Information
-
Patent Grant
-
6330869
-
Patent Number
6,330,869
-
Date Filed
Monday, May 8, 200024 years ago
-
Date Issued
Tuesday, December 18, 200122 years ago
-
Inventors
-
Original Assignees
-
Examiners
Agents
- Arent Fox Kintner Plotkin & Kahn, PLLC
-
CPC
-
US Classifications
Field of Search
US
- 123 9015
- 123 9016
- 123 9017
- 123 9018
- 123 9019
- 123 9031
-
International Classifications
- F02D1302
- F01L1300
- F01L134
-
Abstract
A controller for an internal combustion engine has a hydraulic valve characteristic changing mechanism for changing valve operating characteristics of suction and exhaust valves; a valve system provided with a hydraulic valve phase variable mechanism that changes the phase; a map that stores a fuel injection quantity and an ignition timing in response to the valve operating characteristics; and delay time setting means for setting a delay time required to complete changeover of the valve operating characteristics, based on operating oil properties detected from behavior of a valve phase variable mechanism, to change the map after the delay time has elapsed. Thus, a valve operating characteristic changing timing coincides with a map changing timing to thereby achieve an improved performance of the internal combustion engine.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a control device of an internal combustion engine which is provided with a valve moving apparatus having a hydraulic valve characteristic changing mechanism for changing valve operation characteristic such as lift of a suction valve or an exhaust valve and a hydraulic valve phase variable mechanism for altering phase of the suction valve or the exhaust valve. According to the control device, when the valve operation characteristic is changed, a map storing control amounts for controlling combustion condition of the engine such as amount of injected fuel is changed at a timing reflecting property of a working oil such as viscosity of the working oil supplied to the valve characteristic changing mechanism.
An internal combustion engine provided with a valve moving apparatus having a hydraulic valve characteristic changing mechanism for changing valve operation characteristic by driving a suction valve and an exhaust valve with a cam for low speed of small lift and small valve opening time on a low rotational speed of the engine and with a cam for high speed of large lift and large valve opening time on a high rotational speed of the engine has been known (Japanese Patent Publication No. 2619696).
The above valve characteristic changing mechanism has connecting pins provided on respective rocker arms of the suction valve and the exhaust valve, and an oil pressure changing valve. The connecting pins are moved by pressure of oil which is changed over by the oil pressure changing valve, to connect or disconnect the rocker arms, so that the rocker arms, therefore the suction valve and the exhaust valve, are driven by the cam for low speed or the cam for high speed.
When the valve operation characteristic is changed, a map of fuel injection amount and a map of ignition time are changed into maps for low speed or maps for high speed corresponding to the valve operation characteristic, to carry out fuel injection amount control and ignition time control. In that case, a delay time required for changing actions of the valve characteristic changing mechanism of all cylinders to be completed by the oil pressure changed by the oil pressure changing valve is previously set in a timer, and change of the maps is carried out after the delay time elapses for the fuel injection amount control and the ignition time control adapted to the valve operation characteristic.
However, in the above-mentioned prior art, as the delay time to be set in the timer, a fixed value decided from a viewpoint of prevention of engine stall and prevention of deterioration of drive ability is adopted, so that the delay time does not correspond to change of property of the working oil of the valve characteristic changing mechanism. Therefore, sometimes, notwithstanding that actually valve characteristic changing mechanisms of all cylinders have been already changed into high speed side (or low speed side), maps for fuel injection amount ad ignition time remain in maps for low speed (or for high speed), because the oil property (oil viscosity susceptible to temperature, for example) is altered influenced by operational condition of the engine to alter operation response of the valve characteristic changing mechanism. And, in a short period when a suction air amount, a fuel injection amount and an ignition time are not adapted to each other due to a time lag between a valve operation characteristic changing time point and a map changing time point, air-fuel ratio or ignition time deviates from an optimum value to produce undesirable results regarding engine performance other than the prevention of engine stall and the prevention of deterioration of drive ability, especially regarding exhaust emission.
SUMMARY OF THE INVENTION
The present invention has been accomplished in view of the foregoing, and a subject of the invention is to further improve performance of the internal combustion engine by that property of the working oil in the hydraulic valve characteristic changing mechanism of the valve moving apparatus is detected, and the delay time deciding a change timing of a control amount holding means which folds control amounts for controlling combustion condition of the internal combustion engine is altered in accordance with the detected property of the working oil, to make a change of the valve operation characteristic coincide with the change of the control amount holding means.
The present invention provides a control device of an internal combustion engine, comprising an operational condition detecting means for detecting an operational condition of the internal combustion engine; a valve moving apparatus provided with a first valve control mechanism having a hydraulic valve characteristic changing mechanism for changing valve operation characteristic of at least one of a suction valve and a exhaust valve of said engine, and an oil pressure changing valve for changing pressure of a working oil supplied to said valve characteristic changing mechanism from an oil pressure source; a first valve operation control means for controlling operation of said oil pressure changing valve in accordance with the operational condition detected by said operational condition detecting means; control amount holding means corresponding to said respective valve operation characteristic which hold control amounts to control combustion condition of said engine; a combustion control means operated based on said control amount of said control amount holding means; a working oil pressure detecting means for detecting property of said working oil; a delay time setting means for setting a delay time between change of oil pressure by said oil pressure changing valve and completion of change of valve operation characteristic by said valve characteristic changing mechanism based on property of said working oil detected by said working oil property detecting means; and changing means for changing said control amount holding means to a control amount holding means corresponding to a changed valve operation characteristic when said delay time elapses after said oil pressure to be supplies to said valve characteristic changing mechanism is changed by said oil pressure changing valve.
According to this invention, after the delay time set based on property of the working oil of the valve characteristic changing mechanism elapses, the changing means changes the control amount holding means from a control amount holding means corresponding to a valve operation characteristic before the valve moving mechanism is changed to a control amount holding means corresponding to a valve operation characteristic after the valve moving mechanism is changed. And the combustion control means controls combustion of the engine based on a control amount held in the changed control amount holding means. Since the delay time can be set in accordance with change of property of the working oil which is influenced by operational condition of the engine, in a wide operation range of the engine, change timing of the valve operation characteristic and change timing of the control amount holding means can be made coincide with each other to control combustion of the engine with a control amount most suitable for the valve operation characteristic, so that performance of the engine can be more improved.
The said valve moving apparatus may further comprise a hydraulic valve phase variable mechanism for altering phase of open-close period of at least one of said suction valve and said exhaust valve, and a second valve control mechanism having an oil pressure control valve for controlling pressure of a working oil supplied to said valve phase variable mechanism from said oil pressure source. Further, operation of said oil control valve may be controlled by a second valve operation control means in accordance with the operational condition detected by said operational condition detecting means, and said working oil property detecting means may detect property of said working oil based on behavior of said second valve control mechanism.
According to this invention, the working oil property detecting means can detect working oil property in the valve characteristic changing mechanism based on behaviors of the valve phase variable mechanism operated by oil pressure and the second valve control mechanism having the oil pressure control valve. As the result, a detecting means for directly detecting property of the working oil, for example, a temperature sensor for the working oil is unnecessary and the cost is reduced. As factors exerting influence on property of the working oil, there are kind of the working oil, secular change of the working oil or the like in addition to factors based on operational condition of the engine (temperature of working oil, for example). Since the property of the working oil detected according to this invention includes all of the factors, more accurate working oil property can be detected, and therefore more accurate change timing of the control amount holding means can be set, compared with a case that the working oil property is detected only by the oil temperature sensor for example.
Phase detecting means for detecting phase of at least one of said suction valve and said exhaust valve having phase altered, and phase change speed calculating means for calculating changing speed of phase detected by said phase detecting means may be provided, and said working oil property detecting means may detect said working oil property based on said changing speed of phase.
According to this invention, property of the working oil can be detected from behavior of the valve phase variable mechanism which reflects property of the working oil. Further, since detection of the working oil property is possible even when the phase is altered largely or continuously, the working oil property can be detected one by one in a wide engine operation region.
Phase detecting means for detecting phase of at least one of said suction valve and said exhaust valve having phase altered, and target phase setting means for setting a target phase based on the operational condition detected by said operational condition detecting means may be provided, said second valve operation control means may control operation of said oil pressure control valve so that said target phase concurs with said phase detected by said phase detecting means, and said working oil property detecting means may detect working oil property based on deviation between said target phase and said phase detected by said phase detecting means.
According to this invention, property of the working oil can be detected from behavior of the valve phase variable mechanism which reflects property of the working oil. Further, since the deviation between the target phase and the actual phase is a datum obtainable in course of controlling the valve phase variable mechanism to the target phase, no particular apparatus is necessary for obtaining the deviation to detect the working oil property.
Said oil pressure control valve may be operated in accordance with an amount of supply electric current which is duty-controlled by said second valve operation control means, and said working oil property detecting means may detect working oil property based on duty ratio of said amount of supply electric current when said valve phase variable mechanism maintains a fixed phase by oil pressure controlled by said oil pressure control valve.
According to this invention, by utilizing duty ratio of the amount of electric current supplied to the oil pressure control valve for controlling pressure of the working oil supplied to the valve phase variable mechanism, even in an engine operation region where phase of the suction valve or the exhaust valve is not altered by the valve phase variable mechanism, the working oil property can be detected and the delay time can be set based thereon.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
is a whole view of an internal combustion engine applied the present invention;
FIG. 2
is a partial view of
FIG. 1
viewed in the direction of the arrow II;
FIG. 3
is a sectional view taken along the line III—III of
FIG. 2
;
FIG. 4
is a sectional view taken along the line IV—IV of
FIG. 3
;
FIG. 5
is a sectional view taken along the line V—V of
FIG. 3
;
FIG. 6
is a sectional view taken along the line VI—VI of
FIG. 2
;
FIG. 7
is an oil pressure circuit diagram of the valve characteristic changing mechanism and the valve phase variable mechanism;
FIG. 8
is a sectional view of an oil pressure corresponding valve;
FIG. 9
is a sectional view of a linear solenoid valve;
FIG. 10
is a flow chart showing a routine for changing valve operation characteristic and map by the valve characteristic changing mechanism at a low rotational speed and a middle rotational speed;
FIG. 11
is a flow chart showing a routine for changing valve operation characteristic and map by the valve characteristic changing mechanism at a middle rotational speed and a high rotational speed;
FIG. 12
is a flow chart showing a routine for calculating target cam phases;
FIG. 13
is a flow chart showing a feedback control routine of the valve phase variable mechanism;
FIG. 14
is a flow chart showing a routine for setting delay times;
FIG. 15
is a flow chart showing another routine for setting delay times;
FIG. 16
is a map showing a relation between the delay time and variation of the actual cam phase;
FIG. 17
is a map showing a relation between the delay time and duty ratio of the electric current to the linear solenoid valve which is in a neutral position; and
FIG. 18
is a map showing a relation between the delay time and deviation of the actual cam phase from the target cam phase.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENT OF THE INVENTION
Hereinafter, a preferred embodiment of the present invention will be described with reference to
FIGS. 1
to
18
.
