Abstract:
A charging device is provided that can terminate charging an onboard battery at a charging completion time point which is set by an user. The charging device includes: an AC-DC converter that converts AC power supplied from the external power source to DC power; an AC relay that connects and disconnects the AC-DC converter to and from the external power source; a DC relay that connects and disconnects the AC-DC converter to and from the battery; and a controller that controls the AC and DC relays. The controller is configured to perform: closing the AC relay and specifying a level of power that the external power source can supply: determining a charging start time point from the specified level of power and the charging completion time point; and starting battery charging by closing the AC and DC relays at the determined charging start time point.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a technique for charging a vehicle onboard battery using an external power source. In particular, it relates to a device that charges a high output high capacity battery for powering a motor that drives wheels of a vehicle. In this specification, the term “electric vehicle” includes a hybrid vehicle that is provided with both a motor and an engine for driving the vehicle wheels. Moreover, the term “electric vehicle” also includes a fuel cell vehicle. 
       BACKGROUND ART 
       [0002]    In order to take account of convenience of a user, a charging device for an onboard battery sometimes incorporates a timer. The user connects the electric vehicle to an external power source and sets the timer. The charging device starts when the set time point arrives. 
         [0003]    One improvement technique related to a charging device that incorporates a timer is disclosed in Patent Document 1. Patent Document 1 discloses a technique for reducing the noise of a cooling fan and/or the noise of a water pump during charging, in view of the fact that, in some cases, charging is performed during the night-time, 
       CITATION LIST 
     Patent Literature 
       [0004]    Patent Document 1: Japanese Patent Application Publication 2010-246320. 
       SUMMARY OF INVENTION 
       [0005]    This specification provides another improvement technique related to a charging device that incorporates a timer. A user sets a charging completion time point using the timer. It is necessary for the charging device to calculate a charging start time point from this charging completion time point. If a level of power that can be supplied by an external power source is already known, then it is possible to determine the charging start time point from the known level of power that can be supplied and the desired charging completion time point. However, for example, in some cases, a region over which the charging device is sold is a wide area, and a level of commercial power that can be supplied (from an external power source) may vary according to locations. In other words, in some cases, the charging device cannot specify in advance the level of power that can he supplied. If the level of power that can be supplied is unknown, then the charging device is not capable of determining the charging start time point. This specification provides a charging device and a charging method that can acquire the level of power that can be supplied by the external power source and can determine a charging start time point, and that can terminate the charging process at the charging completion time point that has been set with the timer. 
         [0006]    Normally, a charging device includes an AC-DC converter that converts AC power supplied by an external power source into DC power, an AC relay that connects and disconnects the external power source to and from the AC-DC converter, a DC relay that connects and disconnects the AC-DC converter to and from the battery, a timer, and a controller. It should be noted that there is no actual constructional difference between the “AC relay” and the “DC relay”. In this specification, the terms “AC relay” and “DC relay” are used in order to distinguish these two relays. 
         [0007]    As previously described, the timer is used for setting the charging completion time point And the controller controls the AC relay and the DC relay on the basis of the setting of the timer. Moreover, initially the AC relay and the DC relay are open. In other words, before charging starts, the external power source and the AC-DC converter are not connected together. Also the AC-DC converter and the battery are not connected together. With the charging device disclosed in this specification, after the charging completion time point has been set, the controller specifies the level of power that can be supplied by the external power source by closing the AC relay and measuring a supply voltage of the external power source. Next, the controller determines a charging start time point from the specified level of power that can be supplied and the charging completion time point. If the charging start time point is later than the present moment, the controller sets its own timer so that it will restart at the charging start time point, and then transitions to a sleep mode. The controller then restarts at the charging time point that has thus been determined, and closes the AC relay and the DC relay and starts the charging process. 
