U.S. patent application number 12/630190 was filed with the patent office on 2010-06-10 for variable valve timing control apparatus for internal combustion engine.
This patent application is currently assigned to DENSO CORPORATION. Invention is credited to Yuichi TAKEMURA.
Application Number | 20100139593 12/630190 |
Document ID | / |
Family ID | 42229647 |
Filed Date | 2010-06-10 |
United States Patent
Application |
20100139593 |
Kind Code |
A1 |
TAKEMURA; Yuichi |
June 10, 2010 |
VARIABLE VALVE TIMING CONTROL APPARATUS FOR INTERNAL COMBUSTION
ENGINE
Abstract
A variable valve timing control apparatus for an engine includes
a variable valve timing unit, a lock pin, a hydraulic control unit,
and an oil filling control unit. An operation mode of the hydraulic
control unit is changed between a lock mode, in which the lock pin
locks the camshaft phase at the intermediate lock phase, and a
phase feed-back control mode, in which the camshaft phase is
controlled to a target phase. The oil filling control unit supplies
oil to an advance chamber and a retard chamber of the variable
valve timing unit before the operation mode is changed from the
lock mode to the phase feed-back control mode after an engine
start. The oil filling control unit causes the lock pin to keep
locking the camshaft phase until the oil filling control is
completed after the engine start.
Inventors: |
TAKEMURA; Yuichi;
(Toyohashi-city, JP) |
Correspondence
Address: |
NIXON & VANDERHYE, PC
901 NORTH GLEBE ROAD, 11TH FLOOR
ARLINGTON
VA
22203
US
|
Assignee: |
DENSO CORPORATION
Kariya-city
JP
|
Family ID: |
42229647 |
Appl. No.: |
12/630190 |
Filed: |
December 3, 2009 |
Current U.S.
Class: |
123/90.17 |
Current CPC
Class: |
F01L 2001/34463
20130101; F01L 2001/34476 20130101; F01L 1/3442 20130101; F01L
2001/34453 20130101; F01L 2800/01 20130101; F01L 2001/34466
20130101 |
Class at
Publication: |
123/90.17 |
International
Class: |
F01L 1/34 20060101
F01L001/34 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 9, 2008 |
JP |
2008-312843 |
Claims
1. A variable valve timing control apparatus for an internal
combustion engine that has a camshaft and a crankshaft, comprising:
a variable valve timing unit adapted to adjust valve timing by
shifting a camshaft phase that is a rotational angular position of
the camshaft relative to a rotational angular position of the
crankshaft; a lock pin adapted to lock the camshaft phase at an
intermediate lock phase that is generally middle of an adjustable
range of the camshaft phase; a hydraulic control unit adapted to
control oil pressure that actuates the variable valve timing unit
and the lock pin, wherein an operation mode of the hydraulic
control unit is changed between a lock mode, in which the lock pin
locks the camshaft phase at the intermediate lock phase, and a
phase feed-back control mode, in which the camshaft phase is
controlled to a target phase; and oil filling control means for
executing oil filling control for supplying oil to an advance
chamber and a retard chamber of the variable valve timing unit
before the operation mode is changed from the lock mode to the
phase feed-back control mode after a start of the internal
combustion engine, wherein: the oil filling control means causes
the lock pin to keep locking the camshaft phase by prohibiting the
lock pin from releasing the locked camshaft phase until the oil
filling control is completed after the start of the internal
combustion engine.
2. The variable valve timing control apparatus according to claim
1, wherein: the oil filling control means executes the oil filling
control until a certain time period elapses since the start of the
internal combustion engine.
3. The variable valve timing control apparatus according to claim
1, wherein: the hydraulic control unit includes a first hydraulic
control valve and a second hydraulic control valve, the first
hydraulic control valve controlling oil pressure for actuating the
variable valve timing unit, the second hydraulic control valve
controlling oil pressure for actuating the lock pin; the oil
filling control means maintains a control amount of the second
hydraulic control valve at a value for causing the lock pin to keep
locking the camshaft phase during an execution period for executing
the oil filling control; and the oil filling control means also
changes a control amount of the first hydraulic control valve
during the execution period in order to firstly execute one of (a)
advance chamber oil filling control for supplying oil to the
advance chamber and (b) retard chamber oil filling control for
supplying oil to the retard chamber and in order to subsequently
execute the other one of (a) the advance chamber oil filling
control and (b) the retard chamber oil filling control.
4. The variable valve timing control apparatus according to claim
1, wherein: the oil filling control means stops the oil filling
control and changes a control amount of the hydraulic control unit
such that the camshaft phase is controlled to a full retard phase
or a full advance phase when it is detected that the lock pin does
not lock the camshaft phase based on detection of change of the
camshaft phase during the execution of the oil filling control.
5. The variable valve timing control apparatus according to claim
4, wherein: a target idling rotational speed of the internal
combustion engine indicates a first value while the lock pin locks
the camshaft phase; and the oil filling control means includes
means for increasing the target idling rotational speed after the
start of the internal combustion engine to be a second value that
is higher than the first value when it is detected that the lock
pin does not lock the camshaft phase during the execution of the
oil filling control.
6. The variable valve timing control apparatus according to claim
4, wherein: when it is detected that the lock pin does not lock the
camshaft phase during the execution of the oil filling control, the
oil filling control means executes the followings: the oil filling
control means stops the oil filling control; and the operation mode
is changed to a normal control after the oil filling control means
controls the camshaft phase at a full retard phase or at a full
advance phase until a certain time period that is shorter than a
time required for completing the oil filling control elapses.
7. The variable valve timing control apparatus according to claim
1, wherein: the hydraulic control unit employs a hydraulic control
valve that controls oil pressure for actuating the variable valve
timing unit and the lock pin: the oil filling control means changes
a control amount of the hydraulic control valve such that oil is
firstly supplied to one of the advance chamber and the retard
chamber while the lock pin locks the camshaft phase after the start
of the internal combustion engine; and the oil filling control
means changes the control amount of the hydraulic control valve
such that oil is subsequently supplied to the other one of the
advance chamber and the retard chamber until a certain time period
elapses or until the camshaft phase starts shifting when a first
lock release request since the engine start is issued.
8. The variable valve timing control apparatus according to claim
7, wherein: when it is detected that the lock pin does not lock the
camshaft phase during the execution of the oil filling control, the
operation mode is changed to a normal control after the oil filling
control means supplies oil to the other one of the advance chamber
and the retard chamber.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application is based on and incorporates herein by
reference Japanese Patent Application No. 2008-312843 filed on Dec.
9, 2008.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a variable valve timing
control apparatus that adjusts valve timing of an internal
combustion engine.
[0004] 2. Description of Related Art
[0005] In a conventional hydraulic variable valve timing unit, as
shown in JP-A-H9-324613 (corresponding to U.S. Pat. No. 5,738,056)
and JP-A-2001-159330 (corresponding to U.S. Pat. No. 6,330,870), a
lock phase during engine stop is set at a generally middle phase
within an adjustable range of a camshaft phase such that the
adjustable range of valve timing (camshaft phase) is enlarged. In
the above conventional art, an intermediate lock phase, at which
the phase is locked during the engine stop, is set at a phase
suitable for starting the engine. The engine is started while the
camshaft phase is at the intermediate lock phase. Also, after
starting the engine, the lock is released such that the camshaft
phase is shifted toward a target phase that is set in accordance
with an engine operational state.
