EP0771946B1 - Fuel system - Google Patents

Description

The invention relates to a fuel system for a motor vehicle according to the features the preamble of claim 1.

A fuel system for a motor vehicle is already known, in which a Three / two-way valve is used to regulate the fuel circuit. This valve is relatively complex, expensive and requires a relatively large one Installation space.

From EP-A-0 678 664 a generic fuel system is known in which a check valve and a pressure regulator are integrated in one component. In addition the known fuel system has a flow line in which an elastic Element is installed as a print buffer.

The object of the invention is to provide a fuel system for a motor vehicle create, using simple, mechanical components and the one requires little installation space, in particular the new fuel system for the Running loss fuel circuit can be used.

This object is achieved in a generic fuel system for a motor vehicle solved by the features of the characterizing part of claim 1.

The components used have a simple structure and can be in one be integrated into a single unit, this applies in particular to a check valve, a pressure regulator and possibly a filter. Due to the arrangement of these components close to the tank and due to the elasticity present, an impermissibly high pressure is avoided. As a backup, pressure buffers in the form of elastic elements are particularly important built into the pipes.

A particular problem can arise in a fuel system "Reheat" a hot fuel supply system Engine standstill result. With an approximately constant system pressure, the fuel that expands due to the high temperature, Lines between the fuel pump and the pressure regulator is located up to Reaching one The maximum temperature is derived almost without pressure via the pressure regulator in the return. After that, the pressure in the system decreases continuously, which always outgassing very warm fuel. The gas bubbles created in the injection rail then lead to hot start problems.

In one embodiment of the fuel system, the formation of the gas bubbles prevented by a check valve in the flow line during the reheating phase. The pressure in the fuel rail rises during the post-heating phase the system pressure so that there is almost no outgassing of the fuel. The engine-side pressure relief valve ensures good system filling and on the other hand protection against impermissibly high pressures in the post-heating phase reached.

The integration of components such as the pressure regulator, the filter, the check valve, the pressure relief valve and / or the pressure accumulator, in a valve block or another unit reduces the space requirement. This is it is also possible to arrange the valve block or the unit close to the tank. The housing of the valve block or the unit can be made of metal or Plastic. In particular, the design of the housing as an injection molded part has proven to be inexpensive.

The output to the engine-side return line is preferred for the injection rail trained at the highest point. This has the advantage that gas, which is located in the injection bar, completely via the return into the tank can be derived.

In the case of a "flying" mounting of the valve block in the flow and return, this results in a noise reduction. Flying storage is characterized by that additional fasteners are saved and possible resonance noises of the pressure regulator cannot be transferred to the body.

Due to the simple structure of the fuel system, the fuel system is universal can be used, which results in a variant reduction. Raising the Pressure in the injection bar in the post-heating phase of the engine standstill, that the hot start can be controlled from the tank even without flushing with cold fuel is. The fuel system according to the invention has improved operating conditions when using a suction jet pump because the temperature level is reduced in the lines and in the fuel tank, so that less There are gas components in the fuel. In this way, the suction jet pump delivers better so that the performance of the suction jet pump and the fuel pump is reducible. The reduced requirements for conveying capacity and hot conveying enable the use of cost-effective single-stage pumps or flow pumps. Retrofitting of old vehicles is also possible.

By reducing the suction jet pump gurgling noise after Hot start and by using the floating mounting of the valve block in The fuel system according to the invention operates in the supply and return lines quieter than known fuel systems at significantly lower costs. Finally the components used are less sensitive to dirt.

Fig. 1

einen Schaltplan einer ersten Ausführungsform einer Kraftstoffanlage mit einer zusätzlichen motorseitigen Rücklaufleitung,

Fig. 2

eine Schnittdarstellung eines Ventilblocks, bei dem ein motorseitiges Rückschlagventil und ein motorseitiges Druckbegrenzungsventil sowie ein Druckregler integriert ist und

Fig. 3

einen Schaltplan einer bekannten Ausführungsform einer Kraftstoffanlage ohne einen motorseitigen Rücklauf.

