DESCRIPTION
TITLE OF INVENTION
ELECTRIC VEHICLE CHARGING DEVICE AND ELECTRIC VEHICLE CHARGING
SYSTEM
TECHNICAL FIELD
[0001] The present invention relates to an electric vehicle charging device and an
electric vehicle charging system that serve for charging an electric vehicle such as an
electric automobile.
BACKGROUND ART
[0002] For example, a charging device described in Japanese Patent Application
Publication No. 2003-333706 is known. This charging device serves for charging a
battery-driven forklift. This charging device can receive electric power from a facility
power supply of a plant by connecting a power supply cord thereof to a power receptacle
which is connected to the facility power supply via a breaker. Besides, the charging
device has a communication function, and information relating to the charging state is sent
to other charging devices connected to the facility power supply and received therefrom via
a communication line.
[0003] In this conventional example, a total current value that can be used by one or a
plurality of the charging devices connected to the facility power supply (this value is
referred to as a total current limit value) is set to a predetermined value. Each charging
device automatically determines the charging current value of the charging device on the
basis of the above-mentioned value (total current limit value) and charging states of other
charging devices. Therefore, the electric power consumed by the charging device when
an electric vehicle (battery-driven forklift) is charged can be adequately set without taking
into account the power supply capacity of the facility power supply that supplies electric
power to the charging devices. Therefore, the user can effectively charge the electric
vehicle without increasing the power supply capacity of the facility power supply.
[0004] By the way, when assuming a case of charging an electric vehicle (electric
automobile) at a house, it would be better that the charging current of the electric
automobile be limited so that the total amount of electric power (electric current) consumed
in the house does not exceed the ratings of a main breaker (or a limiter). For example, by
monitoring the electric current flowing in the main breaker and by stopping the supply of
charging current to the electric automobile when the electric current exceeds 90% of the
rated current of the main breaker, it is possible to prevent the main breaker from tripping.
In this case, the electric vehicle should be notified that charging is impossible when the
charging device stops charging.
[0005] As for charging of the abovementioned electric vehicles, for example, standards
- 3 -
of the Society of Automotive Engineers (SAE) stipulate that a 1 kHz pulse-width-modulated
signal (referred to as "control pilot signal") be transmitted from a charging device to an
electric automobile, and a notice relating to the upper limit value of charging current be
given by using an on-duty ratio of the pulse signal. With respect to the control pilot signal
transmitted by the charging device, the SAE standards stipulate that the pulse signal with
the on-duty ratio of greater than 96% indicates the condition that charging is impossible
(indicates an unchargeable state). Therefore, the charging device can notify the electric
automobile of the unchargeable state by setting the on-duty ratio of the pulse-widthmodulated
signal to 100% (that is, by maintaining the signal in the ON state at all times).
However, when the charging device restarts charging of the electric automobile after a
break (interrupt) of the charging, it may occur that the electric automobile makes erroneous
judgment of occurring an abnormality when the on-duty ratio changes from 100% to a
value less than 96% (for example, in electric automobiles of some types, the electric
automobile may makes an erroneous judgment of occurring an abnormality when
receiving a signal whose on-duty ratio is made 100% for an extremely short time).
DISCLOSURE OF INVENTION
[0006] The present invention is developed in view of above problem, and it is an object
of the present invention to enable normal restart of charging after the charging has been
interrupted.
[0007] In an electric vehicle charging device of the present invention, said electric
vehicle charging device being configured to be connected to an electric vehicle by a
charging cable, said electric vehicle charging device being configured to notify the electric
vehicle of at least an upper limit value of a charging current by way of transmitting a
transmission signal through a transmission line included in the charging cable, wherein the
electric vehicle charging device includes a transmission means configured to transmit the
transmission signal generated by pulse-width modulation on a line voltage of the
transmission line, and a control means configured to control the transmission means to
transmit various types of information including the upper limit value by the transmission
signal; and wherein the control means is configured to control the transmission means so
that the line voltage is once made equal to or less than a predetermined voltage and after
then restarting the transmission of the transmission signal in case of charging of the
electric vehicle is interrupted and then restarted.
