U.S. patent application number 09/861620 was filed with the patent office on 2002-02-07 for vehicle drive power control apparatus, and control method.
This patent application is currently assigned to TOYOTA JIDOSHA KABUSHIKI KAISHA. Invention is credited to Kubota, Hirofumi, Mashiki, Zenichiro, Mitani, Shinichi, Takagi, Isao, Tanaka, Hiroya.
Application Number | 20020014363 09/861620 |
Document ID | / |
Family ID | 18657133 |
Filed Date | 2002-02-07 |
United States Patent
Application |
20020014363 |
Kind Code |
A1 |
Kubota, Hirofumi ; et
al. |
February 7, 2002 |
Vehicle drive power control apparatus, and control method
Abstract
A vehicle drive power control apparatus and method control the
speed ratio of a transmission based on a speed shift line that is
set so that, within a practical region, the speed shift line is in
a low revolution speed side of an optimal fuel consumption line
determined based on the efficiency of the engine and the efficiency
of the transmission. Therefore, the width of increase in revolution
speed from the speed occurring at the beginning of the practical
region is curbed. Hence, the fuel consumption resulting from
inertia torques caused by fluctuations in engine revolution speed,
that is, fluctuations in the revolution speed of the input shaft of
the transmission and a fluidic power transfer mechanism, is
reduced, so that the efficiency as a whole increases and the fuel
economy improves in comparison with the case where the optimal fuel
consumption line is used as a control basis.
Inventors: |
Kubota, Hirofumi;
(Mishima-shi, JP) ; Mashiki, Zenichiro;
(Nisshin-shi, JP) ; Takagi, Isao; (Okazaki-shi,
JP) ; Tanaka, Hiroya; (Nishikamo-gun, JP) ;
Mitani, Shinichi; (Susono-shi, JP) |
Correspondence
Address: |
OLIFF & BERRIDGE, PLC
P.O. BOX 19928
ALEXANDRIA
VA
22320
US
|
Assignee: |
TOYOTA JIDOSHA KABUSHIKI
KAISHA
1, TOYOTA-CHO AICHI-KEN
TOYOTA-SHI
JP
471-8571
|
Family ID: |
18657133 |
Appl. No.: |
09/861620 |
Filed: |
May 22, 2001 |
Current U.S.
Class: |
180/197 ;
701/103 |
Current CPC
Class: |
Y02T 10/40 20130101;
B60W 2710/0666 20130101; F16H 2061/0018 20130101; Y02T 10/60
20130101; B60W 10/101 20130101; Y02T 10/84 20130101; B60W 30/18
20130101; F16H 2061/66209 20130101; B60W 10/06 20130101; F16H 61/66
20130101; F16H 2061/0015 20130101; B60W 2710/1005 20130101; F16H
2059/743 20130101; B60W 2710/0622 20130101 |
Class at
Publication: |
180/197 ;
701/103 |
International
Class: |
G06F 007/00; B60K
001/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 23, 2000 |
JP |
2000-151602 |
Claims
What is claimed is:
1. A drive power control apparatus of a vehicle, comprising: an
engine that generates a drive power of the vehicle; a transmission
that is connected to an output shaft of the engine and that
performs a speed shift of the vehicle; and a controller that:
determines a target drive power based on a state of operation of
the vehicle; controls a torque of the engine and a speed ratio of
the transmission so as to achieve the target drive power, wherein
the controller controls the speed ratio of the transmission based
on a speed shift line that is plotted on a graph having a pair of
axes defining a revolution speed of the engine and the torque of
the engine so that, within a practical region in which the state of
operation of the engine is practical, the speed shift line is at a
low revolution speed side of an optimal fuel consumption line that
is determined based on at least an efficiency of the engine and an
efficiency of the transmission, of an efficiency of a drive system
that includes the engine and the transmission.
2. A drive power control apparatus according to claim 1, wherein
the speed shift line is set so that, within the practical region, a
difference between a minimum revolution speed and a maximum
revolution speed on the speed shift line is smaller than a
difference between a minimum revolution speed and a maximum
revolution speed on the optimal fuel consumption line.
3. A drive power control apparatus according to claim 1, wherein
the speed shift line is set so that, within the practical region, a
sensitivity of a fluctuation in the revolution speed with respect
to a fluctuation in the target drive power on the speed shift line
is lower than a sensitivity of a fluctuation in the revolution
speed with respect to the fluctuation in the target drive power on
the optimal fuel consumption line.
4. A drive power control apparatus according to claim 1, wherein
the speed shift line is set so that a width of increase in the
revolution speed of the engine from a revolution speed occurring at
a beginning of the practical region to a relatively high revolution
speed is curbed.
5. A drive power control apparatus according to claim 1, wherein
the internal combustion engine selectively performs at least one
form of combustion in accordance with the state of operation, and
the optimal fuel consumption line reflects the efficiency of the
engine with respect to the at least one form of combustion.
6. A drive power control apparatus according to claim 5, wherein
the at least one form of combustion includes a stoichiometric
air-fuel ratio combustion and a lean combustion.
7. A drive power control apparatus according to claim 6, wherein:
the engine comprises a NOx storage-reduction type catalyst in an
exhaust system, and during the lean combustion, the engine reduces
NOx stored in the NOx storage-reduction type catalyst by performing
a rich spike control that temporarily changes an air-fuel mixture
so that a fuel concentration in the mixture becomes higher than the
fuel concentration corresponding to a stoichiometric air-fuel
ratio, and on a boundary line between the lean combustion and the
stoichiometric air-fuel ratio combustion in the graph, the speed
shift line passes through or near a point at which a corrected fuel
consumption rate determined by considering the rich spike control
and a fuel consumption rate provided during the lean combustion
becomes equal to or closest to a fuel consumption rate provided
during the stoichiometric air-fuel ratio combustion.
8. A drive power control apparatus according to claim 1, wherein
the speed shift line is set such that as the torque of the engine
increases, the revolution speed of the engine remains constant or
increases.
9. A drive power control apparatus according to claim 1, wherein
the transmission is a continuously variable transmission and the
engine is an internal combustion engine.
10. A drive power control apparatus of a vehicle, comprising: an
engine that generates a drive power of the vehicle; a transmission
that is connected to an output shaft of the engine and that
performs a speed shift of the vehicle; and a controller that:
calculates a target output of the engine for achieving a target
drive power that is set based on a state of operation of the
vehicle, and sets a target revolution speed of the internal
combustion engine based on a speed shift line that is plotted on a
graph having a pair of axes defining a revolution speed of the
engine and the target output of the engine so that, within a
practical region in which the state of operation of the engine is
practical, a width of increase in the revolution speed of the
engine to a relatively high revolution speed on the speed shift
line is curbed compared with an optimal fuel consumption line
determined based on at least an efficiency of the engine and an
efficiency of the transmission, of an efficiency of a drive system
that includes the engine and the transmission; and controls the
speed ratio of the transmission so that an actual revolution speed
of the engine becomes equal to the target revolution speed.
