DE102011086681A1 - Fuel feed system for a vehicle - Google Patents

Abstract

A fuel delivery system 10 for a vehicle includes a prefeed pump 14 for delivering fuel from a tank 100, a high pressure pump 12 for delivering the fuel to a common rail system 24, and a filter 16 between the prefeed pump 14 and the high pressure pump 12 for filtering the fuel fuel. the prefeed pump 14 is controllable, wherein the prefeed pump 14 is regulated based on a first fuel pressure upstream of the filter 16 and a second fuel pressure downstream of the filter 16.

Description

FIELD OF THE INVENTION

The invention relates to the field of common rail injection systems. In particular, the invention relates to a fuel delivery system for a vehicle.

BACKGROUND OF THE INVENTION

Many vehicles today have a common rail injection system, an injection system for an internal combustion engine in which a high pressure pump pumps the fuel, such as diesel, to a high pressure level. The pressurized fuel fills a piping system to which the injectors are connected in common and which is constantly under pressure during engine operation.

For the pressure supply of the high-pressure pump different feed pumps can be used. In the commercial vehicle sector, it is customary to supply the fuel to the high-pressure pump by means of mechanically driven constant-displacement pumps (geared or vane pumps). Because of hot start and idle flow requirements, these priming pumps are usually oversized relative to normal operating speeds.

In the passenger car sector, variable-speed electric fuel delivery pumps (such as roller-type or gear pumps) are also used. However, these are not generally used in the commercial vehicle sector because of their robustness and service life, which is not sufficient for internal combustion engine applications.

In vehicles mechanically or hydraulically controlled mechanically driven feed pumps (such as vane or pendulum slide pumps) for conveying engine oil or hydraulic oil are also in use.

SUMMARY OF THE INVENTION

Between the high-pressure pump and the prefeed pump, a fuel filter is usually arranged, which is to filter foreign matter from the fuel. This filter may burst if the pressure is too high. This is bypassed in an unregulated feed pump, for example, characterized in that a burst protection valve or pressure relief valve is provided in parallel to the feed pump, which opens from a certain pressure and the already funded by the prefeed pump fuel flows back towards the tank. Furthermore, an overflow valve can be provided which adjusts the operating pressure of the high-pressure pump downstream of the filter and, in the event of an overpressure downstream of the filter, can return fuel from the high-pressure pump into the tank. In this way, an overpressure in front of the filter and in the high-pressure pump can be avoided. Nevertheless, this is associated with energy losses, since in both cases, the prefeed pump promotes more fuel than would actually be necessary for the function of the high-pressure pump.

It is an object of the invention to provide a more energy-efficient fuel delivery system.

This object is solved by the subject matter of the independent claim. Further embodiments of the invention will become apparent from the dependent claims and from the following description.

One aspect of the invention relates to a fuel delivery system for a vehicle, such as a diesel delivery system in a commercial vehicle.

According to one embodiment of the invention, the fuel delivery system comprises a prefeed pump for delivering fuel from a tank, a high pressure pump for supplying the fuel to a common rail system, and a filter between the prefeed pump and the high pressure pump for filtering the fuel. The prefeed pump is adjustable, the control being based on a first fuel pressure upstream of the filter and a second fuel pressure downstream of the filter, the operating pressure. In other words, the fuel delivery system may have two control ports through which the pressure before and after the filter can be tapped. For example, a delivery rate of the prefeed pump may be controlled based on the first fuel pressure and the second fuel pressure.

The fuel delivery system may thus comprise a controllable feed pump for a common-rail high-pressure pump, which has both a pressure limiting function for limiting the maximum pressure before filter and a flow control for adjusting the operating pressure by filter. In this way, only a lower drive torque or a lower drive power for the prefeed pump in the operating speed range is usually necessary. This in turn can lead to fuel savings and thus contribute to reducing the CO ₂ emission of the vehicle. In addition, in the fuel delivery system an overflow valve and pressure relief valve can be omitted, which reduces the complexity of the fuel delivery system.

According to one embodiment of the invention, the control is such that the delivery rate of the prefeed pump is based on (only) the first Fuel pressure is reduced to zero, in order not to exceed a maximum pressure with blocked filter and thus to avoid a bursting of the filter.

According to one embodiment of the invention, the prefeed pump is a mechanically controllable pump. In other words, the prefeed pump can be controlled directly by a force based on the first and second pressures. For example, the fuel delivery system on supply lines or control connections via which the feed pump is connected to a line before and a line to the filter.

According to one embodiment of the invention, the prefeed pump is a vane pump. A vane pump can be mechanically controlled in a simple manner. For example, the vane pump may have an outer ring, inside which a wheel with wings is received. Between the wheel and the outer ring, a delivery chamber of the vane pump can be formed, which can be increased and reduced by moving the outer ring relative to the wheel. This move can. Pressure surfaces on the outer ring, which are acted upon by the first and the second pressure, are accomplished against an opposite spring, whereby the vane pump can be controlled hydraulically-mechanically.

Thus, the vane pump may include an adjustment mechanism (i.e., the adjustable outer ring) which is a pressure regulator and restrictor integrated into the prefeed pump.

