Internal-combustion engines – Poppet valve operating mechanism – Electrical system
Reexamination Certificate
1999-07-19
2001-03-06
Walberg, Teresa (Department: 3742)
Internal-combustion engines
Poppet valve operating mechanism
Electrical system
Reexamination Certificate
active
06196172
ABSTRACT:
BACKGROUND AND SUMMARY OF THE INVENTION
This application claims the priority of German patent documents 198 32 196.1, filed Jul. 17, 1998; 19855 775.2, filed Dec. 3, 1998; and 198 36 297.8, filed Aug. 11, 1998, the disclosures of which are expressly incorporated by reference herein.
The invention relates to a method for controlling the movement of an armature of an electromagnetic actuator, particularly for operating a charge cycle lifting valve of an internal-combustion engine, in which the armature oscillates between two solenoid coils against the force of at least one restoring spring, in response to alternating energizing of the solenoid coils. With an approach of the armature to the first-energized coil, during the so-called capturing operation, the electric voltage which is applied to the coil capturing the armature is reduced. An example of such a technical environment is disclosed in German Patent Document DE 195 30 121 A1.
A preferred use of an electromagnetic actuator of this type is in an electromagnetically operated valve gear of internal-combustion engines. That is, the charge cycle lifting valves of a reciprocating piston internal-combustion engine are operated by such actuators in the desired manner, being opened and closed in an oscillating fashion. In the case of such an electromagnetic valve gear, the lifting valves are moved individually or in groups by way of electromechanical control members (the so-called actuators), and the point in time for the opening and the closing of each lifting valve can be selected in an essentially completely free manner. As a result, the valve timing of the internal-combustion engine can be optimally adapted to the actual operating condition (defined by the rotational speed and the load) as well as to the respective demands with respect to consumption, torque, emissions, comfort and response behavior of a vehicle driven by the internal-combustion engine.
The essential components of a known actuator for operating the lifting valves of an internal-combustion engine include an armature, two solenoids (for holding the armature in the “lifting valve open” and the “lifting valve closed” position) with the pertaining solenoid coils, and restoring springs for the movement of the armature between the “lifting valve open” and “lifting valve closed” positions. For this purpose, reference is also made to the attached
FIG. 1
which illustrates such an actuator with an assigned lifting valve in the two possible end positions of the lifting valve and of the actuator armature. Between the two illustrated conditions or positions of the actuator—lifting valve unit, the course of the armature lift z or of the armature path between the two solenoid coils, and the course of the current flux I in the two solenoid coils are illustrated over the time t corresponding to a known prior art (which is simpler than the initially mentioned German Patent Document DE 195 30 121 A1).
FIG. 1
shows the closing operation of an internal-combustion engine lifting valve
1
which moves in the direction of its valve seat
30
. In a conventional manner, a valve closing spring
2
a
is applied to this lifting valve
1
. The actuator, which as a whole has the reference number
4
, acts upon the stem of the lifting valve
1
—by means of a hydraulic valve compensating element
3
(which however, is not absolutely necessary). In addition to two solenoid coils
4
a
,
4
b
, this actuator
4
consists of a push rod
4
c
which acts upon the stem of the lifting valve
1
and carries an armature
4
d
which is guided to oscillate longitudinally between the solenoid coils
4
a
,
4
b
. A valve opening spring
2
b
is also applied to the end of the push rod
4
c
facing away from the stem of the lifting valve
1
.
This is therefore an oscillatory system for which the valve closing spring
2
a
and the valve opening spring
2
b
form first and second restoring springs, for which therefore in the following the reference number
2
a
,
2
b
will also be used. The left-hand side of
FIG. 1
shows the first end position of this oscillatory system, in which the lifting valve
1
is completely open and the armature
4
d
rests on the lower solenoid coil
4
b
(hereinafter also called an opener coil, since it holds the lifting valve
1
in its open position). The right-hand side of
FIG. 1
shows the second end position of the oscillatory system in which the lifting valve
1
is completely closed and the armature
4
d
rests against the upper solenoid coil
4
a
(hereinafter also called a closer coil, since it holds the lifting valve
1
in its closed position).
In the following, the closing operation of the lifting valve
1
will be briefly described; that is, in
FIG. 1
, the transition from the left-side condition into the right-side condition. In between, the corresponding courses of the electric currents I flowing in the coils
4
a
,
4
b
as well as the lifting course or the path coordinate z of the armature
4
d
are each entered over the time t. With respect to the path constant z, the value z
0
corresponds to a completely open lifting valve
1
(the armature
4
d
resting on the opener coil
4
b
), while in the case of z=z
1
, the armature
4
d
rests against the closer coil
4
a.
Starting from the left-side “lifting valve open” position, the opener coil
4
b
is energized first in order to hold the armature
4
d
in this position against the tensioned valve closing spring
2
a
(=lower first restoring spring
2
a
), and the current I in the coil
4
b
is illustrated by a broken line in the I-t diagram. If the current I of the opener coil
4
b
is now switched off for a desired transition to “lifting valve closed”, the armature
4
d
detaches from this coil
4
b
and the lifting valve
1
is accelerated by the tensioned valve closing spring
2
a
approximately to its center position (upwards). Because of its mass (moment of inertia) it continues to move, and in the process tensions the valve opening spring
2
b
so that the lifting valve
1
(and the armature
4
d
) are braked. Subsequently, the closer coil
4
a
is energized at a suitable point in time. (In the I-t diagram, the current I for the coil
4
a
is illustrated by a solid line.) In this manner, this coil
4
a
captures the armature
4
d
(the so-called capturing operation), and finally holds it in the “lifting valve closed” position illustrated on the right-hand side. After the armature
4
d
has been securely captured by the coil
4
a
, a switching takes place in the latter to a lower holding current level (compared I-t diagram).
The reverse transition from “lifting valve closed” to “lifting valve open” takes place analogously, from the position illustrated on the right-hand side in
FIG. 1
, by switching off the current I in the closer coil
4
a
and a time-shifted switching-on of the current for the opener coil
4
b
. In general, for energizing the coils
4
a
,
4
b
, a sufficient electric voltage is applied to them, while the switching-off of the electric current I is initiated by a reduction of the electric voltage to the “zero” value. The required electric energy for the operation of each actuator
4
is taken either from the electrical system of the vehicle driven by the pertaining internal-combustion engine or is provided by way of a separate energy supply adapted to the valve gear of the internal-combustion engine. In this case, the electric voltage is kept constant by means of the energy supply, and the coil current I of the actuators
4
assigned to the internal-combustion engine lifting valves
1
is controlled by a control apparatus, such that the required forces for the opening, closing and holding of the lifting valve or valves
1
in the respective desired position are obtained.
In the case of the above-explained state of the art, during the so-called capturing operation (in which one of the two coils
4
a
,
4
b
endeavors to capture the armature
4
d
), the coil current I is controlled by the above-mentioned control apparatus or by a control unit, by timing to a constant value whic
Cosfeld Ralf
Reif Konrad
Bayerische Motoren Werke Aktiengesellschaft
Evenson, McKeown, Edwards & Lenahan P.L.L.C.
Patel Vinod D.
Walberg Teresa
LandOfFree
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