In the embodiment shown in
FIGS. 1-14
,
16
and
17
, the internal combustion engine
1
is a spark-ignition, 4 cylinder, DOHC 4 valve internal combustion engine to be mounted on a vehicle and has pistons
2
connected to a crankshaft
4
via connecting rods
3
. As shown in
FIG. 1
, a drive sprocket
5
provided on one end of the crankshaft
4
, a suction cam sprocket
8
provided on one end of a suction cam shaft
6
and an exhaust cam sprocket
9
provided on one end of an exhaust cam shaft
7
are connected by a timing chain
10
so that the cam shafts
6
,
7
rotate once while the crankshaft
4
rotates twice.
Each cylinder has two suction valve
11
driven by the suction cam shaft
6
and two exhaust valves
12
driven by the exhaust cam shaft
7
. Between the suction cam shaft
6
and the suction valve
11
and between the exhaust cam shaft
7
and the exhaust valve
12
are provided respective valve characteristic changing mechanisms
13
which change valve operation characteristics (lift and opening period, for example) of the valves
11
,
12
in three modes. At the end of the suction cam shaft provided with the cam sprocket
8
is provided a valve phase variable mechanism
50
which advances or retards opening-closing period of the suction valve
11
continuously to alter cam phase.
Both the valve characteristic changing mechanisms
13
for the suction valve
11
and the exhaust valve
12
are of the same construction. Therefore, the valve characteristic changing mechanism
13
for the suction valve
11
will be described hereinafter referring to
FIGS. 2
to
5
.
For every cylinder, the suction valve
11
is integrally provided with a cam for low speed
15
, a cam for high speed
16
and an upheaved portion
17
which are arranged in this order. Under the suction cam shaft
6
is fixed a rocker shaft
18
in parallel with the cam shaft
6
, and a first rocker arm
19
, a second rocker arm
20
and a third rocker arm
21
, corresponding to the cam for low speed
15
, the cam for high speed
16
and the upheaved portion
17
respectively, are supported on the rocker shaft
18
so as to rock.
As shown in
FIG. 3
, the cam for low speed
15
has a nose part which projects radially of the suction cam shaft
6
with a relatively small projection and extends over a relatively small circumferential range, and a base circle part. The cam for high speed
16
has a nose part with a larger projection and a larger circumferential length compared with the cam for low speed
15
, and a base circle part. The upheaved portion
17
has a projecting part slightly projecting radially of the suction cam shaft
6
and a base circle part. The projecting part of the upheaved portion
17
is considerably lower than the nose part of the cam for low speed
15
.
A flange
23
is provided on an upper end of a valve stem
22
of the suction valve
11
. The suction valve
11
is forced to close by a valve spring
25
inserted between a cylinder head
24
and the flange
23
in a compressed state. Each of the first and third rocker arms
19
,
21
supported by the rocker shaft
18
so as to rock has an end adjustably provided with a tappet screw
26
which touches to an upper end of the valve stem
22
of the suction valve
11
.
The first, second and third rocker arms
19
,
20
,
21
have respective first, second and third rollers
27
,
28
,
29
at a position between the rocker arm
18
and the suction valve
11
. The rocker arms
19
,
20
,
21
rock guided by the cams
15
,
16
and the upheaved portion
17
through the rollers
27
,
28
,
29
, respectively. The second rocker arm
20
is forced by a spring means (not shown) so that the second roller
28
touches to the cam for high speed
16
.
As shown in
FIG. 5
, the first roller
27
has an axis parallel with the rocker shaft
18
and comprises an inner ring
27
a
fixedly fitted to the first rocker arm
19
, an outer ring
27
b
slidingly contacted with the cam for low speed
15
, and a plurality of needle rollers provided between the inner ring
27
a
and the outer ring
27
b.
Similarly, the second roller
28
has an axis parallel with the rocker shaft
18
and comprises an inner ring
28
a
fixedly fitted to the second rocker arm
20
, an outer ring
28
b
slidingly contacted with the cam for high speed
16
, and a plurality of needle rollers
28
c
provided between the inner ring
28
a
and the outer ring
28
b.
The third roller
29
has an axis parallel with the rocker shaft
18
and comprises an inner ring
29
a
fixedly fitted to the third rocker arm
21
, an outer ring
29
b
slidingly contacted with the upheaved portion
17
, and a plurality of needle rollers
29
c
provided between the inner ring
29
a
and the outer ring
29
b.
When the rocker arms
19
,
20
,
21
are stationary, the inner rings
27
a,
28
a,
29
a
are fixed so as to align with each other.
As shown in
FIGS. 3
to
5
, the first and third rocker arms
19
,
21
are provided with a first connection changing mechanism
30
capable of connecting and disconnecting the rocker arms
19
,
21
, and the first, second and third rocker arms
19
,
20
,
21
are provided with a second connection changing mechanism
31
capable of connecting and disconnecting these rocker arms
19
,
20
,
21
.
Namely, the first and third rocker arms
19
.
21
have respective connecting arms
19
a,
21
a
formed integrally on a side opposite to the rocker shaft
18
. The connecting arms
19
a,
21
a
are opposite to each other striding across the second rocker arm
20
and between the connecting arms
19
a,
21
a
is provided the first connection changing mechanism
30
which comprises a connecting piston
32
capable of connecting the connecting arms
19
a,
21
a,
a regulating member
33
for regulating movement of the connecting piston
32
, and a return spring
34
for forcing the connecting piston
32
and the regulating member
33
to the disconnecting side. The connecting arms
19
a,
21
a
have guide holes
35
,
36
which are opposite to each other and extend parallel with the rocker shaft
18
.
The connecting piston
32
is fitted to the guide hole
35
slidingly, and between the connecting piston
32
and a closed end of the guide hole
35
is formed a first oil pressure chamber
37
. The first rocker arm
18
is provided with a communication passage
38
communicating with the first oil pressure chamber
37
and within the rocker shaft
18
is formed a first oil pressure supply passage
39
communicating with an oil pump
70
. The first oil pressure supply passage
39
always communicates with the first oil pressure chamber
37
through the communication passage
38
regardless of rocking state of the first rocker arm
19
.
On the one hand, the second connection changing mechanism
31
comprises a connecting piston
41
capable of connecting the first and second rocker arms
19
,
20
, a connecting pin
42
capable of connecting the second and third rocker arms
20
,
21
, a regulating member
43
for regulating movements of the connecting piston
41
and the connecting pin
42
, and a return spring for forcing the connecting piston
41
, the connecting pin
42
and the regulating member
43
to the disconnecting side.
The connecting piston
41
is slidingly fitted to the inner ring
27
a
of the first roller
27
and between one end of the connecting piston
41
and the first rocker arm
19
is formed a second oil pressure chamber
45
. The first rocker arm
19
has a communication passage
46
communicating with second oil pressure chamber
45
. Within the rocker shaft
18
is formed a second oil pressure supply passage
47
communicating with the oil pump
70
. The second oil pressure supply passage
47
is isolated from the first oil pressure supply passage
39
of the first connection changing mechanism
30
. The second oil pressure supply passage
47
always communicates with the second oil pressure chamber
45
through the communication passage
46
regardless of rocking state of the first rocker arm
19
.
The connecting pin
42
having an end touching another end of the connecting pin
41
is slidingly fitted to the inner ring of the second roller
28
. The bottomed-cylinder-like regulating member
43
touching another end of the connecting pin
42
is slidingly fitted to the inner ring
29
a
of the third roller
29
. The return spring
44
is inserted between the third rocker arm
21
and the regulating member
43
in a compressed state.
In the first connection changing mechanism
30
, when pressure of the working oil supplied to the first oil pressure chamber
37
is lowered, the connecting piston
32
and the regulating member
33
is moved by the return spring
34
to the disconnecting side. In this state, the contacting surface of the connecting piston
32
and the regulating member
33
positions between the first rocker arm
19
and the third rocker arm
21
, and the first and third rocker arms are disconnected. When the working oil of high pressure is supplied to the first oil pressure chamber
37
, the connecting piston
32
moves against the return spring
34
to the connecting side and goes into the guide hole
26
so that the first and third rocker arms
19
,
21
are integrally connected.
In the second connection changing mechanism
31
, when pressure of the working oil supplied to the second oil pressure chamber
45
is lowered, the connecting piston
41
, the connecting pin
43
and the regulating member
43
are moved by the return spring
44
to the disconnecting side. In this state, the contacting surface of the connecting piston
41
and the connecting pin
42
positions between the first rocker arm
19
and the second rocker arm
20
, the contacting surface of the connecting pin
42
and the regulating member
43
positions between the second rocker arm
20
and the third rocker arm
21
, and the first, second and third rocker arms
19
,
20
,
21
is in a disconnected state. When the working oil of high pressure is supplied to the second oil pressure chamber
45
, the connecting piston
41
, the connecting pin
42
and the regulating member
43
move against the return spring
44
to the connecting to the connecting side, and the connecting pistons
41
,
42
go into the inner rings
28
a,
29
a
so that the first, second and third rocker arms
19
,
20
21
are integrally connected.
Next, the valve phase variable mechanism
50
provided at an end of the suction cam shaft
6
will be described with reference to
FIGS. 2 and 6
.
A supporting hole
51
a
formed at a center of a cylindrical boss member
51
is coaxially fitted and connected by a pin
52
and a bolt
53
to an end portion of the suction cam shaft
6
so as not to rotate relatively. The cam sprocket
8
which the timing chain
10
is wound round is formed in a cup-shape having a circular hollow
8
a
and on its outer periphery is formed sprocket teeth
8
b.
An annular housing
54
fitted to the hollow
8
a
of the cam sprocket and a plate
55
laid on an axial end of the housing
54
are connected to the cam sprocket
8
by four bolts
56
penetrating them.
Therefore, the boss member
51
integrally connected to the suction cam shaft
6
is housed in a space surrounded by the cam sprocket
8
, the housing
54
and the plate
55
so as to rotate. A lock pin
57
is slidingly fitted to a pin hole axially penetrating the boss member
51
. The lock pin
57
is forced by a compressed spring
58
inserted between the lock pin
57
and the plate
55
so as to engage with a lock hole
8
c
formed in the cam sprocket
8
.
Within the housing
54
are formed four fan-shaped hollows
54
a
arranged about axis of the suction cam shaft
6
at intervals of 90 degrees. Four vanes
51
b
radially projecting from an outer periphery of the boss member
51
are fitted into the hollows
54
a
so as to rotate in an angular range of 30 degrees. Seal members
59
provided at tip ends of the vanes
51
b
slidingly touch top walls of the hollows
54
b
and seal members
60
provided on an inner peripheral surface of the housing
54
slidingly touch an outer peripheral surface of the boss member
51
, so that an advance chamber
61
and a retard chamber
62
are partitioned on both sides of the each vane
51
b.