[0006] In the variable valve timing unit, oil in the advance
chamber (advance-side hydraulic chamber) and in the retard chamber
(retard-side hydraulic chamber) are released while the engine
stops, and thereby oil pressure in each of the hydraulic chambers
is reduced. As a result, if the lock release is executed
immediately when the lock release request is issued after the
engine start, oil (oil pressure) may not be sufficiently supplied
to each hydraulic chamber at the time of issuing. When the lock
release is executed in a state, where oil is not sufficiently
supplied to each hydraulic chamber (or where each hydraulic chamber
has insufficient oil pressure therein), it becomes impossible to
maintain the camshaft phase at the moment of unlocking the lock
pin. As a result, the wide variation of the camshaft phase, in
which the camshaft phase is rapidly changed toward the hydraulic
chamber having a lower oil pressure, occurs, and thereby combustion
performance may deteriorate, or engine rotation may become unstable
disadvantageously.
SUMMARY OF THE INVENTION
[0007] The present invention is made in view of the above
disadvantages. Thus, it is an objective of the present invention to
address at least one of the above disadvantages.
[0008] To achieve the objective of the present invention, there is
provided a variable valve timing control apparatus for an internal
combustion engine that has a camshaft and a crankshaft, the
variable valve timing control apparatus including a variable valve
timing unit, a lock pin, a hydraulic control unit, and an oil
filling control unit. The variable valve timing unit is adapted to
adjust valve timing by shifting a camshaft phase that is a
rotational angular position of the camshaft relative to a
rotational angular position of the crankshaft. The lock pin is
adapted to lock the camshaft phase at an intermediate lock phase
that is generally middle of an adjustable range of the camshaft
phase. The hydraulic control unit is adapted to control oil
pressure that actuates the variable valve timing unit and the lock
pin, wherein an operation mode of the hydraulic control unit is
changed between a lock mode, in which the lock pin locks the
camshaft phase at the intermediate lock phase, and a phase
feed-back control mode, in which the camshaft phase is controlled
to a target phase. The oil filling control unit executes oil
filling control for supplying oil to an advance chamber and a
retard chamber of the variable valve timing unit before the
operation mode is changed from the lock mode to the phase feed-back
control mode after a start of the internal combustion engine. The
oil filling control unit causes the lock pin to keep locking the
camshaft phase by prohibiting the lock pin from releasing the
locked camshaft phase until the oil filling control is completed
after the start of the internal combustion engine.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] The invention, together with additional objectives, features
and advantages thereof, will be best understood from the following
description, the appended claims and the accompanying drawings in
which:
[0010] FIG. 1 is a general schematic configuration of a control
system according to the first embodiment of the present
invention;
[0011] FIG. 2 is a diagram illustrating a variable valve timing
unit and an oil pressure control circuit of the first
embodiment;
[0012] FIG. 3 is a sectional view of the variable valve timing unit
of the first embodiment taken along a plane perpendicular to a
longitudinal axis of the variable valve timing unit;
[0013] FIG. 4 is a timing chart illustrating a control example of
the first embodiment, in which example an engine is started while
an actual camshaft phase is located at an intermediate lock
phase;
[0014] FIG. 5 is a timing chart illustrating another control
example of the first embodiment, in which example the engine is
started while a lock pin is disengaged from a lock hole;
[0015] FIG. 6 is a flow chart illustrating a procedure of a
start-time variable valve timing control routine in the first
embodiment;
[0016] FIG. 7 is a diagram illustrating a variable valve timing
unit and an oil pressure control circuit of the second embodiment
of the present invention;
[0017] FIG. 8A is a diagram for explaining a switching pattern for
switching an operational state of an advance port, a retard port,
and a lock pin control port of a hydraulic control valve of the
second embodiment;
[0018] FIG. 8B is a control characteristic diagram of the hydraulic
control valve for explaining a relation between (a) a phase change
speed and (b) four control ranges of a control duty including a
lock mode, an advance mode, a hold mode, a retard mode;
[0019] FIG. 9 is flow chart illustrating a procedure of a
post-start oil filling control routine of the second
embodiment;
[0020] FIG. 10 is a flow chart illustrating a procedure of a
lock-release-request-time oil filling control routine of the second
embodiment; and
[0021] FIG. 11 is a flow chart illustrating a procedure of an
unlocked-time oil filling control routine of the second
embodiment.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0022] First and the second embodiments, which applies the present
invention to a variable valve timing control apparatus for
adjusting an intake valve, will be described below.
The First Embodiment
[0023] The first embodiment of the present invention will be
described with reference to FIGS. 1 to 6.
[0024] As shown in FIG. 1, an engine 11 (internal combustion
engine) transmits drive force from a crankshaft 12 to an intake
camshaft 16 and an exhaust camshaft 17 through a timing chain 13
and sprockets 14, 15. The intake camshaft 16 is provided with a
variable valve timing unit 18 that adjusts an advance amount (or a
camshaft phase) of the intake camshaft 16 relative to the
crankshaft 12. More specifically, the camshaft phase is a
rotational angular position of the intake camshaft 16 relative to a
rotational angular position of the crankshaft 12.
[0025] Also, a cam angle sensor 19 is provided at a position
radially outward of the intake camshaft 16 for outputting cam angle
signal pulses at predetermined cam angles in order to identify
cylinders. Also, a crank angle sensor 20 is provided at a position
radially outward of the crankshaft 12 for outputting crank angle
signal pulses at predetermined crank angles. The signals outputted
from the cam angle sensor 19 and the crank angle sensor 20 are fed
to an engine control circuit 21. The engine control circuit 21
computes actual valve timing (actual camshaft phase) of the intake
valve and computes an engine rotation speed based on a frequency
(pulse interval) of the output pulses of the crank angle sensor 20.
Also, the other signals outputted by various sensors (an intake air
pressure sensor 22, a coolant temperature sensor 23, a throttle
sensor 24) for detecting an engine operational state are fed to the
engine control circuit 21.
[0026] The engine control circuit 21 executes fuel injection
control and ignition control based on the engine operational state
detected by the various sensors. Also, the engine control circuit
21 executes variable valve timing control (phase feed-back
control), in which the engine control circuit 21 feed-back controls
oil pressure that actuates the variable valve timing unit 18 such
that the actual valve timing of the intake valve (or an actual
camshaft phase of the intake camshaft 16) becomes target valve
timing (target phase).
[0027] Next, the variable valve timing unit 18 will be described
with reference to FIGS. 2 and 3.
[0028] The variable valve timing unit 18 has a housing 31 that is
fixed to the sprocket 14 through a bolt 32. The sprocket 14 is
movably supported at a position radially outward of the intake
camshaft 16. Thus, when the rotation of the crankshaft 12 is
transmitted to the sprocket 14 and the housing 31 through the
timing chain 13, the sprocket 14 and the housing 31 are rotated
synchronously with the crankshaft 12.
[0029] The intake camshaft 16 has one end portion that is fixed to
a rotor 35 through a bolt 37. The rotor 35 is received within the
housing 31 and is rotatable relative to the housing 31.
[0030] As shown in FIG. 3, multiple oil filled chambers 40 are
formed within the housing 31, and vanes 41 are formed at radially
outward parts of the rotor 35. Each of the oil filled chambers 40
is divided into an advance chamber 42 (advance hydraulic chamber)
and a retard chamber 43 (retard hydraulic chamber) by the
corresponding vane 41. At least one of the vanes 41 has both
circumferential ends that are provided with respective stoppers 56.
