  8  updates information including the map information and the AV information stored in the information storage  7  based on an instruction from the control unit  2 . 
     Information such as the map information and the AV information is input into the information input unit  9  from outside of the navigation device  100 . The information provided to the information input unit  9  from outside of the navigation device  100  is used when the information stored in the information storage  7  is updated. 
     The information input unit  9  has an insertion unit  91  to which and from which a medium can be inserted and removed. The medium stores information such as the map information and the AV information. The medium includes, for example, a disk medium such as a CD-ROM (Compact Disc Read Only Memory) and a DVD-ROM (Digital Versatile Disk Read Only Memory) and a semiconductor medium such as an SD (Secure Digital) card. The control unit  2  reads out the above-described information of the map information or the AV information from the medium inserted in the insertion unit  91 . The information such as the map information or the AV information read out from the medium that is inserted in the insertion unit  91  is stored in the information storage  7 . 
     The instruction input unit  10  includes, for example, a hardware operation switch operated by a user, a touch switch set and displayed on the display  16  described below, a remote controller mounted to a steering wheel of the own vehicle or the like, and a voice recognition device having a voice recognition function of recognizing a user&#39;s voice instruction. 
     The instruction input unit  10  is used by the user in inputting information such as numerical information, character information, and instruction information for the navigation device body  1 . When the instruction input unit  10  is operated by the user, the instruction input unit  10  generates an instruction signal indicating an instruction corresponding to the operation made by the user, and provides the instruction signal to at least any one of the facility search unit  11 , the route calculator  12 , the guidance unit  13 , and the information rendering unit  14 . 
     The facility search unit  11 , the route calculator  12 , the guidance unit  13 , and the information rendering unit  14  provide the control unit  2  with the instruction signal provided from the instruction input unit  10 . Therefore, the user of the navigation device  100  can operate the instruction input unit  10  to provide an instruction corresponding to the operation to the facility search unit  11 , the route calculator  12 , the guidance unit  13 , the information rendering unit  14 , and the control unit  2 . 
     The facility search unit  11  searches facility information stored in the map information storage  71  for a desired facility. Specifically, the facility search unit  11  searches the map information stored in the map information storage  71  for a facility, a place, and the like desired by the user based on the user&#39;s instruction provided from the instruction input unit  10 . The result searched out by the facility search unit  11  is provided to the display  16  via the control unit  2  and the display controller  15 , and is displayed on the display  16 . 
     The route calculator  12  calculates a route preferable to take the user to the desired site. Specifically, the route calculator  12  calculates the best route from the current position of the own vehicle to a site such as a destination and a transit point set by the user (hereinafter, referred to as “recommended route”) based on the instruction signal provided from the instruction input unit  10 . The recommended route means, for example, a route which is the shortest (hereinafter, referred to as “shortest route”), a route which takes the shortest time (hereinafter, referred to as “fastest route”), a route with lowest cost including a toll for a toll road (hereinafter, referred to as “low-cost route”), a route which consumes the lowest power (hereinafter, referred to as “low-power consumption route”), or a route with a favorable balance between time and cost (hereinafter, referred to as “standard route”). The recommended route may be optionally arranged from the above-described routes. 
     The route calculator  12  acquires the current position of the own vehicle from the current position detector  5  via the control unit  2 . Further, the route calculator  12  calculates the recommended route based on site information input from the instruction input unit  10  and the map information acquired from the map information storage  71 . The recommended route calculated by the route calculator  12  is provided to the display  16  via the control unit  2  and the display controller  15 , and is displayed on the display  16 . 
     When the route calculation is performed by the route calculator  12 , for example, the publicly known Dijkstra&#39;s Algorithm or the like is used which accumulates link costs allocated to the links which represent respective roads by line segments and figures out a route requiring the minimum link cost. 
     The guidance unit  13  assists the user in driving at a predetermined key point by providing the guidance information to the control unit  2  based on the instruction signal provided from the instruction input unit  10 . For example, while traveling the recommended route, the guidance unit  13  provides the guidance information indicating a site such as an intersection or crossroads at which the direction has to be changed, or a site which is likely to be mistaken. Further, when traveling a multi-lane road, the guidance unit  13  takes account of right turn or left turn ahead, and provides the guidance information indicating a site to guide the user to previously change the lane to a predetermined lane. 
     The guidance unit  13  acquires the current position of the own vehicle from the current position detector  5  via the control unit  2 . Also, the guidance unit  13  acquires the recommended route from the route calculator  12  via the control unit  2 . Further, the guidance unit  13  acquires the guidance information included in the map information from the map information storage  71  via the control unit  2 . 
     When the own vehicle has arrived at a predetermined key point such as an intersection, the guidance unit  13  instructs the display controller  15  via the control unit  2  to visually present, for example, a direction to take at the intersection by means of an arrow or color painting of the road, and to output to the display  16  an enlarged guide map which is enlarged or enlarged and transformed. Alternatively, the guidance unit  13  instructs the display controller  15  via the control unit  2  to visually present a direction to take, and to output the actual image of the key point or an image similar to that to the display  16 . 
     The information rendering unit  14  performs information processing for rendering, on the display  16 , various types of information desired by the user such as the map information and the guidance information. Further, the information rendering unit  14  performs information processing for rendering, on the display  16 , a setting of respective functions of the navigation device  100  as a menu screen. 
     The information rendering unit  14  has a map rendering unit  141  and a menu rendering unit  142 . The map rendering unit  141  performs information processing for rendering a desired map on the display  16  by processing the map information stored in the map information storage  71  based on the instruction signal provided from the instruction input unit  10 . The menu rendering unit  142  manages the state of the menu screen and performs information processing for rendering the menu screen on the display  16  based on the instruction signal provided from the instruction input unit  10 . 
     The map rendering unit  141  acquires necessary information from the map information storage  71 , the current position detector  5 , the facility search unit  11 , the route calculator  12 , the guidance unit  13 , and the menu rendering unit  142 , and processes information to be displayed on the display  16  based on the instruction provided from the instruction input unit  10 . The map rendering unit  141  provides the rendering information about the map to be rendered on the display  16  for the display controller  15  via the control unit  2 . 