Within the suction cam shaft
6
are formed an oil passage for advance
63
and an oil passage for retard
64
. The oil passage for advance
63
communicates with the four advance chambers
61
through four oil passages
65
radially penetrating the boss member
51
, and the oil passage for retard
64
communicates with the four retard chambers
62
through four oil passages
66
radially penetrating the boss member
51
. The lock hole
8
c
of the cam sprocket
8
engaging with the lock pin
57
communicates with any one of the advance chamber
61
through an oil passage (not shown).
When the working oil is not supplied to the advance chamber
61
, a head part of the lock pin
57
is fitted into the lock hole
8
c
of the cam sprocket
8
by force of the spring
58
and the cam shaft
6
is locked to the cam sprocket
8
in a most retarded state that the cam shaft
6
is extremely rotated anticlockwise relatively to the cam sprocket
8
as shown in FIG.
6
. When pressure of the working oil supplied to the advance chamber
61
is raised from the above state, the lock pin
57
leave the lock hole
8
c
of the cam sprocket
8
against the force of the spring
58
by the pressure of the working oil supplied from the advance chamber
61
, the vane
51
b
is rotated clockwise relatively to the cam sprocket
8
by pressure difference between the advance chamber
61
and the retard chamber
62
, and phases of the cam for low speed
15
and the cam for high speed
16
are advanced all at once to alter the valve opening period and the valve closing period of the suction valve
11
toward advance side. Therefore, the opening-closing period of the suction valve
11
can be altered continuously by controlling oil pressure in the advance chamber
61
and the retard chamber
62
.
An oil pressure control system for the valve characteristic changing mechanism
13
and the valve phase variable mechanism
50
will be described with reference to FIG.
7
.
Oil pumped up by the oil pump to, which is the oil pressure source, from an oil pan
71
at a bottom of the crankcase is discharged into an oil passage
72
as lubricating oils of the crankshaft
4
and the valve moving mechanism of the engine
1
and as working oils of the valve characteristic changing mechanism
13
and the valve phase variable mechanism
50
. In two oil passages
73
,
74
branching from the oil passage
72
to communicate with the valve characteristic changing mechanism
13
of suction valve
11
side, a first oil pressure responsive valve
80
and a second oil pressure responsive valve
81
ae provided, respectively. The oil pressure responsive valves
80
,
81
are examples of oil pressure changing valves for changing oil pressure of the oil pressure supply passages
39
,
47
in the rocker shaft
8
into high or low. Though it is not shown, similar oil pressure changing valves are provided in oil passages communicating with the valve characteristic changing mechanism
13
of the exhaust valve
12
side, too. The valve characteristic changing mechanism
13
and the oil pressure changing valve constitute respective valve control mechanisms of the suction valve
11
side and the exhaust valve
12
side. In an oil passage
75
branching from the oil passage
72
to communicate with the valve phase variable mechanism
50
is provided a linear solenoid valve
90
which is an example of the oil pressure control valve for controlling pressures in the advance chamber
61
and the retard chamber
62
continuously. The valve phase variable mechanism
50
and the oil pressure control valve constitute a valve control mechanism other than the above-mentioned valve control mechanism.
A signal from a suction cam shaft sensor
67
(
FIG. 1
) detecting rotational position θI of the suction cam shaft
6
, a signal from a TDC sensor detecting top dead center θTD of the piston based on a exhaust cam shaft sensor
68
(
FIG. 1
) which detects rotational position of the exhaust cam shaft
7
, a signal of a crankshaft sensor
69
(
FIG. 1
) detecting rotational position θC of the crankshaft
4
, a signal from a suction negative pressure sensor detecting suction negative pressure P, a signal from a cooling water temperature sensor detecting cooling water temperature TW, a signal from a throttle opening degree sensor detecting throttle opening degree θTH, and a signal from a rotational speed sensor detecting rotational speed Ne of the engine
1
are inputted in a electronic control unit
76
which is an example of control means. The electronic control unit
76
includes valve operation control means for controlling operations of the valve phase variable mechanism
50
and oil pressure responsive valves
80
,
81
, and valve operation control means for controlling operation of the linear solenoid valve
90
. The above sensors constitute operational condition detecting means for detecting operational condition of the engine.
In a memory provided in the electronic control unit
76
are stored maps of fuel supply amount, ignition period and target cam phase having suction negative pressure and engine rotational speed as parameters. As for the fuel supply amount map (fuel injection amount map, for example) and the ignition period map, maps for low speed, middle speed and high speed are prepared corresponding to valve operation characteristics on low speed, middle speed and high speed. The fuel supply amount and the ignition period ae control amounts for controlling combustion condition of the engine
1
and the maps of the fuel supply amount and the ignition period stored In the memory of the electronic control unit
96
are examples of control amount holding means. A fuel supply apparatus for supplying fuel to the cylinder of the engine such as a fuel injection valve and an ignition period control apparatus are examples of combustion control means and these apparatus are operated based on control amounts stored in the maps.
Referring to
FIG. 8
, the first oil pressure responsive valve
80
comprises a housing
82
, a spool
83
slidingly fitted in the housing
82
, a spring
84
forcing the spool
83
in a direction to close the valve, and a first solenoid valve
85
of normally closed type operated by instructions from the valve operation control means of the electronic control unit
76
. The spool
83
is moved to an open position against force of the spring
84
by pilot pressure inputted through a pilot oil passage
86
branched from a inlet port
82
a
formed in the housing
82
. The pilot oil passage
86
is opened and closed by the first solenoid valve
85
, and when the first solenoid valve
85
is opened, the spool
83
moves to the open position.
The housing
82
is formed with an inlet port
82
a
communicating with the oil passage
73
through an oil filter
87
, an outlet port
82
b
communicating with the first oil pressure supply passage
39
, an orifice
82
c
communicating with the inlet port
82
a
and the outlet port
82
b,
and a drain port
82
d
communicating with the outlet port
82
b
and opening to an upper space of the cylinder head
24
. The spool
83
has a groove
83
b
between a pair of lands
83
a.
When the spool
83
is in the close position, the outlet port
82
b
communicates with the inlet port
82
a
through only the orifice
82
c
and also communicates with the drain port
82
d,
so that pressure of the work oil in the first oil pressure supply passage
39
becomes low. When the spool
83
is in the open position, the outlet port
82
b
communicates with the inlet port
82
a
through the groove
83
b
and is disconnected from the drain port
82
d,
so that pressure of the working oil in the first oil pressure supply passage
39
becomes high.
The housing
82
is provided with a first oil pressure switch
88
to confirm opening-closing motion of the spool
83
which detects oil pressure of the outlet port
82
b
and turns on or off when the oil pressure is low or high.
Oil pressure of the second oil pressure supply passage
74
is also changed by the second oil pressure responsive valve
81
which has the same construction as the first oil pressure responsive valve
80
. Also on the side of the exhaust valve
12
are provided first and second oil pressure responsive valves
80
,
81
of the same construction as those on the suction valve
11
side.
Referring to
FIG. 9
, the linear solenoid valve
90
is provided with a cylindrical sleeve
91
, a spool
92
slidingly fitted into the sleeve
91
, a duty solenoid
93
fixed to the sleeve
91
to drive the spool
92
, and a spring
94
forcing the spool
92
toward the duty solenoid
93
. Electric current supplied to the duty solenoid
93
is duty controlled with ON duty by instruction from valve operation control means in the electronic control unit
76
, so that an axial position of the spool
92
can be altered continuously against the spring
94
.
The sleeve
91
has a central inlet port
91
a,
an advance port
91
b
and a retard port
91
c
positioned on both sides of the inlet port
91
a
respectively, and drain ports
91
d,
91
e
positioned outside of the ports
91
b,
91
c
respectively. On the other hand, the spool
92
has a central groove
92
a,
lands
92
b,
92
c
positioned on both sides of the groove
92
a
respectively, and grooves
92
d,
92
e
positioned outsides of the lands
92
b,
92
c
respectively. The inlet port
91
a
is connected with the oil pump
70
, the advance port
91
b
is connected with the advance chamber
61
of the valve phase variable mechanism
50
, and the retard port
91
c
is connected with the retard chamber
62
of the valve phase variable mechanism
50
.
When the engine
1
is rotated at a low speed, if the first solenoid valve
85
and the second solenoid valve close in accordance with instruction from the valve operation control means of the electronic control unit
76
to close the first and second oil pressure responsive valves
80
,
81
and oil pressure supplied to the first and second connection changing mechanisms
30
,
31
become low, oil pressures of the first and second oil pressure chambers
37
,
45
communicating with the first and second oil pressure supply passages
39
,
47
in the rocker shaft
18
become low. Therefore, the connecting piston
32
and the regulating member
33
of the first connection changing mechanism
30
are moved to the disconnecting position (
FIG. 4
) by the return spring
34
, and the connecting piston
41
, the connecting pin
42
and the regulating member
43
of the second connection changing mechanism
31
are moved to the disconnecting position (
FIG. 5
) by the return spring
44
. As a result, the first, second and third rocker arms
19
,
20
,
21
are disconnected from each other, one of the suction valves
11
is opened and closed by the first rocker arm
19
with the first roller
27
touching the cam for low speed
15
, and another suction valve
11
is substantially closed by the third rocker arm
21
with the third roller
29
touching the upheaved portion
17
. At that time, the second rocker arm
20
with the second roller
28
touching the cam for high speed
16
runs idle regardless of operation of the suction valve
11
.
When the engine
1
is rotated at a middle speed, the first solenoid valve
85
is opened in accordance with an instruction from the valve operation control means of the electronic control unit
76
, the first oil pressure responsive valve
80
is opened, and pressure of the working oil supplied to the first connection changing mechanism
30
of the valve characteristic changing mechanism
13
becomes high. Therefore, oil pressure of the first oil pressure chamber
37
communicates with the first oil pressure supply passage
39
in the rocker shaft
18
becomes high, and the connecting piston
32
and the regulating member
33
is moved to the connecting position against the return spring
34
. On the one hand, the second connection changing mechanism
31
is in the disconnecting position. As the result, the first and third rocker arms
19
,
21
are connected to each other and rocking motion of the first rocker arm
19
with the first roller
27
touching the cam for low speed
15
is transmitted to the third rocker arm
21
connected to the first rocker arm so that both the suction valves
11
are driven to open and close. At that time, the third roller
29
of the third rocker arm
21
is distant from the upheaved portion
17
, and the second rocker arm
20
runs idle regardless of operation of the suction valve
11
.