Each of the stoppers 56 limits a rotational range of the rotor 35
(the vane 41) relative to the housing 31. The stoppers 56 defines a
full retard phase and a full advance phase of an adjustable range
of the camshaft phase.
[0031] The variable valve timing unit 18 is provided with an
intermediate lock mechanism 50 that is adapted to lock the camshaft
phase at an intermediate lock phase. For example, the intermediate
lock phase corresponds to a position (phase) that is located
generally middle of the above adjustable range. The intermediate
lock mechanism 50 will be described below. A lock pin receiving
hole 57 is provided to one of the multiple vanes 41, or multiple
lock pin receiving holes 57 may be provided to the multiple vanes
41, respectively. The lock pin receiving hole 57 receives therein a
lock pin 58 that is displaceable to project from the lock pin
receiving hole 57. The lock pin 58 locks the rotation of the rotor
35 (the vane 41) relative to the housing 31 when the lock pin 58
projects from the lock pin receiving hole 57 toward the sprocket 14
to be inserted into a lock hole 59 of the sprocket 14. As a result,
the camshaft phase is locked at the intermediate lock phase located
generally in the middle of the adjustable range. The intermediate
lock phase is set at a position that is suitable for starting the
engine 11. It should be noted that the lock hole 59 may be
alternatively provided to the housing 31.
[0032] The lock pin 58 is urged by a spring 62 in a lock direction
for locking the camshaft phase. In other words, the lock pin 58 is
urged in a projection direction, in which the lock pin 58 is
capable of projecting from the lock pin receiving hole 57. Also, an
hydraulic chamber for releasing the lock is formed between (a) the
radially outward part of the lock pin 58 and (b) the lock pin
receiving hole 57. The hydraulic chamber is used to control oil
pressure that actuates the lock pin 58 in a lock release direction
for unlocking the rotation of the rotor 35 to release the locked
camshaft phase such that the lock pin 58 does not lock the camshaft
phase. For example, when the pressure in the hydraulic chamber
becomes high, the lock pin 58 is displaced in the lock release
direction. Also, when the pressure in the hydraulic chamber becomes
low, or is released, the lock pin 58 is urged in the lock direction
by the urging force of the spring 62. It should be noted that the
housing 31 is provided with a helical torsion spring 55 (see FIG.
2) that provides spring force for assisting oil pressure applied to
rotate the rotor 35 relatively in an advance direction during
advance control.
[0033] In the first embodiment, a hydraulic control unit, which
controls oil pressure that actuates the variable valve timing unit
18 and the lock pin 58, includes a phase-control hydraulic control
valve 25 (first hydraulic control valve) and a lock-control
hydraulic control valve 26 (second hydraulic control valve). The
phase-control hydraulic control valve 25 controls oil pressure that
actuates the variable valve timing unit 18, and the lock-control
hydraulic control valve 26 controls oil pressure that actuates the
lock pin 58. For example, the phase-control hydraulic control valve
25 is a five-port and three-position type spool valve, and the
lock-control hydraulic control valve 26 is a three-port and
two-position type spool valve.
[0034] An oil pump 28 is driven by drive force of the engine 11,
and the oil pump 28 pumps oil within an oil pan 27 to supply oil to
each of hydraulic control valves 25, 26. The phase-control
hydraulic control valve 25 controls oil pressure (oil amount)
supplied to the advance chambers 42 and the retard chambers 43 of
the variable valve timing unit 18. The lock-control hydraulic
control valve 26 controls oil pressure (oil amount) that actuates
the lock pin 58 in the lock release direction. It should be noted
that the phase-control hydraulic control valve 25 is provided with
a check valve 29 at an inlet port side of the hydraulic control
valve 25, the check valve 29 limiting backflow of oil.
[0035] The engine control circuit 21 computes a target phase
(target valve timing) based on an engine operational condition
during the phase feed-back control (variable valve timing control)
in order to feed-back control a control duty (control amount) of
the phase-control hydraulic control valve 25 such that an actual
camshaft phase of the intake camshaft 16 (actual valve timing of
the intake valve) is caused to become a target phase (target valve
timing). Thus, pressure of oil supplied to the advance chambers 42
and the retard chambers 43 of the variable valve timing unit 18 is
feed-back controlled by the feed back control of the control
duty.
[0036] When a lock request is issued during the phase feed-back
control, a lock control will be executed as follows. For example,
in the lock control, the lock pin 58 is caused to be fitted into
the lock hole 59 of the sprocket 14 such that the actual camshaft
phase is locked at the intermediate lock phase. Firstly, the
operational position of the lock-control hydraulic control valve 26
is changed to the drain port for releasing oil pressure in the lock
release hydraulic chamber within the lock pin receiving hole 57
such that the spring 62 urges to displace the lock pin 58 in the
lock direction. Then, a phase shift control is executed, in which
the phase-control hydraulic control valve 25 is controlled such
that the actual camshaft phase is shifted in a shift-control
direction to a position beyond the intermediate lock phase while
the spring 62 urges the lock pin 58 in the lock direction
(projection direction). When the actual camshaft phase stops round
the intermediate lock phase during the phase shift control, the
control duty of the phase-control hydraulic control valve 25 is
further changed by a certain amount such that the actual camshaft
phase is further shifted in the shift-control direction. In a case,
where the actual camshaft phase is not shifted even after the above
further change of the control duty, it is determined that the lock
has been completed. For example, the completion of the lock
indicates that the actual camshaft phase has been locked at the
intermediate lock phase by fitting the lock pin 58 into the lock
hole 59.
[0037] In the first embodiment, in order to reliably execute the
lock control of the lock pin 58 and the determination of the
completion of the lock, the following control is executed. For
example, when the actual camshaft phase stops around the
intermediate lock phase during the phase shift control, the control
duty of the phase-control hydraulic control valve 25 is changed by
a certain amount alternately (a) for shifting the camshaft phase in
the advance direction and (b) for shifting the camshaft phase in
the retard direction. When the above alternate change of the
control duty does not shift the actual camshaft phase in either
direction, it is finally determined that the lock has been
completed.
[0038] Also, in order to start the engine 11, the engine 11 is
cranked by a starter (not shown) in a state, where the lock pin 58
locks the actual camshaft phase at the intermediate lock phase.
Then, after the starting of the engine, oil filling control for
supplying oil to the advance chambers 42 and the retard chambers 43
of the variable valve timing unit 18 is executed before the
operation mode is changed from a lock mode (described later) to the
phase feed-back control mode. Also, the lock pin 58 is caused to
keep locking the actual camshaft phase by prohibiting the lock pin
58 from releasing the locked camshaft phase until the oil filling
control is completed after the starting of the engine.
[0039] In the above state, the execution of the oil filling control
may be continued after the engine start until sufficient supply of
oil to each of the hydraulic chambers 42, 43 is detected by using,
for example, pressure sensors. However, the employing the oil
pressure sensors may lead to cost increase, and thereby failing to
satisfy the demand for cost reduction.
