U.S. patent application number 11/540672 was filed with the patent office on 2007-05-03 for control apparatus and control method for internal combustion engine.
This patent application is currently assigned to TOYOTA JIDOSHA KABUSHIKI KAISHA. Invention is credited to Tadao Hasegawa, Masayoshi Hattori, Yuji Itoh, Yoshihito Moriya, Yuu Yokoyama.
Application Number | 20070095314 11/540672 |
Document ID | / |
Family ID | 37912969 |
Filed Date | 2007-05-03 |
United States Patent
Application |
20070095314 |
Kind Code |
A1 |
Yokoyama; Yuu ; et
al. |
May 3, 2007 |
Control apparatus and control method for internal combustion
engine
Abstract
An ECU executes a program including the steps of detecting the
crank angle, advancing, at a crank angle at which the cam torque is
exerted in the direction opposite to the rotational direction of an
intake camshaft, the phase in which the intake valve is closed and
retarding, at a crank angle at which the cam torque is exerted in
the rotational direction of the intake camshaft, the phase in which
the intake valve is closed.
Inventors: |
Yokoyama; Yuu; (Okazaki-shi,
JP) ; Moriya; Yoshihito; (Nagoya-shi, JP) ;
Itoh; Yuji; (Okazaki-shi, JP) ; Hasegawa; Tadao;
(Toyota-shi, JP) ; Hattori; Masayoshi;
(Toyota-shi, JP) |
Correspondence
Address: |
OLIFF & BERRIDGE, PLC
P.O. BOX 19928
ALEXANDRIA
VA
22320
US
|
Assignee: |
TOYOTA JIDOSHA KABUSHIKI
KAISHA
TOYOTA-SHI
JP
471-8571
|
Family ID: |
37912969 |
Appl. No.: |
11/540672 |
Filed: |
October 2, 2006 |
Current U.S.
Class: |
123/90.17 ;
123/90.15 |
Current CPC
Class: |
F01L 2800/00 20130101;
Y02T 10/12 20130101; F01L 1/34 20130101; F02D 13/0207 20130101;
F01L 2810/03 20130101 |
Class at
Publication: |
123/090.17 ;
123/090.15 |
International
Class: |
F01L 1/34 20060101
F01L001/34 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 1, 2005 |
JP |
2005-318509 |
Claims
1. A control apparatus for an internal combustion engine including
a camshaft driving a valve and a change mechanism changing a phase
in which said valve is closed, said control apparatus comprising an
operation unit, and said operation unit controlling said change
mechanism in a manner that the phase is advanced in a case where a
torque exerted on said camshaft by rotation of said camshaft acts
in a direction opposite to a rotational direction of said camshaft,
and controlling said change mechanism in a manner that the phase is
retarded in a case where said torque acts in the rotational
direction of said camshaft.
2. The control apparatus for the internal combustion engine
according to claim 1, wherein said operation unit controls said
change mechanism in a manner that the phase is advanced to a
greater extent as the torque acting in the direction opposite to
the rotational direction of said camshaft is larger, and controls
said change mechanism in a manner that the phase is retarded to a
greater extent as the torque acting in the rotational direction of
said camshaft is larger.
3. The control apparatus for the internal combustion engine
according to claim 1, wherein said operation unit controls said
change mechanism in a manner that the phase is advanced to a
greater extent as said camshaft has a higher rotational speed, and
controls said change mechanism in a manner that the phase is
retarded to a greater extent as said camshaft has a higher
rotational speed.
4. The control apparatus for the internal combustion engine
according to claim 1, wherein said operation unit controls said
change mechanism in a manner that the phase is advanced to a
greater extent as said internal combustion engine has a higher
load, and controls said change mechanism in a manner that the phase
is retarded to a greater extent as said internal combustion engine
has a higher load.
5. A control method for an internal combustion engine including a
camshaft driving a valve and a change mechanism changing a phase in
which said valve is closed, comprising the steps of: controlling
said change mechanism in a manner that the phase is advanced in a
case where a torque exerted on said camshaft by rotation of said
camshaft acts in a direction opposite to a rotational direction of
said camshaft; and controlling said change mechanism in a manner
that the phase is retarded in a case where said torque acts in the
rotational direction of said camshaft.
