U.S. patent application number 11/698057 was filed with the patent office on 2007-08-02 for device and method for controlling internal combustion engine.
This patent application is currently assigned to Toyota Jidosha Kabushiki Kaisha. Invention is credited to Yasumichi Inoue, Zenichiro Mashiki, Noboru Takagi, Haruyuki Urushihata, Yuu Yokoyama.
Application Number | 20070175427 11/698057 |
Document ID | / |
Family ID | 38282352 |
Filed Date | 2007-08-02 |
United States Patent
Application |
20070175427 |
Kind Code |
A1 |
Inoue; Yasumichi ; et
al. |
August 2, 2007 |
Device and method for controlling internal combustion engine
Abstract
When an ignition switch is turned off, an ECU executes a program
including the steps of: stopping an engine; setting a phase of an
intake camshaft (or a phase in which an intake valve opens/closes)
to be a maximally retarded phase; advancing the phase of the intake
camshaft; detecting the phase of the intake camshaft as based on a
number or rotations of an electric motor of an intake VVT mechanism
changing the phase of the intake camshaft; and, if the phase
detected as based on the number or rotations of the electric motor
is advanced to a target phase, stopping changing the phase of the
intake camshaft.
Inventors: |
Inoue; Yasumichi;
(Toyota-shi, JP) ; Yokoyama; Yuu; (Okazaki-shi,
JP) ; Mashiki; Zenichiro; (Nisshin-shi, JP) ;
Takagi; Noboru; (Toyota-shi, JP) ; Urushihata;
Haruyuki; (Chiryu-shi, JP) |
Correspondence
Address: |
SUGHRUE MION, PLLC
2100 PENNSYLVANIA AVENUE, N.W., SUITE 800
WASHINGTON
DC
20037
US
|
Assignee: |
Toyota Jidosha Kabushiki
Kaisha
Toyota-shi
JP
DENSO CORPORATION
Kariya-shi
JP
|
Family ID: |
38282352 |
Appl. No.: |
11/698057 |
Filed: |
January 26, 2007 |
Current U.S.
Class: |
123/90.17 ;
123/90.15 |
Current CPC
Class: |
Y02T 10/12 20130101;
F01L 2001/0537 20130101; F02D 13/08 20130101; F01L 2800/03
20130101; Y02T 10/18 20130101; F01L 1/344 20130101 |
Class at
Publication: |
123/90.17 ;
123/90.15 |
International
Class: |
F01L 1/34 20060101
F01L001/34 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 27, 2006 |
JP |
2006-019599(P) |
Claims
1. A control device for an internal combustion engine provided with
a mechanism changing a phase in which at least one valve of an
intake valve and an exhaust valve opens/closes, comprising an
operation unit, wherein: said operation unit controls said
mechanism to change said phase when a predetermined condition
associated with stopping said internal combustion engine is
satisfied; said operation unit detects an amount by which said
mechanism is operated when said mechanism is controlled to change
said phase; said operation unit detects said phase based on said
amount; and said operation unit controls said mechanism to change
said phase detected as based on said amount to attain a
predetermined value.
2. The control device for an internal combustion engine according
to claim 1, wherein said operation unit controls said mechanism to
change said phase after said internal combustion engine is stopped
if said predetermined condition is satisfied.
3. The control device for an internal combustion engine according
to claim 1, wherein: said mechanism includes a motor electrically
operated and having an output shaft rotating to change said phase
in which said valve opens/closes; and said operation unit detects a
number of rotations of said output shaft of said motor accumulated
and detects said phase as based on said number of rotations of said
output shaft of said motor accumulated.
4. A control device for an internal combustion engine provided with
a mechanism changing a phase in which at least one valve of an
intake valve and an exhaust valve opens/closes, comprising an
operation unit, wherein: said operation unit controls said
mechanism to change said phase to attain a limit value when a
predetermined condition associated with stopping said internal
combustion engine is satisfied, said limit value being one of
values of maximally retarded and advanced angles, respectively;
said operation unit controls said mechanism to change said phase
from said limit value if said predetermined condition is satisfied;
said operation unit detects an amount by which said mechanism is
operated when said mechanism is controlled to change said phase
from said limit value; said operation unit detects said phase based
on said amount; and said operation unit controls said mechanism to
change said phase detected as based on said amount to attain a
predetermined value.
