Valves and valve actuation – Electrically actuated valve – Including solenoid
Reexamination Certificate
1999-12-09
2001-08-28
Kaufman, Joseph A. (Department: 3754)
Valves and valve actuation
Electrically actuated valve
Including solenoid
C251S129210
Reexamination Certificate
active
06279873
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a fuel injection valve.
BACKGROUND INFORMATION
A fuel injection valve that can be actuated electromagnetically, wherein an armature works in conjunction with a magnet coil that can be electrically energized so as to cause electromagnetic actuation, and the lift of the armature is transferred to a valve closing element via a valve needle, is described in German Published Patent Application No. 33 14 899. The valve closing element interacts with a valve seat. The armature is not rigidly attached to the valve needle, but rather is arranged so that it can be moved axially relative to the valve needle. A first return spring acts upon the valve needle in the direction of closing and therefore keeps the fuel injection valve closed when no current is being applied to the magnet coil and the magnet coil is thus in its nonenergized state. A second return spring acts upon the armature in the direction of lift in such a way that in its inoperative position the armature is in contact with a first stop surface arranged on the valve needle. When the magnet coil is energized, the armature is pulled in the direction of lift and carries the valve needle with it via the first stop surface. When the current energizing the magnet coil is turned off, the valve needle is accelerated into its closed position by the first return spring and carries the armature with it via the aforementioned stop surface. As soon as the valve closing element impacts the valve seat, the needle valve's closing movement ends abruptly. The armature, which is not rigidly attached to the valve needle, continues to move in the direction opposite to the lift, and this movement is absorbed by the second return spring, i.e., the armature pushes against the second return spring, which has a significantly smaller spring constant than the first return spring. The second return spring once again accelerates the armature in the direction of lift. If the armature impacts the stop surface of the valve needle, the valve closing element, which is attached to the valve needle, is lifted off the valve seat again for a short time and thus opens the fuel injection valve for a short time. Thus the impact dampening described in German Published Patent Application No. 33 14 899 is incomplete. In addition, the disadvantage of a conventional fuel injection valve in which the armature is rigidly attached to the valve needle, and of the fuel injection valve described in German Published Patent Application No. 33 14 899, is that the opening lift of the valve needle takes effect as soon as the magnetic force applied to the armature by the magnet coil exceeds the sum of the forces in the direction of closing, i.e., the closing force of the spring and the hydraulic forces of the fuel, which is under pressure. This is a disadvantage in that when the current energizing the magnet coil is turned on the magnetic force does not immediately reach its final value due to the self-induction of the magnet coil and the eddy currents that arise. The valve needle and the valve closing element are therefore accelerated by a reduced force when the opening lift begins. As a result, the opening time is unsatisfactory for certain applications.
In this connection, U.S. Pat. No. 5,299,776 proposes that the armature not be rigidly attached to the valve needle but rather that a certain amount of axial motion tolerance between the armature and the valve needle be provided. However, in this fuel injection valve, the axial position of the armature in the inoperative position is not defined, and thus with the fuel injection valve described in this patent the response time when the energizing current is turned on is undefined.
SUMMARY OF THE INVENTION
By contrast, the fuel injection valve according to the present invention has the advantage that the fuel injection valve is impact dampened in a satisfactory manner, and in addition the opening time is extremely short.
Because, when the fuel injection valve is in the inoperative position, the second return spring holds the armature in contact not with the first stop surface arranged on the valve needle but rather with a second stationary stop surface located at a distance from the valve needle's first stop surface, the armature is not accelerated again in the direction of lift by the second return spring when the fuel injection valve closes. When the fuel injection valve closes, initially the valve needle stops moving abruptly when the valve closing element comes into contact with the valve seat when accelerated by the first return spring. The armature continues moving in the direction of closing, i.e., in the direction opposite to the direction of lift, in the fuel injection valve according to the present invention too, until it reaches the second stop surface. If the armature bounces back from the second stop surface, it is accelerated again in the direction opposite to the lift by the second return spring, and this keeps the armature from reaching the valve needle's first stop surface and thereby carrying the valve needle with it in the direction of opening. The second return spring ensures that a distance is maintained between the armature and the first stop surface arranged on the valve needle until the armature is once again accelerated in the direction of lift by the magnet coil when the next current pulse is applied to energize the magnet coil.
A further advantage of the fuel injection valve according to the present invention is that the armature is first preaccelerated before it reaches the first stop surface provided on the valve needle, i.e., before it carries the valve needle with it. As a result the armature achieves impetus before it carries the valve needle with it, and transfers it to the valve needle. By contrast with a fuel injection valve in which the armature is rigidly attached to the valve needle or one in which the armature is movable relative to the valve needle but is in contact with the valve needle's stop surface when in the inoperative position, the valve according to the present invention ensures that the opening time is considerably shorter, which means the fuel can be metered more precisely. As a result of a further effect that shortens the opening time, initially a reduced magnetic force is applied to the armature when the current pulse that energizes the magnet coil is turned on, due to the self-induction of the magnet coil and the eddy currents created by the magnet coil. Provided suitable distance is chosen between the second stop surface on which the armature rests in the inoperative position and the first stop surface that ensures that the armature carries the valve needle with it, when the armature impacts the valve needle's first stop surface so much time has elapsed that the magnetic force has reached its final constant value. As a result of the armature's preassigned “flight time,” a delay may be achieved that significantly shortens the fuel injection valve's subsequent opening time.
Preferably a flange, preferably in the shape of a stepped cylinder, is provided on the valve needle. The flange and the valve needle may be a single piece, e.g., this may be achieved via pressure forming. Alternatively, the flange may be a separate component attached to the valve needle via welding, soldering or a similar method. If the flange is designed as a stepped cylinder, preferably a first shoulder serves as the first stop surface for the armature, while the second spring rests against a second shoulder of the stepped cylinder. The first return spring may rest against a face of the stepped cylinder that faces away from the second return spring. Thus the flange in the form of a stepped cylinder simultaneously fulfils several of the key functions of the present invention.
The second stop surface and a face of the armature opposite the second stop surface are preferably flat. The space between the armature and the second stop surface is preferably connected to a fuel channel through which the fuel is conveyed from a f
Eichendorf Andreas
Norgauer Rainer
Pilgram Guido
Sebastian Thomas
Bastianelli John
Kaufman Joseph A.
Kenyon & Kenyon
Robert & Bosch GmbH
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