DE102006018702A1 - Fuel high-pressure conveying device - Google Patents

Abstract

A high-pressure fuel delivery device (18) for an internal combustion engine comprises a high-pressure pump (36) and a low-pressure flow path (72). Said low-pressure flow path (72) leads from a fuel inlet (28) of the high-pressure fuel delivery device (18) to a holding space (40) for a driveshaft (44) of the high-pressure pump (36) and onward to at least one inlet valve (56) of the high-pressure pump (36). Leakage and/or lubricating fuel is recirculated via a recirculation flow path (62). It is proposed that the recirculation flow path (62) opens out (66) into the low-pressure flow path (72).

Description

State of technology

The The invention relates to a high-pressure fuel conveyor according to the preamble of claim 1.

from Common-rail fuel systems for internal combustion engines are known with the market Direct fuel injection. Such fuel systems include an electric feed pump, the Promotes the fuel from a tank to a high-pressure fuel conveyor. These again comprises a mechanically driven by the internal combustion engine Piston high-pressure pump that delivers the fuel to the common rail. For lubrication and cooling the bearing of a drive shaft of the high pressure pump becomes the fuel from a fuel inlet of the high-pressure fuel delivery device first in the interior of a housing the high pressure pump, in particular in a receiving space for the drive shaft directed. From there flows the biggest part of fuel on to inlet valves of high-pressure pump. However, due to the shaft bearings and shaft seals of the drive shaft flows a small part of the fuel that has flowed into the receiving space from. This one is about one Return flow path, usually as return line referred to, returned to the tank.

Disclosure of the invention

Technical task

The The present invention has the object, a high-pressure fuel conveyor to create the type mentioned, which is a cheaper Structure of the fuel system allows.

Technical solution

These Task is by a fuel high-pressure conveyor with the features of claim 1. Advantageous developments are specified in subclaims. Further for the invention Essential features are further in the following description and the drawing discloses. Here are the individual features in very different combinations essential to the invention be without explicit reference to this.

advantageous effects

at Use of the fuel high-pressure conveyor according to the invention can lead to a tank Return line be waived. This is the structure of a fuel system, in which the fuel high-pressure conveyor according to the invention is installed, simplified, which in the production as well as in operation and Maintenance costs can be saved.

Reached This is due to the fact that the return flow path the high-pressure fuel conveyor do not leave, but is integrated into it. The example by the shaft bearings and / or Shaft seals the drive shaft passing fuel is So not returned to the tank, but remains within the fuel high pressure conveyor, by entering the low-pressure flow path is initiated. In this way, an undesirable heating of the avoided in the fuel tank stored fuel.

A advantageous embodiment of the fuel high-pressure conveyor according to the invention is characterized in that it comprises an integrated prefeed pump.

In order to a particularly compact and powerful high-pressure fuel conveyor is created.

In Further education is possible that the pre-feed pump arranged in the low-pressure flow path is, and that the return flow path upstream from the pre-feed pump in the low pressure flow path empties. A fuel system with such configured high pressure fuel delivery builds very easy and compact.

there can be a mechanical pressure control valve with a return channel be provided upstream from the pre-feed pump in the low pressure flow path empties. In this way, a constant inlet pressure to the inlet valve realized the high-pressure pump, and still builds the high-pressure fuel conveyor Compact and easy, as a separate return channel is not required is.

alternative Can the high-pressure fuel conveyor connectable with an external feed pump be. Such can be, for example, in the area of the tank of the fuel system be provided, to which the fuel high-pressure conveyor belongs. In this way it is avoided that between the high-pressure fuel conveyor and the tank a fuel line with a comparatively low pressure is present, in which, for example, vapor bubbles can form.

A particularly advantageous development of the fuel high-pressure conveyor according to the invention is characterized in that in Low-pressure flow path is arranged a suction jet pump, which is driven by the fuel flowing to the inlet valve and in which opens the return flow path. The passing through the shaft bearings, for example, amount of fuel is sucked in this way by the suction jet pump. The sum of the amount of fuel flowing directly from the receiving space to the inlet valve and the amount of flow recirculated via the return flow path is then available as a high-pressure delivery quantity. Such a high-pressure fuel delivery device has a good efficiency, and moreover, the lubrication of the bearings is improved by the forced suction of the lubricating fuel. Especially when an external prefeed pump is provided, with which the fuel high-pressure conveyor is connectable, the return of the lubricating fuel is ensured even at low speeds of the high pressure pump by such a suction jet pump.