         [0008]    By the AC relay being closed, in other words by the external power source being connected, the charging device is able to know an output voltage of the external power source. In order to specify the level of power that can he supplied, in addition to knowing the output voltage, it is necessary also to know current capacity that can be supplied. It is possible to know the current capacity that can be supplied from the external power source, for example, by employing a pilot signal as defined by the SAE (Society of Automotive Engineers) standard J1772 (a standard for a charging interface for electric vehicles). In the J1772 standard; a so-called EVSE (Electric Vehicle Supply Equipment) device is defined that is connected between an external power source and a charging device (i.e. an AC-DC converter). The EVSE is a device that outputs a signal that transmits to an automobile the electrical current capacity that can be supplied by an external power source, and that is equipped with an interlock mechanism that stops supply of power when the automobile is moved. Further, in SAE-J1772, a communication protocol between the EVSE and an electric vehicle (i.e. a charging device) is prescribed, and a so-called pilot signal is defined among signal lines. This pilot signal transmits the current capacity that can be supplied by an external power source from the EVSE to the charging device. To put it in another manner, the pilot signal specifies the current capacity that can be supplied by the external power source. Moreover, it is prescribed that bidirectional communication should be possible via the communication line through which the pilot signal is transmitted, so that it is also possible for a command to be issued from the charging device side to the EVSE for starting supply of power. With this meaning, the pilot signal line is also called as a control pilot line. The value obtained by multiplying the current capacity that can be supplied by the external power source by its output voltage is equivalent to the level of power that can be supplied by the external power source. 
         [0009]    If the charging device that is disclosed in the present specification conforms to the SAE-J1772 standard, then it is capable of utilizing the pilot signal described above. If it is possible to know the output voltage and the current capacity that can be supplied by the external power source, then it is possible to determine the level of power that can be supplied (=[the output voltage]×[the current capacity that can be supplied]). 
         [0010]    It should be noted that a CCID device (Charging Circuit Interrupt Device) is also defined by SAE-J1772, and this device includes an AC relay that disconnects the external power source from the charging device (i.e. from the AC-DC converter). Such an AC relay of the CCID is an example of the AC relay that is to be included in the charging device disclosed in the present specification. 
         [0011]    The charging device disclosed in the present specification has the following further advantageous aspects. As previously described, two relays (the AC relay and the DC relay) are connected between the external power source and the battery. With the charging device described above, the DC relay is not closed until charging is actually started. Thus there is no loss of durability of the DC relay with the charging device disclosed in the present specification, since the number of times that the DC relay is changed over is reduced. 
         [0012]    A closed circuit voltage of the battery (Closed Circuit Voltage: CCV) cannot be measured if the DC relay is not closed. Thus, the controller may be configured to measure an open circuit voltage of the battery (Open Circuit Voltage: OCV) before the charging process is started (i.e. without closing the DC relay), and to terminate the charging process without closing the DC relay if the open circuit voltage is higher than a predetermined voltage threshold, in other words if the SOC (State Of Charge) of the battery is sufficiently high. Thus, due to reduction of the number of times that the DC relay is closed, there is no deterioration of the durability of the DC relay. 
         [0013]    The present specification also provides a novel charging method. This method includes the following three steps: (1) specifying the level of power that can be supplied by an external AC power source; (2) determining a charging start time point from a charging completion time point set by a user and a specified level of power that can be supplied; and (3) at the charging start time point, closing a relay that connects together a battery and an AC-DC converter that converts the power of the external AC power source into DC. This method is also capable of terminating the charging process at the charging completion time point that has been set with the timer. 
         [0014]    The electric vehicle provided with the charging device disclosed in the present specification or a part of the charging device is also an aspect of the novel technique disclosed in the present specification. 
