U.S. patent application number 11/395281 was filed with the patent office on 2006-10-05 for motor vehicle and control method of motor vehicle.
This patent application is currently assigned to TOYOTA JIDOSHA KABUSHIKI KAISHA. Invention is credited to Daigo Ando, Keita Fukui, Osamu Harada, Keiko Hasegawa, Toshio Inoue, Mamoru Tomatsuri.
Application Number | 20060218896 11/395281 |
Document ID | / |
Family ID | 36999182 |
Filed Date | 2006-10-05 |
United States Patent
Application |
20060218896 |
Kind Code |
A1 |
Ando; Daigo ; et
al. |
October 5, 2006 |
Motor vehicle and control method of motor vehicle
Abstract
In a hybrid vehicle of the invention, in the event of
specification that an exhaust treatment catalyst is in a preset
adequate state at step S112, combustion control of an engine starts
after a decrease of an intake pipe pressure P to a preset reference
negative pressure Pref and reduction of an intake air flow into a
cylinder of the engine by engine motoring. In the event of
specification that the exhaust treatment catalyst is not in the
preset adequate state but in an inadequate state at step S112, on
the other hand, the combustion control of the engine immediately
starts, prior to the decrease of the intake pipe pressure P to the
preset reference negative pressure Pref. The hybrid vehicle of the
invention allows an early start of the combustion control in a
lower catalyst temperature condition that lowers the catalytic
conversion power of the exhaust treatment catalyst and in a higher
catalyst temperature condition that causes accelerated
deterioration of the exhaust treatment catalyst in exposure to the
air. The early start of the combustion control effectively reduces
the potential shocks on a start of the engine, while preventing the
potential troubles, for example, the worsened emission and the
accelerated deterioration of the exhaust treatment catalyst,
arising in the course of engine motoring due to the inadequate
state of the exhaust treatment catalyst.
Inventors: |
Ando; Daigo; (Nisshin-shi,
JP) ; Hasegawa; Keiko; (Toyota-shi, JP) ;
Harada; Osamu; (Toyota-shi, JP) ; Inoue; Toshio;
(Gotenba-shi, JP) ; Tomatsuri; Mamoru;
(Toyota-shi, JP) ; Fukui; Keita; (Susono-shi,
JP) |
Correspondence
Address: |
OLIFF & BERRIDGE, PLC
P.O. BOX 19928
ALEXANDRIA
VA
22320
US
|
Assignee: |
TOYOTA JIDOSHA KABUSHIKI
KAISHA
Toyota-shi
JP
|
Family ID: |
36999182 |
Appl. No.: |
11/395281 |
Filed: |
April 3, 2006 |
Current U.S.
Class: |
60/277 ;
60/274 |
Current CPC
Class: |
F01N 11/002 20130101;
Y02T 10/40 20130101; F02N 11/0814 20130101; Y02T 10/6239 20130101;
B60L 2240/445 20130101; B60W 20/10 20130101; B60W 2510/0671
20130101; F02D 41/18 20130101; B60W 2510/068 20130101; Y02T 10/48
20130101; B60K 6/445 20130101; B60W 10/06 20130101; Y02T 10/62
20130101; F02D 41/065 20130101; Y02T 10/47 20130101; B60W 20/00
20130101; F02D 41/0235 20130101 |
Class at
Publication: |
060/277 ;
060/274 |
International
Class: |
F01N 7/00 20060101
F01N007/00; F01N 3/00 20060101 F01N003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 4, 2005 |
JP |
2005-107429 |
Claims
1. A motor vehicle, comprising: a motoring device that is capable
of motoring an internal combustion engine; an exhaust treatment
catalyst that treats exhaust of the internal combustion engine to
convert harmful components of the exhaust into harmless components;
a catalyst state detection unit that detects a state of the exhaust
treatment catalyst; an in-cylinder air flow specification module
that specifies whether an intake air flow into a cylinder of the
internal combustion engine decreases to a preset low range; and an
internal combustion engine start control module that starts
combustion control of the internal combustion engine, in response
to requirement for a restart of the internal combustion engine,
when the state of the exhaust treatment catalyst detected by the
catalyst state detection unit is a preset adequate state, said
internal combustion engine start control module starting the
combustion control of the internal combustion engine after
specification of a decrease in intake air flow into the cylinder of
the internal combustion engine to the preset low range by said
in-cylinder air flow specification module in the course of motoring
the internal combustion engine by the motoring device, when the
state of the exhaust treatment catalyst detected by the catalyst
state detection unit is not the preset adequate state but is an
inadequate state, said internal combustion engine start control
module immediately starting the combustion control of the internal
combustion engine, prior to specification of a decrease in intake
air flow into the cylinder of the internal combustion engine to the
preset low range by said in-cylinder air flow specification module
in the course of motoring the internal combustion engine by the
motoring device.
2. A motor vehicle in accordance with claim 1, wherein the preset
low range represents a certain level of the intake air flow into
the cylinder that is equivalent to idling operation of the internal
combustion engine.
3. A motor vehicle in accordance with claim 1, said motor vehicle
further comprising: an intake pipe pressure specification module
that specifies whether an intake pipe pressure of the internal
combustion engine decreases to a preset reference negative
pressure, wherein said in-cylinder air flow specification module
specifies whether the intake air flow into the cylinder of the
internal combustion engine decreases to the preset low range, based
on a result of the specification of whether the intake pipe
pressure of the internal combustion engine decreases to the preset
reference negative pressure.
4. A motor vehicle in accordance with claim 3, wherein the preset
reference negative pressure represents a certain level of the
intake pipe pressure that is equivalent to idling operation of the
internal combustion engine.
5. A motor vehicle in accordance with claim 3, wherein said intake
pipe pressure specification module specifies whether the intake
pipe pressure of the internal combustion engine decreases to the
preset reference negative pressure, based on a specific parameter
in correlation to the intake pipe pressure of the internal
combustion engine.
6. A motor vehicle in accordance with claim 5, wherein the specific
parameter is a motoring time of the internal combustion engine by
the motoring device.
7. A motor vehicle in accordance with claim 1, wherein the catalyst
state detection unit detects the inadequate state of the exhaust
treatment catalyst, when the exhaust treatment catalyst has a
temperature in a low temperature range that allows exertion of only
an insufficient catalytic conversion power.
8. A motor vehicle in accordance with claim 1, wherein the catalyst
state detection unit detects the inadequate state of the exhaust
treatment catalyst, when the exhaust treatment catalyst has a
temperature in a high temperature range that causes quick
deterioration of the exhaust treatment catalyst by exposure to the
air.
9. A motor vehicle in accordance with claim 1, said motor vehicle
further comprising an internal combustion engine stop control
module that stops the operation of the internal combustion engine
upon satisfaction of a preset internal combustion engine auto stop
condition, wherein said internal combustion engine start control
module restarts the internal combustion engine upon satisfaction of
a preset internal combustion engine auto start condition after the
stop of the operation of the internal combustion engine by said
internal combustion engine stop control module.
10. A motor vehicle in accordance with claim 9, wherein said
internal combustion engine stop control module prohibits the stop
of the internal combustion engine when the exhaust treatment
catalyst is not in the preset adequate state during operation of
the internal combustion engine.
