EP0922852A2

EP0922852A2 - Fuel system

Info

Publication number: EP0922852A2
Application number: EP98309693A
Authority: EP
Inventors: Stephen Michael Parker; Peter Alban George Colingborn; Peter David Allen
Original assignee: Lucas Industries Ltd
Current assignee: Delphi Technologies Inc
Priority date: 1997-12-09
Filing date: 1998-11-25
Publication date: 1999-06-16
Also published as: EP0922852A3; GB9726090D0

Abstract

A fuel system is described which comprises an injector (12) mounted in a bore of an engine cylinder head (10), a high pressure pipe (30) arranged to supply fuel to the injector (12) from a common rail (32), an end region of the pipe (30) adjacent the injector (12) extending in a direction substantially perpendicular to an axis of the injector (12), and a clamp member (38) arranged to clamp the end region of pipe (30) to the injector (12), the clamp member (38) including a drilling (40) defining a return fuel passage extending between the injector (12) and a backleak channel (44) provided in the cylinder head (10) or a cam box wall or cover (22) of the engine. The injector (12) may be modified to define a flow passage (40) which communicates directly with the backleak channel (44), thus avoiding providing a drilling in the clamp member (38).

Description

This invention relates to a fuel system for an internal combustion engine of the compression ignition type. In particular, the invention relates to a fuel system of the type comprising an accumulator or common rail which is arranged to be charged with fuel by an appropriate high pressure fuel pump. A plurality of individually actuable fuel injectors is connected through appropriate high pressure fuel pipes to the common rail or accumulator.
It is desirable not to significantly increase the effective length of the injector by providing a high pressure pipe which extends axially from the end of the injector. It is also desirable to provide a fuel system which is simple to assemble and in which the application of side loads to the injector is avoided. It is also an object of the invention to provide a fuel system in which the backleak connection from an injector to a low pressure fuel reservoir is simple to assemble.
US 5365907 and US 3845748 describe arrangements in which a backleak channel is provided in a wall associated with an engine, appropriate passage means being provided to supply fuel from a backleak passage of an injector to the channel.
US 5419298 relates to an arrangement in which a high pressure fuel pipe between a pump and an injector is bent through approximately 180°, the ends of the pipe being substantially parallel to one another.
EP 0754854 illustrates an arrangement in which a high pressure connection to an injector is achieved using a banjo member. EP 0627553 illustrates an arrangement in which a high pressure supply connector includes a low pressure fuel return path. GB 2314123 also illustrates a high pressure connector including a low pressure fuel return path.
EP 0836003 relates to an injector having a body portion with laterally extending projections defining high and low pressure fuel passages.
According to the present invention there is provided a fuel system comprising an injector mounted in a bore of an engine cylinder head, a high pressure pipe arranged to supply fuel to the injector from a common rail, an end region of the pipe adjacent the injector extending in a direction substantially perpendicular to an axis of the injector, and a clamp member arranged to clamp the end region of pipe to the injector, the clamp member including a drilling defining a return fuel passage extending between the injector and a backleak channel provided in the cylinder head or a cam box wall or cover of the engine.
The fuel pipe is conveniently bent through approximately 180° so that the ends thereof are substantially parallel to one another.
Such a configuration is advantageous in that assembly is simplified as additional slack is available in the high pressure fuel pipe than would be the case if the ends of the pipe were coaxial.
Conveniently, the injector is provided with a seating with which an enlarged part of the fuel pipe is engageable to provide a substantially fluid tight seal between the fuel pipe and the injector.
The clamp member may be engageable with a banjo member mounted upon the injector, or alternatively, the clamp member may be engageable directly with the injector. When the clamp member is engageable directly with the injector, the injector may include a region extending in a direction substantially perpendicular to the axis of the injector with which the clamp member is engageable.
The invention also relates to a fuel system comprising a plurality of injectors mounted on an associated engine, a wall of the engine being provided with a backleak channel, and a plurality of clamp members whereby fuel from backleak passages of the injectors can flow to the backleak channel.
According to another aspect of the invention there is provided a fuel system comprising a fuel injector mounted in a bore of an engine cylinder head, a high pressure pipe arranged to supply fuel to the injector from a common rail, an end region of the pipe adjacent the injector extending in a direction substantially perpendicular to an axis of the injector, and a clamp member arranged to clamp the end region of the pipe to the injector, the injector including a region extending substantially perpendicularly to the axis of the injector and defining a return fuel passage which communicates, directly, with a backleak channel provided in the cylinder head or a cam box wall or cover of the engine.
The invention also relates to a fuel injector for use in such a fuel system.
The invention will further be described, by way of example, with reference to the accompanying drawings, in which:-
Figure 1 is a view of part of an engine and associated fuel system in accordance with an embodiment of the invention; and
Figures 2 to 6 are views of alternative arrangements.
Figure 1 illustrates a cylinder head 10 having bores formed therein within which a plurality of injectors 12 (only one of which is shown) is located. The injectors 12 are of the electromagnetically actuated type and, other than as described hereinafter, the injectors 12 are of substantially conventional form. The injectors 12 are substantially identical to one another and only one of the injectors will be described hereinafter.
Each injector defines an axis along which a valve needle is moveable, the needle being engageable with a seating to control the delivery of fuel by the injector.
The upper end of the injector 12 is provided with an electrical connector 14 whereby signals are applied to the injector 12 to control the operation of electrical or electromagnetic parts thereof to control the timing and duration of injection. A connector cable 16 is secured to the connector 14 by means of a screw 18, the cable 16 terminating at a socket 20 which is located in part of the cam box cover 22 of the engine.
Also adjacent the upper end of the injector 12, a frustoconical seating 24 is provided which communicates with a high pressure fuel supply passage 26 of the injector whereby fuel under pressure is applied to the injector. An enlarged head 28 of a high pressure fuel pipe 30 engages the seating 24, the other end of the high pressure fuel pipe 30 being connected to a source of fuel at high pressure, the fuel source comprising a common rail 32 which is charged with fuel through an inlet connection 34 by an appropriate high pressure fuel pump (not shown).
