A fuel supply system for internal combustion engines

p0001The invention relates to a fuel supply system for internal combustion engines according to the preamble of claim 1.

p0002Such systems consist of a fuel pump and a pressure regulator, wherein the pressure regulator is arranged downstream of a distributor strip and allowed to drain excess fuel into the fuel tank.

p0003Here, the fuel pump is operating with a large delivery against the regulated fuel pressure. When prolonged idling and partial load operation of the internal combustion engine is fed back through the engine heat heated fuel in large quantities in the tank, which increased vapor pressure and gas bubbles can occur in sucked by the pump fuel.

p0004From DE-A1-43 32 446 a supply device is known in which an inserted between the fuel pump and fuel rail pressure control is a function of the pump discharge between conductive and non-conductive and thereby the fuel pump is supplied via a control circuit with different electric power when the pump discharge a threshold of the pressure switch is above or below.

p0005This means no fuel return is obviously provided in the tank, but it is to be expected with a greater variation of the pump discharge because of the required hysteresis.

p0006From DE-A1-31 02 983 an apparatus for controlling the fuel supply is known in which a pressure regulator is a switch / resistor is adjusted, the resistance from the backflowing fuel quantity dependent controls the power supply of the fuel pump. In this device occurs an increase in the fuel temperature in the tank and is located a greater pump pressure fluctuation due to the switching hysteresis before.

p0007Proceeding from this, the invention has the object to design a generic fuel supply system such that a reduced pressure fluctuation to the terminal block is present, not by engine heat caused fuel temperature increase occurs and moreover a pump operation with a total of reduced power supply is accessible.

p0008This object is achieved with the system according to the preamble of claim 1 by the features specified in the characterizing part of the claim. Advantageous developments of the invention are disclosed with the features of the subclaims.

p0009A Ausführunsbeispiel the invention is illustrated in the drawing and is described below.

p0010This shows:<dl id="dl0001" compact="compact"><dt><u>Fig. 1</u></dt><dd>a fuel supply system according to the invention,</dd><dt><u>FIG. 2</u></dt><dd>a formation of the pressure switch in FIG. 1.</dd></dl>

p0011Fig. 1 shows schematically an inventive fuel supply system for internal combustion engines, formed of a fuel pump 1 with electrical terminals, which is connected to a fuel tank 2 and promotes via a fuel pressure line 3 to the internal combustion engine. In the course of the pressure line 3, a pressure switch 4 and then a Reduzierdruckregler 5 is arranged, the output line 6 is connected with a distributor strip 7 of the internal combustion engine.

p0012The Reduzierdruckregler 5 is set so that the reducing pressure is less than the regulated by the pressure switch 4 / set pressure.

p0013By using the Reduzierdruckreglers 5 ensures that the outgoing from the pressure switch 4 pressure fluctuations in the fuel pressure line 3 from breaking through into the common rail. 7

p0014Fig. 2 shows a section of the pressure switch of Figure 1. This consists of a micro-switch 8 with electrical terminals and a switch lever 9 is opened by a diaphragm rod 10 in two positions, switch -. Closed, can be adjusted.

p0015The diaphragm rod 10 is connected to a diaphragm 11 which defines a storage chamber membrane 12th These memory diaphragm chamber 12 is connected via a branch 13 with the fuel pressure line 3, wherein upstream of the branch 13 a check valve 14 is disposed in the fuel pressure line 3rd The aided by the fuel pump 1 fuel passes through the check valve 14 to the Reduzierdruckregler 5 and at the same time in the memory diaphragm chamber 12th

p0016From adjustment of the diaphragm 11 against the force of a spring 15, a higher pressure than the regulated by Reduzierdruckregler 5 so that is present at the PDU 7 standing under working pressure fuel prevails in the fuel pressure line. 3

p0017With filled storage membrane chamber 12, the diaphragm rod 10 adjusted with a stop surface 16 the switch lever 9 "open switch" in the position whereby the power supply is interrupted, if necessary via an amplifier circuit to the fuel pump. 1 This interruption is maintained until the storage membrane chamber 12 is nearly depleted and the diaphragm rod has pushed 10 the switch lever 9 "closed switch" with another stop surface 17 in the position. Thus, the process can repeat.

p0018The check valve 14 prevents Brennstoffrückfluß about the disconnected Brennstoffpunpe 1. It goes without saying that each line of the fuel pressure line may be secured 3 via pressure relief valves can be therefore omitted a relevant representation. The distance between the two abutment surfaces of the diaphragm rod determined in conjunction with the diaphragm adjustment the switching hysteresis. It may be advantageous that the Reduzierdruckregler 5 is subjected to the intake pressure of the internal combustion engine. For this purpose a connection lead 18 is provided.

p0019It may be advantageous if it is provided that the storage volume is 12 when the internal combustion engine is closed by a fuel cut 19, which is arranged in the branch 13 and opens at initiation of the internal combustion engine. This measure is for the safety in case of accidents, reduced fuel discharge, and prevents fuel supply when the internal combustion engine from the storage volume 12 for rail 7 and the injectors, not shown, so that uncontrolled entry of fuel into the combustion chambers, z. B. with leaking valves excluded is (water hammer).

p0020Disconnecting the fuel pump in the phases with filled memory diaphragm chamber 12 resulting in no-load and part-load operation of the internal combustion engine considerable fuel savings over the phases in which the fuel pump with the greatest capacity must work against pressure. The delivery rate of the fuel pump is matched to the consumption of the internal combustion engine.

p0021Here, the poor efficiency of the electric motor of the fuel pump and the power-generating generator plays a considerable role. The switch may alternatively consist of a potentiometer, in which case a voltage-dependent switching device is provided, which switches the power supply to the internal combustion engine at a low voltage to the potentiometer and off or vice versa at high voltage.

p0022It is understood that the membrane of the present embodiment can also be replaced by a piston.