     The menu rendering unit  142  provides the rendering information about the menu screen to be rendered on the display  16  to the display controller  15  via the control unit  2  based on the instruction provided from the instruction input unit  10 . A rendering of the menu screen includes a setting of a touch switch which is set on a display screen of the display  16 . When the user operates the touch switch, the operation is recognized by the instruction input unit  10 . 
     The display controller  15  converts the rendering information provided from the information rendering unit  14  via the control unit  2  into video signals available for the display  16 , and instructs the display  16  to display an image represented by the rendering information according to a control command provided from the control unit  2 . Further, the display controller  15  can instruct to render image information stored in the AV information storage  72  on the display  16 . 
     The display  16  is implemented by a liquid crystal display, for example. The display  16  displays the image represented by the rendering information on the display screen based on the instruction provided from the display controller  15 . 
     In response to input of information about audio such as the AV information (hereinafter, referred to as “audio data”), the audio controller  17  causes the audio to be output from the speaker  18  connected to the navigation device body  1 . Specifically, the audio controller  17  converts the audio data provided from the control unit  2  into audio signals available for the speaker  18 , and provides the audio signals to the speaker  18  based on a control command provided from the control unit  2 . As a result, the audio is output from the speaker  18 . 
     When the audio controller  17  receives input of the guidance information from the guidance unit  13  via the control unit  2 , the audio controller  17  becomes able to instruct the speaker  18  to output the input guidance information as audio. Specifically, in response to input of the audio data as the guidance information, the audio controller  17  converts the input audio data into the audio signals available for the speaker  18 , and provides the audio signals to the speaker  18 . As a result, the guidance information is output from the speaker  18  as audio. 
     The speaker  18  outputs the audio represented by the audio signals provided from the audio controller  17 . A plurality of speakers  18  are provided. In the case where the input audio data is the guidance information, the audio controller  17  controls the speakers  18  to output the guidance information from the speaker near to the driver&#39;s seat among the plurality of speakers  18 . 
     The plurality of speakers  18  may have the same structure or different structures. For example, the plurality of speakers with different structures may have different roles such as a structure of primarily outputting a high-pitched tone, a structure of primarily outputting a medium-pitched tone, and a structure of primarily outputting a low-pitched tone may take respective roles. The speaker  18  to be used for outputting the guidance information may desirably have the structure of primarily outputting a medium-pitched tone in consideration of audibleness. 
     The audio controller  17  distributes the audio information acquired from the AV information storage  72  or the information input unit  9  among the respective speakers  18  in suitable allotments, and instructs the respective speakers  18  to output the audio information. In the case where the information acquired from the AV information storage  72  or the information input unit  9  includes both the audio information and the video information of television broadcasting, a DVD, or the like, the audio controller  17  provides the acquired audio information to the speaker  18  and instructs the speaker  18  to output the audio information, and the display controller  15  provides the acquired video information to the display  16  and instructs the display  16  to output the video information. In this manner, the audio controller  17  and the display controller  15  operate in conjunction with each other to implement the entertainment function. 
     The EV information input unit  19  supplies, to the navigation device  100 , information about the EV such as EV traveling information and battery charging information (hereinafter, referred to as “EV information”). By receiving the EV information of EV vehicle information from outside, the EV information input unit  19  can update the control unit  2  with the EV information. Further, by receiving information from outside, the EV information input unit  19  itself can also function as the information storage  7 . Herein, the information received by the EV information input unit  19  from outside is specifically EV model information and battery charging state information. 
       FIGS. 2 to 7  are diagrams illustrating display screens  161  on the display  16  of the navigation device  100  in route guidance processing in an underlying technology as a premise of the present invention. In response to the user&#39;s input of an instruction to change the display of the display screen  161  (hereinafter, referred to as “change instruction”) from the instruction input unit  10 , the information rendering unit  14  performs processing according to the input change instruction, and the instruction signal is provided to the display  16  via the control unit  2  and the display controller  15 . In this embodiment, inputting of an instruction to the instruction input unit  10  is exemplified by user operation on the touch switches on the display screen  161 . 
       FIG. 2  is a diagram illustrating a current position screen  200 . In response to selection of displaying a map covering the current position of the own vehicle and its surroundings as an object of displaying the map, the current position screen  200  illustrated in  FIG. 2  is displayed. In the current position screen  200 , a map covering a range of about one kilometer square from the own vehicle is displayed, for example. 
     The current position of the own vehicle to be displayed in the current position screen  200  is detected by the current position detector  5  based on the information provided from the GPS receiver  3 , the self-contained navigation sensor  4 , and the like. In the current position screen  200 , the current position of the own vehicle is indicated by a current position symbol  201 . It is considered that a map covering the current position of the own vehicle and its surroundings to be displayed in the current position screen  200  will be most frequently displayed during the use of the navigation device  100 . In  FIG. 2 , a menu button  202  at the lower right of the current position screen  200  is a touch switch which has been set in the display screen  161  of the display  16 . In response to user&#39;s pressing on the menu button  202 , the current position screen  200  displaying the map covering the current position and the area around the current position illustrated in  FIG. 2  transitions to a menu screen  210  for selecting a function illustrated in  FIG. 3 . 
       FIG. 3  is a diagram illustrating the menu screen  210 . In the menu screen  210 , “input destination setting” is displayed in a title bar  211 . In the example illustrated in  FIG. 3 , the menu screen  210  includes three selection buttons  212 ,  213 , and  215  as touch switches for performing three functions of “facility search”, “surrounding facility search”, and “address search”. In response to pressing on the selection button  212  described as “facility” (hereinafter, referred to as “‘facility search’ button”), “facility search” is performed. In response to pressing on the selection button  215  described as “surroundings of own vehicle”, “surrounding facility search” is performed. In response to pressing on the selection button  213  described as “address”, “address search” is performed. 
     Further, the menu screen  210  includes the selection button  214  described as “registered place” as a touch switch for performing a function of “registered place search” which searches for a destination from among previously registered places and sets the place as the destination. Further, the menu screen  210  includes the selection button  216  described as “advance” as a touch switch for performing a function other than “facility search”, “surrounding facility search”, “address search”, and “registered place search”. 
     Further, the menu screen  210  includes a back button  217  described as “back” as a touch switch for moving back to the current position screen  200  illustrated in  FIG. 2 . The menu screen  210  is not limited to the example illustrated in  FIG. 3 , and may include other touch switches such as selection buttons for displaying maps covering surroundings of the destination, surroundings of a transit point, or surroundings of the user&#39;s house. 
