U.S. patent application number 09/850122 was filed with the patent office on 2001-08-30 for hybrid vehicle.
Invention is credited to Amano, Masahiko, Hanyu, Tomoyuki, Masaki, Ryoso, Miyazaki, Taizo.
Application Number | 20010017227 09/850122 |
Document ID | / |
Family ID | 14778942 |
Filed Date | 2001-08-30 |
United States Patent
Application |
20010017227 |
Kind Code |
A1 |
Amano, Masahiko ; et
al. |
August 30, 2001 |
Hybrid vehicle
Abstract
A hybrid vehicle is disclosed, in which the drive torque is
controlled according to a target, and the engine operating point
and the battery charging rate are controlled thereby as targeted to
improve the fuel consumption rate of the hybrid vehicle as a whole
An engine torque estimating unit estimates the engine torque based
on the motor current, and an engine output correction unit.
Inventors: |
Amano, Masahiko;
(Hitachiota-shi, JP) ; Masaki, Ryoso;
(Hitachi-shi, JP) ; Miyazaki, Taizo; (Hitachi-shi,
JP) ; Hanyu, Tomoyuki; (Hitachi-shi, JP) |
Correspondence
Address: |
ANTONELLI TERRY STOUT AND KRAUS
SUITE 1800
1300 NORTH SEVENTEENTH STREET
ARLINGTON
VA
22209
|
Family ID: |
14778942 |
Appl. No.: |
09/850122 |
Filed: |
May 8, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09850122 |
May 8, 2001 |
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09525022 |
Mar 14, 2000 |
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Current U.S.
Class: |
180/65.235 ;
180/65.6; 903/910; 903/945 |
Current CPC
Class: |
B60L 2240/423 20130101;
Y02T 10/70 20130101; Y02T 10/72 20130101; B60W 2510/244 20130101;
B60L 2240/421 20130101; Y10S 903/91 20130101; B60L 50/61 20190201;
Y10S 903/951 20130101; B60K 6/445 20130101; B60W 2050/0006
20130101; B60W 10/26 20130101; F16H 3/727 20130101; B60K 1/02
20130101; B60W 2710/0666 20130101; Y10S 903/945 20130101; B60L
2240/62 20130101; Y02T 90/16 20130101; B60L 58/12 20190201; B60L
2240/441 20130101; B60W 20/00 20130101; B60W 2556/50 20200201; Y10S
903/906 20130101; B60K 6/48 20130101; B60W 20/11 20160101; B60L
2260/42 20130101; B60W 2510/0638 20130101; Y02T 10/62 20130101;
B60K 6/365 20130101; B60W 10/10 20130101; B60W 2710/083 20130101;
Y02T 10/40 20130101; Y10S 903/917 20130101; Y10S 903/903 20130101;
Y02T 10/7072 20130101; B60W 10/115 20130101; F16H 2037/102
20130101; Y02T 10/64 20130101; B60W 2520/10 20130101; B60W 10/06
20130101; B60W 10/08 20130101; B60W 2710/081 20130101; B60L 50/16
20190201; B60W 2510/081 20130101 |
Class at
Publication: |
180/65.2 ;
180/65.6 |
International
Class: |
B60K 006/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 27, 1999 |
JP |
11-120139 |
Claims
What is claimed is:
1. A hybrid vehicle comprising: an engine for generating the energy
for driving the vehicle; a transmission for changing the engine
speed and transmitting the driving force to the wheels; at least a
motor for increasing/decreasing the wheel driving force; a battery
for supplying power to said motor; and a drive control unit for
calculating and outputting an operation command for said engine and
said motor based on the operation information including the
accelerator angle; wherein said drive control unit includes an
engine output correction mechanism for correcting the operation
command value for said engine and maintaining an optimum operating
point of said engine.
2. A hybrid vehicle comprising: an engine for generating the energy
for driving the vehicle; a transmission for changing the engine
speed and transmitting the driving force to the wheels; a motor for
increasing/decreasing the wheel driving force; a battery for
supplying power to said motor; means for determining a target
torque value of said engine; means for calculating the engine
torque generated by said engine; and means for correcting the
output of said engine based on the difference between the target
value of the engine torque and the engine torque calculated by said
engine torque calculation means.
