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

2001-08-15

2002-06-04

Lo, Weilun (Department: 3748)

Internal-combustion engines

Poppet valve operating mechanism

With means for varying timing

C123S090170

Reexamination Certificate

active

06397803

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 open/close timings of intake valves and exhaust valves of the engine in dependence on operation states or modes thereof. More particularly, the invention is concerned with a valve timing control system for an internal combustion engine which system is designed for controlling an actuator so that it is fixedly set to a lock-up position by means of a locking mechanism when the engine is started or stopped, for thereby preventing or suppressing generation of noise as well as occurrence of engine stall event to ensure an improved starting performance of the engine.
2. Description of Related Art
In recent years, in the industrial field of internal combustion engines for the motor vehicles and others, there has been proposed and developed for practical applicants a valve timing control system which is designed to variably control the open/close timing for at least one of the intake valve and the exhaust valve in dependence on the engine operation state with a view to enhancing the engine output performance and reducing the exhaust gas while ensuring improvement engine control performance.
In the system of this type, there is provided a hydraulic pressure type actuator(s) for changing positions of a cam shaft(s) relative to a crank shaft of the engine for controllably sustaining an optimum valve timing.
The actuator includes a locking mechanism for locking the actuator at an intermediate or mid position between the positions corresponding to the most advanced timing and the most retarded timing, respectively, upon starting of the engine operation while allowing the valve timing control to be performed in dependence on the operation state of the engine after having been started.
The variable valve timing mechanism (also referred to as the VVT mechanism in short) which includes the actuator mentioned above is further comprised of a vane assembly 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 assembly will be made in detail later on.
At this juncture, it should however be mentioned that in the engine starting operation mode, the vane assembly of the variable valve timing mechanism is held substantially at a mid position (i.e., the position corresponding to the start position) for regulating the relative rotation (or angular displacement) of the cam shaft relative to the crank shaft and releasing the regulation when a predetermined time has lapsed since the start of the engine.
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. 7
of the accompanying drawings is a functional block diagram showing generally and schematically a configuration of a conventional valve timing control system for an internal combustion engine disclosed, for example, in Japanese Patent Application Laid-Open No. 324613/1997 (JP-A-9-324613) and Japanese Patent Application Laid-Open No. 148380/1999 (JP-A-11-148380), etc.
Parenthetically, it is presumed, only by way of example, that the valve timing control system shown in
FIG. 7
is so arranged as to variably control the open/close timings of both the intake valve and the exhaust valve.
Referring to
FIG. 7
, disposed within a cylinder
1
which constitutes a major part of an engine (hereinafter also referred to as the engine cylinder or simply as the engine
1
) is a piston
1
P reciprocatably therein. A crank shaft
13
C serving as an output shaft of the engine is operatively coupled to the piston
1
P.
The intake air supplied through an intake pipe
4
is charged into a combustion chamber defined within the engine cylinder
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
.
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 air cleaner
2
is designed to purify the intake air fed into the combustion chamber within the engine cylinder. The air flow sensor
3
is designed to measure the quantity or flow rate of the intake air at a position upstream of the throttle valve
5
.
The throttle valve
5
is designed to regulate the amount or flow rate of the intake air flowing through the intake pipe
4
for controlling the output power or torque of the engine
1
.
On the other hand, the idle speed control valve
6
is designed to adjust the intake air flow which bypasses the throttle valve
5
when it is closed, to thereby control the engine rotation speed (rpm) in the idling mode of the engine.
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 by making use of electric power of high voltage supplied from the ignition coil
9
.
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.
The engine
1
is equipped with an intake valve V
1
and an exhaust valve V
2
. The timing at which the intake pipe
4
and the exhaust pipe
10
are put into mutual communication are determined by the intake valve V
1
and the exhaust valve V
2
. On the other hand, the timings for driving the respective valves V
1
and V
2
are determined by the cam shafts
15
C and
16
C each of which rotates at a speed equal to a half of that of the crank shaft
13
C.
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 contained in the exhaust gas.
The catalytic converter (or catalyst)
12
is constituted by a three-way catalytic converter known by itself and serves for eliminating simultaneously harmful gas components such as HC (hydrocarbon), CO (carbon monoxide) and NO
x
(nitrogen oxides) contained in the exhaust gas.
A sensor plate
13
designed for detecting the crank angle is mounted on the crank shaft
13
C of the engine 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 of the plate.
A crank angle sensor
14
is installed at a position close to the outer periphery of the sensor
13
and diametrically opposite thereto for detecting the angular position of the crank shaft
13
C in cooperation with the sensor plate
13
. Thus, the crank angle sensor
14
can generate an electric signal indicative of the rotational position of the crank shaft
13
C (i.e., the pulse-like crank angle signal) every time the projection of the sensor plate
13
passes by the crank angle sensor
14
. In this way, the rotational position or angular position (i.e., crank angle) of the crank shaft
13
C can be detected.
Actuators
15
and
16
are provided for the purpose of changing individually and continuously the cam angle phases (intake and exhaust valve timings) of the cam shafts
15
C and
16
C relative to the crank shaft
13
C.
In more concrete, each of the actuators
15
and
16
is comprised of a retarding hydraulic chamber and an advancing hydraulic chamber partitioned from each other, as will be described later on, for changing the rotational or angular positions (phases) of the cam shafts
15
C and
16
C, respectively, relative to the crank shaft
13
C.
Cam angle sensors
17
and
18
are disposed at positions diametrically opposi

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