       FIG. 4  is a diagram illustrating a facility type screen  220 . The facility type screen  220  is a screen displaying a result of a facility search performed in response to pressing on the “facility search” button  212  in the menu screen  210  illustrated in  FIG. 3 . In the facility type screen  220 , “input facility setting” is displayed in a title bar  221 . The facility type screen  220  includes four selection buttons  222  to  225  as touch switches for displaying a list for each facility type. 
     Further, the facility type screen  220  includes a scroll bar  228 . By pressing an up button  226  or a down button  227  on the scroll bar  228 , the user can vertically move a range of selection buttons displayed in the facility type screen  220  so that other selection buttons are displayed. The up button  226  and the down button  227  are touch switches. Further, the facility type screen  220  includes a back button  229  described as “back” as a touch switch for moving back to a previous screen, i.e., the menu screen  210  illustrated in  FIG. 3 . 
     As a facility search method, for example, there is known a method of refining a search with a facility type and a geographical position as conditions, by using the facility information stored in the map information storage  71 , according to the user&#39;s instruction provided from the instruction input unit  10 . The facility search method is not limited thereto, and various methods can be used. 
     The facility search is performed by the facility search unit  11 . From among the facilities detected by the facility search, a desired facility is selected by the user and set as the destination according to the user&#39;s instruction. In this case, a recommended route from the current position of the own vehicle to the desired facility is calculated by the route calculator  12 , and guidance required at a predetermined key point in the recommended route is calculated by the guidance unit  13 . 
     Together with the current position of the own vehicle acquired by the current position detector  5 , the above-described calculation results are provided to the information rendering unit  14 , and when the own vehicle has arrived at the predetermined key point, the guidance information is displayed in or replaces the map displayed in the display screen  161  as required. Further, the navigation device  100  also performs audio guidance by part of the speakers  18  at the predetermined key point via the audio controller  17  based on the guidance information provided from the guidance unit  13 . 
       FIG. 5  is a diagram illustrating a facility list screen  230 . As an example of the facility list screen  230 ,  FIG. 5  illustrates a screen displaying a result of a search for facilities classified as “dining &amp; restaurant” in response to pressing on a selection button  222  described as “dining &amp; restaurant” in the facility type screen  220  illustrated in  FIG. 4 . In the facility list screen  230  illustrated in  FIG. 5 , “input dining &amp; restaurant” is displayed in a title bar  231 . The facility list screen  230  includes four selection buttons  232  to  235  as touch switches for setting an individual facility as the destination. 
     Further, the facility list screen  230  includes a scroll bar  238 . By pressing an up button  236  or a down button  237  on the scroll bar  238 , the user can vertically move a range of selection buttons displayed in the facility list screen  230  so that other selection buttons are displayed. The up button  236  and the down button  237  are touch switches. Further, the facility list screen  230  includes a back button  239  described as “back” as a touch switch for moving back to a previous screen, i.e., the facility type screen  220  illustrated in  FIG. 4 . 
       FIG. 6  is a diagram illustrating a facility surroundings screen  240 . As an example of the facility surroundings screen  240 ,  FIG. 6  illustrates a case where “restaurant ABC” is set as the destination in response to pressing on a selection button  232  described as “restaurant ABC” in the facility list screen  230  illustrated in  FIG. 5 . In the facility surroundings screen  240 , the name of the facility set as the destination is displayed in a title bar  241 . In the example illustrated in  FIG. 6 , “restaurant ABC” is displayed. 
     In the facility surroundings screen  240 , the facility which is set as the destination (hereinafter, referred to as “destination facility”) is represented by a house symbol denoted by the reference character “ 242 ”. In the facility surroundings screen  240 , a map covering the destination facility  242  and the surroundings thereof is displayed. The facility surroundings screen  240  includes a start search button  243  described as “start search” as a touch switch for inputting an instruction to start searching for a route from the current position of the own vehicle to the destination. Further, the facility surroundings screen  240  includes a back button  244  described as “back” as a touch switch for moving back to a previous screen, i.e., the facility list screen  230  illustrated in  FIG. 5 . 
       FIG. 7  is a diagram illustrating a whole route screen  250 . The whole route screen  250  is a screen displaying a result of a search for a route from the current position of the own vehicle to the destination in response to pressing on the start search button  243  in the facility surroundings screen  240  illustrated in  FIG. 6 . In the whole route screen  250 , the current position of the own vehicle is represented by the current position symbol  201 , and the destination is represented by a white circle denoted by the reference character “ 251 ”. Further, at the position of the destination  251 , a flag symbol is displayed as a destination symbol  252  indicating the destination  251 . 
     The whole route screen  250  displays the current position symbol  201  of the own vehicle and the destination  251 , a map covering the surroundings thereof, and a route from the current position symbol  201  of the own vehicle to the destination  251 . The route is shown by a thick line. Further, the whole route screen  250  includes a current position button  253  described as “current position” as a touch switch for displaying the current position screen  200  illustrated in  FIG. 2 . Also, the whole route screen  250  includes a start guidance button  254  described as “start guidance” as a touch switch for inputting an instruction to start guidance to the destination  251 . 
       FIGS. 8 and 9  are flowcharts showing a route guidance procedure of the underlying technology as a premise of the present invention. Each process of the flowcharts shown in  FIGS. 8 and 9  is performed by the control unit  2 . Processing in the flowcharts shown in  FIGS. 8 and 9  is started in response to power-on of the navigation device  100 , and the operation proceeds to step ST 1 . 
     In step ST 1 , the control unit  2  causes a map covering the current position to be displayed on the display  16 . For example, the control unit  2  causes the above-described current position screen  200  illustrated in  FIG. 2  to be displayed in the display screen  161  on the display  16  as the map covering the current position. 
     Specifically, firstly, current position data representing the current position of the own vehicle and map data are acquired. That is, the current position detector  5  acquires the current position data from the GPS receiver  3  and the self-contained navigation sensor  4 , and provides the detected current position of the own vehicle to the control unit  2 . Meanwhile, the information input unit  9  reads out the map data from an HDD constituting the information input unit  9  or a medium such as a DVD inserted in the insertion unit  91  of the information input unit  9 . The information input unit  9  stores the read out map data in the map information storage  71  via the control unit  2 . 