         [0015]    The details of the technique disclosed in the present specification and yet further improvements will now be explained in terms of an embodiment. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0016]      FIG. 1  is a schematic figure showing a charging system for an electric vehicle; 
           [0017]      FIG. 2  is a block diagram of the charging system; and 
           [0018]      FIG. 3  is a flow chart for charging processing. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0019]    An electric vehicle  100  according to an embodiment will now be explained with reference to the drawings. A schematic illustration of a charging system for the electric vehicle  100  is shown in  FIG. 1 . And a block diagram of the charging system is shown in  FIG. 2 . Here, the term “charging system” means a group of devices that regulate the flow of electrical energy from an external power source to a battery of the vehicle. Moreover,  FIGS. 1 and 2  show only those devices that are necessary for explanation of the present invention, and it should be noted that not all the devices included in the electric vehicle are shown. 
         [0020]    An outline of the charging system will now be explained with reference to  FIG. 1 . The electric vehicle  100  is a single motor type electric vehicle that is propelled by a motor  3 . A high output high capacity battery  4  is mounted to the electric vehicle  100 , and DC power of the battery  4  is converted by an inverter  2  into AC power which is supplied to the motor  3 . While the battery  4  can be charged with regenerated power by utilizing the energy of deceleration of the vehicle, it is also possible to charge the battery  4  from an external power source (i.e. from a commercial power source  93 ). The commercial power source  93  provides AC power at, for example, 100 volts. 
         [0021]    Charging from the external power source is performed via an EVSE  8 . A plug  91  is inserted into a power socket  92  that is provided in a residence, so that the EVSE  8  acquires power from the external power source  93 . A cable  7  extends from the EVSE  8 , and a charging plug  6  is attached to the end of that cable. The charging plug  6  is inserted into a connector  5  of the vehicle  100 , and power is supplied from the external power source  93  to the vehicle  100  via the EVSE  8 . A charging device  10  is provided to the electric vehicle  100 , and this converts the AC power supplied by the external power source  93  into DC power which is outputted to the battery  4 . 
         [0022]    A console of a timer  9  is provided next to the connector  5  of the vehicle  100 . The user is able to input a charging completion time by using this console. The main circuitry of the timer  9  is implemented in the charging device  10 . The charging device  10  operates so that charging is completed at a set charging completion time. The charging processing will be explained subsequently in detail. 
         [0023]    The charging system will now be explained in detail with reference to  FIG. 2 . The EVSE  8  comprises a power leakage detector  8   a , an AC relay  8   b , and a control circuit  8   c . The AC relay  8   b  is a switch that connects and disconnects the external power source  93  to and from the vehicle  100 . Initially, this AC relay  8   b  is open. In other words, initially, the external power source  93  and the EVSE  8  are electrically disconnected from one another. The AC relay  8   b  is controlled by the control circuit  8   c . If the power leakage detector  8   a  detects power leakage, the control circuit  8   c  opens the AC relay  8   b , in other words cuts off the vehicle  100  from the external power source  93 . The control circuit  8   c  sends a pilot signal to the charging device  10  of the vehicle via the cable  7 . “CPLT” in  FIG. 2  denotes a control pilot signal line (hereinafter termed the “CPLT line”), and the pilot signal is sent via this line. Bidirectional communication can be performed via this CPLT line. The details will be described hereinafter. The EVSE  8  including the AC relay  8   b  also functions as a CCID (Charging Circuit Interrupt Device). The other two lines of the cable  7  are lines for supplying power. 
