U.S. patent application number 11/297490 was filed with the patent office on 2006-04-27 for electric drive system for vehicle, electric control system for vehicle, electric drive method for vehicle.
Invention is credited to Kazuhiro Imaie, Yasuhiro Kiyofuji, Shintarou Oku, Keizo Shimada, Naoshi Sugawara, Takashi Yagyu.
Application Number | 20060086547 11/297490 |
Document ID | / |
Family ID | 36205163 |
Filed Date | 2006-04-27 |
United States Patent
Application |
20060086547 |
Kind Code |
A1 |
Shimada; Keizo ; et
al. |
April 27, 2006 |
Electric drive system for vehicle, electric control system for
vehicle, electric drive method for vehicle
Abstract
In an electric drive system for a vehicle, an alternator is
driven by an engine to generate electric power which is used to
drive a motor to generate a driving force. During a retardation of
the vehicle, the motor is operated as an alternator to convert
kinetic energy to electric energy which is used to retard the
vehicle. A retard resistor is provided for absorbing electric
energy generated during the retardation state. The retard resistor
is cooled down by an AC blower.
Inventors: |
Shimada; Keizo; (Hitachi,
JP) ; Kiyofuji; Yasuhiro; (Hitachi, JP) ;
Sugawara; Naoshi; (Hitachi, JP) ; Imaie;
Kazuhiro; (Hitachi, JP) ; Oku; Shintarou;
(Hitachi, JP) ; Yagyu; Takashi; (Ushiku,
JP) |
Correspondence
Address: |
ANTONELLI, TERRY, STOUT & KRAUS, LLP
1300 NORTH SEVENTEENTH STREET
SUITE 1800
ARLINGTON
VA
22209-3873
US
|
Family ID: |
36205163 |
Appl. No.: |
11/297490 |
Filed: |
December 9, 2005 |
Current U.S.
Class: |
180/65.245 ;
180/65.265 |
Current CPC
Class: |
Y10S 903/947 20130101;
Y02T 10/72 20130101; B60L 7/22 20130101; Y02T 10/70 20130101; B60L
2210/20 20130101; Y02T 10/7072 20130101; Y02T 10/62 20130101; B60L
50/61 20190201 |
Class at
Publication: |
180/065.4 |
International
Class: |
B60K 1/00 20060101
B60K001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 12, 2004 |
JP |
2004-358752 |
Claims
1. An electric drive system for a vehicle, comprising: an
alternator driven by power of an engine of said vehicle to generate
electric power; a rectifier for rectifying the electric power
outputted by said alternator; a converter for converting an output
of said rectifier to an alternating current; a motor driven by an
output of said converter and rotated by wheels of said vehicle
mechanically coupled to said motor to generate electric power; a
resistor for converting the electric power generated by said motor
to thermal energy; and a blower for cooling said resistor.
2. An electric drive system for a vehicle according to claim 1,
further comprising a second alternator driven by the power of said
engine to generate electric power, wherein said blower is driven by
electric power generated by said second alternator.
3. An electric drive system for a vehicle according to claim 2,
further comprising a second converter for converting the output of
said second alternator, wherein said second converter has an output
connected to said blower.
4. An electric drive system for a vehicle according to claim 2,
wherein said second alternator is controlled to generate a constant
voltage independently of an engine rotation speed.
5. An electric drive system for a vehicle according to claim 2,
wherein said alternator and said second alternator are coaxially
connected to an output shaft of said engine.
6. An electric drive system for a vehicle according to claim 1,
further comprising a transformer for transforming the output of
said alternator, wherein said blower is driven by an output of said
transformer.
7. An electric drive system for a vehicle according to claim 6,
further comprising a second converter for converting the output of
said transformer, wherein said second converter has an output
connected to said blower.
8. An electric drive system for a vehicle according to claim 6,
further comprising a switch for connecting the output of said
transformer to said blower.
9. An electric drive system for a vehicle according to claim 1,
wherein a driving force is provided for said wheels by connecting a
rotating force of said motor to said wheels through gears, or
directly connecting to said wheels.
10. An electric drive system for a vehicle according to claim 1,
wherein said motor is connected to said resistor through said
switch when said motor is driven by said wheels to generate
electric power.
11. An electric drive system for a vehicle according to claim 1,
further comprising a second motor for cooling down said resistor,
said second motor being driven with the electric power generated by
said motor.
12. An electric drive system for a vehicle according to claim 1,
wherein said system determines whether or not said vehicle is in
retard, and cools said resistor when said vehicle is in retard.