[0008] In such a electric vehicle charging device, it is preferred that the control means is
configured to control the transmission means so that the line voltage is made equal to or
less than a predetermined voltage and after then restarting the transmission of the
transmission signal when a transition is made from an unchargeable state to a chargeable
state.
[0009] An electric vehicle charging system of the present invention includes the
abovementioned electric vehicle charging device and a power monitoring device
- 4 -
configured to indicate the upper limit value to the control means, wherein the control
means is configured to: determine that it is in the unchargeable state when the upper limit
value indicated by the power monitoring device is less than a predetermined threshold;
and determine that it is in the chargeable state when the upper limit value indicated by the
power monitoring device is equal to or higher than the threshold.
[0010] In such an electric vehicle charging system, it is preferred that the power
monitoring device includes a second current sensor for measuring the charging current
supplied to the electric vehicle from a power distribution board, and a first current sensor
for measuring a total consumed current supplied from a power grid to the power
distribution board; and the power monitoring device is configured to indicate the upper limit
value to the control means on the basis of the total consumed current measured by the
first current sensor, the charging current measured by the second current sensor, and a
rated current of the power distribution board.
[0011] The effect demonstrated by the electric vehicle charging device and the electric
vehicle charging system in accordance with the present invention is that charging can be
normally restarted after the charging has been interrupted.
BRIEF DESCRIPTION OF DRAWINGS
[0012] FIG. 1 includes a block diagram of an electric vehicle charging device according
to an embodiment of the present invention and a system configuration diagram of an
electric automobile charging system according to an embodiment of the present invention;
FIG. 2 is a time chart for explaining the operation of the charging device according
to the embodiment; and
FIG. 3 is a time chart for explaining the basic operation of the charging device
according to the embodiment.
DESCRIPTION OF EMBODIMENTS
[0013] An embodiment in which the technical idea of the present invention is applied to
an electric vehicle charging device (referred to hereinbelow as "charging device") and an
electric vehicle charging system disposed at a house will be explained below with
reference to the appended drawings. The electric vehicle charging device (electric
vehicle charging system) of the present embodiment is configured to charge an electric
automobile by using electric power supplied from a power grid. Note that, the electric
vehicle is not limited to the electric automobile and, for example, can be a battery-driven
forklift such as explained in the description of the related art.
[0014] As shown in FIG. 1, AC power of single-phase three-line is supplied to the house
from a power grid 100 via a house distribution board (power distribution board; will be
referred to hereinbelow as "house board") 4. The house board 4 has a main breaker 40
and a plurality of branch breakers 41. The primary side (input side) of the main breaker
40 is connected to the power grid 100. The plurality of the branch breakers 41 is branch-
5 -
connected to the secondary side (output side) of the main breaker 40. In other words, the
primary side (input side) of each branch breaker 41 is connected to the secondary side
(output side) of the main breaker 40. Note that, a limiter (current limiter) may be provided
to the primary side of the main breaker 40. A receptacle or load (lighting units,
electromagnetic cooking devices, air conditioner, and the like) is connected via an in-house
wiring to the secondary side (output side) of the branch breaker 41 (this configuration is
not shown in the figure).
[0015] As shown in FIG. 1, the electric vehicle charging system of the present
embodiment includes a charging device 1 and a power monitoring device 2.