11. A drive power control apparatus according to claim 10, wherein
the transmission is a continuously variable transmission and the
engine is an internal combustion engine.
12. A drive control method for a vehicle that is driven by an
output of an engine via a transmission, the method comprising:
calculating a target output of the engine for achieving a target
drive power that is set based on a state of operation of the
vehicle; setting a target revolution speed of the engine based on a
speed shift line that is plotted on graph having a pair of axes
defining speed of the engine and the target output of the engine so
that, within a practical region in which the state of operation of
the engine is practical, a width of increase in the revolution
speed of the engine to a relatively high revolution speed on the
speed shift line is curbed compared with an optimal fuel
consumption line determined based on at least an efficiency of the
engine and an efficiency of the transmission, of an efficiency of a
drive system that includes the engine and the transmission; and
controlling the speed ratio of the transmission so that an actual
revolution speed of the engine becomes equal to the target
revolution speed.
13. A control method according to claim 12, wherein the speed shift
line is set so that, within the practical region, a difference
between a minimum revolution speed and a maximum revolution speed
on the speed shift line is smaller than a difference between a
minimum revolution speed and a maximum revolution speed on the
optimal fuel consumption line.
14. A control method according to claim 12, wherein the speed shift
line is set so that, within the practical region, a sensitivity of
a fluctuation in the revolution speed with respect to a fluctuation
in the target drive power on the speed shift line is lower than a
sensitivity of a fluctuation in the revolution speed with respect
to the fluctuation in the target drive power on the optimal fuel
consumption line.
15. A control method according to claim 12, wherein the speed shift
line is set so that within the practical region, the revolution
speed on the speed shift line is lower than the revolution speed on
the optimal fuel consumption line.
16. A control method according to claim 12, wherein the engine
selectively performs at least one form of combustion in accordance
with the state of operation, and the optimal fuel consumption line
reflects the efficiency of the engine with respect to the at least
one of combustion.
17. A control method according to claim 16, wherein the at least
one form of combustion includes a stoichiometric air-fuel ratio
combustion and a lean combustion.
18. A control method according to claim 17, wherein: the engine
comprises a NOx storage-reduction type catalyst in an exhaust
system, and during the lean combustion, the internal combustion
engine reduces NOx stored in the NOx storage-reduction type
catalyst by performing a rich spike control that temporarily
changes an air-fuel mixture so that a fuel concentration in the
mixture becomes higher than the fuel concentration corresponding to
a stoichiometric air-fuel ratio, and on a boundary line between the
lean combustion and the stoichiometric air-fuel ratio combustion in
the graph, the speed shift line passes through or near a point at
which a corrected fuel consumption rate determined by considering
the rich spike control and a fuel consumption rate provided during
the lean combustion becomes equal to or closest to a fuel
consumption rate provided during the stoichiometric air-fuel ratio
combustion.
19. A control method according to claim 12, wherein the
transmission is a continuously variable transmission and the engine
is an internal combustion engine.
Description
INCORPORATION BY REFERENCE
[0001] The disclosure of Japanese Patent Application No.
2000-151602 filed on May 23, 2000 including the specification,
drawings and abstract is incorporated herein by reference in its
entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of Invention
[0003] The present invention relates to a vehicle drive power
control apparatus which determines a target drive power based on a
state of operation of a vehicle driven by output of an internal
combustion engine via a continuously variable transmission, and
which controls the torque of the engine and the speed ratio of the
continuously variable transmission so as to obtain an output of the
engine for achieving the target drive power. The invention also
relates to a control method of the apparatus.
[0004] 2. Description of Related Art
[0005] As apparatuses for controlling the drive power of a vehicle
so as to achieve good fuel economy, apparatuses of generally termed
coordinate control performed through the use of a continuously
variable transmission are known (Japanese Patent Application
Laid-Open No. 11-198684 and No. 10-329587). This coordinate control
determines a target drive power based on the state of operation of
the vehicle, and coordinately controls the torque of the internal
combustion engine and the speed ratio of the continuously variable
transmission so as to obtain the engine output that achieves the
determined target drive power with a minimum fuel consumption rate.
Through the coordinate control, the fuel economy is improved.
[0006] In such a drive power control apparatus, speed shift lines
of the continuously variable transmission are set so as to conform
to optimal fuel economy lines (FIG. 19) based on the efficiency of
the internal combustion engine, or to optimal fuel economy lines
(comparative examples indicated by one-dot chain lines in FIGS. 12
and 15) determined with the efficiency of the internal combustion
engine and the efficiency of the continuously variable transmission
(FIG. 20) taken into consideration.
[0007] However, in the vehicles equipped with the above-described
drive power control apparatus, the fuel economy has not been
sufficiently improved in a practical region. A reason for the
insufficient improvement is as follows. Based on the speed shift
lines set so as to conform to optimal fuel economy lines as
described above, the running of the vehicle in a practical region
involves a fuel consumption increase corresponding to the inertia
torques caused by fluctuated rotations of an input shaft of the
continuously variable transmission, so that a low efficiency
results as a whole.
SUMMARY OF THE INVENTION
[0008] It is an object of the invention to provide a vehicle drive
power control apparatus capable of improving fuel economy by
reducing the fuel consumption caused by the aforementioned inertia
torque and thereby enhancing the efficiency as a whole, and a
control method of the apparatus.
[0009] In accordance with a first mode of the invention, a drive
power control apparatus of a vehicle that is driven by the output
of an engine via a transmission determines a target drive power
based on a state of operation of the vehicle, and controls the
torque of the engine and the speed ratio of the transmission so as
to provide an output of the engine for achieving the target drive
power. The control apparatus controls the speed ratio of the
transmission based on a speed shift line that is plotted on a graph
having a pair of axis defining the revolution speed of the engine
and the torque of the engine so that, within a practical region,
the speed shift line is at a low revolution speed side of an
optimal fuel consumption line that is determined based on at least
the efficiency of the engine and the efficiency of the
transmission, of the efficiency of a drive system that includes the
engine and the transmission.
[0010] The speed ratio of the transmission is controlled in
accordance with the speed shift line that is set so that, within
the practical region, the speed shift line is located on the low
revolution speed side of the optimal fuel consumption line
determined based on the efficiencies of the engine and the
transmission of the drive system. Thus, the speed shift line is
shifted to the low engine speed side within the practical region.
