Valve timing control system for internal combustion engine

Details Valve timing control system for internal combustion engine Valve timing control system for internal combustion engine

2001-07-26

2003-02-18

Denion, Thomas (Department: 3748)

Internal-combustion engines

Poppet valve operating mechanism

With means for varying timing

C123S090150, C123S090170

Reexamination Certificate

active

06520131

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a valve timing control apparatus or system for an internal combustion engine which system is designed for controlling operation timings of intake valves and exhaust valves of the engine in dependence on the engine operation states or modes. More particularly, the present invention is concerned with a valve timing control system for an internal combustion engine which system is designed for accelerating or promoting temperature rise of a catalytic converter disposed in an exhaust pipe of the engine in a cold-state idling operation mode while learning a reference (or standard) cam angle for preventing or suppressing occurrence of changes in the engine rotation speed (rpm) as well as engine stall event by stabilizing the engine control performance in a warm-state idling operation mode and ensuring a significant reduction of harmful components contained in the exhaust gas discharged from the engine.
2. Description of Related Art
In recent years, in the industrial field of internal combustion engines for the motor vehicles and others, the statutory regulations imposed on the emission of harmful substances or components contained in the exhaust gas discharged to the atmosphere from the engine mounted on a motor vehicle, automobile or the like become more and more severe from the standpoint of the protection of environment. Under the circumstances, there exists a great demand for reducing the emission of harmful substances or components contained in the exhaust gas discharged from the internal combustion engine.
In general, there have heretofore been adopted two sorts of methods of reducing the harmful exhaust gas components. One method is directed to reduction of the harmful gas directly discharged from the internal combustion engine (hereinafter also referred to simply as the engine). The other method is directed to the reduction of the harmful components through posttreatment of the engine exhaust gas by means of a catalytic converter (hereinafter also referred to simply as the catalyst) installed within an exhaust pipe of the engine at an intermediate location thereof.
As is well known in the art, in the catalytic converter such as mentioned above, reaction of making the harmful gas components be harmless is difficult to take place or rendered impossible unless the temperature of the catalyst has reached a predetermined level. Consequently, it is an important requirement to increase or rise speedily the temperature of the catalyst even when the internal combustion engine is, for example, in the course of starting operation in the cold state (i.e., in the state of low temperature).
In recent years, in an effort to enhance the engine output power while reducing the harmful exhaust gases and improving the fuel-cost performance, there has been developed and increasingly adopted a valve timing control system which is capable of changing or altering the valve timings for intake/exhaust valves of engine cylinders in dependence on the operating states of the engine.
In more concrete, in the conventional valve timing control system known heretofore, an actuator means is provided for changing or modifying the relative angular position (relative phase) of cam shafts relative to the crank shaft of the engine, wherein reference or standard position of the actuator means is stored by detecting the angular position of the crank shaft and the relative positions or phases of the cam shafts relative to the cam shaft to thereby control the relative position(s) or phase(s) of the cam shaft(s) in dependence on the engine operating states.
Further, a locking mechanism is provided in association with the actuator means, which mechanism is designed to operate at an intermediate or mid position between the most advanced angular position and the most retarded angular position so that the actuator means can engage with the locking mechanism upon starting of the engine operation while allowing the valve timing control to be carried out in dependence on the operating state of the engine after it has been started.
More specifically, an electronic control unit (hereinafter also referred to as the ECU in short) is provided which serves as a control means and is so designed as to detect the rotational phase or position (angular position) of the cam shaft for controlling the valve timing to thereby learn phase difference relative to the reference or standard rotational position of the cam shaft while regulating mechanically the tendency of the rotational phase to vary.
The valve timing control system mentioned above includes a variable valve timing mechanism (also referred to as the VVT mechanism in short) which is comprised of a vane disposed rotatably within a housing for changing the phase or angular position of the cam shaft which drives the intake valve or the exhaust valve. In this conjunction, description concerning the vane arrangement will be made in detail later on.
At this juncture, it should however be mentioned that in the engine starting operation mode, the vane of the variable valve timing mechanism is held substantially at a mid position (start corresponding position) for regulating the relative rotation or angular displacement of the cam shaft relative to the crank shaft and releasing the regulation upon lapse of a predetermined time after the start of engine operation.
The valve timing control system of this type is disclosed, for example, in Japanese Patent Application Laid-open Publication No. 324613/1997 (JP-A-9-324613).
For having better understanding of the concept underlying the present invention, description will first be made in some detail of a hitherto known or conventional valve timing control system for an internal combustion engine.
FIG. 6
is a functional block diagram showing generally and schematically a configuration of a conventional valve timing control system for an internal combustion engine disclosed in the above-mentioned publication together with several peripheral constituent parts of the engine.
Referring to
FIG. 6
, the intake air taken in through an intake pipe
4
is charged into a combustion chamber(s) defined within the cylinder(s) of the engine
1
by way of an air cleaner
2
. An air-flow sensor
3
is disposed in the intake pipe
4
at a position downstream of the air cleaner
2
.
The air cleaner
2
is designed to purify the intake air fed into the combustion chamber(s) defined within the engine cylinder(s). The air flow sensor
3
is designed to measure the quantity or flow rate of the intake air.
Further, installed in the intake pipe
4
are a throttle valve
5
, an idle speed control valve (also referred to simply as the ISCV in short)
6
and a fuel injector
7
.
The throttle valve
5
is designed to adjust or regulate the intake air quantity (i.e., the amount or flow rate of the intake air) flowing through the intake pipe
4
for thereby controlling the output power or torque of the engine
1
. The idle speed control valve
6
is designed to adjust or regulate the intake air flow which bypasses the throttle valve
5
to thereby effectuate the control of the engine rotation speed (rpm) in the idle operation state. Further, the fuel injector
7
is designed to inject into the intake pipe
4
an amount of fuel which conforms to the flow rate of the intake air.
Additionally, provided internally of the combustion chamber of the engine cylinder
1
is a spark plug
8
designed to produce a spark discharge for triggering combustion of the air-fuel mixture charged in the combustion chamber defined within the cylinder. The spark plug
8
is electrically connected to an ignition coil
9
which supplies electric power of high voltage to the spark plug
8
.
An exhaust pipe
10
is provided for discharging an exhaust gas which results from the combustion of the air-fuel mixture within the engine cylinder. An O
2
-sensor
11
and a catalytic converter
12
are disposed in the exhaust pipe
10
. The O
2
-sensor
11
serves for detecting the content of residual oxygen conta

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