Valves and valve actuation – Electrically actuated valve – Having element dimensionally responsive to field
Reexamination Certificate
2002-01-24
2003-09-23
Hirsch, Paul J. (Department: 3754)
Valves and valve actuation
Electrically actuated valve
Having element dimensionally responsive to field
C251S057000
Reexamination Certificate
active
06622985
ABSTRACT:
RELATED ART
The invention concerns an injection device having a fluid port, a control valve, a setting element, by way of which a region of a first face of the control valve can be acted upon with force, and a control chamber provided on the side of a second face of the control valve. The invention further concerns a control valve having a valve seat, a first face that faces a compensating chamber, and a second face that faces a control chamber. The invention further concerns a method for injecting fluid, in which a first face of a control valve is acted upon with force by way of the extension of a setting element, a control chamber is discharged by way of a valve seat of the control valve, and an injection nozzle opens.
Devices according to the general class as well as a method according to the general class are known. Solenoid valves or piezoactuators are generally provided as setting elements. While solenoid valves, by themselves, can provide a stroke that is sufficient for control, a power-travel pressure intensification is generally required when piezoactuators are used, which is commonly accomplished hydraulically. The motion of the piezoactuator is transferred to the control valve by way of the hydraulic power-travel pressure intensification, so that the switching state of the control valve changes. As a result, the pressure conditions in a control chamber change, which, finally, opens an injection nozzle.
Injection devices are often constructed in such a way that, in an initial state, a high pressure—in the neighborhood of the pressure of a common-rail system—is present in the control chamber. A characteristic feature of such a common-rail system or storage injection system is the fact that pressure generation and injection are decoupled. The injection pressure is generated independently of the engine speed and rate of injection, and it waits in the “rail” (fuel accumulator) for injection. In current systems, the pressure in the common rail is in the range of between 1000 and 2000 bar, with higher pressures coming into increasing use. To open the injection nozzle, the control chamber is discharged via activation of the control valve, so that a reduced pressure acts upon the valve control piston. As a result, the injection nozzle can open. To close the injection nozzle, the control valve is returned to its initial state, whereby high pressure forms in the control chamber once more. As a result, the injection nozzle closes due to the force that acts on the valve control piston.
Depending on the arrangement of the control valve within the injection device, the speed at which the injection nozzle closes may be slower than desired, and the construction of the injection device may be less than compact. Moreover, considerable forces may be required to actuate the control valve by means of the setting element.
Advantages of the Invention
The invention is based on the injection device according to the general class in that a compensating chamber is provided on the side of the first face of the control valve, that the compensating chamber is partially limited by the first front face of the control valve, and that the compensating chamber communicates with the control chamber. By way of this arrangement, the pressure present in the control chamber—in common-rail systems, this is the rail pressure—is transferred to the compensating chamber. This pressure corresponds to a force that acts on the first face of the control valve. The setting element therefore need only exert a reduced force on the control valve in order to actuate it.
The control valve preferably comprises at least one channel that connects the compensating chamber with the control chamber. The transfer of pressure from the control chamber into the compensating chamber can therefore be carried out by way of a simple action.
In a first state, a valve seat of the control valve preferably seals off the control chamber from a leakage system. High pressure can therefore form in the control chamber, which keeps the injection nozzle in a closed state or moves the injection nozzle into a closed state.
It is an advantage thereby if elastic means are provided that hold the valve seat of the control valve closed. By this means, a defined state of the control valve is ensured when the setting element is retracted.
In a second state, the control valve preferably connects the control chamber with a leakage system. If the control valve is therefore acted upon with force by the setting element and transferred to a second state, the pressure can escape from the control chamber into the leakage system. This makes it possible for the injection nozzle to open.
In a preferred arrangement, the control chamber is connected to the leakage system by way of the channel and a drainage damping valve. As a result of the interplay with the other flow conditions within the system, a drainage damping valve makes it possible to influence the opening time of the injection nozzle. The provision of this drainage damping valve in conjunction with the channel—by way of which the control chamber communicates with the compensating chamber—is particularly economical and space-saving, so that a compact construction of the control valve is encouraged.
The control valve preferably comprises a surface area in the chamber around the valve seat that can be acted upon with force by the pressure generated in the control chamber. By this means, a further force equalization takes place, and the force to be applied by the setting element on the control valve is reduced once more.
It is particularly advantageous thereby if the effective first face of the control valve, together with the effective surface area in the space around the region of the valve seat, basically corresponds to the effective second face. In this context, “effective surface area” refers, in each case, to a surface area that is perpendicular to the direction of movement of the control valve. If the effective second face is acted upon with force by the total pressure in the control chamber, this force is equalized by the sum of forces that act on the first face, on the one hand, and on the surface area in the chamber around the valve seat, on the other. The effective surface area that is available for the force equalization is therefore only reduced around the surface area of the first face upon which the setting element acts. This surface area has a diameter of 1.8 mm, for example, and is extremely small compared to the effective second face. A satisfying force equalization is therefore achieved.
Further advantages of the invention result from the fact that, in a first state of the control valve, and in a second state of the control valve, the fluid port is sealed off from the control chamber. In these states of the control valve, the control chamber is connected to the fluid port only by way of a port damping valve. This makes it possible for pressure reduction to take place by way of the connection of the control chamber with the leakage system.
It is then particularly advantageous if, in a third state of the control valve, a connection is established between the fluid port and the control chamber. When the control valve enters the third switching state, therefore, it becomes possible for the pressure in the control chamber to increase abruptly, which causes the injection nozzle to close particularly rapidly.
The control chamber and the fluid port are preferably sealed off and connected, respectively, by means of a control sleeve that can be moved by the control valve. During the first and second switching states, the control sleeve is located in its control sleeve seat, by way of which the fluid port is sealed off from the control chamber. If the control valve moves into its third switching state, however, the control sleeve is lifted out of its control sleeve seat, and the fluid port and control chamber are suddenly connected. This results in the abrupt increase of pressure in the control chamber, which makes the advantageously rapid closing of the injection nozzle possible.
The setting element
Hirsch Paul J.
Robert & Bosch GmbH
Striker Michael J.
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