[0016] The power monitoring device 2 includes a control unit 20, a current measuring
unit 21, and a communication unit 22. The power monitoring device 2 is also includes
current sensors (first current sensors) 210, 211 for measuring the electric current supplied
from the power grid 100 to the house board 4. The current measuring unit 21 measures
with the current sensors 210, 211 the electric currents flowing in two electric lines (two
voltage lines), other than a neutral line, among the three electric lines (lamp lines)
connected to the primary side of the main breaker 40. The current measuring unit 21
outputs the respective measured values to the control unit 20. The control unit 20 is
composed mainly of a microcomputer, and calculates an instantaneous value and/or an
integral value of electric power (supplied powder) supplied from the power grid 100 on the
basis of the current value measured by the current measuring unit 21 and the measured
value (voltage value) of the primary-side voltage (input voltage) of the main breaker 40.
The communication unit 22 performs communication with the charging device 1, for
example, based on serial communication conforming to the RS485 standard. However,
the communication system of the communication unit 22 is not limited to the RS485
standard and may be a power line communication system or a radio communication
system (for example, low-power radio communication system).
[0017] The charging device 1 includes a signal processing unit (transmission means) 10,
a residual current transformer 11, an electric leak detection unit 12, an opening-closing unit
13, a communication control unit (control means) 14, a charging cable 15, and a charging
connector 16. The charging device 1 is installed at a location near a parking space
(garage) of an electric automobile (electric vehicle) 200 and connected to one of branch
circuits branched by a branch breaker 41 (in FIG. 1, the branch circuit branched by the
branch breaker 41 on the right end of the lower stage) of the house board 4. In the
charging cable 15, a power supply line 150 for supplying an electric current (charging
current) to the electric automobile 200 and a transmission line 151 for transmitting a pilot
signal are coated by an insulating sheath, and a charging connector 16 is provided at the
distal end portion of the charging cable 15. The charging connector 16 can be
removablely inserted and connected to an insertion port (inlet) provided at the body of the
electric automobile 200. When the charging connector 16 is inserted and connected into
the insertion port, electric power (charging power) can be transmitted from the power grid
- 6 -
100 via the house board 4 and the charging device 1, and the pilot signal can be
transmitted between the signal processing unit 10 of the charging device 1 and a charging
electronic control unit (ECU; not shown in the figure) of the electric automobile 200.
[0018] The opening-closing unit 13 has an electromagnetic relay (not shown in the
figure) that is inserted in the power supply line between the branch breaker 41 and the
power supply line 150, and opens (breaks) or closes (makes) the power supply line by
ON/OFF switching the electromagnetic relay in response to an instruction from the signal
processing unit 10. The electric leak detection unit 12 is configured to detect an
unbalanced current flowing in the power supply line by the residual current transformer 11.
If the detected level of the unbalanced current exceeds a threshold, the electric leak
detection unit 12 determines that current leak has occurred and controls the openingclosing
unit 13 to open the power supply line. The communication control unit 14 has a
function (communication function) of performing communication (serial communication
conforming to the RS485 standard) with the communication unit 22 of the power
monitoring device 2 and a function (adjustment function) of adjusting the charging current
supplied to the electric automobile 200 as will be described hereinbelow. Such a
communication control unit 14 is constituted by a microcomputer and an integral circuit for
serial communication. Note that, the power monitoring device 2 is provided with a current
sensor (second current sensor) 212 for measuring a charging current supplied from the
house board 4 to the electric automobile 200. In the power monitoring device 2, the
electric current (charging current) supplied to the electric automobile 200 via the charging
device 1 is measured with the current sensor 212.
[0019] The basic charging operation of the charging device 1 will be explained below
with reference to the time chart shown in FIG. 3. When the charging connector 16 is
connected to the insertion port of the electric automobile 200 (point of time t'0), a
predetermined voltage V1 (for example, V1 = 12 V) is supplied from the signal processing
unit 10 to the transmission line 151. The electric voltage (line voltage) applied to the
transmission line 151 serves as a transmission medium for a control pilot (CPLT) signal
(referred to hereinbelow as "pilot signal"), and various types of information are exchanged
between the charging ECU and the signal processing unit 10, as will be described below,
according to the voltage level and on-duty ratio.