5. The control device for an internal combustion engine according
to claim 4, wherein: said operation unit controls said mechanism to
change said phase to said limit value after said internal
combustion engine is stopped if said predetermined condition is
satisfied; and said operation unit controls said mechanism to
change said phase from said limit value after said internal
combustion engine is stopped if said predetermined condition is
satisfied.
6. The control device for an internal combustion engine according
to claim 4, wherein: said mechanism includes a motor electrically
operated and having an output shaft rotating to change said phase
in which said valve opens/closes; and said operation unit detects a
number of rotations of said output shaft of said motor accumulated
and detects said phase as based on said number of rotations of said
output shaft of said motor accumulated.
7. A method of controlling an internal combustion engine provided
with a mechanism changing a phase in which at least one valve of an
intake valve and an exhaust valve opens/closes, comprising the
steps of: controlling said mechanism to change said phase when a
predetermined condition associated with stopping said internal
combustion engine is satisfied; detecting an amount by which said
mechanism is operated when said mechanism is controlled to change
said phase; and detecting said phase based on said amount, wherein
the step of controlling said mechanism includes the step of
controlling said mechanism to change said phase detected in the
step of detecting said phase to attain a predetermined value.
8. The method of controlling an internal combustion engine
according to claim 7, wherein the step of controlling said
mechanism includes the step of controlling said mechanism to change
said phase after said internal combustion engine is stopped if said
predetermined condition is satisfied.
9. The method of controlling an internal combustion engine
according to claim 7, wherein: said mechanism includes a motor
electrically operated and having an output shaft rotating to change
said phase in which said valve opens/closes; the step of detecting
said amount includes the step of detecting a number of rotations of
said output shaft of said motor accumulated; and the step of
detecting said phase includes the step of detecting said phase as
based on said number of rotations of said output shaft of said
motor accumulated.
10. A method of controlling an internal combustion engine provided
with a mechanism changing a phase in which at least one valve of an
intake valve and an exhaust valve opens/closes, comprising the
steps of: controlling said mechanism to change said phase to a
limit value when a predetermined condition associated with stopping
said internal combustion engine is satisfied, said limit value
being one of values of maximally retarded and advanced angles,
respectively; controlling said mechanism to change said phase from
said limit value when said predetermined condition is satisfied,
detecting an amount by which said mechanism is operated when said
mechanism is controlled to change said phase from said limit value;
and detecting said phase based on said amount, wherein the step of
controlling said mechanism to change said phase from said limit
value includes the step of controlling said mechanism to change
said phase detected as based on said amount to attain a
predetermined value.
11. The method of controlling an internal combustion engine
according to claim 10, wherein: the step of controlling said
mechanism to change said phase to said limit value includes the
step of controlling said mechanism to change said phase to said
limit value after said internal combustion engine is stopped if
said predetermined condition is satisfied; and the step of
controlling said mechanism to change said phase from said limit
value includes the step of controlling said mechanism to change
said phase from said limit value after said internal combustion
engine is stopped if said predetermined condition is satisfied.
12. The method of controlling an internal combustion engine
according to claim 10, wherein: said mechanism includes a motor
electrically operated and having an output shaft rotating to change
said phase in which said valve opens/closes; the step of detecting
said amount includes the step of detecting a number of rotations of
said output shaft of said motor accumulated; and the step of
detecting said phase includes the step of detecting said phase as
based on said number of rotations of said output shaft of said
motor accumulated.
13. A control device for an internal combustion engine provided
with a mechanism changing a phase in which at least one valve of an
intake valve and an exhaust valve opens/closes, comprising: control
means for controlling said mechanism to change said phase when a
predetermined condition associated with stopping said internal
combustion engine is satisfied; first detection means for detecting
an amount by which said mechanism is operated when said mechanism
is controlled by said control means; and second detection means for
detecting said phase based on said amount, wherein said control
means includes means for controlling said mechanism to change said
phase detected by said second detection means to attain a
predetermined value.
14. The control device for an internal combustion engine according
to claim 13, wherein said control means includes means for
controlling said mechanism to change said phase after said internal
combustion engine is stopped if said predetermined condition is
satisfied.
15. The control device for an internal combustion engine according
to claim 13, wherein: said mechanism includes a motor electrically
operated and having an output shaft rotating to change said phase
in which said valve opens/closes; said first detection means
includes means for detecting a number of rotations of said output
shaft of said motor accumulated; and said second detection means
includes means for detecting said phase as based on said number of
rotations of said output shaft of said motor accumulated.