If the prefeed pump is electrically driven, the setting of the prefeed pressure, So the pressure with which the fuel through the receiving space conveyed through the inlet valve will be adjusted, especially well. In addition, you then have a lot more Degrees of freedom with regard to the placement of the prefeed pump.

Becomes the prefeed pump but at least indirectly driven by the internal combustion engine, can be a particularly compact high-pressure fuel conveyor be created.

In the low pressure flow path can be downstream from the mouth of the return flow path an adjustable throttle device may be arranged. Such, Also referred to as "metering unit" throttle device allows a setting of the flow rate the high-pressure pump and thus the high-pressure fuel conveyor. By the invention proposed Placement of the throttle device, the flow rate through the over Recirculation flow path returned fuel quantity unaffected.

In the return flow path can have at least one flow restrictor be arranged. Through this, the amount of fuel returned via the return flow path can be targeted can be adjusted, which further improves the efficiency of the fuel high-pressure conveyor according to the invention.

Short description the drawings

following become particularly preferred embodiments the present invention with reference to the accompanying Drawing closer explained. In the drawing show:

1 a schematic representation of a fuel system with a first embodiment of a high-pressure fuel conveyor; and

2 a representation similar 1 but with a second embodiment of a high-pressure fuel delivery device.

embodiments the invention

In 1 a fuel system carries the overall reference numeral 10 , It belongs to an internal combustion engine, not shown, which in turn drives a motor vehicle, not shown.

The fuel system 10 includes a fuel tank 12 in which a liquid fuel, such as gasoline or diesel, is stored. From the fuel tank 12 leads a fuel line 14 over a filter 16 to a high-pressure fuel delivery device 18 , In this, the fuel is compressed to a high pressure and to a fuel pressure accumulator 20 promoted, which is also called "Rail". To the rail 20 are several fuel injectors 22 connected, which inject the fuel directly into them associated combustion chambers (not shown) of the internal combustion engine. To the rail 20 is a controllable pressure relief valve 24 connected, from which a drain line 26 to the fuel tank 12 returns.

The fuel high-pressure conveyor 18 includes a fuel inlet 28 to the fuel line 14 connected. From the fuel inlet 28 leads a channel 30 to a prefeed pump 32 Into the fuel high-pressure conveyor 18 is integrated. From the pre-feed pump 32 leads a channel 34 to a high pressure pump 36 , The high pressure pump 36 as well as the pre-feed pump 32 mechanically driven by the internal combustion engine, for example by a camshaft of the internal combustion engine. The high pressure pump 36 includes a housing 38 with a recording room 40 for one with a cam 42 provided drive shaft 44 , This works with two pistons 46a and 46b together, the extraction rooms 48a respectively 48b limit.

From the recording room 40 leads a channel 50 to an adjustable throttle device 52 from which in turn channels 54a and 54b via inlet valves 56a and 56b to the delivery rooms 48a and 48b to lead. channels 58a and 58b connect the conveyor rooms 48a and 48b with exhaust valves 60a and 60b , These simultaneously form a fuel outlet of the high-pressure fuel conveyor, to which the rail 20 connected.

The drive shaft 44 is in the case 38 the high pressure pump 36 stored by shaft bearings. The recording room 40 is sealed via corresponding shaft seals to the outside. However, these are not absolutely tight and therefore in 1 through channels 62a and 62b and corresponding throttles 64a and 64b designated. The throttle or shaft seal 64a is in a housing cover, the throttle or shaft seal 64b arranged in a housing body. About limiting throttles 65a and 65b lead the channels 62a and 62b to the canal 30 back. The estuary is with 66 designated. From the canal 50 branches still another overflow channel 68 in which a mechanical pressure control or overflow valve 70 is arranged. The overflow channel 68 flows into the canal 62a and thus ultimately 66 in the channel 30 ,

In the channels 30 . 34 , in the recording room 40 , in the canal 50 and in the channels 54a and 54b There is a comparatively low pressure. This flow path is therefore also referred to as "low-pressure flow path". He bears the reference numeral 72 , The through the shaft seals 64a and 64b passing fuel is through the channels 62a and 62b to the mouth 66 recycled. The channels 62a and 62b are therefore also referred to as "return flow path".