[0020] When the charging ECU detects the pilot signal of the voltage V1, the charging
ECU makes a switch (not shown in figure) inserted between the transmission line 151 and
ground close so as to connect a resistor (not shown in figure), thereby decreasing the
voltage level of the pilot signal from V1 to V2 (for example, V2 = 9 V) (point of time t'1).
When the signal processing unit 10 detects that the pilot signal has decreased from V1 to
V2, the signal processing unit 10 outputs a pulsed pilot signal of a predetermined
frequency (for example, 1 kHz) (point of time t'2). The signal level of the pilot signal is ±
V1, but the upper limit level has dropped to V2.
- 7 -
[0021] The on-duty ratio of the pilot signal indicates the upper limit value of the charging
current. The relationship between the upper limit value of the charging current and the
on-duty ratio is set in advance for each charging device 1. For example, the SAE
standards stipulate that when the on-duty ratio is within a range of 10% to 85%, a
numerical value (Ampere) obtained by multiplying the on-duty ratio by 0.6 is taken as an
upper limit value for a pilot signal sent by the charging device 1 (for example, when the onduty
ratio is 10%, the upper limit value is 10*0.6 = 6 Ampere). The standards also
stipulate that when the on-duty ratio is larger than 85% and equal to or less than 96%, a
numerical value (Ampere) obtained by subtracting 64 from the on-duty ratio and multiplying
the resultant difference by 2.5 be taken as the upper limit value. Thus, the pilot signal is
transmitted by superimposing the information (value) of the upper limit value on the line
voltage in the transmission line 151 as a pulse-width-modulated signal. With respect to
the pilot signal sent by the charging device 1, the SAE standards stipulate that the pilot
signal with the on-duty ratio of less than 10% (5% excluded) and the pilot signal with the
on-duty ratio of greater than 96% indicates an error or no charging allowed (charging
disallowed). It is also stipulated that the pilot signal with the on-duty ratio of 5% indicates
a condition that digital communication is needed (see SAE J 1772).
[0022] When the charging ECU detects the on-duty ratio of the pilot signal and verifies
the upper limit value of the charging current, the charging ECU decreases the voltage level
of the pilot signal (for example, by connecting a resistance) from V2 to V3 (for example, V3
= 6 V) (point of time t'3). When the signal processing unit 10 detects that the signal level
of the pilot signal has decreased from V2 to V3, the signal processing unit 10 closes the
opening-closing unit 13 to start the supply of charging power.
[0023] The charging ECU sets a current value for charging a storage battery in order to
reach a charge level of the storage battery to a target level, on the basis of the upper limit
value of charging current notified from the charging device 1 (note that, the current value is
set to be equal to or smaller than the upper limit value notified from the charging device 1),
and outputs a charging command to a charger (not shown in the figure) installed on the
electric automobile 200. When receiving the charging command, the charger charges the
storage battery while adjusting the charging current so as not to exceed the current value
set by the charging ECU (from a point of time t'3 onward). When the charge level of the
storage battery reaches the target level, the charging ECU outputs a charging end
command to the charger to stop charging the storage battery, and restores the voltage
level of the pilot signal from V3 to V2 (point of time t'4). Upon receiving the charging end
command, the charger stops charging the storage battery.
[0024] When the signal processing unit 10 detects that the pilot signal has changed from
V3 to V2, the signal processing unit 10 opens the opening-closing unit 13 to stop the
supply of AC power. Further, the charging ECU opens the switch connected to the
transmission line 151 to cut off the resistor, thereby returning the voltage level of the pilot
signal to the initial voltage value V1 (point of time t'5). When the voltage level of the pilot
- 8 -
signal returns to V1, the signal processing unit 10 stops generating a predetermined
frequency oscillation, (thereafter) maintains the voltage level of the pilot signal at V1 and
returns to the stand-by state (point of time t'6).
