DE102009027335A1 - Fuel system for an internal combustion engine - Google Patents

Abstract

The present invention relates to a fuel system (10) for an internal combustion engine (12), in particular of a motor vehicle, which has a pre-feed pump (26), a high-pressure pump (30), a metering device (36) arranged hydraulically between the pre-feed pump (26) and high-pressure pump (30) and has a zero delivery line (38) for conveying away leaks from the metering device (36). In the fuel system (10), suction means are arranged in the zero delivery line (38) or at its downstream end.

Description

The The invention relates to a fuel system for an internal combustion engine according to the preamble of claim 1.

State of the art

The DE 19926 308 A1 shows a common rail fuel system in which a prefeed pump promotes fuel flow through a fuel line from a tank to a high pressure pump. Between prefeed pump and high-pressure pump, a metering device is arranged with which the amount of fuel reaching the high-pressure pump can be influenced. Between the metering device and a delivery chamber of the high-pressure pump branches off from a zero feed line, in which a zero-feed throttle is arranged, opens. About the zero feed line is still discharged with a closed metering device passing through this leakage amount.

Disclosure of the invention

task The invention is to the efficiency of the fuel system improve.

The The object is achieved by a fuel system having the features of the claim 1 solved. Advantageous developments are specified in the subclaims. For the invention important features can be found about it In addition, in the following description and in the drawing, wherein the characteristics both alone and in different Combinations may be important to the invention without being explicitly pointed out.

advantage the suction means is a pressure reduction in the zero delivery line or at the end thereof, such that an opening pressure of an intake valve the high-pressure pump can remain low, what their efficiency improved (the opening pressure of the intake valve must with a safe distance and taking into account a Lifetime drift always be higher than the highest occurring pressure level plus the required differential pressure over the zero-delivery line and the possibly present there zero-delivery throttle). In addition, the diameter of the zero feed throttle be kept relatively small, so that in normal production case only comparatively little fuel over the zero delivery line "lost goes ". This improves the filling of a delivery chamber the high pressure pump, and especially when starting the efficiency, if the necessary pressure for this purpose is almost exclusively applied by the prefeed pump must become.

For the invention it is particularly advantageous if the suction means include a venturi nozzle. Preferably flows the zero delivery line into that area of the venturi nozzle, where the lowest pressure prevails. A venturi nozzle Builds easily and without moving parts. It is therefore inexpensive and works practically wear-free. As in a fuel system almost always the one for the operation of a Venturi nozzle necessary fuel flows are present anyway, are no additional drives for the Venturi nozzle necessary.

Especially is advantageous if the fuel system is a pressure control valve for regulating the pressure in a between pre-feed pump and high pressure pump lying low pressure area, and if the Venturi nozzle in a discharge line of the pressure control valve is arranged. Such a pressure control valve generally controls then off particularly much fuel when the metering device is closed is. Thus, the suction power of the Venturi nozzle is accurate then particularly large, if due to the closed metering device to be discharged via the zero feed line Leakage amount is maximum. Conversely, when open Metering device reduces the suction power. The suction power is Thus, automatically adapted to the needs, which the efficiency of the Fuel system particularly benefits.

The Invention works even more effectively when the diversion line, in the Venturi nozzle is arranged in a supply line opens to the feed pump. This makes it possible immediately return the leakage fuel to the inlet of the pre-feed pump encourage him to return to the fuel cycle Operating the internal combustion engine or for lubrication and cooling to initiate the drive and crankcase.

alternative For this it is also possible that the diversion line, in the Venturi nozzle is arranged in a return line flows, which leads back into a fuel tank. The recirculated fuel can be in the fuel tank cool what the temperature of the fuel system facilitated.

In a modified embodiment of the invention It is also possible that the Venturi nozzle in one Control line of the pressure control valve is arranged. should that Pressure control valve have a plurality of Absteuerleitungen, which have different opening pressures assigned to the pressure control valve, the function of the Venturi nozzle regardless of which diversion line is currently active, ensured.