A banjo member 36 is located around an upper part of the injector 12, the banjo member 36 including a through bore within which part of the injector 12 is located, and a radially extending passage through which the high pressure fuel pipe 30 extends to permit the head 28 thereof to engage the seating 24. The radially extending passage of the banjo member 36 is provided with an internal screw-thread which mates with an external screw-thread provided on an end part of a clamp member 38, the clamp member 38 being provided with an axially extending passage through which the fuel pipe 30 extends, an end part of the passage of the clamp member 38 being shaped to engage the enlarged head 28 of the fuel pipe 30 to ensure that the head 28 is clamped in sealing engagement with the seating 24.
The clamp member 38 extends through an opening provided in the cam box cover 22, the part of the clamp member 38 exposed from the cam box cover 22 being shaped to receive an appropriate tool to permit rotation of the clamp member 38 during assembly.
An annular chamber 40a is defined between the injector 12, banjo member 36 and clamp member 38, the annular chamber 40a communicating with a return fuel passage 40 provided in the clamp member 38. The annular chamber 40a receives fuel from a backleak passage 12a of the injector 12. The passage 40 further communicates with an annular chamber 40b defined between the clamp member 38 and cam box cover 22, the annular chamber 40b communicating through a drilling 42 with a backleak channel 44 provided in the cam box cover 22 which communicates, in use, with an appropriate low pressure fuel reservoir. The backleak channel 44 communicates with a plurality of drillings 42 thus permitting each injector to be connected to the backleak channel 44.
As illustrated in Figure 1, appropriate O-ring seals are located between the injector 12, banjo member 36, connector member 38 and cam box cover 22 to reduce the leakage of fuel from the fuel system, in use.
In order to assist assembly and compensate for any manufacturing inaccuracies, it is desirable for the threaded connection between the clamp member 38 and banjo member 36 to be slightly loose, thus permitting the clamp member 38 to occupy a position which is slightly offset from the axis of the radially extending passage of the banjo member 36. It will be appreciated that the use of the enlarged, dome-like head 28 and frustoconical seating 24 is a self-centring arrangement thus assisting in assembly. The use of a high pressure fuel pipe 30 which is bent through 180°, the ends of the high pressure fuel pipe 30 being substantially parallel to one another is advantageous in that assembly is simplified as an increased amount of slack is available in the fuel pipe 30 resulting in the clamp member 38 being more manoeuvrable during assembly. An additional advantage of this arrangement is that the use of the banjo member 36 and clamp member 38 to secure the high pressure fuel pipe 30 to the injector 12 avoids the application of a side load to the injector, and instead a compressive load is applied across the diameter of the injector 12.
A further advantage of this arrangement is that the provision of a return fuel passage to the backleak channel can be achieved in a relatively simple and convenient manner.
The arrangement illustrated in Figure 2 is similar to that of Figure 1 but differs therefrom in that the banjo member 36 is not used, and instead the injector 12 is provided with an externally screw-threaded, radially extending projection 46 with which an internally screw-threaded part of the clamp member 38 is engageable to clamp the head 28 of the fuel pipe 30 against a seating 24 provided at an end of the projection 46.
In the arrangement of Figure 3, the projection 46 is of increased axial length, the projection 46 extending through the cam box cover 22 and incorporating the passage 40 which communicates directly with the backleak channel 44. Clearly, as the injector 12 communicates directly with the backleak channel 44, the clamp member 38 does not contain a low pressure backleak passage, and rather is used simply to clamp the enlarged head of the fuel pipe 30 to the seating 24. As in the arrangement of Figure 1, the clamp member 38 of the Figure 3 arrangement is provided with an externally screw-threaded region which is received within an internally screw-threaded part of the projection 46.
The arrangement of Figure 4 is also similar to that of Figure 2, the projection 46 being of increased axial length, but being insufficient to extend through the cam box cover 22. In this arrangement, the projection 46 is provided with an externally screw-threaded part which is engaged by an internally screw-threaded part of the clamp member 38.
In each of the arrangements described hereinbefore, the injector is of relatively short axial length as the high pressure connection to the injector is achieved by means of the lateral clamping load applied by the clamping member, and a return fuel passage to the backleak channel is achieved in a simple and convenient manner. In each case, it will be appreciated that the clamp member does not carry fuel under high pressure, but rather applies a clamping load to form a seal between the high pressure pipe and the injector.
The arrangement illustrated in Figure 5 differs from those described hereinbefore in that the injector 12 extends through the cam box cover 22. As the upper part of the injector 12 is exposed through the cam box cover 22, the electrical connections can be made directly to the injector 12 thus the provision of a separate socket 20 can be avoided. Further, as the injector 12 extends through the cam box cover 22, the backleak connection between the injector 12 and backleak connector channel 44 can be direct, thus no flow channel for backleak fuel is provided in the high pressure fuel clamp member 38.
In the arrangement of Figure 5, the clamp member 38 includes an externally screw-threaded region which is received within an internally screw-threaded bore which is orientated at approximately 45° to the axis of the injector 12 and which communicates with the high pressure fuel passage 26 of the injector 12. As the end of the fuel pipe 30 connected to the injector 12 is orientated at approximately 45° to the axis of the injector 12, the connection of the high pressure fuel pipe 30 to the common rail 32 is similarly orientated.
In the arrangement illustrated in Figure 6, the backleak flow channel 44 is not provided in the cam box cover 22 but rather is provided in a wall of the common rail 32. This permits recovery of heat from the fuel escaping from the injector, thus improving the efficiency of the fuel system and reducing the temperature of the fuel returning to the fuel tank. A backleak connector line 48 is provided to permit communication between the backleak passage of the injector 12 and the channel 44.
Although in the description hereinbefore, the backleak channel 44 is provided in the cam box cover, it will be appreciated that the channel may be provided in another part of the wall of the engine.