Therefore, the width of increase in engine revolution speed from
the level occurring at the beginning of the practical region is
curbed. Hence, the fuel consumption resulting from inertia torques
caused by fluctuations in the engine revolution speed, that is,
fluctuations in the revolution speed of the input shaft of the
transmission, is reduced, so that the efficiency as a whole
increases and the fuel economy improves in comparison with the case
where the optimal fuel consumption line is used as a control
basis.
[0011] The speed shift line may be set so that, within the
practical region, a difference between a minimum revolution speed
and a maximum revolution speed on the speed shift line is smaller
than a difference between a minimum revolution speed and a maximum
revolution speed on the optimal fuel consumption line. Furthermore,
the speed shift line may be set so that, within the practical
region, a sensitivity of a fluctuation in the revolution speed with
respect to a fluctuation in the target drive power on the speed
shift line is lower than a sensitivity of a fluctuation in the
revolution speed with respect to the fluctuation in the target
drive power on the optimal fuel consumption line.
[0012] The aforementioned construction prevents great fluctuations
in the revolution speed of the engine even if the output of the
engine fluctuates in accordance with the target drive power within
the practical region. Therefore, the fuel consumption resulting
from inertia torques caused by fluctuations in the engine
revolution speed, that is, fluctuations in the revolution speed of
the input shaft of the transmission, is reduced, so that the
efficiency as a whole increases and the fuel economy improves in
comparison with the case where the optimal fuel consumption line is
used as a control basis.
[0013] The drive power control apparatus may further have a
construction wherein the engine comprises a NOx storage-reduction
type catalyst in an exhaust system, and during the lean combustion,
the engine reduces NOx stored in the NOx storage-reduction type
catalyst by performing a rich spike control of temporarily changing
an air-fuel mixture so that a fuel concentration in the mixture
becomes higher than the fuel concentration corresponding to a
stoichiometric air-fuel ratio, and wherein on a boundary line
between the lean combustion and the stoichiometric air-fuel ratio
combustion in the two-dimensional space of the revolution speed of
the engine and the torque of the engine, the speed shift line
passes through or near a point at which a corrected fuel
consumption rate determined by considering the rich spike control
and a fuel consumption rate provided during the lean combustion
becomes equal to or closest to a fuel consumption rate provided
during the stoichiometric air-fuel ratio combustion.
[0014] If the selectable forms of combustion includes a
stoichiometric air-fuel ratio combustion and a lean combustion and
the rich spike control is performed during the lean combustion, the
speed shift line is set so that the point which exists on the
boundary line between the lean combustion and the stoichiometric
air-fuel ratio combustion and through which the speed shift line
passes coincides with or exists near the point at which the
corrected fuel consumption rate determined by considering the rich
spike control and the fuel consumption rate provided during the
lean combustion becomes equal to or closest to the fuel consumption
rate provided during the stoichiometric air-fuel ratio combustion.
This makes it possible to maintain a state of good fuel consumption
rate even when the form of combustion changes between the lean
combustion and the stoichiometric air-fuel ratio combustion in
accordance with the speed shift line. Thus, the changing between
the forms of combustion is optimized, so that fuel economy can be
further improved.
[0015] In a vehicle drive control method in accordance with another
mode of the invention, a target output of the engine for achieving
a target drive power set based on a state of operation of the
vehicle is calculated. Furthermore, a target revolution speed of
the engine is set based on a speed shift line that is plotted on a
graph having a pair of axis defining a revolution speed of the
engine and the target output of the engine so that, within a
practical region in which the state of operation of the engine is
practical, a width of increase in the revolution speed of the
engine to a relatively high revolution speed on the speed shift
line is curbed compared with an optimal fuel consumption line
determined based on at least an efficiency of the engine and an
efficiency of the transmission, of an efficiency of a drive system
that includes the engine and the transmission. Then, the speed
ratio of the transmission is controlled so that an actual
revolution speed of the engine becomes equal to the target
revolution speed.
[0016] According to this mode of the invention, the fuel
consumption resulting from inertia torques caused by fluctuations
in the engine revolution speed, that is, fluctuations in the
revolution speed of the input shaft of the transmission, is
reduced, so that the efficiency as a whole increases and the fuel
economy improves in comparison with the case where the optimal fuel
consumption line is used as a control basis.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] The foregoing and further objects, features and advantages
of the present invention will become apparent from the following
description of preferred embodiments with reference to the
accompanying drawings, wherein like numerals are used to represent
like elements and wherein:
[0018] FIG. 1 is a schematic block diagram of a drive system and a
control system of a motor vehicle in accordance with Embodiment
1;
[0019] FIG. 2 is a schematic diagram illustrating a construction of
an engine in accordance with Embodiment 1;
[0020] FIG. 3 is a horizontal sectional view of a cylinder head in
the engine in Embodiment 1;
[0021] FIG. 4 is a plan view of a top surface of a piston in the
engine in Embodiment 1;
[0022] FIG. 5 is a section taken on line V-V in FIG. 3;
[0023] FIG. 6 is a section taken on line VI-VI in FIG. 3;
[0024] FIG. 7 is a block diagram illustrating a construction of an
E-ECU in Embodiment 1;
[0025] FIG. 8 is a block diagram illustrating a construction of an
T-ECU in Embodiment 1;
[0026] FIG. 9 illustrates a speed shift line CV that is used in
Embodiment 1;
[0027] FIG. 10 is a control block diagram of a coordinate control
portion performed by the E-ECU and the T-ECU in Embodiment 1;
[0028] FIG. 11 is a diagram illustrating a one-dimensional map for
calculating the target engine revolution speed NEt from the target
output P, which is provided for realizing the speed shift line CV
shown in FIG. 9;
[0029] FIG. 12 is a diagram illustrating relationships between fuel
consumption rates in the forms of combustion and the speed shift
line CV used in Embodiment 1;
[0030] FIG. 13 is a flowchart illustrating a fuel injection amount
control process executed by the E-ECU in Embodiment 2;
[0031] FIG. 14 is a flowchart illustrating a rich spike execution
flag Fnox setting process executed by E-ECU in Embodiment 2;
[0032] FIG. 15 is a diagram illustrating the construction of a
speed shift line CV used in Embodiment 2;
[0033] FIG. 16 is a graph indicating changes in the fuel
consumption rate caused by a rich spike control in Embodiment
2;
[0034] FIG. 17 is a diagram illustrating the construction of a
speed shift line CV in another embodiment of the invention;
[0035] FIG. 18 is a diagram illustrating the construction of a
speed shift line CV in still another embodiment of the
invention;
[0036] FIG. 19 is a diagram illustrating the construction of a
conventional speed shift line; and
[0037] FIG. 20 is a diagram illustrating the efficiency of a
continuously variable transmission.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0038] FIG. 1 is a schematic block diagram of a drive system and a
control system for a motor vehicle to which the invention is
applied.