[0040] Then, in the first embodiment, the execution of the oil
filling control is continued until a certain time period has
elapsed since engine start (start of the cranking). In other words,
the oil filling control is continued for the certain time period
after the start of the cranking. A time required for sufficiently
supplying each of the hydraulic chambers 42, 43 with oil is
measurable in advance based on design data and experimental data,
and thereby an execution duration for executing the oil filling
control may be preset based on the design data and the experimental
data. Thus, it is possible to satisfy the demand for cost reduction
by controlling the execution duration of the oil filling control by
using a timer, and thereby by simplifying the configuration
advantageously.
[0041] The first embodiment has a configuration that includes both
(a) the phase-control hydraulic control valve 25 for controlling
oil pressure that actuates the variable valve timing unit 18 and
(b) the lock-control hydraulic control valve 26 for controlling oil
pressure that actuates the lock pin 58. Typically, the
phase-control hydraulic control valve 25 is operated independently
from the lock-control hydraulic control valve 26. Thus, it is
possible to control the phase-control hydraulic control valve 25 in
the advance direction or in the retard direction while the
lock-control hydraulic control valve 26 is controlled in the lock
direction.
[0042] In consideration of the above configuration, during the
execution period of the oil filling control of the first
embodiment, while control duty of the lock-control hydraulic
control valve 26 is maintained at a value for maintaining the lock
pin 58 in a lock position for locking the camshaft phase at the
intermediate lock phase, control duty of the phase-control
hydraulic control valve 25 is changed such that one of advance
chamber oil filling control and retard chamber oil filling control
is executed first, and then the other one of the advance chamber
oil filling control and the retard chamber oil filling control
subsequently. In the advance chamber oil filling control, oil is
supplied to the advance chamber 42 such that the advance chamber 42
is filled with oil. Also, in the retard chamber oil filling
control, oil is supplied to the retard chamber 43 such that the
retard chamber 43 is filled with oil. Due to the above, during the
execution period of the oil filling control (the advance chamber
oil filling control and the retard chamber oil filling control),
the advance chamber 42 and the retard chamber 43 are reliably
filled with oil while the lock pin 58 is maintained at the lock
position (or while the lock pin 58 keeps locking the camshaft phase
at the intermediate lock phase).
[0043] Also, in a case, where the disengagement of the lock pin 58
from the lock hole 59 (or unlock of the lock pin 58) is detected
during the execution of the oil filling control based on the
detection of the shift of the actual camshaft phase, the oil
filling control is stopped. Then, control duty of the phase-control
hydraulic control valve 25 is changed such that the actual camshaft
phase is shifted to the full retard phase (or to the full advance
phase). For example, in general, in a case, where the lock pin 58
is unlocked while the advance chambers 42 and the retard chambers
43 are not sufficiently filled with oil, the actual camshaft phase
becomes unstable, and thereby the actual camshaft phase may widely
vary. Thus, immediately after the detection of that the lock pin 58
does not lock the camshaft phase during the execution of the oil
filling control, the oil filling control is stopped and only one of
(a) the advance chambers 42 and (b) the retard chambers 43 is
filled with oil. As a result, the actual camshaft phase is quickly
shifted to the full retard phase (or the full advance phase) within
the adjustable range such that the wide unwanted variation of the
actual camshaft phase is quickly and successfully prevented.
[0044] Furthermore, in the first embodiment, a target idling
rotational speed of the internal combustion engine indicates a
first value while the lock pin 58 locks the camshaft phase. The
target idling rotational speed after the start of the internal
combustion engine is increased to be a second value that is higher
than the first value when it is detected that the lock pin 58 does
not lock the camshaft phase during the execution of the oil filling
control. Simultaneously, when it is detected that the lock pin 58
does not lock the camshaft phase during the execution of the oil
filling control, the actual camshaft phase is controlled at the
full retard phase or at the full advance phase until a certain time
period that is shorter than a time required for completing the oil
filling control elapses. The operation mode is changed to the
normal control (the lock control or the phase feed-back control)
after the above operation.
[0045] As above, if the target idling rotational speed of the fast
idle is increased upon the detection of the unlock of the lock pin
58 during the execution of the oil filling control, a rotational
speed (oil discharge rate) of the oil pump 28 is increased such
that the advance chamber 42 or the retard chamber 43 is more
quickly and effectively filled with oil. As a result, it is
possible to suppress the unwanted variation of the actual camshaft
phase, and thereby it is possible to effectively prevent the
deterioration of combustion and the variation in the rotation of
the engine 11 advantageously.
[0046] For example, it take a shorter time to sufficiently fulfill
only one of the advance chamber 42 and the retard chamber 43 with
oil to shift the camshaft phase to the full retard phase or to the
full advance phase than to fulfill both of the chambers 42, 43.
Thus, even when the unlock of the lock pin 58 is detected during
the execution of the oil filling control, the operation is
relatively quickly recovered to a normal control while the wide
variation of the camshaft phase is limited by firstly shifting the
camshaft phase to the full retard phase or the full advance phase
before changing the operation to the normal control.
[0047] A control example of the variable valve timing unit 18 of
the first embodiment at a time of starting the engine will be
described with reference to FIG. 4 and FIG. 5.
[0048] FIG. 4 is a control example, in which the engine 11 is
cranked by a starter in a state, where the lock pin 58 locks the
actual camshaft phase at the intermediate lock phase. In the
example of FIG. 4, the cranking is started at time t1, and
simultaneously the advance chamber oil filling control is executed
by changing the control duty of the phase-control hydraulic control
valve 25 to an advance-side duty in order to fill the advance
chamber 42 with oil. For example, the advance-side duty may be a
control duty of 0% and may correspond to a full advance phase. The
cranking is ended at time t2, at which the starting of the engine
11 has been completed, and then operation is changed to a normal
fast idle control, where the engine rotation speed is controlled at
the target idling rotational speed of the fast idle in a normal
operation.
[0049] The advance chamber oil filling control has been executed
for a certain time period B until time t3. Then, at time t3, the
retard chamber oil filling control is executed by changing the
control duty of the phase-control hydraulic control valve 25 to a
retard-side duty in order to fill the retard chamber 43 with oil.
For example, the retard-side duty may be a control duty of 100% and
may correspond to a full retard phase. The lock release (unlock) of
the lock pin 58 is prohibited during a period from the start of the
cranking till the end of the advance chamber oil filling control
and the retard chamber oil filling control, and thereby the lock
pin 58 remains at the lock position, at which the lock pin 58 keeps
locking the camshaft phase at the intermediate lock phase.
[0050] Then, operation is changed to a normal control (lock control
or phase feed-back control) at time t4, by which the retard chamber
oil filling control has been executed for a certain time period C.
In order to execute the lock control as shown in FIG. 4, the
control duty of the phase-control hydraulic control valve 25 is
changed to a certain control duty such that the lock pin 58 within
the lock hole 59 is displaced in a rotational direction (in the
retard direction or in the advance direction) of the rotor 35.
Thus, the lock pin 58 is held and is slightly pressed against an
inner peripheral edge of the lock hole 59, and thereby the wide
variation of the actual camshaft phase is prevented. For example,
the above certain control duty may be apart from a hold duty, which
is used for maintaining the actual camshaft phase, by a
predetermined amount in the retard direction or in the advance
direction.
