Fuel pump

Details Fuel pump Fuel pump

1998-03-10

1999-10-19

Moulis, Thomas N.

Internal-combustion engines

Charge forming device

With fuel pump

F04B 104, F02M 3704

Patent

active

059671238

DESCRIPTION:

BRIEF SUMMARY
PRIOR ART

The invention is based on a fuel pump for pumping fuel for an internal combustion engine.
In internal combustion engines, the fuel supplied to the engine increasingly has to be delivered to the engine at relatively high pressure. As a result, the drive mechanism used to drive the pump element is subjected to major mechanical forces. Especially in displacement pumps and particularly piston pumps and especially radial piston pumps, the load on the bearing that supports the drive mechanism is relatively great. In piston pumps, the drive mechanism is typically a rotationally supported shaft, and the bearing are severely loaded in the radial direction. Since the fuel has no lubricating property or only an extremely poor lubricating property but conversely can severely damage the bearing, the fuel must be prevented from getting into the region of the bearing. This is especially true when the fuel is gasoline.
The bearing is typically provided with a special lubricant. To prevent the lubricant from escaping from the bearing, a bearing seal is provided. The bearing seal must be adapted to the lubricant. If the fuel gets into the region of the bearing seal, then the fuel can deleteriously affect the properties of the bearing seal, especially when the fuel is gasoline.
In a known fuel pump (German Offenlegungsschrift DE 44 19 927 A1), the drive mechanism is a shaft rotationally supported via two ball bearings. In this fuel pump, external lubrication is provided. In the known fuel pump, lubricant is pressed between the two ball bearings via a lubricant delivery opening. This requires a separation lubricant source for supplying the lubricant. This increases the expense considerably. Moreover, the bearing seal used to seal off the ball bearing comes into contact with the fuel on one side, which shortens the service life of the bearing seal. Since the bearing seal cannot seal absolutely, at least very minimal quantities of fuel can always get into the region of the ball bearings, which impairs their durability.
Fuel must also be prevented from escaping to the outside from the housing between the drive mechanism and the housing. In the known fuel pumps, despite complicated and expensive sealing provisions, this problem has not been solved to satisfaction.


ADVANTAGES OF THE INVENTION

The fuel pump according to the invention for pumping fuel for an internal combustion engine has the advantage over the prior art that the fuel is excellently well separated from the bearing that supports the drive mechanism, which has a favorable effect on the durability of the bearing. An escape of the fuel from the fuel pump housing is advantageously reliably prevented even without complicated sealing provisions.
If the separator means is air, the result is advantageously a structurally simple feasibility of the fuel pump, and the communication of the separation chamber with the air supplied at least indirectly by the engine is especially simple.
For engine operation, air is needed, which is supplied by the engine, so that advantageously without major effort, at least a small portion of this air can be passed through the separation chamber.
If the separation chamber is made to communicate with the air inlet of the engine, this has the advantage that any fuel that might reach the separation chamber can be diverted without difficulty into the engine and combusted harmlessly.
In the air inlet, at least a slight negative pressure prevails at least intermittently, which promotes the aspiration of the fuel or fuel vapor out of the separation chamber.
If the separation chamber is additionally provided with an entrance through which air can get into the separation chamber, then thorough scavenging of the separation chamber with air is advantageously obtained.
Through the throttle restriction between the separation chamber and the air inlet of the engine, the pressure in the separation chamber and the quantity of air flowing through it can advantageously be varied.
The pressure in the separation chamber and the scavenging of the separa

REFERENCES:
patent: 4301777 (1981-11-01), Grundman

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