Abstract:
An electric vehicle is provided with an electric energy consumption calculating unit for calculating the electric energy consumption of a battery for supplying electric energy to a motor for traveling, a virtual gasoline consumption estimating unit for estimating the virtual gasoline consumption corresponding to the electric energy consumption, an electric energy fee calculating unit for calculating the electric energy fee corresponding to the electric energy consumption, a virtual gasoline fee calculating unit for calculating the virtual gasoline fee corresponding to the virtual gasoline consumption, and a fee comparison information output means for outputting information about the comparison between the electric energy fee and the virtual gasoline fee in the form of an image or a speech.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to an electric vehicle that outputs in the form of an image or as speech information representing a comparison between an electric power charge for an actual amount of consumed electric power, and a hypothetical gasoline charge for a hypothetical amount of consumed gasoline, which is estimated based on the amount of consumed electric power. 
       BACKGROUND ART 
       [0002]    Numerous efforts have been made to develop electric vehicles as one class of environmentally friendly vehicles. Certain electric vehicles are capable of outputting information concerning the amount of reduced emission gases compared with gasoline-powered vehicles. See, Japanese Laid-Open Patent Publication No. 2001-078304 (hereinafter referred to as “JP2001-078304A”). According to JP2001-078304A, an amount of reduced carbon dioxide is calculated based on the distance that an electric vehicle has traveled, and information depending on an accumulated value of the amount of reduced carbon dioxide is displayed (see, for example, Abstract and  FIGS. 2 through 4  of JP2001-078304A). 
       SUMMARY OF INVENTION 
       [0003]    According to JP2001-078304A, although the user can recognize an accumulated value of the amount of reduced carbon dioxide, the user is unable to recognize the amount of reduction in cost. 
         [0004]    The present invention has been made in view of the aforementioned problems. It is an object of the present invention to provide an electric vehicle, which allows the user to recognize an amount of reduction in cost compared with gasoline-powered vehicles. 
         [0005]    According to the present invention, there is provided an electric vehicle, which is propelled by supplying electric power from a battery to a traction motor, comprising an amount-of-consumed-electric-power calculator for calculating an amount of consumed electric power of the battery, a hypothetical-amount-of-consumed-gasoline estimator for estimating a hypothetical amount of consumed gasoline corresponding to the amount of consumed electric power, an electric-power-charge calculator for calculating an electric power charge corresponding to the amount of consumed electric power, a hypothetical-gasoline-charge calculator for calculating a hypothetical gasoline charge corresponding to the hypothetical amount of consumed gasoline, and a charge-comparing-information outputting unit for outputting an image or speech that provides information of a comparison between the electric power charge and the hypothetical gasoline charge. 
         [0006]    According to the present invention, information of a comparison between the electric power charge corresponding to the amount of consumed electric power of the battery and the hypothetical gasoline charge corresponding to the amount of consumed electric power can be output as an image or as speech. Therefore, the user of the electric vehicle can recognize the amount of reduction in cost in comparison with gasoline-powered vehicles. 
         [0007]    The electric vehicle may further comprise a charge difference calculator for calculating the charge difference between the electric power charge and the hypothetical gasoline charge, wherein the charge-comparing-information outputting unit outputs an image or speech that indicates the charge difference. Since the calculated charge difference between the electric power charge and the hypothetical gasoline charge is output as an image or as speech, the user can easily grasp the reduced cost achieved by using the electric vehicle. 
         [0008]    The amount of consumed electric power and the hypothetical amount of consumed gasoline may comprise an amount of consumed electric power and a hypothetical amount of consumed gasoline, respectively, per unit time or per unit traveled distance, and the charge-comparing-information outputting unit may output an image or speech that indicates the electric power charge and the hypothetical gasoline charge based on the amount of consumed electric power and the hypothetical amount of consumed gasoline per unit time or per unit traveled distance. The comparison results can thus be output with precision. 
         [0009]    The electric vehicle may further comprise a storage unit for storing, in association with each other, a range of states of charge of the battery charged from a charging station, and an electric power unit cost at the charging station while the battery is being charged from the charging station, wherein the electric-power-charge calculator calculates the electric power charge using the amount of consumed electric power and the electric power unit cost at the charging station. In this manner, the cost for the amount of consumed electric power can be reflected more precisely, thereby allowing the user to easily grasp the cost difference, if any, between electric power unit costs at different charging stations and in different charging time zones. 
         [0010]    The storage unit may store results of charging processes at a plurality of charging stations. Comparison results for a longer period of time can thus be output with precision. 
