GB2598318A

GB2598318A - Common rail housing and a method of forming a drilling in a common rail housing

Info

Publication number: GB2598318A
Application number: GB2013260.1A
Authority: GB
Inventors: Ates Ceren; Sarman Tolga; Akin Levent
Original assignee: Delphi Technologies IP Ltd
Current assignee: Delphi Technologies IP Ltd
Priority date: 2020-08-25
Filing date: 2020-08-25
Publication date: 2022-03-02
Also published as: GB202013260D0

Abstract

A method of forming a drilling 32 in a common rail housing 22 for an internal combustion engine to provide a communication path between a rail volume 24 defined along a longitudinal axis (A-A, Fig 3) and an injector cavity 26. The method comprises steps of inserting a machining tool 30 into the injector cavity along a longitudinal axis (B-B, Fig 3) of the injector cavity and translated the machine tool along a drilling axis C-C perpendicular to the longitudinal axis (A-A). A drilling operation is performed as the machining tool is translated along the drilling axis to bring the injector cavity into communication with the rail volume via the drilling. Preferably the machining tool is an electro chemical machining tool which may comprise a support 30a and a cathode 30b, the method comprises inserting the electro-chemical machining tool into the injector cavity so that the support extends along the injector cavity axis and until the cathode aligns with the drilling axis, translating the cathode along the drilling axis and supplying an electrical current to the machining. A common rail housing and common rail housing for a gasoline injection engine are also claimed.

Description

COMMON RAIL HOUSING AND

A METHOD OF FORMING A DRILLING IN A COMMON RAIL HOUSING

TECHNICAL FIELD

The present disclosure relates to a common rail housing and to a method of providing a drilling in a common rail housing. In particular, but not exclusively, the invention relates to a common rail housing for use in an internal congestion engine, particularly a gasoline direct injection (GDI) engine.

BACKGROUND OF THE INVENTION

Gasoline direct injection (GDI) engines inject fuel at high pressure directly into the cylinders of the engine. The fuel injectors of GDI engines are typically connected to a common rail. The common rail comprises a rail housing in the form of a tubular body that defines a high pressure fuel reservoir, or rail volume, from which fuel is supplied to the injectors. The common rail enables fuel to be supplied to the injectors at a controlled and stable pressure and helps to damp oscillations in fuel pressure within the fuel system.

The injectors are typically mounted on the rail housing, one per cylinder of the engine. In a four cylinder engine, for example, four injectors are mounted along the rail housing with each being received in an associated injector cavity or recess provided in the rail housing.

Figure 1 shows a section view of the rail housing 10 at the position of one of the injectors (the injectors are not shown in Figure 1). The rail housing 10 defines the rail volume 12 which has a circular cross section and communicates with a cavity 14 for the injector via an internal drilling portion 16. The internal drilling portion 16 is formed by introducing a machining tool (not shown) to the rail housing 10 from the left hand side of the rail housing (in the illustration shown) and machining through the rail housing 10 to initially form an outer drilling portion 18 which communicates with the rail volume 12. The machining tool passes through the rail volume 12 and onwards through the rail housing 10 until it intercepts the injector cavity 14 perpendicularly, creating the inner drilling portion 16. It is then necessary to provide a plug or seal (not shown) for the outer drilling portion 18 to prevent leakage of fuel from the rail volume 12 through this route.

The need to provide the plug or seal prevents an inconvenience in the manufacturing process. Also due to the relatively high pressure of fuel that is contained within the rail volume, the seal is not always effective so that leakage can occur to the detriment of performance.

As an alternative to the arrangement shown in Figure 1, another known technique involves introducing a machining tool 19 into the injector cavity 14 at an angle to the longitudinal axis of the cavity 14. However, for many rail configurations it is not possible to provide a steep enough angle for the machining tool (as shown in Figure 2) so that the required position for the drilling 16 between the injector cavity 14 and the rail volume 12 is not accessible by the machining tool. Thus, this solution has limitations and can only be used for a limited number of injector/rail configurations.

It is an aim of the present invention to address one or more of the disadvantages associated with the prior art.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention there is provided a method of forming a drilling in a common rail housing for an internal combustion engine to provide a communication path between a rail volume defined within the common rail housing and an injector cavity defined within the common rail housing, the injector cavity being arranged to receive a fuel injector, in use, and the rail volume being arranged to receive pressurised fuel, in use, the method comprising; in an initial step, inserting a machining tool into the injector cavity along a longitudinal axis of the injector cavity; in a subsequent step to the initial step, translating the machining tool along a drilling axis, wherein the drilling axis is perpendicular to the longitudinal axis of the injector cavity; and performing a drilling operation as the machining tool is translated along the drilling axis to bring the injector cavity into communication with the rail volume via the drilling.

