Control apparatus for internal combustion engine

Internal-combustion engines – Poppet valve operating mechanism – With means for varying timing

Reexamination Certificate

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C123S090170

Reexamination Certificate

active

06213070

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a control apparatus for an internal combustion engine equipped with a variable valve timing mechanism. More specifically, the present invention is directed to a control apparatus for controlling a change in valve timing by the variable valve timing mechanism.
2. Description of the Related Art
FIG. 8
schematically shows the arrangement of a conventional control system for an internal combustion engine equipped with a variable valve timing mechanism, as described in Japanese Patent Application Laid-Open No. Hei 6-299876. The conventional control system is an example of a general-purpose system for changing the open/close timing of an intake valve alone.
Now, the conventional internal combustion engine will be explained. In each cylinder
100
(only one cylinder is indicated), a combustion chamber
100
a
is defined by a piston
101
which is moved for reciprocation in the cylinder
100
. An ignition plug
102
is provided in a cylinder head at an upper portion of the combustion chamber
100
a,
with a tip portion thereof being presented into the combustion chamber
100
a.
An intake pipe
103
and an exhaust pipe
104
are connected to each cylinder
100
. The intake pipe
103
conducts intake air to the combustion chamber
100
a.
The exhaust pipe
104
is used to exhaust combustion gases from the combustion chamber
100
a.
An intake valve
117
is provided at an intake port through which the exhaust pipe
104
is opened to the combustion chamber
100
a,
whereas an exhaust valve
118
is provided at an exhaust port through which the exhaust pipe
104
is opened to the combustion chamber
100
a.
A throttle valve
108
is provided in the intake pipe
103
for controlling an amount of intake air which is supplied to the combustion chamber
100
a.
An opening degree of the throttle valve
108
is detected by a throttle sensor
112
mounted on the intake pipe
103
in the vicinity of the throttle valve
108
. Also, within the intake pipe
103
, both a fuel injection valve
105
and a pressure sensor
113
are provided on the downstream side of the throttle valve
108
. The fuel injection valve
105
is to supply or inject fuel to the intake pipe
103
. The pressure sensor
113
is to detect the pressure in the intake pipe
103
. Furthermore, a water temperature sensor
107
for detecting a temperature of engine coolant or cooling water is mounted on the cylinder
100
, and an oxygen sensor
106
for detecting an oxygen concentration in exhausted air is provided on the exhaust pipe
104
.
Both an intake cam shaft
115
and an exhaust cam shaft
119
, by which the respective valves are opened/closed, are arranged above the intake valve
117
and the exhaust valve
118
. An intake-side timing pulley
120
and an exhaust-side timing pulley
119
a
are mounted on the intake cam shaft
115
and the exhaust cam shaft
119
. Both the intake-side timing pulley
120
and the exhaust-side timing pulley
119
a
are operatively coupled via timing belts (not shown) to a crank shaft
116
. The crank shaft
116
is coupled via a piston rod
116
a
to the piston
101
provided in each cylinder
100
. As a result, both the intake cam shaft
115
and the exhaust cam shaft
119
are driven to rotate in synchronization with the rotation of the crank shaft
116
.
An oil pressure actuator (VVT ACT)
114
driven by lubricating oil of the engine is coupled to an end face of the intake cam shaft
115
, and the oil pressure actuator
114
changes open/close timing of the intake valve
117
. In other words, the oil pressure actuator
114
changes the displacement angle of the intake cam shaft
115
with respect to the intake-side timing pulley
120
in order to continuously change the open/close timing of the intake valve
117
.
An oil control valve (OCV)
121
supplies operating oil to the oil pressure actuator
114
, and also adjusts the amount of the operating oil, so that the oil pressure actuator
114
is driven to change the open/close timing of the intake valve
117
.
FIG. 8
represents such a system for changing the valve timing of the intake valve
117
alone. Similarly, a system for changing the open/close timing of the exhaust valve
118
may be provided.
A rotary plate
116
b
having concave/convex portions formed on an outer circumferential portion thereof is fixed to the crank shaft
116
. A crank angle sensor
110
is arranged opposite to the outer circumferential portion and in the vicinity of the rotary plate
116
b
for detecting the concave/convex portion of the outer circmferential portion of the rotary plate
116
b,
so that this sensor
110
may detect a rotational or angular position of the crank shaft
116
(i.e., crank angle position), and the number of revolutions per minute of the engine (hereinafter referred to as “engine rotational number or speed”).
The output signals of various sorts of sensors are inputted into an engine control unit (hereinafter referred to as an “ECU”)
122
. These sensors include the crank angle sensor
110
, the throttle sensor
112
, the pressure sensor
113
, an intake air sensor (not shown), the water temperature sensor
107
, and the like. The ECU
122
detects an operating condition of the engine in response to sensor information, and then controls the ignition plug
102
, the fuel injection valve
105
, the oil control valve
121
and the like in correspondence with the detected engine operating condition.
FIG. 9
is a schematic block diagram showing a basic arrangement of a conventional control apparatus for an internal combustion engine equipped with the above-described variable valve timing mechanism.
As indicated in
FIG. 9
, the conventional control apparatus for the internal combustion engine includes an operating condition detector
1
, a target advance amount setter
2
, an actual advance amount detector
3
, an advance amount deviation calculator
4
, a control amount calculator
5
, a controller
6
, and a variable valve timing mechanism
7
to be discussed later. It should be understood that these elements
1
to
6
functionally indicate the control contents of the ECU
122
, and these control contents may be executed in a software manner by using a microcomputer and the like.
The operating condition detector
1
detects the operating condition of the internal combustion engine from the information of the output signals derived from various sorts of sensors such as the crank angle sensor
110
for detecting the rotational number of the engine, the throttle sensor
112
, the pressure sensor
113
, an intake air sensor (not shown), and the water temperature sensor
107
, and so on.
The target advance amount setter
2
sets an optimum target valve timing under the detected engine operating condition based upon the detection result of the operating condition detector
1
. The target valve timing is previously mapped based upon either the engine rotational number Ne and the charging efficiency Ce, or the engine rotational number Ne and the throttle opening degree. In the case where a predetermined operating condition is satisfied, for example, the engine cooling water temperature becomes higher than or equal to a predetermined temperature (for instance, higher than or equal to 0° C.), the target advance amount setter
2
retrieves the map, and executes an interpolation calculation so as to set an optimum target advance amount “&thgr;b”. To the contrary, when the predetermined operating condition cannot be satisfied, the target advance amount setter
2
fixes the target advance amount &thgr;b to a basic reference position (for example, intake side is fixed to the most retarded angle position, whereas exhaust side is fixed to the most advanced angle position).
The actual advance amount detector
3
detects the actual valve open/close timing (position) based on the output signals derived from the crank angle sensor
110
and the cam angle position detecting sensor
111
by employing the known method.
The advance amount deviation calculator
4
calc

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