EP1262658B1 - Fuel system for supplying fuel for an internal combustion engine - Google Patents

Description

State of the art

The invention relates to a fuel system for supply of fuel for an internal combustion engine, with a Reservoir, with a first fuel pump, the Inlet is connected to the reservoir, with a second fuel pump, the inlet of which Fuel connection with an outlet of the first Fuel pump is connected to at least one Injector, which with an outlet of the second Fuel pump is connected and fuel at least can lead indirectly to a combustion chamber with one Locking device, which a return flow of fuel at least from a portion of the fuel connection prevented back into the reservoir, and with a Leakage line coming from the second fuel pump leads to the reservoir.

Such a fuel system is known from the market see e.g. US-A-5558068. In the known fuel system, an electrically delivers powered fuel pump from a fuel tank Fuel through a fuel line too a high-pressure fuel pump driven by the internal combustion engine. This promotes the fuel under a lot high pressure in a fuel manifold (also: "Rail" called). From there the fuel gets at least an injector, through which the fuel eventually gets into the combustion chamber of the internal combustion engine.

In the known fuel system is used as a high-pressure fuel pump used a 1-cylinder piston pump. about the leakage line becomes leakage fuel which is caused by the gap between the cylinder and piston passes through the high pressure fuel pump to the reservoir recycled. This relieves the piston seal of the used 1-cylinder piston pump. Behind the exit of the electric fuel pump is a check valve present, which is a backflow of fuel through the Prevented fuel pump back into the reservoir.

A fundamental problem with fuel systems is that Supply of the combustion chambers of the internal combustion engine with Fuel during starting. With the known Fuel system, a valve device ensures that the electrically driven one during the starting process Fuel pump closes the fuel with increased feed pressure supplies the injectors. In many cases it is enough this increased feed pressure to the internal combustion engine start in no time. By the increased Feed pressure can cause a gas bubble in the Fuel connection between the electrically powered Fuel pump and that of the internal combustion engine driven fuel pump in many cases like this be compressed that a safe start of the Internal combustion engine is guaranteed.

The present invention has the task of a Fuel system of the type mentioned above to further that the starting and operating behavior of a internal combustion engine equipped with the fuel system gets better at high operating temperatures and that Service life of the fuel system is as long as possible. At the same time, the fuel system should be as simple as possible be constructed.

This task is the beginning of a fuel system mentioned type solved in that in the leakage line a hydraulically operated shut-off valve device which is arranged by the pressure in a section the fuel connection is controlled which is upstream of the locking device.

Advantages of the invention

By providing a shut-off valve device in the Leakage line is achieved that after turning off the Internal combustion engine the increased form in the Fuel connection between the first and second Fuel pump can be maintained. By a The leakage line is blocked after it has been switched off The engine prevents fuel from flowing through the gap between the movable pump element and the Limitation of the pump space of the second fuel pump passes through and flows back to the reservoir. This would cause a gradual decrease in pressure in the Fuel connection upstream from the first Run the fuel pump.

Maintaining pressure prevents that after turning off one is called Internal combustion engine in the connection between the first and the second fuel pump can form gas bubbles. Such gas bubbles occur when the in the Fuel lines between the fuel pumps located fuel due to heat conduction from the Internal combustion engine heated up. However, the pressure is like this is possible with the fuel system according to the invention is, even with an internal combustion engine turned off can maintain the formation of such gas bubbles largely avoided. This improves that Starting behavior of one with the invention Fuel system-equipped internal combustion engine considerably.

The hydraulic actuation of the shut-off valve device is reliable and simple, i.e. inexpensive, realizable. The control of the shut-off valve device by the pressure in that section of the Fuel connection which is upstream of the Locking device is located, allows a quick response of the Shut-off valve device on switching the first fuel pump.

This section occurs when the Fuel pump very quickly to build up pressure from ambient pressure prevailing at rest to normal Operating pressure of the first fuel pump. Conversely, falls the pressure in this section of the fuel connection at Switching off the first fuel pump from the normal one Operating pressure very quickly to ambient pressure, so that the shut-off valve device is also safe in this case and can be switched reliably.

Advantageous developments of the invention are in Subclaims specified.