11. A motor vehicle, comprising: a motoring device that is capable
of motoring an internal combustion engine; an exhaust treatment
catalyst that treats exhaust of the internal combustion engine to
convert harmful components of the exhaust into harmless components;
a catalyst state detection unit that detects a state of the exhaust
treatment catalyst; an intake pipe pressure specification module
that specifies whether an intake pipe pressure of the internal
combustion engine decreases to a preset reference negative
pressure; and an internal combustion engine start control module
that starts combustion control of the internal combustion engine,
in response to requirement for a restart of the internal combustion
engine, when the state of the exhaust treatment catalyst detected
by the catalyst state detection unit is a preset adequate state,
said internal combustion engine start control module starting the
combustion control of the internal combustion engine after
specification of a decrease in intake pipe pressure of the internal
combustion engine to the preset reference negative pressure by said
intake pipe pressure specification module in the course of motoring
the internal combustion engine by the motoring device, when the
state of the exhaust treatment catalyst detected by the catalyst
state detection unit is not the preset adequate state but is an
inadequate state, said internal combustion engine start control
module immediately starting the combustion control of the internal
combustion engine, prior to specification of a decrease in intake
pipe pressure of the internal combustion engine to the preset
reference negative pressure by said intake pipe pressure
specification module in the course of motoring the internal
combustion engine by the motoring device.
12. A motor vehicle in accordance with claim 11, wherein the preset
reference negative pressure represents a certain level of the
intake pipe pressure that is equivalent to idling operation of the
internal combustion engine.
13. A motor vehicle in accordance with claim 11, wherein said
intake pipe pressure specification module specifies whether the
intake pipe pressure of the internal combustion engine decreases to
the preset reference negative pressure, based on a specific
parameter in correlation to the intake pipe pressure of the
internal combustion engine.
14. A motor vehicle in accordance with claim 13, wherein the
specific parameter is a motoring time of the internal combustion
engine by the motoring device.
15. A motor vehicle in accordance with claim 11, wherein the
catalyst state detection unit detects the inadequate state of the
exhaust treatment catalyst, when the exhaust treatment catalyst has
a temperature in a low temperature range that allows exertion of
only an insufficient catalytic conversion power.
16. A motor vehicle in accordance with claim 11, wherein the
catalyst state detection unit detects the inadequate state of the
exhaust treatment catalyst, when the exhaust treatment catalyst has
a temperature in a high temperature range that causes quick
deterioration of the exhaust treatment catalyst by exposure to the
air.
17. A motor vehicle in accordance with claim 11, said motor vehicle
further comprising an internal combustion engine stop control
module that stops the operation of the internal combustion engine
upon satisfaction of a preset internal combustion engine auto stop
condition, wherein said internal combustion engine start control
module restarts the internal combustion engine upon satisfaction of
a preset internal combustion engine auto start condition after the
stop of the operation of the internal combustion engine by said
internal combustion engine stop control module.
18. A motor vehicle in accordance with claim 17, wherein said
internal combustion engine stop control module prohibits the stop
of the internal combustion engine when the exhaust treatment
catalyst is not in the preset adequate state during operation of
the internal combustion engine.
19. A control method of a motor vehicle, comprising the steps of:
(a) detecting a state of an exhaust treatment catalyst that treats
exhaust of the internal combustion engine to convert harmful
components of the exhaust into harmless components; and (b) when
the state of the exhaust treatment catalyst detected by the step
(a) is a preset adequate state, starting the combustion control of
the internal combustion engine after specification of a decrease in
intake air flow into the cylinder of the internal combustion engine
to the preset low range, in the course of motoring the internal
combustion engine, and when the state of the exhaust treatment
catalyst detected by the step (a) is not the preset adequate state
but is an inadequate state, starting the combustion control of the
internal combustion engine, prior to specification of a decrease in
intake air flow into the cylinder of the internal combustion engine
to the preset low range in the course of motoring the internal
combustion engine.
20. A control method of a motor vehicle, comprising the steps of:
(a) detecting a state of an exhaust treatment catalyst that treats
exhaust of the internal combustion engine to convert harmful
components of the exhaust into harmless components; and (b) when
the state of the exhaust treatment catalyst detected by the step
(a) is a preset adequate state, starting the combustion control of
the internal combustion engine after specification of a decrease in
intake pipe pressure of the internal combustion engine to the
preset reference negative pressure in the course of motoring the
internal combustion engine, and when the state of the exhaust
treatment catalyst detected by the step (a) is not the preset
adequate state but is an inadequate state, starting the combustion
control of the internal combustion engine, prior to specification
of a decrease in intake pipe pressure of the internal combustion
engine to the preset reference negative pressure in the course of
motoring the internal combustion engine.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a motor vehicle and a
control method of the motor vehicle.
[0003] 2. Description of the Prior Art
[0004] One proposed technique for a motor vehicle equipped with an
internal combustion engine performs combustion control of the
internal combustion engine including fuel injection control and
ignition control to restart the operation of the internal
combustion engine, after an intake pipe pressure in an air intake
conduit of the internal combustion engine decreases to a sufficient
negative pressure by motoring the internal combustion engine (see,
for example, Japanese Patent Laid-Open Gazette No. 2001-304007).
This prior art motor vehicle delays the combustion control until a
sufficient decrease in amount of the air in the air intake conduit
and a cylinder of the internal combustion engine. The delayed
combustion control reduces the potential shocks on a start of the
internal combustion engine, compared with the combustion control
including fuel injection control and ignition control immediately
after the engine motoring.
[0005] This prior art motor vehicle certainly reduces the potential
shocks on a start of the internal combustion engine but does not
take into account the state of an exhaust treatment catalyst, which
treats the exhaust of the internal combustion engine to convert
harmful components of the exhaust into harmless components. The
prior art motor vehicle delays the start timing of the combustion
control until the engine motoring decreases the intake pipe
pressure in the air intake conduit of the internal combustion
engine to the sufficient negative pressure. In a low temperature
condition, the exhaust treatment catalyst is generally not active
and does not exert the sufficient catalytic conversion power. In
the case where the air in the air intake conduit and in the
cylinder has an uncombusted fuel content, for example, in the event
of slow leakage of the fuel from an injector for injecting the fuel
under the operation stop condition of the internal combustion
engine, the exhaust treatment catalyst in the low temperature
condition may not succeed in sufficiently converting the
uncombusted fuel content for a relatively long time. During
motoring of the internal combustion engine, the air in the air
intake conduit and the cylinder is directly flowed to the exhaust
treatment catalyst. In a high temperature condition of the exhaust
treatment catalyst, the delayed start timing of the combustion
control extends the time of exposure of the exhaust treatment
catalyst to the air and may accelerate deterioration of the exhaust
treatment catalyst. As described above, the delayed start timing of
the combustion control under some conditions of the exhaust
treatment catalyst may cause the worsened emission or the
accelerated deterioration of the exhaust treatment catalyst.
SUMMARY OF THE INVENTION
[0006] The object of the invention is thus to eliminate the
drawbacks of the prior art technique and to provide a motor vehicle
that reduces potential shocks on a start of an internal combustion
engine and prevents potential troubles arising under some
conditions of an exhaust treatment catalyst, as well as to a
corresponding control method of such a motor vehicle.
[0007] In order to attain at least part of the above and the other
related objects, the present invention is constructed as
follows.
[0008] The present invention is directed to a motor vehicle
including: a motoring device that is capable of motoring an
internal combustion engine; an exhaust treatment catalyst that
treats exhaust of the internal combustion engine to convert harmful
components of the exhaust into harmless components; a catalyst
state detection unit that detects a state of the exhaust treatment
catalyst; an in-cylinder air flow specification module that
specifies whether an intake air flow into a cylinder of the
internal combustion engine decreases to a preset low range; and an
internal combustion engine start control module that starts
combustion control of the internal combustion engine, in response
to requirement for a restart of the internal combustion engine.