         [0011]    The electric vehicle may further comprise a position detector for detecting the position of the electric vehicle, wherein the hypothetical-gasoline-charge calculator calculates the hypothetical gasoline charge using a gasoline unit cost corresponding to a geographic region where the electric vehicle is presently located. The comparison results can thus be output with precision. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0012]      FIG. 1  is a block diagram of an electric vehicle system including electric vehicles according to an embodiment of the present invention; 
           [0013]      FIG. 2  is a flowchart of a process sequence during charging of the electric vehicle; 
           [0014]      FIG. 3  is a diagram showing an example of a relationship between the state of charge of a battery used by the electric vehicle, and the unit price of electric power; 
           [0015]      FIG. 4  is a flowchart of a charge difference display process during traveling of the electric vehicle; 
           [0016]      FIG. 5  is a flowchart of a process for determining a present amount of consumed electric power according to the embodiment; 
           [0017]      FIG. 6  is a flowchart of a process for determining an electric power charge corresponding to a present amount of consumed electric power according to the embodiment; 
           [0018]      FIG. 7  is a flowchart of a process for determining a present hypothetical amount of consumed gasoline according to the embodiment; 
           [0019]      FIG. 8  is a diagram showing a relationship between traction energy and a corresponding hypothetical amount of consumed gasoline according to the embodiment; 
           [0020]      FIG. 9  is a diagram showing a relationship between a parked idling time and a corresponding hypothetical amount of consumed gasoline according to the embodiment; 
           [0021]      FIG. 10  is a diagram showing a relationship between an air conditioner load and a corresponding hypothetical amount of consumed gasoline according to the embodiment; 
           [0022]      FIG. 11  is a flowchart of a process for acquiring gasoline unit price information, and for calculating a hypothetical gasoline charge according to the embodiment; and 
           [0023]      FIG. 12  is a view showing in concise form an example of a display screen according to the embodiment. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
     A. Embodiment 
     1. Explanation of Arrangement 
     (1) Overall Electric Vehicle System  10   
       [0024]      FIG. 1  is a block diagram of an electric vehicle system  10  (hereinafter also referred to as a “system  10 ”) for multiple electric vehicles  12  according to an embodiment of the present invention. The system  10  includes a plurality of electric vehicles  12 , a plurality of charging stations  14   a,    14   b,  and an external server  16 . 
         [0025]    In the system  10 , each of the electric vehicles  12  can be charged at a desired one of the charging stations  14   a,    14   b,  and can also acquire information concerning an electric power unit cost [yen/kW] (electric power unit cost information Ipc), as well as information concerning gasoline unit cost [yen/1] (gasoline unit cost information Igc) from the charging stations  14   a,    14   b  or the external server  16 . Each of the electric vehicles  12  can display a charge difference D [yen] between an electric power charge PC [yen] and a hypothetical gasoline charge GC [yen] based on the amount of electric power Cp [kW] consumed by the electric vehicle  12 , the electric power unit cost information Ipc, and the gasoline unit cost information Igc. 
         [0026]    In the present embodiment, the amount of consumed electric power Cp, the electric power charge PC, the hypothetical gasoline charge GC, and the charge difference D are given in relation to a present traveling event of the electric vehicle  12  (after a later-described electronic controller  34  is turned on). However, the foregoing information may be given in other units (e.g., day, month, year). 
         [0027]    In  FIG. 1 , internal structural details of one of the electric vehicles  12  are illustrated, whereas the structural details of the other electric vehicles  12  are omitted from illustration. 
       (2) Electric Vehicle  12   
       [0028]    Each of the electric vehicles  12  includes a traction motor  20 , a battery  22 , a connector  24 , a state of charge sensor  26  (hereinafter referred to as an “SOC sensor  26 ”), a voltage sensor  28 , a current sensor  30 , a navigation device  32 , an electronic controller  34  (hereinafter referred to as an “ECU  34 ”), a monitor  36 , and an air conditioner  38 . 
         [0029]    The motor  20 , which comprises a three-phase AC motor, generates drive power based on electric power supplied from the battery  22  through a DC/DC converter (not shown). The generated drive power is transmitted through a transmission (not shown) to rotate road wheels (not shown). 
         [0030]    The battery  22  serves as an electric energy storage device (energy storage), which is capable of outputting a high voltage (several hundred volts in the present embodiment). The battery  22  may comprise a lithium ion secondary battery, for example. 