In a first training it is mentioned that the Shut-off valve device by the pressure at the outlet of the first fuel pump is controlled. Here are the Pressure changes when switching the first on and off Fuel pump is most noticeable. At the The shut-off valve device can switch off the first fuel pump thus be closed very quickly what an undesirable outflow of fuel from the Leakage line and the fuel connection in the Storage container prevented early. The pressure in the Fuel connection can thus be as high as possible Level can be maintained.

For a fuel system with constant admission pressure is that training is particularly preferred in which the Shut-off valve device only when a Control pressure opens, which is in the normal range Operating pressure of the first fuel pump is and a pressure drop indicates a control pressure which below the normal operating pressure of the first Fuel pump is, and if there is a pressure drop to one Control pressure closes, which is below normal Operating pressure of the first fuel pump is.

These apply to fuel systems with variable admission pressure Execution above with the proviso that the opening pressure the shut-off valve device in the range of the minimum Operating pressure of the first fuel pump and Closing pressure below this minimum operating pressure lies.

This ensures that only when the Fuel pump after switching on such a sufficient Performance provides that the start of the Internal combustion engine is possible, the shut-off valve device opened and the pressure in the Leakage line is lowered to ambient pressure. Vice versa it is also ensured that the shut-off valve device immediately after turning off the first Fuel pump is closed.

It is particularly preferred if the shut-off valve device a biasing element, for example a spring, which includes a valve element in the closed Rested position applied.

It is also possible that downstream of the Locking device a pressure relief valve is provided. With this pressure relief valve it has the following Proven: After turning off the hot ones Internal combustion engine, the standstill of the first Fuel pump and the associated closing of the Shut-off valve device could be caused by heating the Fuel and the associated expansion of the Fuel in the fuel connection and the Leakage line to an impermissible pressure increase in this Area come. Such an impermissible increase in pressure will prevented by the pressure relief valve. The Components in the fuel connection and in the Leakage line are thus also in the case of shutdown Internal combustion engine protected against impermissibly high pressures, which increases their lifespan. In addition, too cheaper components designed for lower pressures are used.

An advantageous embodiment provides that a return flow line downstream of the blocking device from the fuel connection to the reservoir branches and the pressure relief valve in the Return flow line is arranged.

It is also possible that between the outlet of the first Fuel pump and the locking device from the Fuel connection a line to the reservoir branches in which a flow restrictor is arranged, and this line with a control connection of the shut-off valve device connected is. With such a choke becomes when the first fuel pump is switched on Establishing a stable pressure in the Fuel connection between the first and second Fuel pump accelerated and relieved. The over the Flow restriction to the outflow of the reservoir Amount of fuel can preferably be used to operate a Suction jet pump for feeding the first fuel pump be used. The one for controlling the shut-off valve device necessary fuel flow falls here not weight.

Alternatively, it is possible that the control connection the shut-off valve device with a degassing connection the first fuel pump is connected. Preferably this solution comes into question if with the Return flow no suction jet pump should be operated. It is then for the efficiency of the first fuel pump advantageous that of the main flow of fuel no tax amount is deducted.

It is also possible that the shut-off valve device is a connected in parallel to the shut-off function Has pressure limiting function. In this case, on a separate pressure relief valve can be dispensed with, what the construction costs for the fuel system according to the invention reduced.

It is also favorable for the construction effort if the shut-off valve device in the area of the storage container, especially in the area of the first fuel pump, is arranged. It is particularly preferred if the first fuel pump and the shut-off valve device Are part of a tank installation unit.

The invention also relates to an internal combustion engine, especially for motor vehicles, with a Fuel system that uses at least one fuel Feeds combustion chamber. It is advantageous if that Fuel system is designed in the above manner.

drawing

Figur 1

ein schematisiertes Blockschaltbild eines Ausführungsbeispiels eines Kraftstoffsystems; und

Figur 2

eine schematisierte Detaildarstellung einer zweiten Kraftstoffpumpe sowie einer Absperr-Ventileinrichtung des Kraftstoffsystems von Figur 1.

An exemplary embodiment of the invention is explained in detail below with reference to the accompanying drawing. The drawing shows:

Figure 1

a schematic block diagram of an embodiment of a fuel system; and

Figure 2

2 shows a schematic detailed illustration of a second fuel pump and a shut-off valve device of the fuel system from FIG. 1.

Description of the embodiment

In Fig. 1, a fuel system as a whole carries that Reference numeral 10. It is part of an internal combustion engine 11 and includes a low pressure region 12 and one High pressure area 14.