6. The control method for the internal combustion engine according
to claim 5, wherein said step of controlling said change mechanism
in the manner that the phase is advanced includes the step of
controlling said change mechanism in a manner that the phase is
advanced to a greater extent as the torque acting in the direction
opposite to the rotational direction of said camshaft is larger,
and said step of controlling said change mechanism in the manner
that the phase is retarded includes the step of controlling said
change mechanism in a manner that the phase is retarded to a
greater extent as the torque acting in the rotational direction of
said camshaft is larger.
7. The control method for the internal combustion engine according
to claim 5, wherein said step of controlling said change mechanism
in the manner that the phase is advanced includes the step of
controlling said change mechanism in a manner that the phase is
advanced to a greater extent as said camshaft has a higher
rotational speed, and said step of controlling said change
mechanism in the manner that the phase is retarded includes the
step of controlling said change mechanism in a manner that the
phase is retarded to a greater extent as said camshaft has a higher
rotational speed.
8. The control method for the internal combustion engine according
to claim 5, wherein said step of controlling said change mechanism
in the manner that the phase is advanced includes the step of
controlling said change mechanism in a manner that the phase is
advanced to a greater extent as said internal combustion engine has
a higher load, and said step of controlling said change mechanism
in the manner that the phase is retarded includes the step of
controlling said change mechanism in a manner that the phase is
retarded to a greater extent as said internal combustion engine has
a higher load.
9. A control apparatus for an internal combustion engine including
a camshaft driving a valve and a change mechanism changing a phase
in which said valve is closed, said control apparatus comprising:
first control means for controlling said change mechanism in a
manner that the phase is advanced in a case where a torque exerted
on said camshaft by rotation of said camshaft acts in a direction
opposite to a rotational direction of said camshaft; and second
control means for controlling said change mechanism in a manner
that the phase is retarded in a case where said torque acts in the
rotational direction of said camshaft.
10. The control apparatus for the internal combustion engine
according to claim 9, wherein said first control means includes
means for controlling said change mechanism in a manner that the
phase is advanced to a greater extent as the torque acting in the
direction opposite to the rotational direction of said camshaft is
larger, and said second control means includes means for
controlling said change mechanism in a manner that the phase is
retarded to a greater extent as the torque acting in the rotational
direction of said camshaft is larger.
11. The control apparatus for the internal combustion engine
according to claim 9, wherein said first control means includes
means for controlling said change mechanism in a manner that the
phase is advanced to a greater extent as said camshaft has a higher
rotational speed, and said second control means includes means for
controlling said change mechanism in a manner that the phase is
retarded to a greater extent as said camshaft has a higher
rotational speed.
12. The control apparatus for the internal combustion engine
according to claim 9, wherein said first control means includes
means for controlling said change mechanism in a manner that the
phase is advanced to a greater extent as said internal combustion
engine has a higher load, and said second control means includes
means for controlling said change mechanism in a manner that the
phase is retarded to a greater extent as said internal combustion
engine has a higher load.
Description
[0001] This nonprovisional application is based on Japanese Patent
Application No. 2005-318509 filed with the Japan Patent Office on
Nov. 1, 2005, 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 to control of an internal
combustion engine. In particular, the invention relates to the
technique of advancing or retarding a phase in which a valve is
closed, according to a torque exerted on a camshaft that drives the
valve.
[0004] 2. Description of the Background Art
[0005] An internal combustion engine has been known that has such
valves as intake valves and exhaust valves opened and closed by
rotation of camshafts. In such an internal combustion engine, as
the camshaft rotates, a reaction force from the valve causes a
torque acting on the camshaft (the torque is also referred to as
cam torque hereinafter). As the valve is opened, the cam torque is
exerted in the direction opposite to the rotational direction of
the camshaft (the cam torque is exerted in the direction that
hinders rotation of the camshaft). In contrast, as the valve is
closed, the cam torque is exerted in the rotational direction of
the camshaft (the cam torque is exerted in the direction that helps
rotation of the camshaft). Therefore, the torque necessary for
rotating the camshaft may vary to a significant degree while the
camshaft makes one rotation. Thus, for VVT (Variable Valve Timing)
that changes the phase in which the valve is opened/closed (valve
opening/closing timing) by rotation of the camshaft that drives the
valve (relative rotation with respect to the sprocket for example),
the cam torque could influence the VVT. In other words, depending
on the direction in which the cam torque is exerted, the phase of
the valve may be easy to change or difficult to change by rotation
of the camshaft. Therefore, it is necessary to take the cam torque
into account for controlling the phase.