[0039] An engine 2 as a power source is connected to a transmission
mechanism 3. An output shaft 3a of the transmission mechanism 3 is
connected to right and left-side drive wheels 5 via a differential
4. FIG. 2 schematically shows a construction of the engine 2. The
engine 2 is a direct injection type gasoline engine that is
installed as a vehicle-driving engine in a motor vehicle. The
engine 2 has six cylinders 2a. As shown in FIGS. 3 to 6, each
cylinder 2a has a combustion chamber 10 that is defined by a
cylinder block 6, a piston 7 disposed for reciprocating movements
within the cylinder block 6, and a cylinder head 8 mounted on the
cylinder block 6.
[0040] Each combustion chamber 10 is provided with a first intake
valve 12a, a second intake valve 12b, and a pair of exhaust valves
16. The first intake valve 12a is connected to a first intake port
14a. The second intake valve 12b is connected to a second intake
port 14b. The two exhaust valves 16 are connected to two exhaust
ports 18, respectively.
[0041] FIG. 3 is a horizontal sectional view of a portion of the
cylinder head 8 corresponding to one of the cylinders. As shown in
FIG. 3, the first intake port 14a and the second intake port 14b of
each cylinder are straight intake ports that extend substantially
linearly. An ignition plug 20 is disposed in a central portion of
an inner wall surface of the cylinder head 8. A fuel injection
valve 22 is disposed in a peripheral portion of an inner wall
surface of the cylinder head 8 that is adjacent to both the first
intake valve 12a and the second intake valve 12b. Each fuel
injection valve 22 is disposed so that fuel can be injected
therefrom directly into the combustion chamber 10.
[0042] FIG. 4 is a plan view of a stop surface of one of the
pistons 7. FIG. 5 is a section taken on line V-V in FIG. 3. FIG. 6
is a section taken on line VI-VI in FIG. 3. As shown in the
drawings, a generally ridge-shaped top face of the piston 7 has a
recess 24 having an inverted dome-like contour which extends from a
site below the fuel injection valve 22 to a site below the ignition
plug 20.
[0043] As shown in FIG. 2, the first intake ports 14a of the
cylinders 2a are connected to a surge tank 32 via first intake
passages 30a formed in an intake manifold 30. The second intake
ports 14b are connected to the surge tank 32 via second intake
passages 30b. An airflow control valve 34 is disposed within each
second intake passage 30b. The airflow control valves 34 are
interconnected via a common shaft 36, and are opened and closed via
the shaft 36 by a negative pressure actuator 37. When the airflow
control valves 34 are closed, intake air is introduced via only the
first intake ports 14a, and form strong swirls S (FIG. 3) within
the combustion chambers 10.
[0044] The surge tank 32 is connected to an air cleaner 42 via an
intake duct 40. A throttle valve 46 driven by an electric motor 44
(a DC motor or a stepping motor) is disposed in the intake duct 40.
The degree of opening of the throttle valve 46 (degree of throttle
opening TA) and the completely closed state of the throttle valve
46 (complete closure signal IDL) are detected by a throttle opening
sensor 46a. The degree of opening of the throttle valve 46 is
controlled in accordance with the state of operation. The exhaust
ports 18 of the cylinders 2a are connected to an exhaust manifold
48. The exhaust manifold 48 discharges exhaust gas, via a catalytic
converter 49 that controls the emission.
[0045] Referring back to FIG. 1, the above-described engine 2 is
electrically controlled by an engine-controlling electronic control
unit (hereinafter, referred to as "E-ECU") 60 that is mainly formed
by a microcomputer. As described below, the E-ECU 60 receives
inputs of signals and detected values corresponding to the engine
revolution speed NE, the accelerator operation amount ACCP, etc.,
so as to control the engine 2.
[0046] The transmission mechanism 3 has a fluidic power transfer
mechanism 62 and a continuously variable transmission (hereinafter,
referred to as "CVT") 64. The fluidic power transfer mechanism 62
is a mechanism that transfers torque between the side of an input
shaft 62c and the side of an output shaft 62d via a fluid such as
an oil or the like. In this embodiment, the fluidic power transfer
mechanism 62 is a torque converter. The fluidic power transfer
mechanism 62 has a lockup mechanism 62a. The lockup mechanism 62a
is a clutch mechanism that directly interlocks the input shaft 62c
side and the output shaft 62d side via a mechanical means such as a
friction plate or the like. The lockup mechanism 62a has, for a
buffering purpose, a damper 62b that is formed by an elastic body
such as coil spring or the like.
[0047] The input shaft 62c of the fluidic power transfer mechanism
62 is connected to a crankshaft of the engine 2. The output shaft
62d of the fluidic power transfer mechanism 62 is connected to an
input shaft 64a of the CVT 64. The CVT 64 is a transmission
mechanism capable of steplessly (continuously) varying the ratio
between the rotation speed of the input shaft 64a and the rotation
speed of an output shaft 64b, that is, the speed ratio. In this
embodiment, the CVT 64 is a belt type continuously variable
transmission. The CVT 64 incorporates a gear transmission mechanism
for accomplishing a reverse drive function, and may further
incorporate a gear transmission mechanism for expanding the width
of speed ratio if necessary.
[0048] A control of the changing between engagement (locked-up
state) and disengagement (unlocked state) of the lockup mechanism
62a of the transmission mechanism 3, and a control of the speed
ratio of the CVT 64 are performed by a transmission
mechanism-controlling electronic control unit (hereinafter,
referred to as "T-ECU") 66 in accordance with the state of running
of the vehicle.
[0049] The T-ECU 66 is connected to the E-ECU 60 in a data
transmission capable manner, and receives inputs of signals and
detected values corresponding to the hydraulic pressure for driving
the lockup mechanism 62a, the rotation speeds NP, NS of pulleys of
the CVT 64, etc., as data for control. The T-ECU 66 also receives
inputs of shift signals for selecting one of states of the CVT 64,
that is, a stopped state (parking P), a reverse drive state
(reverse R), a neutral state (neutral N), an automatic transmission
mode (drive D) that is an automatic forward drive state in which
the speed ratio is automatically set in accordance with the state
of running of the vehicle, and a manual transmission mode (manual
M) that is a manual sate in which the transmission state is
manually set.
[0050] A construction of the E-ECU 60 is illustrated in the block
diagram of FIG. 7. The E-ECU 60 is a control unit for controlling
the engine 2, for example, performing a throttle opening degree
control, a fuel injection control, an ignition timing control, an
idle speed control, etc. The E-ECU 60 is formed as a logic circuit
having a CPU 60a, a ROM 60b, a RAM 60c, a backup RAM 60d, etc. The
ROM 60b is a memory that pre-stores various control programs, data,
such as map or the like, for reference during execution of the
various programs. Based on the various programs and data stored in
the ROM 60b, the CPU 60a executes various operations. The RAM 60c
is a memory for temporarily storing results of operations of the
CPU 60a, data or the like obtained from outputs of various sensors.