3. A hybrid vehicle according to claim 1, wherein the torque
generated by said engine is calculated based on the detected torque
value of said motor or a toque command value.
4. A hybrid vehicle according to claim 2, wherein said torque
generated by said engine is calculated based on the detected torque
value of said motor or a torque command value.
5. A hybrid vehicle comprising: an engine for generating the energy
for driving the vehicle; a transmission for changing the engine
speed and transmitting the driving force to the wheels; a motor for
increasing/decreasing the wheel driving force; means for
determining a target output value of said engine; means for
calculating the output generated by said engine; and means for
correcting the output of said engine based on the difference
between the target engine output value and the engine output value
calculated by said engine output calculation means, thereby
maintaining an optimum operating point of said engine.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a hybrid vehicle having an
engine and a motor, or in particular to a hybrid vehicle in which
the fuel consumption can be improved by controlling the operating
point of the engine and the battery charging rate according to a
target.
[0002] One system intended to reduce engine fuel consumption is a
hybrid vehicle utilizing the driving force of the motor. Various
types of such a system have been proposed and include the series
type and the parallel type. For example, JP-A-7-135701 discloses a
system in which two motors and one planetary gear are used so that
the engine driving force is input to the planetary gear, and the
motor is controlled to drive the vehicle by the driving force
obtained from the output shaft of the planetary gear. Part of the
energy of the engine is derived from a generator (which is one of
the motors) generating power while the motor coupled to the output
shaft of the generator delivers a driving force as an assistance.
Thus, the engine is always driven efficiently in a high torque area
while at the same time providing the shift function.
[0003] A method of controlling the driving torque of the hybrid
vehicle is described in JP-A-8-207601 in which the torque of the
generator is calculated and the torque of the motor on the output
shaft is corrected by the calculated torque of the generator.
According to this method, the vehicle driving torque is not
affected greatly by variations in the engine output and therefore
the drivability can be improved.
[0004] In order to suppress the change in the charging condition of
the battery connected to the generator or the motor, on the other
hand, JP-A-10-243503 discloses a method in which the motor torque
command or the target engine speed is corrected in accordance with
the current value of the battery. This method can maintain the
normal condition of the battery and therefore can prevent the
deterioration of the battery. Also, the battery charging rate can
be controlled as scheduled.
[0005] Of all the methods described above, the method of correcting
the output of the motor according to the estimated torque value can
control the vehicle drive torque as intended and therefore can
improve the drivability. Nevertheless, the change in motor output
may cause unexpected charge and discharge of the battery, often
leading to the deviation from the optimum schedule for charging the
battery, resulting in a deteriorated fuel consumption rate.
[0006] According to the method of correcting the motor output or
the target engine speed in accordance with the battery current or
the like, on the other hand, the battery deterioration can be
prevented and the optimum schedule can be followed. However, the
required driving output cannot be produced often adversely
affecting the drivability.
[0007] In any of the methods described above, the engine operating
point, if deviated from the target, is not corrected, thereby
posing the problem that the engine deviates from the optimum
operating point and the fuel consumption rate is deteriorated.
SUMMARY OF THE INVENTION
[0008] The object of the invention is to provide a hybrid vehicle n
which the efficiency and the fuel consumption can be improved by
controlling the engine operating point and the battery charging
rate as intended without adversely affecting the drivability.
[0009] In order to achieve the aforementioned object, according to
the invention, there is provided a hybrid vehicle comprising an
engine for generating the energy for driving the vehicle, a
transmission for transmitting the driving force to the wheels by
changing the rotational speed of the engine, at least a motor for
changing the wheel driving force, a battery for supplying power to
the motor, and a drive control unit for calculating and outputting
an operation command value for the engine and the motor based on
the drive information including the accelerator angle, wherein the
drive control unit includes an engine output correcting mechanism
for correcting the operation command value for the engine based on
the difference between the engine operation command value and the
torque generated by the engine thereby to maintain an optimum
engine operating point.
[0010] The optimum operating point is defined as a point on or near
a curve associated with the best fuel consumption rate of the
engine including the efficiency of the transmission and the
motor.