     The control unit  2  reads out the map data from the map information storage  71 , and performs matching processing for superimposing the current position symbol  201  representing the position of the own vehicle (hereinafter, referred to as “own vehicle position”) on a position corresponding to the current position data provided from the current position detector  5 . The map data which has been subjected to the matching processing is provided to the display controller  15  via the control unit  2 . 
     The display controller  15  generates rendering data based on the map data subjected to the matching processing by the control unit  2 , and provides the rendering data to the display  16 . Consequently, as illustrated in  FIG. 2  described above, the map covering the area around the current position of the own vehicle is displayed on the display  16 . When the map covering the current position is displayed, the operation proceeds to step ST 2 . 
     In step ST 2 , the control unit  2  judges whether or not the destination is set. In step ST 2 , if it is judged that the destination is set, the operation proceeds to step ST 3 , and if it is judged that the destination is not set, the control unit  2  waits until the destination is set. 
     The user inputs the destination such as a site and a facility included in the map data from the instruction input unit  10  by operating, for example, a touch switch as destination input means displayed on the display  16 , an input button provided to the body, or the like. For example, the user inputs the destination by pressing the above-described touch switches displayed in the display screens  161  illustrated in  FIGS. 3 to 5 . 
     If it is judged that the destination is set in step ST 2 , the facility search unit  11  provides the control unit  2  with destination input data of a site, a facility, and the like based on the information input from the instruction input unit  10 . The control unit  2  provides the route calculator  12  and the guidance unit  13  with the result of the matching processing performed on the map and the current position of the own vehicle as well as the destination input data provided from the facility search unit  11 . 
     Next, in step ST 3 , the control unit  2  judges whether or not pressing on the start search button  243  is detected in the above-described facility surroundings screen  240  illustrated in  FIG. 6 . In step ST 3 , if it is judged that the pressing is detected, the operation proceeds to step ST 4 , and if it is judged that the pressing is not detected, the control unit  2  waits until the pressing is detected. 
     In step ST 4 , the control unit  2  starts a route search. Specifically, the route calculator  12  creates a route by performing processes for searching for a route from the current position of the own vehicle to the destination. When the route has been created in this manner, the operation proceeds to step ST 5 . 
     In step ST 5 , the control unit  2  judges whether or not the own vehicle can travel to the destination. In step ST 5 , if it is judged that the own vehicle can travel to the destination, the operation proceeds to step ST 8 , and if it is judged that the own vehicle cannot travel to the destination, the operation proceeds to step ST 6 . 
     In step ST 6 , the control unit  2  adds, to the route to the destination, a pre-arrival chargeable site which is a battery chargeable site available for battery charging before arriving at the destination, and the operation proceeds to step ST 7 . 
     In step ST 7 , the control unit  2  starts searching again for a route to the destination to include the pre-arrival chargeable site added in step ST 6 . Specifically, the route calculator  12  creates a route by again performing processes for searching for a route from the current position of the own vehicle to the destination. When the route has been created in this manner, the operation proceeds to step ST 8 . 
     In step ST 8 , the control unit  2  displays the route to the destination. Specifically, the control unit  2  instructs the guidance unit  13  to perform route guidance processing from the own vehicle position to the destination. The guidance unit  13  creates route guidance information by performing the guidance processing from the own vehicle position to the destination based on the instruction from the control unit  2 . The control unit  2  provides the display controller  15  with the guidance information including the route to the destination provided from the route calculator  12  and an intersection guide map to the destination and the like provided from the guidance unit  13 . The display controller  15  performs display processing on the provided route and guidance information for displaying on the display  16 , and provides the information to the display  16 . As a result, the route and the guidance information are displayed on the display  16 . 
     In step ST 9 , the control unit  2  judges whether or not pressing on the start guidance button for instructing to start route guidance to the destination is detected. In step ST 9 , if it is judged that the pressing is detected, the operation proceeds to step ST 10 , and if it is judged that the pressing is not detected, the control unit  2  waits until the pressing is detected. 
     In step ST 10 , the control unit  2  starts route guidance to the destination. Specifically, the control unit  2  provides the audio controller  17  with guidance audio information out of the guidance information to the destination provided from the guidance unit  13 . The audio controller  17  performs audio processing on the provided guidance audio information for outputting from the speaker  18 , and provides the guidance audio information to the speaker  18 . As a result, the audio represented by the guidance audio information is output from the speaker  18 . In this manner, the user is guided through the route by audio output from the speaker  18 . 
     Thereafter, the control unit  2  sequentially provides the audio controller  17  with the guidance audio information representing guide messages corresponding to the environment which changes as the vehicle travels, and causes the speaker  18  to output the guide messages. As a result, the guide messages corresponding to the environment which changes as the vehicle travels are sequentially output from the speaker  18 . When the route guidance has been started in this manner, the operation proceeds to step ST 11 . 
     In step ST 11 , the control unit  2  judges whether or not the own vehicle has arrived at the destination. In step ST  11 , if it is judged that the own vehicle has arrived at the destination, the operation proceeds to step ST 12 , and if it is judged that the own vehicle has not arrived at the destination, the control unit  2  waits until it is judged that the own vehicle has arrived at the destination. In step ST 12 , the control unit  2  finishes the route guidance, returns to step ST 1 , and repeats the above processes. 
     As described above, in the underlying technology, if it is judged that the own vehicle cannot travel to the destination, the pre-arrival chargeable site is added to the route to the destination and the user is informed of this, but the underlying technology does not take into account the remaining battery capacity after arrival at the destination. Therefore, the own vehicle may be incapable of traveling after arrival at the destination. Thus, this embodiment adopts the following configuration. 
       FIGS. 10 and 11  are diagrams illustrating examples of image displayed in the display screen  161  on the display  16  of the navigation device  100  in the first embodiment of the present invention.  FIG. 10  is a diagram illustrating a whole route screen  300 . In this embodiment, in the case where the start search button  243  is pressed in the above-described facility surroundings screen  240  illustrated in  FIG. 6 , the whole route screen  300  illustrated in  FIG. 10  is displayed. In the whole route screen  300 , a post-arrival chargeable site  301  is displayed in addition to the current position symbol  201 , the destination  251 , and the destination symbol  252 . The post-arrival chargeable site  301  is a battery chargeable site after arrival at the destination. In the whole route screen  300 , a route from the destination  251  to the post-arrival chargeable site  301  is shown by a dotted line. 