16. A control device for an internal combustion engine provided
with a mechanism changing a phase in which at least one valve of an
intake valve and an exhaust valve opens/closes, comprising: first
control means for controlling said mechanism to change said phase
to attain a limit value when a predetermined condition associated
with stopping said internal combustion engine is satisfied, said
limit value being one of values of maximally retarded and advanced
angles, respectively; second control means for controlling said
mechanism to change said phase from said limit value if said
predetermined condition is satisfied; first detection means for
detecting an amount by which said mechanism is operated when said
mechanism is controlled by said second control means; and second
detection means for detecting said phase based on said amount,
wherein said second control means includes means for controlling
said mechanism to change said phase detected by said second
detection means to attain a predetermined value.
17. The control device for an internal combustion engine according
to claim 16, wherein: said first control means includes means for
controlling said mechanism to change said phase to said limit value
after said internal combustion engine is stopped if said
predetermined condition is satisfied; and said second control means
includes means for controlling said mechanism to change said phase
from said limit value after said internal combustion engine is
stopped if said predetermined condition is satisfied.
18. The control device for an internal combustion engine according
to claim 16, wherein: said mechanism includes a motor electrically
operated and having an output shaft rotating to change said phase
in which said valve opens/closes; said first detection means
includes means for detecting a number of rotations of said output
shaft of said motor accumulated; and said second detection means
includes means for detecting said phase as based on said number of
rotations of said output shaft of said motor accumulated.
Description
[0001] This nonprovisional application is based on Japanese Patent
Application No. 2006-019599 filed with the Japan Patent Office on
Jan. 27, 2006, the entire contents of which are hereby incorporated
by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates generally to devices and
methods for controlling internal combustion engines and
particularly to techniques employed to control internal combustion
engines in which a phase in which at least one of intake and
exhaust valves is opened/closed is varied.
[0004] 2. Description of the Background Art
[0005] Conventionally there have been known Variable Valve Timing
(VVT) changing in accordance with a condition of operation a phase
in which intake and exhaust valves open/close (or a crank angle),
variable valve lift (VVL) changing an amount in which a valve is
lifted, and other variable valve mechanisms changing how a valve is
operated. Such variable valve mechanisms allow a valve to operate
in a state (or have a phase or be lifted in an amount)
appropriately corresponding to a condition of operation of interest
to provide increased output, improved emission performance, and the
like. While an engine is in operation, a valve is operated in a
state, which is not necessarily appropriate for starting the
engine. For example, if, with the engine in operation, timing the
valve to close is controlled to be maximally retarded, and in that
condition the engine is stopped, then, in subsequently starting the
engine, an insufficiently compressed air fuel mixture can be
provided. This can results in impaired startability. Accordingly a
technique has been proposed to change, while stopping an engine,
how a valve is operated.
[0006] Japanese Patent Laying-Open No. 2003-184585 discloses a
control device for an internal combustion engine, that controls,
while stopping the engine, a condition of an operation
opening/closing a valve (or how the valve is operated) to be that
condition of such operation which is targeted for automatically
stopping an engine (an internal combustion engine). As disclosed in
the publication, the control device includes: a variable valve
control unit varying a condition of an operation opening/closing an
intake valve or both intake and exhaust valves of the internal
combustion engine to at least control intake air in amount; a
control unit automatically stopping the engine when a predetermined
condition for automatically stopping the engine is established
while the internal combustion engine is in operation; a control
unit controlling a valve in automatically stopping the engine, that
calculates that condition of the operation opening/closing the
valve which is targeted for automatically stopping the engine, as
based on the current condition of the internal combustion engine
and/or the vehicle, immediately after the control unit
automatically stopping the engine automatically stops the internal
combustion engine, and that controls a condition of the operation
opening/closing the valve to be that of such operation which is
targeted for automatically stopping the engine. As the condition of
the operation opening/closing the valve that is targeted for
automatically stopping the engine, the control unit controlling a
valve in automatically stopping the engine calculates a condition
of such operation which is estimated to be optimal for
subsequently, automatically starting the engine.