[0011] According to another aspect of the invention, there is
provided a hybrid vehicle comprising an engine for generating the
energy for driving the vehicle, a transmission for transmitting the
driving force to the wheels by changing the rotational speed of the
engine, at least a motor for changing the wheel driving force, a
battery for supplying power to the motor, means for determining a
target engine torque, means for calculating the torque generated by
the engine, and means for correcting the engine output based on the
difference between the target engine torque value and the engine
torque value calculated by the engine torque calculation means.
[0012] According to still another aspect of the invention, there is
provided a hybrid vehicle comprising an engine for generating the
energy for driving the vehicle, transmission for transmitting the
driving force to the wheels by changing the rotational speed of the
engine, at least a motor for changing the wheel driving force, a
battery for supplying power to the motor, means for determining a
target engine output value instead of the engine torque, means for
calculating the output of the engine, and means for correcting the
engine output based on the difference between the target engine
output value and the calculated engine output value.
[0013] According to yet another aspect of the invention, there is
provided a hybrid vehicle comprising an engine for generating the
energy for driving the vehicle, a transmission for transmitting the
driving force to the wheels by changing the rotational speed of the
engine, at least a motor for changing the wheel driving force, a
battery for supplying power to the motor, a battery management unit
for determining a target current value of the battery, means for
detecting the battery current, and means for correcting the engine
output based on the difference between a target battery current and
a detected battery current value, wherein the battery management
unit produces a schedule for the battery charging rate based on the
navigation information and determines the target battery current
value based on the difference between the detected value of the
battery charging rate and the scheduled battery charging rate.
[0014] The engine output correcting means can correct the output by
controlling the throttle opening degree or correcting the target
engine output value.
[0015] According to this invention, an optimum engine operating
point can be maintained while producing the target vehicle driving
torque and also the battery charging rate can be kept as scheduled
for an improved fuel consumption rate.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is a diagram showing an example of a configuration of
a driving system of a hybrid vehicle according to this
invention.
[0017] FIG. 2 is a diagram showing a configuration of a drive
control unit shown in FIG. 1.
[0018] FIG. 3 is a diagram showing a configuration of an engine
output correcting unit shown in FIG. 2.
[0019] FIG. 4 is a diagram for explaining the engine operating
point.
[0020] FIG. 5 is a diagram showing a configuration of another
example of the hybrid vehicle driving system according to this
invention.
[0021] FIG. 6 is a diagram showing a configuration of the drive
control unit shown in FIG. 5.
[0022] FIG. 7 is a diagram showing another configuration of the
drive control unit of the hybrid vehicle driving system according
to the invention.
[0023] FIG. 8 is a diagram showing still another configuration of
the drive control unit according to this invention.
[0024] FIG. 9 is a diagram showing a configuration of the hybrid
vehicle of another type according to the invention.
[0025] FIG. 10 is a diagram showing yet another configuration of
the drive control unit according to the invention.
DESCRIPTION OF THE EMBODIMENTS
[0026] FIG. 1 shows a hybrid vehicle in which the tires 3a, 3b are
rotated by use of the energy of an engine through a drive shaft 2.
This hybrid vehicle including a planetary gear train A4 and a
planetary gear train B5 as a differential mechanism each including
a sun gear, a planetary gear and a ring gear. The sun gears are
driven by a motor A8 and a motor B9 controlled by power converters
10, 11, respectively. The battery 12 is used for supplying the
energy required by these motors or storing the energy generated in
these motors at the time of deceleration braking. Each planetary
gear is fastened to the same input shaft, and the driving torque of
the engine 1 is divided into two or more planetary gears. The ring
gears, on the other hand, are coupled to a common output shaft
through gears having different gear ratios. The torque output from
the two planetary gear trains are combined into a vehicle drive
torque .tau.v. As a result, it is possible to secure an
acceleration or deceleration of the vehicle as intended by the
driver. By controlling the torque .tau.a, .tau.b and the speeds
.omega.a, .omega.b of the motors A8, B9 for driving the sun gears,
on the other hand, the vehicle drive torque .tau.v and the engine
speed .omega.e can be regulated. The drive control unit 31
calculates and outputs the engine throttle opening degree command
value .theta.t, the speed command value .omega.ar of the motor A
and the torque command value .tau.br of the motor B using
predetermined functions and data according to predetermined
processing steps based on the information including the accelerator
angle .theta.a, the vehicle speed .omega.v, the torque command
value .tau.ar of the motor A and the currents Ia, Ib of the motors
A, B. The drive control unit 31 is configured with a microcomputer
including a CPU, a RAM, a ROM, input/output control means and
various programs stored in the ROM.
