U.S. patent application number 09/883350 was filed with the patent office on 2001-12-20 for automobile and power supply system therefor.
This patent application is currently assigned to Hitachi, Ltd.. Invention is credited to Amano, Masahiko, Masaki, Ryoso, Morooka, Yasuo.
Application Number | 20010052760 09/883350 |
Document ID | / |
Family ID | 18687472 |
Filed Date | 2001-12-20 |
United States Patent
Application |
20010052760 |
Kind Code |
A1 |
Amano, Masahiko ; et
al. |
December 20, 2001 |
Automobile and power supply system therefor
Abstract
In an automobile power supply where plural voltages can be
supplied, a plurality of batteries and a DC/DC converter are
assumed to be unnecessary, and it is possible to operate even when
the controller breaks down. High-voltage terminal 11 and
low-voltage terminal 12 are provided in battery 6. High-voltage FET
4 for controlling the power supply in one direction from
high-voltage terminal 11 to inverter 3 is connected between
inverter 3 and high-voltage terminal 11. Low-voltage FET 5 for
controlling the power supply in one direction from inverter 3 to
low-voltage terminal 12 between inverter 3 and low-voltage terminal
12 is connected.
Inventors: |
Amano, Masahiko;
(Hitachiota, JP) ; Masaki, Ryoso; (Hitachi,
JP) ; Morooka, Yasuo; (Hitachi, JP) |
Correspondence
Address: |
Evanson, McKeown, Edwards & Lenehan P.L.L.C.
Suite 700
1200 G St. N.W.
Washington
DC
20005
US
|
Assignee: |
Hitachi, Ltd.
|
Family ID: |
18687472 |
Appl. No.: |
09/883350 |
Filed: |
June 19, 2001 |
Current U.S.
Class: |
320/163 ;
903/903 |
Current CPC
Class: |
Y02T 10/64 20130101;
B60L 2240/443 20130101; B60L 3/04 20130101; B60L 2240/12 20130101;
F02N 2011/0888 20130101; B60L 7/14 20130101; Y02T 10/72 20130101;
Y02T 10/70 20130101; B60L 58/21 20190201; B60L 58/14 20190201; B60L
2260/26 20130101; B60L 2250/26 20130101; Y02T 10/62 20130101; Y02T
10/7072 20130101; B60L 2210/10 20130101; B60W 10/26 20130101; B60L
50/16 20190201; B60L 2210/30 20130101; H02J 7/1423 20130101; B60L
3/0046 20130101; B60L 58/13 20190201; Y10S 903/903 20130101; B60L
15/2009 20130101; B60L 2240/421 20130101; B60L 2240/441 20130101;
B60K 6/485 20130101; B60L 15/20 20130101; B60L 58/20 20190201; B60L
2240/423 20130101; F02N 11/0866 20130101; B60L 58/15 20190201; B60L
2210/40 20130101; B60L 50/66 20190201; F02N 2011/0896 20130101 |
Class at
Publication: |
320/163 |
International
Class: |
H02J 007/06; H02J
007/24 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 19, 2000 |
JP |
2000-187503 |
Claims
What is claimed is:
1. A power-supply unit for an automobile comprising: a battery
having a high-voltage terminal and a low-voltage terminal; a
converter for converting AC power into DC power; a first switching
element for controlling the power supply in one direction from the
high-voltage terminal of the battery to the converter; and a second
switching element for controlling the power supply in one direction
from the converter to the low-voltage terminal of the battery.
2. The power-supply unit for an automobile according to claim 1,
wherein the switching element which forms said converter and said
first and said second switching element are integrated.
3. The power-supply unit for an automobile according to claim 1,
wherein said first and said second switching element comprise a
field effect transistor (FET) and diodes connected oppositely to
each other, and wherein when the electric current is about to flow
from the source side of said first or second switching element to
its drain side, the gate of the switching element is turned on.
4. The power-supply unit for an automobile according to claim 1,
wherein the voltage of the DC side of said converter is controlled
according to the state of said first and said second switching
element.
5. The power-supply unit for an automobile according to claim 1,
wherein when at least one of said first and the second switching
elements cannot be controlled, the voltage of the DC side of said
converter is controlled according to the direction of the electric
power of said converter.
6. The power-supply unit for an automobile according to claim 1,
wherein said battery comprises a plurality of battery blocks
connected in series.