         [0031]    The connector  24  can be connected to connectors  40   a,    40   b  in the charging stations  14   a,    14   b  so as to interconnect the battery  22  and the charging stations  14   a,    14   b,  so that electric power from the charging stations  14   a,    14   b  can be supplied in order to charge the battery  22 . According to the present embodiment, when the connector  24  is connected to one of the connectors  40   a,    40   b,  a switch (not shown) is turned on in order to supply electric power from a 12V battery (not shown) to the ECU  34 , the SOC sensor  26 , etc. A junction board (not shown), which is a circuit board with an integral assembly of protective functional parts for the battery  22 , is connected between the battery  22  and the connector  24 . 
         [0032]    The SOC sensor  26  detects the SOC (State of Charge) [%] of the battery  22 , and sends the detected SOC percentage to the ECU  34 . The voltage sensor  28  detects the voltage (battery voltage Vbat) [V] across the battery  22 , and sends the detected battery voltage Vbat [V] to the ECU  34 . The current sensor  30  detects a current (battery current Ibat) [I] of the battery  22 , and sends the detected battery current Ibat [I] to the ECU  34 . 
         [0033]    The navigation device  32  identifies the present position of the electric vehicle  12  using GPS (Global Positioning System) and provides route guidance information to the user. The navigation device  32  has a communication unit  42 , an input/output unit  44 , a control unit  46 , and a storage unit  48 . 
         [0034]    The ECU  34  calculates the electric power charge PC and the hypothetical gasoline charge GC, and displays the charge difference D therebetween on the monitor  36 . The ECU  34  has a communication unit  50 , an input/output unit  52 , a control unit  54 , and a storage unit  56 . Details concerning operations of the ECU  34  will be described later. 
         [0035]    The monitor  36  outputs screens and speech for providing route guidance information from the navigation device  32 , and also outputs screens and speech for providing charge difference guidance information from the ECU  34 . In the present embodiment, the monitor  36  doubles as a monitor for the navigation device  32 . However, the monitor  36  may also be a display unit for displaying various meters on the instrument panel of the electric vehicle  12 . 
         [0036]    In  FIG. 1 , the thick lines shown as interconnecting the components represent electric power lines, and the thin lines interconnecting the components represent communication lines. 
       (3) Charging Stations  14   a,    14   b    
       [0037]    According to the present embodiment, the charging station  14   a  is a public station comprising the connector  40   a,  a communication unit  60   a,  an input/output unit  62   a,  a control unit  64   a,  and a storage unit  66   a.  The charging station  14   b  is a private station comprising the connector  40   b,  an input/output unit  62   b,  a control unit  64   b,  and a storage unit  66   b.    
         [0038]    The charging station  14   a  is located in a location accessible by the public (e.g., a gas station or the parking lot of a convenience store), which can be used by anyone provided that a payment is made. More specifically, the storage unit  66   a  of the charging station  14   a  stores an electric power unit cost UPp [yen/kW], so that when the user uses the charging station  14   a,  the user is asked to pay for the charged amount of electric power at the charging station  14   a.  On the other hand, the charging station  14   b  is installed in an individual&#39;s home, and the user is charged with an amount of electric power supplied from the charging station  14   b,  together with an additional amount of electric power consumed by the individual&#39;s home. More specifically, the storage unit  66   b  of the charging station  14   b  does not store an electric power unit cost UPp, so that when the user uses the charging station  14   b,  the user cannot be informed from the charging station  14   b  concerning the electric power unit cost UPp. 
       (4) External Server  16   
       [0039]    The external server  16  indicates the electric power unit cost UPp and a gasoline unit cost UPg [yen/1] for each of the electric vehicles  12 . The external server  16  has a communication unit  70 , an input/output unit  72 , a control unit  74 , and a storage unit  76 . 
       2. Process Sequence for Displaying Charge Difference 
       [0040]    A process sequence of the ECU  34  for displaying the charge difference D will be described below. 
       (1) Process Sequence When the Battery  22  is Charged 
       [0041]      FIG. 2  is a flowchart of a process sequence of the electric vehicle  12  when the electric vehicle  12  is charged. 
         [0042]    In step S 1 , when the user connects the connector  24  to either the connector  40   a  or the connector  40   b,  thereby turning on the ECU  34  and the SOC sensor  26 , etc., the SOC sensor  26  detects the SOC of the battery  22  before the battery  22  starts to be charged, and sends the detected SOC to the ECU  34 . The ECU  34  stores the received SOC in the storage unit  56 . 
         [0043]    In step S 2 , the ECU  34  deletes the electric power unit cost information Ipc corresponding to SOCs having higher values than the SOC detected in step S 1 , from among the electric power unit cost information Ipc that is stored in the storage unit  56 . It is thus possible to store electric power unit cost information Ipc in the storage unit  56  concerning only electric power that will be charged from now on. 
