Fluid sprinkling – spraying – and diffusing – Unitary injection nozzle and pump or accumulator plunger
Reexamination Certificate
1999-01-21
2001-03-20
Brinson, Patrick (Department: 3752)
Fluid sprinkling, spraying, and diffusing
Unitary injection nozzle and pump or accumulator plunger
C239S533200, C239S533900, C267S177000
Reexamination Certificate
active
06202940
ABSTRACT:
The invention relates to a pump nozzle for injecting fuel into an internal combustion engine, especially a one-cylinder diesel engine, which is provided with a piston foot, a pump cylinder, a pump piston, an intermediate washer and an injection nozzle with compression spring, compression-spring plate and valve needle.
Conventional injection systems comprise an injection pump, whose outlets communicate via pressure lines with a plurality of injection nozzles. The pressure lines have physical characteristics which act to limit power since, under the conditions prevailing in high-pressure injection systems, the fuel can no longer be regarded as a stiff, incompressible fluid, and the processes during injections are governed by laws similar to those of acoustics. For example, the pressure line acts as a “harmful” volume in the system, since it limits the attainable peak pressures, and the dynamics of the pressure line make it difficult to maintain control over the injection processes (after-spurts, cavitation).
Pump nozzles have already been in use for some time to avoid these disadvantages caused by the line. In such a construction, injection pump and injection nozzle constitute a unit. One pump nozzle per cylinder is mounted in the cylinder head and driven either directly via a piston foot or indirectly by the camshaft via rocker arm. Control can be exerted either via a common control rod in the cylinder head, in analogy with an in-line injection pump, or by an alternative low-pressure proportioning pump. However, directly controlled pump nozzles are already known as well. In such a construction, the overflow port, which in the case of in-line injection pumps is controlled with the inclined edge for flow regulation, is operated via a quick-acting high-pressure solenoid valve. The pump nozzle delivers as long as the solenoid valve is closed.
German Patent DE 4127003 A1 discloses an electrically controlled pump nozzle of the class in question for fuel-injection devices in internal combustion machines. The pump nozzle described therein is provided with a pump housing which contains a pump cylinder, in which there is guided a pump piston which defines a pump working chamber and is driven with constant stroke. In the extension of its centerline there is disposed a retaining element on which there is mounted a nozzle body.
This and other known pump-nozzle variants share the feature of large overall length. For this reason, the pump nozzle has been used heretofore mainly in engines with very large dimensions.
German Patent Application DE-AS 1126678 indeed proposes a pump nozzle in which a cup spring is provided as the valve compression spring in order to lessen the area of the injection housing heated by the combustion gases as well as to reduce the housing diameter. This design has the disadvantage, however, that the spring pressure is not adjustable and the use of commercial pump components to lower the costs is ruled out.
The object of the present invention is therefore to provide a pump nozzle which can be manufactured inexpensively, which has a short overall length and which thereby is suitable even for small diesel engines.
This object is achieved according to the invention by the features of claim
1
.
The pump nozzle according to the invention is constructed in such a way that a pump-piston foot is connected to a pump piston, which is accommodated in a pump cylinder. An intermediate washer and a valve needle connected thereto, together with a nozzle body, form the nozzle. Disposed off to the side of the valve-needle axis there is provided a compression spring as the valve-needle-closing spring. Hereby there is achieved a compact structure with very short overall length.
An advantageous further embodiment of the invention provides that the compression spring is disposed beside the pump cylinder. In this case the compression spring can have the form of a helical spring, whose axis runs parallel to the valve-needle axis.
Another further embodiment of the invention provides that the valve needle is subjected via a reversing lever to the spring pressure of the pre-loaded compression spring. Advantageously the reversing lever is provided with a pivot or a lever fulcrum on the intermediate washer, the valve needle and the compression-spring plate.
When opening pressure is reached, the fuel presses on the valve needle, thus lifting it and simultaneously the reversing lever. For this purpose the opening pressure must be sufficiently high that it overcomes and opposes the spring pressure exerted by the compression spring via the reversing lever on the valve needle. The further the valve needle is lifted from its seat in the nozzle, the more the compression spring is compressed. Conversely, when the closing pressure is reached, the valve needle is forced sealingly into the nozzle orifice by the compression spring acting through the reversing lever, and thus the injection nozzle is closed.
Advantageously the intermediate washer is provided with a longitudinal slot to accommodate the reversing lever. Hereby the overall length can be further shortened.
In another advantageous further embodiment of the present invention, a piston lug between piston foot and pump piston and a control sleeve are provided for mechanical regulation of the injection flow. In this case, fuel is proportioned according to the overflow principle with inclined edges, the effective stroke of the pump element being varied by turning it. Inlet ports communicating with the suction chamber of the injection pump are disposed in the pump cylinder.
The control sleeve is advantageously constructed as a profiled sheet-metal sleeve with a control connecting rod. For example, the control sleeve can comprise a polygonal profile, thus giving the piston lug adequate clearance for axial up and down movement, while also providing for turning of the pump piston and thus of the longitudinal slot via the control connecting rod, which is attached by rivet or spot weld. Hereby the need is obviated for an expensive and complex toothed control rack, which engages in a sealing toothed gear mounted on the piston.
Another advantageous embodiment provides that a solenoid valve is disposed on the upstream side for electronic injection control. Thereby injection flow and start of injection can be regulated in simple manner by one component.
Furthermore, it is advantageous for the piston foot to be connected by a driver to a driving element. By attaching the driver on the side of the driving element, such as a driving cam or rocker arm, and by the possibility of connecting the driver with the piston end by simple swiveling of the driver, there is achieved particularly simple mounting of the injection pump on the motor. Once the piston foot with its broadened foot plate has been brought into bearing position on the driving element, the driver is simply swiveled above the foot plate, so that it engages via the rear side of the foot plate and prevents it from being lifted by the driving element during operation of the engine. Hereby the expensive piston springs which are standard in conventional injection pumps can be completely replaced.
Yet another advantageous embodiment of the present invention provides that the compression-spring chamber is constructed as the fuel feed. A cost-saving, compact structure is also achieved by this multiple function.
REFERENCES:
patent: 4650116 (1987-03-01), Prillwitz
patent: 5326034 (1994-07-01), Peters
patent: 1126678 (1962-03-01), None
patent: 4127003 (1993-02-01), None
patent: 2226078 (1990-06-01), None
Brinson Patrick
Helfgott & Karas P.C.
Motorenfabrik Hatz GmbH & Co. KG
Nguyen Dinh Q.
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