[0006] Japanese Patent Laying-Open No. 2005-076518 discloses a
control apparatus for a variable valve timing mechanism that
changes the phase according to the cam torque. The control
apparatus disclosed in Japanese Patent Laying-Open No. 2005-076518
controls the variable valve timing mechanism that changes the
rotational phase of the camshaft relative to the crankshaft of the
internal combustion engine to vary the valve timing of an intake
valve or an exhaust valve. The control apparatus detects the state
of the cam torque generated on the camshaft due to operation of the
cam driving to open/close the intake valve or the exhaust valve
and, when the cam torque is generated in the direction opposite to
the direction of changing the rotational phase, decreases the
degree of change in rotational phase or maintains the rotational
phase as it is.
[0007] Regarding the control apparatus for the variable valve
timing mechanism disclosed in the above-referenced publication,
when the rotational phase is to be changed and the cam torque is
generated in the direction that hinders the change of the
rotational phase, the change (degree of change) of the rotational
phase is decreased or the change in rotational phase is stopped.
Thus, an increase in engine load due to the cam torque can be
prevented.
[0008] As for a V-type 8-cylinder internal combustion engine
employing a double-plane (also referred to as dual-plane)
crankshaft with crankpins arranged at 90.degree. therebetween, it
is known that the right and left banks cannot be fired alternately
and firing is successively caused in one of the banks. In such a V8
internal combustion engine, the cylinders are not fired at regular
intervals. Thus, valves provided to respective cylinders have
respective phases (opening/closing timings) that are not at regular
intervals as well. Therefore, there may be the case where a valve
of one of the cylinders is closed in a certain phase (at a certain
timing) while opening operation of another cylinder in the same
bank may be started in that phase (at that timing) and there may be
the case where the above-described valve state does not occur.
Accordingly, in a phase (at a timing) in (at) which valves of some
of the cylinders are closed, the cam torque exerted in the
direction opposite to the camshaft rotational direction increases.
If the cam torque exerted in the direction opposite to the camshaft
rotational direction is large, the phase in which the valve is
actually closed is later than or delayed relative to a phase
determined under control due to influences of deformation or the
like of such components as a chain coupling the crankshaft and
camshafts and other parts. In contrast, there may be the case where
the intake valve of any cylinder is closed in a certain phase while
the intake valve of another cylinder in the same bank is in the
transition from the opening operation to the closing operation in
that phase and there may be the case where such a valve state does
not occur. Accordingly, in a phase in which some of the cylinders
are closed, the cam torque exerted in the camshaft rotational
direction increases. If the cam torque exerted in the camshaft
rotational direction is large, the phase in which the valve is
actually closed is earlier than or advanced relative to a phase
determined under control, due to influences of deformation or the
like of such components as the chain coupling the crankshaft and
camshafts and other parts. In the cylinder having its intake valve
closed in the delayed phase, the quantity of air pushed back from
the cylinder into the intake manifold as the piston is lifted
increases, resulting in a decrease in final quantity of air sucked
into the cylinders. On the contrary, in the cylinder having its
intake valve closed in the advanced phase, the quantity of air
pushed back from the cylinder into the intake manifold as the
piston is lifted decreases, resulting in an increase in final
quantity of air sucked into the cylinder. Therefore, some cylinders
are smaller in sucked or intake air quantity than other cylinders.
Further, in a cylinder having its exhaust valve closed in a delayed
phase, the quantity of exhaust gas sucked back from the exhaust
manifold into the cylinder as the piston is moved downward
increases (namely internal EGR (Exhaust Gas Recirculation) quantity
increases). On the contrary, in a cylinder having its exhaust valve
closed in an advanced phase, the quantity of exhaust gas sucked
back from the exhaust manifold into the cylinder as the piston is
moved downward decreases. Therefore, the cylinders are nonuniform
in internal EGR quantity. For such an internal combustion engine as
described above, if the control apparatus for the variable valve
timing mechanism disclosed in Japanese Patent Laying-Open No.
2005-076518 is used, the difference in quantity of air taken into
cylinders as well as the difference in internal EGR quantity could
be increased. In other words, for such a cylinder having its intake
valve or exhaust valve closed in a delayed phase, in the phase in
which the intake valve or exhaust valve is closed, the cam torque
is exerted in the direction opposite to the direction in which the
phase is advanced (camshaft rotational direction), so that advance
of the phase is restrained or stopped. On the contrary, in such a
cylinder having its intake valve or exhaust valve closed in an
advanced phase, in the phase in which the intake valve or exhaust
valve is closed, the cam torque is exerted in the direction of
advancing the phase, so that the advance of the phase is continued.