When the state of the exhaust treatment catalyst detected by the
catalyst state detection unit is a preset adequate state, the
internal combustion engine start control module starts the
combustion control of the internal combustion engine after
specification of a decrease in intake air flow into the cylinder of
the internal combustion engine to the preset low range by the
in-cylinder air flow specification module in the course of motoring
the internal combustion engine by the motoring device. When the
state of the exhaust treatment catalyst detected by the catalyst
state detection unit is not the preset adequate state but is an
inadequate state, the internal combustion engine start control
module immediately starts the combustion control of the internal
combustion engine, prior to specification of a decrease in intake
air flow into the cylinder of the internal combustion engine to the
preset low range by the in-cylinder air flow specification module
in the course of motoring the internal combustion engine by the
motoring device.
[0009] In the preset adequate state of the exhaust treatment
catalyst, the motor vehicle of the invention starts the combustion
control of the internal combustion engine to restart the operation
of the internal combustion engine, after the intake air flow into
the cylinder decreases to the preset low range in the course of
motoring the internal combustion engine. This desirably reduces the
potential shocks on a start of the internal combustion engine. In
the inadequate state of the exhaust treatment catalyst, on the
other hand, the motor vehicle of the invention immediately starts
the combustion control of the internal combustion engine, prior to
a decrease of the intake air flow into the cylinder to the preset
low range. This may not sufficiently reduce the potential shocks on
a start of the internal combustion engine but effectively prevents
the potential troubles caused by a delayed start timing of the
combustion control in the course of engine motoring in the
inadequate state of the exhaust treatment catalyst. The low range
may be set experimentally or otherwise to a specific level of the
intake air flow into the cylinder, which restrains the driver from
feeling uncomfortable by the shocks in the combustion control after
engine motoring on a start of the internal combustion engine.
[0010] In the motor vehicle of the invention, the preset low range
may represent a certain level of the intake air flow into the
cylinder that is equivalent to idling operation of the internal
combustion engine. This arrangement ensures a smooth start of the
internal combustion engine without causing an engine stall and
effectively reduces the potential shocks on a start of the internal
combustion engine.
[0011] In one preferable embodiment of the motor vehicle of the
invention, the in-cylinder air flow specification module includes
an intake pipe pressure specification module, which determines
whether an intake pipe pressure of the internal combustion engine
decreases to a preset reference negative pressure and thereby
specifies whether the intake air flow into the cylinder of the
internal combustion engine decreases to the preset low range. The
lower intake air flow into the cylinder tends to decrease the
intake pipe pressure. Namely the intake air flow into the cylinder
is correlated to the intake pipe pressure. The intake air flow into
the cylinder is thus estimable from the measured intake pipe
pressure.
[0012] The present invention is also directed to another motor
vehicle including: a motoring device that is capable of motoring an
internal combustion engine; an exhaust treatment catalyst that
treats exhaust of the internal combustion engine to convert harmful
components of the exhaust into harmless components; a catalyst
state detection unit that detects a state of the exhaust treatment
catalyst; an intake pipe pressure specification module that
specifies whether an intake pipe pressure of the internal
combustion engine decreases to a preset reference negative
pressure; and an internal combustion engine start control module
that starts combustion control of the internal combustion engine,
in response to requirement for a restart of the internal combustion
engine. When the state of the exhaust treatment catalyst detected
by the catalyst state detection unit is a preset adequate state,
the internal combustion engine start control module starts the
combustion control of the internal combustion engine after
specification of a decrease in intake pipe pressure of the internal
combustion engine to the preset reference negative pressure by the
intake pipe pressure specification module in the course of motoring
the internal combustion engine by the motoring device. When the
state of the exhaust treatment catalyst detected by the catalyst
state detection unit is not the preset adequate state but is an
inadequate state, the internal combustion engine start control
module immediately starts the combustion control of the internal
combustion engine, prior to specification of a decrease in intake
pipe pressure of the internal combustion engine to the preset
reference negative pressure by the intake pipe pressure
specification module in the course of motoring the internal
combustion engine by the motoring device.
[0013] In the preset adequate state of the exhaust treatment
catalyst, the motor vehicle of the invention starts the combustion
control of the internal combustion engine to restart the operation
of the internal combustion engine, after the intake pipe pressure
decreases to the preset reference negative pressure in the course
of motoring the internal combustion engine. This desirably reduces
the potential shocks on a start of the internal combustion engine.
In the inadequate state of the exhaust treatment catalyst, on the
other hand, the motor vehicle of the invention immediately starts
the combustion control of the internal combustion engine, prior to
a decrease of the intake pipe pressure to the preset reference
negative pressure. This may not sufficiently reduce the potential
shocks on a start of the internal combustion engine but effectively
prevents the potential troubles caused by a delayed start timing of
the combustion control in the course of engine motoring in the
inadequate state of the exhaust treatment catalyst. The reference
negative pressure may be set experimentally or otherwise to a
specific pressure level, which restrains the driver from feeling
uncomfortable by the shocks in the combustion control after engine
motoring on a start of the internal combustion engine.
[0014] In the motor vehicle of the invention, the preset reference
negative pressure may represent a certain level of the intake pipe
pressure that is equivalent to idling operation of the internal
combustion engine. This arrangement ensures a smooth start of the
internal combustion engine without causing an engine stall and
effectively reduces the potential shocks on a start of the internal
combustion engine.
[0015] In one preferable structure of the motor vehicle of the
invention, the intake pipe pressure specification module specifies
whether the intake pipe pressure of the internal combustion engine
decreases to the preset reference negative pressure, based on a
specific parameter in correlation to the intake pipe pressure of
the internal combustion engine. This structure does not require
direct measurement of the intake pipe pressure. The specific
parameter may be a motoring time of the internal combustion engine
by the motoring device. The longer motoring time tends to decrease
the intake pipe pressure to a greater negative pressure. The
motoring time is thus the parameter correlated to the intake pipe
pressure.
[0016] In one preferable application of the motor vehicle of the
invention, the catalyst state detection unit detects the inadequate
state of the exhaust treatment catalyst, when the exhaust treatment
catalyst has a temperature in a low temperature range that allows
exertion of only an insufficient catalytic conversion power. Such
definition enables an early start of the combustion control in the
low catalyst temperature range where the exhaust treatment catalyst
has the insufficient catalytic conversion power. This application
of the invention effectively prevents extension of an undesirable
emission time period when the uncombusted fuel content remaining in
an air intake conduit or the cylinder of the internal combustion
engine is not sufficiently converted by the exhaust treatment
catalyst bus is directly discharged to the outside air. This
arrangement thus desirably prevents the worsened emission. The low
temperature range represents a certain temperature condition of the
exhaust treatment catalyst that is below a required activation
temperature or just reaches the required activation temperature but
still has only an insufficient level of the catalytic conversion
power. The low temperature range may be determined experimentally
or empirically.
[0017] In another preferable application of the motor vehicle of
the invention, the catalyst state detection unit detects the
inadequate state of the exhaust treatment catalyst, when the
exhaust treatment catalyst has a temperature in a high temperature
range that causes quick deterioration of the exhaust treatment
catalyst by exposure to the air. Such definition enables an early
start of the combustion control in the high catalyst temperature
range. This application of the invention effectively restrains the
exhaust treatment catalyst from being excessively exposed to the
air flowed to the exhaust treatment catalyst by engine motoring and
thus prevents the accelerated deterioration of the exhaust
treatment catalyst. The high temperature range represents a certain
temperature condition of the exhaust treatment catalyst that
accelerates deterioration of the exhaust treatment catalyst in
exposure to the air. The high temperature range may be determined
experimentally or empirically.