In embodiments, the longitudinal axis of the injector cavity and the drilling axis are aligned in the same plane.

The machining tool is preferably an electro chemical machining tool.

The electro chemical machining tool may comprise a support and a cathode, the method comprising inserting the electro-chemical machining tool into the injector cavity so that the support extends along the injector cavity axis and until the cathode aligns with the drilling axis, translating the cathode along the drilling axis and supplying an electrical current to the machining tool to perform the drilling operation at least during part of said translation.

In one embodiment, the method may be performed on a forged common rail housing.

The method may be used to form a plurality of drillings within the common rail housing, the rail housing comprising a plurality of injector cavities configured to receive a respective injector of the engine, in use, each drilling providing a communication path between the rail volume and an associated one of the injector cavities, the method comprising, in the initial step, inserting one of a plurality of machining tools into a respective one of the injector cavities along a longitudinal axis of a respective injector cavity and, in the subsequent step, translating each machining tool along a drilling axis of an associated one of the drillings and performing a drilling operation as the machining tools are translated along the respective drilling axis so as to bring each injector cavity into communication with the rail volume via the associated one of the drillings.

On one example, the subsequent step may be carried out simultaneously for each of the plurality of machining tools.

In another example, the subsequent step may be carried out for each machining tool, one at a time.

In another embodiment, the method may be used to form a plurality of drillings within the common rail housing, the rail housing comprising a plurality of injector cavities each configured to receive a respective injector of the engine, in use, each drilling providing a communication path between the rail volume and an associated one of the injector cavities, the method comprising, in the initial step, inserting the machining tool into one of the injector cavities and translating the machining tool along the drilling axis of an associated one of the drillings to perform the drilling operation as the machining tool is translated along the respective drilling axis to form an associated one of the plurality of drillings, and moving the machining tool along the longitudinal axis of the rail volume and repeating the initial and subsequent steps for each injector cavity to form the plurality of drillings one at a time.

According to a second aspect of the invention, there is provided a common rail housing for an internal combustion engine, the common rail housing comprising a rail volume defined within the common rail housing along a longitudinal axis, the rail volume having an internal wall, an injector cavity defined within the common rail housing along a longitudinal axis of the injector cavity, the injector cavity being configured to receive a fuel injector, in use, and a drilling providing a communication path between the rail volume and the injector cavity, the internal wall having a wall opening at the end of the drilling remote from the injector cavity, where the drilling communicates with the rail volume, wherein the drilling intersects the rail volume perpendicular to the longitudinal axis of the rail volume and wherein the internal wall is closed in the region opposite the wall opening.

The common rail housing may be suitable for use in a gasoline injection engine.

According to a further aspect of the present invention there is provided an internal combustion engine comprising the common rail housing of the second aspect.

Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and/or features of any embodiment can be combined in any way and/or combination, unless such features are incompatible.

BRIEF DESCRIPTION OF THE DRAWINGS

The prior art has been described with reference to the following figures: Figure 1 is a section view of a common rail of the prior art to illustrate a drilling which provides communication between an injector cavity and a rail volume for fuel, and Figure 2 is a cross section of an alternative common rail of the prior art to illustrate difficulties in using a machining tool inserted through the injector cavity to form a drilling which provides communication between an injector cavity and a rail volume for fuel.

One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figures 3 and 4 are perspective views of a common rail housing and a machining tool which is used to provide a drilling in the common rail housing, in accordance with a method of one embodiment of the invention; Figure 5 is an enlarged perspective view of the common rail housing in Figures 3 and 4; Figure 6 is a perspective view of the common rail housing in Figures 3 to 5, with the machining tool performing a further step of the method; Figure 7 is an enlarged perspective view of the common rail housing in Figure 6; Figure 8 is an enlarged perspective view of the common rail housing in Figures 6 and 7, from a different angle; and Figure 9 is a cut away view of the full length of the common rail housing in Figures 3 to 8.

DETAILED DESCRIPTION

Figure 3 schematically illustrates a portion of a common rail assembly, referred to generally as 20, for a gasoline direct injection (GDI) engine according to one embodiment of the present invention.