Claims

A fuel system comprising an injector (12) mounted in a bore of an engine cylinder head (10), a high pressure pipe (30) arranged to supply fuel to the injector (12) from a common rail (32), an end region of the pipe (30) adjacent the injector (12) extending in a direction substantially perpendicular to an axis of the injector (12), and a clamp member (38) arranged to clamp the end region of pipe (30) to the injector (12), the clamp member (38) including a drilling (40) defining a return fuel passage extending between the injector (12) and a backleak channel (44) provided in the cylinder head (10) or a cam box wall or cover (22) of the engine.
A fuel system as claimed in Claim 1, wherein the injector (12) is provided with a seating with which an enlarged part of the fuel pipe (30) is engageable to form a substantially fluid tight seal between the fuel pipe (30) and the injector (12).
A fuel system as claimed in Claim 1 or Claim 2, wherein the clamp member (38) is engageable with a banjo member (36) mounted upon the injector (12).
A fuel system as claimed in Claim 1 or Claim 2, wherein the clamp member (38) is engageable directly with the injector (12).
A fuel system as claimed in Claim 4, wherein the clamp member (38) is engageable with a region of the injector (12) extending in a direction substantially perpendicular to the axis of the injector (12).
A fuel system comprising a fuel injector (12) mounted in a bore of an engine cylinder head (10), a high pressure pipe (30) arranged to supply fuel to the injector (12) from a common rail (32), an end region of the pipe (30) adjacent the injector (12) extending in a direction substantially perpendicular to an axis of the injector (12), and a clamp member (38) arranged to clamp the end region of the pipe (30) to the injector (12), the injector (12) including a region extending substantially perpendicularly to the axis of the injector and defining a return fuel passage (40) which communicates, directly, with a backleak channel (44) provided in the cylinder head (10) or a cam box wall or cover (22) of the engine.
A fuel system as claimed in any one of the preceding claims, wherein the fuel pipe (30) is bent through approximately 180°, the ends thereof extending substantially parallel to one another.
A fuel injector for use in a fuel system as claimed in any one of the preceding claims.