13. An electric drive system for a vehicle according to claim 12,
wherein said system determines whether or not said resistor is
cooled down, and determines whether or not said vehicle is in
retard after waiting for a predetermined time when said resistor is
cooled down.
14. An electric drive system for a vehicle according to claim 13,
wherein said system determines whether or not said vehicle is in
acceleration, and determines whether or not said vehicle is in
retard when said vehicle is in acceleration.
15. An electric control system for a vehicle for controlling
electric power generated by an alternator driven by power of an
engine, and controlling a conversion of a rectified version of the
electric power output, wherein a torque of wheels driven by a motor
is controlled by the converted electric power by controlling the
conversion of the electric power, said motor is controlled to
generate electric power which acts as a mechanical load on
rotations of the wheels, and said system controls to cool down
thermal energy generated by electric power generated by said
motor.
16. An electric drive method for a vehicle comprising the steps of:
rectifying electric power generated by an alternator driven by an
engine; converting the rectified output to an alternate current by
a converter; driving a motor with the converted output to rotate
wheels; driving said motor to generate electric power which acts as
a mechanical load on rotations of the wheels; and converting the
electric power generated by said motor to thermal energy to
dissipate the heat.
17. An electric drive system according to claim 1, further
comprising wheels mechanically coupled to said motor.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to an electric drive system
for a vehicle, an electric control system for a vehicle, and an
electric drive method for a vehicle.
[0002] For electrically driving a vehicle, an engine is used to
generate power with which an alternator is driven to generate
electric power which is used to drive a motor for moving the
vehicle. Specifically, the alternator is driven by the engine to
generate electric power which is then converted to a direct current
(DC) by a rectifier, and the DC power is supplied to an inverter.
Further, the DC input is converted to an alternate current (AC)
output by the inverter, an AC motor is driven with the AC output to
rotate wheels through gears, thus driving a vehicle to move.
[0003] For retarding a vehicle, the AC motor is operated as an
alternator, while the inverter is operated as a converter to
convert AC power to DC power. Such a technique is described, for
example, in JP-A-2000-224709.
SUMMARY OF THE INVENTION
[0004] However, the prior art described above publication
difficulties in absorbing energy generated during a retardation of
the vehicle as the energy generated during the retardation becomes
larger when the vehicle continuously runs down a long downhill.
[0005] It is an object of the present invention to provide an
electric driving system for a vehicle, an electric control system
for a vehicle, and an electric drive method for a vehicle which are
capable of efficiently absorbing energy generated during a
retardation, even if the energy generated during the retardation of
vehicle is increased, for example, due to a vehicle continuously
running down a long downhill road, or due to a comparative heavy
vehicle.
[0006] To achieve the above object, in the present invention, an
electric motor is driven to generate electric power which acts as a
mechanical load on rotations of wheels. The electric power
generated by the motor is converted to thermal energy by a
resistor.
[0007] More specifically, a forced air-cooled retard resistor is
provided for absorbing electric power resulting from a retardation.
Also, an auxiliary alternator is provided coaxially with a main
alternator, and an inverter associated with a blower is operated
with the output of the auxiliary alternator to drive the blower for
cooling down the retard resistor.
[0008] According to the present invention, since the energy
generated during a retardation is converted to thermal energy which
is discharged to the air by cooling, the present invention is
effective particularly when the retardation is continuously
applied, and can improve the driving efficiency.
[0009] Other objects, features and advantages of the invention will
become apparent from the following description of the embodiments
of the invention taken in conjunction with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a block diagram illustrating an electric drive
system for a vehicle according to one embodiment of the present
invention;
[0011] FIG. 2 is a block diagram illustrating another embodiment of
the electric drive system for a vehicle using a DC blower in the
present invention;
[0012] FIG. 3 is block diagram illustrating a further embodiment of
the electric drive system for a vehicle using a transformer in
place of an auxiliary alternator in the present invention;
[0013] FIG. 4 is a block diagram illustrating a yet further
embodiment of the electric drive system for a vehicle illustrated
in FIG. 3, in which a contactor is substituted for an inverter
associated with the blower in the present invention;
[0014] FIG. 5 represents exemplary structures of a main alternator
and an auxiliary alternator in the embodiment illustrated in FIG.
1;
[0015] FIGS. 6A and 6B represent one embodiment of method of
controlling an AC blower, where FIG. 6A is a timing chart, and FIG.
6B is a flow chart illustrating the flow of operations in the
control method;
[0016] FIGS. 7A and 7B represent another embodiment of the method
of controlling an AC blower, showing that the AC blower is operated
after a retard as well, where FIG. 7A is a timing chart, and FIG.