In addition thereto, it is advantageous that the feed line is part of a lubricating and / or cooling line of the high-pressure pump, and that the pressure regulating valve has a first opening pressure it connects the feed line to a return line. This ensures that the Venturi nozzle flows through even at a comparatively low pressure in the low pressure range, for example when starting the internal combustion engine, with fuel and the zero discharge leakage is effectively dissipated.

Furthermore is advantageous in that the high pressure pump at least one return line for returning a bearing leakage, and that in the return line to the high pressure pump towards locking spring-loaded check valve, arranged is. The check valve causes the start of the Fuel pressure can be built up faster.

Advantageous is also that in parallel to the feed pump a spring-loaded Check valve or a pressure relief valve arranged is, which opens in the direction of feed pump inlet. The check valve or pressure relief valve has it the task, for example, in the case of using a pressure-side Fuel filter (upstream after the pre-feed pump) if there is a blockage in the filter, the prefeed pump to protect against overloading. Parallel can For this fault, a warning signal, eg. On a dashboard of the motor vehicle are discharged to the filter from the blockage to free, or replace the filter.

at Fuel systems is for filling the fuel system For example, after a repair or maintenance a hand pump intended. That is why for such an embodiment advantageous in that, parallel to the prefeed pump, a spring-loaded check or a pressure relief valve is arranged which in the direction High pressure pump inlet opens. This valve stops at Filling a bypass to the pre-feed pump, so that not all the fuel for filling by the Pre-feed pump must be pumped through.

following Be with reference to the drawings embodiments of the invention exemplified. Show it:

1 a fuel system in a first embodiment with a zero feed line, which opens in a Venturi nozzle in a Absteuerleitung a pressure control valve;

2 a sectional view of the Venturi nozzle of 1 ;

3 a fuel system in a second embodiment with a zero feed line, which opens in a Venturi nozzle in a feed line of a pressure control valve;

4 a fuel system in a third embodiment with a zero feed line, which opens in a Venturi nozzle in a return line of a pressure control valve;

5 the fuel system off 1 with a check valve in a return line;

6 the fuel system off 1 with a check valve in a line for the removal of bearing leakage of the high-pressure pump 1 to the fuel delivery line; and

7 a fuel system in a fourth embodiment with a fuel filter that between the prefeed pump and the high pressure pump from 1 is arranged.

1 shows a fuel system 10 , which is for a so-called common-rail injection system of an internal combustion engine 12 is designed. For operation of the internal combustion engine 12 Fuel is injected under high pressure into a fuel rail (Common Rail) 14 promoted and stored there, being at the fuel rail 14 Fuel injectors 16 connected to the fuel under high pressure in combustion chambers 18 the internal combustion engine 12 inject.

The fuel is from a fuel tank 20 promoted a motor vehicle. In the flow direction are in a fuel delivery path 22 , starting from the fuel tank 20 , a fuel filter 24 , a throttle 25 and a mechanically or electrically operated prefeed pump 26 arranged. The fuel path first opens for lubricating drive parts in a drive or crankcase 28 a high pressure pump 30 , which is preferably designed as a mechanically driven radial piston pump. The course of the fuel in the fuel system 10 is marked with arrows in the drawing.

The flow of fuel behind the drive and crank chamber 28 is divided into two parts. The first output of the fuel is a service line 32 for operating the internal combustion engine 12 , the second output is a supply return 34 a fuel circuit for lubricating and cooling the high pressure pump 30 ,

By the management 32 the fuel is flowing in the direction of flow through another fuel filter 35 a metering device 36 supplied, which is designed as an electromagnetically controllable, proportional spring-loaded slide valve. The metering device 36 So is fluidic or hydraulic between the prefeed pump 26 and the high pressure pump 30 arranged and used for metering the fuel for the high-pressure pump 30 , Downstream of the metering device 36 the fuel flow is divided into two again. On the one hand, a zero pipeline branches off 38 off, via a fuel filter 39 in a venturi nozzle 40 empties. A detailed description of the Venturi nozzle 40 follows further behind. On the other hand branches of the metering device 36 a promotion line 42 off, which via a suction valve 44 in a pump room 46 the high pressure pump 30 leads, the one about the high pressure pump 30 towards blocking check valve 48 with the fuel rail 14 is connectable.