[0025] As described hereinabove, the charging device 1 controls the process of charging
the storage battery installed on the electric automobile 200 by switching ON/OFF the
supply of charging power to the electric automobile 200 and indicating the upper limit value
of charging current to the charging ECU of the electric automobile 200.
[0026] By the way, a large charging current of about more than ten to dozens of
Amperes is regularly necessary for charging the electric automobile 200. Meanwhile, the
rated current of the main breaker 40 (when a limiter is installed, the rated current of the
limiter and the main breaker 40) in a usual house is set to about 30 Ampere to 60 Ampere.
Therefore, in the case in which the electric automobile 200 is charged while using a load
device with large current consumption, such as an electromagnetic cooking device or air
conditioner, it is likely to occur that the main breaker 40 or limiter is made tripped if
charging the electric vehicle with a charging current of the upper limit value that has been
set in advance for the charging device 1.
[0027] Accordingly, in order to prevent the trip, the control unit 20 of the power
monitoring device 2 periodically (for example, with a spacing of 1 sec) sends from the
communication unit 22 a command (adjustment command) for setting (updating) the upper
limit value of charging current into such a current value obtained by subtracting a
difference between the total consumed current and the rated current from the present
current value of the charging current. That is, the power monitoring device 2 calculates a
value obtained by subtracting a difference between the total consumed current and the
rated current of the house board 4 from the current value of charging current, and notifies
the communication control unit 14 of this value. Note that, the total consumed current is a
sum total of the charging current and currents consumed by load devices (load-consumed
current). The total consumed current is measured, for example, using the current
sensors 210, 211 provided between the power grid 100 and the main breaker 40.
[0028] In other words, the control unit 20 of the power monitoring device 2 periodically
sends from the communication unit 22 a command (adjustment command) to set the
upper limit value of charging current to the difference value between the rated current and
the load-consumed current.
[0029] In the charging device 1, the communication control unit 14 receives the
adjustment command from the power monitoring device 2, and then instructs the signal
processing unit 10 to set the upper limit value of charging current to a value equal to or
lower than the upper limit value indicated in the adjustment command. When the signal
processing unit 10 receives the instruction from the communication control unit 14, the
signal processing unit 10 changes (adjusts) the on-duty ratio of the pilot signal on the basis
of the adjustment command received from the communication control unit 14. For
example, if the current capacity of the charging cable 15 (the allowed amount of electric
- 9 -
current that can flow in the charging cable 15) is 30 Ampere, the on-duty ratio that
originally was 50% decreases, for example, to 20% to 40%. As a result, the upper limit
value of charging current is adjusted to a value (for example, 15 Ampere) lower than the
initial 30 Ampere. Note that, if the present upper limit value is the same as the previous
upper limit value, the on-duty ratio is not changed. Note that, the communication control
unit 14 may also use a plurality of values sent by the adjustment commands from the
communication unit 22. For example, the communication control unit 14 may be
configured to calculate the average of plurality of values sent from the communication unit
22 and to indicate the upper limit value of charging current to the signal processing unit 10
on the basis of the average value.
[0030] The charging ECU of the electric automobile 200 sets again (updates) the current
value of charging current on the basis of the adjusted upper limit value, and outputs a
charging command to the charger. Upon receiving the charging command, the charger
charges the storage battery while adjusting the charging current so as not to exceed the
"new" current value that has been set by the charging ECU. As a result, the charging
current supplied to the electric automobile 200 becomes load-consumed current equal to
or less than the upper limit value set by the signal processing unit 10, and therefore the
total consumed current (sum of charging current and load-consumed current) is prevented
from exceeding the rated current of the main breaker 40.