[0007] As disclosed in the publication, immediately after the
internal combustion engine is automatically stopped, the control
device calculates from the current condition of the internal
combustion engine, that of the vehicle and the like a condition of
an operation opening/closing the valve which is estimated to be
optimal for subsequently, automatically starting the engine as that
of such operation which is targeted for automatically stopping the
engine. While the engine is stopped, a condition of the operation
opening/closing the valve is controlled to match that of such
operation which is targeted. This allows the engine to
subsequently, automatically start with the valve opened/closed in a
condition which is substantially optimal for automatically starting
the engine to improve the engine in automatic startability and also
reduce emissions provided in automatically starting the engine.
[0008] Generally the phase of an intake or exhaust valve or the
like is detected as based on a pulse signal provided from a cam
position sensor employing an electromagnetic pickup sensor. The cam
position sensor outputs the pulse signal as an air gap varies that
is formed between the cam position sensor and a cam angle sensor
plate rotating together with a camshaft. However, when the engine
stops, the cam angle sensor plate (or the camshaft) rotates slowly
or has a rotational speed of zero, and the air gap hardly varies
and the pulse signal is hardly obtained. If the control device for
an internal combustion engine as disclosed in Japanese Patent
Laying-Open No. 2003-184585 is applied to change, while stopping
the internal combustion engine, a phase in which a valve
opens/closes, the phase is hardly detected. As a consequence, the
phase in which the valve is opened/closed cannot be controlled with
precision.
SUMMARY OF THE INVENTION
[0009] The present invention contemplates a control device or the
like for an internal combustion engine, that can control with
precision, while stopping an internal combustion engine, a phase in
which intake and exhaust valves open/close.
[0010] The present invention in one aspect provides a control
device for an internal combustion engine provided with a mechanism
changing a phase in which at least one valve of an intake valve and
an exhaust valve opens/closes. The control device includes an
operation unit. The operation unit: controls the mechanism to
change the phase when a predetermined condition associated with
stopping the internal combustion engine is satisfied; detects an
amount by which the mechanism is operated when the mechanism is
controlled to change the phase; detects the phase based on the
amount; and controls the mechanism to change the phase detected as
based on the amount to attain a predetermined value.
[0011] In accordance with the present invention when a
predetermined condition associated with stopping an internal
combustion engine is satisfied a phase in which intake and exhaust
valves open/close is changed. For example the phase is changed to
attain a value appropriate for subsequently starting the internal
combustion engine. However, with the internal combustion engine
stopped, or immediately before the engine stops, the crankshaft (or
the camshaft) has an extremely low rotational speed. In this
condition, the phase is hardly detected with a cam position sensor
employing an electromagnetic pickup sensor or the like.
Accordingly, the amount by which a mechanism changing the phase is
operated is detected and from the amount detected, the phase is
detected. For example, a relationship between the amount by which
the mechanism is operated and the phase's variation is previously
obtained through an experiment or the like and stored in the form
of a map which is used to detect the phase's variation. From the
variation as detected and the current phase (e.g., a phase detected
when it is detectable by a cam position senor, a phase that can be
obtained mechanically, or the like), the changed phase is detected.
A phase in which the intake and exhaust valves open/close can thus
be obtained with precision without the cam position sensor. The
phase thus detected is changed until it attains a predetermined
value. The phase in which the intake and exhaust valves open/close
can thus be changed to the predetermined value with precision. A
control device for an internal combustion engine can thus be
provided that allows a phase in which the intake and exhaust valves
open/close to be controlled with precision while the internal
combustion engine is stopped.
[0012] Preferably the operation unit controls the mechanism to
change the phase after the internal combustion engine is stopped if
the predetermined condition is satisfied.
[0013] In accordance with the present invention a phase in which a
valve opens/closes is changed after the internal combustion engine
is stopped. This can prevent the valve from opening/closing in a
phase that would not be appropriate for the internal combustion
engine in operation while the internal combustion engine is in
operation. The phase in which the intake and exhaust valves
open/close can thus be controlled in accordance with a condition of
operation of interest with precision.
[0014] Still preferably, the mechanism includes a motor
electrically operated and having an output shaft rotating to change
the phase in which the valve opens/closes, and the operation unit
detects a number of rotations of the output shaft of the motor
accumulated and detects the phase as based on the number of
rotations of the output shaft of the motor accumulated.
[0015] In accordance with the present invention the phase in which
a valve opens/closes is changed as an electric motor's output shaft
rotates. The phase is detected as based on the number of rotations
of the output shaft of the motor accumulated. The phase in which
the intake and exhaust valves open/close can thus be obtained with
precision without the cam position sensor and hence controlled with
precision.