The backup RAM 60d is a non-volatile memory for storing data that
needs to be retained during stop of the engine 2. The CPU 60a, the
ROM 60b, the RAM 60c and the backup RAM 60d are interconnected by a
bus 60e, and are also connected to an external input circuit 60f
and an external output circuit 60g via the bus 60e. The external
input circuit 60f is connected to a vehicle speed sensor 68 for
detecting the vehicle speed V, an engine speed sensor 70 for
detecting the engine revolution speed NE, the throttle opening
sensor 46a, an accelerator depression sensor 74 for detecting the
accelerator operation amount ACCP, that is, the amount of
depression of an accelerator pedal 72, an intake pressure senor 76
for detecting the intake pressure PM in the surge tank 32, an
air-fuel ratio sensor 78 for detecting the air-fuel ratio A/F based
on exhaust components, a water temperature sensor 80 for detecting
the cooling water temperature THW of the engine 2, a stop lamp
switch 84 for detecting whether a brake pedal 82 (FIG. 2) has been
depressed, etc. The external output circuit 60g is connected to the
throttle valve-driving motor 44, the fuel injection valve 22 of
each cylinder of the engine 2, the negative pressure actuator 37,
an igniter (not shown), and other actuators, which are driven when
necessary.
[0051] A construction of the T-ECU 66 is shown in the block diagram
of FIG. 8. The T-ECU 66 is a control unit that performs an
automatic transmission operation by controlling the lockup
mechanism 62a and the CVT 64. The T-ECU 66 is formed as a logic
circuit having a CPU 66a, a ROM 66b, a RAM 66c, a backup RAM 66d, a
bus 66e, an external input circuit 66f, an external output circuit
66g, etc. These components 66a to 66g perform basically the same
functions as those in the E-ECU 60. The external input circuit 66f
is connected to a shift device 88 that outputs the aforementioned
shift signal SHFT, a primary pulley rotation sensor 89a for
detecting the rotation speed NP of the primary pulley in the CVT
64, a secondary pulley rotation sensor 89b for detecting the
rotation speed NS of the secondary pulley in the CVT 64, a
hydraulic pressure sensor 90 for detecting the hydraulic pressure
for driving the lockup mechanism 62a, and other sensors and the
like. The external output circuit 66g is connected to a speed shift
actuator 92 for changing the speed ratio by driving the primary
pulley and the second pulley in the CVT 64, a lockup actuator 94
for switching the lockup mechanism 62a of the fluidic power
transfer mechanism 62, and other actuators and the like. The T-ECU
66 is connected in terms of signals to the E-ECU 60 via the
external input circuit 66f and the external output circuit 66g, for
mutual communications with the E-ECU 60.
[0052] When the automatic transmission mode D is selected, the
E-ECU 60 and the T-ECU 66 constructed as described above perform a
coordinate control so as to generate an appropriate drive power on
the drive wheels 5 in accordance with a drive power requested by an
operating person via the accelerator pedal 72 or the like. More
specifically, the E-ECU 60 adjusts one or more of the amount of
intake air, the amount of fuel injection, and the form of
combustion so as to provide the fuel economy and the engine output
torque needed to achieve the requested drive power. The T-ECU 66
adjusts the speed ratio so as to achieve an engine revolution speed
NE that is needed to achieve a requested drive power.
[0053] With regard to the form of combustion in Embodiment 1, one
of a stratified charge combustion, a uniform combustion and a weak
stratified charge combustion is selected in accordance with the
state of operation. In the stratified charge combustion mode, fuel
is injected into each combustion chamber 10 from the corresponding
fuel injection valve 22 during a late period in the compression
stroke so that a stratified mixture with high fuel concentration is
formed, and is ignited. In the uniform combustion, fuel is injected
into each combustion chamber 10 from the corresponding fuel
injection valve 22 during the intake stroke so that a uniform
mixture is formed, and is then ignited. In the weak stratified
charge combustion, fuel is injected both during the intake stroke
and during a late period in the compression stroke so that a
stratified mixture is formed in a uniform and lean mixture, and is
ignited. FIG. 9 indicates regions of the forms of combustion that
are expressed in a two-dimensional space based on the engine
revolution speed NE and the engine torque T. In FIG. 9, broken
lines represent constant output lines, and a bent solid line
represents a speed shift line CV used in Embodiment 1.
[0054] During the stratified charge combustion mode, injected fuel
provided by injection performed during the late period of the
compression stroke moves from the fuel injection valve 22 into the
recess 24 of the piston 7 in each cylinder, and then strikes a
peripheral wall surface 26 (see, e.g., FIGS. 4, 5). Upon striking
the peripheral wall surface 26, fuel moves while vaporizing, and
forms a combustible mixture layer in the recess 24 adjacent to the
ignition plug 20. The stratified combustible mixture is ignited by
the ignition plug 20, thereby accomplishing stratified charge
combustion. In this manner, stable combustion can be accomplished
in each combustion chamber 10 with intake air existing in an
extremely excess amount relative to fuel.
[0055] During the uniform combustion, an amount of fuel corrected
in various manners based on a stoichiometric air-fuel ratio basic
fuel injection amount QBS is injected during the intake stroke. The
injected fuel flows into each combustion chamber 10 together with
inflowing intake air, and continues flowing until ignition.
Therefore, a uniform mixture of the stoichiometric air-fuel ratio
(in some cases, the air-fuel ratio is controlled to a rich air-fuel
ratio that means a higher fuel concentration than the
stoichiometric air-fuel ratio, due to an increasing correction) is
formed in the entire combustion chamber 10, so that the uniform
combustion is accomplished.
[0056] During the weak stratified charge combustion mode, fuel
injected by the first injection flows into the combustion chamber
10 together with intake air, thereby forming a uniform lean mixture
in the entire combustion chamber 10. Then, the second fuel
injection performed at a late time in the compression stroke, so
that a combustible mixture layer is formed within the recess 24 in
the vicinity of the ignition plug 20 as mentioned above. The
stratified combustible mixture is ignited by the ignition plug 20,
and ignited flame bums the lean mixture existing in the entire
combustion chamber 10. In this manner, stratified charge combustion
with a weak degree of stratification is accomplished, so that a
smooth torque change can be realized in an intermediate region
between the stratified charge combustion and the uniform
combustion.