Consequently, the phase in which the intake valve or exhaust valve
is actually closed is further displaced from a phase determined
under control, which could increase differences in air quantity and
internal EGR for example between cylinders.
SUMMARY OF THE INVENTION
[0009] An object of the present invention is to provide a control
apparatus or the like for an internal combustion engine that can
restrain occurrence of nonuniformity of cylinders with respect to
each other in terms of intake air quantity and internal EGR
quantity.
[0010] A control apparatus for an internal combustion engine
according to the present invention controls the internal combustion
engine including a camshaft driving a valve and a change mechanism
changing a phase in which the valve is closed. The control
apparatus includes an operation unit. The operation unit controls
the change mechanism in a manner that the phase is advanced in a
case where a torque exerted on the camshaft by rotation of the
camshaft acts in a direction opposite to a rotational direction of
the camshaft, and controls the change mechanism in a manner that
the phase is retarded in a case where the torque acts in the
rotational direction of the camshaft.
[0011] In accordance with the present invention, in the case where
the torque acts in the opposite direction to the camshaft
rotational direction, the phase in which the valve is closed is
advanced and, in the case where the torque acts in the camshaft
rotational direction, the phase is retarded. Thus, for a cylinder,
in the case where the torque acting in the opposite direction to
the camshaft rotational direction could cause delay of the phase
(timing) in (at) which the intake valve or exhaust valve is closed,
the phase in which the intake valve or exhaust valve is closed can
be advanced. Accordingly, occurrence of delay of the phase in which
the intake valve or exhaust valve is closed can be restrained.
Further, for a cylinder, in the case where the torque acting in the
camshaft rotational direction could cause advance of the phase in
which the intake valve or exhaust valve is closed, the phase in
which the intake or exhaust valve is closed can be retarded.
Accordingly, occurrence of advance of the phase in which the intake
valve or exhaust valve is closed can be restrained. Thus, the
control apparatus for the internal combustion engine can be
provided that can restrain occurrence of displacement of the phase
in which the intake valve or exhaust valve of each cylinder is
actually closed with respect to a phase determined under control,
and can restrain occurrence of nonuniformity of cylinders with
respect to each other in terms of quantity of air taken into the
cylinder and internal EGR quantity.
[0012] Preferably, the operation unit controls the change mechanism
in a manner that the phase is advanced to a greater extent as the
torque acting in the direction opposite to the rotational direction
of the camshaft is larger, and controls the change mechanism in a
manner that the phase is retarded to a greater extent as the torque
acting in the rotational direction of the camshaft is larger.
[0013] In accordance with the present invention, as the torque
acting in the opposite direction to the camshaft rotational
direction is larger, the phase of the intake valve or exhaust valve
is advanced to a greater extent. Further, as the torque acting in
the camshaft rotational direction is larger, the phase of the
intake valve or the exhaust valve is retarded to a grater extent.
Accordingly, as delay in phase in which the intake valve or exhaust
valve is closed is larger, the phase in which the intake valve or
exhaust valve is closed can be advanced to a greater extent.
Further, as advance in phase in which the intake valve or exhaust
valve is closed is larger, the phase in which the intake valve or
exhaust valve is closed can be retarded to a greater extent. Thus,
for each cylinder, occurrence of displacement of the phase in which
the intake valve or exhaust valve is actually closed with respect
to a phase determined under control can be restrained, and
occurrence of nonuniformity of cylinders with respect to each other
in terms of intake air quantity and internal EGR quantity can be
restrained.
[0014] Still preferably, the operation unit controls the change
mechanism in a manner that the phase is advanced to a greater
extent as the camshaft has a higher rotational speed, and controls
the change mechanism in a manner that the phase is retarded to a
greater extent as the camshaft has a higher rotational speed.