         [0024]    The charging device  10 , which receives power from the EVSE  8 , is provided with an AC-DC converter  13  and a conditioning circuit  17 . The AC power supplied from the EVSE  8  is converted into DC power by the AC-DC converter  13 . For example, the AC-DC converter  13  may convert inputted commercial 100 VAC power into 300 volts DC, this being the rated voltage of the battery  4 . The output current of the AC-DC converter  13  is smoothed by the conditioning circuit  17 , and is then supplied to the battery  4 . A first voltage sensor  12  that measures AC voltage is provided to the input side of the AC-DC converter  13 , and a second voltage sensor  15  that measures DC voltage is provided to the output side of the AC-DC converter  13 . Moreover, respective capacitors  14  and  16  for current smoothing are connected to the input side and the output side of the conditioning circuit  17 . The sensor data from the voltage sensors  12  and  15  is sent to a charging controller  18 . And the charging controller  18  controls the AC-DC converter  13  and the conditioning circuit  17  on the basis of the state of the sensor data from the voltage sensors and the state of the CPLT signal. The AC-DC converter  13  is provided with many switching circuits, and the charging controller  18  provides switching commands (i.e. PWM signals) to those switching circuits. To express this in another manner, the charging controller  18  is capable of changing over the AC-DC converter  13  between activating and deactivating. The charging controller  18  is also capable of sending commands to the EVSE  8  via the CPLT line (as will be described hereinafter). Moreover, the charging controller  18  controls a DC relay  31  of the vehicle, and stores the state of charge (SOC: State Of Charge) and certain results in a non-volatile memory  19 . Here, this DC relay  31  is a switch that connects or disconnects the battery  4  to and from the drive system of the vehicle. The DC relay  31  is also called the “main system relay”. 
         [0025]    A third voltage sensor  23  is connected to the battery  4 . This third voltage sensor  23  is connected to the battery  4  without any relationship to the DC relay  31 , and measures the open circuit voltage (OCV: Open Circuit Voltage) of the battery  4 . The open circuit voltage of the battery  4  as measured by the third voltage sensor  23  is provided to the charging controller  18 . 
         [0026]    The battery  4  is also connected to the inverter  2  via the DC relay  31 . The inverter  2  is provided with a voltage raising circuit  2   a  and an inverter circuit  2   b , and a motor controller  2   c  supplies commands (i.e. PWM signals) to switching circuits included in those devices. It should be noted that the character string “C-CNTL” in  FIG. 2  denotes the “charge controller”, while the character string “M-CNTL” denotes the “motor controller”. 
         [0027]    The pilot signal protocol will now be explained in general terms. When the external power source  93  is connected, the EVSE  8  (i.e. the control circuit  8   c ) raises the potential on the CPLT line to a voltage V 3  (typically 12 V). The charging device  10  (i.e. the charging controller  18 ) monitors the potential on the CPLT line, detects the fact that its potential has risen to the voltage V 3 , and thus knows that a supply of power can be received from the EVSE  8 . The potential on the CPLT line also functions as a message (i.e. as a command) from the charging controller  18  to the EVSE  8 . In order to know the current capacity that can be received, the charging controller  18  lowers the potential on the CPLT line to a voltage V 2  (typically 9 V). When the EVSE  8  (i.e., its control circuit  8   c ) detects the fact that the potential on the CPLT line has dropped to the voltage V 2 , it checks the voltage and the current of the external power source  93 , specifies the current capacity that it can supply, and sends this to the charging controller  18 . In concrete terms, the EVSE  8  outputs a pulse signal to the CPLT line. At this time, the duty ratio of the pulse signal specifies the current capacity that can be supplied. The charging device  10  monitors this pulse signal on the CPLT line, and thus becomes aware of the current capacity that can be supplied. Then, after having completed preparations for charging, the charging device  10  closes the DC relay  31  (in other words, connects the charging device  10  and the battery  4  together), and also drops the potential on the CPLT line to a voltage V 1  (typically 6 V). The fact that the potential on the CPLT line drops to the voltage V 1  means, to the EVSE  8 , that the start of charging is being commanded. Thus, when the EVSE  8  detects that the potential on the CPLT line has dropped to the voltage V 1 , it closes the AC relay  8   b . The external power source  93  and the charging device  10  are thus electrically connected together, and charging starts. Since the protocol related to the pilot signal is prescribed in SAE-J1772, reference should be made thereto for further details. 
         [0028]    The charging process performed by the charging controller  18  will now be explained. A flow chart for this charging processing is shown in  FIG. 3 . The charging controller  18  starts the process of  FIG. 3  when a start switch that is provided upon the console of the timer  9  is pressed. Moreover, in some cases, connection of the charging plug  6  of the EVSE  8  to the vehicle side connector  5  may function as a trigger for the start of charging. In other words, it is also possible for the process of  FIG. 3  to be started when the charging plug  6  is connected to the vehicle side connector  5 . 