Embodiments of the invention are described below by way of example with reference to the drawings. Show:

Fig. 1

1 shows a circuit diagram of a first embodiment of a fuel system with an additional engine-side return line,

Fig. 2

a sectional view of a valve block in which an engine-side check valve and an engine-side pressure relief valve and a pressure regulator is integrated and

Fig. 3

a circuit diagram of a known embodiment of a fuel system without an engine-side return.

Fig. 1 shows a fuel system 1, in which from a fuel tank 2 a fuel pump 3 fuel 4 to an injection rail 5 of a not shown Motors M is funded. The fuel pump 3 is usually operated electrically and is located in a surge pot 6. The fuel tank shown in FIG. 1 2 has two chambers 7a and 7b. The fuel level in the the two chambers are different, as is the case with one on top Triangle is marked.

In the present embodiment, the fuel is supplied by a suction jet pump 8 conveyed from the left chamber 7b into the right chamber 7a. The suction jet pump 8 is by the amount of fuel not required by the engine M, the flows back into the fuel tank 2, driven. For a one-piece fuel tank drops the suction jet pump 8, so that the fuel flowing back flows directly into the fuel tank via a return line 9.

The fuel delivered by the fuel pump 3 from the fuel tank 2 flows via a flow line 10 to a filter 11. The filtered fuel is applied a pressure regulator 12 and then flows through a pressure maintaining or check valve 13. Then the fuel gets into the injection bar 5. The Fuel that is not required by engine M passes through return line 17 or 9 back into the fuel tank 2.

During engine operation, the engine-side pressure relief valve 15 is closed. Only when filling the system and if necessary during the reheating phase when the engine is stopped, the pressure relief valve 15 is activated. The opening pressure of the additional pressure relief valve 15 is higher than that System pressure, but on the other hand lower than the opening pressure of the pump side Pressure relief valve 100. The system filling is significantly faster by an overpressure acting on a vacuum connection of the pressure regulator 12 with simultaneous operation of the fuel pump 3.

Since the opening pressure of the engine-side pressure relief valve 15 is higher as the system pressure is the formation of gas bubbles during the post-heating phase largely prevented. This assumes that the injectors of the Injection strip 5 are tight. The engine-side pressure relief valve 15 protects against impermissibly high pressures in the reheating phase. Reaches the fuel in the Injection bar 5 an impermissibly high pressure, the pressure relief valve 15 opened and the excess fuel can 14 and 9 flow back into the fuel tank 2.

The fuel pump 3 delivers a constant amount of fuel through the supply line 10. By the pressure regulator 12, the amount not required by the engine of fuel via a return line 17 to the return line 9.

An outlet opening 18 is at the highest on the injection bar 5 Place of the injection bar 5 is formed. This ensures that the injection bar 5 gas located completely transported back to the fuel tank 2 can be.

2 shows a valve block 20 into which the engine-side check valve 13 and the engine-side pressure relief valve 15 are integrated. The valve block 20 has a housing 21, which can be made of metal or plastic. In the case 21, a connection opening 22 for the pressure regulator 12 is formed. The housing 21 has an H shape. The direction of flow of the fuel is indicated by arrows in FIG. 2 displayed. In the upper left section 24 of the housing 21, which for Return line 14 leads, the engine-side pressure relief valve 15 is arranged. The check valve 13 is located in the section 23 opposite thereto built-in. Among the sections 23 and 24 designed as lines is one Connecting line 17 is provided, which consists of sections 9 'and 24 Return line 25 with the existing sections 10 and 23 Flow line 26 of the housing 21 connects to one another.

At the outwardly facing ends 27 and 28 of the lines 25 and 26 of the Housing 21 are formed in cross-section conical thickenings, which in Reduce the cross-section of the axial direction outwards. In another embodiment the ends 27 and 28 can have a pine cone-shaped cross section exhibit.