7B is a flow chart illustrating the flow of operations in the
control method; and
[0017] FIGS. 8A and 8B represent a further embodiment of the method
of controlling an AC blower, showing that the AC blower is operated
before a retard as well, where FIG. 8A is a timing chart, and FIG.
8B is a flow chart illustrating the flow of operations in the
control method.
DESCRIPTION OF THE INVENTION
[0018] In the following, several embodiments of the present
invention will be described with reference to the accompanying
drawings.
[0019] Describing in brief the configuration of an electric drive
system for a vehicle according to a first embodiment, the electric
drive system comprises a blower for cooling down a retard resistor
in this embodiment. The blower is driven by an associated inverter
which is powered by an auxiliary alternator coaxial with a main
alternator. Also, the auxiliary alternator is controlled to
generate a constant output voltage irrespective of the engine
rotation speed, so that the retard resistor can be cooled down
under an optimal cooling condition, irrespective of the engine
rotation speed and conditions under which the main alternator
generates the electric power.
[0020] Describing specifically with reference to FIG. 1, the main
alternator 2 and auxiliary alternator 3 are driven by the engine 1.
The output of the main alternator 2 is converted to a direct
current (DC) by a rectifier 4, and the DC power is applied to an
inverter 6. The inverter 6 converts the DC power to alternating
current (AC) power for driving an AC motor 7. The output of the AC
motor 7 is transmitted to wheels 11 to move the vehicle. On the
other hand, during a retardation, the AC motor 7 is driven to act
as an alternator. The inverter 6 is operated as a converter to
convert AC power to DC power, and a switch 8 is turned on such that
the DC power is consumed by a retard resistor 9. In other words,
kinetic energy is converted to thermal energy to retard the
vehicle. Also, the output of the auxiliary alternator 3 is used to
operate an AC blower 13 through an inverter 12. The aforementioned
retard resistor 9 is cooled down by the AC blower 13.
[0021] As illustrated in FIG. 5, the main alternator 2 and
auxiliary alternator 3 can be integrated for reduction in size by
arranging a rotor 24 of the main alternator and a rotor 27 of the
auxiliary alternator on a single shaft 21, and placing a stator 26
of the main alternator and a stator 29 of the auxiliary alternator
within a single case 23. Also, since the two alternators are
electrically independent of each other, the main alternator 2
having a larger capacity can generate a higher voltage, while the
auxiliary alternator 3 having a smaller capacity can generate a
lower voltage. As a result, general-purpose products of low voltage
insulation type can be used for the inverter 12 and associated AC
blower 13.
[0022] Describing how to control the engine 1 and main alternator
2, a controller 51 obtains an accelerator position signal from an
accelerator position sensor 61 and a retarding signal from a
retarding detection sensor 62 thereby to produce control signals
for controlling the engine 1, the main alternator 2, the auxiliary
alternator 3, the rectifier 4, the inverter 6, the AC motor 7, and
the switch 8 as shown in the dotted lines. In particular, a target
rotation speed of the engine 1 and a target voltage of the main
alternator 2 are calculated in accordance with the position of an
accelerator, and the output frequency of the inverter 6 (or the AC
motor 7). The engine 1 is supplied with a fuel such that the engine
1 reaches the target rotation speed. Also, an excitation current of
the main alternator 2 is controlled such that the main alternator 2
outputs the target voltage. In other words, the rotation speed and
alternator output voltage are controlled such that the engine 1 and
main alternator 2 are driven under optimal conditions. For example,
when a maximum driving force is required for the vehicle, the
engine 1 is driven to reach its maximum rotation speed, and the
exciting current of the alternator 2 is controlled to increase the
output voltage of the alternator 2 to its maximum voltage.
Conversely, when no driving force is required, the engine 1 is
driven to reach its minimum speed, and the exciting current of the
alternator 2 is controlled to reduce the output voltage of the
alternator 2 to its minimum voltage.