[0015] In accordance with the present invention, as a higher
camshaft rotational speed causes a larger torque acting in the
opposite direction to the camshaft rotational direction, the phase
of the intake valve or exhaust valve is advanced to a greater
extent. Further, as a higher camshaft rotational speed causes a
larger torque acting in the camshaft rotational direction, the
phase of the intake valve or exhaust valve is retarded to a greater
extent. Accordingly, as delay in phase in which the intake valve or
exhaust valve is closed is larger, the phase in which the intake
valve or exhaust valve is closed can be advanced to a greater
extent. Further, as advance in phase in which the intake valve or
exhaust valve is closed is larger, the phase in which the intake
valve or exhaust valve is closed can be retarded to a greater
extent. Thus, for each cylinder, occurrence of displacement of the
phase in which the intake valve or exhaust valve is actually closed
with respect to a phase determined under control can be restrained,
and occurrence of nonuniformity of cylinders with respect to each
other in terms of intake air quantity and internal EGR quantity can
be restrained.
[0016] Still preferably, the operation unit controls the change
mechanism in a manner that the phase is advanced to a greater
extent as the internal combustion engine has a higher load, and
controls the change mechanism in a manner that the phase is
retarded to a greater extent as the internal combustion engine has
a higher load.
[0017] In accordance with the present invention, as a higher load
of the internal combustion engine causes a larger torque acting in
the opposite direction to the camshaft rotational direction, the
phase of the intake valve or exhaust valve is advanced to a greater
extent. Further, as a higher load of the internal combustion engine
causes a larger torque acting in the camshaft rotational direction,
the phase in which the intake valve or exhaust valve is closed can
be retarded to a greater extent. Accordingly, as delay in phase in
which the intake valve or exhaust valve is closed is larger, the
phase in which the intake valve or exhaust valve is closed can be
advanced to a greater extent. Further, as advance in phase in which
the intake valve or exhaust valve is closed is larger, the phase in
which the intake valve or exhaust valve is closed can be retarded
to a greater extent. Thus, for each cylinder, occurrence of
displacement of the phase in which the intake valve or exhaust
valve is actually closed with respect to a phase determined under
control can be restrained, and nonuniformity of cylinders with
respect to each other in terms of intake air quantity and internal
EGR quantity can be restrained.
[0018] 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
[0019] FIG. 1 schematically shows a configuration of an engine of a
vehicle on which an ECU is mounted that is a control apparatus
according to an embodiment of the present invention.
[0020] FIG. 2 is a map defining target values of the phase of an
intake camshaft.
[0021] FIG. 3 is a perspective view showing a cylinder block.
[0022] FIG. 4 is a table showing the firing order of the
engine.
[0023] FIG. 5 shows changes of a cam torque exerted on the intake
camshaft.
[0024] FIG. 6 shows a map for correcting the phase of an intake
valve.
[0025] FIG. 7 is a flowchart showing a control structure of a
program executed by the ECU in FIG. 1.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0026] With reference to the drawings, embodiments of the present
invention are hereinafter described. 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 is not repeated.
[0027] Referring to FIG. 1, a description is given of an engine of
a vehicle on which a control apparatus is mounted, according to an
embodiment of the present invention. The control apparatus in the
present embodiment is implemented for example by means of a program
executed by an ECU (Electronic Control Unit) 4000 shown in FIG.
1.
[0028] 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 used.
[0029] Into engine 1000, air is sucked from an air cleaner 1020.
The quantity of sucked air 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 (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. The fuel
injection timing 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 provided 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 such parts as a chain and gears to be rotated at the
same rotational speed.
[0034] Intake valve 1100 has its phase (opening/closing timing)
controlled by an intake VVT mechanism 2000 provided to intake
camshaft 1120. Exhaust valve 1110 has its phase (opening/closing
timing) 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 control
respective phases of intake valve 1100 and exhaust valve 1110. It
is noted that the method of controlling the phase is not limited to
the aforementioned one.
[0036] Intake VVT mechanism 2000 is operated by an electric motor.
Exhaust VVT mechanism 3000 is hydraulically operated. It is noted
that intake VVT mechanism 2000 may be hydraulically operated while
exhaust VVT mechanism 3000 may be driven by an electric motor.
Further, since any well-known art may be applied to implement the
VVT mechanism, a detailed description thereof is not given
here.
[0037] To ECU 4000, signals indicating the rotational speed and the
crank angle of crankshaft 1090 are input from a crank angle sensor
5000. Further, to ECU 4000, signals indicating respective phases of
intake camshaft 1120 and exhaust camshaft 1130 (phase: the camshaft
position in the rotational direction) are input from a cam position
sensor 5010.
[0038] Furthermore, to ECU 4000, a signal indicating the water
temperature (coolant temperature) of engine 1000 from a coolant
temperature sensor 5020 as well as a signal indicating the quantity
of intake air (quantity of air taken or sucked into engine 1000) of
engine 1000 from an airflow meter 5030 are input.