[0027] A specific method of controlling the motors A8, B9 is
described below. In the system shown in FIG. 1, equations (1) to
(4) below hold.
.omega.e=Kp.omega.a+Ka.omega.v (1)
.omega.e=Kp.omega.b+Kb.omega.v (2)
.tau.e=(.tau.a+.tau.b)/Kp (3)
.tau.v=(Ka.tau.a+Kb.tau.b)/Kp (4)
[0028] where .omega.e, .omega.v, .omega.a, .omega.b are the engine
speed, the vehicle speed, the rotational speed of the motor A and
the rotational speed of the motor B, respectively, and .tau.e,
.tau.a, .tau.b, .tau.v the engine torque, the torque of the motor
A, the torque of the motor B and the vehicle drive torque,
respectively. Characters Kp, Ka, Kb are constants relating to the
gear ratio.
[0029] Using this relation, the following equation (5) is obtained
from equation (1).
.omega.ar=(.omega.er-Ka.omega.v) (5)
[0030] where .omega.er is the target engine speed, .omega.v the
detected vehicle speed and .omega.ar the rotational speed setting
of the motor A.
[0031] By controlling the rotational speed of the motor A based on
this equation, the engine can be driven at the desired operating
point and the desired change gear ratio is obtained.
[0032] Also, let .tau.vr be the target vehicle drive torque, and
.tau.a be the output torque of the motor A, and from equation (4),
the following relation holds.
.tau.br=(Kp.tau.vr-Ka.tau.a)/Kb (6)
[0033] Assuming that .tau.br determined from equation (6) is a
torque setting of the motor A, the desired vehicle drive torque can
be obtained.
[0034] By controlling the motors according to equations (5) and
(6), the engine speed can be controlled to the desired change gear
ratio or the target vehicle drive torque can be generated. Equation
(6) contains no engine torque .tau. e, and therefore even when the
engine torque undergoes a change, the vehicle drive torque can be
controlled as targeted by controlling the two motors.
[0035] The drive control unit 31, which is for realizing the
aforementioned control operation, calculates and outputs the engine
throttle opening command value .theta.t, the speed command value
.omega.ar of the motor A and the torque command value .tau.br of
the motor B based on the information including the accelerator
angle .theta.a, the vehicle speed .omega.v, the torque command
value .tau.ar of the motor A and the currents Ia, Ib of the motors
A, B. The throttle opening command value .theta.t is sent to the
throttle control unit 13, the motor A speed command value .omega.ar
to the motor A control unit 14, and the motor B torque command
value .tau.br to the motor B control unit 15 thereby to actually
control the engine and the motors.
[0036] The motor A control unit 14, based on the difference between
the speed command value .omega.ar and the speed detection value
.omega.a, produces the torque command value .tau.ar in such a
manner as to eliminate the difference by the proportional integral
control or the like thereby to control the power converter 10.
Also, the torque command value .tau.ar involved is sent to the
drive control unit 31.
[0037] Now, the configuration of the drive control unit 31 will be
explained with reference to FIG. 2.
[0038] First, the target drive torque determining unit 21
determines a target drive torque .tau.vr of the vehicle based on a
map predetermined from the accelerator angle .theta.a and the
vehicle speed .omega.v.
[0039] In the overall control unit 22, the engine output and the
change gear ratio are determined based on the target drive torque
.tau.vr and the vehicle speed .omega.v, and the engine operating
point X (the target engine speed .omega.er, the target torque
.tau.er) is calculated. In the process, the operating point is
determined in such a manner as to enable the engine to operate in
an area as efficient as possible.