The low pressure region 12 comprises a storage container 16, in which fuel 18 is stored. The fuel 18 is from the reservoir 16 by a first Fuel pump 20 promoted. This is about an electric fuel pump powered by a Clock module 22 is driven. The electrical Fuel pump 20 feeds into an via an outlet 23 Low pressure fuel line 24. In this is after the electric fuel pump 20 in the flow direction first seen a check valve 26 and then a Filter 28 arranged.

Seen in the direction of flow before the check valve 26 branches off from the low-pressure fuel line 24 Branch line 30, which to the reservoir 16 returns. In the branch line 30 is one Flow throttle 32 arranged. From the between the Check valve 26 and the filter 28 located area of Low-pressure fuel line 24 branches one more Branch line 34, which also goes to the reservoir 16 returns and in which a pressure relief valve 36 is arranged. The pressure in the downstream of that Check valve 26 located portion of the low pressure fuel line 24 is detected by a pressure sensor 38.

The low pressure fuel line 24 leads to a second one Fuel pump 40. This will not be discussed here illustrated way of the crankshaft of the Internal combustion engine 11 driven. The second Fuel pump 40 is a 1-piston high-pressure pump. Upstream of the high pressure pump 40 are still in the low pressure fuel line 24 Pressure damper 42 and a check valve 44 are arranged.

On the output side, the high pressure pump 40 pumps into a Fuel line 46, which via a check valve 48 leads to a fuel rail 50. This will commonly referred to as "rail". To the fuel rail 50 are in turn several fuel injectors 52 connected which the fuel in a combustion chamber, not shown, of the internal combustion engine Inject 11. The pressure in the fuel rail 50 is detected by a pressure sensor 54.

To overpressure in the fuel rail 50 too avoid which the functionality of the Injector 52 could interfere with the Fuel rail 50, a pressure relief valve 56 provided which is fluidly connected via a line 58 to the Low pressure fuel line 24 is connected. The pressure in the fuel line 46 and the fuel rail 50, that is in the high pressure region 14 of the Fuel system 10, is via a quantity control valve 60 controlled which between the check valve 48 and the high pressure pump 40 located area of Fuel line 46 with between the check valve 44 and the pressure damper 42 located area of Low pressure fuel line 24 connects.

The fuel system 10 also includes a control and Control device 62, which among other things signals from Pressure sensor 54 receives. This is also from the pressure sensor 38 Control and regulating device 62 supplied with signals. On the output side, the control and regulating device 62 is below with the clock module 22 of the first fuel pump 20 and connected to the flow control valve 60.

A leakage line 64 leads from the high pressure pump 40 back to the storage container 16. In the leakage line 64 is a shut-off valve device 66 is present. This has via an open switch position 68 and a closed Switch position 70. In the closed rest position 70 the shut-off valve device 66 by a compression spring 72 brought. In the open switch position 68 Shut-off valve device 66 by a piston 74 brought, which is shown only symbolically in Fig. 1. The piston 74 can communicate with the pressure via a control line 76 are applied, which in the branch line 30th prevails.

The electric fuel pump 20, the check valve 26, the filter 28, the pressure sensor 38, the Pressure relief valve 36, the flow restrictor 32 and the Shut-off valve device 66 are part of one Tank installation unit 75.

The high pressure pump 40 and the shutoff valve device 66 are now explained in detail with reference to FIG. 2:

The high pressure pump 40 is a 1-piston pump. The piston 77 is driven by a cam drive 78 driven. The piston 77 is in a cylinder housing 80 guided. The top of the piston 74 and that Cylinder housing 80 delimit a pump chamber 82. This becomes opposite the cam drive 78 by a gap seal sealed between the piston 74 and the Cylinder housing 80 is formed. Furthermore, one Piston seal 84 fixed to the housing is provided. The Leakage line 64 branches directly from an annular groove 86 Above the piston seal 84. This will in Operation relieves the piston seal 84.

The shut-off valve device 66 comprises a housing 88, in which the piston 74 is guided. At its top in Fig. 2 At the end, the piston 74 carries a head 90, the diameter of which is considerably larger than that of the piston 74. Also the Piston 90 is in a correspondingly wider area of the Valve housing 88 guided tightly. The head 90 is from the Compression spring 72 acts, through which the lower End face of the piston 74 against an annular web 92 is acted upon in a flow space 94 behind formed an inlet 96 of the shut-off valve device 66 is. A radial outlet 97 is located at the flow space 94 provided to which the leading to the reservoir 16 Section of the leakage line 64 is connected.