     Also, in addition to the current position button  253 , the whole route screen  300  includes a start route-search for destination button  302  for instructing to start searching for a route to the destination  251  and a start route-search for charge site button  303  for instructing to start searching for a route to the post-arrival chargeable site  301 . 
       FIG. 11  is a diagram illustrating a whole route screen  310 .  FIG. 11  illustrates the whole route screen  310  displayed in the case where the start route-search for charge site button  303  is pressed in the whole route screen  300  illustrated in  FIG. 10 . The whole route screen  310  includes a start guidance button  311  for instructing to start route guidance to the post-arrival chargeable site  301 . 
       FIGS. 12 to 17  are flowcharts showing a route guidance procedure in the first embodiment of the present invention. Each process of the flowcharts shown in  FIGS. 12 to 17  is performed by the control unit  2 . Processing in the flowcharts shown in  FIGS. 12 to 17  is started in response to power-on of the navigation device  100 , and the operation proceeds to step ST 21 . 
     The processes of step ST 21  to step ST 23  are performed in the same manner as the above processes of step ST 1  to step ST 3  shown in  FIG. 8 . That is, in step ST 21 , a map covering the current position including the own vehicle is displayed on the display  16 . 
     In step ST 22 , it is judged whether or not the destination is set. If it is judged that the destination is set, the operation proceeds to step ST 23 , and if it is judged that the destination is not set, the control unit  2  waits until it is judged that the destination is set. 
     In step ST 23 , it is judged whether or not pressing on a start route-search for destination button  302  is detected. If it is judged that the pressing is detected, the operation proceeds to step ST 24 , and if it is judged that the pressing is not detected, the control unit  2  waits until it is judged that the pressing is detected. 
     In this embodiment, in step ST 24 , the control unit  2  adds the post-arrival chargeable site after the user-set destination. As the post-arrival chargeable site, a site having the battery charging facility closest to the destination or a battery chargeable site which has been previously input and stored by the user, for example, is added. When the post-arrival chargeable site is added as described above, the operation proceeds to step ST 25 . 
     In step ST 25 , the control unit  2  acquires, as the battery charging information, the EV information such as the remaining battery capacity from information about the own vehicle provided from outside of the navigation device  100  (hereinafter, referred to as “outside vehicle information”). 
     Next, in step ST 26 , searching for a route to the post-arrival chargeable site added in step ST 25  is started. When the route search has been started as described above, the operation proceeds to step ST 27 . 
     In step ST 27 , it is judged whether or not traveling to the post-arrival chargeable site is possible by taking into account the EV information such as the remaining battery capacity from the outside vehicle information. In step ST 27 , if it is judged that the own vehicle can travel to the post-arrival chargeable site, the operation proceeds to step ST 30 , and if it is judged that the own vehicle cannot travel to the post-arrival chargeable site, the operation proceeds to step ST 28 . 
     If it is judged in step ST 27  that traveling to the post-arrival chargeable site is not possible, and the operation proceeds to step ST 28 , then in step ST 28 , the control unit  2  acquires the EV information such as a remaining battery capacity and the traveling information and, by taking these into account, adds a pre-arrival chargeable site to the route to the destination as a transit point so that the own vehicle can travel to the post-arrival chargeable site via the destination. As the pre-arrival chargeable site, a site having the battery charging facility or a battery chargeable site which has been previously input and stored by the user, for example, is selected. 
     In step ST 29 , the control unit  2  starts searching again for a route to the post-arrival chargeable site in the route which is additionally set with the pre-arrival chargeable site. Specifically, the guidance unit  13  creates the guidance information by performing the guidance processing from the current position of the own vehicle to the destination. 
     In step ST 30 , the control unit  2  displays a route to the post-arrival chargeable site via the destination on the display  16 . Specifically, the control unit  2  provides the display controller  15  with the route to the destination provided from the route calculator  12  and the guidance information such as the intersection guide map to the destination provided from guidance unit  13 . The display controller  15  performs the display processing on the provided route and guidance information for displaying on the display  16 , provides the information to the display  16 , and causes the display  16  to display the information. 
     In step ST 31 , the control unit  2  judges whether or not pressing on the start guidance button for instructing to start route guidance to the post-arrival chargeable site is detected. In step ST 31 , if it is judged that the pressing is detected, the operation proceeds to step ST 32 , and if it is judged that the pressing is not detected, the operation proceeds to step ST 33 . 
     In step ST 32 , the control unit  2  starts the route guidance to the destination. Specifically, the control unit  2  provides the audio controller  17  with the guidance audio information out of the guidance information to the destination provided from the guidance unit  13 . The audio controller  17  performs the audio processing on the provided guidance audio information for outputting from the speaker  18 , provides the information to the speaker  18 , and causes the speaker  18  to output the audio. In this manner, the user is guided through the route by audio. Thereafter, the guide messages corresponding to the environment which changes as the vehicle travels are output sequentially. When the route guidance to the destination is started in this manner, the operation proceeds to step ST 35  shown in  FIG. 14 . 
     In the case where the operation proceeds from step ST 31  to step ST 33 , the control unit  2  judges in step ST 33  whether or not pressing on the start guidance button for instructing to start route guidance to the destination is detected. In step ST 33 , if it is judged that the pressing is detected, the operation proceeds to step ST 34 , and if it is judged that the pressing is not detected, the operation returns to step ST 31 . 
     In step ST 34 , as in step ST 32 , the control unit  2  starts the route guidance to the destination. When the route guidance to the destination is started as described above, the operation proceeds to step ST 53  shown in  FIG. 17 . 
     In step ST 35  shown in  FIG. 14 , the control unit  2  judges whether or not the own vehicle is traveling the guided route. In step ST 35 , if it is judged that the own vehicle is traveling the guided route, the operation proceeds to step ST 41  shown in  FIG. 15 , and if it is judged that the own vehicle is not traveling the guided route, the operation proceeds to step ST 36 . 
     In step ST 36 , the control unit  2  acquires the battery charging information, and the operation proceeds to step ST 37 . 
     In step ST 37 , the control unit  2  starts searching again for a route to the post-arrival chargeable site. When searching for a route to the post-arrival chargeable site has been started again as described above, the operation proceeds to step ST 38 . 