[0040] The engine control unit 23 determines the throttle opening
command value .theta.to in accordance with the target engine speed
.omega.er and the target torque .tau.er determined in the overall
control unit 22. The correction value .DELTA..theta.t determined in
the engine output correction unit 27 is added to .theta.to to
obtain .theta.t, and a command is issued to the throttle control
unit 13.
[0041] The motor A control unit 24 calculates the speed command
value .omega.ar determined in equation (5) based on the target
engine speed .omega.er determined in the overall control unit 22
and the actual measurement .omega.v of the vehicle speed and issues
a speed command to the motor A control unit 14.
[0042] The motor B control unit 25 calculates the torque command
value .tau.br of the motor B by substituting .tau.ar into .tau.a of
equation (6) based on the target drive torque .tau.vr of the
vehicle and the torque command value .tau.ar of the motor A8 sent
from the overall control unit 22, and issues a command to the motor
B control unit 15.
[0043] The engine torque estimation unit 41 determines an estimated
engine torque .tau.e by the following method from the armature
currents Ia, Ib of the motors A8, B9.
[0044] First, the input torque .tau.ai of the motor A8 is
calculated based on the following equation from the armature
current Ia of the motor A8.
.tau.ai =Pn.theta.Iq+Pn(Ld-Lq)IdIq (7)
[0045] where .theta. is the magnetic fluxes interlinking the
armature, Pn the number of poles, Id, Iq the Ia components along d
and q axes, respectively, and Ld, Lq inductances of the armature
winding along d and q axes, respectively.
[0046] Then, the output torque .tau.a is calculated from the
relation of equation (8)
.tau.a=.tau.ai-Ja(d.omega.a/dt) (8)
[0047] where Ja is the inertia of the motor A8, and d.omega.a/dt
the change rate of the rotational speed. The change rate of the
rotational speed can be calculated from the difference of the
rotational speed .omega.a or the like. A simple method of this
calculation is to ignore the term of the change rate of the
rotational speed and regard the input torque as an output
torque.
[0048] This is also the case with the motor B, for which the output
torque .tau.b is calculated from the armature current Ib. The motor
output torque .tau.a and .tau.b thus calculated are substituted
into equation (3) thereby to determine the estimated engine torque
.tau.e.
[0049] The engine output correction unit 42 calculates the throttle
opening correction value .DELTA..theta.t in accordance with the
difference between the target engine torque .tau.er and the
estimated engine torque .tau.e. The correction value is determined
in such a manner as to increase the throttle opening in the case
where the estimated torque is smaller, and to decrease the throttle
opening in the case where the estimated torque is larger. By doing
so, the engine output can be controlled so that the engine torque
approaches the target torque.
[0050] FIG. 3 shows an example configuration for the proportional
integral control. By setting the gains Kp and Ki appropriately, the
control operation can be performed to eliminate the difference
between the target torque and the estimated torque rapidly.
[0051] Now, the effect of correcting the engine output will be
explained with reference to FIG. 4. Assume that the overall control
unit 22 has determined a target operating point of the engine at
point X on the best fuel consumption curve including the
transmission efficiency and the motor efficiency based on a given
target drive torque .tau.vr and the vehicle speed .omega.v. The
engine control unit 23 controls the throttle valve to attain the
operating point at point X. In view of the fact that the engine
characteristics change with the atmospheric pressure or the like,
however, the target output may fail to be achieved. For example,
the actual torque may deviate to point Y. By the way, the engine
speed .omega.e, which can be controlled accurately by controlling
the speed of the motor A, is assumed not to develop any
deviation.
[0052] Once the actual operating point deviates from the target
operating point in this way, the optimum operating point is missed,
and therefore the fuel consumption rate may deteriorate. Also, the
control method described above is intended to secure the required
drive torque from the motor regardless of the engine torque, and
therefore the engine output deviation from the target leads to an
unexpected discharge or charge of the battery power. In the case of
FIG. 4, for example, the engine output runs short and therefore the
motor output increases correspondingly, resulting in the battery
being discharged. A protracted situation of this battery discharge
will cause the battery charging rate to deviate from the target
value and therefore the need arises for an unexpected charging
operation, thereby leading to an overall deterioration of the
efficiency.
