GB2438414A

GB2438414A - Pipe to fuel injector connector allows misalignment and flow path for leakage

Info

Publication number: GB2438414A
Application number: GB0610224A
Authority: GB
Inventors: Thomas Canepa-Anson
Original assignee: Delphi Technologies Inc
Current assignee: Delphi Technologies Inc
Priority date: 2006-05-23
Filing date: 2006-05-23
Publication date: 2007-11-28
Also published as: GB0610224D0

Abstract

A fuel pipe 40 comprises an enlarged head 40b which is engaged with a fuel injector 42 to which fuel is supplied. The fuel injector inlet 42 and pipe head 40b are received within a clamping nut 62 which has a frusto-conical inner surface 70. The pipe carries an annular collar 72 having a front surface 80 of frusto-conical form to engage with the rear surface 54 of the enlarged head of the pipe, and a rear surface 78 of frusto-conical form to engage with the inner surface 70 of the clamping nut 62. The annular collar 72 defines, at least in part, a flow path for leakage fuel (see grooves 82, figures 8-10).

Description

IMPROVEMENTS RELATING TO

PIPE CONNECTIONS

Technical field

The invention relates to a fluid pipe. In particular, but not exclusively, the invention relates to a high pressure supply pipe for a fuel injector in a fuel injection system of an internal combustion engine. The invention is particularly applicable to common rail systems which transport high pressure fuel to the fuel injectors of the engine.

Background to the invention

In existing fuel injection systems it is known to transport high pressure fuel to each of the injectors via a steel pipe, the outlet end of which is connected to the inlet of the associated injector. The high pressure pipe and the injector inlet are clamped together by means of a nut.

The pipe connection to the injector inlet must have good sealing properties to ensure that any leakage of fuel between the pipe and the injector cannot contaminate the engine components underneath the engine rocker cover. It is also important that fuel leakage cannot dilute the cam box lubricating oil as this can accelerate wear of the various engine bearing surfaces.

Figure 1 shows a high pressure pipe connection, as in US 6 431 608, in which a high pressure fuel pipe 10 is connected, at its outlet end, to an inlet region 12 of an injector by means of a screw threaded clamping nut 16. The fuel pipe 10 includes a main pipe body lOa and an outlet end lOb in the form of an enlarged head or nipple which defines a frusto-conical engagement surface 18. An internal bore 20 through the pipe 10 defines a flow passage for high pressure fuel to be transported to the injector inlet region 12.

The frusto-conical engagement surface 18 of the enlarged pipe head lOb engages with a frusto-conical engagement surface 22 defined within the inlet region 12. An 0-ring seal 24 is provided between the pipe/injector interface and the cam box space 26, to prevent leakage of fuel into the cam box space 26.

An annular collar 28 is carried by the main pipe body l0a and locates immediately behind the enlarged pipe head lOb so that the front surface of the collar 28 abuts the enlarged pipe head I Ob and the rear surface of the collar 28 abuts a step 30 in the internal bore of the clamping nut 16. The collar 28 supports the pipe 10 within the clamping nut bore and transmits axial load, applied by the clamping nut 16, through the enlarged pipe head lOb to the engagement surfaces 18, 22 to provide a good seal.

In order to divert any leakage fuel at the pipe/injector interface away from the cam box 26, the collar 28 is provided with a groove 32. The groove 32 connects a chamber 34, defined between the internal bore of the clamping nut 16 and the enlarged pipe head lOb, with a clearance 36 defined between the main pipe body lOa and the internal bore of the clamping nut 16.

It has been recognised that the high pressure pipe connection described previously is difficult to manufacture, particularly because of the square-faced contact between the enlarged pipe head lOb and the collar 28. It has also been recognised that undesirable stress concentrations arise in the pipe 10, which can lead to premature wear and failure.

It is with a view to addressing these disadvantages that the present invention provides an improved pipe connection suitable for use in high pressure applications.

Summary of the invention

According to a first aspect of the present invention, there is provided a fluid pipe comprising an enlarged head which is engageable with an outlet component to which fluid is transported through the pipe, in use. The fluid pipe and the outlet component are received within a clamping nut which defines an internal bore including a surface of frusto-conical form. The fluid pipe carries an annular collar having (i) a front surface of frusto-conical form for engagement with a rear surface of the enlarged head of frusto-conical form and (ii) a rear surface of frusto-conical form for engagement with the frusto-conical surface of the clamping nut. The annular collar defines, at least in part, a flow path for leakage fuel.