         [0044]    In step S 3 , the ECU  34  acquires the electric power unit cost information Ipc concerning electric power that will be charged from now on. When the ECU  34  is connected to the charging station  14   a,  the ECU  34  acquires the electric power unit cost information Ipc from the charging station  14   a.  More specifically, the control unit  54  of the ECU  34  sends a request for electric power unit cost information Ipc through the communication unit  50  to the charging station  14   a.  In response to the request received through the communication unit  60   a,  the control unit  64   a  of the charging station  14   a  reads the electric power unit cost information Ipc from the storage unit  66   a,  and sends the read electric power unit cost information Ipc through the communication unit  60   a  to the ECU  34 . The control unit  54  of the ECU  34 , which has received the electric power unit cost information Ipc through the communication unit  50   a,  stores the received electric power unit cost information Ipc in the storage unit  56 . 
         [0045]    When the ECU  34  is connected to the charging station  14   b,  the ECU  34  acquires electric power unit cost information Ipc from the external server  16 . More specifically, the control unit  54  of the ECU  34  sends a request for electric power unit cost information Ipc through the communication unit  50  to the external server  16 . In response to the request received through the communication unit  70 , the control unit  74  of the external server  16  reads the electric power unit cost information Ipc from the storage unit  76 , and sends the read electric power unit cost information Ipc through the communication unit  70  to the ECU  34 . The control unit  54  of the ECU  34 , which has received the electric power unit cost information Ipc through the communication unit  50 , stores the received electric power unit cost information Ipc in the storage unit  56 . 
         [0046]    In step S 4 , the battery  22  is charged with electric power from the charging station  14   a  or the charging station  14   b.    
         [0047]    In step S 5 , when the charging process is finished, the SOC sensor  26  detects the SOC of the battery  22 , which has been charged, and sends the detected SOC to the ECU  34 . The control unit  54  of the ECU  34  stores the received SOC in the storage unit  56 . As a result, the acquired electric power unit cost information Ipc is stored in the storage unit  56  in association with the SOC (step S 1 ) before the battery  22  begins to be charged, and in association with the SOC (step S 5 ) after the battery  22  stops being charged. More specifically, the storage unit  56  stores, as a set in a table  80  ( FIG. 3 ), the SOC before the battery  22  starts being charged, the SOC after the battery  22  stops being charged, and the electric power unit cost information Ipc. In  FIG. 3 , the electric power unit cost information Ipc in a range of SOCs from 60% to 90% is stored in a present process sequence (60% represents the SOC before the battery  22  starts to be charged, and 90% represents the SOC after the battery  22  stops being charged). The electric power unit cost information Ipc, in a range of SOCs from 0% to 40%, and the electric power unit cost information Ipc in a range of SOCs from 40% to 60% were stored during previous process sequences. 
       (2) Process Sequence When the Electric Vehicle  12  Travels 
       [0048]      FIG. 4  is a flowchart of a charge difference display process of the electric vehicle  12  when the electric vehicle  12  travels. The charge difference display process is a process (including processes ancillary thereto) for displaying on the monitor  36  the charge difference D between the electric power charge PC and the hypothetical gasoline charge GC, based on the amount of consumed electric power Cp, the electric power unit cost information Ipc, and the gasoline unit cost information Igc, etc. Hereinafter, values determined or calculated in a present process sequence (one cycle from steps S 11  through S 20  in  FIG. 4 ) will be accompanied by the term “(present)”, and values determined or calculated in a previous process sequence (one cycle from steps S 11  through S 20  in  FIG. 4 ) will be accompanied by the term “(previous)”. 
         [0049]    In step S 11 , the ECU  34  determines a present traveled distance L [km]. The traveled distance L represents a traveled distance in a present traveling event, i.e., a traveled distance after the ECU  34  has been turned on. However, as described later, the traveled distance L may represent another traveled distance. In step S 12 , the ECU  34  determines a present amount of consumed electric power, i.e., an amount of consumed electric power Cp (present) [kW]. 
         [0050]      FIG. 5  is a flowchart of a process for determining the present amount of consumed electric power Cp (present). In step S 31  shown in  FIG. 5 , the ECU  34  determines whether or not the present process of step S 12  is the first process that occurs after the process sequence shown in  FIG. 4  has started. If the present process of step S 12  is the first process (step S 31 : YES), then the voltage sensor  28  detects an initial voltage V 1  [V] across the battery  22 , and the current sensor  30  detects an initial current I 1  [A] of the battery  22 . Then in step S 32 , the voltage sensor  28  and the current sensor  30  send the detected initial voltage V 1  and the detected initial current I 1  to the ECU  34 . 