[0018] In one preferable embodiment of the invention, the motor
vehicle further includes an internal combustion engine stop control
module that stops the operation of the internal combustion engine
upon satisfaction of a preset internal combustion engine auto stop
condition. The internal combustion engine start control module
restarts the internal combustion engine upon satisfaction of a
preset internal combustion engine auto start condition after the
stop of the operation of the internal combustion engine by the
internal combustion engine stop control module. In motor vehicles
with auto stop and auto restart functions of the internal
combustion engine, the internal combustion engine repeats stopping
and restarting frequently during a drive. This arrangement is
preferably applicable to the motor vehicles with such
functions.
[0019] In the motor vehicle of this preferable embodiment, the
internal combustion engine stop control module may prohibit the
stop of the internal combustion engine when the exhaust treatment
catalyst is not in the preset adequate state during operation of
the internal combustion engine. This arrangement desirably reduces
the frequency of restarting the operation of the internal
combustion engine in the inadequate state of the exhaust treatment
catalyst.
[0020] The present invention is further directed to a control
method of a motor vehicle, including the steps of: (a) detecting a
state of an exhaust treatment catalyst that treats exhaust of the
internal combustion engine to convert harmful components of the
exhaust into harmless components; and (b) when the state of the
exhaust treatment catalyst detected by the step (a) is a preset
adequate state, starting the combustion control of the internal
combustion engine after specification of a decrease in intake air
flow into the cylinder of the internal combustion engine to the
preset low range in the course of motoring the internal combustion
engine, and when the state of the exhaust treatment catalyst
detected by the step (a) is not the preset adequate state but is an
inadequate state, starting the combustion control of the internal
combustion engine, prior to specification of a decrease in intake
air flow into the cylinder of the internal combustion engine to the
preset low range in the course of motoring the internal combustion
engine.
[0021] In the preset adequate state of the exhaust treatment
catalyst, the control method of the invention starts the combustion
control of the internal combustion engine to restart the operation
of the internal combustion engine, after the intake air flow into
the cylinder decreases to the preset low range in the course of
motoring. This desirably reduces the potential shocks on a start of
the internal combustion engine. In the inadequate state of the
exhaust treatment catalyst, on the other hand, the control method
of the invention starts the combustion control of the internal
combustion engine, prior to a decrease of the intake air flow into
the cylinder to the preset low range. This may not sufficiently
reduce the potential shocks on a start of the internal combustion
engine but effectively prevents the potential troubles caused by a
delayed start timing of the combustion control in the course of
engine motoring in the inadequate state of the exhaust treatment
catalyst. This control method may further include steps for
actualizing the additional functions described above in connection
with the motor vehicle of the invention.
[0022] The present invention is further directed to another control
method of a motor vehicle, comprising the steps of: (a) detecting a
state of an exhaust treatment catalyst that treats exhaust of the
internal combustion engine to convert harmful components of the
exhaust into harmless components; and (b) when the state of the
exhaust treatment catalyst detected by the step (a) is a preset
adequate state, starting the combustion control of the internal
combustion engine after specification of a decrease in intake pipe
pressure of the internal combustion engine to the preset reference
negative pressure in the course of motoring the internal combustion
engine, and when the state of the exhaust treatment catalyst
detected by the step (a) is not the preset adequate state but is an
inadequate state, starting the combustion control of the internal
combustion engine, prior to specification of a decrease in intake
pipe pressure of the internal combustion engine to the preset
reference negative pressure in the course of motoring the internal
combustion engine.
[0023] In the preset adequate state of the exhaust treatment
catalyst, the control method of the invention starts the combustion
control of the internal combustion engine to restart the operation
of the internal combustion engine, after the intake pipe pressure
decreases to the preset reference negative pressure in the course
of motoring the internal combustion engine. This desirably reduces
the potential shocks on a start of the internal combustion engine.
In the inadequate state of the exhaust treatment catalyst, on the
other hand, the control method of the invention starts the
combustion control of the internal combustion engine, prior to a
decrease of the intake pipe pressure to the preset reference
negative pressure. This may not sufficiently reduce the potential
shocks on a start of the internal combustion engine but effectively
prevents the potential troubles caused by a delayed start timing of
the combustion control in the course of engine motoring in the
inadequate state of the exhaust treatment catalyst. This control
method may further include steps for actualizing the additional
functions described above in connection with the motor vehicle of
the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] FIG. 1 schematically illustrates the configuration of a
hybrid vehicle;
[0025] FIG. 2 schematically illustrates the configuration of an
engine;
[0026] FIG. 3 is a flowchart showing a start control routine;
[0027] FIG. 4 is an example of a torque demand setting map;
[0028] FIG. 5 is a graph showing variations of torque command Tm1*
against time elapsed since a start of motoring;
[0029] FIG. 6 is an alignment chart that explains dynamics of
rotational elements in a power distribution integration mechanism
30.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0030] One mode of carrying out the invention is described below as
a preferred embodiment with reference to the accompanied drawings.
FIG. 1 schematically illustrates the configuration of a hybrid
vehicle 20 in one embodiment of the invention. As shown in FIG. 1,
the hybrid vehicle 20 of the embodiment includes an engine 22, an
engine electronic control unit 50 (engine ECU 50) that controls the
operations of the whole engine system, a three shaft-type power
distribution integration mechanism 30 that is linked to a
crankshaft 26 or an output shaft of the engine 22 via a damper 28,
a motor MG1 that is connected to the power distribution integration
mechanism 30 and has power generation capability, a reduction gear
35 that is attached to a ring gear shaft 32a or a driveshaft linked
with the power distribution integration mechanism 30, a motor MG2
that is connected to the reduction gear 35, and a hybrid electronic
control unit 70 that controls the operations of the whole hybrid
vehicle 20. As illustrated in FIG. 2, the hybrid vehicle 20 also
has a catalytic converter 160 located downstream the engine 22 to
treat the exhaust and convert harmful components of the exhaust
into harmless components.
[0031] The engine 22 is an internal combustion engine that consumes
a hydrocarbon fuel, such as gasoline or light oil, to output power.
As shown in FIG. 2, the air cleaned by an air cleaner 122 and taken
in via a throttle valve 124 is mixed with the atomized gasoline
injected by an injector 126 to the air-fuel mixture. The air-fuel
mixture is introduced into a cylinder 150 via an intake valve 128.
The introduced air-fuel mixture is ignited with spark made by a
spark plug 130 to be explosively combusted. The reciprocating
motions of a piston 132 by the combustion energy are converted into
rotational motions of the crankshaft 26. The throttle valve 124
varies an inclination angle (opening) relative to the cross section
of an air intake conduit 121 to regulate the air flow through the
air intake conduit 121. An actuator 136 is actuated to electrically
vary the opening of the throttle valve 124. The opening of the
throttle valve 124 is measured by a throttle position sensor 146
and is output to the engine ECU 50. The exhaust from the engine 22
goes through the catalytic converter 160 that converts toxic
components included in the exhaust, that is, carbon monoxide (CO),
hydrocarbons (HC), and nitrogen oxides (NOx), into harmless
components, and is discharged to the outside air.
[0032] The catalytic converter 160 is connected with an exhaust
conduit 123 and is filled with an exhaust treatment catalyst 161. A
typical example of the exhaust treatment catalyst 161 is a
three-way catalyst that mainly consists of an oxidation catalyst,
such as platinum (Pt) or palladium (Pd), a reduction catalyst, such
as rhodium (Rh), and an assisting catalyst, such as ceria
(CeO.sub.2). The functions of the oxidation catalyst convert CO and
HC into water (H.sub.2O) and carbon dioxide (CO.sub.2). The
functions of the reduction catalyst convert NOx into nitrogen
(N.sub.2) and oxygen (O.sub.2). A temperature sensor 162 is
attached to the catalytic converter 160 to monitor the temperature
of the exhaust treatment catalyst 161.