[0031] However, it should be noted that it takes a substantial delay time between a time
point at which the charging unit 1 instructs the electric automobile 200 to reduce the
charging current and a time point at which the charging current is actually reduced at the
electric automobile 200 side. For example, if the communication control unit 14 requires
a time T2 to change the on-duty ratio of the pilot signal after receiving the adjustment
command, and the electric automobile 200 requires a time T3 to reduce the charging
current in response to the pilot signal, a delay time T1 (= T2 + T3) appears. As a result,
an overload current continuously flows through the main breaker 40 at least for the delay
time T1 and therefore the main breaker 40 can be tripped if the delay time T1 exceeds the
tripping operation time of the main breaker 40. Furthermore, in most cases, the time T2
required for changing the on-duty ratio of the pilot signal differs depending on the type of
the electric automobile 200.
[0032] Accordingly, in order to prevent the main breaker 40 from tripping when the upper
limit value of charging current is reduced, it is preferred to: interrupt the charging of the
charging ECU; and after then adjust the upper limit value of charging current to a value
lower than that before the interrupt. In this instance, as explained in the related art, when
the charging is stopped, the charging device 1 should notify the electric automobile 200 of
this charging stop. Further, as explained in the related art, the notification of the charging
stop can be given from the charging device 1 by setting the on-duty ratio of the pilot signal
to 100%. However, in a case where the transition time of the pilot signal related to a state
transition is specified, if the on-duty ratio of the pilot signal is set to 100% and again to a
- 10 -
value less than 100% (for example, 80%) during charging, an unexpected abnormality can
occur in the electric automobiles 200 of some types.
[0033] In addition, as another problem, if the charging current is small, sufficient power
cannot be supplied from a power distribution board to a charger due to internal resistance
or the like. Because of such a reason, the SAE standards does not assume (specify) to
charge the electric vehicle with the charging current of less than 6 Amperes. As a result,
in a case where the charging device 1 conforms to the SAE standards, when the allowed
value of charging current becomes to less than 6 Amperes because of, for example,
starting to use a load device, charging by the charging device 1 should be interrupted (by,
for example, setting the on-duty ratio of the pilot signal to 100%). In this case, if the onduty
ratio of the pilot signal is set to 100% and again to a value less than 100% during
charging, an unexpected abnormality can occur in the electric automobiles 200 of some
types.
[0034] In order to resolve this problem, the present embodiment is configured such that:
when charging of the electric automobile 200 is interrupted and then restarted, the
communication control unit 14 controls the signal processing unit 10 to reduce the line
voltage of the transmission line 151 to a value equal to or less than a predetermined
voltage (within a predetermined waiting time) and after then restarts to transmit the pilot
signal for which the on-duty ratio is set to a value less than 100% (for example, 80%).
Meanwhile, the charging ECU causes the charger to interrupt the charging immediately
after the on-duty ratio of the pilot signal becomes 100%. Further, the charging ECU is
configured to determine that the charging connector 16 is pulled out from the insertion port
upon detecting that the line voltage of the transmission line 151 becomes equal to or lower
than the predetermined voltage.
[0035] Therefore, with the charging device 1 of the present embodiment, it is enabled to
cause the charging ECU of the electric automobile 200 to recognize that "the charging
connector 16 has been pulled out of the insertion port" when charging of the electric
automobile 200 is interrupted and restarted (before the charging is restarted). The
predetermined voltage is a threshold for the charging ECU to determine that the charging
connector 16 has been pulled out from the insertion port. This voltage can be set, for
example, within a range from several volts to zero volts. Note that, it is preferred that the
predetermined voltage be zero volts. In the explanation below, it is assumed that the
predetermined voltage is set to zero volts.
[0036] Thus, the communication control unit 14 is configured that: setting the on-duty
ratio of the pilot signal to 100%; setting the line voltage of the transmission line 151 to the
predetermined voltage (zero volts); waiting an elapse of the predetermined waiting time;
and after then making the signal processing unit 10 start the transmission (oscillation) of
the pilot signal for which the on-duty ratio is set to a value less than 100% (for example,
80%). Upon receiving the pilot signal, the charging ECU determines that the charging
connector 16 has been inserted and connected to the insertion port. Then, the charging
- 11 -
ECU sets a current value of charging current on the basis of the upper limit value detected
from the on-duty ratio of the pilot signal and outputs a charging command to the charger,
as according to the regular processing flow (processing flow shown in FIG. 3; which has
already been explained). Having received the charging command, the charger charges
the storage battery while adjusting the charging current so as not to exceed the new
current value that has been set by the charging ECU.