         [0051]    In step S 33 , the ECU  34  calculates an initial electric power P 1  [kW] of the battery  22  based on the initial voltage V 1  and the initial current I 1 . 
         [0052]    If, in step S 31 , the present process of step S 12  is not the first process after the process sequence shown in  FIG. 4  has started (step S 31 : NO), then the voltage sensor  28  detects a present battery voltage Vb (battery voltage Vb (present)), and the current sensor  30  detects a present battery current Ib (battery current Ib (present)). Then in step S 34 , the voltage sensor  28  and the current sensor  30  send the detected battery voltage Vb (present) and the detected battery current Ib (present) to the ECU  34 . 
         [0053]    In step S 35 , the ECU  34  calculates a present battery electric power Pb (battery electric power Pb (present)) based on the battery voltage Vb (present) and the battery current Ib (present). 
         [0054]    In step S 36 , the ECU  34  subtracts the battery electric power Pb (present) from the previous battery electric power Pb (battery electric power Pb (previous)), and thereby calculates a present amount of consumed electric power Cp (amount of consumed electric power Cp (present)). If the electric vehicle  12  is currently operating in a regenerative mode, then since the battery electric power Pb (present) is greater than the battery electric power Pb (previous), the amount of consumed electric power Cp (present) is negative. 
         [0055]    In step S 13  shown in  FIG. 4 , the ECU  34  converts the amount of consumed electric power Cp (present) calculated in step S 12  into an amount of money, and thereby calculates an electric power charge PC (present).  FIG. 6  is a flowchart of a process for determining an electric power charge PC corresponding to the amount of consumed electric power Cp (present). 
         [0056]    In step S 41  shown in  FIG. 6 , the SOC sensor  26  detects a present SOC (SOC (present)), and sends the detected SOC (present) to the ECU  34 . In step S 42 , the ECU  34  reads the present electric power unit cost information Ipc (electric power unit cost information Ipc (present)), and acquires an electric power unit cost UPc (present) corresponding to the SOC (present). 
         [0057]    In step S 43 , the ECU  34  multiplies the amount of consumed electric power Cp (present) by the electric power unit cost UPp (present), and thereby calculates a present electric power charge PC (electric power charge PC (present)). If the electric vehicle  12  is currently operating in a regenerative mode and the amount of consumed electric power Cp (present) is negative, then the electric power charge PC (present) also is negative. 
         [0058]    In step S 14  shown in  FIG. 4 , the ECU  34  calculates a present total electric power charge Tpc (total electric power charge Tpc (present)) [yen]. The total electric power charge Tpc (present) represents the sum of the total electric power charge Tpc (previous), which represents the total of the electric power charges PC up to the previous process sequence, together with the electric power charge Cp (present). 
         [0059]    In step S 15 , the ECU  34  determines a hypothetical amount of consumed gasoline Cg (present).  FIG. 7  is a flowchart of a process for determining the hypothetical amount of consumed gasoline Cg (present). 
         [0060]    In step S 51  shown in  FIG. 7 , the ECU  34  determines a present traction energy (traction energy Ed (present)) [kWh]. The traction energy Ed (present) represents the energy consumed due to operation of the motor  20  from the previous process sequence up to the present process sequence, which can be determined depending on the traveled distance of the electric vehicle  12 , for example. Alternatively, simulated values or measured values may be acquired under certain conditions (accelerations, decelerations, etc.) with respect to the electric vehicle  12  or a corresponding gasoline-powered vehicle, in which case, the traction energy Ed (present) can be determined from the simulated values or measured values based on the traveling history (acceleration or deceleration history) of the electric vehicle  12 . 
         [0061]    In step S 52 , the ECU  34  calculates a hypothetical amount of consumed gasoline Cg 1  (present) [1]. The hypothetical amount of consumed gasoline Cg 1  (present) represents a hypothetical amount of consumed gasoline, which corresponds to the traction energy Ed (present), and which forms part of the hypothetical amount of consumed gasoline Cg (present). More specifically, as shown in  FIG. 8 , the storage unit  56  of the ECU  34  stores a table  82  of traction energies Ed and hypothetical amounts of consumed gasoline Cg 1 , which are associated with each other. The ECU  34  determines a hypothetical amount of consumed gasoline Cg 1  depending on the traction energy Ed from the table  82 . The table  82  may be referred to, for example, as a database of hypothetical amounts of gasoline consumed by a gasoline-powered vehicle, which corresponds to the specifications of the electric vehicle  12 . 