[0051] Also, when the lock release request is issued during the
execution of the lock control (lock mode), the operational position
of the lock-control hydraulic control valve 26 is changed from the
drain port to the oil pressure supply port such that oil pressure
is supplied to the lock release hydraulic chamber within the lock
pin receiving hole 57 in order to actuate the lock pin 58 in the
lock release direction for the lock release. In the above, the
operation mode is prevented from being changed into the phase
feed-back control mode for a certain period after the lock release
request is issued. Simultaneously, the control duty of the
phase-control hydraulic control valve 25 is controlled such that
the actual camshaft phase is controlled around the intermediate
lock phase while the lock pin 58 is actuated in the lock release
direction. Then, when the certain period has elapsed since the time
of issuing the lock release request, operation is changed to the
phase feed-back control mode.
[0052] As above, the change to the phase feed-back control mode is
prohibited for the certain period since the lock release request is
issued, and also during the above period, the lock release control
is executed while the actual camshaft phase is controlled around
the intermediate lock phase, for example, by adjusting the control
duty at the certain control duty that is apart from the hold duty
by the predetermined amount in the retard direction or in the
advance direction. As a result, it is possible to effectively
disengage the lock pin 58 from the lock hole 59. More specifically,
due to the above operation, while the lock pin 58 is pulled out of
the lock hole 59, the lock pin 58 is effectively limited from being
urged against the inner peripheral edge of the lock hole 59 by the
driving force for shifting the actual camshaft phase by the phase
feed-back control. As a result, the possible failure in the
disengagement of the lock pin 58 from the lock hole 59 is
successfully prevented. Accordingly, after the lock release has
been ended, the operation mode is changed into the phase feed-back
control mode. Thus, when the lock release request is issued, it is
possible to reliably start shifting the actual camshaft phase to
the target phase (or it is possible to reliably start the phase
feed-back control) after the lock has been released.
[0053] In contrast, FIG. 5 is a control example, in which the
engine 11 is cranked by the starter for starting the engine 11 in
an unlock position, where the lock pin 58 is unlocked. Similar to
the other control example in FIG. 4, the control duty of the
phase-control hydraulic control valve 25 is also set at the control
duty of 0% for the full advance phase in order to start the advance
chamber oil filling control at time t1, at which the cranking is
started. During the execution of the oil filling control (the
advance chamber oil filling control and the retard chamber oil
filling control), the unlock of the lock pin 58 is detected based
on detection of the change of the camshaft phase at time t2. Then,
the advance chamber oil filling control is stopped. Then, the
target idling rotational speed of the fast idle executed after the
engine start while the lock pin 58 is at the unlock position is set
higher than the target idling rotational speed of the normal fast
idle, in which the lock pin 58 is at the lock position. Also,
simultaneously, the full retard control is executed by changing the
control duty of the phase-control hydraulic control valve 25 at the
control duty of 100% for the full retard phase for a certain time
period such that the actual camshaft phase is shifted to the full
retard phase. For example, the certain time period is shorter than
a time period required for the execution of the oil filling control
(the advance chamber oil filling control and the retard chamber oil
filling control). It should be noted that the full advance control
may be alternatively executed by changing the control duty of the
phase-control hydraulic control valve 25 to the control duty of 0%
for the full advance phase such that the actual camshaft phase is
shifted to the full advance phase.
[0054] When the above certain time period has elapsed at time t3
since the start of the full retard control (or the full advance
control), the full retard control (or the full advance control) is
ended. By this time, oil pressure has been increased due to elapse
of the certain time period, and the operation is changed to the
normal control (for example, the phase feed-back control as shown
in FIG. 5).
[0055] It should be noted that in the examples of FIGS. 4 and 5,
the advance chamber oil filling control is firstly executed after
the start of the cranking, and then the operation is changed to the
retard chamber oil filling control. Alternatively, the retard
chamber oil filling control may be firstly executed, and then the
operation may be changed to the advance chamber oil filling
control.
[0056] The variable valve timing control at the engine start
according to the first embodiment is executed by the engine control
circuit 21 based on a start-time variable valve timing control
routine shown in FIG. 6.
[0057] The start-time variable valve timing control routine of FIG.
6 is repeatedly executed at certain intervals while the engine
control circuit 21 is on (or while the ignition switch is on), and
functions as oil filling control means. When the present routine is
started, firstly, it is determined at step 101 whether the cranking
is being executed or whether a time period that has elapsed since
the engine start is shorter than the certain time period A. When
the cranking has not been executed yet, or when the certain time
period A has already elapsed since the engine start, the start-time
variable valve timing control is not required, and thereby the
present routine is ended without executing the subsequent
process.
[0058] In contrast, when it is determined at step 101 that the
cranking is being executed or that the elapsed time period since
the engine start is shorter than the certain time period A, control
proceeds to step 102, where it is determined whether actual
camshaft phase varies or not. In other words, it is determined at
step 102 whether the actual camshaft phase stably stays around the
intermediate lock phase. When it is determined at step 102 that the
actual camshaft phase does not vary or that the actual camshaft
phase stably stays around the intermediate lock phase, it is
determined that the lock pin 58 is at the lock position. Thus,
control proceeds to step 104, where it is determined whether an
execution duration of the advance chamber oil filling control since
the start of the cranking has reached the certain time period B.
When it is determined that the execution duration of the advance
chamber oil filling control has not reached the certain time period
B, control proceeds to step 105, where the control duty of the
phase-control hydraulic control valve 25 is maintained at 0% to
continue the advance chamber oil filling control for further
filling the advance chamber 42 with oil.
[0059] Then, the execution duration of the advance chamber oil
filling control reaches the certain time period B, control proceeds
from step 104 to step 106, where it is determined whether an
execution duration of the retard chamber oil filling control has
reached a certain time period C. When it is determined that the
execution duration of the retard chamber oil filling control has
not reached the certain time period C, control proceeds to step
107, where the control duty of the phase-control hydraulic control
valve 25 is maintained at 100% in order to continue the retard
chamber oil filling control such that the retard chamber 43 is
further filled with oil.
[0060] When it is determined at step 102 that the lock pin 58 is at
the unlock position based on the detection of the change of the
actual camshaft phase during the execution of the oil filling
control (the advance chamber oil filling control and the retard
chamber oil filling control), control proceeds to step 103. At step
103, the oil filling control is stopped, and the control duty of
the phase-control hydraulic control valve 25 is changed to 100% (or
to 0%). As a result, the full retard control (or the full advance
control) is executed such that the actual camshaft phase is
maintained at the full retard phase (or the full advance phase).
The full retard control (or the full advance control) is executed
for the certain time period that is shorter than the time period
required for the oil filling control (the advance chamber oil
filling control and the retard chamber oil filling control). The
oil pressure has been increased due to the above operation, and
then the operation is changed to the normal control (the lock
control or the phase feed-back control).
[0061] In contrast, in a case, where the lock pin 58 has been
maintained at the lock position since the start of the cranking,
when it is determined at step 106 that the execution duration of
the retard chamber oil filling control has reached the certain time
period C, the retard chamber oil filling control is ended. Then,
control proceeds to step 108, where it is determined whether the
lock request is issued. When the lock request is issued, control
proceeds to step 109, where the control duty of the phase-control
hydraulic control valve 25 is changed to the certain control duty
such that the lock pin 58 is displaced within the lock hole 59 in
the retard direction or in the advance direction in order to
maintain the lock pin 58 in a state (lock mode), where the lock pin
58 is slightly pressed against the inner peripheral edge of the
lock hole 59. For example, the above certain control duty may be a
control duty apart from the hold duty, which is used for
maintaining the actual camshaft phase, by the predetermined amount
rx in the retard direction or in the advance direction.