[0016] The present invention in another aspect provides a control
device for an internal combustion engine provided with a mechanism
changing a phase in which at least one valve of an intake valve and
an exhaust valve opens/closes. The control device includes an
operation unit. The operation unit: controls the mechanism to
change the phase to attain a limit value when a predetermined
condition associated with stopping the internal combustion engine
is satisfied, the limit value being one of values of maximally
retarded and advanced angles, respectively; controls the mechanism
to change the phase from the limit value if the predetermined
condition is satisfied; detects an amount by which the mechanism is
operated when the mechanism is controlled to change the phase from
the limit value; detects the phase based on the amount; and
controls the mechanism to change the phase detected as based on the
amount to attain a predetermined value.
[0017] In accordance with the present invention when a
predetermined condition associated with stopping an internal
combustion engine is satisfied a phase is changed to a limit value.
The limit value is one of values of maximally retarded and advanced
angles, respectively, and mechanically determined by the structure
of the mechanism and can be obtained previously. The phase in which
a valve opens/closes that is set at the limit value can eliminate
the necessity of employing a sensor or the like to detect the phase
with precision. Such limit value is used as a reference to change
the phase. For example the phase is changed to attain a value
appropriate for subsequently starting the internal combustion
engine. However, with the internal combustion engine stopped, or
immediately before the engine stops, the crankshaft (or the
camshaft) has an extremely low rotational speed. In this condition,
the phase is hardly detected with a cam position sensor employing
an electromagnetic pickup sensor or the like. Accordingly, the
amount by which a mechanism changing the phase is operated is
detected and from the amount detected, the phase is detected. For
example, a relationship between the amount by which the mechanism
is operated and the phase is previously obtained through an
experiment or the like and stored in the form of a map which is
used to detect the phase's variation. From the variation as
detected and the limit value, the changed phase is detected. A
phase in which the intake and exhaust valves open/close can thus be
obtained with precision without the cam position sensor. The phase
thus detected is changed until it attains a predetermined value.
The phase in which the intake and exhaust valves open/close can
thus be changed to the predetermined value with precision. A
control device for an internal combustion engine can thus be
provided that allows a phase in which the intake and exhaust valves
open/close to be controlled with precision while the internal
combustion engine is stopped.
[0018] Preferably, the operation unit controls the mechanism to
change the phase to the limit value after the internal combustion
engine is stopped if the predetermined condition is satisfied, and
the operation unit controls the mechanism to change the phase from
the limit value after the internal combustion engine is stopped if
the predetermined condition is satisfied.
[0019] In accordance with the present invention after the internal
combustion engine is stopped the phase is changed to the limit
value, and subsequently from that limit value the phase is changed.
This can prevent the valve from opening/closing in a phase that
would not be appropriate for the internal combustion engine in
operation while the internal combustion engine is in operation. The
phase in which the intake and exhaust valves open/close can thus be
controlled in accordance with a condition of operation of interest
with precision.
[0020] Still preferably, the mechanism includes a motor
electrically operated and having an output shaft rotating to change
the phase in which the valve opens/closes, and the operation unit
detects a number of rotations of the output shaft of the motor
accumulated and detects the phase as based on the number of
rotations of the output shaft of the motor accumulated.
[0021] In accordance with the present invention the phase in which
a valve opens/closes is changed as an electric motor's output shaft
rotates. The phase is detected as based on the number of rotations
of the output shaft of the motor accumulated. The phase in which
the intake and exhaust valves open/close can thus be obtained with
precision without the cam position sensor and hence controlled with
precision.
[0022] The foregoing and other objects, features, aspects and
advantages of the present invention will become more apparent from
the following detailed description of the present invention when
taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] FIG. 1 schematically shows a configuration of an engine of a
vehicle with an ECU a control device of an embodiment, mounted
therein.
[0024] FIG. 2 shows a map defining a target value of a phase of an
intake camshaft.
[0025] FIG. 3 is a flowchart representing a structure of a program
for control executed by the ECU shown in FIG. 1.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0026] With reference to the drawings, an embodiment of the present
invention will be described hereinafter. In the following
description, like components are denoted by like reference
characters. They are also named identically and function
identically. Therefore, a detailed description thereof will not be
repeated.