[0057] The coordinate control performed when the automatic
transmission mode D is selected will next be described in detail
with reference to the control block diagram of FIG. 10. In the
below description, B1 to B6 parenthesized represent blocks shown in
FIG. 10. The blocks B3, B4 correspond to processes performed by the
T-ECU 66. The other blocks correspond to processes performed by the
E-ECU 60.
[0058] First, a target drive power F is set based on the
accelerator operation amount ACCP and the vehicle speed V (B1). The
vehicle speed V may be substituted with, for example, the rotation
speed of a different rotating member that has a corresponding
relation with the vehicle speed.
[0059] The setting of the target drive power F based on the
accelerator operation amount ACCP and the vehicle speed V is
performed based on a map pre-stored in the ROM 60b. More
specifically, a relationship between the vehicle speed V and the
target drive power F is pre-set as a map using the accelerator
operation amount ACCP as a parameter. This map is used. In the
setting of the map, the target drive power F is determined so as to
reflect characteristics of the object vehicle or engine 2 or the
like.
[0060] Next, based on the determined target drive power F and the
vehicle speed V or a detected value corresponding to the vehicle
speed, a target output P is calculated (B2). More specifically, the
target output P can be calculated as a product of the target drive
power F and the vehicle speed V as in Equation (1).
P.rarw.F.times.V (1)
[0061] The thus-calculated target output P is used to calculate a
target engine revolution speed NEt (B3).
[0062] In the block B3, a target engine revolution speed NEt is
calculated from the target output P, with reference to a
one-dimensional map as indicated by a solid line in FIG. 11 which
is pre-stored in the ROM 66b of the T-ECU 66. If a speed shift line
CV is set in a two-dimensional space of the engine revolution speed
NE and the engine torque T as indicated in FIG. 9, an engine
revolution speed NE can be independently determined in accordance
with the output. Therefore, a one-dimensional map for determining
the target engine revolution speed NEt by using the target output P
as a parameter as indicated by the solid line in FIG. 11 can be set
from the speed shift line CV shown in FIG. 9.
[0063] Then, the speed shift control of the CVT 64 is performed so
that the present actual engine revolution speed NE becomes equal to
the target engine revolution speed NEt (B4).
[0064] It is to be noted herein that the engine revolution speed NE
and the primary pulley rotation speed NP have a relationship of
equivalence. Therefore, in the aforementioned speed shift control
of the CVT 64, the CVT 64 can be controlled by using the primary
pulley rotation speed NP instead of the engine revolution speed NE.
The blocks B3, B4 are processes performed by the T-ECU 66. In
reality, therefore, the T-ECU 66 may control the CVT 64 by handling
the target primary pulley rotation speed NPt for the target engine
revolution speed NEt, and handling the actual primary pulley
rotation speed NP for the actual engine revolution speed NE.
[0065] In a flow different from the above-described flow, a target
engine torque T0 is calculated from the target output P calculated
in the block B2 (B5). More specifically, the target engine torque
T0 is calculated by dividing the target output P by the present
actual engine revolution speed NE as in Equation (2).
[0066] It is also practicable to substitute the actual engine
revolution speed NE with the actual primary pulley rotation speed
NP in calculating target engine torque T0. The target engine torque
T0 may also be calculated by using the aforementioned target engine
revolution speed NEt (target primary pulley rotation speed
NPt).
T0.rarw.30.circle-solid.P/(.pi..circle-solid.NE) (2)
[0067] The engine torque is controlled so that the actual engine
torque reaches the calculated target engine torque T0 (B6). More
specifically, the amount of fuel injection and the amount of intake
air are adjusted so that the target engine torque T0 is reached. If
the present form of combustion is the stratified charge combustion
or the weak stratified charge combustion, the engine torque is
adjusted based on the amount of fuel injected. If the present form
of combustion is the uniform combustion, the engine torque is
adjusted based on the amount of intake air, that is, the degree of
opening of the throttle valve 46 (degree of throttle opening
TA).
[0068] Due to the processes as in the blocks B1 to B6, the speed
ratio of the CVT 64 is adjusted along the speed shift line CV shown
in FIG. 9.
[0069] Relationships between the speed shift line CV and the fuel
consumption rates provided by the forms of combustion is indicated
in FIG. 12. In FIG. 12, elliptical broken lines represent constant
fuel consumption rate lines. A comparative example indicated by
one-dot chain lines in FIGS. 11 and 12 represents a case in which
an optimal fuel consumption line determined based on the efficiency
of the engine 2 and the efficiency of the CVT 64 is set as a speed
shift line. As can be understood from FIGS. 11 and 12, the speed
shift line CV of Embodiment 1 is set on a low engine speed side of
the optimal fuel consumption line, as far as a practical region is
concerned. Furthermore, the speed shift line CV is set so that,
within the practical region, the difference between the minimum
engine revolution speed NEmin and the maximum engine revolution
speed NEmax on the speed shift line CV is smaller than the
difference between the minimum engine revolution speed on the
optimal fuel consumption line (equal to NEmin) and the maximum
engine revolution speed NEZ on the optimal fuel consumption line.
Still further, the speed shift line CV is set so that, within the
practical region, the sensitivity of revolution speed fluctuation
with respect to fluctuation in the target drive power F based on
the speed shift line CV is lower than the sensitivity based on
optimal fuel consumption line.
[0070] In the above-described construction, the processes of the
blocks B3, B4 correspond to the operations as a speed ratio control
means.
[0071] Embodiment 1 constructed as described above achieves the
following advantages.
[0072] As indicated in FIGS. 11 and 12, the speed ratio of the CVT
64 is controlled in accordance with the speed shift line (solid
line) that is set so that, within the practical region, the speed
shift line is located on the low engine speed side of the optimal
fuel consumption line (one-dot chain line) determined based on the
efficiency of the engine 2 and the efficiency of the CVT 64.
Therefore, the width of increase in the engine revolution speed
from the level at the beginning of the practical region is curbed.
Hence, the fuel consumption resulting from inertia torques caused
by fluctuations in the revolution speed of the engine 2, that is,
revolution speed fluctuations of the input shaft of the CVT 64 and
the input shaft of the fluidic power transfer mechanism 62, is
reduced, so that the efficiency as a whole increases and the fuel
economy improves in comparison with the case where the optimal fuel
consumption line is used as a control basis.
[0073] Furthermore, within the practical region, the difference
between the maximum engine revolution speed NEmax and the minimum
engine revolution speed NEmin on the speed shift line is smaller
than the difference between the maximum engine revolution speed NEZ
and the minimum engine revolution speed (equal to NEmin) on the
optimal fuel consumption line. Therefore, great fluctuations in the
engine revolution speed NE of the engine 2 are substantially
prevented even if the target drive power F fluctuates in the
practical region. Hence, the fuel consumption resulting from
inertia torques caused by fluctuations in the revolution speed of
the engine 2, that is, revolution speed fluctuations of the input
shaft of the CVT 64 and the input shaft of the fluidic power
transfer mechanism 62, is reduced, so that the efficiency as a
whole increases and the fuel economy improves in comparison with
the case where the optimal fuel consumption line is used as a
control basis.