When the engine
1
is rotated at a high speed, the first solenoid valve
85
and a second solenoid valve are opened in accordance with an instruction from the electronic control unit
76
, the first and second oil pressure responsive valves
80
,
81
are opened and pressures of the working oils supplied to the first and second connection changing mechanisms
30
,
31
of the valve characteristic changing mechanism
13
become high. Therefore, oil pressures transmitted to the first and second oil pressure chambers
37
,
45
from the first and second oil pressure supply passages
39
,
47
in the rocker shaft
18
become high. As the result, the connecting piston
32
and the regulating member
33
of the first connection changing mechanism
30
remain in the connecting position, on the one hand the connecting piston
41
, the connecting pin
42
and the regulating member
43
move to the connecting position against the return spring
44
, and the first, second and third rocker arms
19
,
20
,
21
are integrally connected, so that rocking motion of the second rocker arm
20
with the second roller
28
touching the cam for high speed
16
is transmitted to the first and third rocker arms
19
,
21
integrally connected to the second rocker arm
20
, and the two suction valves
11
are driven so as to open and close. At that time, the cam for low speed
15
runs idle being distant from the first roller
27
of the first rocker arm
19
and the upheaved portion
17
runs idle being distant from the third roller
29
of the third rocker arm
21
.
Thus, on the low speed rotation of the engine
1
, one of the suction valves
11
is driven at a small lift and a small opening period, and another suction valve
11
is In substantially closed resting state. On the middle rotation of the engine
1
, both the suction valves
11
can be driven at the small lift and the small opening period. On the high rotation of the engine
1
, both the suction valves
11
can be driven at a large lift and a large opening period.
The above is the same with respect to the valve characteristic changing mechanism
13
of the exhaust valve
12
side and operation of the two exhaust valves
12
, too.
Next, operation of the valve phase variable mechanism
50
will be described.
When the engine
1
is stopped, the valve phase variable mechanism
50
is kept at a most retarded state in which volume of the retard chamber
62
is largest, volume of the advance chamber
61
is zero and the lock pin
57
is fitted to the lock hole
8
c
of the cam sprocket
8
. When the engine is started, the oil pump
70
operates and if oil pressure supplied to the advance chamber
61
through the linear solenoid valve
90
exceeds a predetermined value, the lock pin
57
leaves the lock hole
8
c
by the oil pressure to allow operation of the valve phase variable mechanism
50
.
In this state, if duty ratio of the duty solenoid is increased from a set value corresponding to a neutral position, 50% for example, the spool
92
is moved from its neutral position shown in
FIG. 9
to the left so that the inlet port
91
a
connected with the oil pump
70
communicates with the advance port
91
b
through the groove
92
a
and the retard port
91
c
communicates with the drain port
91
e
through the groove
92
e.
As the result, oil pressure acts to the advance chamber
61
of the valve phase variable mechanism
50
, so that the suction cam shaft
9
rotates anticlockwise in
FIG. 6
relatively to the cam sprocket
8
and cam phase of the suction cam shaft
6
alters to the advance side continuously. Then, when a target cam phase is obtained, the duty ratio of the duty solenoid
93
is set at 50% to position the spool
92
of the linear solenoid valve
90
at the neutral position as shown in
FIG. 9
, where the inlet port
91
a
is closed between the lands
92
b,
92
c
and the retard port
91
c
and the advance port
91
b
are closed by the lands
92
b,
92
c
respectively. Thus, the cam sprocket
8
and the suction cam shaft
6
are fixed relatively to maintain the cam phase constant.
In order to alter the cam phase of the suction cam shaft
6
to the retard side continuously, the duty ratio of the duty solenoid
93
is reduced from 50% to move the spool
92
to the right from the neutral position, so that the inlet port
91
a
connected with the oil pump
70
communicates with the retard port
91
c
through the groove
92
a
and the advance port
91
b
communicates with the drain port
91
d
through the groove
92
d.
When a target cam phase is obtained, the duty ratio of the duty solenoid
93
is set at 50% to position the spool
92
at the neutral position as shown in FIG.
9
. Thus, the inlet port
91
a,
the retard port
91
c
and the advance port
91
b
are closed to maintain the cam phase constant.
In this manner, opening-closing period of the suction valve
11
can be advanced or retarded continuously over a range of 30 degrees of rotational angle of the suction cam shaft
6
, by altering phase of the suction cam shaft
6
with regard to phase of the crankshaft
4
by means of the valve phase variable mechanism
50
.
Next, modes of controlling the valve characteristic changing mechanism
13
and modes of changing the fuel injection amount and the ignition period with respect to the suction valve
11
will be described with reference to flow charts. Those with respect to the exhaust valve
12
are the same.
FIG. 10
is a flow chart showing a routine for changing valve operation characteristic between a low speed rotation and a middle speed rotation by the first connection changing mechanism
30
of the valve characteristic changing mechanism
13
and for changing maps of fuel ignition amount and ignition period. The routine is carried out every set times.
At the step S
11
, whether a sensor or the like is out of order or not is discriminated, and if it is out of order, close instruction is sent to the first solenoid valve
85
at the step S
12
to obtain the low speed valve operation characteristic in which one of the suction valves
11
is driven by the cam for low speed
15
and another suction valve
11
is substantially closed to rest.
If it is discriminated to be not out of order at S
11
, the flow advances to S
13
, and if the engine
1
is in starting operation, and after-starting delay timer T
5
is set at a set time, 5 seconds for example, at S
14
, then the flow advances to S
12
to close the first solenoid valve
85
.
When starting of the engine
1
is completed, until the after-starting delay timer TS times up at S
15
, the flow goes to S
12
to maintain the first solenoid valve
85
in the closed state. When the set time of the after-starting delay timer TS elapses, namely when 5 seconds elapses after starting, whether the cooling water temperature TW is lower than a set water temperature TW
1
, for example 60°, or not, namely whether warming of the engine has been completed or not, is discriminated based on a detecting signal of a cooling water temperature sensor at S
16
. If it is in warming-up, a change prohibiting flag FIN for prohibiting changeover of the valve operation characteristic by the first connection changing mechanism
30
is set at “1” at the step S
17
, then the flow advances to the step S
19
.
When the warming-up is completed, the change prohibiting flag FIN is set at “0” at the step S
18
. At the step S
19
, whether the change prohibiting flag FIN is set at “1” or not, namely whether the change is prohibited or not, is discriminated, and when the change is prohibited, the close instruction is sent to the first solenoid valve
85
at the step S
12
.
If the change prohibiting flag FIN is not “1” at the step S
19
, whether the engine rotational speed detected by a rotational speed sensor is lower than a set rotational speed Ne
1
, for example 2000 rpm, or not is discriminated at the step S
20
, and when the rotational speed is lower than the set rotational speed Ne
1
, that is on low speed rotation, the flow advances to the step S
21
. When the fuel injection amount map and the injection period map for middle speed are not selected at the last time, namely when the first connection changing mechanisms
30
of all cylinders are not changed to middle speed valve operation characteristics, at the step S
21
, the flow advances to the step S
12
.
When maps of fuel injection amount and ignition period for middle speed have been selected at S
21
, the closing instruction is sent to the first solenoid valve
85
at S
22
, then whether the first oil pressure switch
88
is turned on or not, namely whether oil pressure of the first oil pressure supply passage
39
is low or not, is discriminated at S
23
. When the first solenoid valve
85
is changed over from open to close, until the first oil pressure switch is turned on at S
23
, the flow advances to S
31
and further a series of treatments of STEPS s
32
to S
35
, setting of delay time for low speed, setting of changing delay timer for low speed TL, selection of fuel injection amount map for middle speed used in fuel injection amount control routine and ignition period map for middle speed used in ignition period control routine, and setting of the middle speed valve operation characteristic flag F
1
to “1”, are carried out, to use the map for middle speed continuously.
When the first oil pressure switch
88
is turned on at S
23
, whether the set time of the changing delay timer for low speed TL has elapsed or not is discriminated at S
24
. When the set time of the timer TL does not elapse, fuel injection amount map for middle speed and the ignition period map for middle speed are selected at S
34
and the middle speed valve operation characteristic flag F
1
is set to “1” at S
35
.
When the set time of the changing delay timer for low speed TL elapses at S
24
, at all cylinders, the valve operation characteristic is changed from the middle speed valve operation characteristic in which both suction valves
11
are driven by the cam for low speed
15
to the low speed valve operation characteristic in which one of the suction valves
11
is driven by the cam for low speed
15
and another suction valve
11
is substantially closed to rest. Then, a delay time for middle speed is set at S
25
and the time is set in the changing delay timer for middle speed TM
1
at S
26
. In succession, the fuel injection amount map for low speed and the ignition period map for low speed are selected by the map changing means of the electronic control unit
76
at S
27
to change from the map for middle speed to the map for low speed. Thereafter, the middle speed valve operation characteristic flag F
1
is set to “0” at S
28
, because the valve operation characteristic at that time is the low speed valve operation characteristic.
If the engine rotational speed Ne is above the set rotational speed Ne
1
at S
20
, opening instruction, that is, an instruction for changing to the middle speed valve operation characteristic is sent to the first solenoid valve
85
at S
29
. And whether the first oil pressure switch
88
turns off or not, that is, whether oil pressure of the first oil pressure supply passage
39
is high or not is discriminated at S
30
. When the first solenoid valve
85
is changed from “close” to “open”, until the first oil pressure switch
88
is turned off from “on”, the flow advances to S
24
, and further a series of treatments of steps S
25
to S
28
, setting of delay time for middle speed, setting of changing delay timer TM
1
for middle speed, selection of fuel injection amount map for low speed and ignition period map for low speed, and setting of the middle speed valve operation characteristic flag F
1
to “0” are carried out, to use the map for low speed continuously.
When the first oil pressure switch
88
is turned off for showing high pressure of the first oil pressure supply passage
39
at S
30
, whether the changing delay timer for middle speed TM
1
times up or not is discriminated at S
31
. If the set time of the timer TM
1
does not elapse, the fuel injection amount map for low speed and the ignition period map for low speed are selected at S
27
and the middle speed valve operation characteristic flag F
1
is set to “0” at S
28
.
When the set time of the changing delay timer for middle speed TM
1
elapses at S
31
, at all cylinders, the valve operation characteristic is changed from the low speed valve operation characteristic in which one of the suction valves
11
is driven by the cam for low speed
15
and another suction valve
11
is substantially closed to rest to the middle speed valve operation characteristic in which both suction valves are driven by the cam for low speed
15
. Then, a delay time for low speed is set at S
32
and the time is set in the changing delay timer for low speed TL at S
33
. In succession, the fuel injection amount map for middle speed and the ignition period map for middle speed are selected by the map changing means of the electronic control unit
76
at S
34
to change from the map for low speed to the map for middle speed. Therefore, the middle speed valve operation characteristic flag F
1
is set to “1” at S
35
.