[0027] Referring to FIG. 1, a description is given of an engine of
a vehicle having a control device mounted therein according to the
embodiment of the present invention. In the present embodiment the
control device is implemented by a program executed for example by
an electronic control unit (ECU) 4000 shown in FIG. 1.
[0028] An engine 1000 is a V-type, 8-cylinder engine having an "A"
bank 1010 and a "B" bank 1012 each including a group of four
cylinders. Here, any engine other than the V8 engine may be
employed.
[0029] Into engine 1000, air is sucked from an air cleaner 1020.
The quantity of air sucked is adjusted by a throttle valve 1030.
Throttle valve 1030 is an electronic throttle valve driven by a
motor.
[0030] The air is mixed with fuel in a cylinder 1040 (or combustion
chamber). Into cylinder 1040, the fuel is directly injected from an
injector 1050. In other words, injection holes of injector 1050 are
provided within cylinder 1040.
[0031] The fuel is injected in the intake stroke. When the fuel is
injected is not limited to the intake stroke. Further, in the
present embodiment, engine 1000 is described as a direct-injection
engine having injection holes of injector 1050 that are disposed
within cylinder 1040. However, in addition to direct-injection
(in-cylinder) injector 1050, a port injector may be provided.
Moreover, only the port injector may be provided.
[0032] The air-fuel mixture in cylinder 1040 is ignited by a spark
plug 1060 and accordingly burned. The air-fuel mixture after
burned, namely exhaust gas, is cleaned by a three-way catalyst 1070
and thereafter discharged to the outside of the vehicle. The
air-fuel mixture is burned to press down a piston 1080 and thereby
rotate a crankshaft 1090.
[0033] At the top of cylinder 1040, an intake valve 1100 and an
exhaust valve 1110 are provided. Intake valve 1100 is driven by an
intake camshaft 1120. Exhaust valve 1110 is driven by an exhaust
camshaft 1130. Intake camshaft 1120 and exhaust camshaft 1130 are
coupled by a chain, a gear and/or the like to be rotated at the
same rotational speed.
[0034] Intake valve 1100 has its phase (or is timed to open/close,
as) controlled by an intake VVT mechanism 2000 provided to intake
camshaft 1120. Exhaust valve 1110 has its phase (or is timed to
open/close, as) controlled by an exhaust VVT mechanism 3000
provided to exhaust camshaft 1130.
[0035] In the present embodiment, intake camshaft 1120 and exhaust
camshaft 1130 are rotated by the VVT mechanisms to time intake
valve 1100 and exhaust valve 1110, as controlled, to open/close.
Note that the valves may be timed, as controlled in a method
different than above, to open/close.
[0036] Intake VVT mechanism 2000 is operated by an electric motor
2010 having an output shaft connected to intake camshaft 1120 via a
speed reducer (not shown) of intake VVT mechanism 2000. The speed
reducer is configured of a link, a gear and/or the like.
[0037] Electric motor 2060 is controlled by ECU 4000. The current
and voltage of electric motor 2060 are detected by an ammeter (not
shown) and a voltmeter (not shown) and the measurements are input
to ECU 4000.
[0038] Exhaust VVT mechanism 3000 is hydraulically operated. Note
that intake VVT mechanism 2000 may be hydraulically operated.
Furthermore, exhaust VVT mechanism 3000 may be operated by an
electric motor. Furthermore the hydraulic pressure generated by an
electric motor may be employed to operate intake and exhaust VVT
mechanisms 2000 and 3000. The VVT mechanism can be implemented by
known technology and accordingly, will not be described repeatedly
in detail.
[0039] ECU 4000 receives a signal from a crank angle sensor 5000
indicating the rotational speed and crank angle of crankshaft 1090.
Further, ECU 4000 receives a signal from a cam position sensor 5010
indicating a phase of intake and exhaust camshafts 1120 and 1130
(or the position of the camshaft in the direction of rotation).
[0040] Crank angle sensor 5000 and cam position sensor 5010 are
electromagnetic pickup sensors and output a pulse signal to ECU
4000.
[0041] Crank angle sensor 5000 outputs the pulse signal as an air
gap formed between the sensor and a timing rotor rotating together
with crank shaft 1090 varies. Cam position sensor 5010 outputs the
pulse signal as an air gap formed between the sensor and a cam
angle sensor plate rotating together with the camshaft varies.
