Control device of an internal combustion engine

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)
Number Name Date Kind
4876995 Otobe et al. Oct 1989
4889085 Yagi et al. Dec 1989
4962732 Inoue et al. Oct 1990
5628286 Kato et al. May 1997
6109225 Ogita et al. Aug 2000