The common rail assembly 20 includes a common rail housing 22 which is provided with a longitudinal drilling, shown in the figure to have a circular cross section, to define a rail volume 24 defined along a longitudinal rail axis A-A. The rail housing 22 is also provided with a plurality of injector cavities, in a similar way to the prior art. Only one injector cavity 26 is shown in Figure 3 but in practice several such cavities are provided along the axial length of the rail housing 22, each one for receiving a respective injector (not shown) associated with a different cylinder of the engine with which the common rail assembly 20 is used. The injector cavity 26 is provided through an elongate portion 28 of the rail housing 22 which forms an integral part of the rail housing 22 and which extends substantially perpendicularly to the longitudinal axis A-A of the rail housing 22. The injector cavity 26 has a longitudinal axis B-B which is thus perpendicular to the longitudinal axis A-A of the rail volume 24. In use, when the injectors are assembled into their associated injector cavity 26, each injector aligns along the longitudinal axis B-B of the associated injector cavity.

As described previously, it is necessary for each injector cavity 26 to be brought into communication with the rail volume 24 to allow fuel within the rail volume 24 to be delivered to the associated injector. To this end, a drilling (not shown in Figure 3) needs to be formed between the rail volume 24 and each injector cavity 26.

The drilling method of the invention relies on an electro-chemical machining process to form the required drilling. Electro-chemical machining is a known process which relies on an anodic metal dissolution process to shape, form and/or drill through a metal work product. In a dynamic ECM process, a cathode of the ECM tool is moved with constant speed into a component to provide good finishing results. The process is known for use especially with complex shapes that are difficult to machine using more conventional machining methods.

Referring also to Figure 4, in a first step of the method of forming the drilling, a machining tool in the form of an electro-chemical machining (ECM) tool 30 is brought towards and then introduced into the injector cavity 26 along its longitudinal axis B-B. In the drilling method of the invention, the ECM machining tool 30 includes an elongate support 30a which carries a cathode 30b at one end and a projection 30c at the other end. During the drilling process, the projection 30c is controlled by means of a control assembly (not shown) which controls the introduction of the machining tool 30 into the injector cavity 26.

As shown in Figure 4, in a second step of the process, the machining tool 30 is inserted fully into the injector cavity 26 so that the cathode 30c is aligned along a drilling axis C-C for the drilling to be formed. The drilling axis C-C is perpendicular to the longitudinal axis B-B of the injector cavity 26 and the axes (CC and B-B) are aligned in the same plane.

As a third step in the process, the cathode 30c is activated and the machining tool is translates so that the cathode moves along the drilling axis C-C, in a direction perpendicular to the longitudinal axis B-B of the injector cavity 26. As the ECM machining tool 30 is activated and through the translation, the cathode 30b drills into the rail housing 22, through the wall of the injector cavity 26 and towards the rail volume 24. In Figure 4 the initial formation of the drilling 32 can be seen, the drilling 32 communicating with the injector cavity 26 at its lower end. At this stage, the drilling 32 is partially formed in the rail housing 22, in the region between the injector cavity 26 and the rail volume 24, as can be seen clearly in the enlarged view of Figure 5.

The machining tool 30 continues to translate along the drilling axis C-C and machining continues until the cathode 30b breaks through the internal wall of the rail volume 24, completing the drilling process and bringing the injector cavity 26 into communication with the rail volume 24 via the drilling 32, as shown in Figures 6, 7 and 8. Once the drilling 32 is fully formed and the necessary communication path has been formed between the injector cavity 26 and the rail volume 24, the machining tool 30 is translated in reverse along the drilling axis C-C and is removed from the injector cavity 26.

In contrast to the prior art solution shown in Figure 1, the benefit of the method of the invention is that, for any one injector, there is only one point of opening into the rail volume 24 at the position of the drilling 32, and there is no opening in the portion of the wall of the rail volume opposite the drilling 32, as in Figure 1 for example. Any risk of leakage from the rail volume 24 is therefore avoided.

In contrast to the prior art solution of Figure 2, the method can be used for any rail configuration, regardless of the position of the injector cavity 26 relative to the rail volume 24 because the machining tool 30 can be introduced into the injector cavity 26 in line with the axis B-B. This enables the drilling 32 to be formed perpendicular to the longitudinal axis of the rail volume 24 which has benefits in terms of product life and robustness.