7. The power-supply unit for an automobile according to claim 1,
further comprising a charging rate measuring means for detecting
the charging rate of the high-voltage terminal side of said battery
and the charging rate of the low-voltage terminal side,
respectively, Wherein said first and said second switching element
are controlled according to the charging rate detected by said
charging rate measuring means.
8. The power-supply unit for an automobile according to claim 1,
wherein when the voltage of the DC side of said converter is
controlled according to the target voltage value at the other
terminal of said battery, the correction is performed according to
the voltage detection value of another terminal of said
battery.
9. An automobile including: a motor/generator; an inverter for
driving said motor/generator; a battery connected to said inverter
through the terminals at a plurality of different voltages; a first
switching element provided between said inverter and a first fixed
terminal of the terminals at a plurality of different voltages of
said battery; a first rectifying device connected in parallel with
the intermittence-switching means provided in said first switching
element, for throwing more electric currents in the direction of
said first terminal from said inverter; a second switching element
provided between said inverter and a second terminal at a voltage
lower than that of said the first terminal of the terminals of a
plurality of different voltages of said battery; a second
rectifying device connected in parallel with the
intermittence-switching means provided in said second switching
element, for throwing more electric currents in the direction of
said second terminal from said inverter; and a battery control unit
for turning on/off said first and said second switching element
according to the state of the charge of said battery.
10. The automobile according to claim 1, wherein said first and
said second switching element are a first and a second field effect
transistor, respectively.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to an automobile which needs a
plurality of different voltages, in order to correspond to the
increase in the consumption of the electric power in an automobile,
and the power-supply unit therefor. Especially, the present
invention relates to a technology suitable to achieve a plurality
of voltage power supply at low-cost.
[0002] To realize an electric operation and a large capacity of
on-board equipment such as electric power steerings and electric
air conditioners provided in automobiles, 42V automobile electric
power supply system in which the 42V-system power supply is added
to the conventional 14V-system power supply is proposed. The
electric current decreases to 1/3 of the conventional current
amount because the voltage increases to three times that of the
conventional power supply in the 42V-system power supply.
Therefore, the decrease in the power loss, the weight saving of the
harness, and the adoption of the high-power load, etc. become
possible.
[0003] However, because making the electric power load like a lamp
system, etc. a 42V-system is difficult, it is expected that two
kinds of voltages of 14V and 42V are used for the present time.
[0004] The system having both of the battery (rated voltage 36V)
for 42V and the battery (rated voltage 12V) for 14V is proposed, in
which the battery for 42V is charged by an alternator and the
battery for 14V through a DC/DC converter.
[0005] Another method is proposed to reduce the cost, in which the
switch switches the output of the alternator to the 42V side or the
14V side, and the DC/DC converter is omitted.
[0006] A further method is proposed, in which two batteries are
connected in series, two kinds of voltage terminals are provided,
and the charge to each battery is switched by switching the
switching element. If this method is applied to 42V power supply,
the battery for 14V need not be separately prepared because the
battery gives the terminal for 14V for 42V. An example of this
method is described in the U.S. Pat. No. 4,686,442.
[0007] A further method is proposed to increase the efficiency of
the alternator and the lifetime of the starter, in which the
function of the starter and the alternator is integrated and the
motor/generator controlled by the inverter is applied to the
42V-power supply.
[0008] There is a problem that the battery cannot be charged at all
when the controller for controlling the switch breaks down, and the
switch cannot be turned on, in the method in which the output of
the alternator is switched to 42V side or 14V side with switch
among the above-mentioned methods. Moreover, it is necessary to
provide the battery for 14V besides the battery for 42V, and thus
the cost rises.
[0009] In the method that two batteries are connected in series,
two kinds of voltage terminals are provided, and the charge to each
battery is switched by switching the switching element, only the
direction of the charge from the alternator is considered in the
configuration of the switching element. Therefore, there is a
problem that it is not possible to apply the method to the
motor/generator in which the function of the starter is integrated,
because the electric current cannot flow into the direction of the
electric discharge.
[0010] In either example, the change in the power-supply voltage
occurred when the switch is changed is not considered.
SUMMARY OF THE INVENTION
[0011] An object of the present invention is to provide an
automobile and the power-supply unit therefor operable even if the
DC/DC converter is not used, a plurality of batteries are not
needed, and the controller for controlling the switch breaks
down.