         [0062]    In step S 53 , the ECU  34  determines a parked idling time Ti (present) [sec.]. The parked idling time Ti (present) represents a time during which the electric vehicle  12  has been parked in an idling state from the previous process sequence up to the present process sequence. When the electric vehicle  12  is parked in an idling state, the speed of the electric vehicle  12  is zero and the ignition switch (not shown) is turned on. 
         [0063]    In step S 54 , the ECU  34  calculates a hypothetical amount of consumed gasoline Cg 2  (present) [1]. The hypothetical amount of consumed gasoline Cg 2  (present) represents a hypothetical amount of consumed gasoline, which corresponds to the parked idling time Ti (present) and which forms part of the hypothetical amount of consumed gasoline Cg (present). More specifically, as shown in  FIG. 9 , the storage unit  56  of the ECU  34  stores a table  84  of parked idling times Ti and hypothetical amounts of consumed gasoline Cg 2 , which are associated with each other, and from the table  84 , the ECU  34  determines a hypothetical amount of consumed gasoline Cg 2  depending on the parked idling time Ti. The table  84  may be referred to, for example, as a database of hypothetical amounts of gasoline consumed by a gasoline-powered vehicle, which corresponds to the specifications of the electric vehicle  12 . 
         [0064]    In step S 55 , the ECU  34  determines the present load (load La (present)) [A] on the air conditioner  38 . The load La (present) represents a load (consumed current) on the air conditioner  38  from the previous process sequence up to the present process sequence. 
         [0065]    In step S 56 , the ECU  34  calculates a present hypothetical amount of consumed gasoline Cg 3  (hypothetical amount of consumed gasoline Cg 3  (present)) [1]. The hypothetical amount of consumed gasoline Cg 3  (present) represents a hypothetical amount of consumed gasoline, which corresponds to the load La (present), and which forms part of the hypothetical amount of consumed gasoline Cg (present). More specifically, as shown in  FIG. 10 , the storage unit  56  of the ECU  34  stores a table  86  of loads La and hypothetical amounts of consumed gasoline Cg 3 , which are associated with each other. The ECU  34  determines a hypothetical amount of consumed gasoline Cg 3  depending on the load La from the table  86 . The table  86  may be referred to, for example, as a database of hypothetical amounts of gasoline consumed by a gasoline-powered vehicle, which corresponds to the specifications of the electric vehicle  12 . 
         [0066]    In step S 57 , the ECU  34  adds the hypothetical amounts of consumed gasoline Cg 1  (present), Cg 2  (present), and Cg 3  (present), to thereby calculate a hypothetical amount of consumed gasoline Cg (present). In other words, the hypothetical amount of consumed gasoline Cg (present) represents the sum of the hypothetical amounts of consumed gasoline Cg 1  (present), Cg 2  (present), and Cg 3  (present). 
         [0067]    In step S 16  shown in  FIG. 4 , the ECU  34  converts the hypothetical amount of consumed gasoline Cg (present) calculated in step S 15  into an amount of money, and thereby calculates a present hypothetical gasoline charge GC (hypothetical gasoline charge GC (present)) [yen].  FIG. 11  is a flowchart of a process for acquiring gasoline unit price information Igc and for calculating a hypothetical gasoline charge GC (present). 
         [0068]    In step S 61  shown in  FIG. 11 , the ECU  34  determines whether or not the present process carried out in step S 16  is the first process that occurs after the process sequence shown in  FIG. 4  has started. If it is the first process (step S 61 : YES), then in step S 62 , the ECU  34  identifies the present position of the electric vehicle  12  with the navigation device  32 . More specifically, the control unit  54  of the ECU  34  sends a request for the present position to the control unit  46  of the navigation device  32 . In response to the request, the control unit  46  of the navigation device  32  identifies the present position of the electric vehicle  12  using radio waves from GPS satellites received by the communication unit  42  and the map information stored in the storage unit  48 , and the control unit  46  sends the identified present position to the control unit  54  of the ECU  34 . 
         [0069]    In step S 63 , the ECU  34  acquires gasoline unit cost information Igc from the external server  16  via a wireless communication link. More specifically, the control unit  54  of the ECU  34  sends a request for gasoline unit cost information Igc via the communication unit  50  to the external server  16  via a wireless communication link. The request includes information concerning the present position of the electric vehicle  12 . In response to the request received through the communication unit  70 , the control unit  74  of the external server  16  reads from the storage unit  76  the gasoline unit cost UPg corresponding to the present position. The control unit  74  then sends the gasoline unit cost information Igc including the gasoline unit cost UPg through the communication unit  70  to the ECU  34 . 
