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

2001-10-22

2003-02-04

Denion, Thomas (Department: 3748)

Internal-combustion engines

Poppet valve operating mechanism

With means for varying timing

C123S090160, C123S090170, C123S090120, C123S090270, C123S090310, C074S567000, C251S012000

Reexamination Certificate

active

06513468

ABSTRACT:

This application is based on Application No. 2001-137666, filed in Japan on May 8, 2001, the contents of which are hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates in general terms to a valve timing control system for an internal combustion engine for controlling operation timings of intake valves and exhaust valves of the engine in dependence on engine operating states.
2. Description of Related Art
In recent years, the statutory regulations imposed in connection with emission of harmful materials or substances contained in the exhaust gas discharged to the atmosphere from the internal combustion engine mounted on a motor vehicle or automobile become more and more severe from the standpoint of environmental protection. Under the circumstances, there exists a great demand for reducing the emission of harmful materials or substances contained in the exhaust gas of the internal combustion engine.
In general, there have heretofore been known 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) while the other method is directed to the reduction of the harmful components through posttreatment of the engine exhaust gas with the aid of a catalytic converter (hereinafter also referred to simply as the catalyst) installed within the exhaust pipe of the engine at an intermediate portion.
As is well known in the art, in the catalyst such as mentioned above, reaction of rendering the harmful gas components to be harmless is difficult or unable to take place unless the temperature of the catalyst has reached a predetermined value. 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 this conjunction, it is also known that in most of the internal combustion engines known heretofore, cam shafts which plays an essential role in determining the timings for opening and closing the intake or exhaust valves are so arranged as to be rotationally driven by a crank shaft through the medium of timing belts (or timing chains).
Accordingly, the timings for opening and closing the intake or exhaust valves (which timing may also be referred to as the cam angles) are so controlled as to remain constant relative to the crank angle notwithstanding of the fact that the valve timings as required may change in dependence on the operating states of the engine.
However, in recent years, a valve timing control system designed to be capable of changing or modifying the valve timings has been adopted for practical applications with a view to enhancing the fuel-cost performance of the engine while ensuring improvement of the exhaust gas quality.
The valve timing control system of this type is disclosed in, for example, in Japanese Patent Application Laid-Open Publication No. 324613/1997 (JP-A-9-324613).
The valve timing control system disclosed in the above-mentioned publication includes a variable valve timing mechanism (also referred to as the VVT mechanism in short) which is comprised of vanes each disposed rotatably within a housing for changing the phase (or angular position) of the cam shafts which is adapted to drive the intake valves and the exhaust valves. Incidentally, concerning arrangement of the vanes, description will be made later on.
At this juncture, however, it should be mentioned that in the engine starting operation, the vane of the variable valve timing mechanism is held substantially at a mid position (start corresponding position) for controlling or regulating the relative angular displacement of the cam angle relative to the crank angle and releasing the regulation or control after lapse of a predetermined time.
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 of an internal combustion engine.
FIG. 12
is a functional block diagram showing generally and schematically a configuration of a conventional valve timing control system of an internal combustion engine together with several peripheral parts of the engine.
Referring to
FIG. 12
, provided in association with an intake pipe
4
for feeding the air into a combustion chamber(s) defined within the cylinder(s) of the engine
1
are an air cleaner
2
for purifying the intake air, an air flow sensor
3
for measuring the quantity or flow rate of the intake air. Further, installed in the intake pipe
4
are a throttle valve
5
for adjusting or regulating the intake air quantity (i.e., the amount or flow rate of the intake air) to thereby control the output of the engine
1
, an idle speed control valve (also referred to simply as the ISCV in short)
6
for adjusting or regulating the intake air flow which bypasses the throttle valve
5
to thereby effectuate the engine rotation speed (rpm) control in the idling operation mode, and a fuel injector
7
for charging or injecting an amount of fuel which conforms with the intake air quantity.
Additionally, provided internally of the combustion chamber of the engine cylinder
1
is a spark plug
8
for producing a spark discharge for triggering combustion of the air-fuel mixture charged in the combustion chamber defined within the cylinder. To this end, the spark plug
8
is electrically connected to an ignition coil
9
which supplies electric energy of high voltage to the spark plug
8
.
An exhaust pipe
10
is provided for discharging an exhaust gas resulting from the combustion of the air-fuel mixture within the engine cylinder. An O2-sensor
11
and a catalytic converter
12
are disposed in the exhaust pipe
10
. The O2-sensor
11
serves for detecting the content of residual oxygen contained in the exhaust gas.
The catalytic converter or catalyst
12
is constituted by a three-way catalytic converter known by itself is capable of eliminating simultaneously harmful gas components such as HC (hydrocarbon), CO (carbon monoxide) and NOx (nitrogen oxides) contained in the exhaust gas.
A sensor plate
13
designed for detecting the crank angle is mounted on a crank shaft (not shown) so as to corotate therewith. The sensor plate
13
is provided with a projection (not shown) at a predetermined crank angle in the outer periphery thereof.
A crank angle sensor
14
is installed at a position diametrically opposite to the outer periphery of the sensor plate
13
for the purpose of detecting the angular position of the crank shaft in cooperation with the sensor plate
13
. Thus, the crank angle sensor
14
can generate an electric signal indicative of the crank angle, i.e., the crank angle signal, every time the projection of the sensor plate
13
passes by the crank angle sensor
14
. In this way, the rotating position or angular position (crank angle) of the crank shaft can be detected.
The engine
1
is equipped with valves for putting into communication the intake pipe
4
and the exhaust pipe
10
to each other, wherein the timings for driving the intake or exhaust valves are determined by the cam shafts which are rotated at a speed equal to a half of that of the crank shaft, as will be described later on.
Actuators
15
and
16
for changing adjustably the cam phases are designed to change the timings for driving or actuating the intake or exhaust valves, respectively.
More specifically, each of the actuators
15
and
16
is comprised of a retarding hydraulic chamber and an advancing hydraulic chamber partitioned from each other (described later on) for changing or varying the rotational or angular positions (phases) of the cam shafts
15
C and
16
C, respectively, relative to the crank shaft.
Cam angle sensors
17
and
18
are disposed at positions diametrically opposite to the outer periphery of cam an

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