[0039] Based on these signals input from the sensors as well as a
map and a program stored in a memory (not shown), ECU 4000 controls
the throttle opening position, the ignition timing, the fuel
injection timing, the quantity of injected fuel, the phase of
intake valve 1100 and the phase of exhaust valve 1110 for example,
so that engine 1000 is operated in a desired operating state.
[0040] In the present embodiment, ECU 4000 determines the phase of
intake valve 1100 based on the map as shown in FIG. 2 that uses the
engine speed NE and the intake air quantity KL as parameters. A
plurality of maps for respective coolant temperatures are stored
for determining the phase of intake valve 1100.
[0041] Referring to FIG. 3, a further description of engine 1000 is
given. In "B" bank 1012 of a cylinder block 1002 of engine 1000,
cylinders 1040 to which respective numbers #1, #3, #5 and #7 are
allocated are formed and arranged successively from the front side
to the rear side of the vehicle.
[0042] Further, in "A" bank 1010 of cylinder block 1002, cylinders
1040 to which respective numbers #2, #4, #6 and #8 are allocated
are formed and arranged successively from the front side to the
rear side of the vehicle.
[0043] As shown in FIG. 4, firing is caused in the cylinders in the
order of #1 cylinder, #8 cylinder, #7 cylinder, #3 cylinder, #6
cylinder, #5 cylinder, #4 cylinder, and #2 cylinder. The firing
interval is 90.degree. in crank angle (CA).
[0044] While crankshaft 1090 makes two rotations (720.degree. in
crank angle), one cycle of engine 1000 is completed that is
comprised of the four steps: intake stroke.fwdarw.compression
stroke.fwdarw.power stroke.fwdarw.exhaust stroke. Therefore,
between two cylinders one of which precedes the other with another
cylinder therebetween in firing order, namely between two cylinders
at a firing interval of 180.degree. in crank angle, there is a
difference in cycle corresponding to one stroke in the cycle.
[0045] Thus, when #1 cylinder is in the transition from the intake
stroke to the compression stroke, #7 cylinder is in the transition
from the exhaust stroke to the intake stroke. Here, in the phase
(timing) in which intake valve 1100 of #1 cylinder is closed,
intake valve 1100 of #7 cylinder starts opening operation.
Therefore, the cam torque increases that is exerted in the
direction opposite to the direction in which intake camshaft 1120
rotates.
[0046] The cam torque exerted in the direction opposite to the
rotational direction of intake camshaft 1120 increases in the phase
in which intake valve 1100 of #3 cylinder is closed, in addition to
the phase in which intake valve 1100 of #1 cylinder is closed.
[0047] Further, regarding two cylinders that are successive in
firing order, namely two cylinders at a firing interval of
90.degree. in crank angle, in the phase in which intake valve 1100
of one cylinder preceding in firing order is closed, intake valve
1100 of the other cylinder following in firing order is in the
transition from the opening operation to the closing operation.
[0048] In the present embodiment, in the phase in which intake
valve 1100 of #7 cylinder is closed, intake valve 1100 of #3
cylinder is in the transition from the opening operation to the
closing operation. Therefore, the cam torque exerted in the
direction in which intake camshaft 1120 is rotated increases.
[0049] A similar state to the above-described one may also occur in
"A" bank 1010. As shown in FIG. 5, in the phase in which respective
intake valves 1100 of #2 cylinder and #6 cylinder are closed, the
cam torque exerted in the direction opposite to the rotational
direction of intake camshaft 1120 is larger. Further, in the phase
in which intake valve 1100 of #4 cylinder is closed, the cam torque
exerted in the rotational direction of intake camshaft 1120 is
larger.
[0050] It is noted that, in FIG. 5, the solid line represents the
cam torque exerted on intake camshaft 1120 provided to "B " bank
1012. The broken line represents the cam torque exerted on intake
camshaft 1120 provided to "A" bank 1010. The dots each represent
the cam torque at a crank angle at which intake valve 1100 of each
cylinder 1040 is closed.
[0051] Moreover, in FIG. 5, the cam torque exerted in the direction
opposite to the rotational direction of intake camshaft 1120 is
represented by a positive value and the cam torque exerted in the
rotational direction of intake camshaft 1120 is represented by a
negative value.