The housing 88 of the shut-off valve device 66 is after closed at the top by a lid 98, which on a pin on its inside facing head 90 (without reference numerals) through which the compression spring 72 is centered. The shut-off valve device cover 98 66 is with the valve housing 88 by caulking 99 inextricably linked. Below the head 90 is between the Head 90, the piston 74 and the valve housing 88 a further pressure chamber 100 is formed. This is about one radial bore 102 connected to the control line 76. The Compression spring 72 is in a cylindrical recess (without Reference numerals) performed in the top of the head 90. from A flow channel 104 runs along the bottom of the recess through the piston 74 downwards and further radially outwards into the flow space 94.

The fuel system 10 shown in FIGS. 1 and 2 works as follows:

In normal operation of the internal combustion engine 11 Fuel 18 from the reservoir 16 from the electric fuel pump 20 in the low pressure fuel line 24 and on to the high pressure pump 40 promoted. The high pressure pump 40 promotes the electric fuel pump 20 pre-compressed fuel 18 continue with another pressure increase in the Fuel line 46 to the fuel rail 50. The pressure sensor 54 and the quantity control valve 60 are part a closed controlled system, over which the of the High pressure pump 40 in the high pressure area 14 of the Fuel system 10 delivered fuel amount and their Pressure is set.

When the electric fuel pump 20 is turned on the pressure in the low pressure fuel line 24 rises up to the value specified by the control and regulating device 62 on via the pressure sensor 38 and the clock module 22 is settled. When starting hot, the pressure is up to Opening pressure of the pressure relief valve 36 of approximately 6 increased bar. Pressure in the entire operating area Low pressure region 12 between about 1.5 and about 6 bar varies. Also in the branch line 30, in which the Flow throttle 32 is arranged, this pressure prevails. The pressure is thus also via the control line 76 in the Pressure chamber 100 of the shut-off valve device 66 passed.

The pressure area below the head 90 and the compression spring 72 are matched to one another so that when printing just below the minimum operating pressure of 1.5 bar the head 90 and with it the piston 74 against the force of the Compression spring 72 is moved upwards. Thus the Piston 74 from the ring web 92 and gives the way from the Leakage line 64 through the shut-off valve device 66 to the reservoir 16 free.

This makes it possible for fuel to pass through the gap seal between the piston 77 and the Cylinder housing 80 passes through to the annular groove 86, via the flow space 94, the radial outlet 97 and the Flow the leakage line 66 back to the reservoir 16 can. This leads to a noticeable relief of the Piston seal 84.

When the engine is turned off, the electric fuel pump 20 turned off. By doing Area of the low pressure fuel line 24, which upstream of the check valve 26 falls thus the pressure on the prevailing in the reservoir 16 Ambient pressure. The same applies to the branch line 30, the control line 76 and the pressure chamber 100. By the Compression spring 72 can now head 90 and piston 74 again be pressed down until the piston 74 on the ring land 92 is present and the connection of the leakage line 64 to Storage container 16 interrupts.

As mentioned above, they are below the Head 90 lying pressure surface and the compression spring 72 so coordinated that the closing of the shut-off valve device 66 already scarce at one print takes place below 1.5 bar. Is the shut-off valve device 66 closed, but is the entire Area of the leakage line 64 between the shut-off valve device 66 and the high pressure pump 40 and the Area of low pressure fuel line between the High pressure pump 40 and the check valve 26 from the Environment completed. The remains in this area System pressure at the time of parking also at parked engine received.

After turning off the engine it may be due to from heat conduction to heating the low pressure fuel line 24 come. This will also Fuel 18 in the low pressure fuel line 24 warms and expands. This just results in that described closed area of the low-pressure fuel line 24 to a pressure increase. To one Damage to components of the low pressure fuel line 24 or total of the low pressure range To avoid 12, the pressure relief valve 36 is on the Branch line 34 with this area of the low-pressure fuel line 24 connected.