[0062] Then, when the lock release request is issued, control
proceeds from step 108 to step 110, where the lock release control
is executed. More specifically, in the lock release control, the
operational position of the lock-control hydraulic control valve 26
is changed from the drain port to the oil pressure supply port such
that oil pressure is supplied to the lock release hydraulic chamber
within the lock pin receiving hole 57 in order to actuate the lock
pin 58 in the lock release direction for the lock release. Then,
control proceeds to step 111, where the operation is changed to the
phase feed-back control. In the above case, even when the lock
release request is issued before completing the oil filling control
(the advance chamber oil filling control and the retard chamber oil
filling control), the lock release is prohibited until the
completion of the oil filling control, and the lock release control
is executed after the completion of the oil filling control.
[0063] In the first embodiment, before the operation is changed
from the lock mode to the phase feed-back control mode after the
engine start, the oil filling control, which supply oil to the
advance chambers 42 and the retard chambers 43 of the variable
valve timing unit 18, is executed. Also, simultaneously, the lock
release of the lock pin 58 is prohibited until the end of the oil
filling control after the engine start such that the lock pin 58 is
maintained at the lock position. Thus, even when the lock release
request is issued before the completion of the oil filling control
or before fulfillment of the advance chambers 42 and the retard
chambers 43 with oil, the execution of the lock release is
prevented, and thereby the wide and unstable variation of the
camshaft phase at the time of the lock release is effectively
prevented.
Second Embodiment
[0064] The above the first embodiment illustrates a configuration
that has the phase-control hydraulic control valve 25 and the
lock-control hydraulic control valve 26, which are independent from
each other. More specifically, the phase-control hydraulic control
valve 25 independently controls oil pressure that actuates the
variable valve timing unit 18, and the lock-control hydraulic
control valve 26 independently controls oil pressure that actuates
the lock pin 58. However, in the second embodiment shown in FIGS. 7
to 11, a hydraulic control valve 71 is singularly employed instead.
More specifically, the hydraulic control valve 71 integrally has
both (a) phase-control hydraulic control valve function for
controlling oil pressure that actuates a variable valve timing unit
70 and (b) lock-control hydraulic control valve function for
controlling oil pressure that actuates the lock pin 58.
[0065] A configuration of the variable valve timing unit 70 of the
second embodiment is substantially similar to a configuration of
the variable valve timing unit 18 of the first embodiment. Thus,
the numerals same with the first embodiment are used in the
description below.
[0066] As above, the hydraulic control valve 71 integrally has the
phase-control hydraulic control valve function and the lock-control
hydraulic control valve function, and is, for example, an
eight-port and four-position spool valve. As shown in FIGS. 8A and
8B, the operation mode of the hydraulic control valve 71 is
categorized in four modes in accordance with the control duty of
the hydraulic control valve 71. For example, the four modes include
a lock mode (slight advance mode), an advance mode, a hold mode,
and a retard mode.
[0067] When the operation mode is in the lock mode (slight advance
mode), a lock pin control port of the hydraulic control valve 71 is
brought into communication with the drain port such that oil
pressure in the lock release hydraulic chamber within the lock pin
receiving hole 57 is released, and thereby the spring 62 urges the
lock pin 58 in the lock direction (projection direction). Also, a
retard port of the hydraulic control valve 71 is brought into
communication with the drain port such that oil pressure in the
retard chambers 43 are released. In the above communication state,
a restrictor in an oil passage connected with an advance port of
the hydraulic control valve 71 is slowly changed in accordance with
the control duty of the hydraulic control valve 71 such that oil is
slowly supplied to the advance chambers 42 through the advance
port. As a result, the actual camshaft phase is gently shifted in
the advance direction.
[0068] When the operation mode is in the advance mode, the retard
port of the hydraulic control valve 71 is brought into
communication with the drain port such that oil pressure in the
retard chamber 43 is released. In the above operation state, oil
pressure supplied to the advance chambers 42 through the advance
port of the hydraulic control valve 71 is changed in accordance
with the control duty of the hydraulic control valve 71. As a
result, the actual camshaft phase is shifted in the advance
direction.
[0069] When the operation mode is in the hold mode, oil pressure in
both the advance chamber 42 and the retard chamber 43 are
maintained such that the actual camshaft phase is prevented from
shifting.
[0070] When the operation mode is in the retard mode, the advance
port of the hydraulic control valve 71 is brought into
communication with the drain port such that oil pressure in the
advance chambers 42 are released. In the above operation state, oil
pressure supplied to the retard chambers 43 through the retard port
of the hydraulic control valve 71 is changed in accordance with the
control duty of the hydraulic control valve 71 such that the actual
camshaft phase is shifted in the retard direction.
[0071] When the operation mode is in the control mode other than
the lock mode (such as the retard mode, the hold mode, the advance
mode), the lock release hydraulic chamber within the lock pin
receiving hole 57 is filled with oil in order to increase oil
pressure in the lock release hydraulic chamber. As a result, the
increased pressure of oil pulls the lock pin 58 out of the lock
hole 59 such that the lock of the lock pin 58 is released. In other
words, the increased oil pressure disengages the lock pin 58 from
the lock hole 59 such that the lock of the camshaft phase by the
lock pin 58 is released.
[0072] It should be noted that in the second embodiment, the
control mode is changed in the order from the lock mode (slight
advance mode), the advance mode, the hold mode, to the retard mode
in accordance of the increase of the control duty of the hydraulic
control valve 71. However, for example, the control mode may be
alternatively changed in the order of the retard mode, the hold
mode, the advance mode, and the lock mode (slight advance mode) in
accordance with the increased of the control duty of the hydraulic
control valve 71 as shown in FIG. 8B. Further alternatively, the
control mode may be changed in the other order of the lock mode
(slight advance mode), the retard mode, the hold mode, and the
advance mode. Also, in a case, where a control range of the lock
mode is directly adjacent to a control range of the retard mode,
the operation of the hydraulic control valve 71 in the control
range for the lock mode (slight retard mode) may be executed as
follows. For example, in the lock mode, oil pressure in the lock
release hydraulic chamber within the lock pin receiving hole 57 is
released, and the spring 62 is caused to urge the lock pin 58 in
the lock direction. Simultaneously, the advance port is brought
into communication with the drain port such that oil pressure is
the advance chamber 42 is released. In the above operation
condition, an operational state of the restrictor of the oil
passage connected with the retard port is slowly changed in
accordance with the control duty of the hydraulic control valve 71
such that oil is slowly supplied to the retard chambers 43 through
the retard port. As a result, the actual camshaft phase is gently
shifted in the retard direction.
[0073] The engine control circuit 21 computes the target phase
(target valve timing) based on the engine operational condition
during the phase feed-back control (variable valve timing control).
Then, the control duty of the hydraulic control valve 71 is
feed-back controlled such that oil pressure supplied to the advance
chamber 42 and the retard chambers 43 of the variable valve timing
unit 70 is feed-back controlled in order to cause the actual
camshaft phase of the intake camshaft 16 (actual valve timing of
the intake valve) to become the target phase (target valve
timing).