[0037] The charging operation of the above-described charging device 1 will be
explained below in detail with reference to the time chart shown in FIG. 2. In the
explanation below, it is assumed that a threshold for the upper limit value of charging
current is set to 6 Amperes, and that charging of the electric automobile 200 is not allowed
when the upper limit value of charging current is restricted to less than the threshold.
[0038] First, the charging connector 16 is inserted and connected to the insertion port of
the electric automobile 200, and the voltage V1 is applied from the signal processing unit
10 to the transmission line 151. After then, the charging ECU decreases the voltage level
of the pilot signal from V1 to V2 at the point of time t1. In this instance, if an adjusted
value indicated from the control unit 20 of the power monitoring device 2 is less than 6
Amperes, the communication control unit 14 of the charging device 1 determines that
charging to the electric automobile 200 is not allowed (disallowed) by the power monitoring
device 2 and does not start the oscillation of the pilot signal. Note that, when the
oscillation of the pilot signal is not started and the on-duty ratio is maintained at 100%, the
charging ECU does not output a charging command to the charger.
[0039] And then, when the adjusted value indicated from the control unit 20 of the power
monitoring device 2 changes to a value equal to or greater than 6 Amperes for the reason
of decreasing of the consumed current because of, for example, stop the usage of a load
device, the communication control unit 14 of the charging device 1 determines that
charging of the electric automobile 200 is allowed by the power monitoring device 2. And
then, the communication control unit 14 causes the signal processing unit 10 to stop the
application of voltage to the transmission line 151 and sets the line voltage to zero volts
(point of time t2). When the predetermined waiting time elapses since the point of time t2,
the communication control unit 14 causes the signal processing unit 10 to restart the
application of voltage to the transmission line 151. When a voltage is applied to the
transmission line 151, the charging ECU makes the line voltage to V2 (point of time t3).
When detecting that the line voltage becomes V2, the signal processing unit 10 starts the
oscillation of the pilot signal (point of time t4).
[0040] When the charging ECU detects the on-duty ratio of the pilot signal and
recognizes the upper limit value of charging current, the charging ECU decreases the
voltage level of the pilot signal from V2 to V3. When the signal processing unit 10 detects
that the signal level of the pilot signal has decreased from V2 to V3, the signal processing
unit 10 closes the opening-closing unit 13 and starts the supply of charging power. The
charging ECU then sets a current value for charging the storage battery in order to reach
- 12 -
the charge level of the storage battery to the target level, on the basis of the upper limit
value of charging current sent from the signal processing unit 10, and outputs a charging
command to the charger.
[0041] If the adjusted value indicated from the control unit 20 of the power monitoring
device 2 changes to a value equal to or less than 6 Amperes, for example, due to the
increase in the total consumed current during charging, the communication control unit 14
of the charging device 1 determines that charging of the electric automobile 200 is
disallowed. The communication control unit 14 then causes the signal processing unit 10
to stop oscillating the pilot signal and maintains the on-duty ratio at 100% (from a point of
time t5 onward). When the oscillation of the pilot signal is stopped and the on-duty ratio
is maintained at 100%, the charging ECU stops outputting the charging command to the
charger.