[0023] The auxiliary alternator 3 in turn controls the exciting
current such that the auxiliary alternator 3 generates a constant
output voltage even though the engine 1 varies in the rotation
speed. In this way, a retardation system can be operated regardless
of the state of the driving system. For example, when the retarding
pedal is depressed at the vehicle running with the maximum rotation
speed of the engine, the engine speed may vary from the maximum
speed to the minimum speed. At this time, the auxiliary alternator
3 is controlled to maintain the output voltage constant, and the
output frequency of the inverter 12 is controlled to be constant,
so that the blower 13 can make a stable cooling operation. Also, in
the present invention, a constant low AC voltage can be generated
from the output of the auxiliary alternator 3 irrespective of
whichever state of the system. This can be utilized when an
auxiliary power supply is required, such as a power supply for an
in-board heater. Another advantage of this embodiment is that an
effective auxiliary power supply is provided. Also, since an AC
motor can be used for a motor associated with the blower for
cooling the retard resistor 9, the maintenance can be facilitated
for the blower, which is another advantage of the embodiment. On
the other hand, the inverter 6 is controlled to reach a target
torque by calculating a torque current instruction value, an
exciting current instruction value, and a rotation speed
instruction value based on the motor current and rotation speed of
the AC motor 7.
[0024] FIG. 2 illustrates another embodiment of the present
invention. The following description will be given of parts
different from those in the embodiment illustrated in FIG. 1. Since
the remaining parts are the same as those in the embodiment
illustrated in FIG. 1 in principle, no description will be given of
these parts. The auxiliary alternator 3 and inverter 12 associated
with the blower 13 are removed, and the AC blower 13 is replaced
with a DC blower 14. The DC blower 14 is powered from an
intermediate tap of the retard resistor 9. Since the auxiliary
alternator and inverter associated with the blower can be omitted
from the embodiment of FIG. 1, the resulting circuit can be
simplified. Also, as the switch 8 is turned on to apply a voltage
across the retard resistor 9, the DC blower 14 automatically
rotates. On the other hand, as the switch 8 is turned off to stop
applying a voltage across the retard resistor 9, the DC blower 14
automatically stops. Therefore, the blower 14 is controlled in
response to the control on the switch 8, so that the control can be
simplified as well.
[0025] FIG. 3 illustrates a further embodiment of the present
invention. The following description will be given of parts
different from the foregoing embodiments. The remaining parts are
the same. As opposed to the embodiment of FIG. 1, the inverter 12
associated with the blower 13 is powered from the output of the
main alternator 2 through a transformer 15, rather than the
auxiliary alternator 3. Since the auxiliary alternator 3 can be
omitted from the embodiment of FIG. 1, the cost can be reduced.
Since variations in the output voltage of the main alternator
results in variations in the input voltage of the inverter 12
associated with the blower 13, this embodiment is suitable for
those applications which do not vary the output voltage of the main
alternator 2.
[0026] FIG. 4 illustrates a yet further embodiment of the present
invention. The following description will be given of parts
different from the foregoing embodiments. The remaining parts are
the same. A contactor 16 is provided in place of the inverter 12
associated with the blower 13 in the embodiment of FIG. 3. The
substitution of the contactor 16 for the inverter 12 associated
with the blower 13 can result in a reduction in cost. However,
since the AC blower 13 is applied with a voltage proportional to
the output voltage of the main alternator 2 at the same frequency
as the output frequency of the main alternator 2, this embodiment
is suitable for those applications which do not fluctuate the
output voltage or output frequency of the main alternator 2.
[0027] FIGS. 6A and 6B represent one embodiment of a method of
controlling the AC blower 13 in the embodiments illustrated in
FIGS. 1, 3, and 4. At step 601, it is determined whether or not the
vehicle is in retarding state. The controller 51 determines the
vehicle is in the retardation state or not based on the signal from
retarding detection sensor 62 disposed on the retard pedal. When
the vehicle is in retarding state, the inverter 12 associated with
the blower 13 in FIG. 1, for example, is operated to drive the
blower 13 at step 603 by applying a control signal to the inverter
12 from the controller 51. On the other hand, when the vehicle is
not in retard state, the inverter 12 associated with the blower 13
in FIG. 1, for example, is stopped to stop the blower 13. While the
foregoing description has been given in connection with the
inverter 12 associated with the blower 13 in FIG. 1, similar
operations can be performed in the configurations of FIGS. 3 and 4,
as a matter of course. In this embodiment, the AC blower 13 is
operated only during a retard. The efficiency can be increased
because the AC blower 13 can be operated only for a minimally
required time.
[0028] FIGS. 7A and 7B represent another embodiment of the method
of controlling the AC blower 13 in the embodiment illustrated in
FIG. 4. Explanation will be made only for the portions of the
further embodiment different from the afore-mentioned embodiments.