[0042] Furthermore ECU 4000 receives a pulse signal from a
rotational speed sensor 5012 indicating the rotational speed of the
output shaft of electric motor 2010 of intake VVT mechanism 2000, a
signal from a coolant temperature sensor 5020 indicating the water
(or coolant) temperature of engine 1000, and a signal from an
airflow meter 5030 indicating the quantity of intake air of engine
1000 (i.e., the quantity of air taken or sucked into engine 1000).
Furthermore ECU 4000 receives a signal from an ignition switch 5040
indicating that ignition switch 5040 is turned on or off.
[0043] Based on these signals received from the sensors as well as
a map and a program stored in a memory (not shown), ECU 4000
controls: the throttle angle; the timing of ignition; the timing of
injection of fuel; the quantity of fuel injected; timing intake and
exhaust valves 1100 and 1110 to open/close; and the like so that
engine 1000 is operated in a desired operating state.
[0044] In the present embodiment, ECU 4000 determines the phase of
intake camshaft 1120 (or how intake valve 1100 should be timed to
open/close) based on a map employing engine speed NE and intake air
quantity KL as parameters, as shown in FIG. 2. A plurality of maps
for respective coolant temperatures are stored for determining the
phase of intake camshaft 1120.
[0045] Reference will now be made to FIG. 3 to describe a structure
of a program for control executed by ECU 4000 in the present
embodiment.
[0046] In step (S) 100 ECU 4000 determines whether ignition switch
5040 is turned off. If so (YES in S100) the control proceeds with
S200. Otherwise (NO in S100) the process ends.
[0047] In S200 ECU 4000 stops engine 1000. In S300 ECU 4000 sets
the phase of intake camshaft 1120 (a phase in which intake valve
1100 opens/closes) to be a maximally retarded phase for example by
retarding the phase until the voltage of electric motor 2010
rapidly increases (or a lock voltage is detected).
[0048] In S400 ECU 4000 advances the phase of intake camshaft 1120.
In S500 ECU 4000 detects the phase of intake camshaft 1120 based on
the rotational speed of electric motor 2010 as detected by
rotational speed sensor 5012.
[0049] More specifically, a map storing a relationship between a
number of rotations of motor 2010 accumulated from a state with
intake camshaft 1120 having the maximally retarded phase and the
phase's variation is used to detect the variation of the phase of
intake camshaft 1120. From the variation of the phase as detected
and the maximally retarded phase (for example by adding together
the maximally retarded phase and the variation of the phase as
detected, or subtracting the variation of the phase as detected
from the maximally retarded phase) a phase obtained after the
advance (or change) is detected. Note that the phase of intake
camshaft 1120 may be detected in a method other than described
above.
[0050] In S600 ECU 4000 determines the phase of intake camshaft
1120 as detected from the rotational speed of electric motor 2010
has advanced to a predetermined target phase. If the detected phase
and the target phase have a difference having a predetermined value
or smaller, ECU 4000 determines that the phase of intake camshaft
1120 detected has advanced to the predetermined target phase. Note
that the target phase is a phase determined as a phase appropriate
for subsequently starting the engine. The phase appropriate for
starting the engine is set with startability and emission
performance considered.
[0051] If the detected phase has advanced to the target phase (YES
in S600) the control proceeds with S700. Otherwise (NO in S600) the
control returns to S400.
[0052] In S700 ECU 4000 stops changing the phase of intake camshaft
1120. More specifically, electric motor 2010 is stopped from
operating and the phase of intake camshaft is maintained.
Subsequently the process ends.
[0053] As based on the structure and flowchart as described above,
the control device in the present embodiment, or ECU 4000, operates
as will be described hereinafter.
[0054] To stop engine 1000 the driver turns off ignition switch
5040 (YES in S100). In response, engine 1000 is stopped (S200). If
at that time intake camshaft 1120 has a phase for example maximally
retarded and thus held, then, in subsequently starting the engine,
an insufficiently compressed air fuel mixture can be provided. This
impairs startability.
[0055] Accordingly, desirably, as engine 1000 is stopped, the phase
of intake camshaft 1120 is changed to attain a target phase
determined as a phase appropriate for subsequently starting the
engine.
[0056] When engine 1000 stops, however, intake camshaft 1120 does
not rotate. Cam position sensor 5010 employing an electromagnetic
pickup sensor cannot detect the phase of intake camshaft 1120, and
the phase of intake camshaft 1120 may not be changed to the target
phase with precision.