[0012] Another object of the present invention is to provide an
automobile and the power-supply unit therefor which can control so
that the change in the power-supply voltage may decrease when
switching on/off.
[0013] A power-supply unit of the automobile according to the
present invention includes a battery having a high-voltage terminal
and a low-voltage terminal, a converter for converting AC power
into DC power, a first switching element for controlling the power
supply in one direction from the high-voltage terminal of the
battery to the converter, and a second switching element for
controlling the power supply in one direction from the converter to
the low-voltage terminal of the battery.
[0014] It becomes possible to achieve a power supply system with a
plurality of voltages without using a DC/DC converter by this
configuration.
[0015] Further, because a plurality of voltage terminals are
provided in one battery, it is not necessary to provide a battery
separated for each voltage.
[0016] Preferably, the first and the second switching element of
the present invention comprise a field effect transistor and diodes
connected mutually and oppositely.
[0017] Preferably, the voltage at the DC side of the converter is
controlled to the voltage of the high-voltage terminal side or that
of the low-voltage terminal side according to the on/off state of
the switching element.
[0018] Preferably, even when it becomes impossible to control the
first and the second switching element due to the breakdown of the
controller, the voltage of the DC side of the converter is
controlled according to the direction of the electric power
converted by the converter.
[0019] Even when it becomes impossible to control the switching
elements hereby, the charge to the high-voltage terminal side and
the electrical discharge from the low-voltage terminal side are
always possible due to the operation of the diode connected
mutually and oppositely. Therefore, the automobile can be operated
until the remaining amount of the low-voltage terminal side of the
battery is run out.
[0020] Preferably, the present invention further comprises the
charging rate measuring means for measuring the charging rate at
the high-voltage terminal side of the battery and that at the
low-voltage terminal side, respectively. The first and the second
switching element are controlled according to the measured charging
rate.
[0021] As a result, it is possible to control so as not to cause
the unbalance in the battery charging rate at the high-voltage
terminal side and the low-voltage terminal side, and the
deterioration of the battery performance due to the unbalance of
the charging rate can be prevented.
[0022] Preferably, in the present invention, when the DC voltage is
controlled by the converter, the voltage of another voltage
terminal not controlled is detected directly, and the voltage
control system is corrected.
[0023] As a result, it becomes possible to control so that the
terminal voltage does not greatly change even when the switching
element is switched.
[0024] An automobile of the present invention has a
motor/generator; an inverter for driving said motor/generator; a
battery connected to said inverter through the terminals at a
plurality of different voltages; a first switching element provided
between said inverter and a first fixed terminal of the terminals
at a plurality of different voltages of said battery; a first
rectifying device connected in parallel with the
intermittence-switching means provided in said first switching
element, for throwing more electric currents in the direction of
said first terminal from said inverter; a second switching element
provided between said inverter and a second terminal at a voltage
lower than that of said the first terminal of the terminals of a
plurality of different voltages of said battery; a second
rectifying device connected in parallel with the
intermittence-switching means provided in said second switching
element, for throwing more electric currents in the direction of
said second terminal from said inverter; and a battery control unit
for turning on/off said first and said second switching element
according to the state of the charge of said battery.
[0025] Further, in the automobile of the present invention, said
first switching element and said first rectifier, and said second
switching element and said second rectifier are a first and a
second field effect transistor, respectively.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] FIG. 1 shows the configuration of an automobile power-supply
unit according to one embodiment of the present invention.
[0027] FIG. 2 shows the configuration of the battery control unit 7
of FIG. 1.
[0028] FIG. 3 shows the processing flow of the engine start-up
control unit 51 of FIG. 2.
[0029] FIG. 4 shows the processing flow of the charge control unit
52 of FIG. 2.
[0030] FIG. 5 shows the control block illustrating the method of
operating the torque instruction in the charge control unit 52 of
FIG. 2.
[0031] FIG. 6 shows the control block of motor control unit 7 of
FIG. 1.
[0032] FIG. 7 shows the configuration of the automobile
power-supply unit with three voltages according to one embodiment
of the present invention.
[0033] FIG. 8 shows an example of the automobile equipped with the
device of FIG. 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0034] Hereinafter, the embodiments of the present invention will
be explained referring to the drawings.