According to one embodiment of the invention, the prefeed pump to a first pressure surface, which is acted upon by the first fuel pressure and having a second pressure surface, which is acted upon by the second fuel pressure. The two pressure surfaces may for example be present on a piston, so that a force can be formed with the piston, which then acts on one side of the outer ring of the prefeed pump. The two pressure surfaces can for example also be realized directly by approaches on the outer ring. On the other side of the outer ring can be exerted by a spring, a force on the outer ring, which counteracts the force through the pressure surfaces.

The vane cell pump can thus have an adjustable outer ring, which controls the delivery rate of the vane pump via two pressure surfaces with the first and second pressure before and after the main filter.

According to one embodiment of the invention, the ratio of the first pressure surface to the second pressure surface is approximately 0.4 to 0.6. In this way, a delivery rate of the feed pump can be adjusted so that, for example, an operating pressure of about 4 to 6 bar depending on the high-pressure pump delivery and the filter load and a maximum overpressure in the event of failure of a blocked filter of about 14 bar with minimal / no flow rate.

According to one embodiment of the invention, the fuel delivery system comprises a discharge for fuel, which is designed to return fuel from the filter, which is to be supplied to the high-pressure pump, and fuel from the high-pressure pump in the tank. This derivative can be used, for example, that the prefeed pump promotes even a minimum flow rate when no fuel is pumped from the high pressure pump in the common rail system. The minimum flow rate may be necessary for cooling and lubricating the high pressure pump.

A control connection of the feed pump can also be connected to this derivative.

According to one embodiment of the invention, the fuel delivery system further comprises a throttle valve between the tank and the control port. About this throttle valve, the minimum flow of Vorförderpumpe or the minimum amount of cooling fuel can be adjusted.

According to one embodiment of the invention, the fuel delivery system further comprises a check valve between the tank and the throttle valve. This valve can be used so that only after a certain minimum pressure downstream of the filter, for example, when the driving internal combustion engine is started and at least idling, the minimum flow rate is returned to the tank. In other words, the throttle valve can be switched off with the check valve in the start case.

BRIEF DESCRIPTION OF THE FIGURES

Embodiments of the invention will now be described in detail with reference to the accompanying drawings.

1 shows a fuel delivery system according to an embodiment of the invention.

2 shows a feed pump for a fuel delivery system according to an embodiment of the invention.

Basically, identical or similar parts are provided with the same reference numerals.

DETAILED DESCRIPTION OF EMBODIMENTS

1 shows a fuel delivery system 10 with a high pressure pump 12 and a prefeed pump 14 for a motor vehicle. Between the high pressure pump 12 and the pre-feed pump 14 is a fuel filter 16 arranged. In normal operation, the prefeed pump delivers fuel from a supply line 18 , which is connected to a tank of the vehicle (for example, via a pre-filter), and compresses the fuel to an operating pressure, which via a line 20 the fuel filter 16 is supplied. About a line 22 becomes the pre-compressed fuel of the high pressure pump 12 fed, which compresses it to over 1000 bar and over other lines 24 the common rail system of the vehicle supplies.

About a metering unit 26 that in a line 28 from the inlet 22 the high pressure pump to suction valves 30 is arranged on the high pressure pump, the flow rate of the high pressure pump 12 be set.

To the line 28 is between the suction valves 30 and the metering unit 26 a return line 32 connected by the via a throttle 34 and a check valve 36 Fuel in the supply line 18 the pre-feed pump 12 can be returned. About the throttle 34 can leak with closed metering unit 26 be discharged and certainly a flow rate of the high-pressure pump 12 be prevented, for example, in overrun when no fuel is removed from the common rail system. The check valve 36 prevents fuel flow at the filter 16 over to the suction valves 30 and thus in the common rail system, if after maintenance work (for example, filter replacement) the fuel delivery system 10 is refilled from the tank with pressure, for example via a hand pump. The fuel is at the non-rotating feed pump 14 over the parallel bypass valve 54 directed.

About the line 22 The engine of the high pressure pump is also supplied with cooling and lubricating amount. About a return 38 can be from the pressure lubricated bearings 40 and 42 the high pressure pump 12 escaping fuel are returned to the tank.

To the return line 38 is a derivative 44 connected, which connects the engine area of the high-pressure pump with the tank. In the return 38 are a throttle valve 46 and a check valve 48 arranged. With the throttle valve 46 A minimum amount of fuel can be adjusted by the pre-feed pump 14 is at least promoted and for cooling the high-pressure pump 12 serves. With the check valve 48 can during the start of the engine and thus the conveyor system 10 the return flow into the tank will be interrupted.

The pre-feed pump 12 is mechanically adjustable and has a first control connection 50 and a second control port 52 on, over which a first fuel pressure in front of the filter 16 and a second fuel pressure after the filter 16 from the pre-feed pump 14 can be detected. The first control connection 50 is on the line 20 between the filters 16 and the prefeed pump 14 connected, the second control connection 52 to the derivative 44 in front of the throttle 46 and the check valve 48 , Alternatively, the control connection 52 directly to the line 22 or the engine room of the high pressure pump 12 be connected.