[0074] Furthermore, in the practical region, the speed shift line
is set so that the rising of target engine revolution speed NEt is
delayed with respect to the rising of the target output P of the
engine 2. That is, the speed shift line is set so that, in the
practical region, the sensitivity of fluctuation in engine
revolution speed with respect to fluctuation in the target drive
power F based on the speed shift line is lower than the sensitivity
based on the optimal fuel consumption line. Therefore, great
fluctuations in the engine revolution speed NE are prevented even
if the target drive power F fluctuates in the practical region.
Hence, the fuel consumption resulting from inertia torques caused
by fluctuations in the revolution speed of the engine 2, that is,
revolution speed fluctuations of the input shaft of the CVT 64 and
the input shaft of the fluidic power transfer mechanism 62, is
reduced, so that the efficiency as a whole increases and the fuel
economy improves in comparison with the case where the optimal fuel
consumption line is used as a control basis.
[0075] The speed shift line CV in Embodiment 1 is set so as to
define a relationship in which in all the forms of combustion, as
the engine torque T increases, the engine revolution speed NE
remains constant or increases. Therefore, even in a portion of the
practical region, a great fluctuation in the engine speed in
response to a small fluctuation in the target drive power F is
prevented, so that the aforementioned fuel efficiency improvement
becomes more remarkable.
[0076] Embodiment 2 of the invention will next be described.
[0077] In Embodiment 2, a NOx storage-reduction type catalyst 99 is
incorporated in a catalytic converter 49 shown in FIG. 2, which
shows Embodiment 1. The E-ECU 60 performs a rich spike control by
performing a fuel injection amount control process illustrated in
the flowchart of FIG. 13 and a process of setting a rich spike
execution flag Fnox illustrated in the flowchart of FIG. 14. In
conjunction with the rich spike control, a speed shift line CV is
set as indicted in FIG. 15. Other constructions of Embodiment 2 are
substantially the same as those of Embodiment 1. In the following
description, the hardware construction of Embodiment 2 should be
apparent from the aforementioned drawings of Embodiment 1 and the
reference characters representing the component parts and the
like.
[0078] The fuel injection amount control process will be described
with reference to FIG. 13. This process is cyclically executed by
every pre-set crank angle.
[0079] When fuel injection amount control process starts, the E-ECU
60 inputs various engine operation state data, such as the
accelerator operation amount ACCP, the engine revolution speed NE,
the intake pressure PM, the cooling water temperature THW, the
air-fuel ratio A/F, etc., into work areas in the RAM 60c
(S110).
[0080] Subsequently, the E-ECU 60 determines whether the rich spike
execution flag Fnox is "OFF" (S120). If Fnox="OFF" ("YES" in S120),
the E-ECU 60 selects and executes a form of combustion in
accordance with the operation state, that is, one of the stratified
charge combustion, the uniform combustion and the weak stratified
charge combustion, as described above in conjunction with
Embodiment 1 (S130). Then, the E-ECU 60 temporarily ends the
process.
[0081] Conversely, if Fnox="ON" ("NO" in S120), the E-ECU 60
performs the rich spike control (S140). More specifically, the
E-ECU 60 performs a process of shifting the air-fuel ratio A/F to
the rich side (e.g., A/F=11.5) by temporarily increasing the amount
of fuel injected from the fuel injection valves 22. When the rich
spike control process is performed in this manner, unburned gas is
produced in exhaust, and is supplied as a reducing agent to the
catalytic converter 49, so that NOx in the NOx storage-reduction
type catalyst 99 is reduced.
[0082] After that, the E-ECU 60 temporarily ends the process.
[0083] The rich spike execution flag Fnox setting process will be
described with reference to the flowchart of FIG. 14. The rich
spike execution flag Fnox setting process is cyclically executed at
every pre-set crank angle.
[0084] First, the E-ECU 60 determines whether the lean combustion
(the stratified charge combustion or the weak stratified charge
combustion) is being performed (S210). If the lean combustion is
being performed ("YES" in S210), the E-ECU 60 calculates an added
amount of NOx that is produced by the lean combustion and is stored
into the NOx storage-reduction type catalyst 99, based on the
relationship between the intake pressure PM and the amount of fuel
injected from each fuel injection valve 22 by the fuel injection
amount control process. The E-ECU 60 then increases the amount of
NOx stored sNOx calculated in the previous control cycle by the
added amount of NOx to determine a new amount of NOx stored sNOx
(S220).
[0085] Subsequently, the E-ECU 60 determines whether the amount of
NOx stored sNOx has exceeded an allowable storage value NOxCAP
(S230). If sNOx.ltoreq.NOxCAP ("NO" in S230), the E-ECU 60
temporarily ends the process without performing any further
processing.
[0086] If sNOx>NOxCAP ("YES" in S230), the E-ECU 60 subsequently
sets "ON" in the rich spike execution flag Fnox (S240). Then, the
E-ECU 60 temporarily ends the process.
[0087] When the uniform combustion is being executed instead of the
lean combustion ("NO" in S210), the E-ECU 60 calculates an amount
of NOx that is reduced by unburned gas after being stored in the
NOx storage-reduction type catalyst 99, based on the relationship
between the intake pressure PM and the amount of fuel injected from
each fuel injection valve 22 by the fuel injection amount control
process. The E-ECU 60 then decreases the amount of NOx stored sNOx
calculated during the previous control cycle by the amount of NOx
reduced, thereby determining a new amount of NOx stored sNOx
(S250).
[0088] Subsequently, the E-ECU 60 determines whether the amount of
NOx stored sNOx is at most "0" (S260). If sNOx.ltoreq.0 ("YES" in
S260), the E-ECU 60 sets "0" as the amount of NOx stored sNOx
(S270), and then sets "OFF" in the rich spike execution flag Fnox
(S280). Subsequently, the E-ECU 60 temporarily ends the process. If
sNOx>0 ("NO" in S260), the E-ECU 60 temporarily ends the process
without performing any further processing.
[0089] Considering the rich spike control performed during the
stratified charge combustion and during the weak stratified charge
combustion, it can be understood that the fuel economy slightly
deteriorates during the stratified charge combustion and the weak
stratified charge combustion with the rich spike control in
comparison with a case where the stratified charge combustion and
the weak stratified charge combustion are simply performed without
the rich spike control.