The times which are set in the changing delay timers for low speed and middle speed TL, TM
1
are set by a delay time setting routine to be mentioned later adapted to a time required for completing changing actions of the first connection changing mechanisms
30
of all cylinders when oil pressure of the first oil pressure supply passage
39
is altered, and reflect property of the oil operating the valve characteristic changing mechanism
13
, particularly its viscosity. Therefore, responsiveness of changing of the valve operation characteristic to the oil property is taken into consideration. Accordingly, even if the oil property is altered by change of engine operational condition for example, timing of changing maps for low speed and maps for middle speed to each other after the delay time elapses coincides with timing of completion of changing of the valve operation characteristics at all cylinders, so that fuel injection amount and ignition period appropriate for the valve operation characteristic over a wide range of engine operation can be obtained and improvement of exhaust emission is possible.
When it is discriminated to be out of order at S
11
, when it is discriminated to be in starting at S
13
, when it is discriminated that
5
seconds do not elapse after completion of starting at S
15
, when the change prohibiting flag is not set to “1” at S
19
, and when fuel injection amount map and ignition period map for middle speed have been selected at S
21
, the flow advances to S
12
to close the first solenoid valve
85
. After that, a delay time for middle speed is set at S
25
, the time is set in the changing delay timer for middle speed TM
1
AT S
26
, the fuel injection amount map for low speed and the ignition period map for low speed are selected at S
27
, and the middle speed valve characteristic flag F
1
is set to “0” at S
28
.
Next, a routine for changing valve operation characteristic and changing maps of fuel injection amount and ignition period between middle speed rotation and high speed rotation by the second connection changing mechanism
31
of the valve characteristic connection changing mechanism
31
of the valve characteristic changing mechanism
13
.
FIG. 11
shows this changing routine which is carried out every set times.
At S
41
, whether a sensor or the like is out of order or not is discriminated, and if it is out of order, chose instruction is sent to the second solenoid value at S
42
. In accordance with the engine rotational speed Ne at that time, the suction valves
11
becomes that low speed valve operation characteristic in which one of the suction valve
11
is driven by the cam for low speed
15
and another suction valve
11
is substantially closed to rest, or the middle speed valve operation characteristic in which both suction valves
11
are driven by two cam for low speed
15
. After the second solenoid valve is closed at S
42
, the flow advances at S
49
.
If it is discriminated to be not out of order at S
41
, the flaw advances to S
43
and whether the middle speed valve operation characteristic flag F
1
is “1” or not, namely whether the suction valve
11
is in the middle speed valve operation characteristic or not is discriminated. If the valves
11
is not in the middle speed valve operation characteristic, close instruction is sent to the second solenoid valve at S
42
and the valves
11
becomes the low speed valve operation characteristic in which one of the suction valves
11
is driven by the cam for low speed
15
and another suction valve
11
is substantially chose to rest.
When it is in the middle speed valve operation characteristic at S
43
, whether the engine rotational speed Ne is lower than a set rotational speed Ne
2
, for example 500 rpm, a not is discriminated at S
44
, and when the engine rotational speed is lower than the set rotational speed Ne
2
, namely in middle speed operation, whether the high speed valve characteristic flag F
2
has been set to “1” a not is discriminated at S
45
. If the high speed valve operation characteristic flag F
2
is “0”, namely if the second connection changing mechanism
31
of all cylinders are not changed to the high speed valve operation characteristic, the flow advances at A
42
. At that time the suction valve
11
are in the middle speed valve operation characteristic in which the suction valve
11
are driven by the cam for low speed
15
.
When the high speed valve operation characteristic has been “1” at S
45
, after the close instruction is sent to the second solenoid valve at S
46
, whether or not the second oil pressure which is turned on, namely pressure of the second oil pressure supply passage
47
is low, is discriminated at S
47
.
When the second solenoid valve changes from “open” to “close”, until the second oil pressure switch turns on at S
47
, the flow advances to S
55
, further a series of treatments of S
56
to S
59
, namely setting delay time for middle speed, setting of the middle speed changing delay timer TM
2
, selection of the high speed fuel ignition amount map and the high speed ignition period map, and setting high speed valves apparatus characteristic of flag F
2
to “1”, are carried out to use the map for high speed continuously.
When the second oil pressure switch is turned on to lower the pressure at step S
47
, it is judged, at step S
48
, whether or not the set time elapses with the changing delay timer for middle speed TM
2
. When time is not up with the changing delay timer for middle speed TM
2
, the fuel injection quantity map for high speed and the ignition timing map for high speed are selected at step S
88
, and the high-speed valve operating characteristic flag F
2
is set to “1” at step S
89
.
When the set time elapses with the changing delay timer for middle speed TM
2
at step S
48
, all the cylinders are changed from high-speed valve operating characteristics in which both the suction valves
11
are driven by the cam for high speed
16
to middle-speed valve operating characteristics in which both the suction valves
11
are driven by the cam for low speed
15
. The delay time for high speed is set at step S
49
and the time is set to the changing delay timer for high speed TH at step S
50
. Successively, at step S
51
, the fuel injection quantity map for middle speed and the ignition timing map for middle speed are selected by the map changing means of the electronic control unit
76
, thereby changing from the map for high speed to the map for middle speed. Thereafter, at step S
52
, the valve operating characteristics at this time are middle-speed valve operating characteristics, and hence the high-speed valve operating characteristic flag F
2
is set to “0”.
When the engine speed is equal to or more than the set speed Ne
2
at step S
44
, a valve opening command of the second solenoid valve, i.e., a changing command to the high-speed valve operating characteristics, is issued at step S
53
. And, it is judged, at step S
54
, whether or not the second oil pressure switch is turned off, i.e. whether or not oil pressure of the second oil pressure supply passage
47
is increased to high pressure. At the time of changing from closing of the second solenoid valve to opening thereof, while the second oil pressure switch is turned from on to off at step S
54
, the flow proceeds to step S
48
, and furthermore a series of processes at steps S
49
to S
52
are executed, i.e. setting of the delay time for high speed, setting of the changing delay timer TH for high speed, a selection of the fuel injection quantity for middle speed and the ignition timing map for middle speed, and setting of the high-speed valve operating characteristic flag F
2
to “0” are executed, and the map for middle speed is continuously used.
When the second oil pressure switch is turned off to increase the pressure of the second oil pressure supply passage
47
at step S
54
, it is judged, at step S
55
, whether or not the set time elapses with the changing delay timer for high speed TH. When the set time has not elapsed with the changing delay timer for high speed TH, the fuel injection quantity map for middle speed and the ignition timing map for middle speed are selected at step S
51
, and the high-speed valve operating characteristic flag F
2
is set to “0” at step S
52
.
When the set time elapses with the changing delay timer for high speed TH is at step S
55
, all the cylinders are changed from middle-speed valve operating characteristics in which both the suction valves
11
are driven by the cam for low speed
15
to high-speed valve operating characteristics in which both the suction valves
11
are driven by the cam for high speed
16
. And, the delay time for middle speed is set at step S
56
and the time is set to the changing delay timer for middle speed TM
2
at step S
57
. Successively, at step S
58
, the fuel injection quantity map for high speed and the ignition timing map for high speed are selected by the map changing means of the electronic control unit
76
, thereby changing from the map for middle speed to the map for high speed. Thereafter, at step S
59
, the high-speed valve operating characteristic flag F
2
is set to “1”.
In this step also, the delay time to be set to the delay timers for middle speed TM
2
and high speed TH is set in conformity with a period of time in which oil pressure of the second oil pressure supply passage
47
changes and the second connection changing mechanisms
31
of all the cylinders have completed changing operations, and the values are set in the below-described delay time set routine as well as the delay time in the first connection changing mechanism
30
. Accordingly, properties of oil affect the time, and even if the oil properties change due to change in driving state of the engine, timing of changing between both the maps for middle speed and both the maps for high speed after this delay time has elapsed substantially coincides with a timing in which changing of the valve operating characteristics of all the cylinders has completed. For this reason, the fuel injection quantity and the ignition timing are set appropriately for the valve operating characteristics in a wide range of an engine drive region, thereby enabling improvement in exhaust emission.
In this connection, when it is judged, at step S
41
, that a fault occurs, when the middle-speed valve operating characteristics flag F
1
is not set to “1” at step S
43
, and when the previous high-speed valve operating characteristic flag F
2
is not set to “1” at step S
45
, the flow proceeds to step S
42
as described above, and the second solenoid valve is closed, thereafter the delay time for high speed is set at step S
49
, and the time is set to the changing delay timer for high speed TH at step S
50
, the fuel injection quantity map for middle speed and the ignition timing map for middle speed are selected at step S
51
, and the high-speed valve operating characteristic flag F
2
is set to “0” at step S
52
.
A control aspect of a valve phase variable mechanism
50
will be described with reference to a flowchart.
A flowchart of
FIG. 12
shows a routine of calculating a target cam phase and this routine is executed in each set time.
First of all, when the internal combustion engine
1
is driven for starting at step S
61
, a started state cam phase control disable timer TS is set to a set time, e.g., 5 sec, at step S
62
, a valve phase variable mechanism operating delay timer TD is set to a set time, e.g., 0.5 sec, at step S
63
, and a target cam phase CM is set to “0”, at step S
64
, and a valve phase variable mechanism control enable flag F indicating whether to enable operation of the valve phase variable mechanism
50
is set to “0”, at step S
65
, and the operation is disabled.
When the internal combustion engine
1
has completed starting, until the set time elapses with the started state cam phase control disable timer TS at step S
66
, the flow proceeds to step S
63
, and, in turn, transfer to steps S
64
and S
65
, and the operation of the valve phase variable mechanism
50
is disabled. When the set time elapses with the started state cam phase control disable timer TS and 5 sec elapses after started, the flow transfers to step S
67
. If a valve phase variable mechanism fault flag FNG is set to “1” at step S
67
, or a fault of a sensor, etc. other than the valve phase variable mechanism
50
of a sensor, etc. occurs at step S
68
, the flow transfer to steps S
63
to S
65
, and the operation of the valve phase variable mechanism
50
is disabled.
If a fault does not occur in both steps S
67
and S
68
, it is judged, at step S
69
, whether or not the internal combustion engine
1
is driven idly, at step S
69
. During the idle driving, e.g., a throttle valve opening detected by a throttle valve opening sensor is an entirely closed state, and also when engine speed detected by a speed sensor is in the proximity of 700 rpm, the flow transfers to steps S
63
to S
65
, and the operation of the valve phase variable mechanism
50
is disabled.
If not during the idle driving at step S
70
, it is judged whether or not coolant temperature TW detected by a coolant temperature sensor is between a lowermost value TW
2
, e.g., 0° C. and an uppermost value TW
3
, e.g., 110° C. It is judged, in turn, at step S
71
, whether or not engine speed Ne detected by the speed sensor is higher than a lowermost value Ne
3
, e.g., 1500 rpm, and if respective conditions of steps S
70
and S
71
prove abortive, the flow transfers to steps S
63
to S
65
, and the operation of the valve phase variable mechanism
50
is disabled.