In the connection opening 22, which is formed in the flow line 26 of the housing 21 is, a pipe socket 29 of the pressure regulator 12 is arranged. The pipe socket 29 has a cylindrical section 30 whose diameter is the inside diameter the return line 17 is adapted. On its outer circumference a seal 31, for example an O-ring, is provided. On the cylindrical Section 30 closes another cylindrical section 32 with a larger one Diameter. Is on the outer periphery of the cylindrical portion 32 a seal 33 is also arranged.

In the pressure regulator 12 is a membrane, not shown, or another device provided that above a certain limit pressure, for example between 3 and 4 bar, opens so that the fuel from the supply line 26 through a through hole formed in the cylindrical portions 30 and 32 34 can flow through. The fuel flowing through the passage opening 34 is represented by the essentially horizontal arrow in FIG. 2.

As is apparent from Figures 1 and 2, there is the check valve 13 and Pressure relief valve 15 essentially from a closing element 36, such as a ball, a resilient element 37 and a spring lock 38.

Fig. 3 shows a known embodiment of a fuel system 1 ', in which Difference from the embodiment of Figures 1 and 2, the engine-side pressure relief valve 15 is omitted. Accordingly, the engine side is also missing Return line 14 and the outlet opening 18 on the injection bar 5. Added is an elastic element 39, for example in the form of a pressure accumulator can be trained. Between the intake manifold of the engine M and the Pressure regulator 12, as in FIG. 1, a vacuum line 40 can be provided.

As has been found in tests, a system filling is still empty Lines and units before commissioning even without one Rinsing possible. This is achieved in that the existing elasticity 19 pressure peaks are reduced in the flow line. As security against im Pressures that do not occur during normal operation are one or more elastic elements 39 installed in the feed line 19.

Claims (8)

1. A fuel system for a motor vehicle comprising a fuel tank (2), a fuel pump (3) disposed therein and delivering fuel (4) through a flow pipe (10) and a filter (11) to an injection manifold (5) of an engine (M) and comprising a first return pipe (9) through which fuel (4) not required by the engine (M) flows back into the tank (2), wherein the filtered fuel (4) acts on a pressure regulator (12) which opens above a predetermined limiting pressure, so that the fuel (4) not required can flow through a second return pipe (17) and through the first return pipe (5) to the tank (2) and wherein a non-return valve (13) is connected behind the pressure regulator (12) in the direction towards the engine (M), characterised in that on the engine side a third return pipe (14) is connected to the injection manifold (5) and leads to a pressure-limiting valve (15), and on the opposite outlet side the pressure-limiting valve (15) is connected to the other return lines (9, 17) and the non-return valve (13), the pressure-limiting valve (15) and the pressure regulator (12) are incorporated in a single component (20).
2. A fuel system according to claim 1, characterised in that the filter (11) is additionally incorporated in the component (20).
3. A fuel system according to claim 1 or 2, characterised in that at least one elastic element (39) in the form of a pressure buffer is incorporated in the flow pipe (19).
4. A fuel system according to any of the preceding claims, characterised in that the component (20) is a valve block having a casing (21), the casing (21) comprises a flow pipe (26), a return pipe (25) and a pipe (17) connecting the two pipes (25 and 26), and the non-return valve (13) is incorporated in the flow pipe (26) and the pressure-limiting valve (15) is incorporated in the return pipe (25).
5. A fuel system according to any of the preceding claims, characterised in that the casing (21) of the valve block (20) has a connection (22) for the pressure regulator (12).
6. A fuel system according to any of the preceding claims, characterised in that the pressure for opening the pressure-limiting valve (15) on the engine side is higher than the system pressure but lower than the pressure for opening the pressure-limiting valve (100) on the pump side.
7. A fuel system according to any of the preceding claims, characterised in that the pressure-limiting valve (15) on the engine side is closed during operation of the engine (M) and is opened only when the system is being filled or at an appropriate pressure during the after-heating phase when the engine (M) is out of operation.
8. A fuel system according to any of the preceding claims, characterised in that the valve block (20) is disposed in or on the tank (2).

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