DE2242344A1 - FUEL INJECTION NOZZLE FOR COMBUSTION MACHINES - Google Patents

Description

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22423Ai

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Utility model registration

Robert Bosch GmbH H, 7 Stuttgart I ₃ P.O. Box 50

Fuel injector for internal combustion engines

The invention relates to a fuel injection nozzle for internal combustion engines for pre-injection and main injection, with a valve needle that opens against at least one closing spring, in the closing direction after completing the pre-injection stroke an additional force is loaded.

Such pre-injection and main injection nozzles are supposed to produce the strong ignition noise in fast-running diesel engines when idling be dismantled. A smaller amount of fuel is used first injected, which is followed by a larger amount. The injection of the quantities does not have to be separated from one another, instead, a smooth transition can take place.

In known fuel injection nozzles of the type mentioned, two springs are connected in series, one of which

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Robert Bosch GmbH R-IA ^ r

Stuttgart IUJb

for the pilot injection only one comes into effect, and after completion of the pre-injection stroke, the second is switched on. However, the space required is proportionate large and there are constructive difficulties with two springs, the stroke of the valve needle and dB preload adjust these springs.

The invention is based on the object of a fuel injection nozzle of the type mentioned to develop in which the disadvantages mentioned are avoided and in the possible a weak closing spring can be used for a better pressure setting and a smaller pressure drop based on the opening pressure.

This object is achieved according to the invention in that the Additional force is generated by the fuel supplied under pressure to the injection nozzle, which is via an actuating piston acts on the spring side of the valve needle, the acted upon surface acting in the valve needle direction on the actuating piston is smaller than the area on the valve needle acting in the opening direction.

The dimensions of this setting piston are chosen so that an optimal injection process is achieved at all speeds will. By using this setting piston, the in

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Robert Bosch GmbH R. 1 0 3 -6

Stuttgart

Opening direction effective pressure area on the valve needle during of the residual stroke corresponding to the main injection is reduced, so that an adjustable pressure increase for a given spring stiffness until the full nozzle cross-section is released. Is the subject of the invention in a throttle nozzle used, a weaker closing spring can be used and thus a better pressure setting and a smaller pressure drop relative to the opening pressure can be achieved.

According to an advantageous embodiment of the invention, the The actuating piston is arranged coaxially to the valve needle and has a mandrel that transmits power into the spring chamber of the injection nozzle dives. So it is one, consisting essentially of turned parts, which can be manufactured cheaply in production Construction.

According to an additional embodiment of the invention are in the channels leading to the pressure chambers of the actuating piston and valve needle are arranged throttles. Maybe through this too adjustable throttles, an additional adjustment of the injection process to the engine requirements can be achieved.

An embodiment of the subject matter of the invention is shown in the drawing and is explained in more detail below.

According to the greatly simplified representation, it is in a nozzle housing leash nozzle needle 2 is arranged, which controls an injection opening 3

098 11/0059

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Robert Bosch GmbH r. 10 3 5

Stuttgart

and by, a closing spring 4 is loaded. Also provided in the nozzle housing is an actuating piston 5 arranged coaxially to the valve needle, the end face 6 of which dips into a pressure chamber and which has a mandrel 8 on the side facing the valve needle, which dips into the spring chamber 9. When the actuating piston 5 rests against a stop 10 which determines its rest position, a distance s corresponding to the pre-injection stroke is between the mandrel 8 and the nozzle needle 2. The fuel supplied by the fuel injection pump (not shown) via a line 12 passes through channels 13 and 14 at the same time Z ¹ um Pressure chamber 7 and to the pressure chamber 15 of the valve needle. As soon as the valve needle has covered the pre-injection stroke s against the force of the closing spring 4, it strikes the mandrel of the actuating piston 5. This reduces the area 6 of the actuating piston 5 that acts on the valve needle 2 in the opening direction, i.e. the pressure of the fuel supplied must increase accordingly in order to cause the valve needle 2 to open further. This further opening then corresponds to the main injection, in which larger quantities are now injected under greater pressure. The pressure curve can also be influenced by arranging adjustable throttles 16 and 17 in the channels 13 and 14.

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Claims (2)

Bobert Bosch GmbH R. 1 Π τ c Stuttgart · υ j i, Expectations ^ Fuel injection nozzle for internal combustion engines for pre-injection and main injection, with a Y-valve needle which opens against at least one closing spring and which is loaded in the closing direction by an ^{additional force after completing the varinjection stroke, characterized in that the 1} additional force is caused by the pressure of the injection nozzle supplied fuel is generated, which acts via an actuating piston (5) on the spring side of the valve needle (2), whereby the acted upon area (6) on the actuating piston (5) acting in the valve needle direction is smaller than the area on the valve needle (5) acting in the opening direction. 2). 2. Fuel injection nozzle according to claim 1, characterized in that that the actuating piston (5) is arranged coaxially to the valve needle (2) and has a mandrel (8) which is used for power transmission immersed in the spring chamber (9) of the injection nozzle. 3 · Fuel injection nozzle according to claim 1 or 2, characterized in that that in the channels leading to the pressure chambers (7, 15) of the actuating piston (5) and valve needle (2) (13, 14) throttles (16, 17) are arranged. 409811 / 005P Blank page