[0035] FIG. 1 shows an example of the configuration of the
automobile power supply in which two voltage systems of 42V-system
and 14V-system are provided. The start-up and the power generation
of engine 1 is performed by motor/generator 2 connected on a
rotation axis of the engine 1. The driving force and the generated
output of motor/generator 2 are controlled by inverter 3. When the
engine is started up, the DC voltage of the battery 6 is converted
into an AC voltage with inverter 3. As a result, the engine 1 is
rotated by the driving torque generated by the motor/generator 2
After the engine 1 is started up, an AC voltage is generated in the
motor/generator 2 by the rotation of the engine. This AC voltage is
converted into the DC voltage by inverter 3, and is charged in the
battery 6.
[0036] The battery 6 has a high-voltage terminal 11 and a ground
terminal 13 for 42V (rated voltage 36V). Further, it also has a
low-voltage terminal 12 to supply the electric power to a
14V-system load. It should be noted that the battery can be either
of integrated type or separated type in which three battery blocks
for 14V (rated voltage 12V) are connected in series. In the
configuration in which three battery blocks are connected in
series, there are advantages in that it is possible to replace the
order of connection in a certain period of time, or to exchange
every block. In addition, it is possible to combine the battery for
28V(rated voltage 24V) with the battery for 14V.
[0037] A plurality of 42V-system loads 21 of the comparatively
high-power such as an electric power steering and an electric air
conditioner are connected to the high-voltage terminal 11 for 42V.
To the low-voltage terminal 12 for 14V, 14V-system loads 22 such as
lamps and various controllers, that low voltage is advantageous,
are connected. Moreover, because the voltage between the
high-voltage terminal 11 and the low-voltage terminal 12 becomes
28V, it is also possible to connect loads for 28V between these two
terminals.
[0038] The connection between the inverter 3 and the battery 6 is
performed as follows. First of all, the negative electrode side of
the inverter 3 is connected to the ground terminal 13 of the
battery 6. The high-voltage FET (field effect transistor) 4 or the
first switching element is connected between the high-voltage
terminals 11 of the battery 6 and the positive electrode of the
inverter 3, and the low-voltage FET (field effect transistor) 5 or
the second switching element is connected between the low-voltage
terminals 12 of the battery 6 and the positive electrode of the
inverter 3. The source of the high-voltage FET 4 is connected to
high-voltage terminal 11, and the drain is connected to inverter 3.
Even if the switch is off, the electric current from the inverter 3
to the high-voltage terminal 11 can be allowed by the
inverse-connection diodes (rectifier) provided in the high-voltage
FET 4. The source of the low-voltage FET 5 is connected to the
positive electrode of the inverter 3, and the drain is connected to
the low-voltage terminal 12. Even if the switch is off, the
electric current from the low-voltage terminal 12 of the battery 6
to the inverter 3 can be allowed by the diode provided in the
low-voltage FET 5.
[0039] Namely, the high-voltage FET 4 acts as a switching element
to control the power supply in one direction of the inverter 3 from
the high-voltage terminal 11 of battery 6. Further, the low-voltage
FET 5 acts as a switching element to control the power supply in
one direction of the low-voltage terminal 12 of the battery 6 from
the inverter 3. These FETs comprise an intermittence-switching
means for switching on/off the internal circuit and a rectifying
device provided in parallel with the intermittence-switching
means.
[0040] The integrated control unit 9 provides operation mode
instructions of engine start-up, charge, assist, and regeneration,
etc. to battery control unit 7, based on driver's key switch
operation, accelerator operation, brake operation, and battery
charging rate, etc. Further, the integrated control unit 9 provides
a torque instruction .tau.o indicative of the torque to be output
by the motor/generator 2.
[0041] Battery control unit 7 controls the high-voltage FET 4 and
the low-voltage FET 5 which are the switching element according to
the state of the charge of the battery 6. Here, the switching is
performed by operating the voltage of the gates of the high-voltage
FET 4 and the low-voltage FET 5. Moreover, the voltage selection
signal is given to motor control unit 8 corresponding in the state
of the switch. The driving torque or the power generation torque to
be generated by motor/generator 2 is determined based on the
instruction from integrated control unit 9, and a torque
instruction .tau.m is given to the motor control unit 8. In
addition, an operation confirmation signal indicative whether the
battery control unit 7 operates normally.