[0053] The present invention is intended for a control operation in
which the target engine operating point is set at or in the
vicinity of point X (optimum operating point) on the total best
fuel consumption rate curve including the efficiency of the
transmission and the motor. The use of this method can correct this
engine torque deviation and restore the operating point at or in
the vicinity of point X. Thus, the engine operates at the optimum
operating point and the battery charging rate undergoes no
unexpected change, thereby preventing the deterioration of the fuel
consumption rate.
[0054] In the aforementioned example, the output torque is
calculated from the armature current of the motor. As an
alternative, an estimated engine torque value .tau.e can be
determined by substituting the torque command values .tau.ar,
.tau.br directly into .tau.a, .tau.b in equation (3). In such a
case, the estimation is possible using a simple method without
using the motor current at the sacrifice of the likelihood of an
estimation error being developed.
[0055] A similar effect is attained also by attaching a torque
detector to the engine output shaft and using the output of the
torque detector as an estimated torque value. In such a case, the
detection accuracy is improved as compared with the estimation
based on the motor torque.
[0056] Also, instead of correcting the output based on the
deviation from the target engine torque value as in the
aforementioned case, a similar effect can be obtained by a method
of detecting the deviation from the target engine output. The
engine output is determined as the product of the engine torque and
the engine speed. In FIG. 2, therefore, this method can be
accomplished by adding the engine speed information.
[0057] Now, another example configuration of the drive control unit
will be explained with reference to FIGS. 5 and 6. In this example,
the distance to be covered up to the destination constituting the
navigation information, the current Ic flowing in the battery 12
and the battery charging rate SOC are input to the drive control
unit 32.
[0058] The battery management unit 43 first produces a schedule for
the battery charging rate based on the navigation information. In
the case where a mountainous road and an ascending slope are in the
way ahead, the battery charging rate is set to a larger value to
provide a sufficient torque assistance by the motor. In the case
where a descending road ahead is forecast, on the contrary, the
battery charging rate is set to a smaller value to provide a
sufficient regenerative braking. Also, in the case where an urban
area is nearing and a low-speed run on the motor is expected, the
battery charging rate is increased.
[0059] Then, the battery charging rate schedule thus prepared is
compared with the current battery charging rate, and based on the
difference, a target power value Pcr to be charged to (or
discharged from) the battery is determined. At the same time, the
target value Icr of the charge (or discharge) current for the
battery is calculated. The target battery current value Icr is
calculated by solving the quadratic equation (9), for example.
Pcr=IcVo+Ic.sup.2R (9)
[0060] where vo is the electromotive force of the battery, and R
the internal resistance of the battery. As for the signs attached
to Pcr and Icr, the plus sign is defined as indicating the charging
and the minus sign as indicating the discharge.
[0061] The overall control unit 22 determines the engine output and
the change gear ratio based on the target drive torque .tau.vr, the
vehicle speed .omega.v and the target battery power Pcr, and
calculates the engine operating point (target engine speed
.omega.er, the target engine torque .tau.er). In the case where the
target battery power value Pcr is positive (charging), the target
engine output value is the sum of the output for driving the
vehicle and the output for charging the battery. In the case where
the target value Pcr is negative (discharge), on the other hand,
the target engine output is decreased correspondingly.
[0062] As described above, by correcting the target engine output
value as required for the charge or discharge of the battery, the
battery charging rate can be managed as targeted. In view of the
aforementioned fact that the engine characteristics are subjected
to various changes, however, the target output is not always
produced. In the case where the target X is missed and the point Y
is reached instead, as shown in FIG. 4, for example, the engine
output decreases and the discharge increases correspondingly. Also,
the loss occurring in the motor may change depending on the
prevailing conditions. As a result, it may be that the target
battery current cannot be secured, often making it impossible to
manage the battery charging rate to the target value. In such a
case, the correction is carried out by the engine output correction
unit 44 as described below.
[0063] In the engine output correction unit 44, the throttle
opening correction value .DELTA..theta.t is calculated based on the
difference between the target battery current value Icr and the
detected current value Ic. In the case where the detected value is
smaller, the throttle valve opening is increased to increasing the
charging rate, while in the case where the detected value is
larger, the throttle opening value is reduced. As a result, the
engine operating point is corrected from point Y to point X, for
example, in FIG. 4 thereby making it possible to control the
battery current toward the target value. As a configuration of the
control system, the proportional integral control similar to that
shown in FIG. 3 can be used. By doing so, the engine output, even
if it deviates from the target value, can be corrected so that the
battery current attains the target value.