Through the supply return 34 will be in the drive and crank room 28 located fuel in the flow direction via another fuel filter 50 a pressure control valve 52 supplied, which is designed as a spring-loaded spool valve with two switching stages. The supply return 34 thus also provides the Zusueuerleitung the pressure control valve 52 dar. The pressure control valve 52 includes next to the input for the supply return 34 three outputs. In the first switching stage - ie at low fuel pressure in the supply return 34 - The fuel is in a return line 54 via a throttle 56 in the fuel tank 20 promoted, in the second shift stage - at higher fuel pressure in the supply return line 34 - The fuel is in a flow line 58 promoted in which the venturi nozzle 40 is arranged. The return line 54 and the flow line 58 thus provide Absteuerleitungen the pressure control valve 52 dar. The flow line 58 flows into the fuel delivery line 22 , A third exit 60 of the pressure control valve 52 only serves to equalize the pressure when moving the spool in the pressure control valve 52 , Again, leaks can occur, the leakage fuel is via a throttle 62 in the return line 54 promoted.

The high pressure pump 30 usually has two bearings for supporting a rotary shaft of an eccentric. These bearings can also leak fuel leakage. The two bearings are in 1 as chokes 63 shown. The leakage of the bearings 63 is via the return line 54 to the fuel tank 20 recycled.

The venturi nozzle 40 is in 2 shown in section. It consists of a smooth-walled pipe on an outside 64 with a narrowing of the inner cross-section D by two oppositely directed cones 66 and 68 , which are brought together in the region of their smallest diameter D. The two cones 66 and 68 have the same tapered cross section D and the same expanded cross section 3D. All edges inside the tube 64 are rounded according to a streamline shape. The expanded cross section 3D is about three times as large as the tapered cross section D. In the flow direction 70 shows the cone 66 about the length of the tapered cross section D on; the length of the cone 68 points in the direction of flow 70 a length 3-5D of about three to five times the length of the tapered cross-section D. In the area of the position inside the pipe 64 with the tapered cross section D is perpendicular to the pipe 64 a take-off channel 72 intended. The cross-section of the take-off channel 72 is substantially smaller relative to the cross section D and is dimensioned so that it represents a throttle cross-section of a zero-feed throttle. At this zero feed throttle 72 is in the present invention, the zero-delivery line 38 connected, whereas the pipe 64 Part of the flow line 58 is. Manufacturing technology, a channel in a housing of the high-pressure pump 30 the venturi nozzle 40 have as Einpressteil. The venturi nozzle 40 but could alternatively be designed as a Schraublösung or as an external component.

The venturi nozzle 40 when used in the present invention, works as follows:
Flows through the pipe 64 - So through the flow line 58 - Fuel, so is at the narrowest point D of the pipe 64 a dynamic pressure (dynamic pressure) maximum and a static pressure (static pressure) minimal. The speed of the flowing fuel increases in proportion to the cross sections D: 3D as it flows through the constricted part of the tube 64 because the same amount of fuel flows through everywhere. Due to the comparatively low pressure in the region of the narrowest point D prevails also at the mouth of the zero-feed throttle 72 a correspondingly low pressure. This creates between the mouth of the zero feed throttle 72 into the interior of the Venturi nozzle 40 and the beginning of the zero feed line 38 a pressure difference through which fuel from the area between metering device 36 and suction valve 44 via the zero delivery line 38 is sucked off. The venturi nozzle 40 So far forms a suction at the downstream end of the zero feed line 38 ,