When it is judged, at step S
71
, that the engine speed Ne is higher than the lowermost value Ne
3
, the flow transfers to step S
72
so that the valve phase variable mechanism
50
is operated. At step S
72
, a map of a target cam phase set by use of negative a suction minus pressure and the engine speed as parameters is retrieved. Here, a means for retrieving a target cam phase CM at step S
72
is a target phase setting means.
At step S
73
, the value procured by retrieving at step S
72
is set as the target cam phase CM. At step S
74
, in order to prevent hunting when the valve phase variable mechanism
50
is transferred from a non-operating state to an operating state, after the valve phase variable mechanism operating delay timer TD awaits time-up, the valve phase variable mechanism control enable flag F is set to “1” at step S
75
, and the operation of the valve phase variable mechanism
50
is enabled.
A flowchart of
FIG. 13
shows a routine of feedback-controlling a cam phase by means of the valve phase variable mechanism
50
, and this routine is executed in each set time.
First of all, when a valve phase variable mechanism fault flag FNG is not set to “1” at step S
81
and the valve phase variable mechanism
50
is normal, and further the valve phase variable mechanism enable flag F is set to “1” at step S
82
and the valve phase variable mechanism
50
is being operated, a deviation DM between the target cam phase CM calculated in a target cam phase calculation routine and a real cam phase C which is an actual cam phase calculated from outputs of a suction cam shaft sensor
67
and a crankshaft sensor is calculated at step S
83
, and also a difference DC between a real cam phase C(n−1) in a previous loop and a real cam phase C(n) in a present loop is calculated at step S
84
. Here, a means for calculating the real cam phase C from the outputs of the suction cam shaft sensor
67
and the crankshaft sensor is a phase detecting means.
If the valve phase variable mechanism control enable flag F changes from “0” to “1” at next step S
85
, i.e., in case the operation of the valve phase variable mechanism
50
is changed from the disable to the enable in a present loop, the flow transfers to step S
86
, and the deviation DM is compared with a first feedforward control decision value D
1
, e.g., a value corresponding to 10° crank angle. This results in that, if the deviation DM is greater than the first feedforward control decision value D
1
, a feedforward control flag FFF is set to “1” at step S
87
, and the valve phase variable mechanism
50
which should intrinsically be feedback-controlled is feedforward-controlled.
That is, after a manipulated variable D(n) in a present loop of the valve phase variable mechanism
50
is set to an uppermost value DH
1
at step S
89
, a duty ratio DOUT of a linear solenoid valve
90
of the valve phase variable mechanism
50
is set as a present manipulated variable D(n) at step S
103
. In subsequent loops, as the decision result at step S
85
is NO and also the decision result at step S
90
is YES, the deviation and the first feedforward control decision value D
1
are recompared in size at step S
86
, and while the deviation DM is greater, the flow transfers to step S
103
through steps S
87
to S
89
.
Accordingly, if a deviation DM between a target cam phase CM and a real cam phase C is great, when the valve phase variable mechanism
50
is started controlling, a present manipulated variable D(n) of the valve phase variable controlling is set to the uppermost value DH
1
which is a constant, while the state continues, whereby the valve phase variable mechanism
50
is feedforward-controlled. As mentioned above, only while convergence is feared since the deviation DM is great, the feedforward control continues, with the result that responsibility and convergence can be made compatible.
In case the deviation DM is equal to or smaller than the first feedforward control decision value D
1
from the beginning of control at step S
86
, or in case the deviation DM becomes equal to or smaller than the first feedforward control decision value D
1
during the aforesaid feedforward control, the feedforward control flag FFF of the valve phase variable mechanism
50
is set to “0” at step S
91
, and the flow transfers to step S
92
. At step S
92
, if a previous integral term D
1
(n−1) is zero, a previous integral term D
1
(n−1) is set to an initial value at step S
93
.
At step S
94
, the deviation DM (in case the target cam phase CM is greater than the real cam phase C) is compared with a second feedforward control decision value D
2
which is smaller than the first feedforward control decision value D
1
. This results in that, if the deviation DM between the both is great, after a present manipulated variable D(n) is set to an uppermost value DH
2
at step S
95
, the duty ratio DOUT of the linear solenoid valve
90
is set as the present manipulated variable D(n) at step S
103
.
Likewise, at step S
96
, the deviation DM (in case the target cam phase CM is smaller than the real cam phase C) is compared with a third feedforward control decision value D
3
which is smaller in absolute value than the first feedforward control decision value D
1
. This results in that, if the deviation DM between the both is great, the duty ratio DOUT of the linear solenoid valve
90
is set as the present manipulated variable D(n) at step S
103
after a present manipulated variable D(n) is set to a lowermost value DL
2
at step S
97
,.
Thus, even after the deviation DM becomes the first feedforward control decision value D
1
or less at step S
86
, until the deviation DM becomes the second and third feedforward control decision value D
2
, D
3
or less at steps S
94
, S
96
, the present manipulated variable D(n) is switched from the uppermost value DH
1
to the uppermost value DH
2
or the lowermost value DL
2
and the feedforward controlling continues, whereby the responsibility and convergence are contrived to make compatible.
If the absolute value of the deviation DM is sufficiently reduced by the aforesaid feedforward control and both the steps S
94
and S
96
end in failure, after a proportional term gain KP, an integral term gain K
1
, and a differential term gain KV are calculated at step S
98
in order to perform PID feedback controlling, a proportional term DP, an integral term DI, and a differential term DV are calculated by the following equation at step S
99
, respectively:
DP=KP*DM
DI=KI*DM+DI
(
n−
1)
DV=KV*DC
At step S
100
, the present manipulated variable D(n) of the PID feedback controlling is calculated as a sum of the proportional term DP, the integral term DI, and the differential term DV.
Successively, at steps S
101
and S
102
, a limit process of the present manipulated variable D(n) is executed. That is, if the present manipulated variable D(n) exceeds an uppermost value DH
3
at step S
101
, an uppermost value DH
2
is set as the present manipulated variable D(n) at step S
95
, and also if the present manipulated variable D(n) is less than a lowermost value DL
3
at step S
102
, a lowermost value DL
2
is set as the present manipulated variable D(n) at step S
97
. At step S
103
, the present manipulated variable D(n) is used as the duty ratio DOUT of the linear solenoid valve
90
, and the valve phase variable mechanism is feedback-controlled so that the deviation DM between the target cam phase CM and the real cam phase C is converged to zero.
In the meantime, when the valve phase variable mechanism
50
is failing at step S
81
and a valve phase variable mechanism fault flag FNG is set to “1”, at step S
105
through step S
104
, a value of the present manipulated variable D(n) is set to, e.g., a fault recovery set value DT equivalent to the duty ratio 50% of the linear solenoid valve
90
, and at next step S
106
, a fault recovery timer TNG is set. While the set time elapses with the fault recovery timer TNG from a next loop, a decision result at step S
104
is NO and the present manipulated variable C(n) is set to “0” at step S
107
.
According to such control, in case the valve phase variable mechanism
50
failed. the valve phase variable mechanism
50
is set in a most angularly retarded state, and besides the linear solenoid valve
90
forthwith interconnects an inflow port
91
a
to an angular advance port
91
b
within a set time, and the valve phase variable mechanism
50
can be operated to an angularly advanced side. This results in that, in case a fault occurs due to bite-in of dust, or in case a fault decision is made in an instant by pulsation, etc. of the oil pressure circuit, the valve phase variable mechanism
50
or the linear solenoid valve
90
can automatically be recovered to a normal state.
Furthermore, when the valve phase variable mechanism control enable flag F is set to “0” at step S
82
and the operation of the valve phase variable mechanism
50
is disabled, the valve phase variable mechanism feedforward control flag FFF is set to “0” at step S
108
, and, in turn, after the present manipulated variable D(n) of the valve phase variable mechanism
50
is set to the lowermost value DL
1
at step S
109
, the duty ratio DOUT of the linear solenoid valve
90
of the valve phase variable mechanism
50
is set as the present manipulated variable D(n) at step S
103
.
A flowchart of
FIG. 14
is a flowchart of valve operating characteristics by the first connection changing mechanism
30
and a changing routine of both the maps of fuel injection quantity and ignition timing as shown in
FIG. 10
, indicating a delay time set routine executed at respective steps S
25
and S
32
for setting a delay time to be set to respective changing delay timers for low speed and middle speed TL, TM
1
.
By use of the difference DC between the previous real cam phase C(n−1) and the present real cam phase C(n) calculated in feedback control of the cam phase by the valve phase variable mechanism
50
, i.e., a change speed of the real cam phase C, and the duty ratio of a current quantity which is duty-controlled for retaining a spool
92
of the linear solenoid valve
90
at a neutral position, properties of oil which is an operating oil are detected and a delay time is set based on the detected oil properties.
First, it is judged, at step Slll, whether or not coolant temperature TW is lower than a set value TW
4
(e.g., 80° C.) higher than a warm-up decision temperature based on a detection signal from a coolant temperature sensor. When the coolant temperature TW is lower than the set value TW
4
, as oil temperature takes various values according to a state of the internal combustion engine
1
, the oil properties represented by the viscosity of an oil are various. Therefore, it is necessary to know the oil properties including the viscosity of an oil, in order that the operating responsibility of a valve characteristic changing mechanism
13
depending on the oil properties, i.e., a time required for changing operation is accurately evaluated. On the other hand, when the coolant temperature TW is equal to or more than this set value TW
4
, great changes do not occur in the operating responsibility of the valve characteristic changing mechanism
13
due to changes in oil temperature. Therefore, in case it is judged that the coolant temperature TW is equal to or more than the set value TW
4
at step S
111
, control proceeds to step S
112
, and the delay time is constant to a set value (a fixed value), e.g., 0.2 sec.
When the coolant temperature TW is lower than the set value TW
4
, it is judged, at step S
113
, whether or not the engine speed Ne is in the range of the set lowermost value Ne
5
and the uppermost value Ne
6
containing the changing speed of valve operating characteristics by the valve characteristic changing mechanism
13
, e.g., in the range of 1000 to 3000 rpm, based on a detection signal from the speed sensor. When the engine speed is outside this range, the delay time is set as a set value at step S
112
.
When it is judged that the engine speed Ne is within the set range at step S
113
, it is judged, at step S
114
, whether or not the present target cam phase CM(n) changes from the previous target cam phase CM(n−1), and in case there is a change, it is judged, at step S
115
, whether or not the set time elapses with a first timer T
1
with the passage of a set time, e.g., a predetermined time of a period of time of 1 to 2 sec, and when the set time elapses, after the set time is set in the first timer T
1
at step S
116
, the flow proceeds to step S
112
.
In case it is judged, at step S
115
, that the set time has not elapsed with the first timer T
1
, at step S
117
, a delay time is acquired with reference to a map indicating a relationship between the delay time and the difference DC as shown in
FIG. 16
, based on the difference DC between the previous real cam phase C(n−1) and the present real cam phase C(n) which is acquired at step S
84
in the flowchart of the feedback control routine of FIG.
