Internal-combustion engines – Poppet valve operating mechanism – Electrical system
Reexamination Certificate
2000-12-18
2002-04-30
Denion, Thomas (Department: 3748)
Internal-combustion engines
Poppet valve operating mechanism
Electrical system
C251S129150, C251S129180
Reexamination Certificate
active
06378473
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of controlling an electromagnetic valve unit for use in internal combustion engines.
2. Description of the Related Art
Heretofore, there have been known electromagnetic valve units for selectively opening and closing intake or exhaust valves in the cylinders of internal combustion engines. A basic structure of such an electromagnetic valve unit is shown in
FIG. 1
of the accompanying drawings.
As shown in
FIG. 1
, the electromagnetic valve unit has a valve head
3
for selectively opening and closing an intake or exhaust port
2
(hereinafter referred to as “intake/exhaust port
2
”) of a combustion chamber
1
of each cylinder of an internal combustion engine. The valve head
3
is mounted on an end of a shank
3
a
, and an armature
4
in the form of an iron disk is attached to the other end of the shank
3
a
. The shank
3
a
is axially reciprocally, i.e., vertically in
FIG. 1
, movable to move the valve head
3
between a closed position, indicated by the imaginary lines, for closing the intake/exhaust port
2
and an open position, indicated by the imaginary lines, for opening the intake/exhaust port
2
.
Some electromagnetic valve units include a drive rod (not shown) held coaxially against the upper end of a valve stem for movement in union with the valve stem, and an armature attached to the drive rod. In such electromagnetic valve units, the valve stem and the drive rod jointly correspond to the shank
3
a
shown in FIG.
1
.
The electromagnetic valve unit shown in
FIG. 1
has electromagnets
5
,
6
positioned respectively above and below the armature
4
and having respective solenoids
5
a
,
6
a
. The electromagnet
5
serves as a valve-closing electromagnet which, when the solenoid
5
a
is energized, generates electromagnetic forces to lift and attract the armature
4
thereby to move the valve head
3
into the closed position. The electromagnet
6
serves as a valve-opening electromagnet which, when the solenoid
6
a
is energized, generates electromagnetic forces to lower and attract the armature
4
thereby to move the valve head
3
into the open position.
The electromagnetic valve unit also has a spring
7
positioned above the armature
4
for normally urging the armature
4
to lower the valve head
3
toward the open position, and a spring
8
positioned below the armature
4
for normally urging the armature
4
to lift the valve head
3
toward the closed position. When the electromagnets
5
,
6
are de-energized, the biasing forces of the springs
7
,
8
are kept in equilibrium to hold the valve head
3
in a neutral position, indicated by the solid lines, between the closed and open positions. Therefore, the springs
7
,
8
jointly serve as a biasing means for biasing the valve head
3
in the neutral position.
For opening the valve head
3
from the closed position in which the armature
4
is attracted to the valve-closing electromagnet
5
under its electromagnetic forces, the solenoid
5
a
of the valve-closing electromagnet
5
is de-energized to release the armature
4
from the valve-closing electromagnet
5
, allowing the valve head
3
to move from the closed position toward the open position under the combined biasing forces of the springs
7
,
8
. On the movement of the valve head
3
from the closed position toward the open position, the solenoid
6
a
of the valve-opening electromagnet
6
are energized to attract the armature
4
until the valve head
3
reaches the open position, whereupon the valve head
3
is maintained in the open position.
For moving the valve head
3
from the open position toward the closed position, the solenoid
6
a
is de-energized to release the armature
4
from the valve-opening electromagnet
6
. Thereafter, the solenoid
5
a
is energized to attract the armature
4
against the valve-closing electromagnet
5
. In this manner, the valve head
3
is displaced from the open position into the closed position, and held in the closed position.
The above cycle of opening and closing the valve head
3
is periodically performed in synchronism with the rotational speed of the internal combustion engine.
In order to introduce intake air into and discharge exhaust gases from the combustion chamber
1
smoothly for efficiently operating the internal combustion engine, it is necessary to open and close the valve head
3
such that the displaced position of the valve head
3
between the closed and open positions changes in a desired time-dependent pattern according to the rotational speed of the internal combustion engine. If the opening and closing action of the valve head
3
suffers a difficulty for some reason, such a faulty situation needs to be recognized properly and the valve head
3
needs to be operated for the purpose of avoiding the trouble.
It has been customary for the electromagnetic valve unit to incorporate a displacement sensor for detecting the displaced position of the valve head
3
, and to control the energization of the valve-closing electromagnet
5
and the valve-opening electromagnet
6
depending on the displaced position of the valve head
3
as detected by the displacement sensor. The displaced position of the valve head
3
is recognized by comparing the output from the displacement sensor with a predetermined threshold.
Output characteristics of the displacement sensor with respect to the displaced position of the valve head
3
tend to vary from displacement sensor to displacement sensor and also tend to change due to aging. For these reasons, when the output from the displacement sensor is compared with a fixed threshold, the displaced position of the valve head
3
as recognized based on the comparison is liable to vary. As a result, it is difficult to control the energization of the valve-closing electromagnet
5
and the valve-opening electromagnet
6
in order to open and close the valve head
3
accurately and reliably irrespectively of individual internal combustion engines or the period in which the individual internal combustion engine has been used. It is also difficult to appropriately recognize a failure of the opening and closing action of the valve head
3
and adequately operate the valve head
3
depending on the recognized opening and closing action thereof.
Even if the output of the displacement sensor is highly accurate, the opening and closing action of the valve head
3
is affected by the friction of various related parts, the combustion pressure in the combustion chamber
1
, different characteristics of the springs
7
,
8
, and their time-dependent changes. Consequently, if the energization of the valve-closing electromagnet
5
and the valve-opening electromagnet
6
is controlled in a fixed pattern depending on the output of the displacement sensor, then it is difficult to control the opening and closing action of the valve head
3
accurately and stably.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a method of controlling an electromagnetic valve unit for use in internal combustion engines by appropriately performing a process of controlling the energization of a valve-closing electromagnet or a valve-opening electromagnet to open and close a valve head while compensating for variations of the output of a displacement sensor and variations of the friction of various related parts, for thereby opening and closing the valve head accurately and stably.
According to an aspect of the present invention, there is provided a method of controlling an electromagnetic valve unit in an internal combustion engine, having a valve head reciprocally movable between an open position for opening an intake or exhaust port of a combustion chamber in the internal combustion engine and a closed position for closing the intake or exhaust port, biasing means for biasing the valve head to a neutral position between the open position and the closed position, a valve-opening electromagnet for displacing the valve head into the open position
Fujimoto Jiro
Nakamura Minoru
Yamaki Toshihiro
Corrigan Jaime
Denion Thomas
Honda Giken Kogyo Kabushiki Kaisha
Lahive & Cockfield LLP
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