[0064] Now, another configuration example of the drive control unit
32 will be explained with reference to FIG. 7. In this example, the
engine output correction unit 45 outputs the battery power
correction value .theta.Pcr but not the throttle opening correction
value .DELTA..theta.t based on the difference between the target
battery current value Icr and the detected battery current value
Ic, and adds the battery power correction value .DELTA.Pcr to the
target battery power value Pcr output from the battery management
unit. In the case where the detected battery current value is
smaller than the target battery current value, the target battery
power value is corrected upward. By doing so, the target engine
output value is corrected and therefore the engine output is
indirectly corrected, thereby making it possible to control the
battery current as targeted.
[0065] Further, an example configuration with the cases of FIGS. 2
and 7 combined is shown in FIG. 8. In this case, the engine output
correction unit 42 outputs the throttle opening correction value
.DELTA..theta.t based on the estimated engine torque value, and the
engine output correction unit 45 outputs the battery power
correction value .DELTA.Pcr based on the detected battery current
value. With this configuration, the engine is always kept at the
optimum operating point, while at the same time controlling the
battery current to the target value.
[0066] The foregoing description concerns the case in which the
schedule for battery charging rate is prepared by the battery
management unit 43 using the navigation information. The present
invention is applicable, however, also to the case where the
charging rate is managed simply by setting the upper and lower
limits thereof without using the navigation information. In such a
case, too, the battery charge and discharge can be controlled to
the target by correcting the engine output while always securing
the vehicle driving force.
[0067] Now, an explanation will be given of the case in which the
invention is applied to an ordinary hybrid vehicle other than shown
in FIG. 1.
[0068] FIG. 9 shows a hybrid vehicle comprising an engine 1, a
transmission 17, a motor 16 for changing the drive torque, and a
power converter 11 and a battery 12 for driving the motor. The
drive control unit 30 outputs the engine throttle opening command
value .theta.t, the change gear ratio command value r, the motor
torque command value .tau.r based on the information including the
accelerator angle .theta.a and the vehicle speed .omega.v. The
throttle opening command value .theta.t is sent to the throttle
control unit 13, the change gear ratio command r to the
transmission control unit 19, and the motor torque command .tau.r
to the motor control unit 15.
[0069] The configuration of the drive control unit 34 will be
explained with reference to FIG. 10. The target torque determining
unit 21, the overall control unit 22, the engine control unit 23
and the battery management unit 43 are similar to the corresponding
parts shown in FIG. 6. The transmission control unit 27 calculates
the change gear ratio command value r from the target engine speed
.omega.er determined by the overall control unit 22 and the actual
measurement .omega.v of the vehicle speed, and issues a command to
the transmission control unit 19. The motor control unit 26
calculates the torque required of the motor for assistance, from
the target drive torque .tau.vr of the vehicle and the target
engine torque .tau.er, and outputs a motor torque command
.tau.r.
[0070] The engine output correction unit 44 operates similarly to
the case of FIG. 6 and calculates the throttle opening correction
value .DELTA..theta.t based on the difference between the target
battery current value Icr and the detected battery current value Ic
output from the battery management unit 43. In the case where the
detected value is smaller, the throttle opening value is increased
to increase the charging rate, while in the case where the detected
value is larger, the throttle opening is decreased. As a result,
the battery current can be controlled to approach the target
value.
[0071] There is also a method for correcting the battery current
which may be different from the target value in response to a
command from the motor. This method, however, employed is at the
risk of failing to achieve the target drive torque of the vehicle.
In this method, if the motor is controlled to produce the target
drive torque and the battery current is corrected on the engine
side, the battery charging rate can be managed while at the same
time producing a target drive torque.
[0072] It will thus be understood from the foregoing description
that according to this invention, the engine output is corrected
while maintaining a target vehicle driving force, thereby making it
possible to control the engine operating point and the battery
charging rate to the target, thereby improving the fuel consumption
rate of the vehicle as a whole.
* * * * *