13
. Here, a means for acquiring the difference DC between the previous real cam phase C(n−1) and the present real cam phase C(n) at step S
84
is a phase change speed calculating means for calculating a change speed of a phase, constituting an operating oil property detecting means. Furthermore, a means for acquiring a delay time at step S
117
is a delay time setting means. In this connection, two types of map are prepared for use in the aforesaid steps S
25
and S
32
, respectively, and are stored in a memory of an electronic control unit
76
.
The reason why it is possible to detect the oil properties from the difference DC between the previous real cam phase C(n−1) and the present real cam phase C(n) is that the valve phase variable mechanism
50
as a device for changing a cam phase is operated by the pressure of the oil and that the behavior depends on the oil properties such as viscosity of the oil, etc.
That is, in the valve phase variable mechanism
50
, oil controlled by the linear solenoid valve
90
is supplied to an angular advance chamber
61
and an angular retard chamber
62
of the valve phase variable mechanism
50
to rotate a suction cam shaft
6
. Accordingly, after the linear solenoid valve
90
starts controlling an opening area of an advance port
91
b
and a retard port
91
c,
and further after the oil passes through the oil passage and flows into the advance chamber
61
or the retard chamber
62
, the suction cam shaft
6
starts rotating by a difference in oil pressures between the advance chamber
61
and the retard chamber
62
, and a state of the valve phase variable mechanism
50
changes until the rotation ends. It is evident that such the state change depends on the oil properties represented by the viscosity of oil (oil temperature is one index indicating the oil properties, but this also finally relates to the viscosity of an oil). Therefore, it is possible to detect the properties of oil based on behavior of the valve phase variable mechanism
50
. Here, rotation state of the suction cam shaft
6
reflects the behavior of the valve phase variable mechanism
50
after the oil flows into the advance chamber
61
or the retard chamber
62
, and the oil properties are detected from such rotation state.
This set time is determined taking into consideration a follow-up property of the real cam phase C with respect to the target cam phase CM (it is obvious that this follow-up property reflects the oil properties from the above), and the behavior of the valve phase variable mechanism
50
for a while immediately after the target cam phase CM changes reflects more accurately the oil properties because the advance port
91
b
or the retard port
91
c
of the linear solenoid valve
90
is entirely opened. After this set time has elapsed, judging from the operating responsibility of the valve phase variable mechanism
50
, there are great possibilities that the actual cam phase is in the vicinity of the target cam phase CM, and therefore the spool
92
of the linear solenoid valve
90
is in a state of approaching a neutral position for clogging the advance port
91
b
and the retard port
91
c,
and the change of the real cam phase C does not reflect accurately the oil properties. For this reason, the delay time is designed not to set from the change of the real cam phase C at this time.
When it is judged, at step S
114
, that the target cam phase does not change, it is judged, at step S
118
, whether or not the absolute value of the difference between the target cam phase CM and the real cam phase is within a value equivalent to 2° in crank angle, i.e., whether or not the real cam phase C converges to the target cam phase CM. When it is judged, at step S
118
, that there is a convergence, it is judged, at step S
119
, whether or not the set time elapses with a second timer T
2
with the elapse of a set time, e.g., 0.5 sec, and when the set time has not elapsed, process proceed to step S
112
. This set time is a latency until the real cam phase C coincides with the target cam phase CM from the vicinity of the target cam phase CM and the spool
92
of the linear solenoid valve
90
reaches a neutral position.
When it is judged, at step S
119
, that the set time of the second timer T
2
elapses, it is judged that a cam phase, i.e., a phase of a suction valve
11
, is equal to the target cam phase CM to be fixed, and after a set time is set to the second timer T
2
at step S
120
, a delay time is acquired at step S
121
, with reference to a map illustrating a relationship between a delay time and a duty ratio as shown in
FIG. 17
based on the duty ratio of the linear solenoid valve
90
when the spool
92
is at a neutral position. Here, in a valve operating control means of the electronic control unit
76
, a means for determining a duty ratio of a current quantity for retaining the spool
92
of the linear solenoid valve
90
at a neutral position is an operating oil property detecting means. Furthermore, a means for acquiring a delay time is a delay time setting means at step S
121
. Similarly to the map illustrating a relationship between a delay time and a difference D as shown in
FIG. 16
, two types of map are prepared for use in the aforesaid steps S
25
and S
32
, respectively, and are stored in a memory of the electronic control unit
76
.
The oil properties can be detected by the duty ratio of the linear solenoid valve
90
when the spool
92
is at a neutral position for retaining the cam phase at a constant value because a coil portion of the linear solenoid valve
90
is affected by an atmospheric temperature and its resistant value changes. That is, in a state that the linear solenoid valve
90
is warmed up, a current quantity when the spool
92
occupies the neutral position is set to be a duty ratio of 50%, but since a coil temperature of the linear solenoid valve
90
is also low during warming up and its resistant value is smaller than a value after warmed up, electric current with respect to the linear solenoid valve
90
is easy to flow. When current is easy to flow as mentioned above, in a state that a battery voltage is constant during warming up and after warmed up, a current quantity for retaining a neutral position of the spool
92
is same, but the duty ratio may be smaller than that after warmed up, and as the coil temperature is lower, the smaller is the duty ratio. On the other hand, as mentioned above, as oil temperature is also low during warming up, the viscosity as an oil property is larger than that after warmed up, and as the oil temperature is lower, this viscosity is larger. Accordingly, it is possible to detect the viscosity as an oil property by the duty ratio of the linear solenoid valve
90
when the spool
92
occupies the neutral position, i.e., when the cam phase is held constant.
When it is judged, at step S
118
, that the real cam phase C does not converge to the target cam phase CM, and when it is judged, at step S
122
, that the set time of a third timer T
3
is up with the elapse of a set time, e.g., a predetermined time of a period of time of 1 to 2 sec, after the set time is set to the third timer T
3
at step S
123
, the flow proceeds to step S
112
.
When it is judged, at step S
122
, that the set time has not elapsed with the third timer T
3
, the flow proceeds to step S
117
, and the delay time is acquired based on the difference DC. In this connection, the set time of the third timer T
3
has the same sense as the set time set to the first timer T
1
.
Also in the flowchart of the valve operating characteristics by a second connection changing mechanism
31
and the changing routine of both the maps of fuel injection quantity and ignition timing as shown in
FIG. 11
, in order to set the delay time to be set to respective delay timers for middle speed and high speed TM
2
, TH, the below routine is also used as a delay time setting routine which is executed at respective steps S
49
and S
56
. Namely, as a set range of the engine speed Ne at step S
113
in the flowchart of a routine for setting the delay time of the aforesaid first connection changing mechanism
30
, the lowermost value is changed to 4000 rpm and the uppermost value Ne
6
is changed to 6000 rpm, respectively, with the other steps remaining the same.
In this connection, the same routine as the routine for setting the delay time of the valve characteristic changing mechanism
13
at a suction valves
11
side is used in case the delay time of the valve characteristic changing mechanism
13
at an exhaust valve
12
side is set.
As the embodiment is constituted as above, the following effects can be exhibited.
The delay time, which determines a changing timing between the fuel injection quantity map and the ignition timing map in response to each of valve operating characteristics for low speed, middle speed, and high speed which are changed by the valve characteristic changing mechanism
13
, is reflected by the oil properties operating the valve characteristic changing mechanism
13
, in particular its viscosity, and as a result, it is equal to a value taking account of responsibility of changing operation of valve operating characteristics dependent on the oil properties. Accordingly, even if the oil properties change due to a change of the driving state of the engine, a timing of changing between the fuel injection quantity map and the ignition timing map after this delay time has elapsed substantially coincides with a timing when change of the valve operating characteristics of all the cylinders has been completed. For this reason, the fuel injection quantity and the ignition timing are suited for the valve operating characteristics ranging over a wide-range engine drive region and an improvement in exhaust emission is made possible.
As factors which influences on the oil properties, here, in addition to a factor (e.g., oil temperature) based on the engine drive state, there are types of oil, a secular change of oil, and the like, but all the factors are fetched in, and as the delay time can be set based on the resultant oil properties, it is possible to set the delay time more precisely than, e.g., the case of making use of the oil properties detected by an oil temperature sensor, and accordingly it is possible to set a more precise changing timing of both the maps of fuel injection quantity and ignition timing.
The oil properties can be detected based on a behavior of the valve phase variable mechanism
50
operating by an oil pressure of an oil, i.e., based on the deviation DM between the target cam phase CM calculated from a change of the real cam phase C dependent on operation of the valve phase variable mechanism
50
and the real cam phase C, or the difference DC (a change speed) of the real cam phase C. Therefore, a detection means for directly detecting the oil properties, e.g., an oil temperature sensor, is unnecessary and costs can be reduced.
Furthermore, since the difference DC of the real cam phase C is utilized, even in case the phase changes greatly, or in case it changes continuously, detection of operating oils properties is possible. Therefore, it is possible to detect in sequence the operating oils properties in the wide-range engine drive region.
In the difference DC of the real cam phase C which is utilized when the delay time is set, and the deviation DM between the target cam phase CM and the real cam phase C, it is possible to make use of data obtained in a process of feedback-controlling the cam phase to the target cam phase CM. Therefore, detection of the operating oil properties from a change of the cam phase does not need a peculiar device for acquiring the difference DC of the real cam phase C and the deviation DM between the target cam phase CM and the real cam phase C.
On the basis of a behavior of the linear solenoid valve
90
controlling the pressure of oil supplied to the valve phase variable mechanism
50
, i.e., on the basis of the duty ratio of a current quantity which is duty-controlled to the linear solenoid valve
90
when the spool
92
is at a neutral position for retaining fixedly the cam phase, the oil properties can be detected. Therefore, even in the engine drive region in which the cam phase does not change, it is possible to set the delay time in response to the oil properties.
A second embodiment of the present invention will now be described with reference to
FIGS. 15 and 18
, and according to the second embodiment of the present invention, only a delay time setting routine executed at respective steps S
25
, S
32
, S
49
, S
56
differs for setting the delay time to be set in the respective changing delay timers for low speed, middle speed, and high speed TL, TM
1
, TM
2
, TH, and the other constitution is the same as in the first embodiment.
This routine sets the delay time for setting to the respective delay timers for low speed and middle speed TL, TM
1
, and by making use of the deviation between the target cam phase CM and the real cam phase C which are calculated in feedback-controlling of the cam phase by the valve phase variable mechanism
50
, and the duty ratio of a current quantity which is duty-controlled for retaining the spool
92
of the linear solenoid valve
90
at a neutral position, the properties of oil which is an operating oil are detected and the delay times for low speed and middle speed are set based on the detected oil properties.