[0074] When the lock request is issued during the phase feed-back
control, the phase shift control is executed, in which the
hydraulic control valve 71 is controlled such that the actual
camshaft phase is shifted to go beyond the intermediate lock phase
in the direction (for example, in the retard direction in the
second embodiment) that is opposite from the shift-control
direction during the lock mode to come. Then, the operation mode is
changed to the lock mode, in which the hydraulic control valve 71
is controlled such that the actual camshaft phase is gently shifted
in the direction toward the intermediate lock phase (or in the
advance direction in the second embodiment) while the spring 62 is
caused to urge the lock pin 58 in the lock direction.
[0075] Furthermore, in the second embodiment, the hydraulic control
valve 71 is configured such that phase shift torque in the advance
direction (or in the retard direction) is adjustable in accordance
with the control duty within the control range of the lock mode.
When the operation mode is changed to the lock mode, the spring 62
urges the lock pin 58 in the lock direction and the actual camshaft
phase is gently shifted in the direction toward the intermediate
lock phase. During the above lock mode, the hydraulic control valve
71 is controlled such that the phase shift torque is gradually
increased. When the actual camshaft phase stops around the
intermediate lock phase even with the gradual increase of the phase
shift torque, it is determined that the lock has been
completed.
[0076] Present embodiment employs the hydraulic control valve 71
that integrally includes the phase-control hydraulic control valve
function and the lock-control hydraulic control valve function as
described above. Even in a case, where the actual camshaft phase
accidentally stops at a position different from the intermediate
lock phase due to some reasons (for example, condition, such as oil
temperature) in the present embodiment, the above configuration and
operation of the hydraulic control valve 71 is capable of
effectively preventing the erroneous determination of the
completion of the lock. As a result, the actual camshaft phase is
reliably locked at the intermediate lock phase, and thereby the
determination of the completion of the lock is reliably
achieved.
[0077] The control characteristic of FIGS. 8A and 8B shows that the
lock mode is not prepared for the retard mode, and that the control
range of the lock mode only ranges beside the advance mode. As a
result, it is impossible to supply oil to the retard chamber 43
while the lock pin 58 is maintained at the lock position.
[0078] Thus, in the second embodiment, in a case, where the oil
filling control is executed after the engine start, the control
duty of the hydraulic control valve 71 is changed such that the
advance chamber oil filling control is firstly executed while the
lock pin 58 is maintained at the lock position to keep locking the
actual camshaft phase at the intermediate lock phase. When a first
lock release request after the engine start is issued, the control
duty of the hydraulic control valve 71 is changed such that the
retard chamber oil filling control is subsequently executed until
the actual camshaft phase starts shifting, or until a certain time
period elapses. For example, in the advance chamber oil filling
control, it is possible to supply oil to one of the advance chamber
42 and the retard chamber 43 while the lock pin 58 locks the
camshaft phase. The one of the hydraulic chambers corresponds to
the advance chamber 42 for the case of the control characteristic
of FIGS. 8A and 8B. Also, in the retard chamber oil filling
control, oil is supplied to the other one of the hydraulic
chambers, and the other one corresponds to the retard chamber 43
based on the control characteristic of FIGS. 8A and 8B.
[0079] In the above case, during the execution of the advance
chamber oil filling control, when the unlock of the lock pin 58 is
detected based on the detection of the change of the actual
camshaft phase, oil is supplied to the other one (the retard
chamber 43) of the advance chamber 42 and the retard chamber 43.
Then, operation is changed to the normal control (the lock control
or the phase feed-back control). Due to the above operation, even
when the lock pin 58 is erroneously unlocked (or the lock pin 58 is
erroneously displaced to the unlock position) during the execution
of the oil filling control, the operation is relatively early
changed to the normal control while the wide variation of the
actual camshaft phase is effectively prevented.
[0080] The oil filling control of the second embodiment is executed
by the engine control circuit 21 based on each of routines shown in
FIGS. 9 to 11. Procedure of each of the routines will be described
below.
[Post-Start Oil Filling Control Routine]
[0081] A post-start oil filling control routine of FIG. 9 is
repeatedly executed at certain intervals while the engine control
circuit 21 is on, and functions as oil filling control means. When
the present routine is started, firstly, it is determined at step
201 whether the cranking is being executed or whether a time period
that has elapsed since the start of the cranking is shorter than a
certain time period D. When it is determined that the cranking has
not been started or that the certain time period D has elapsed
since the start of the cranking (since the engine start),
corresponding to NO at step 201, the oil filling control is not
required, and thereby the present routine is ended without
executing the subsequent process.
[0082] In contrast, when it is determined at step 201 that the
cranking is being executed or that the certain time period D has
not elapsed since the engine start, control proceeds to step 202,
where it is determined whether the lock pin 58 is unlocked (the
lock pin 58 is at the unlock position) based on the change of the
actual camshaft phase. When it is determined at step 202 that the
lock pin 58 is at an unlock position (the lock pin 58 does not lock
the camshaft phase), control proceeds to step 203, where a
unlocked-time oil filling control routine of FIG. 11 (described
later) is executed.
[0083] When it is determined at step 202 that the lock pin 58 is
not at the unlock position (or that the actual camshaft phase
stably stays around the intermediate lock phase), control proceeds
to step 204, where the control duty of the hydraulic control valve
71 is set at a control duty E (see FIG. 8B), at which advance
torque is maximized while the control duty is within a control
range for the lock mode for maintaining the lock pin 58 at the lock
position. For example, when the advance torque is maximized, an oil
filling rate for supplying oil to the advance chamber 42 is
maximized. As above, the advance chamber oil filling control for
supplying oil to the advance chamber 42 is executed. In the present
embodiment, it is possible to supply oil to the advance chamber 42
while the lock pin 58 is maintained at the lock position for
locking the actual camshaft phase.
[0084] Then, control proceeds to step 205, where it is determined
whether the actual camshaft phase stably stays around the
intermediate lock phase. When it is determined that the actual
camshaft phase does not stably stay around the intermediate lock
phase, control proceeds to step 206, where the unlock of the lock
pin 58 is determined (or it is determined that the lock pin 58 is
at the unlock position). Thus, control proceeds to step 203, where
the unlocked-time oil filling control routine of FIG. 11 is
executed.
[0085] In contrast, when it is determined at step 205 that the
actual camshaft phase stably stays around the intermediate lock
phase, control proceeds to step 207, where the execution duration
of the lock mode (post-start oil filling control) exceeds a certain
time period F. When it is determined that the execution duration of
the lock mode has not exceeded the certain time period F, the
present routine is ended.
[0086] Then, when the execution duration of the lock mode exceeds
the certain time period F, it is determined that supply of oil to
the advance chamber 42 has been completed, and control proceeds to
step 208, where the control duty of the hydraulic control valve 71
is set at a control duty of 0% within the control range for the
lock mode in order to stop the supply of oil to the advance chamber
42. Then, the advance chamber oil filling control is ended, and
control proceeds to step 209, where an advance chamber oil filling
control completion flag is set at "ON" indicating the completion of
the advance chamber oil filling control.
[Lock-Release-Request-Time Oil Filling Control Routine]
[0087] The lock-release-request-time oil filling control routine of
FIG. 10 is repeatedly executed at certain intervals while the
engine control circuit 21 is on, and functions as oil filling
control means. When the present routine is started, firstly, it is
determined at step 301 whether the advance chamber oil filling
control completion flag is ON indicating that the advance chamber
oil filling control is completed. When the advance chamber oil
filling control completion flag is OFF indicating that the advance
chamber oil filling control has not been completed yet, process is
ended without executing the subsequent process. Thus, even when the
lock release request is issued before the advance chamber oil
filling control is completed, the execution of the lock release is
prevented.