[0033] The engine ECU 50 is constructed as a microprocessor
including a CPU, a ROM that stores processing programs, a RAM that
temporarily stores data, and input and output ports, which are not
specifically illustrated. The engine ECU 50 receives, via its input
port, signals from various sensors that measure and detect the
conditions of the engine 22. The signals input into the engine ECU
50 include a throttle opening from the throttle position sensor
146, an air intake flow into the engine 22 from a vacuum sensor
148, pulse signals from a crank angle sensor 140, and a catalyst
temperature from the temperature sensor 162. The engine ECU 50
outputs, via its output port, diverse control signals and driving
signals to drive and control the engine 22. The signals output from
the engine ECU 50 include driving signals to the actuator 136 for
actuating the throttle valve 124, driving signals to the injector
126, and control signals to an ignition coil 138 integrated with an
igniter to control the spark by the spark plug 130. The engine ECU
50 is electrically connected with the hybrid electronic control
unit 70 to drive and control the engine 22 in response to control
signals received from the hybrid electronic control unit 70 and to
output data regarding the operating conditions of the engine 22 to
the hybrid electronic control unit 70 according to the
requirements.
[0034] The power distribution integration mechanism 30 has a sun
gear or external gear 31, a ring gear or internal gear 32 that is
arranged concentrically with the sun gear 31, multiple pinion gears
33 that engage with both the sun gear 31 and the ring gear 32, and
a carrier 34 that holds the multiple pinion gears 33 to allow their
revolutions and rotations on their axes. The power distribution
integration mechanism 30 is constructed as a planetary gear
mechanism that has differential motions with the sun gear 31, the
ring gear 32, and the carrier 34 as rotating elements. When the
motor MG1 functions as an electric generator, the power output from
the engine 22 and transmitted through the carrier 34 is distributed
to the sun gear 31 and the ring gear 32 at their gear ratio. When
the motor MG1 functions as an electric motor, on the other hand,
the power output from the engine 22 and transmitted through the
carrier 34 is integrated with the power output from the motor MG1
and transmitted through the sun gear 31 and is output to the ring
gear 32. The power output to the ring gear 32 is accordingly
transmitted to drive wheels 63 via a ring gear shaft 32a, the gear
mechanism 60, and the differential gear 62.
[0035] Both the motors MG1 and MG2 are known synchronous motor
generators that are driven as a generator and as a motor. The
motors MG1 and MG2 transmit electric power to and from a battery 55
via inverters 41 and 42. Power lines 54 that connect the inverters
41 and 42 with the battery 55 are constructed as a positive
electrode bus line and a negative electrode bus line shared by the
inverters 41 and 42. This arrangement enables the electric power
generated by one of the motors MG1 and MG2 to be consumed by the
other motor. The motor MG1 also functions as a starter to rotate
the crank shaft 26 of the engine 22 at the time of starting the
engine. Operations of both the motors MG1 and MG2 are controlled by
a motor electronic control unit (hereinafter, referred to as motor
ECU) 40. The motor ECU 40 receives diverse signals required for
controlling the operations of the motors MG1 and MG2, for example,
signals from rotational position detection sensors 43 and 44 that
detect the rotational positions of rotors in the motors MG1 and MG2
and phase currents applied to the motors MG1 and MG2 and measured
by non-illustrated current sensors. The motor ECU 40 outputs
switching control signals to the inverters 41 and 42. The motor ECU
40 communicates with the hybrid electronic control unit 70 to
control operations of the motors MG1 and MG2 in response to control
signals transmitted from the hybrid electronic control unit 70
while outputting data relating to the operating conditions of the
motors MG1 and MG2 to the hybrid electronic control unit 70
according to the requirements.
[0036] The battery 55 is under control of a battery electronic
control unit (hereinafter, referred to as a battery ECU) 56. The
battery ECU 56 receives diverse signals required for control of the
battery 55, for example, an inter-terminal voltage measured by a
non-illustrated voltage sensor disposed between terminals of the
battery 55, a charge-discharge current measured by a
non-illustrated current sensor attached to the power line 54
connected with the output terminal of the battery 55, and a battery
temperature measured by a temperature sensor 57 attached to the
battery 55. The battery ECU 56 outputs data relating to the state
of the battery 55 to the hybrid electronic control unit 70
according to the requirements. The battery ECU 56 calculates a
state of charge (SOC) of the battery 55, based on the accumulated
charge-discharge current measured by the current sensor, for
control of the battery 55.
[0037] The hybrid electronic control unit 70 is constructed as a
microprocessor including a CPU 72, a ROM 74 that stores processing
programs, a RAM 76 that temporarily stores data, a non-illustrated
input-output port, and a non-illustrated communication port. The
hybrid ECU 70 receives various signals via the input port: an
ignition signal from an ignition switch 80, a gearshift position SP
from a gearshift position sensor 82 that detects the current
position of a gearshift lever 81, an accelerator opening Acc from
an accelerator pedal position sensor 84 that measures a step-on
amount of an accelerator pedal 83, a brake pedal position BP from a
brake pedal position sensor 86 that measures a step-on amount of a
brake pedal 85, and a vehicle speed V from a vehicle speed sensor
88. The hybrid electronic control unit 70 is connected with the
engine ECU 50, the motor ECU 40, and the battery ECU 56 via the
communication port and transmits diverse control signals and data
to and from the engine ECU 50, the motor ECU 40, and the battery
ECU 56, as mentioned above.
[0038] The hybrid vehicle 20 of the embodiment thus constructed
calculates a torque demand to be output to the ring gear shaft 32a
functioning as the drive shaft, based on observed values of a
vehicle speed V and an accelerator opening Acc, which corresponds
to a driver's step-on amount of the accelerator pedal 83. The
engine 22 and the motors MGl and MG2 are subjected to operation
control to output a required level of power corresponding to the
calculated torque demand to the ring gear shaft 32a. The operation
control of the engine 22 and the motors MG1 and MG2 selectively
effectuates one of a torque conversion drive mode, a
charge-discharge drive mode, and a motor drive mode. The torque
conversion drive mode controls the operations of the engine 22 to
output a quantity of power equivalent to the required level of
power, while driving and controlling the motors MG1 and MG2 to
cause all the power output from the engine 22 to be subjected to
torque conversion by means of the power distribution integration
mechanism 30 and the motors MG1 and MG2 and output to the ring gear
shaft 32a. The charge-discharge drive mode controls the operations
of the engine 22 to output a quantity of power equivalent to the
sum of the required level of power and a quantity of electric power
consumed by charging the battery 55 or supplied by discharging the
battery 55, while driving and controlling the motors MG1 and MG2 to
cause all or part of the power output from the engine 22 equivalent
to the required level of power to be subjected to torque conversion
by means of the power distribution integration mechanism 30 and the
motors MG1 and MG2 and output to the ring gear shaft 32a,
simultaneously with charge or discharge of the battery 55. The
motor drive mode stops the operations of the engine 22 and drives
and controls the motor MG2 to output a quantity of power equivalent
to the required level of power to the ring gear shaft 32a.
[0039] The description regards the operations of the hybrid vehicle
20 having the configuration discussed above, especially a series of
control to restart the operation of the engine 22, for example, in
response to a shift of the drive mode from the motor drive mode to
the torque conversion drive mode or to the charge-discharge drive
mode. FIG. 3 is a flowchart showing a start control routine
executed by the hybrid electronic control unit 70. This start
control routine is performed on a start of the engine 22.