     In step ST 38 , the control unit  2  judges whether or not the own vehicle can travel to the post-arrival chargeable site based on the battery charging information acquired in step ST 36 . In step ST 38 , if it is judged that the own vehicle can travel to the post-arrival chargeable site, the operation returns to step ST 32  shown in  FIG. 13 , and the route guidance to the destination is started for the route searched out again in step ST 37 . In step ST 38 , if it is judged that the own vehicle cannot travel to the post-arrival chargeable site, the operation proceeds to step ST 39 . 
     In step ST 39 , as in the above-described step ST 28  shown in  FIG. 13 , the control unit  2  adds a pre-arrival chargeable site to the route to the destination, and the operation proceeds to step ST 40 . 
     In step ST 40 , as in the above-described step ST 29  shown in  FIG. 13 , the control unit  2  starts searching again for a route to the post-arrival chargeable site to include the pre-arrival chargeable site. When searching has been started again as described above, the operation returns to the above-described step ST 32  shown in  FIG. 13 , and starts the route guidance to the destination for the route searched out again in step ST 40 . 
     In step ST 41  shown in  FIG. 15 , the control unit  2  judges whether or not the own vehicle has arrived at the destination. In step ST 41 , if it is judged that the own vehicle has arrived at the destination, the operation proceeds to step ST 42 , and if it is judged that the own vehicle has not arrived at the destination, the operation returns to the above-described step ST 35  shown in  FIG. 14 , and the above processes are repeated. 
     In step ST 42 , the control unit  2  judges whether or not power off has been instructed. In step ST 42 , if it is judged that the power off has not been instructed, the operation proceeds to step ST 43 , and if it is judged that the power off has been instructed, the operation proceeds to step ST 45 . 
     In step ST 43 , the control unit  2  controls the display controller  15  to display the route from the destination to the post-arrival chargeable site on the display  16 , and the operation proceeds to step ST 44 . 
     In step ST 44 , the control unit  2  judges whether or not travel to the post-arrival chargeable site is selected. In step ST 44 , if it is judged that the travel is selected, the operation proceeds to step ST 46  shown in  FIG. 16 , and if it is judged that the travel is not selected, the operation proceeds to step ST 45 . 
     In step ST 45 , the control unit  2  finishes the guidance to the destination. When the guidance is finished as described above, the operation returns to step ST 21  shown in  FIG. 12 , and the above processes are repeated. 
     In step ST 46  shown in  FIG. 16 , the control unit  2  displays the route from the destination to the post-arrival chargeable site on the display  16 . In this manner, the control unit  2  presents the route to the post-arrival chargeable site as the next battery chargeable site to the user, letting the user judge whether or not to travel to the post-arrival chargeable site. In the case where the user has judged to travel to the post-arrival chargeable site, the user instructs to start the route guidance to the post-arrival chargeable site by, for example, pressing the start guidance button  311  in the above-described whole route screen  310  which presents the route to the post-arrival chargeable site shown in  FIG. 11 . 
     In step ST 47 , the control unit  2  judges whether or not pressing on the start guidance button for instructing to start route guidance to the post-arrival chargeable site is detected. In step ST 47 , if it is judged that the pressing is detected, the operation proceeds to step ST 48 , and if it is judged that the pressing is not detected, the control unit  2  waits until it is judged that the pressing is detected. 
     In step ST 48 , the control unit  2  starts the route guidance to the post-arrival chargeable site. 
     In step ST 49 , the control unit  2  judges whether or not the own vehicle is traveling the guided route. In step ST 49 , if it is judged that the own vehicle is traveling the guided route, the operation proceeds to step ST 51 , and if it is judged that the own vehicle is not traveling the guided route, the operation proceeds to step ST 50 . 
     In step ST 50 , the control unit  2  starts searching again for a route to the post-arrival chargeable site. When searching has been started again as described above, the operation returns to step ST 48 , and the route guidance is started for the route to the post-arrival chargeable site searched out again in step ST 50 . 
     In step ST 51 , the control unit  2  judges whether or not the own vehicle has arrived at the post-arrival chargeable site. In step ST 51 , if it is judged that the own vehicle has arrived at the post-arrival chargeable site, the operation proceeds to step ST 52 , and if it is judged that the own vehicle has not arrived at the post-arrival chargeable site, the operation returns to step ST 49 , and the above processes are repeated. 
     In step ST 52 , the control unit  2  finishes the route guidance, and returns to the above-described step ST 21  shown in  FIG. 12 , and displays the map covering the current position on the display  16 . That is, the display screen  161  on the display  16  returns to the current position screen  200 . 
     If it is judged that the pressing on the start guidance button for instructing to start route guidance to the destination is detected in the above-described step ST 33  shown in  FIG. 13 , and the operation proceeds to step ST 34  and then to step ST 53  shown in  FIG. 17 , the control unit  2  judges in step ST 53  whether or not the own vehicle is traveling the guided route. In step ST 53 , if it is judged that the own vehicle is traveling the guided route, the operation proceeds to step ST 54 , and if it is judged that the own vehicle is not traveling the guided route, the operation proceeds to step ST 56 . 
     In step ST 54 , the control unit  2  judges whether or not the own vehicle has arrived at the destination. In step ST 54 , if it is judged that the own vehicle has arrived at the destination, the operation proceeds to step ST 55 , and if it is judged that the own vehicle has not arrived at the destination, the operation returns to step ST 53  and the above processes are repeated. In step ST 55 , the control unit  2  finishes the route guidance, returns to the above-described step ST 21  shown in  FIG. 12 , and displays the map covering the current position on the display  16 . 
     In the case where the operation proceeds from step ST 53  to step ST 56 , the control unit  2  acquires the battery charging information in step ST 56 , and the operation proceeds to step ST 57 . In step ST 57 , the control unit  2  starts searching again for a route to the destination, and the operation proceeds to step ST 58 . 
     In step ST 58 , the control unit  2  judges whether or not the own vehicle can travel to the destination. In step ST 58 , if it is judged that the own vehicle can travel to the destination, the operation returns to step ST 34  shown in  FIG. 13 , and the route guidance to the destination is continued. In step ST 58 , if it is judged that the own vehicle cannot travel to the destination, the operation proceeds to step ST 59 . 
     In step ST 59 , the control unit  2  adds a pre-arrival chargeable site to the route to the destination, and the operation proceeds to step ST 60 . 