[0052] If the cam torque exerted in the direction opposite to the
rotational direction of intake camshaft 1120 is larger, the phase
in which intake valve 1100 is actually closed is later than a phase
determined under control, due to influences of deformation or the
like of such components as the chain coupling the crankshaft and
camshafts and other parts. Accordingly, the phase in which
respective intake valves 1100 of #1 cylinder, #3 cylinder, #2
cylinder and #6 cylinder are actually closed is later than the
phase in which respective intake valves 1100 of other cylinders are
closed.
[0053] On the contrary, if the cam torque exerted in the rotational
direction of intake camshaft 1120 is larger, the phase in which
intake valve 1100 is actually closed is earlier than a phase
determined under control, due to influences of deformation or the
like of such components as the chain coupling the crankshaft and
camshafts and other parts. Accordingly, the phase in which
respective intake valves 1100 of #7 cylinder and #4 cylinder are
actually closed is earlier than the phase in which respective
intake valves 1100 of other cylinders are closed.
[0054] In cylinder 1040 having intake valve 1100 closed in a phase
as delayed, the quantity of air pushed back from cylinder 1040 into
the intake manifold as piston 1080 is lifted increases, resulting
in a decrease in final quantity of air sucked into cylinder
1040.
[0055] On the contrary, in cylinder 1040 having intake valve 1100
closed in a phase as advanced, the quantity of air pushed back from
cylinder 1040 into the intake manifold as piston 1080 is lifted
decreases, resulting in an increase in final quantity of air sucked
into cylinder 1040.
[0056] Thus, the cylinders differ from each other in intake air
quantity. In this case, fluctuation of the rotation of crankshaft
1090 (fluctuation of the rotational speed while one rotation is
made) increases, and accordingly vibrations and noise of engine
1000 could increase.
[0057] Then, in the present embodiment, the phase in which intake
valve 1100 is closed is corrected so that the difference in
quantity of air sucked into cylinder 1040 is decreased as much as
possible. The phase in which intake valve 1100 is closed is
corrected, as shown in FIG. 6, based on the map defining, according
to the cam torque, the extent to which the phase should be
corrected.
[0058] The phase in which intake valve 1100 is closed is corrected,
in the case where the crank angle is a crank angle at which the cam
torque is exerted in the direction opposite to the rotational
direction of intake camshaft 1120, so that the phase is advanced
relative to a reference phase defined by the map shown in FIG. 2
(the phase determined from engine speed NE and intake air quantity
KL).
[0059] In contrast, the phase in which intake valve 1100 is closed
is corrected, in the case where the crank angle is a crank angle at
which the cam torque is exerted in the rotational direction of
intake camshaft 1120, so that the phase is retarded relative to the
reference phase defined by the map shown in FIG. 2.
[0060] Referring to FIG. 7, a description is given of a control
structure of a program executed by ECU 4000 that is a control
apparatus according to the present embodiment.
[0061] In step (hereinafter step is abbreviated as S) 100, ECU 4000
detects the crank angle based on a signal (pulse signal)
transmitted from crank angle sensor 5000.
[0062] In S200, ECU 4000 corrects, based on the detected crank
angle and the aforementioned map (see FIG. 6), the phase in which
intake valve 1100 of each cylinder 1040 is closed to a phase that
is advanced or retarded relative to the reference phase. Intake VVT
mechanism 2000 is controlled so that the corrected phase is
implemented. After this, this process is ended.
[0063] A description is given of an operation of ECU 4000 that is
the control apparatus in the present embodiment based on the
above-described structure and flowchart.
[0064] While the engine is operating, the crank angle is detected
(S 100) and, at a crank angle at which the cam torque is exerted in
the direction opposite to the rotational direction of intake
camshaft 1120, the phase in which intake valve 1100 is closed is
advanced (S200).
[0065] Thus, in the case where the cam torque exerted in the
direction opposite to the rotational direction of intake camshaft
1120 could retard the phase in which intake valve 1100 is actually
closed, the phase of intake valve 1100 can be advanced.
Accordingly, occurrence of delay in phase in which intake valve
1100 is actually closed can be restrained.
[0066] Further, at a crank angle at which the cam torque is exerted
in the rotational direction of intake camshaft 1120, the phase in
which intake valve 1100 is closed is retarded (S200). Thus, in the
case where the cam torque exerted in the rotational direction of
intake camshaft 1120 could advance the phase in which intake valve
1100 is actually closed, the phase of intake valve 1100 can be
retarded. Accordingly, occurrence of advance in phase in which
intake valve 1100 is actually closed can be restrained.