[0057] Accordingly when engine 1000 is stopped the phase of intake
camshaft 1120 is once set to be the maximally retarded phase
(S300). The maximally retarded phase is a phase mechanically
determined by the structure of intake VVT mechanism 2000.
Previously storing the maximally retarded phase for example in
memory allows the maximally retarded phase to be detected without
cam position sensor 5010.
[0058] With this phase as a reference, the phase of intake camshaft
1120 is advanced (S400). The phase of intake camshaft 1120 advanced
is detected as based on the number of rotations of electric motor
2010 accumulated, as detected by rotational speed sensor 5012
(S500). More specifically, A variation from the maximally retarded
phase is detected to detect the phase of intake camshaft 1120.
[0059] Thus the phase of intake camshaft 1120 can be detected
without cam position sensor 5010. In particular, in the present
embodiment, electric motor 2010 has its output shaft connected to
intake camshaft 1120 via a speed reducer. Accordingly, electric
motor 2010 has a sufficiently high rotational speed (or a large
number of rotations accumulated) in changing the phase of intake
camshaft 1120. As such, the rotational speed (or the number of
rotations) of electric motor 2010 (accumulated) is sufficiently (or
with high precision) detectable by rotational speed sensor 5012.
The phase of intake camshaft 1120 can thus be detected with
precision from the number of rotations of electric motor 2010
accumulated.
[0060] If the phase thus detected has advanced to the target phase
(YES in S600) changing the phase is stopped (S700). The phase of
intake camshaft 1120 can thus be set to be a phase appropriate for
subsequently starting the engine.
[0061] Thus the present embodiment provides a control device or ECU
operating so that when the ignition switch is turned off to stop
the engine the phase of the intake camshaft is once set to be a
maximally retarded phase. While the phase of the intake camshaft is
advanced with the maximally retarded phase serving as a reference,
the phase of the intake camshaft is detected as based on the number
of rotations of an electric motor of an intake VVT mechanism
accumulated. This allows the phase of the intake camshaft to be
detected if a pulse signal is not obtained from a cam position
sensor. The phase of the intake camshaft can thus be controlled
with precision.
[0062] Note that while in the present embodiment engine 1000 is
stopped in response to ignition switch 5040 being turned off,
engine 1000 may be stopped when the vehicle has a vehicular speed
of "0" and the brake pedal is also depressed, i.e., an idle-stop
condition, or an other stop condition is satisfied.
[0063] Furthermore, changing the phase of intake camshaft 1120
after engine 1000 is stopped may be replaced with changing the
phase of intake camshaft 1120 if ignition switch 5040 is turned off
or the idle-stop condition or a similar stop condition is satisfied
or the like and before engine 1000 is stopped.
[0064] Furthermore, the phase of intake camshaft 1120 may be
changed immediately before engine 1000 is started.
[0065] Furthermore, setting the phase of intake camshaft 1120 to be
a maximally retarded phase may be replaced with setting the phase
of intake camshaft 1120 to be a maximally advanced phase and
subsequently retarding the phase to a target phase.
[0066] Furthermore, a target phase and the current phase of intake
camshaft 1120 may be compared and from a result thereof whether the
phase of intake camshaft 1120 should be set to be a maximally
retarded phase or a maximally advanced phase may be determined.
Such decision may be made to reduce the total variation of the
phase.
[0067] Furthermore, the phase of intake camshaft 1120 may be
changed to a target phase, rather than set to be a maximally
retarded or advanced phase. The phase of the intake camshaft 1120
having been changed may be detected from that detected by cam
position sensor 5010 before the phase is changed, and the variation
of the phase as detected as based on the cumulative rotational
speed of electric motor 2010.
[0068] Furthermore, a parameter other than the rotational speed (or
the number of rotations) of electric motor 2010 (accumulated) may
be employed to detect the variation of the phase.
[0069] Furthermore when engine 1000 is stopped the phase of exhaust
camshaft 1130 (or a phase in which exhaust valve 1110 opens/closes)
may be changed. The phase of exhaust camshaft 1130 may be detected
similarly as that of intake camshaft 1120 is detected.
[0070] Although the present invention has been described and
illustrated in detail, it is clearly understood that the same is by
way of illustration and example only and is not to be taken by way
of limitation, the spirit and scope of the present invention being
limited only by the terms of the appended claims.
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