[0042] The motor control unit 8 outputs PWM signals Pu, Pv, and Pw
to the inverter 3 based on the voltage selection signal, the torque
instruction and the crank angle signal .theta.c of the engine 1
from the battery control unit 7. Moreover, the motor control unit 8
inputs the operation confirmation signal from the battery control
unit 7. If the battery control unit 7 does not operate normally,
special processing in abnormal circumstances is performed.
[0043] An example of the automobile installing the device of FIG. 1
is shown in FIG. 8.
[0044] In FIG. 8, the motor/generator 2 is installed outside of
engine 1 in the horizontal putting method. Namely, belt 81 is
bridged between the motor/generator 2 and the pulley 103 of a
crankshaft, and, as a result, the driving force is bidirectionally
transferred between the engine 1 and the motor/generator 2. The
arrangement of the motor/generator 2 can be properly changed
according to the convenience of the arrangement of engine 1, and
the arrangement of the motor/generator 2 is not limited whether it
is put longitudinally or horizontally.
[0045] Although the equipment and units, etc. such as battery 6,
inverter 3, battery control unit 7, motor control units 8 and
integrated control unit 9 other than the motor/generator 2 are
arranged in engine rooms 10, it is also possible to properly change
the arrangement according to the convenience of the arrangement of
the vehicle-relevant equipment (not shown in the figure), and to
arrange in the place other than the engine room 105. Further,
although the battery control unit 7, the motor control unit 8, and
the integrated control unit 9 are shown in the figure as one
housing, it is also possible to arrange them in another housing,
and to put the inverter 3 into the same housing as one for other
controllers.
[0046] In this embodiment, the engine 101 and the motor/generator 2
are mechanically connected via the belt 81, however, the
configuration in which the crankshaft 102 of the engine 101 and the
motor/generator 2 are connected directly for instance, is
acceptable. Further, it is needless to say that various connected
configurations can be adopted.
[0047] Hereinafter, the configuration and the operation of the
battery control unit 7 will be explained in detail.
[0048] FIG. 2 shows the configuration of the battery control unit
7. First of all, high-voltage side charging rate measuring part 54
measures the charging rate of a high-voltage side battery based on
the output of the electric current measuring means 14 and the
voltage measuring means 16. Similarly, low-voltage side charging
rate measuring part 55 measures the charging rate of a low-voltage
side battery based on the output of the electric current measuring
means 14, 15 and the voltage measuring means 17. The charging rate
of the high-voltage side battery is output to the integrated
control unit 9. The high-voltage side battery indicates the battery
block between the high-voltage terminal 11 and the low-voltage
terminal 12, and the low-voltage side battery indicates the battery
block between the low-voltage terminal 12 and the ground terminal
13.
[0049] Although there are various methods as a method of measuring
charging rate, the method of obtaining the charging rate according
to the predetermined characteristic data is adopted in this
embodiment, based on the integrated value of the electric current
which flows to the battery, and the voltage and the current value.
Because there is a suitable measurement means by the kind of the
battery such as lead, nickel hydrogen, and the lithium ion, it is,
therefore, preferable to use them properly.
[0050] It should be noted that the electric current which flows to
the low voltage battery is equal to the total value of the electric
current of electric current measuring means 14 at 42V side and the
electric current measuring means 15 at 14V side.
[0051] An actual control is performed based on the charging rate
and the voltage measured value of the battery obtained in the
above-mentioned method. Either of the engine start-up control unit
51, the charge control unit 52, and the regenerative assist control
unit 53 operates according to an operation mode output by the
integrated control unit 9, and outputs a control signal.
[0052] First, the case of the engine start-up will be explained.
The engine start-up control unit 51 operates and starts to control
when the engine start-up instruction is output as an operation mode
signal from the integrated control unit 9 based on driver's key
switch operation. In an automobile having an idling stop function,
the engine start-up instruction is output based on the shift
operation, the brake operation, and the accelerator operation, etc.
besides the key switch operation.
