Fluid sprinkling – spraying – and diffusing – With system fluid relief or return to supply
Reexamination Certificate
2002-02-11
2002-12-17
Evans, Robin O. (Department: 3752)
Fluid sprinkling, spraying, and diffusing
With system fluid relief or return to supply
C239S088000, C239S090000, C239S092000, C239S096000, C239S584000, C239S585100, C239S585200, C239S586000
Reexamination Certificate
active
06494383
ABSTRACT:
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
The invention relates to a control valve configuration for use in a fuel injector for an internal combustion engine. Configurations of this generic type are disclosed, for example, in U.S. Pat. Nos. 5,460,329 and 5,407,131.
In the case of the control valve configuration according to U.S. Pat. No. 5,460,329, fuel passes as a control fluid through an electromagnetically actuable control valve, which is configured as a slide valve, to a pressure intensifier in the injector. Via the electromagnetic activation, at defined times or crank angles of the internal combustion engine the fuel to be injected is placed under high pressure by the pressure intensifier. The fuel which is placed under high pressure then causes, in the conventional manner, the valve needle on the nozzle of the injector to lift off from its seat and to open up the path for the fuel to the nozzle opening, in order to inject the fuel into the combustion chamber of the engine.
Another type of control valve for a fuel injector that operates with a cam-operated pressure-intensifying piston, is described in U.S. Pat. No. 5,407,131. The control valve here is a seat valve that is normally, i.e. in the rest state, open and which can be closed with the aid of a solenoid. In the open state, the fuel delivered from the tank by a lowpressure fuel pump flows back through the control valve to the tank. The fuel injection into the combustion chamber of a diesel engine is initiated by energizing the solenoid, the magnetic force of which brings the seat valve into the closed operating state. The fuel in the injector, which is now no longer able to flow away, is placed under pressure as a consequence of the cam-actuated piston of the pressure intensifier. When the pressure has reached the defined nozzle-needle opening pressure, the injection starts. The injection is ended by deenergizing the solenoid, whereupon the seat valve is re-opened, so that the fuel can flow away again and the pressure in the injector falls.
Leakage and losses which arise due to leaking and as a consequence of the seepage form a problem which generally occurs in the case of control valve configurations for fuel injection and in particular also in the case of the known configurations dealt with above. The sealing function is restricted both in the case of the slide valves and in the case of the seat valves. Slide valves are only inadequately sealed over the sealing gap, and in the case of seat valves, the sealing function is undertaken only in one direction by the seat. Also, relatively long-lasting seepages, for example by keeping open a valve for the control fluid during the rest state, as in the case of the configuration according to U.S. Pat. No. 5,407,131 mentioned above, are to be evaluated as a loss.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a control valve configuration for use in a fuel injector for internal combustion engines which overcomes the above-mentioned disadvantages of the prior art devices of this general type, in which losses occurring during use are reduced.
With the foregoing and other objects in view there is provided, in accordance with the invention, a control valve configuration for use in a fuel injector for an internal combustion engine. The control valve configuration contains a housing having a valve chamber, a valve inlet for a fluid which is under pressure, and a valve outlet for hydraulically controlling an injection process at a nozzle of the fuel injector. The valve chamber has a first section, a second section, and a return opening. The housing further has a chamber wall defining a rear of the valve chamber and a seat defining a first part of a seat valve disposed in the first section. An actuating device is disposed in the housing. A valve body is disposed in the valve chamber, and the valve body can be displaced axially by the actuating device. Depending on a position of the valve body, the valve body produces or blocks a fluidic connection between the valve inlet and the valve outlet. The valve body has a first valve section forming a second part of the seat valve disposed between the valve inlet and the valve outlet in the first section of the valve chamber. The seat valve is closed in a rest position of the valve body and is opened in a working position of the valve body. The valve body has a second valve section rigidly connected to the first valve section. The second section of the valve chamber and the second valve section form a slide valve which, in the rest position of the valve body produces a fluidic connection between the valve outlet and the return opening and blocks a fluidic connection between the seat valve and the valve outlet. The slide valve closes the return opening and then starts to produce a fluidic connection between the seat valve and the valve outlet only after the valve body leaves the rest position. The first section of the valve chamber leads through the seat of the seat valve in a direction of flow into the second section of the valve chamber.
Accordingly, the valve body that can be displaced axially in the valve chamber by the actuating device has two rigidly connected sections. A first section of the valve body forms a seat valve between the valve inlet and valve outlet in a first section of the valve chamber, the seat valve being closed in a rest position of the valve body and being opened in a working position of the valve body. A second section of the valve body and a second section of the valve chamber form a slide valve which, in the rest position of the valve body, produces a fluidic connection between the valve outlet and a return opening and blocks the fluidic connection between the seat valve and the valve outlet, and which closes the return opening and then starts to produce a fluidic connection between the seat valve and the valve outlet only after it leaves the rest position.
The control valve configuration according to the invention therefore forms two individual valves which are connected in series and one of which is configured as a seat valve and the other of which is configured as a slide valve. Since, in the rest position of the valve body, the outlet of the valve configuration is cut off from the inlet pressure by the closed seat valve and additionally by the slide valve and is connected to the return opening, the outlet is kept unpressurized in this phase without control fluid flowing as wastage through the configuration. In addition, the leakage losses in this phase remain low as a consequence of the cumulative sealing actions of the seat valve and slide valve (connected one behind the other). Since the seat valve naturally begins to open immediately the valve body leaves the rest position, the space between the valve and the slide valve can already be filled with the inlet pressure before the slide valve, after obstructing the return opening, opens up the path to the outlet, with the result that the pressurization of the outlet takes place abruptly.
The outlet of the control valve configuration according to the invention is therefore particularly well-suited for a hydraulic control of the injection process, in which the injection phase is initiated by transfer of the valve body into the working position and the injection interval is determined by the rest position of the valve body.
In the case of a preferred embodiment, the first section of the valve body is a control piston which slides in a tight-fitting manner in the first section of the valve chamber and on the front side of which, which faces the seat valve, an annular active surface which is exposed to the valve inlet pressure is formed. A control space behind a rear active surface of the control piston is connected to the valve inlet via a feed restrictor and to a return connection via a discharge restrictor that is to be opened by the actuating device. In this connection, flow resistances of the restrictors and a proportion in size between the annular active surface and the rear active surface are dimensioned in such a
Evans Robin O.
Greenberg Laurence A.
Locher Ralph E.
Siemens Aktiengesellschaft
Stemer Werner H.
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