The pre-feed pump 14 is designed to their flow rate depending on the two pressures in the lines 20 and 44 adjust.

2 shows a prefeed pump 14 in the form of a vane pump 14 when in a housing 60 a conveyor wheel 62 with wings 64 in an outer ring 66 is included. Rotates the conveyor wheel 62 in the direction indicated by the arrow, carry the wings 64 , the fuel from the supply line 18 the pump 14 from the tank 100 through the pump chamber or the delivery chamber 68 into the derivative 20 the pump 14 at the same time the supply line 20 of the filter 16 represents.

The outer ring 66 is in the case 60 movably recorded. Just like the pump in the 2 is shown, the volume of the pump chamber changes 68 when moving the outer ring 66 in the horizontal direction and thus the pumping capacity of the pre-feed pump 14 ,

On a first side of the outer ring 66 has the prefeed pump 14 a feather 70 which exerts a force on the first page. The feather 70 is in a cavity 72 the pre-feed pump 14 taken over a line 74 with the feed 18 the pre-feed pump 14 communicates and therefore the fuel pressure in the supply line 18 is exposed.

On a second, opposite side of the outer ring 66 has the prefeed pump 14 a second cavity 76 on, over the control port 50 that with the derivative 20 communicates with the (first) pressure in front of the filter 16 can be acted upon. On the second side is the outer ring 66 with an approach 78 connected to a pressure chamber with the pressure surface 82 disconnects, via the control port 52 with the (second) pressure after the filter 16 can be acted upon.

The pressure inside the cavity 76 acts on a first printing surface 80 and generates a force on the outer ring 66 , The pressure on the neck 78 acts on a second printing surface 82 and creates another force on the outer ring 66 , For example, the ratio of the first pressure surface 80 to second printing surface 82 for example, about 0.4 to 0.6. The two printing surfaces 80 . 82 Alternatively, they could also be realized via a step-top.

Overall, affect the outer ring 66 the spring force of the spring 70 , the force of (low) pressure in the cavity 72 and sum of forces based on the first and second pressures before and after the filter 16 , The adjusting operating and maximum pressures can be determined by the choice of spring 70 and by adjusting the areas 80 . 82 be adjusted. Thus, the operating pressure downstream of the filter 16 be regulated to, for example, about 5 bar and prevent the pressure from the filter 16 exceeds a maximum value of, for example, 14 bar.

In addition, it should be noted that "encompassing" does not exclude other elements or steps, and "a" or "an" does not exclude a multitude. It should also be appreciated that features or steps described with reference to any of the above embodiments may also be used in combination with other features or steps of other embodiments described above. Reference signs in the claims are not to be considered as limiting.

Claims (9)

Fuel conveyor system ( 10 ) for a vehicle, comprising: a prefeed pump ( 14 ) for conveying fuel from a tank ( 100 ), a high pressure pump ( 12 ) for supplying the fuel to a common rail system ( 24 ); a filter ( 16 ) between the pre-feed pump ( 14 ) and the high pressure pump ( 12 ) for filtering the fuel; characterized in that the prefeed pump ( 14 ) is controllable; and the prefeed pump ( 14 ) based on a first fuel pressure in front of the filter ( 16 ) and a second fuel pressure after the filter ( 16 ) is regulated. Fuel conveyor system ( 10 ) according to claim 1, wherein a delivery rate of the prefeed pump ( 14 ) is reduced to zero based on the first fuel pressure to 16 ) not to exceed a maximum pressure. Fuel conveyor system ( 10 ) according to claim 1 or 2, wherein the prefeed pump ( 14 ) is a mechanically controllable pump. Fuel conveyor system ( 10 ) according to one of the preceding claims, wherein the prefeed pump ( 14 ) is a vane pump. Fuel conveyor system ( 10 ) according to claim 4, wherein the vane pump ( 14 ) an outer ring ( 66 ), in the interior of which a wheel ( 62 ) with wings ( 64 ), wherein a delivery space ( 68 ) of the vane pump ( 14 ) between the wheel and the outer ring ( 66 ), wherein the control by moving the outer ring ( 66 ) relative to the wheel ( 62 ) he follows. Fuel conveyor system ( 10 ) according to claim 5, wherein the prefeed pump ( 14 ) a first printing surface ( 80 ), which is acted upon by the first fuel pressure and a second pressure surface ( 82 ), which can be acted upon by the second fuel pressure. Fuel conveyor system ( 10 ) according to claim 6, wherein the ratio of the first pressure surface ( 80 ) to second printing surface ( 82 ) is about 0.4 to 0.6. Fuel conveyor system ( 10 ) according to any one of the preceding claims, further comprising: a derivative ( 44 ) for fuel designed to remove fuel from the high pressure pump ( 12 ) via a throttle valve ( 46 ) in the tank ( 100 ); where a control connection ( 52 ) of the feed pump ( 14 ) with the derivative ( 44 ) connected is. Fuel conveyor system ( 10 ) according to claim 8, further comprising: a check valve ( 48 ) between the throttle valve ( 46 ) and the tank ( 100 ).

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