In a flowchart of
FIG. 15
, as steps S
131
and S
133
are the same as steps S
111
and S
112
of the flowchart of
FIG. 14
, the description will be omitted. However, in case a decision result at both the steps S
131
and S
133
is NO, the flow proceeds to step S
132
, and a delay time is set to a set value (a fixed value), e.g., 0.2 sec.
If it is judged, at step S
133
, that the engine speed Ne is within a set range, it is judged, at step S
134
, whether or not a present target cam phase CM(n) changes from the previous target cam phase CM(n−1), and in case there is a change, it is judged, at step S
135
, whether or not a change quantity of the target cam phase CM is smaller than a set value α. Interpreting this step S
135
, in case the oil properties are detected from the deviation DM between the target cam phase CM and the real cam phase C, as a course of changes of the target cam phase CM is various, the deviation DM under the conditions as same as possible must be utilized. This set value α is occasionally determined by experiments, etc. taking into account the above circumstances.
In case a change quantity of the target cam phase CM is equal to or more than a set value α at step S
135
, it is difficult to detect accurate oil properties from the above reasons, so that the flow proceeds to step S
132
, and the delay time is set to a set value (a fixed value), e.g., 0.2 sec.
In case a change quantity of the target cam phase CM is less than the set value α at step S
135
, it is judged, at step S
136
, whether or not the set time has elapsed with a fourth timer T
4
, and when the time has elapsed, timed out, after the set time is set to the fourth timer T
4
at step S
137
, the flow proceeds to step S
138
. When the set time has not elapsed with a fifth timer T
5
at step S
138
, at step S
139
, based on the deviation DM between the target cam phase CM and the real cam phase C acquired at step S
83
in the flowchart of the feedback control routine of
FIG. 13
, a delay time is acquired with reference to a map illustrating a relationship between the delay time and the deviation DM as shown in FIG.
18
. Here, a means for acquiring the deviation DM between the target cam phase CM and the real cam phase C at step S
83
is an operating oil properties detection means. Furthermore, a means for acquiring a delay time at step S
139
is a delay time setting means. Incidentally, two types of map are prepared for use in the aforesaid steps S
25
, S
32
, respectively, and are stored in a memory of the electronic control unit
76
.
The reason why it is possible to detect the oil properties from the deviation DM between the target cam phase CM and the real cam phase C is the same as it is possible to detect the oil properties from the aforesaid difference DC between the previous real cam phase C(n−1) and the present real cam phase C(n), and this is because the valve phase variable mechanism
50
as a device for changing a cam phase is operated by pressure of oil, and its behavior is dependent on the oil properties such as the viscosity of an oil, etc.
The significance of the steps S
136
and S
138
is the same as at step S
135
, and since a course of changes of the target cam phase CM is various as mentioned above, if the deviation DM at a specific period of time is not utilized when a small change of the target cam phase CM occurs, it is impossible to detect accurate oil properties.
When the set time of fourth timer T
4
is not up at step S
136
, and after it is judged, at step S
138
, that the set time elapses with a fifth timer T
5
and a set time is set to the fifth timer T
5
at step S
140
, the flow proceeds to step S
2
. Incidentally, the set time to be set to the fourth timer T
4
and the fifth timer T
5
is occasionally set from the viewpoint of accurate oil properties detection.
When it is judged, at step S
134
, that the target cam phase CM does not change, it is judged, at step S
141
, whether or not the absolute value of the deviation DM between the real cam phase C and the target cam phase CM is smaller than a valve equivalent to 2° in crank angle, i.e., it is judged whether or not the real cam phase C converges into the target cam phase CM. If it is judged, at step S
141
, that the real cam converges, it is judged, at step S
142
, whether or not the set time of a sixth timer T
6
is up with the elapse of the set time, e.g., 0.5 sec. and when the set time has not elapsed, the flow proceeds to step S
132
. This set time is a latency when the real cam phase C coincides with the target cam phase CM from the proximity of the target cam phase CM and the spool
92
of the linear solenoid valve
90
reaches a neutral position.
When it is judged, at step S
142
, that the set time of the sixth timer T
6
is up, it is judged that the cam phase, i.e., a phase of the suction valve
11
, is equal to the target cam phase CM to be constant, and after a set time is set to the sixth timer T
6
at step S
143
, based on the duty ratio of the linear solenoid valve
90
when the spool
92
is at a neutral position at step S
144
, a delay time is acquired with reference to a map illustrating a relationship between the delay time and the duty ratio as shown in
FIG. 17. A
means for acquiring the delay time at step S
144
is a delay time setting means. Incidentally, two types of map are prepared for use in the aforesaid steps S
25
and S
32
, respectively, and are stored in a memory of the electronic control unit
76
.
When it is judged, at step S
141
, that the real cam phase C does not converge into the target cam phase CM, it is judged, at step S
146
, whether or not the set time elapses with a seventh timer T
7
, and when the time elapses, after a set time is set to the seventh timer T
7
at step S
146
, process proceeds to step S
147
. When the set time has not elapsed with an eighth timer T
8
at step S
147
, the flow proceeds to step S
139
, and the delay time is acquired based on the deviation DM. Incidentally, the significance of both steps S
145
and S
147
is the same as both steps S
136
and S
138
. Furthermore, the set times to be set to the seventh timer T
7
and the eighth timer T
8
are occasionally set from the viewpoint of an accurate oil properties detection.
When the set time of the sixth timer T
6
is not up at step S
145
, and after it is judged, at step S
147
, that the time of the eighth timer T
8
has elapsed and a set time is set to the eighth timer T
8
at step S
148
, the flow proceeds to step S
132
.
Also in a flowchart of the valve operating characteristics by the second connection changing mechanism
31
and the changing routine of both the maps of fuel injection quantity and ignition timing as shown in
FIG. 11
, a next routine is also used as a delay time setting routine at respective steps S
49
and S
56
for setting the delay time to be set to respective changing delay timers TM
2
and TH. In the set range of the engine speed Ne at step S
133
in the flowchart of a routine for setting the delay time of the aforesaid first connection changing mechanism
30
, the lowermost value Ne
5
is changed to 4000 rpm and the uppermost value Ne
6
is changed to 6000 rpm, respectively, with the other steps remaining the same.
In this connection, the same routine as that for setting the delay time of the valve characteristics changing mechanism
13
at the suction valves
11
side is used in case of setting the delay time of the valve characteristics changing mechanism
13
at the side of the exhaust valves
12
.
Also in the second embodiment, the same effects as in the first embodiment can be obtained.
According to both the embodiments, an oil pressure changing valve is constituted by oil pressure responsive valves
80
and
81
provided with a spool
83
which is driven by a solenoid valve
85
for opening and closing a pilot oil passage
86
and a pilot pressure, but the spool
83
may be driven by a solenoid without using a solenoid valve
85
and the pilot oil passage
86
, and in the case, an oil pressure switch
88
can be omitted.
According to both the embodiments, at the time of a low-speed rotation of the engine, the one suction valve
11
is substantially stalled to close the valve, and an upheaved portion
17
may be formed by a low-speed cam so that the suction valve
11
is not stalled and an opening and closing drive is made at a small lift quantity and during a slightly opening valve period. In this case, the lift quantity and the opening valve period of the low-speed cam may be the same as the cam for low speed
15
, or may be different therefrom.
According to both the embodiments, the valve phase variable mechanism
50
is provided in the suction cam shaft
6
, but the valve phase variable mechanism
50
may be provided in the exhaust cam shaft
7
instead of the suction cam shaft
6
. Furthermore, a valve system may not be provided with two cam shafts of the suction cam shaft
6
and the exhaust cam shaft
7
, and may be provided with one cam shaft comprising a suction cam and an exhaust cam.
According to both the embodiments, the oil properties are detected from behaviors of the valve phase variable mechanism
50
and the linear solenoid valve
90
, but by use of a sensor for directly detecting the oil properties, the delay time can be set based on the detection results.
Claims
- 1. A control device of an internal combustion engine, comprising;an operational condition detecting means for detecting an operational condition of the internal combustion engine; a valve moving apparatus provided with a first valve control mechanism having a hydraulic valve characteristic changing mechanism for changing valve operation characteristic of at least one of a suction valve and an exhaust valve of said engine, and an oil pressure changing valve for changing pressure of a working oil supplied to said valve characteristic changing mechanism from an oil pressure source; a first valve operation control means for controlling operation of said oil pressure changing valve in accordance with the operational condition detected by said operational condition detecting means; control amount holding means corresponding to said respective valve operation characteristic with hold control amounts to control combustion condition of said engine; a combustion control means operated based on said control amount of said control amount holding means; a working oil property detecting means for detecting property of said working oil; a holding time setting means for setting a delay time between change of oil pressure by said oil pressure changing valve and completion of change of valve operation characteristic by said valve characteristic changing mechanism based on property of said working oil detected by said working oil property detecting means and; changing means for changing said control amount holding means to a control amount holding means corresponding to a changed valve operation characteristic when said delay time elapses after said oil pressure to be supplied to said valve characteristic changing mechanism is changed by said oil pressure changing valve.
- 2. A control device of an internal combustion engine as claimed in claim 1, wherein said valve moving apparatus further comprises a hydraulic valve phase variable mechanism for altering phase of open-close period of at least one of said suction valve and said exhaust valve, and a second valve control mechanism having an oil pressure control valve for controlling pressure of a working oil supplied to said valve phase variable mechanism from said oil pressure source; operation of said oil control valve is controlled by a second valve operation control means in accordance with the operational condition detected by said operational condition detecting means; and said working oil based on behavior of said second valve control mechanism.
- 3. A control device of an internal combustion engine as claimed in claim 2, wherein phase detecting means for detecting phase of at least one of said suction valve and said exhaust valve having phase altered, and phase change speed calculating means for calculating means for calculating changing speed of phase detected by said phase detecting means, are provided; and said working oil property detecting means detects said working oil property based on said changing speed of phase.
- 4. A control device of an internal combustion engine as claimed in claim 2, wherein phase detecting means for detecting phase of at least one of said suction valve and said exhaust valve having phase altered, and target phase setting means for setting a target phase based on an the operational condition detected by said operational condition detecting means are provided; said second valve operation control means controls operation of said oil pressure control valve so that said target phase concurs with said phase detected by said phase detecting means; and said working oil property detecting means detects working oil property based on deviation between said target phase and said phase detected by said phase detecting means.
- 5. A control device of an internal combustion engine as claimed in claim 2, wherein said oil pressure control valve is operated in accordance with an amount of supply electric current which is duty-controlled by said second valve operation control means, and said working oil property detection means detected working oil property based on duty ratio of said amount of supply election current when said valve phase variable mechanism maintains fixed phase by said oil pressure controlled by said oil pressure control valve.
Priority Claims (1)
Number |
Date |
Country |
Kind |
11-133973 |
May 1999 |
JP |
|
US Referenced Citations (5)