Preferably, the front and rear frusto-conical surfaces of the annular collar are aligned substantially in parallel with one another. The collar is therefore a convenient component to manufacture e.g. by means of a stamping process.

The fluid pipe is preferably a high pressure fuel pipe for delivering fuel to an outlet component in the form of a fuel injector. In particular, the high pressure fuel pipe is suitable for use in a common rail fuel injection system for delivering high pressure fuel to a fuel injector of the system.

The invention provides an advantage over the prior art in US 6 431 608 in that the rear frusto-conical surface of the annular collar and its interaction with the frusto-conical surface of the internal bore of the clamping nut reduces the stress concentrations which are found to occur in US 6 431 608.

According to a second aspect of the present invention, there is provided a fluid pipe comprising an enlarged head which is engageable with an outlet component to which fluid is transported through the pipe, in use. The fluid pipe and the outlet component are received within an internal bore of a clamping nut. The inlet fluid pipe carries an annular collar having a front surface for engagement with a rear surface of the enlarged head of the pipe and a rear surface for engagement with a surface of the internal bore of the clamping nut. The front surface of the annular collar is of frusto-conical form and the rear surface of the enlarged head of the pipe is also of frusto-conical form. The annular collar defines, at least in part, a flow path for leakage fuel.

Brief descriDtion of the drawings The background to the invention has already been described, by way of example only, io with reference to Figure 1 which shows a section view of a known high pressure pipe connection to an injector.

The invention will now be described, by way of example only, with reference to the accompanying figures in which: Figure 2 is a perspective view of a high pressure connection for a fuel injector in accordance with a first embodiment of the invention, including a clamping nut, Figure 3 is another perspective view of the high pressure connection in Figure 2, with the clamping nut removed, Figure 4 is a section view of the high pressure pipe connection in Figures 2 and 3, Figure 5 is a perspective view of a high pressure connection for a fuel injector in accordance with a second embodiment of the invention, including a clamping nut, Figure 6 is another perspective view of the high pressure connection in Figure 5, with the clamping nut removed, Figure 7 is a section view of the high pressure pipe connection in Figures 5 and 6, Figure 8 is a side view of the collar of the high pressure pipe connection in Figures 5 to 7, Figure 9 is a plan view of the collar in Figure 8, and Figure 10 is a perspective view of the collar in Figures 8 and 9.

Figures 11 is a section view of the high pressure pipe connection in Figures 5 to 7, to illustrating an inlet end to the high pressure pipe, Figure 12 is a cut away view of the high pressure pipe in Figure 11, and Figure 13 is a perspective view of the high pressure pipe connection in Figures 11 and 12.

Detailed description of the preferred embodiments of the invention Figures 2 to 4 illustrate a high pressure pipe connection of a first embodiment of the invention. The pipe connection is formed between a high pressure pipe 40 and an inlet region 42 of a fuel injector of an internal combustion engine. The high pressure pipe 40 includes a main pipe body 40a and an enlarged head or nipple 40b. An internal bore 46 of the pipe 40 defines a flow passage for transporting high pressure fuel to an injector fuel passage 44 defined within the injector inlet region 42.

The injector fuel passage 44 defines an engagement surface 48 of frusto-conical form and receives the enlarged pipe head 40b. The enlarged pipe head 40b defines an engagement surface 50 of frusto-conical form which seats against the frusto-conical engagement surface 48 of the injector inlet passage 44 at the pipe/injector interface. The enlarged pipe head 40b is provided with an annular projection 52 part way along its length, referred to as an olive. The olive 52 defines a rear frusto-conical surface 54 of the enlarged pipe head 40b which tapers into the main pipe body 40a. An annular collar 56 is carried on pipe 40 and includes a rear surface 60. the annular collar also includes a front surface 58, of frusto-conical form, which engages with the rear frusto-conical surface 54 of the olive 52.