The fuel system 10 in the in 1 The illustrated embodiment thus works as follows:
Fuel is produced by the suction effect of the pre-feed pump 26 from the fuel tank 20 via the fuel delivery line 22 sucked. The fuel is in the fuel filter 24 filtered. The pre-feed pump 26 promotes the fuel further into the drive and crank chamber 28 the high pressure pump 30 , From there, the operation of the internal combustion engine 12 Fuel over the management 32 the opened metering device 36 fed, after which the fuel through the suction valve 44 then in the conveyor room 46 the high pressure pump 30 arrives. There, the fuel is compressed and under high pressure via the check valve 48 in the rail 14 the internal combustion engine initiated.

With closed metering device 36 (eg in overrun mode), the entire of the prefeed pump 26 Promoted fuel from the drive and crank chamber 28 over the supply line 34 to the pressure control valve 52 promoted. Due to the excess amount of fuel, the pressure in the supply line increases 34 so that the pressure control valve 52 so far that opens the fuel on the one hand, via the return line 54 to the fuel tank 20 back and on the other hand through the flow line 58 in which the venturi nozzle 40 is arranged, back to the input of the feed pump 26 is encouraged. The latter creates a fuel circuit that lubricates and cools the drive and crankcase 28 and for operating the venturi nozzle 40 serves.

Because the prefeed pump 26 usually promotes more fuel than for the operation of the internal combustion engine 12 is necessary is also at partially open metering device 36 , ie in load operation of the internal combustion engine 12 , a certain fuel flow in the supply line 34 arise, which is less than in overrun operation, so that the pressure control valve 52 only partially open. While passing through the return line 54 flowing fuel quantity thereof is (still) unaffected, is the fuel flow through the flow line 58 lower, so also the suction power of the Venturi nozzle 40 is lower.

When starting the internal combustion engine 12 is the spring-loaded pressure control valve 52 initially closed, so that about the management 32 the greatest possible fuel pressure with open metering device 36 can build up.

Is in overrun mode of the internal combustion engine 12 the metering device 36 closed, so occurs at the metering device 36 a fuel leak out. The leakage is via the zero delivery line 38 and the zero-feed throttle 72 the Venturi nozzle 40 fed. As in the case of the closed metering device 36 the flow line 58 has a large flow, arises at the entrance of the take-off tube 72 in the venturi tube 64 a greater suction than partially or fully opened metering device 36 , The venturi nozzle 40 sucks the leakage from the zero delivery line 38 and conveys it with the remaining fuel to the input of the pre-feed pump 26 into the fuel delivery line 22 ,

3 shows a second embodiment of the invention. For 3 and all subsequent figures, it is true that such elements and regions which are functionally equivalent to elements and regions of the fuel system of 1 , bear the same reference numerals and will not be explained again in detail. The difference to 1 lies in the arrangement of the Venturi nozzle 40 , This is contrary to 1 in the supply line 34 , ie in the feed line of the pressure control valve 52 arranged. The function of this embodiment is substantially identical to the described function of the embodiment in FIG 1 , The venturi nozzle 40 works even with comparatively low flow through the control line 34 ,

4 shows a third embodiment of the invention. The main difference too 1 or 3 also lies in the arrangement of the Venturi nozzle 40 , This is here in the return line 54 arranged. The venturi nozzle 40 works with comparatively constant suction power.

5 indicates an extension 1 , Here is also in the return line 54 which also includes the bearing leakage of the high pressure pump 30 dissipates one to the high pressure pump 30 locking spring-loaded check valve 74 arranged. Through the check valve 74 can be a starting pressure in the fuel system 10 be built faster and easier.

6 shows a modification of 5 in which the check valve 74 in a line for the removal of bearing leakage of the high-pressure pump 30 to the fuel delivery line 22 is arranged. Auc here is the check valve 74 to limit bearing leakage when starting.