[0040] In the start control routine of FIG. 3, the CPU 72 of the
hybrid electronic control unit 70 first inputs required data for
start control, that is, the accelerator opening Acc from the
accelerator pedal position sensor 84, the vehicle speed V from the
vehicle speed sensor 87, a rotation speed Ne of the engine 22,
rotation speeds Nm1 and Nm2 of the motors MG1 and MG2, a time t
elapsed since a start of motoring the engine 22, and an output
limit Wout of the battery 55 (step S100). The rotation speed Ne of
the engine 22 is computed in response to signals output from the
crank angle sensor 140 attached to the crankshaft 26 and is
received from the engine ECU 50 by communication. The rotation
speeds Nm1 and Nm2 of the motors MG1 and MG2 are computed from the
rotational positions of the respective rotors in the motors MG1 and
MG2 detected by the rotational position detection sensors 43 and 44
and are received from the motor ECU 40 by communication. The time t
elapsed since a start of motoring the engine 22 is input as the
count of a timer, which starts counting time in response to a start
request of the engine 22. The output limit Wout of the battery 55
is set corresponding to the temperature Tb of the battery 55
measured by the temperature sensor 57 and the state of charge SOC
of the battery 55 and is received from the battery ECU 56 by
communication.
[0041] After the data input, the CPU 72 sets a torque demand Tr* to
be output to the ring gear shaft 32a or the driveshaft, based on
the input accelerator opening Acc and the input vehicle speed V
(step S102). A concrete procedure of setting the torque demand Tr*
in this embodiment stores in advance variations in torque demand
Tr* against the accelerator opening Acc and the vehicle speed V as
a torque demand setting map in the ROM 74 and reads the torque
demand Tr* corresponding to the given accelerator opening Acc and
the given vehicle speed V from this torque demand setting map. One
example of the torque demand setting map is shown in FIG. 4.
[0042] The CPU 72 subsequently sets a torque command Tm1* of the
motor MG1, based on the input time t elapsed since a start of
motoring the engine 22 (step S104). A concrete procedure of setting
the torque command Tm1* of the motor MG1 in this embodiment stores
in advance a variation in torque command Tm1* against the time t
elapsed since a start of motoring as a torque command setting map
in the ROM 74 and reads the torque command Tm1* corresponding to
the given time t elapsed since a start of motoring from this torque
command setting map. One example of the torque command setting map
is shown in FIG. 5. As shown in the map of FIG. 5, the torque
command Tm1* of the motor MG1 gradually increases from a time t0
when a start request of the engine 22 is output, and reaches a
preset relatively high torque level T1 at a time t1. The torque
command Tm1* is kept at the preset relatively high torque level T1
for a preset time period between the time t1 and a time t2 and
gradually decreases to reach a preset torque level T2 at a time t3.
The torque level T1 and the time period between the time t1 and the
time t2 are set as a torque and a time length that ensure a quick
increase in rotation speed Ne of the engine 22, and depend upon the
performances of the engine 22 and the battery 55. The torque level
T2 is set as a torque that further increases the rotation speed Ne
of the engine 22 while saving the power consumption for motoring,
and depends upon the performances of the engine 22 and the battery
55. The torque command Tm1* of the motor MG1 is set to make the
rotation speed Ne of the engine 22 increase to and subsequently
kept at a preset starting rotation speed Nstart.
[0043] The CPU 72 then determines whether the rotation speed Ne of
the engine 22 reaches or exceeds the preset starting rotation speed
Nstart (step S106). Immediately after output of the start request
of the engine 22, the rotation speed Ne of the engine 22 is lower
than the preset starting rotation speed Nstart. In this state, a
negative answer is given at step S106 and the processing flow goes
to step S116. At step S116, the CPU 72 calculates an upper torque
restriction Tmax as a maximum possible torque output from the motor
MG2 according to Equation (1) given below. The calculation
subtracts the product of the torque command Tm1* and the rotation
speed Nm1 of the motor MG1, which represents the power consumption
of the motor MG1, from the output limit Wout of the battery 55 and
divides the difference by the rotation speed Nm2 of the motor MG2:
Tmax=(Wout-Tm1*-Nm1)/Nm2 (1)
[0044] The CPU 72 then calculates a tentative motor torque Tm2tmp
as a torque to be output from the motor MG2 from the torque demand
Tr*, the torque command Tm1* of the motor MG1, a gear ratio p of
the power distribution integration mechanism 30, and a gear ratio
Gr of the reduction gear 35 according to Equation (2) given below
(step S118): Tm2tmp=(Tr*+Tm1*/p)/Gr (2) The CPU 72 compares the
calculated upper torque restriction Tmax with the calculated
tentative motor torque Tm2tmp and sets the smaller to a torque
command Tm2* of the motor MG2 (step S120). Such setting of the
torque command Tm2* of the motor MG2 enables the output torque of
the motor MG2 to cancel out a reactive torque applied to the ring
gear shaft 32a or the driveshaft while the motor MG1 is motoring
the engine 22. The torque demand Tr* to be output to the ring gear
shaft 32a is restricted to the output limit of the battery 55.
[0045] Equation (2) given above is readily led from an alignment
chart of FIG. 6. In the alignment chart of FIG. 6, the left axis
`S` represents the rotation speed of the sun gear 31 that is
equivalent to the rotation speed Nm1 of the motor MG1. The middle
axis `C` represents the rotation speed of the carrier 34 that is
equivalent to the rotation speed Ne of the engine 22. The right
axis `R` represents the rotation speed Nr of the ring gear 32 that
is equivalent to division of the rotation speed Nm2 of the motor
MG2 by the gear ratio Gr of the reduction gear 35. The thick arrows
on the axis `S` and the axis `R` represent torques applied to the
respective axes. In the state of the current processing flow, the
engine 22 has not yet started its operation and applies no torque
to the carrier 34. The crankshaft 26 of the engine 22 is supported
by the torque of the motor MG1 (torque command Tm1*) applied to the
sun gear 31. The ring gear shaft 32a receives application of a
reactive torque, and the motor MG2 outputs a cancellation torque
(=-Tm1*/p) to cancel out the reactive torque.
[0046] After setting the torque commands Tm1* and Tm2* of the
motors MG1 and MG2 in the above manner, the CPU 72 sends the torque
commands Tm1* and Tm2* to the motor ECU 40 (step S122). The motor
ECU 40 receives the torque commands Tm1* and Tm2* and performs
switching control of the switching elements included in the
respective inverters 41 and 42 to drive the motor MG1 with the
torque command Tm1* and the motor MG2 with the torque command Tm2*.
The CPU 72 then specifies whether the start of the engine 22 is
complete or incomplete (step S124) The specification of the
complete or incomplete start of the engine 22 is based on
determination of whether the rotation speed Ne of the engine 22
exceeds a reference speed Nref, which is higher than the starting
rotation speed Nstart by a predetermined level. In the state of the
current processing flow, the rotation speed Ne of the engine 22 is
still lower than the starting rotation speed Nstart, and the engine
ECU 50 has not yet started combustion control of the engine 22
including fuel injection control and ignition control. Namely the
CPU 72 specifies incomplete start of the engine 22 at step S124 and
returns the processing flow to step S100.