         [0070]    If, in step S 61 , the present process of step S 16  is not the first process after the process sequence shown in  FIG. 4  has started (step S 61 : NO), then after step S 63 , the ECU  34  multiplies the hypothetical amount of consumed electric gasoline Cg (present) by the gasoline unit cost UPg (present), and thereby calculates a hypothetical gasoline charge GC (present) [yen] in step S 64 . 
         [0071]    In step S 17  shown in  FIG. 4 , the ECU  34  calculates a total hypothetical gasoline charge Tgc (present) [yen]. The total hypothetical gasoline charge Tgc (present) represents the sum of a total hypothetical gasoline charge Tgc (previous), which represents the total gasoline charges GC up to the previous process sequence, and the hypothetical gasoline charge Cg (present). 
         [0072]    In step S 18 , the ECU  34  calculates the charge difference D (present) between the total electric power charge Tpc (present) and the total hypothetical gasoline charge Tgc. 
         [0073]    In step S 19 , the ECU  34  updates the information displayed on the monitor  36  depending on the total electric power charge Tpc (present), the total hypothetical gasoline charge Tgc (present), and the charge difference D (present), which were calculated respectively in steps S 14 , S 17 , and S 18 . 
         [0074]      FIG. 12  shows in concise form an example of a display screen  90  of the monitor  36 . As shown in  FIG. 12 , the display screen  90  displays a present traveled distance L and a present total amount of consumed electric power Cp 1  [kW]. The total amount of consumed electric power Cp 1  represents an accumulated sum of the amounts of consumed electric power CP (present) (which are calculated after step S 12 , although this is not illustrated in  FIG. 4 ). 
         [0075]    In step S 20  shown in  FIG. 4 , the ECU  34  determines whether or not the traveling event of the electric vehicle  12  has finished. For example, the ECU  34  may determine whether or not the traveling event of the electric vehicle  12  has been completed by determining whether or not an ignition switch (not shown) has been turned off. If the traveling event of the electric vehicle  12  has not finished (step S 20 : NO), then control returns to step S 11 . If the traveling event of the electric vehicle  12  has finished (step S 20 : YES), then in step S 21 , the ECU  34  stores the total electric power charge Tpc (present), the total hypothetical gasoline charge Tgc (present), and the charge difference D (present) in the storage unit  56 . 
         [0076]    According to the present embodiment, a single processing cycle made up of steps S 11  through S 20  shown in  FIG. 4  is performed within each unit time (e.g., every 5 seconds). 
       3. Advantages of the Present Embodiment 
       [0077]    According to the present embodiment, as described above, the total electric power charge Tpc (present), the total hypothetical gasoline charge Tgc (present), and the charge difference D (present), which serve as information for comparison with the electric power charge PC (present) corresponding to the amount of consumed electric power Cp (present) of the battery  22  and the hypothetical gasoline charge GC (present) corresponding to the hypothetical amount of consumed gasoline Cg (present) that corresponds to the amount of consumed electric power Cp (present), can be output as images ( FIG. 12 ). Consequently, the user of the electric vehicle  12  can recognize the amount of reduction in cost as compared with gasoline-powered vehicles. 
         [0078]    According to the present embodiment, the ECU  34  calculates the charge difference D (present) between the total electric power charge Tpc (present) and the total hypothetical gasoline charge Tgc (present), and outputs the calculated charge difference D (present) as an image. Since the calculated charge difference D (present) is output as an image, the user can easily grasp the reduced cost achieved by using the electric vehicle  12 . 
         [0079]    According to the present embodiment, the ECU  34  outputs images representative of the total electric power charge Tpc (present) and the total hypothetical gasoline charge Tgc (present), based on the amount of consumed electric power Cp (present) and the hypothetical amount of consumed gasoline Cg (present) per unit time. Therefore, results for comparison can be output accurately. 
         [0080]    According to the present embodiment, the ECU  34  includes the storage unit  56 , which stores a range of SOCs charged by the charging stations  14   a,    14   b  and the electric power unit costs UPp at the charging stations  14   a,    14   b  in association with each other, while the battery  22  is being charged at the charging station  14   a  or the charging station  14   b.  The ECU  34  calculates the total electric power charge Tpc (present) using the amount of consumed electric power Cp (present) and the electric power unit costs UPp at the charging stations  14   a,    14   b.  In this manner, the total electric power charge Tpc (present) can be reflected more precisely, thus allowing the user to easily grasp the cost difference, if any, between the electric power unit costs UPp at the different charging stations  14   a,    14   b  and in different charging time zones. 