     In step ST 60 , the control unit  2  starts searching again for a route to the destination to include the pre-arrival chargeable site added in step ST 59 . When searching has been started again as described above, the operation returns to step ST 34  shown in  FIG. 13 , and the control unit  2  starts the route guidance for the route to the destination searched out again in step ST 60 . 
     As described above, according to this embodiment, the route calculator  12  searches for a route from the current position acquired by the current position detector  5 , via the destination input by the instruction input unit  10 , to the post-arrival chargeable site. As a result, the post-arrival chargeable site can be previously recognized before arriving at the destination. Therefore, measures can be previously taken, for example, to prevent the own vehicle from being incapable of traveling after arrival at the destination. 
     Further, according to this embodiment, the EV information input unit  19  acquires the battery charging information about the charged amount of the battery of the own vehicle. The control unit  2  judges whether or not traveling from the current position via the destination to the post-arrival chargeable site is possible based on the acquired battery charging information. 
     As a result, before arriving at the destination, it is possible to judge whether or not traveling from the current position via the destination to the post-arrival chargeable site is possible. Therefore, measures can be taken, for example, to ensure that the own vehicle can travel from the destination to the post-arrival chargeable site, before arriving at the destination. 
     Further, in this embodiment, if the control unit  2  has judged that traveling to the pre-arrival chargeable site is possible, the display controller  15  outputs to the display  16  the route from the current position via the destination to the post-arrival chargeable site searched out by the route calculator  12 . 
     As a result, it is possible to present to the user that traveling from the current position via the destination to the post-arrival chargeable site is possible. Further, it is possible to present the post-arrival chargeable site to the user before arriving at the destination. Therefore, the user can make the own vehicle travel without being worried that the own vehicle might be incapable of traveling. 
     Further, in this embodiment, if the control unit  2  has judged that traveling to the post-arrival chargeable site is not possible, the route calculator  12  starts searching again for a route which includes a pre-arrival chargeable site between the current position and the destination. The display controller  15  outputs the route searched out again to the display  16 . 
     As a result, before arriving at the destination, it is possible to present to the user that the own vehicle cannot travel to the post-arrival chargeable site. Further, before arriving at the destination, it is possible to present the pre-arrival chargeable site between the current position and the destination to the user. As a result, since the user is encouraged to charge up at the pre-arrival chargeable site, it is possible to prevent the own vehicle from not being able to travel to the post-arrival chargeable site. 
     Further, in this embodiment, the guidance unit  13  guides the route searched out by the route calculator  12  by using the display controller  15  and the audio controller  17 . As a result, the user can be guided through the route from the current position via the destination to the post-arrival chargeable site. Therefore, user convenience can be improved. 
     Further, in this embodiment, since the instruction input unit  10  is configured to allow input of a candidate site for the post-arrival chargeable site, candidate sites for the post-arrival chargeable site can be input by the user. As a result, a route which includes a private facility, as the post-arrival chargeable site, such as a user&#39;s house or a house of the user&#39;s friend instead of a public facility can be searched. Therefore, user convenience can be improved. 
     In this embodiment described above, in step ST 42  shown in  FIG. 15 , if it is judged that the power off has been instructed, the operation proceeds to step ST 45 , and the route guidance is finished without performing the route guidance from the destination to the post-arrival chargeable site. 
     The present invention is not limited thereto and, for example, the route guidance from the destination to the post-arrival chargeable site may be performed after the user has powered off the own vehicle and the navigation device  100  and visited the destination. In this case, after the power-off, the route to the post-arrival chargeable site is stored in a memory, for example, the information storage  7 . 
     Then, after being powered on again, in step ST 43 , the route to the post-arrival chargeable site is displayed with a message asking the user to judge whether or not to travel to the post-arrival chargeable site. Then, in step ST 44 , if it is judged that the user has selected to travel to the post-arrival chargeable site, the operation proceeds to step ST 46 , and the route guidance may be started. 
     Second Embodiment 
     A navigation device according to the second embodiment of the present invention has the same configuration as that of the navigation device  100  according to the first embodiment except for the route guidance procedure. Therefore, in the navigation device according to the second embodiment, the same reference characters are used to refer to the parts of the configuration which are the same as those of the first embodiment, and illustrations and descriptions thereof will be omitted. 
     In the above-described first embodiment, a route to the post-arrival chargeable site via the destination is displayed in step ST 30 . Then, if it is judged that the pressing on the start guidance button for instructing to start route guidance to the post-arrival chargeable site is detected in step ST 31 , the route guidance to the destination is performed in step ST 32  to step ST 40 , and after it is judged that the own vehicle has arrived at the destination in step ST 41 , the route to the post-arrival chargeable site is displayed in step ST 43 . Then, if it is judged that the user has selected to travel to the post-arrival chargeable site in step ST 44 , the route guidance to the post-arrival chargeable site is performed in step ST 46  to step ST 52 . 
     In contrast, in this embodiment, route search processing is performed as below.  FIGS. 18 to 22  are flowcharts showing a route guidance procedure according to the second embodiment of the present invention. Each process of the flowcharts shown in  FIGS. 18 to 22  is performed by the control unit  2 . In the flowcharts shown in  FIGS. 18 to 22 , the same step numbers are used to refer to the same steps as those of the flowcharts shown in  FIGS. 12 to 17 , and descriptions thereof will be omitted. Processing in the flowcharts shown in  FIGS. 18 to 22  is started in response to power-on of the navigation device  100 , and the operation proceeds to step ST 21 . 
     The processes of step ST 21  to step ST 26  are performed in the same manner as in the above-described first embodiment and the operation proceeds to step ST 27  shown in  FIG. 19 . In this embodiment, if it is judged in step ST 27  that the own vehicle can travel to the post-arrival chargeable site, the operation proceeds to step ST 71 , and if it is judged that the own vehicle cannot travel to the post-arrival chargeable site, the operation proceeds to step ST 28 . In response to completion of the processes of step ST 28  and step ST 29 , the operation proceeds to step ST 71 . 
     In step ST 71 , the control unit  2  displays the route to the destination on the display  16 . When the route to the destination has been displayed on the display  16  as described above, the operation proceeds to step ST 72 . 