[0053] FIG. 3 shows a processing flow of engine start-up control
unit. It is examined first whether it is possible to start up the
engine by using the high voltage battery (step 101). it is judged
whether it is possible to start up the engine, based on whether the
charging rate measured by the high-voltage side charging rate
measuring part 55 is more than a predetermined value, or whether
the voltage value of the high voltage system (42V-system) is more
than a predetermined value. Even if the battery charging rate is
small, and it is judged that start-up is possible by a so-called
jump-start in the case that the voltage is more than the
predetermined value by connecting the battery of another
automobile. The processing advances to steps 103-105 if the
start-up is possible. The low-voltage FET 5 is turned off and the
high-voltage FET 4 is turned on. And the voltage selection signal
indicative of the selection of 42V is output.
[0054] The processing advances to step 102 if it is impossible to
judge that the start-up by the high-voltage battery is possible. In
the step, it is judged whether it is possible to start up the
engine, based on whether the charging rate of the low-voltage
battery is more than a predetermined value, or whether the voltage
value of the low voltage system (14V-system) is more than a
predetermined value, in the same way as step 101. If the start-up
is possible, the processing advances to steps 106-108. The
high-voltage FET 5 is turned off and the low-voltage FET 4 is
turned on. And the voltage selection signal indicative of the
selection of 42V is output.
[0055] The processing advances to step 103 if it can not be
determined that the start-up by the low voltage battery is
possible. In the step, the start-up by the high voltage battery is
tested in this example. If it is desirable to avoid the battery
overdischarge, it may give up the start-up of the engine with
indicating the incapability of the engine start-up, and may adopt
the method of urging the jump start with the battery of another
automobile.
[0056] The processing advances to step 109 when the voltage
selection signal is output, and the torque instruction is output in
the step. Instruction .tau.o output by the integrated control unit
9 is used as it is for the start-up of the engine as torque
instruction value .tau.m. Finally, the operation confirmation
signal indicative of whether the battery control unit operates
normally is output (step 110).
[0057] According to this embodiment, there is a feature that the
engine start-up can surely be done because the voltage is switched
judging whether the start-up becomes possible by using which
voltage. Further, there are effects that the start-up is possible
by using either voltage of 42V and 14V, and the judgement of the
voltage can be automatically executed, with regard to the jump
start by the battery of another automobile.
[0058] Next, the case that the engine 1 is started and the battery
is charged by the motor/generator 2, will be explained. After it is
confirmed that the engine is turned over, the charge instruction is
output as an operation mode signal by the integrated control unit
9. In the automobile with the regenerative braking function, it is
not possible to regenerate when the charging rate of the battery
becomes 100%. Therefore, the charging instruction is output in
consideration of the charging rate information in order to keep the
carging rate about 90% or less for instance.
[0059] In the battery control unit 7, the charge control unit 52
operates and the charge is controlled according to the flow shown
in FIG. 4. When charging the battery, it is necessary to control
the high-voltage FET 4 and the low-voltage FET 5 so as not to cause
a big unbalance in the charging rate of a high-voltage side battery
and a low-voltage side battery. Here, the difference between the
charging rate of a high-voltage side battery and the charging rate
of a low-voltage side battery is assumed to be .DELTA.SOC. This
.DELTA.SOC is adjusted between .+-.5%.
[0060] It is checked whether .DELTA.SOC is smaller than -5% in step
201. If so, the low-voltage FET 5 is turned off and the
high-voltage FET 4 is turned on, and thus the inverter 3 is
connected to 42V-system so that the charging rate of the
high-voltage side battery may increase (steps 204-205). A signal
indicative of the selection of 42V is output as a voltage selection
signal in step 206. Then, the processeing advances to step 209. If
.DELTA.SOC is -5% or more, the processign advances to step 202. In
the step, it is checked whether .DELTA.SOC is larger than +5%. If
larger than +5%, the low-voltage FET 5 is turned on and the
high-voltage FET 4 is turned off, and thus the inverter 3 is
connected to 14V-system so that the charging rate of the
low-voltage side battery may increase. Then 14V is output as a
voltage selection signal (step 206-208), and the processing
advances to step 209. If .DELTA.SOC is +5% or less, the switch is
not changed and the processing advances to step 209. In step 209,
the charge torque to be generated by the motor/generator 2 is
calculated. The calculated torque is output in step 210. Finally,
the operation confirmation signal is output in step 211.
[0061] According to the above-mentioned method, the deterioration
of the battery performance by the unbalance of the charging rate
between the battery blocks is prevented because the difference of
the charging rate of the high-voltage side battery and the
low-voltage side battery is always controlled to become a
predetermined value or less.