7 shows a fourth embodiment of the invention and is a modification of 5 , However, this embodiment is also applicable to the other described embodiments. The essential difference from the previously described embodiments is the position of the fuel filter 24 , While so far the fuel filter 24 always on the suction side of the pre-feed pump 26 was arranged, here is the fuel filter 24 on the pressure side of the pre-feed pump 26 arranged. In such fuel systems, a hand pump is preferred for filling the fuel system after repair or maintenance 76 intended. In the flow direction are in front of and behind the hand pump 76 two to the fuel tank 20 blocking check valves 77 intended. In addition, they are parallel to the pre-feed pump 26 one in the direction of the high pressure pump 26 opening spring-loaded check valve 78 and in the direction of feed pump inlet opening spring-loaded check valve 80 intended. The check valve 78 serves as a bypass when filling the fuel system 10 so that not all the fuel for filling by the pre-feed pump 26 must be pumped. The check valve 80 protects against possible blockage of the fuel filter 24 the pre-feed pump 26 in front of an overload and the fuel filter 24 from damage. The treatment of the neutral pipeline 38 with the use of the Venturi nozzle 40 is identical to the previously described embodiments.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 19926308 A1 [0002]

Claims (10)

Fuel system ( 10 ) for an internal combustion engine ( 12 ), in particular of a motor vehicle, which has a prefeed pump ( 26 ), a high pressure pump ( 30 ), a hydraulic between pre-feed pump ( 26 ) and high pressure pump ( 30 ) arranged metering device ( 36 ) and a zero delivery line ( 38 ) for removing leaks from the metering device ( 36 ), characterized in that in the zero feed line ( 38 ) or at the downstream end of suction means ( 40 ) are arranged. Fuel system ( 10 ) according to claim 1, characterized in that the suction means a Venturi nozzle ( 40 ). Fuel system ( 10 ) according to claim 1 or 2, characterized in that it is a pressure regulating valve ( 52 ) for regulating the pressure in an intermediate feed pump ( 26 ) and high pressure pump ( 30 ) and that the Venturi nozzle ( 40 ) in a diversion line ( 54 . 58 ) of the pressure regulating valve ( 52 ) is arranged. Fuel system ( 10 ) according to claim 3, characterized in that the diversion line ( 58 ) in a supply line ( 22 ) to the prefeed pump ( 26 ) opens. Fuel system ( 10 ) according to claim 3, characterized in that the diversion line in a return line ( 54 ) opens. Fuel system ( 10 ) according to claim 1 or 2, characterized in that the pressure regulating valve ( 52 ) for regulating the pressure in an intermediate feed pump ( 26 ) and high pressure pump ( 30 ) and that the Venturi nozzle ( 40 ) in a control line ( 34 ) of the pressure regulating valve ( 26 ) is arranged. Fuel system ( 10 ) according to claim 6, characterized in that the control line ( 34 ) Part of a lubricating and / or cooling line of the high-pressure pump ( 30 ), and that the pressure regulating valve ( 52 ) has a first opening pressure, from which it is the control line ( 34 ) with a return line ( 54 ) connects. Fuel system ( 10 ) according to one of the preceding claims, characterized in that the high pressure pump ( 30 ) at least one return line ( 54 ) for returning a bearing leakage, and that in the return line ( 54 ) to the high pressure pump ( 30 ) locking spring-loaded check valve ( 74 ) is arranged. Fuel system ( 10 ) according to one of the preceding claims, characterized in that parallel to the prefeed pump ( 26 ) a spring-loaded check valve or a pressure relief valve ( 80 ) is arranged, which opens in the direction of feed pump inlet. Fuel system ( 10 ) according to one of the preceding claims, characterized in that parallel to the prefeed pump ( 26 ) a spring-loaded check valve or a pressure relief valve ( 78 ) which opens in the direction of the high pressure pump inlet.

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