[0088] In contrast, when it is determined at step 301 that the
advance chamber oil filling control completion flag is ON
indicating that the advance chamber oil filling control has been
completed, control proceeds to step 302, where it is determined
whether a first lock release request after the engine start is
issued. When the first lock release request after the engine start
is not issued, the present routine is ended without executing the
subsequent process.
[0089] Then, when the first lock release request after the engine
start is issued, control proceeds to step 303, where the control
duty of the hydraulic control valve 71 is set at the control duty
of 100% in order to execute the retard chamber oil filling control
for supplying oil to the retard chamber 43. For example, when the
control duty of the hydraulic control valve 71 is set at the
control duty of 100%, the oil filling rate for supplying oil to the
retard chamber 43, which has not yet been sufficiently filled with
oil, is maximized.
[0090] Then, control proceeds to step 304, where a retard chamber
oil filling duration counter is incremented, and a retard chamber
oil filling duration (or duration time of the control duty 0%) is
measured. Then, control proceeds to step 305, where it is
determined whether the actual camshaft phase starts shifting. When
it is determined that the actual camshaft phase has not started
shifting, control proceeds to step 307, where it is determined
whether a count value of the retard chamber oil filling duration
counter exceeds a predetermined value (or whether a duration for
executing the retard chamber oil filling control exceeds a certain
time period). When it is determined that the count value of the
retard chamber oil filling duration counter is equal to or smaller
than the predetermined value, the present routine is ended. Thus,
when the first lock release request after the engine start is
issued after the execution of the advance chamber oil filling
control, the retard chamber oil filling control is executed until
the actual camshaft phase starts shifting or until the certain time
period has elapsed.
[0091] When the actual camshaft phase does not start shifting, and
also the retard chamber oil filling duration exceeds the certain
time period, the retard chamber oil filling control is ended. Then,
control proceeds to step 308, where the lock release control is
executed to release the lock of the lock pin 58. The above lock
release control may be executed while the target phase of the
actual camshaft phase is set around the intermediate lock phase
such that the lock pin 58 is limited from being firmly pressed
against the inner peripheral edge of the lock hole 59. As a result,
frictional force generated while the lock pin 58 is being pulled
out of the lock hole 59 during the lock release control is reduced.
As above, the lock release control is executed while the control
duty of the hydraulic control valve 71 is held within the control
range for the hold mode. After the execution of the lock release
control, control proceeds to step 309, where the phase feed-back
control is executed such that the control duty of the hydraulic
control valve 71 is feed-back controlled in order to make the
actual camshaft phase become the target phase. As a result, oil
pressure of the variable valve timing unit 70 supplied to the
advance chamber 42 and the retard chamber 43 is feed-back
controlled accordingly.
[0092] in contrast, when the actual camshaft phase starts moving
before the retard chamber oil filling duration reaches the certain
time period, it is determined that the lock release has been
already made. Thus, control proceeds to step 306, where the phase
feed-back control is executed.
[Unlocked-Time Oil Filling Control Routine]
[0093] The unlocked-time oil filling control routine of FIG. 11 is
a subroutine executed at step 203 of the post-start oil filling
control routine of FIG. 9 when the unlock of the lock pin 58 is
detected (or when it is detected that the lock pin 58 does not lock
the camshaft phase) at step 202 while the cranking is being
executed or before the certain time period D has elapsed since the
engine start (step 201).
[0094] When the present routine is started, firstly at step 401,
the control duty of the hydraulic control valve 71 is set at the
control duty of 100%, at which the oil filling rate for the retard
chamber 43 is maximized and the retard chamber oil filling control
for supplying oil to the retard chamber 43 is executed. Then,
control proceeds to step 402, where it is determined whether the
engine is idling. When it is determined that the engine is idling,
control proceeds to step 403, where the target idling rotational
speed is increased such that the engine rotation speed is increased
accordingly. Thus, the rotational speed of the oil pump 28 that
pumps oil is increased, and thereby the oil filling rate for
supplying oil to the retard chamber 43 is increased. As a result,
oil pressure in the retard chamber 43 is quickly increased.
[0095] When it is determined at step 402 that the engine is not
idling, the increase of the target idling rotational speed at step
403 is not executed.
[0096] Then, control proceeds to step 404, where it is determined
whether the retard chamber oil filling duration (or the duration
time of the control duty 100%) exceeds a certain time period G.
When it is determined that the retard chamber oil filling duration
has not exceeded the certain time period G, the present routine is
ended.
[0097] When the retard chamber oil filling duration exceeds the
certain time period G, it is determined that the supply (filling)
of oil to the retard chamber 43 has been completed. Thus, control
proceeds to step 405, where the operation is changed to the normal
control (the lock control or the phase feed-back control).
[0098] In the second embodiment, the variable valve timing control
apparatus employs the hydraulic control valve 71 that integrally
has (a) the phase-control hydraulic control valve function for
controlling oil pressure that actuates the variable valve timing
unit 70 and (b) the lock-control hydraulic control valve function
for controlling oil pressure that actuates the lock pin 58. When
the oil filling control is executed after the engine start, the
control duty of the hydraulic control valve 71 is changed such that
the advance chamber oil filling control is executed firstly, and
such that when the first lock release request after the engine
start is issued after the execution of the advance chamber oil
filling control, the retard chamber oil filling control is
subsequently executed until the actual camshaft phase starts
shifting or until the certain time period elapses. For example, in
the advance chamber oil filling control, oil is supplied to one of
the advance chamber 42 and the retard chamber 43, and it is
possible to supply oil to the one of the chambers 42, 43 while the
lock pin 58 is kept at the lock position. In accordance with the
control characteristic of FIGS. 8A and 8B, the one of the chambers
42, 43 corresponds to the advance chamber 42. In contrast, in the
retard chamber oil filling control, oil is supplied to the other
one of the chambers, and the other one of the chambers corresponds
to the retard chamber 43 based on the control characteristic of
FIGS. 8A and 8B. As a result, even in a case for employing the
hydraulic control valve 71 that integrally has the phase-control
hydraulic control valve function and the lock-control hydraulic
control valve function, the unstable wide variation of the camshaft
phase at the time of the lock release after the engine start is
effectively prevented.
[0099] Furthermore, in the second embodiment, when the unlock of
the lock pin 58 is detected based on the detection of the change of
the actual camshaft phase during the execution of the oil filling
control to the advance chamber 42, firstly, oil is supplied to the
retard chamber 43. Then, the operation is changed to the normal
control (the lock control or the phase feed-back control). As a
result, even when the lock pin 58 is unlocked during the execution
of the oil filling control to the advance chamber 42, it is
possible to relatively early change the operation to the normal
control while the unstable wide variation of the actual camshaft
phase is effectively prevented.
[0100] It should be noted that the present invention is not limited
to the variable valve timing control apparatus for the intake
valve. However, the present invention may be applied to a variable
valve timing control apparatus for an exhaust valve.
[0101] A configuration of the variable valve timing unit 18, 70 and
a configuration of the hydraulic control valves 25, 26, 71 may be
modified as required provided that the modification does not
deviate from the gist of the invention.
[0102] Additional advantages and modifications will readily occur
to those skilled in the art. The invention in its broader terms is
therefore not limited to the specific details, representative
apparatus, and illustrative examples shown and described.
* * * * *