[0062] There is a method of changing the switch in consideration of
not only .DELTA.SOC but also engine speed. Because the induced
voltage of the motor/generator 2 increases when the engine speed is
high, the inverter is connected to 42V-system. Oppositely, when the
engine speed is low, the inverter is connected to 14V-system. As a
result, there is an effect that the efficiency of the generation
can be able to be improved because the voltage suitable for the
induced voltage of the motor is selected.
[0063] Although .DELTA.SOC was controlled so as to fall within the
predetermined range in the flow of FIG. 4, it is also possible to
control to keep .DELTA.SOC almost 0 by switching over more
frequently. For instance, the on/off switch of the high-voltage FET
4 and the low-voltage FET 5 is made to be performed without fail
for the cycle or 10 Ms, and the period when high-voltage FET 4
turns on is changed according to .DELTA.SOC. If .DELTA.SOC is
positive, the period when high-voltage FET 14 turns on is
lengthened, and If .DELTA.SOC is negative, the period when the
high-voltage FET 4 turns on is shortened oppositely. The control by
which .DELTA.SOC is kept almost 0 always becomes possible by
adjusting the degree (gain) by which the period is changed.
[0064] In step 209, the power generation torque to be output the
motor/generator 2 is calculated. A method of maintaining a target
value the DC voltage will be explained with reference to FIG.
5.
[0065] For instance, when the inverter is connected to the
42V-system, the charge torque is calculated based on the difference
between the voltage target value and the voltage measured value of
42V-system. If the voltage measured value is lower than the voltage
target value, the charging torque is increased. As a result, the
charging current which flows to the battery is increased, and the
voltage of 42V-system increases. For instance, the
proportional-plus-integral control (PI control) can be used as a
control method. In that case, the difference between the voltage
target value and the voltage measured value of 14V-system is
calculated, the correction gain is multiplied, and the product is
added to the voltage target value of 42V-system. It is important to
control so that the voltage should not change when switching over,
because the load in which the change in voltage is undesirable like
the lamp load etc. is connected to 14V-system. It is possible to
control to keep the voltage of 14V-system in the neighborhood of
the target value even when the inverter is connected to 42V-system
by using the method shown in FIG. 5.
[0066] Next, The case in which the regenerative braking or the
engine assistance is instructed as an operation mode will be
explained. In this case, the regenerative assist control part 53 is
operated, and the control is executed. The possibility that the
electric power that both the regenerative braking and the engine
assist charges or discharges a big power into or from the battery
is high. Therefore, the low-voltage switch 5 is basically turned
off and the high-voltage switch 4 is turned on, and the inverter is
connected to the high-voltage side. Torque instruction value .tau.o
output by the integrated control unit 9 is output as it is as a
torque instruction.
[0067] The same processing step as steps 103-105 and steps 109-110
of FIG. 3 is performed.
[0068] Next, the operation of the motor control unit 8 will be
explained.
[0069] FIG. 6 shows the control block, in which the induction
machine is used as the motor/generator 2. First of all, slipping
angular frequency .omega.s of the motor/generator 2 is determined
by the slip control part 35 based on the torque instruction value
.tau.m output by the battery control unit 7. Not .tau.m but torque
instruction value .tau.o output by integrated control unit 9 is
used, when judged that the battery control unit is abnormal based
on the operation confirmation signal from the battery control unit
7. In speed sensing unit 34, the motor speed .omega.m is calculated
from the crank angle .theta.c of engine 1. It is not necessary to
use the dedicated rotation sensor by detecting speed .omega.m of
the motor by using crank angle .theta.c, because the
motor/generator 2 is directly connected to the engine 1. Next,
primary angular frequency .omega.1 of inverter 3 is calculated
based on the sum of the speed .omega.m and slipping angular
frequency Cs. Moreover, the primary voltage V1 is calculated from
the primary angular frequency .omega.1 so that the electric current
which flows to motor/generator 2 may almost become constant. This
is a method referred generally as the V/f control, in which the
value of V1/.omega.1 is controlled to be constant, or becomes a
fixed function. This calculation is carried out in the V/f control
unit 36. The voltage instruction Vu, Vv, and Vw of respective phase
are calculated from primary voltage V1 and primary angular
frequency .omega.1 by the voltage calculating part 37. Next, these
signals are converted into PWM signal Pu, Pv, and Pw in the PWM
control unit 38 so that the voltage of motor/generator 2 may become
voltage instruction Vu, Vv, and Vw, and are output to the inverter
3. Because the DC voltage of inverter 3 is decided depending on the
voltage of the connected battery, the PWM signal is calculated by
inputting the voltage selection signal obtained in processing part
39.
