Fuel supply system of an internal-combustion engine

Details Fuel supply system of an internal-combustion engine Fuel supply system of an internal-combustion engine

1993-07-07

1994-12-20

Nelli, Raymond A.

Internal-combustion engines

Charge forming device

Fuel flow regulation between the pump and the charge-forming...

123514, 123516, B60K 1501, F02M 6946, F02M 3720

Patent

active

053738292

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND AND SUMMARY OF THE INVENTION

The invention relates to a system for supplying fuel to an internal-combustion engine which is arranged in an engine compartment, a forward-flow fuel pipe, which starts from a fuel tank situated outside the engine compartment and has a pump, leading to the internal-combustion engine, and a pressure regulator being provided which connects a branch pipe branching off the forward flow pipe with a return-flow pipe leading to the fuel tank in order to adjust a desired fuel pressure in the forward-flow pipe.
From the DE 39 14 939 A1, for example, such a system for supplying fuel to an internal-combustion engine is known. In this case, the pressure regulator is arranged close to the internal-combustion engine or close to the fuel injection valves which are fastened to the internal-combustion engine suction system and branch off from the engine-compartment-side end of the forward-flow pipe. Normally, much more fuel flows through the forward-flow fuel line than will finally be required in the internal-combustion engine because the fuel volume flow is determined by the normal constant delivery output of the pump. In this case, the pump delivery output is dimensioned such that a sufficient amount of fuel is available in all possible internal-combustion engine operating points and particularly also in the operating point of the maximal nominal output. In partial-load operating points, a relatively large excess fuel volume flow is therefore available which arrives back in the fuel tank by way of the return-flow pipe. In this case, the pressure regulator adjusts the volume flow arriving in the return-flow pipe in such a manner that a defined fuel pressure exists in the forward-flow pipe. In this case, this excess fuel pressure may be defined either with respect to the ambient pressure or with respect to the pressure conditions in the suction system.
In normal internal-combustion engine operation, as indicated in the above description, a considerable amount of fuel is always transferred by pumping by way of the forward-flow and the return-flow pipe. In this case, this transferred fuel amount always travels through the engine compartment which is warmed up by the waste heat of the internal-combustion engine. This causes not only a heating of the fuel flow that was transferred by pumping but also results in a temperature rise of the whole fuel volume contained in the fuel tank. However, this rise in temperature is undesirable because easily volatile fuel constituents will then tend to evaporate.
It is therefore an object of the invention to provide measures by means of which a heating particularly of the fuel volume situated in the fuel tank by the engine compartment waste heat is largely prevented.
For achieving this object, it is provided that the branch pipe leading from the forward-flow pipe by way of the pressure regulator to the return-flow pipe as well as the pressure regulator are arranged outside the engine compartment. According further to the present invention, the branch pipe and the pressure regulator are arranged close to the fuel tank. In another preferred embodiment, the pressure regulator can be connected with the engine compartment side end of the forward-flow pipe as an alternative to the branch pipe.
According to the invention, the excess fuel flow delivered by the pump no longer travels through the engine compartment but is branched off the forward-flow pipe already outside the engine compartment. Any heating of the fuel flow returning into the fuel tank by the internal-combustion engine is therefore largely excluded. The effect according to the invention can be further increased when the branch pipe and the pressure regulator are arranged near the fuel tank. Preferably, the arrangement according to the invention is situated in a motor vehicle, in which case the internal-combustion engine as well as the engine compartment are housed in the front of the vehicle and the fuel tank is housed in the rear of the vehicle. If the pressure regulator as well as the branch

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