         [0029]    First, the charging controller  18  Checks whether or not an end time point is set (step S 2 ). If the end time point has been set with the timer  9  (YES in step S 2 ), then the charging controller  18  lowers the potential on the CPLT line to the voltage V 2 , and acquires the current capacity that can be supplied by the external power source  93  via the EVSE  8  (step S 3 ). Next, the charging controller  18  drops the potential of the CPTL line to the voltage V 1 , and thus issues a command to the EVSE  8  to close the AC relay  8   b  (step S 4 ). When the AC relay  8   b  is closed, the external power source  93  and the charging device  10  become electrically connected. Then the charging controller  18  measures the output voltage of the external power source  93  with the first voltage sensor  12  (step S 5 ). And, from the current capacity and the output voltage that can be supplied by the external power source  93 , the charging controller  18  specifies the level of power that can be supplied. 
         [0030]    Next, the charging controller  18  measures the open circuit voltage of the battery  4  using the third voltage sensor  23 . The charging controller  18  estimates the remaining capacity SOC (State Of Charge) of the battery  4  from its open circuit voltage (step S 6 ). Moreover, from the power that can be supplied by the external power source  93  and from the SOC, the charging controller  18  calculates the time period required for fully charging the battery  4  (i.e. the charging period) (step S 7 ). This charging period is calculated using [the level of power that can be supplied (in Wh: watt-hours)]/[the vacant capacity of the battery  4  (in W: watts)]. Here, [the vacant capacity of the battery  4  (in W: watts)] is obtained by: [the full charge capacity of the battery  4  (in W: watts)]×(100 SOC)×0.01. 
         [0031]    The charging controller  18  determines a charging start time point (step S 8 ) from the charging completion time point set on the timer and the charging period. And, if the charging start time point is not earlier than the present time point (NO in step S 9 ), then the charging controller  18  opens the AC relay  8   b  (in step S 10 ), sets its own timer so as to restart at the charging start time point, and transitions into a sleep mode (step S 12 ). This sleep mode is the same as the “sleep mode” of a personal computer, and is a mode in which only a self-timer routine remains being activated, while other functions are deactivated. 
         [0032]    On the other hand, if no end time point is set (NO in step S 2 ), or if the charging start time point is earlier than the present time point (YES in step S 9 ), then the charging controller  18  performs the process of step S 22  and subsequent steps. It should he noted that the charging controller  18  starts from the process of step S 22  when restarting from the sleep mode. 
         [0033]    The charging controller  18  acquires the open circuit voltage of the battery  4  by using the third voltage sensor  23 , and terminates the process without closing the DC relay  31  if this open circuit voltage is higher than a predetermined threshold voltage (YES in step S 22 , and steps S 26  and S 27 ). The fact that the open circuit voltage is higher than the predetermined threshold voltage implies that the SOC of the battery  4  is already sufficient. In other words, if the charging controller  18  decides that the SOC of the battery  4  is high and that charging is unnecessary, then it terminates the charging process without closing the DC relay  31  even once. Typically, the voltage threshold is set at the rated output voltage of the battery  4 . Generally, if the battery is sufficiently charged, its output voltage is slightly higher than its rated output voltage. 
         [0034]    On the other hand, if the open circuit voltage of the battery  4  is lower than the predetermined threshold voltage (NO in step S 22 ), then the charging controller  18  lowers the potential on the CPLT line to the voltage V 1 , and closes the AC relay  8   b . Additionally, the charging controller  18  also closes the DC relay  31  (step S 23 ). Next, the charging controller  18  supplies a PWM signal to the switching circuitry of the AC-DC converter  13 , and thus starts the charging process (step S 24 ). 