A clamping nut 62 receives the injector inlet region 42 and the high pressure pipe 40 and serves to transmit axial load to the pipe/injector interface by means of a screw-threaded engagement region 68. An 0-ring seal 66 is provided adjacent to the region of screw thread engagement 68 to prevent leakage of high pressure fuel into a cam box space 69 to the left hand side (in the orientation shown in Figure 4) of the pipe/injector interface.

The clamping nut 62 includes an internal bore 64 which extends along the length of the nut 62. The bore 64 includes a reduced diameter region which houses a significant length of the main pipe body 40a and an enlarged diameter region which receives the enlarged pipe head 40b and the injector inlet region 42. A step 66 along the bore 64 of the clamping nut 62 defines the intersection between the enlarged and reduced diameter regions of the nut 62. The step 66 makes flat, square-faced contact with the rear surface of the annular collar 56.

The annular collar 56 is of sufficient length to support the high pressure pipe 40 within the clamping nut bore 64. When the clamping nut 62 is tightened onto the injector inlet region 42 by screwing the parts 62, 42 together, an axial load is transmitted through the collar 56 to the enlarged pipe head 40b so that the engagement surfaces 48, 50 form a good seal. As can be seen in Figure 3, the annular collar 56 is of castellated form and includes a plurality (three of which are shown) of radially extending grooves 57 on its rear surface which define a leakage path for fuel. The leakage paths for fuel provide communication between (i) a space 84 defined within the enlarged diameter region of the clamping nut bore 64 and (ii) a clearance 86 defined between the reduced diameter region of the clamping nut bore 64 and the main pipe body 40a. Note that the grooves 57 in the annular collar 56 are not visible in the section shown in Figure 4.

The high pressure connection in Figures 3 to 4 provides an advantage over the prior art in US 6 431 608 in that the stress concentration in the enlarged pipe head 40b is reduced, particularly in the region of the olive 52 adjacent to the collar 58 where the olive 52 tapers into the main pipe body 40a. The benefit is achieved by virtue of the frusto-conical engagement surfaces 54, 58 of the olive 52 and the collar 56.

A further improvement to the high pressure connection of Figures 2 to 4 is illustrated in Figures 5 to 7 which shows a second embodiment of the invention, with similar parts to those shown in Figures 2 to 4 being identified with like reference numerals.

A high pressure pipe connection is formed between the high pressure pipe 40 and the inlet region 42 of the fuel injector. The high pressure pipe 40 includes a main pipe body 40a and an enlarged head or nipple 40b. The internal bore 64 of the pipe 40 defines a flow passage for transporting high pressure fuel to an injector inlet passage 44 in the injector inlet region 42.

The injector inlet passage 44 defines an engagement surface 48 of frusto-conical form into which the tip of the enlarged pipe head 40b is received. The enlarged pipe head 40b also defines an engagement surface 50 of frusto-conical form which engages with the engagement surface 48 of the inlet passage 44 at the pipe/injector interface. An annular projection or olive 52 defines a rear, frusto-conical surface 54 of the enlarged pipe head 40b which tapers into the main pipe body 40.

The clamping nut 62 receives the inlet region 42 and the high pressure pipe 40 and serves to transmit axial load to the engagement surfaces 48, 50 at the pipe/injector interface by virtue of a region of a region of screw-threaded engagement 68 between the parts 42, 62. The 0-ring seal 66 adjacent to the region of screw thread engagement 68 serves to prevent leakage of high pressure fuel into the cam box space 69. The internal bore 64 of the clamping nut 62 extends along the length of the nut 62 and includes a reduced diameter region which receives a significant length of the main pipe body 40a and an enlarged diameter region which receives the enlarged pipe head 40b and the injector inlet region 42. A stepped surface 70, of frusto-conical form, defines the intersection between the enlarged and reduced diameter regions of the bore 64 in the clamping nut 62.

Referring also to Figures 8 to 10, an annular collar 72 is carried on the main pipe body 40a and includes a front collar section 74 and a rear collar section 76. The outer periphery of the rear collar section 76 is tapered to define a rear collar surface 78 of frusto- conical form which contacts with the frusto-conical step 70 in the clamping nut bore 64. The inner periphery of the front collar section 74 is tapered to define a front collar surface 80 of frusto-conical form which engages with the rear frusto-conical surface 54 of the enlarged pipe head 40b (the inner periphery of the front collar section 74 is only visible in Figure 10). The collar 72 is thus formed with substantially parallel front and rear surfaces 80, 78 of frusto-conical form, making it a particularly convenient component to manufacture (e.g. by a stamping operation).