Possibly. can the compression spring 72 and located within the Ring web 72 located end face of the piston 74 so be coordinated with one another that if the Pressure in the leakage line 64 to a value above a limit value of the piston 74 lifts off from the ring web 92 The corresponding pressure level is preferably above the pressure levels predetermined by the pressure relief valve 36. In In this case, the shut-off valve device 66 an additional safety pressure limiting device for the low pressure fuel line 24 and the Leakage line 64 created.

Via the flow channel 104 is the space in which the Compression spring 72 is arranged with the radial outlet 97 the shut-off valve device 66, which in turn leads to the reservoir 16. Because there usually approximately ambient pressure prevails, is caused by this Flow channel 104 avoided in the room in which the compression spring 72 is arranged, the force ratio can build up disturbing pressure.

In an embodiment, not shown, the Control line from the shut-off valve device is not closed a branch line, but to one on the electrical Fuel pump existing degassing connection. This solution is preferably used if the Return flow no suction jet pump is operated. This has the advantage of being the bulk of the fuel no tax amount is deducted, reducing the efficiency of the electric fuel pump improved.

Claims (13)

1. Fuel system (10) for the delivery of fuel (18) for an internal combustion engine, with a tank (16), with a first fuel pump (20), the inlet of which is connected to the tank (16), with a second fuel pump (40), the inlet of which is connected to an outlet (23) of the first fuel pump (20) via a fuel connection (24), with at least one injection device (52) which is connected to an outlet of the second fuel pump (40) and can supply fuel (18) at least indirectly to a combustion space, with a blocking device (26) which prevents a backflow of fuel (18) at least from a portion of the fuel connection (24) back into the tank (16), and with a leakage line (64) which leads from the second fuel pump (40) to the tank (16), characterized in that the leakage line (64) has arranged in it a hydraulically actuated shut-off valve device (66) which is controlled by the pressure in a portion of the fuel connection (24) which lies upstream of the blocking device (26).
2. Fuel system (10) according to Claim 1, characterized in that the shut-off valve device (66) is controlled by the pressure at the outlet of the first fuel pump (20).
3. Fuel system (10) according to either one of Claims 1 or 2, characterized in that the shut-off valve device (66) opens only in the presence of a control pressure which lies in the region of the normal operating pressure of the first fuel pump (20) and closes in the event of a pressure drop to a control pressure which lies below the normal operating pressure of the first fuel pump (20).
4. Fuel system (10) according to either one of Claims 1 or 2, characterized in that the shut-off valve device (66) opens only in the presence of a control pressure which lies in the region of the minimum operating pressure of the first fuel pump (20) and closes in the event of a pressure drop to a control pressure which lies below the minimum operating pressure of the first fuel pump (20).
5. Fuel system (10) according to either one of Claims 3 or 4, characterized in that the shut-off valve device (66) comprises a pre-stressing element (72) which loads the valve element (74, 90) into the closed position of rest.
6. Fuel system (10) according to one of the preceding claims, characterized in that a pressure-limiting valve (36) is provided downstream of the blocking device (26).
7. Fuel system (10) according to Claim 6, characterized in that, downstream of the blocking device (26), a return-flow line (34) branches off from the fuel connection (24) towards the tank (16), and the pressure-limiting valve (36) is arranged in the return-flow line (34).
8. Fuel system (10) according to either one of Claims 6 or 7, characterized in that, between the outlet of the first fuel pump (20) and the blocking device (26), a line (30) branches off from the fuel connection (24) towards the tank (16), the said line having a flow throttle (32) arranged in it, and this line (30) is connected to a control connection (102) of the shut-off valve device (66)
9. Fuel system (10) according to one of the preceding claims, characterized in that the control connection of the shut-off valve device is connected to a degassing connection of the first fuel pump.
10. Fuel system (10) according to one of the preceding claims, characterized in that the shut-off valve device has a pressure-limiting function connected in parallel to the shut-off function.
11. Fuel system (10) according to one of the preceding claims, characterized in that the shut-off valve device (66) is arranged in the region of the tank (16), in particular in the region of the first fuel pump (20).
12. Fuel system (10) according to Claim 11, characterized in that the first fuel pump (20) and the shut-off valve device (66) are part of a tank installation unit.
13. Internal combustion engine (11), in particular for a motor vehicle, with a fuel system (10), which supplies the fuel (18) to at least one combustion space, characterized in that the fuel system (10) is designed according to one of Claims 1 to 12.

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