         [0035]    The charging controller  18  continues the charging process until the SOC of the battery  4  becomes greater than a predetermined threshold value (NO in step S 25 ). To express this in other words, the charging controller  18  charges the battery  4  until it reaches full charge. When the SOC becomes greater than the threshold value (YES in step S 25 ), the charging controller  18  opens the AC relay  8   b  and the DC relay  31  (step S 26 ), and terminates the charging process (step S 27 ). It should be understood that, in step S 25 , the charging controller  18  determines the SOC based on the closed circuit voltage (CCV: Closed Circuit Voltage) of the battery  4 . 
         [0036]    The advantages of the charging device  10  of this embodiment will now he described. When a charging end time point is set with the timer, the charging device  10  specifies the level of power that can be supplied by the external power source  93 , and determines a charging start time point. Accordingly, the charging device  10  is able to start charging in such a manner that charging will certainly end at the appointed charging end time point, even if the charging device  10  is being used in a region in which the level of power that can be supplied by the external power source  93  is not clear. 
         [0037]    The charging device  10  does not operate the DC relay  31  until charging is to be started. The DC relay  31  is a very important component of the electric vehicle  100 . Since, with this charging device  10 , the number of times that this system main relay is operated is reduced, accordingly the durability of the system main relay may not deteriorate. 
         [0038]    Points to keep in mind in connection with the embodiment described above will now be mentioned. The charging controller  18  of this embodiment acquires the SOC of the battery  4 , and calculates the charging period (steps S 6  and S 7  of  FIG. 3 ). It would also be possible to arrange for the charging controller to determine the charging start time point from a predetermined expected charging capacity, the level of power that can be supplied by the external power source, and the set time on the timer. Typically, the predetermined expected charging capacity will correspond to 100% charging capacity. In this case, the charging period will be equivalent to the time period required to charge up from a SOC of 0% to a SOC of 100%. By employing such a predetermined expected charging capacity, the charging device is able to determine the charging period without acquiring the SOC of the battery. 
         [0039]    The vehicle of the above embodiment was an electric vehicle equipped with a single motor. However, the technique disclosed in the present specification can also be applied to a so-called plug-in type hybrid vehicle that is equipped both with a motor and with an engine for driving the wheels of the vehicle. 
         [0040]    Representative, non-limiting examples of the present invention will now be described in further detail with reference to the attached drawings. This detailed description is merely intended to teach a person of skill in the art further details for practicing preferred aspects of the present teachings and is not intended to limit the scope of the invention. Furthermore, each of the additional features and teachings disclosed below may be utilized separately or in conjunction with other features and teachings to provide improved a charging device for an electric vehicle, as well as methods for using and manufacturing the same. 
         [0041]    Moreover, combinations of features and steps disclosed in the following detail description may not be necessary to practice the invention in the broadest sense, and are instead taught merely to particularly describe representative examples of the invention. Furthermore, various features of the above-described and below-described representative examples, as well as the various independent and dependent claims, may be combined in ways that are not specifically and explicitly enumerated in order to provide additional useful embodiments of the present teachings. 
         [0042]    All features disclosed in the description and/or the claims are intended to be disclosed separately and independently from each other for the purpose of original written disclosure, as well as for the purpose of restricting the claimed subject matter, independent of the compositions of the features in the embodiments and/or the claims. In addition, all value ranges or indications of groups of entities are intended to disclose every possible intermediate value or intermediate entity for the purpose of original written disclosure, as well as for the purpose of restricting the claimed subject matter, 
         [0043]    Specific examples of the present invention have been described in detail; however, these are mere exemplary indications and thus do not limit the scope of the claims. The art described in the claims includes modifications and variations of the specific examples presented above. Technical features described in the description and the drawings may technically be useful alone or in various combinations, and are not limited to the combinations as originally claimed. Further, the art described in the description and the drawings may concurrently achieve a plurality of aims, and technical significance thereof resides in achieving any one of such aims.