     In step ST 72 , the control unit  2  judges whether or not pressing on the start guidance button for instructing to start route guidance to the destination is detected. In step ST 72 , if it is judged that the pressing is detected, the operation proceeds to step ST 32 , and if it is judged that the pressing is not detected, the control unit  2  waits until it is judged that the pressing is detected. Thereafter, the process of step ST 32  is performed in the same manner as in the first embodiment, and the operation proceeds to step ST 35  shown in  FIG. 20 . 
     In this embodiment, in step ST 35 , if it is judged that the own vehicle is traveling the guided route, the operation proceeds to step ST 73  shown in  FIG. 21 . In step ST 35 , if it is judged that the own vehicle is not traveling the guided route, the operation proceeds to step ST 36  as in the first embodiment, and after the processes of step ST 36  to step ST 40  are performed, the operation proceeds to step ST 32  shown in  FIG. 19 . 
     In step ST 73  shown in  FIG. 21 , the control unit  2  judges whether or not the own vehicle has arrived at the destination. In step ST 73 , if it is judged that the own vehicle has arrived at the destination, the operation proceeds to step ST 43 , and if it is judged that the own vehicle has not arrived at the destination, the operation returns to step ST 35  shown in  FIG. 20 , and the above processes are repeated. The processes of step ST 43  and the subsequent steps are performed in the same manner as in the above-described first embodiment. 
     As described above, in this embodiment, firstly, the route to the destination is displayed in step ST 71 , and the route guidance to the destination is performed in step ST 32  to step ST 40 . Then, after it is judged that the own vehicle has arrived at the destination in step ST 73 , the route to the post-arrival chargeable site is displayed in step ST 43 , and the route guidance to the post-arrival chargeable site is performed in step ST 46  to step ST 52 . 
     As described above, the same effect as that of the above-described first embodiment can be obtained also by performing the route guidance with the route to the destination and the route to the post-arrival chargeable site sequentially displayed. For example, also in this embodiment, since the route calculator  12  searches for a route from the current position acquired by the current position detector  5 , via the destination input by the instruction input unit  10 , to the post-arrival chargeable site, it is possible to previously recognize the post-arrival chargeable site before arriving at the destination. Therefore, measures can be previously taken, for example, to prevent the own vehicle from being incapable of traveling after arrival at the destination. 
     Also, in this embodiment, the route to the post-arrival chargeable site is not displayed on the display  16  until arrival at the destination. As a result, it is not necessary to previously select whether to perform the route guidance to the destination or to the post-arrival chargeable site beforehand. Therefore, it is possible to prevent user operations from becoming complicated while preventing the own vehicle from being incapable of traveling after arrival at the destination. 
     In the above-described first and second embodiments, the means for performing respective representative functions in the navigation device  100  are described independently of the control unit  2 . One or more types of the means for performing these respective functions such as the current position detector  5 , the information update unit  8 , the facility search unit  11 , the route calculator  12 , the guidance unit  13 , the information rendering unit  14 , the display controller  15 , and the audio controller  17  may be included in the control unit  2 . These functions may also be implemented by a microcomputer. Although the information rendering unit  14  and the display controller  15  are provided separately from each other in this embodiment, they may be integrated into one unit. 
     In this embodiment, the navigation device  100  is a standalone navigation device which operates based on the map information stored in the map information storage  71 . The navigation device  100  is not limited thereto. The navigation device  100  may be a communication type navigation device which obtains map information of a necessary area by means of communication as required and temporarily stores the map information in an internal work memory configured by a DRAM (Dynamic Random Access Memory) or the like for use. 
     In this embodiment, the information storage  7  is implemented by an HDD device. The information storage  7  is not limited thereto and may be implemented, for example, by a memory device using semiconductor elements. 
     Further, in this embodiment, the information input unit  9  is configured to store information provided from outside by means of a medium inserted in the insertion unit  91  into the information storage  7  via the control unit  2 . The information input unit  9  is not limited thereto, and may be configured to function as the information storage  7  by storing the information provided from outside into the information input unit  9 . In this case, the information storage  7  may not be provided. 
     Also, the information input unit  9  may be configured as a connection terminal such as a USB (Universal Serial Bus). In this case, the information input unit  9  as a connection terminal and a portable medium which stores information are connected to each other directly or by wire. 
     The portable medium to be connected to the information input unit  9  configured as a connection terminal may be a portable music player or an electronic device equipped with that function. Further, the portable medium may be portable information and communications equipment such as a mobile phone or a portable tablet terminal. Although the portable medium and the information input unit  9  may be connected to each other by wire, they need not to be physically connected to each other, and may be configured to wirelessly exchange information. The term “wirelessly” herein means not connected by wire in contrast to the wire connection, without regard of the exchanging scheme of the information such as whether it exchanges the information by radio wave or light. 
     Further, the information input unit  9  may be configured to include communications equipment which exchanges information with a separately installed information center. In this case, the information input unit  9  exchanges any one of the above-described map information and AV information or the other information with the information center by using the internal communications equipment. The information input unit  9  may also use the above-described portable information and communications equipment instead of including the communications equipment. 
     Further, in this embodiment, the route calculator  12  is configured to present a route as the recommended route. The route calculator  12  is not limited thereto, and may be configured to present a plurality of routes as the recommended routes. All of the plurality of routes presented in this case may not necessarily be the shortest routes, but are presented within a certain allowance. The same applies to the other optional routes which are the fastest route, the low-cost route, the low-power consumption route, and the standard route. 
     The navigation device  100  may include the speaker  18  that outputs the guidance information separately from the speakers  18  for outputting the AV information. 
     In the present invention, the above-described respective embodiments can be freely combined, or optional constituent elements of the respective embodiments can be modified or omitted as required within the scope of the present invention. 
     Although the present invention has been described in detail, the above descriptions are examples in all aspects, and the present invention is not limited thereto. It should be understood that numerous modifications which have not been exemplified herein are possible without departing from the scope of the present invention. 
     DESCRIPTION OF REFERENCE NUMERALS 
       1  navigation device body,  2  control unit,  3  GPS receiver,  4  self-contained navigation sensor,  5  current position detector,  6  traffic information transceiver,  7  information storage,  8  information update unit,  9  information input unit,  10  instruction input unit,  11  facility search unit,  12  route calculator,  13  guidance unit,  14  information rendering unit,  15  display controller,  16  display,  17  audio controller,  18  speaker,  19  EV information input unit,  100  navigation device.