[0042] When the adjusted value indicated from the control unit 20 of the power
monitoring device 2 is thereafter again changed to a value equal to or greater than 6
Amperes, the communication control unit 14 of the charging device 1 causes the signal
processing unit 10 to stop the application of voltage to the transmission line 151 and sets
the line voltage to zero volts (point of time t6). When a waiting time elapses since the
point of time t6, the communication control unit 14 causes the signal processing unit 10 to
restart the application of voltage to the transmission line 151. When the voltage is applied
to the transmission line 151, the charging ECU makes the line voltage to V2 (point of time
t7). When the signal processing unit 10 detects that the line voltage has become V2, the
signal processing unit 10 restarts the oscillation of the pilot signal (point of time t8).
[0043] When the charging ECU detects the on-duty ratio of the pilot signal and
recognizes the upper limit value of charging current, the ECU decreases the voltage level
of the pilot signal from V2 to V3. When the signal processing unit 10 detects that the
signal level of the pilot signal has decreased from V2 to V3, the signal processing unit 10
closes the opening-closing unit 13 and starts (restarts) the supply of charging power. The
charging ECU then sets a current value for charging the storage battery in order to reach
the charge level of the storage battery to the target level, on the basis of the upper limit
value of charging current sent from the signal processing unit, and outputs a charging
command to the charger.
[0044] As described hereinabove, in the charging device 1 of the present embodiment,
when charging of the electric automobile 200 is interrupted and then restarted, the control
means (communication control unit 14) controls the transmission means (signal
processing unit 10) so that the line voltage of the transmission line 151 (for a
predetermined standby time period) is decreased to zero volts and after then (restart) to
transmit a transmission signal. As a result, by setting the line voltage of the transmission
line 151 to zero volts, it is possible to cause the charging ECU the electric automobile 200
to recognize that the charging connector 16 has been pulled out from the insertion port.
Therefore, when the signal processing unit 10 applies the line voltage to the transmission
- 13 -
line 151 and restarts the oscillation of the pilot signal, the charging ECU determines that
the charging connector 16 has again been inserted and connected to the insertion port,
and therefore the charging ECU can start (restart) charging by the regular processing flow.
As a result, the charging can be normally restarted after the charging has been interrupted.
- 14 -
Claims
1. An electric vehicle charging device for charging an electric vehicle, said electric
vehicle charging device being configured to be connected to an electric vehicle by a
charging cable, said electric vehicle charging device being configured to notify the electric
vehicle of at least an upper limit value of a charging current by way of transmitting a
transmission signal through a transmission line included in the charging cable,
wherein the electric vehicle charging device comprises a transmission means
configured to transmit the transmission signal obtained by pulse-width modulation of a line
voltage of the transmission line, and a control means configured to control the
transmission means to transmit various types of information including the upper limit value
by the transmission signal; and
wherein the control means is configured to control, when charging of the electric
vehicle is interrupted and then restarted, the transmission means so that the line voltage is
made equal to or less than a predetermined voltage and after then restarting the
transmission of the transmission signal.
2. The electric vehicle charging device according to claim 1, wherein the control
means is configured to control, when a transition is made from an unchargeable state to a
chargeable state, the transmission means so that the line voltage is made equal to or less
than a predetermined voltage and after then restarting the transmission of the transmission
signal.
3. An electric vehicle charging system comprising: the electric vehicle charging
device according to claim 2; and a power monitoring device configured to indicate the
upper limit value to the control means,
wherein the control means is configured to: determine that it is in the
unchargeable state when the upper limit value indicated by the power monitoring device is
less than a predetermined threshold; and determine that it is in the chargeable state when
the upper limit value indicated by the power monitoring device is equal to or higher than
the threshold.
4. The electric vehicle charging system according to claim 3,
wherein the power monitoring device comprises a second current sensor for
measuring the charging current supplied to the electric vehicle from a power distribution
board, and a first current sensor for measuring a total consumed current supplied from a
power grid to the power distribution board; and
wherein the power monitoring device is configured to indicate the upper limit
value to the control means on the basis of the total consumed current measured by the
- 15 -
first current sensor, the charging current measured by the second current sensor, and a
rated current of the power distribution board.