[0070] When the abnormality is not found in the operation
confirmation signal of the battery control unit 7, the processing
part 39 outputs the voltage selection signal as it is. The
following processing is performed when judged that the abnormality
is found by operation confirmation signal in the battery control
unit 7. Whether it is a state that the charge is demanded or a
state that the engine start-up is demanded is judged from the sign
of the torque instruction value .tau.o output by the integrated
control unit 9. It is judged that it is in the state of the engine
start-up if .tau.o is positive, and the voltage selection signal is
output to the PWM control unit 38 as low voltage (14V). It is
judged that it is in the state of the charge if .tau.o is negative,
and the voltage selection signal is output as high voltage (42V).
Even when the battery control unit 7 breaks down by the control
like this, the engine start-up from the low-voltage terminal 12 and
the charge to the high-voltage terminal 11 become possible
respectively through the inverse-connection diodes provided in the
low-voltage FET and the high-voltage FET. In a word, the
reliability of the automobile electrical power system having a
plurality of voltages is improved, because it become possible to
perform the charge and the engine start-up not possible to do with
the conventional switch when the battery control unit breaks down.
Especially, it is useful to perform the charge to the high-voltage
side even if the battery control unit breaks down, because an
on-board equipment which needs the high-power is connected to the
high-voltage terminal side.
[0071] Although the case with induction machine being used as the
motor/generator 2 is described in the above, the present invention
can be applied to the case with synchronous machine being used.
[0072] Well, although the inverter 3, the high-voltage FET 4, and
the low-voltage FET 5 are assumed to be a separate component in the
configuration of FIG. 1, it is also possible to mount as one module
bringing these three components together. It is possible to make an
integrated module by installing two power MOSFET chips for changing
the voltage and six power MOSFET chips for the inverter in the same
module. Therefore, making space-saving, the miniaturization, and
making low-cost are achieved. Further, because it is possible to
observe and control all power MOS FET chips with same IC if a
control IC is installed in the module, the control with high
accuracy can be performed and the cost can be decreased.
[0073] Next, an example of applying the present invention to the
automobile power supply having three kinds of voltages will be
explained with reference to FIG. 7. The battery 6 has medium
voltage terminal 62 for 28V besides the high-voltage terminal 11
for 42V, low-voltage terminal 12 for 14V, and the ground terminal
13. 28V-system load 63 is connected to medium voltage terminal 62.
The high-voltage terminal 11 is connected to a positive pole of
inverter 3 through high-voltage FET 4, and the low-voltage terminal
12 is connected to a positive pole of inverter 3 through
low-voltage FET 5. The medium voltage terminal 62 is connected to a
positive pole of the inverter through medium voltage FET 61a and
62b. The medium voltage FET 61a and 62b are connected mutually in
series with reversing the polarity of the diode. The purpose of
this is to prevent from entering the state of the short-circuit
through the diode when the high-voltage FET 4 or the low-voltage
FET 5 turns on.
[0074] The present invention is applicable to the power supply with
three kinds of voltages by the above-mentioned configuration.
Although the detection system and the control system of the
electric current and the voltage are omitted in FIG. 7, the same
configuration and control method as FIG. 1 can be applied.
[0075] Further, although the high voltage was explained as 42V in
FIG. 7, it is possible to compose in the same way even if it is the
voltage of 100V or more, applied to a hybrid automobile. In that
case, the drive motor, the equipment for 42V and the equipment for
12V of a hybrid automobile can be driven by one battery. Moreover,
the DC/DC converter need not be provided. Therefore, the cost is
reduced.
[0076] According to the above-mentioned embodiment, neither a DC/DC
converter nor a plurality of batteries are needed in the automobile
power-supply unit which can supply a plurality of voltages.
Further, the start-up of the engine and the charge of the battery
can be performed even if the controller for controlling the switch
which switches the voltage breaks down. Moreover, the change in the
power-supply voltage when switching over can be suppressed.
* * * * *