         [0081]    According to the present embodiment, the storage unit  56  stores the results of charging processes at a plurality of charging stations (e.g., charging stations  14   a,    14   b ) ( FIG. 3 ). Therefore, comparison results for a longer period of time can be output with precision. 
         [0082]    According to the present embodiment, the ECU  34  calculates the hypothetical amount of consumed gasoline Cg (present) using the gasoline unit cost UPg (present) corresponding to the present position of the electric vehicle  12 . Therefore, comparison results can be output with precision. 
       B. Modifications 
       [0083]    The present invention is not limited to the above embodiment, but various alternative arrangements may be adopted without departing from the scope of the invention. For example, the present invention may adopt the following alternative arrangements. 
         [0084]    In the above embodiment, the hypothetical amounts of consumed gasoline Cg 1  (present), Cg 2  (present), and Cg 3  (present) are used to calculate the hypothetical amount of consumed gasoline Cg (present). However, the present invention is not limited to such a combination, and other combinations may be used, insofar as such combinations can be used to calculate a hypothetical amount of consumed gasoline. For example, only the hypothetical amount of consumed gasoline Cg 1  (present), or a combination of the hypothetical amounts of consumed gasoline Cg 1  (present) and Cg 2  (present), or a combination of the hypothetical amounts of consumed gasoline Cg 1  (present) and Cg 3  (present) may be used to calculate a hypothetical amount of consumed gasoline. 
         [0085]    In the above embodiments, the items shown in  FIG. 12  are displayed on the screen of the monitor  36 . However, the present invention is not limited to displaying those items. Only the charge difference D (present), or a combination of the total electric power charge Tpc (present) and the total hypothetical gasoline charge Tgc (present), or a combination of the total electric power charge Tpc (present), the total hypothetical gasoline charge Tgc (present), and the charge difference D (present), or a combination of the electric power unit cost UPp (present) and the gasoline unit cost UPg (present) may be displayed on the screen of the monitor  36 . In  FIG. 12 , data concerning the present traveling event (after the ECU  34  has been turned on) are displayed. However, the present invention is not limited to displaying those data, and data for each day, month, and year may be displayed. Alternatively, data concerning traveling events up to the present time after the electric vehicle  12  has been shipped from the factory may be displayed. Further, alternatively, data at present, i.e., instantaneous data indicative of the charge difference D, may be displayed. Speech may be output instead of or concurrently with images. 
         [0086]    In the above embodiment, the electric power unit cost UPp and the gasoline unit cost UPg are acquired from the charging station  14   a  or from the external server  16 . However, the present invention is not limited to using such sources, and the electric power unit cost UPp and the gasoline unit cost UPg may also be manually input by the user using the input/output unit  52 . 
         [0087]    In the above embodiment, the process of steps S 11  through S 20  is performed per unit time. However, the present invention is not limited to such processing times. Alternatively, the process of steps S 11  through S 20  may be performed per unit distance traveled (e.g., every 100 m). 
         [0088]    In the above embodiment, the SOC of the battery  22  and the electric power unit cost UPp are associated with each other. However, a process sequence, which does not employ such an association (e.g., a process sequence with the electric power unit cost UPp being of a fixed value), may be carried out. The above association may also be updated by updating only the immediately preceding data (e.g., only one electric power unit cost UPp) without updating any data previous thereto. 
         [0089]    In the above embodiment, the amount of consumed electric power Cp (present) is converted into a monetary amount, after which the total electric power charge Tpc (present) is calculated (steps S 12  through S 14  in  FIG. 4 ). However, the present invention is not limited to such a process sequence. An accumulated value made up of respective amounts of consumed electric power Cp (present) may be determined, and then the accumulated value may be multiplied by the electric power unit cost UPp (present), to thereby calculate the total electric power charge Tpc (present). 
         [0090]    In the above embodiment, the gasoline unit cost UPg is acquired only one time ( FIG. 11 ). However, the gasoline unit cost UPg may be updated as many times as needed by repeating the process of steps S 62  and S 63 . Further, in the above embodiment, the gasoline unit cost UPg is acquired at the current traveled position of the electric vehicle  12 . However, the present invention is not limited to using such a gasoline unit cost UPg. For example, the gasoline unit cost UPg may be acquired at the locations of the charging stations  14   a,    14   b.