At step 701, it is determined whether or not the vehicle is in
retard state. When the vehicle is in retard state, the inverter 12
associated with the blower 13 in FIG. 1, for example, is operated
to drive the blower 13 at step 706. On the other hand, when the
vehicle is not in retard state, it is determined at step 702
whether or not the blower 13 is in operation. When the blower 13 is
not in operation, the flow returns to step 701. On the other hand,
when the blower 13 is in operation, the flow waits for a time ta
(seconds) at step 703. Then, it is determined again at step 704
whether or not the vehicle is in retard state. When in retard
state, the inverter 12 associated with the blower 13 in FIG. 1, for
example, is operated to drive the blower 13 at step 706. When not
in retard state, the inverter 12 associated with the blower 13 in
FIG. 1, for example, is stopped to stop the blower 13 at step 705.
While the foregoing description has been made in connection with
the inverter 12 associated with the blower 13 in FIG. 1, similar
operations can be performed in the configurations of FIGS. 3 and 4,
as a matter of course. In this embodiment, the AC blower 13 is
operated not only during the retardation period but also for a
certain time (ta in FIG. 7A) after the retard has been finished. By
operating the blower 13 after the retarding operation has been
finished, and even after heat generation of the retard resistor 9
has been finished, the heat remaining in the retard resistor 9 can
be removed to prevent abnormal heating after the end of the retard.
In this way, a longer lifetime can be expected for the retard
resistor 9.
[0029] FIGS. 8A and 8B represent a further embodiment of the method
of controlling the AC blower 13 in the embodiments illustrated in
FIGS. 1, 3, and 4. Explanation will be made only for the portions
of the further embodiment different from the afore-mentioned
embodiments. At step 801, it is determined whether or not the
vehicle is in acceleration state. When in acceleration, it is
determined at step 803 whether or not the speed of the vehicle is
substantially zero. If the speed of the vehicle is not
substantially zero, the inverter 12 associated with the blower 13
in FIG. 1, for example, is operated to drive the blower 13 at step
803.
[0030] Conversely, when it is determined at step 801 that the
vehicle is not in acceleration state, or when it is determined at
step 803 that the vehicle speed is substantially zero, the flow
proceeds to step 802. The vehicle speed is calculated based on the
rotation speed of the AC motor 10 detected by a rotation sensor
(not shown), the gear ratio and the wheel diameter. It is
determined at step 802 whether or not the blower 13 is in
operation. When not in operation, the flow returns to step 801. On
the other hand, when the blower 13 is in operation, the blower 13
is left operated for a time ta (seconds) at step 804. Then, it is
determined again at step 805 whether or not the vehicle is in
acceleration state. That is, it is determined as the acceleration
state when the acceleration value is more than a predetermined
value. The acceleration value may be calculated by differentiate
the vehicle speed. When in acceleration, it is determined at step
807 whether or not the vehicle speed is substantially zero. When
the vehicle speed is not substantially zero, the inverter 12
associated with the blower 13 in FIG. 1, for example, is operated
to drive the blower 13 at step 808. On the other hand, when the
speed of the vehicle is substantially zero, the inverter 12
associated with the blower 13 in FIG. 1, for example, is stopped to
stop the blower 13 at step 806. Conversely, when it is determined
at step 805 that the vehicle is not in acceleration state, the
blower 13 is stopped at step 806 in a similar manner.
[0031] While the foregoing description has been made in connection
with the inverter 12 associated with the blower 13 in FIG. 1,
similar operations can be performed in the configurations of FIGS.
3 and 4, as a matter of course.
[0032] In this embodiment, the AC blower 13 is operated when the
vehicle is not in acceleration state and when the speed of the
vehicle is not substantially zero. Also, the AC blower 13 is
stopped after it is operated for a certain time (ta in FIG. 8B)
when the vehicle gets off the condition of no acceleration state
with the vehicle speed in substantially zero. In this embodiment,
the AC blower 13 starts the operation at the time the acceleration
state is terminated. Therefore, the AC blower 13 has begun the
rotation at the time the retarding operation is started. In this
way, it is possible to improve a shortage of air due to a delay in
the start of the rotation of the blower 13 when the retarding
operation is started. Also, by operating the blower 13 even after
the retarding operation is terminated and the retard resistor 9 no
longer generates heat, heat remaining in the retard resistor 9 can
be removed to prevent abnormal heating after the end of the retard.
From the foregoing, the lifetime of the retard resistor is expected
to become longer.
[0033] While the foregoing description has been given of an
embodiment in which gears 10 are interposed between the AC motor 7
and the wheels 11, the present invention can also be applied to a
direct drive system which omits the gears 10.
[0034] It should be further understood by those skilled in the art
that although the foregoing description has been made on
embodiments of the invention, the invention is not limited thereto
and various changes and modifications may be made without departing
from the spirit of the invention and the scope of the appended
claims.
* * * * *