When the clamping nut 62 is tightened onto the injector inlet region 42 by screwing the parts 62, 42 together, an axial load is transmitted through the collar 72 to the enlarged pipe head 40b so that the engagement surfaces 48, 50 of the parts 42, 40 form a good seal at the pipe/injector interface. Compared with the collar 56 in Figures 2 to 4, the collar 72 is of much reduced length (as can be seen in Figure 7). In addition, the shaping of the rear collar surface 78 to be frusto-conical, and the shaping of the cooperable surface 70 of the nut 62 to be frusto-conical, serves to reduce the stress concentrations within the pipe 40b, compared to the arrangements in Figures 1 and 2.

The rear collar section 78 is also provided with a plurality of radially extending grooves 82 which, when the high pressure connection is assembled, define a plurality of flow paths for leakage fuel. The leakage paths provide communication between a space or chamber 84 defined within the enlarged diameter region of the clamping nut bore 64 and a clearance 86 defined between the reduced diameter region of the clamping nut bore 64 and the main pipe body 40a. In the embodiment shown in Figures 8 to 10, three grooves 82 are shown at equi-angularly spaced locations around the collar diameter, but any number of grooves may be provided.

In the event that any high pressure fuel leakage occurs at the pipe/injector interface 48, into the chamber 84, the leakage fuel is able to flow through the grooves 82 provided in the annular collar 72 and into the clearance 86 and to a low pressure drain (e.g. outside the engine). The flow of leakage fuel to the cam box 69, via the 0-ring seal 66, is thus substantially prevented.

Figures 11 to 13 illustrate an inlet region 40c of the high pressure pipe 40 in Figures 8 to 10. The inlet region 40c of the pipe 40 extends beyond the end of the clamping nut 62 and is provided with a connector 88 which may, for example, connect the pipe 40 to a common rail or to a unit pump.

Claims

Claims 1. A fluid pipe comprising an enlarged head which is engageable

with an outlet component to which fluid is transported through the pipe, in use, the outlet component and the fluid pipe being received within a clamping nut which defines an internal bore including a surface of frusto-conical form, wherein the fluid pipe carries an annular collar having (i) a front surface of frusto-conical form for engagement with a rear surface of the enlarged head of frusto-conical form and (ii) a rear surface of frusto-conical form for engagement with the frusto-conical surface of the clamping nut bore, and wherein the annular collar defines, at least in part, a flow path for leakage fuel.

2. The fluid pipe as claimed in claim 1, wherein the front and rear frusto-conical surfaces of the annular collar are aligned substantially in parallel with one another.

3. The fluid pipe as claimed in claim 2, wherein the annular collar includes a front collar section which defines the front frusto-conical surface of the annular collar and a rear collar section which defines the rear frusto-conical surface of the annular collar, wherein the front frusto-conical surface is defined on an internal diameter of the annular collar and the rear frusto-conical surface of the collar is defined on an outer diameter of the annular collar.

4. The fluid pipe as claimed in any one of claims 1 to 3, wherein the annular collar is provided with at least one radially extending groove which defines a part of the flow path for leakage fuel.

5. The fluid pipe as claimed in claim 4, wherein the annular collar is provided with a plurality of radially extending grooves arranged at equi-angularly spaced locations around the annular collar.

6. The fluid pipe as claimed in any one of claims I to 5, being a fuel pipe for transporting high pressure fuel to an outlet component in the form of a fuel injector inlet.

7. A fluid pipe substantially as herein described with reference to Figures 5 to 13.

8. A fluid pipe comprising an enlarged head which is engageable with an outlet component to which fluid is transported through the pipe, in use, the fluid pipe and the outlet component being received within an internal bore of a clamping nut, wherein the inlet fluid pipe carries an annular collar having a front surface of frusto-conical form for engagement with a rear surface of the enlarged head of frusto-conical form, and a rear surface for engagement with a surface of the internal bore of the clamping nut, wherein the annular collar defines, at least in part, a flow path for leakage fuel.

9. A fluid pipe substantially as herein described with reference to Figures 2 to 4.