Figure 9 shows the full length of the common rail housing 22, including four injector cavities 26a, 26b, 26c, 26d at regularly spaced locations along the rail axis A-A. Each injector cavity 26a, 26b, 26c, 26d is of the same form as that described previously with reference to Figures 3 to 8 and includes an associated drilling 32a, 32b, 32c, 32d through the rail housing 22 which communicates with the rail volume 24 to provide communication with the associated injector cavity 26a, 26b, 26c, 26d, respectively. In addition to the injector cavities 26a, 26b, 26c, 26d, the rail housing 22 includes four mounting portions 34a, 34b, 34c, 34d, one associated with each of the injector cavities, which are used to mount the rail housing 22 to the engine via bolts (not shown) which extend through an associated bolt hole within each mounting portion 34a, 34b, 34c, 34d.

The method of the invention provides the further benefit that it can be readily adapted so that each of the four drillings 32a, 32b, 32c, 32d is formed simultaneously with the drillings for the other injector cavities. A respective machining tool (not shown in Figure 9) is inserted into the associated injector cavity 26a, 26b, 26c, 26d, along its longitudinal axis, at the same time as the other machining tools until the cathode of each tool aligns with the drilling axis of the associated drilling 32a, 32b, 32c, 32d to be formed. The cathodes are then activated either simultaneously or one at a time to form the required drillings. Alternatively, a separate machining tool may be used to form each drilling 32a, 32b, 32c, 32d, either simultaneously or one at a time. Each machining tool is controlled via software running on a controller, with each machining tool being controlled independently of the other machining tools.

In an alternative method, one machining tool may be used to form all of the drillings 32a, 32b, 32c, 32d by first introducing the machining tool into an end one of the injector cavities (e.g. injector cavity 26a) and forming this drilling 32a first, then removing the machining tool from that injector cavity and moving it along the longitudinal axis A-A of the rail volume 24, before inserting the machining tool 30 into the adjacent injector cavity (e.g. injector cavity 26b). Once the drilling 32b is formed to communicate with the second injector cavity 26b the machining tool is removed from the second injector cavity 26b, and the process continues until all four drillings 32a, 32b, 32c, 32d have been formed, one at a time.

The method lends itself to the formation of drillings in a forged rail housing 22, but equally may be applied to cast housings. It will also be appreciated that although the invention has been described in the context of a common rail housing for a GDI engine, the method is also applicable to a common rail housing for us in compression ignition (diesel) internal combustion engines.

Other variations of the invention will also be apparent to the skilled person and the aforementioned examples are not intended to be limiting.

List of reference numbers: 10-common rail housing (prior art) 12-rail volume (prior art)

14-injector cavity (prior art)

16-inner drilling portion (prior art)

18-outer drilling portion (prior art)

19-machining tool (prior art)

20-common rail assembly 22-common rail housing 24-rail volume 26, 26a, 26b, 26c, 26d -injector cavity 30-machining tool 30a -support of machining tool 30b -cathode of machining tool 30c -projection of machining tool 32, 32a, 32b, 32c, 32d -drilling 34a, 34b, 34c, 34d -mounting portion of rail A-A -longitudinal axis of rail volume B-B -longitudinal axis of injector cavity C-C -longitudinal axis of drilling