In operation, the fuel from the pre-feed pump 32 from the fuel tank 12 aspirated and to a comparatively low feed pressure, for example, 4 bar, compressed and with this pressure in the receiving space 40 promoted. There it serves for cooling and lubrication of the bearings of the drive shaft 44 , From the recording room 40 the fuel flows over the adjustable throttle 52 to the intake valves 56a , b and further into the pumping rooms 48a , b, where he compresses and over the exhaust valves 60a , b to the rail 20 is encouraged. The for lubrication of bearings of the drive shaft 44 and about the shaft seals 64a , B fuel passing through the return flow path 62a , b on the suction side (channel 30 ) of the pre-feed pump 32 promoted and sucked by this again.

A fuel system 10 with an alternative embodiment of a high-pressure fuel delivery device 18 is in 2 shown. It is true that such elements and areas that have equivalent functions to previously described elements and areas, the same reference numerals and are not explained in detail again.

In the fuel system 10 from 2 is the prefeed pump 32 not in the fuel high-pressure conveyor 18 integrated, but as an external feed pump 32 in the area of the fuel tank 12 arranged. It is also not powered by the internal combustion engine, but electrically. Also the pressure control valve 70 with the overflow channel 68 is in the area of the pre-feed pump 32 close to the fuel tank 12 arranged.

In the channel 50 , the reception room 40 over the adjustable throttle 52 to the channels 54a , b and on to the intake valves 56a , b, is a suction jet pump 74 arranged. So this is from the recording room 40 to the intake valves 56a , b flowing fuel is driven, and into it flows into 66 the return flow path 62a , b.

Claims (11)

Fuel high pressure conveyor ( 18 ) for an internal combustion engine, with a high-pressure pump ( 36 ) and with a low pressure flow path ( 72 ) coming from a fuel inlet ( 28 ) of the high-pressure fuel delivery device ( 18 ) to a recording room ( 40 ) for a drive shaft ( 44 ) of the high-pressure pump ( 36 ) and on to at least one inlet valve ( 56 ) of the high-pressure pump ( 36 ) and with a recycle flow path ( 62 ), is returned via the leakage and / or lubricating fuel, characterized in that the return flow path ( 62 ) in the low pressure flow path ( 72 ) ( 66 ). Fuel high pressure conveyor ( 18 ) according to claim 1, characterized in that it has an integrated prefeed pump ( 32 ). Fuel high pressure conveyor ( 18 ) according to claim 2, characterized in that the prefeed pump ( 32 ) in the low pressure flow path ( 72 ) and that the return flow path ( 62 ) upstream of the feed pump ( 32 ) in the low pressure flow path ( 72 ) ( 66 ). Fuel high pressure conveyor ( 18 ) according to one of claims 2 or 3, characterized in that it comprises a mechanical pressure regulating valve ( 70 ) with an overflow channel ( 68 ), which upstream of the feed pump ( 32 ) in the low pressure flow path ( 72 ) opens. Fuel high pressure conveyor ( 18 ) according to claim 1, characterized in that it is connected to an external prefeed pump ( 32 ) is connectable. Fuel high pressure conveyor ( 18 ) according to claim 5, characterized in that the return flow path ( 62 ) between the recording room ( 40 ) and the inlet valve ( 56 ) in the low pressure flow path ( 72 ) ( 66 ). Fuel high pressure conveyor ( 18 ) according to one of the preceding claims, characterized in that in the low-pressure flow path ( 72 ) a suction jet pump ( 74 ) arranged from the to the inlet valve ( 56 ) and in which the return flow path ( 62 ) ( 66 ). Fuel high pressure conveyor ( 18 ) according to one of claims 2 to 7, characterized in that the prefeed pump ( 32 ) is electrically driven. Fuel high pressure conveyor ( 18 ) according to one of claims 2 to 7, characterized in that the prefeed pump ( 32 ) is at least indirectly driven by the internal combustion engine. Fuel high pressure conveyor ( 18 ) according to one of the preceding claims, characterized in that in the low-pressure flow path ( 72 ) downstream of the mouth ( 66 ) of the return flow path ( 62 ) an adjustable throttle device ( 52 ) is arranged. Fuel high pressure conveyor ( 18 ) according to one of the preceding claims, characterized in that in the return flow path ( 62 ) at least one flow restrictor ( 65 ) is arranged.