[0047] The rotation speed Ne of the engine 22 reaches or exceeds
the preset starting rotation speed Nstart during the repeated
execution of steps S100 to S106 and S116 to S124. In this state, an
affirmative answer is given at step S106 and the processing flow
goes to step S108. The CPU 72 determines whether an intake pipe
pressure P is lower than a preset reference negative pressure Pref
(step S108). This specifies whether the intake air flow into the
cylinder 150 decreases to a preset low range. The reference
negative pressure Pref is set to a negative pressure level that is
equivalent to the idling operation of the engine 22. In this
embodiment, the result of the comparison between the intake pipe
pressure P and the preset reference negative pressure Pref at step
S108 is based on the determination of whether the time t elapsed
since a start of motoring exceeds a predetermined reference time
length, for example, 2 to 3 seconds. The reference time length is
experimentally or empirically determined as a required time period
from a start of motoring for decreasing the intake pipe pressure P
to the preset reference negative pressure Pref. Immediately after
the rotation speed Ne of the engine 22 reaches the preset starting
rotation speed Nstart, the time t elapsed since a start of motoring
has not yet exceeded the preset reference time length. Namely the
intake pipe pressure P has not yet decreased to the preset
reference negative pressure Pref. In this state, a negative answer
is given at step S108 and the processing flow goes to step S112.
The CPU 72 specifies whether the exhaust treatment catalyst 161 is
in an adequate state (step S112). In this embodiment, the exhaust
treatment catalyst 161 having the temperature in a specific
temperature range between a preset low reference temperature and a
preset high reference temperature is specified as the exhaust
treatment catalyst 161 in the adequate state. The low reference
temperature represents a lower threshold temperature, below which
the catalytic conversion power of the exhaust treatment catalyst
161 is insufficient. The high reference temperature represents a
higher threshold temperature, above which the exposure of the
exhaust treatment catalyst 161 to the air causes the excessively
particle growth of the exhaust treatment catalyst 161, which
undesirably reduces the surface area of the exhaust treatment
catalyst 161 and accelerates deterioration of the exhaust treatment
catalyst 161. When the temperature of the exhaust treatment
catalyst 161 is within the specific temperature range between the
preset low reference temperature and the preset high reference
temperature, an affirmative answer is given to step S112. The
processing flow then executes steps S116 to S122 and specifies
whether the start of the engine 22 is complete or incomplete at
step S124. In this state, the start of the engine 22 is still
incomplete since the engine ECU 50 has not yet started the
combustion control of the engine 22. A negative answer is
accordingly given at step S124 and the processing flow goes back to
step S100. In the adequate state of the exhaust treatment catalyst
161, motoring of the engine 22 continues until the intake pipe
pressure P of the air intake conduit 121 reaches the preset
reference negative pressure Pref. During this engine motoring, the
internal air of the air intake conduit 121 and the cylinder 150 is
flowed to the exhaust treatment catalyst 161. The exhaust treatment
catalyst 161 converts the uncombusted fuel content in the air flow,
prior to discharge to the outside air. This prevents the worsened
emission and the accelerated deterioration of the exhaust treatment
catalyst 161 due to the air-induced particle growth.
[0048] The intake pipe pressure P decreases to be lower than the
preset reference negative pressure Pref during the repeated
execution of steps S100 to S108, S112, and S116 to S124. In this
state, an affirmative answer is given at step S108 and the
processing flow goes to step S110. The CPU 72 specifies execution
or no-execution of combustion control of the engine 22 including
fuel injection control and ignition control (step S110).
Immediately after the intake pipe pressure P decreases below the
preset reference negative pressure Pref, the engine ECU 50 has not
yet started the combustion control of the engine 22. In this state,
a negative answer is given at step S110 and the processing flow
goes to step S114. The CPU 72 instructs the engine ECU 50 to start
the combustion control (step S114). The engine ECU 50 starts the
combustion control of the engine 22 in response to this
instruction. In this state, the intake pipe pressure P is lower
than the preset reference negative pressure Pref, and the intake
air flow into the cylinder 150 decreases to the preset low range.
The combustion control of the engine 22 in this state reduces the
potential shocks on a start of the engine 22, compared with the
combustion control of the engine 22 immediately after the increase
of the rotation speed Ne of the engine 22 to the preset starting
rotation speed Nstart, that is, under the condition of the intake
pipe pressure P of not lower than the preset reference negative
pressure Pref. The processing flow then executes steps S116 to S122
and specifies whether the start of the engine 22 is complete or
incomplete at step S124. In this state, the start of the engine 22
is still incomplete since the engine ECU 50 has just started the
combustion control of the engine 22. A negative answer is thus
given again at step S124 and the processing flow goes back to step
S100. This time, an affirmative answer is given at step S110 after
the processing of steps S100 to S108 since the engine ECU 50 has
started the combustion control of the engine 22. The processing
flow then goes to steps S116 to S124. The start of the engine 22 is
complete during the repeated execution of steps S100 to S110 and
S116 to S124. The processing flow eventually terminates the start
control routine of FIG. 3 in response to an affirmative answer at
step S124.
[0049] In an inadequate state of the exhaust treatment catalyst
161, on the other hand, the CPU 72 executes the processing of and
after step S110 in response to a negative answer at step S112. In
the inadequate state of the exhaust treatment catalyst 161, the
engine ECU 50 immediately starts the combustion control of the
engine 22 without waiting for a decrease of the intake pipe
pressure P in the air intake conduit 121 to the preset reference
negative pressure Pref. In a lower catalyst temperature condition
than the specific temperature range, the exhaust treatment catalyst
161 has the insufficient catalytic conversion power and can not
sufficiently convert the uncombusted fuel content in the air flow
prior to the discharge to the outside air. The early start of the
combustion control desirably shortens the time period when the air
flow having the uncombusted fuel content is discharged to the
outside air without sufficient catalytic conversion, that is, the
time period of worsened emission. The uncombusted fuel content in
the air flow is ascribed to, for example, slow leakage of the fuel
from the injector 126 under the operation stop condition of the
engine 22. When the temperature of the internal air of the air
intake conduit 121 and the cylinder 150 is lower than the
temperature of the exhaust treatment catalyst 161, the
low-temperature air flow further decreases the temperature of the
exhaust treatment catalyst 161. The early start of the combustion
control shortens the time period when the temperature of the
exhaust treatment catalyst 161 is lowered. In a higher catalyst
temperature condition than the specific temperature range, on the
other hand, exposure of the exhaust treatment catalyst 161 to the
air accelerates deterioration of the exhaust treatment catalyst
161. The early start of the combustion control desirably shortens
the time period when the exhaust treatment catalyst 161 is exposed
to the air flow. This effectively prevents the accelerated
deterioration of the exhaust treatment catalyst 161.
[0050] In the course of drive control in the drive mode with the
active combustion control of the engine 22, for example, in the
torque conversion drive mode or in the charge-discharge drive mode,
the hybrid electronic control unit 70 performs a series of
operations as described below. When the exhaust treatment catalyst
161 is in the adequate state, upon satisfaction of a preset engine
auto stop condition in the course of the drive control in the drive
mode with the active combustion control of the engine 22, the CPU
72 of the hybrid electronic control unit 70 executes engine stop
control. The engine stop control sends a stop instruction to the
engine ECU 50 to stop the combustion control of the engine 22,
while setting the torque commands Tm1* and Tm2* of the motors MG1
and MG2 on the basis of the operation stop of the engine 22 and
sending the set torque commands Tm1* and Tm2* to the motor ECU 40.