[0090] Therefore, as indicated in FIG. 16 illustrating
relationships between the fuel consumption rate and the output with
the engine revolution speed NE being fixed, the point of equality
C2 between the fuel consumption rate in the uniform combustion and
the fuel consumption rate in the weak stratified charge combustion
with the rich spike control is shifted to the low output side of
the point of equality C1 between the fuel consumption rate in the
uniform combustion and the fuel consumption rate in the weak
stratified charge combustion without the rich spike control.
[0091] In Embodiment 2, the speed shift line CV is set so that,
within the practical region, the speed shift line CV is located on
the low engine speed side of the optimal fuel consumption line
determined based on the efficiency of the engine 2 and the
efficiency of the CVT 64. As indicated in FIG. 15, the speed shift
line CV is set in the aforementioned setting so as to pass through
the point of equality C2 of fuel consumption rate on a boundary
line B between the uniform combustion and the weak stratified
charge combustion.
[0092] If an appropriate point of equality C2 does not exist on the
boundary line B between the uniform combustion and the weak
stratified charge combustion in the low engine speed side of the
optimal fuel consumption line, a speed shift line CV is set so as
to pass through a point at which the fuel consumption rate in the
uniform combustion and the fuel consumption rate in the weak
stratified charge combustion are closest to each other, or is set
so as to cross on the boundary line B between the uniform
combustion and the weak stratified charge combustion, in the
vicinity of the point of equality C2 or in the vicinity of the
point of greatest proximity.
[0093] Embodiment 2, constructed as described above, achieves
substantially the same advantages as those of Embodiment 1.
[0094] The point which exists on the boundary line B between the
stratified charge combustion and the uniform combustion and through
which the speed shift line CV passes is set to a point of equality
or greatest proximity between the fuel consumption rate in the
uniform combustion and the corrected fuel consumption rate
determined by taking into account the rich spike control as well as
the fuel consumption rate in the weak stratified charge combustion,
or is set in the vicinity of the point of equality or greatest
proximity.
[0095] More specifically, as indicated in FIG. 16, a fuel
consumption rate line with good fuel consumption rate can be
obtained by setting the speed shift line CV so as to extend through
the point C2 in a region where the form of combustion is switched
from the stratified charge combustion to the uniform combustion.
Therefore, it becomes possible to change the speed ratio while
always maintaining good fuel consumption rate. As a result, fuel
economy can be improved.
[0096] Although in the foregoing embodiments, the speed shift line
CV is a sharply bent line, the speed shift line CV may also be a
line that curves and extends toward the low engine speed side in
the practical region. See, e.g., FIG. 17.
[0097] Although in the foregoing embodiments, the CVT 64 is a belt
type continuously variable transmission, the CVT 64 may also be a
toroidal type continuously variable transmission or the like.
[0098] In the foregoing embodiments, the lean combustion is
performed in the form of the stratified charge combustion or the
weak stratified charge combustion. However, the lean combustion may
also be performed in other forms, for example, in the form of
generally termed "lean burn", that is, a uniform lean combustion in
which fuel is uniformly mixed with intake air at a ratio that is on
the lean side of the stoichiometric air-fuel ratio and such a
uniform mixture is ignited.
[0099] In the foregoing embodiments, the speed shift line CV is a
speed shift line CV for a motor vehicle in which a direct injection
type gasoline engine is installed and the form of combustion in the
engine is changed. The speed shift line CV in the invention is also
applicable to a speed shift line CV for a motor vehicle in which an
intake port injection type engine is installed and the possible
form of combustion is only the uniform combustion at the
stoichiometric air-fuel ratio as indicated in FIG. 18. In the case
where the form of combustion is fixed, too, engine revolution speed
fluctuation is reduced, so that the fuel consumption caused by
inertia torques is reduced. As a result, the efficiency as a whole
increases and fuel economy improves in comparison with the case
where the optimal fuel consumption rate line is used as a control
basis.
[0100] While the embodiments of the invention have been described,
the invention further includes, for example, the following
embodiments.
[0101] In a vehicle that is driven by output of an internal
combustion engine via a continuously variable transmission, a
vehicle drive power control apparatus which determines a target
drive power based on a state of operation of the vehicle, and which
controls the torque of the engine and the speed ratio of the
continuously variable transmission so as to provide an output of
the engine for achieving the target drive power, the drive power
control apparatus including a controller that controls the speed
ratio of the continuously variable transmission in accordance with
a speed shift line that is set in a two-dimensional space of the
revolution speed of the engine and the torque of the engine. The
speed is possible to set in the following way.
[0102] The speed shift line is, with a practical region, at a low
revolution speed side of an optimal fuel consumption line that is
determined based on an efficiency of the entire drive system that
includes the engine and the continuously variable transmission.
[0103] The difference between the minimum revolution speed and the
maximum revolution speed on the speed shift line is, with a
practical region, smaller than the difference between the minimum
revolution speed and the maximum revolution speed on an optimal
fuel consumption rate line that is determined based on the
efficiency of the entire drive system that includes the engine and
the continuously variable transmission.
[0104] The sensitivity of revolution speed fluctuation with respect
to fluctuation in the target drive power is, with a practical
region, lower on the speed shift line than on an optimal fuel
consumption line determined based on the efficiency of the entire
drive system that includes the engine and the continuously variable
transmission.
[0105] In the illustrated embodiment, the T-ECU 66 and the E-ECU 60
are implemented as a programmed general purpose computer. It will
be appreciated by those skilled in the art that the controller can
be implemented using a single special purpose integrated circuit
(e.g., ASIC) having a main or central processor section for
overall, system-level control, and separate sections dedicated to
performing various different specific computations, functions and
other processes under control of the central processor section. The
controller can be a plurality of separate dedicated or programmable
integrated or other electronic circuits or devices (e.g., hardwired
electronic or logic circuits such as discrete element circuits, or
programmable logic devices such as PLDs, PLAs, PALs or the like).
The controller can be implemented using a suitably programmed
general purpose computer, e.g., a microprocessor, microcontroller
or other processor device (CPU or MPU), either alone or in
conjunction with one or more peripheral (e.g., integrated circuit)
data and signal processing devices. In general, any device or
assembly of devices on which a finite state machine capable of
implementing the procedures described herein can be used as the
controller. A distributed processing architecture can be used for
maximum data/signal processing capability and speed.
[0106] While the invention has been described with reference to
preferred embodiments thereof, it is to be understood that the
invention is not limited to the preferred embodiments or
constructions. To the contrary, the invention is intended to cover
various modifications and equivalent arrangements. In addition,
while the various elements of the preferred embodiments are shown
in various combinations and configurations, which are exemplary,
other combinations and configurations, including more, less or only
a single element, are also within the spirit and scope of the
invention.
* * * * *