[0067] As discussed above, with the ECU identified as the control
apparatus in the present embodiment, at a crank angle at which the
cam torque is exerted in the direction opposite to the rotational
direction of the intake camshaft, the intake VVT mechanism is
controlled so that the phase in which the intake valve is closed is
advanced. Further, at a crank angle at which the cam torque is
exerted in the rotational direction of the intake camshaft, the
intake VVT mechanism is controlled so that the phase in which the
intake valve is closed is retarded. Thus, for a cylinder, in the
case where the cam torque exerted in the direction opposite to the
rotational direction of the intake camshaft could retard the phase
in which the intake valve of the cylinder is actually closed, the
phase in which the intake valve is closed can be advanced.
Accordingly, occurrence of delay in phase in which the intake valve
is actually closed can be restrained. In contrast, for a cylinder,
in the case where the cam torque exerted in the rotational
direction of the camshaft could advance the phase in which the
intake valve of the cylinder is actually closed, the phase in which
the intake valve is closed can be retarded. Accordingly, occurrence
of advance in phase in which the intake valve is actually closed
can be restrained. In this way, occurrence of displacement can be
restrained of the phase in which the intake valve of each cylinder
is actually closed, with respect to a phase determined under
control, and occurrence of nonuniformity of cylinders with respect
to each other in terms of quantity of air sucked into the cylinder
can be restrained.
Other Embodiments
[0068] In such cases where the rotational speed of intake camshaft
1120 is high and where the load of engine 1000 is high, namely the
case where the absolute value of the cam torque is relatively
large, the extent to which the phase is corrected may be larger
than the one used in the case where the absolute value of the cam
torque is relatively small. In other words, in the case where the
cam torque exerted in the direction opposite to the direction in
which intake camshaft 1120 is rotated is relatively large, the
phase in which intake valve 1100 is closed may be advanced to a
greater extent than the one used in the case where the
aforementioned cam torque is relatively small. Further, in the case
where the absolute value of the cam torque exerted in the
rotational direction of intake camshaft 1120 is relatively large,
the phase in which intake valve 1100 is closed may be retarded to a
greater extent than the one used in the case where the
aforementioned absolute value is relatively small.
[0069] In this way, as the phase in which intake valve 1100 is
actually closed is delayed to a greater extent, the phase of intake
valve 1100 may be advanced to a greater extent. Further, as the
phase in which intake valve 1100 is actually closed is advanced to
a greater extent, the phase of intake valve 1100 may be retarded to
a greater extent. Thus, occurrence of displacement of the phase in
which the intake valve of each cylinder is actually closed with
respect to a phase determined under control can be restrained, and
occurrence of nonuniformity of cylinders with respect to each other
in terms of intake air quantity can be restrained.
[0070] Furthermore, in addition to or instead of intake valve 1100,
exhaust valve 1110 may be advanced or retarded in phase according
to the cam torque. This is because of the fact that a cylinder
having exhaust valve 1100 closed in a delayed phase has an
increased internal EGR quantity while a cylinder having exhaust
valve 1100 closed in an advanced phase has a decreased internal EGR
quantity, resulting in nonuniformity of cylinders with respect to
each other in internal EGR quantity and increased rotational
fluctuations of engine 1000.
[0071] Thus, for cylinder 1040, in the case where the cam torque
exerted in the direction opposite to the rotational direction of
exhaust camshaft 1130 could delay the phase in which exhaust valve
1110 is actually closed, the phase of exhaust valve 1110 can be
advanced. Accordingly, occurrence of delay of the phase in which
exhaust valve 1110 is actually closed can be restrained.
[0072] Further, for cylinder 1040, in the case where the cam torque
exerted in the rotational direction of exhaust camshaft 1130 could
advance the phase in which exhaust valve 1110 is actually closed,
the phase of exhaust valve 1110 can be retarded. Accordingly,
occurrence of advance of the phase in which exhaust valve 1110 is
actually closed can be restrained. Consequently, for each cylinder,
occurrence of displacement of the phase in which exhaust valve 1110
is actually closed with respect to a phase determined under control
can be restrained, and occurrence of nonuniformity of cylinders
with respect to each other in terms of internal EGR quantity can be
restrained.
[0073] 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.
* * * * *