After execution of the engine stop control, the CPU 72 executes the
drive control in the motor drive mode or a predetermined vehicle
stop control during a stop of the hybrid vehicle 20. When the
exhaust treatment catalyst 161 is in the inadequate state, on the
other hand, even upon satisfaction of the preset engine auto stop
condition, the CPU 72 of the hybrid electronic control unit 70 does
not send the stop instruction to the engine ECU 50 to stop the
combustion control of the engine 22 but continues the current drive
control. The engine auto stop condition is satisfied, for example,
when an engine power demand Pe* to be output from the engine 22 is
sufficiently low to make the operation efficiency of the engine 2
in a predetermined low efficiency range. The engine power demand
Pe* is calculated as the sum of a drive power demand Pr*, a
charge-discharge power demand Pb* to be charged into or discharged
from the battery 55, and a potential loss Ploss (Pe=Pr*+Pb*+Ploss).
The drive power demand Pr* is obtained by dividing the product of
the rotation speed Nr of the ring gear shaft 32a and the torque
demand Tr*, which is set corresponding to the input accelerator
opening Acc and the input vehicle speed V from the torque demand
setting map of FIG. 4, by the gear ratio Gr of the reduction gear
35. The adequate state or the inadequate state of the exhaust
treatment catalyst 161 is specified according to the same procedure
as step S112 in the start control routine of FIG. 3. When the
exhaust treatment catalyst 161 is in the inadequate state, even
upon satisfaction of the engine auto stop condition, the hybrid
electronic control unit 70 does not stop the combustion control of
the engine 22 but keeps the operation of the engine 22. This
arrangement desirably reduces the occasions when the exhaust
treatment catalyst 161 is in the inadequate state on a start of the
engine 22. Namely this effectively reduces the frequency of
restarting the operation of the engine 22 in the inadequate state
of the exhaust treatment catalyst 161.
[0051] The motor MG1 in the hybrid vehicle 20 of the embodiment is
equivalent to the motoring device of the invention. The hybrid
electronic control unit 70 of the embodiment corresponds to the
in-cylinder air flow specification module and the intake pipe
pressure specification module of the invention. The hybrid
electronic control unit 70 and the engine ECU 50 of the embodiment
are equivalent to the internal combustion engine start control
module and the internal combustion engine stop control module of
the invention. The catalytic converter 160 and the temperature
sensor 162 of the embodiment respectively correspond to the exhaust
treatment catalyst and the catalyst state detection unit of the
invention. The description of the embodiment regarding the
operations of the hybrid vehicle 20 simultaneously gives an
apparent example of the motor vehicle control method of the
invention.
[0052] As described above, when the temperature of the exhaust
treatment catalyst 161 is in a lower temperature range below the
preset low reference temperature or in a higher temperature range
above the preset high reference temperature, the hybrid vehicle 20
of the embodiment starts combustion control of the engine 22
including fuel injection control and ignition control, prior to a
decrease of the intake pipe pressure P in the air intake conduit
121 to the preset reference negative pressure Pref. This
arrangement effectively prevents the potential troubles arising in
the course of engine motoring due to a delayed start of the
combustion control of the engine 22 in the inadequate state of the
exhaust treatment catalyst 161. Such potential troubles include the
extended time period of worsened emission and the accelerated
deterioration of the exhaust treatment catalyst 161.
[0053] In the inadequate state of the exhaust treatment catalyst
161, the control procedure of the embodiment does not allow an auto
stop of the engine 22. This arrangement reduces the frequency of
restarting the operation of the engine 22 in the inadequate state
of the exhaust treatment catalyst, that is, the frequency of
restarting the engine 22 with potential shocks.
[0054] The hybrid vehicle 20 of the embodiment repeats auto stops
and auto starts of the operation of the engine 22 during a drive.
The technique of the invention is preferably applicable to such a
hybrid vehicle to effectively prevent the potential troubles, for
example, the worsened emission and the accelerated deterioration of
the exhaust treatment catalyst.
[0055] In the adequate state of the exhaust treatment catalyst 161,
after a decrease of the intake pipe pressure P in the air intake
conduit 121 to the preset reference negative pressure Pref, the
combustion control starts to reduce the intake air flow into the
cylinder 150. This effectively reduces the potential shocks on a
start of the engine 22. In the condition of the gearshift lever 81
set to a P (parking) position, the ring gear shaft 32a is locked.
In this state, the motor MG2 can not output the cancellation torque
(=--Tm1*/p) to cancel out the reactive torque applied to the ring
gear shaft 32a. The reactive torque is thus directly applied as a
shock to the vehicle body. In the hybrid vehicle 20 of this
embodiment, however, in the adequate state of the exhaust treatment
catalyst 161, the start control can effectively reduce the
potential shocks on a start of the engine 22 even in the condition
of the gearshift lever set to the P position. When the exhaust
treatment catalyst 161 is not in the inadequate state at the time
of starting the engine 22 in the condition of the gearshift lever
81 set to the P position, the start control gives preference to
prevention of the potential troubles arising in the course of
engine motoring due to the inadequate state of the exhaust
treatment catalyst 161, over reduction of the potential shocks on a
start of the engine 22.
[0056] The reference negative pressure Pref is set to a negative
pressure level that is equivalent to the idling operation of the
engine 22. In the adequate state of the exhaust treatment catalyst
161, such setting ensures a smooth start of the engine 22 without
causing an engine stall.
[0057] The embodiment discussed above is to be considered in all
aspects as illustrative and not restrictive. There may be many
modifications, changes, and alterations without departing from the
scope or spirit of the main characteristics of the present
invention. Some examples of possible modification are given
below.
[0058] The start control routine of the embodiment shown in FIG. 3
estimates the intake air flow into the cylinder 150, based on the
intake pipe pressure P. This technique is, however, not
restrictive, and any other suitable technique may be adopted to
estimate the intake air flow into the cylinder 150. In one
applicable structure, an in-cylinder pressure sensor is located in
the cylinder 150 to measure the internal pressure of the cylinder
150. The intake air flow into the cylinder 150 may be estimated
from the internal pressure of the cylinder 150 measured by the
in-cylinder pressure sensor. In another applicable structure, an
airflow meter is located in the air intake conduit 121 to measure
the intake air flow into the engine 22. The intake air flow into
the cylinder 150 is directly measured by the airflow meter.
[0059] The start control routine of the embodiment shown in FIG. 3
determines whether the intake pipe pressure P in the air intake
conduit 121 is lower than the preset reference negative pressure
Pref, based on the time t elapsed since a start of motoring at step
S108. The determination may alternatively be based on the intake
pipe pressure measured by the vacuum sensor 148 set in the air
intake conduit 121.
[0060] The start control routine of the embodiment shown in FIG. 3
immediately starts the combustion control at step S110, upon
specification at step S112 that the exhaust treatment catalyst 161
is in the adequate state. One modified flow of the start control
routine may start the combustion control after engine motoring
until the intake pipe pressure P decreases to a medium negative
pressure level, which is higher than the preset reference negative
pressure Pref by a specific pressure level.
[0061] In the hybrid vehicle 20 of the embodiment, in the
inadequate state of the exhaust treatment catalyst 161, even upon
satisfaction of the engine auto stop condition, the control
procedure does not allow an auto stop of the engine 22. One
possible modification may allow an auto stop of the engine 22 even
under such conditions at a reduced frequency. The modified
procedure counts the number of times of satisfaction of the engine
auto stop condition and allows an engine auto stop at each even
number of times but prohibits the engine auto stop at each odd
number of times.
[0062] The above embodiment regards application of the invention to
the hybrid vehicle 20. The technique of the invention is also
applicable to a vehicle with a simple idling stop function that
prevents transmission of the output powers of motors MG1 and MG2 to
a driveshaft.
[0063] The present invention claims the benefit of priority from
Japanese Patent Application No. 2005-107429 filed on Apr. 4, 2005,
the entire contents of which are incorporated by reference
herein.
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