Claims

CLAIMS: 1. A method of forming a drilling (32; 32a, 32b, 32c, 32d) in a common rail housing (22) for an internal combustion engine to provide a communication path between a rail volume (24) defined along a longitudinal axis (A-A) of the common rail housing (22) and an injector cavity (26; 26a, 26b, 26c, 26d) defined within the common rail housing (22), the injector cavity (26; 26a, 26b, 26c, 26d) being arranged to receive an injector, in use, and the rail volume (24) being arranged to receive pressurised fuel, in use, the method comprising: in an initial step, inserting a machining tool (30) into the injector cavity (26; 26a, 26b, 26c, 26d) along a longitudinal axis (B-B) of the injector cavity (26; 26a, 26b, 26c, 26d); in a subsequent step to the initial step, translating the machining tool (30) along a drilling axis (C-C) of the drilling (32; 32a, 32b, 32c, 32d), wherein the drilling axis (C-C) is perpendicular to the longitudinal axis (A-A) of the injector cavity (26; 26a, 26b, 26c, 26d); and performing a drilling operation as the machining tool (30) is translated along the drilling axis (C-C) to bring the injector cavity (26; 26a, 26b, 26c, 26d) into communication with the rail volume (24) via the drilling (32; 32a, 32b, 32c, 32d).
2. The method as claimed in claim 1, wherein the longitudinal axis (B-B) of the injector cavity (26; 26a, 26b, 26c, 26d) and the drilling axis (C-C) are aligned in the same plane
3. The method as claimed in claim 1 or claim 2, wherein the machining tool (30) is an electro chemical machining tool.
4. The method as claimed in claim 3, wherein the electro chemical machining tool (30) comprises a support (30a) and a cathode (30b), the method comprising inserting the electro-chemical machining tool (30) into the injector cavity (26; 26a, 26b, 26c, 26d) so that the support (30a) extends along the injector cavity axis and until the cathode (30b) aligns with the drilling axis (C-C), translating the cathode (30b) along the drilling axis (C-C) and supplying an electrical current to the machining tool (30) to perform the drilling operation at least during part of said translation.
5. The method as claimed in any of claims 1 to 4, wherein the method is performed on a forged common rail housing (22).
6. The method as claimed in any of claims 1 to 5, for forming a plurality of drillings (32a, 32b, 32c, 32d) within the common rail housing (22), the rail housing comprising a plurality of injector cavities (26a, 26b, 26c, 26d) configured to receive a respective injector of the engine, in use, each drilling (32a, 32b, 32c, 32d) providing a communication path between the rail volume (24) and an associated one of the injector cavities (26a, 26b, 26c, 26d), the method comprising; in the initial step, inserting one of a plurality of machining tools (30) into a respective one of the injector cavities (26a, 26b, 26c, 26d) along a longitudinal axis (B-B) of a respective injector cavity (26a, 26b, 26c, 26d) and, in the subsequent step, translating each machining tool along a drilling axis (C-C) of an associated one of the drillings (32a, 32b, 32c, 32d) and performing a drilling operation as the machining tools (30) are translated along the respective drilling axis (C-C) so as to bring each injector cavity (26a, 26b, 26c, 26d) into communication with the rail volume (22) via the associated one of the drillings (32a, 32b, 32c, 32d).
7. The method as claimed in claim 6, wherein the subsequent step is carried out simultaneously for each of the plurality of machining tools.
8. The method as claimed in claim 6, wherein the subsequent step is carried out for each machining tool, one at a time.
9. The method as claimed in any of claims 1 to 5, for forming a plurality of drillings (32a, 32b, 32c, 32d) within the common rail housing (22), the rail housing comprising a plurality of injector cavities (26a, 26b, 26c, 26d) each configured to receive a respective injector of the engine, in use, each drilling (32a, 32h, 32c, 32d) providing a communication path between the rail volume (24) and an associated one of the injector cavities (26a, 26b, 26c, 26d), the method comprising; in the initial step, inserting the machining tool (30) into one of the injector cavities (26a, 26b, 26c, 26d) and translating the machining tool along the drilling axis (C-C) of an associated one of the drillings (32a, 32b, 32c, 32d) to perform the drilling operation as the machining tool (30) is translated along the respective drilling axis (C-C) to form an associated one of the plurality of drillings (32a, 32b, 32c, 32d), and moving the machining tool (30) along the longitudinal axis (A-A) of the rail volume (24) and repeating the initial and subsequent steps for each injector cavity (26a, 26b, 26c, 26d) to form the plurality of drillings one at a time.
10. A common rail housing (22) for an internal combustion engine, the common rail housing (22) comprising; a rail volume (24) defined within the common rail housing (22) along a longitudinal axis (A-A), the rail volume (24) having an internal wall, an injector cavity (26; 26a, 26b, 26c, 26d) defined within the common rail housing (22) along a longitudinal axis (B-B) of the injector cavity, the injector cavity being configured to receive a fuel injector, in use, and a drilling (32; 32a, 32b, 32c, 32d) providing a communication path between the rail volume (24) and the injector cavity (26; 26a, 26b, 26c, 26d), the internal wall having a wall opening at the end of the drilling (32; 32a, 32b, 32c, 32d) remote from the injector cavity (26; 26a, 26b, 26c, 26d), where the drilling (32; 32a, 32b, 32c, 32d) communicates with the rail volume (24), wherein the drilling (32; 32a, 32b, 32c, 32d) intersects the rail volume (24) perpendicular to the longitudinal axis (A-A) of the rail volume (24) and wherein the internal wall is closed in the region opposite the wall opening.
11. The common rail housing (22) as claimed in claim 10, for a gasoline injection engine.