EP3502461A1

EP3502461A1 - A fuel delivery passage for a fuel injection system and a method of manufacturing a fuel delivery passage

Info

Publication number: EP3502461A1
Application number: EP17208810.6A
Authority: EP
Inventors: Giandomenico Serra; Gisella Di Domizio; Marco Pasquali
Original assignee: Continental Automotive Technologies GmbH
Current assignee: Vitesco Technologies GmbH
Priority date: 2017-12-20
Filing date: 2017-12-20
Publication date: 2019-06-26

Abstract

A fuel delivery passage (8) for a fuel injection system for an internal combustion engine is provided. The passage (8) includes a fuel inlet (4) adapted to receive fuel from a high-pressure source and at least one fuel outlet (6) adapted to be connected to an inlet port of a fuel injector. The passage (8) comprises at least one channel (12) having a tortuous path (22) for the fuel flow. At least one section (16) of the channel (12) varies in cross-sectional area over a predetermined length.

Description

The present disclosure relates to a fuel delivery passage for a fuel injection system for an internal combustion engine. The disclosure relates, particularly but not exclusively, to a fuel delivery passage for incorporation in a main gallery of a fuel injection system for a multicylinder direct injection internal combustion engine.
In known arrangements, the main gallery comprises an elongate reservoir for fuel in which the fuel is supplied by a high pressure fuel pump and outlets for supplying fuel to a fuel injector for directing fuel directly into each cylinder of the engine. The volume of fuel in the reservoir is intended to damp out fluctuations in the pressure of the fuel supplied by the pump so that the pressure at each outlet is equal and substantially constant.
In the known arrangements, the main gallery is typically a substantial generally tubular element which has to be strong enough to cope with the stresses of the load applied to the main gallery by the high pressure of fuel in the reservoir. As a result, the main gallery tends to be heavy and costly because of the amount of material used in its construction.
The present disclosure seeks to provide a fuel supply system which overcomes or mitigates the disadvantages of the known main galleries.
The present disclosure shows a fuel delivery passage for a fuel injection system for an internal combustion engine, the passage including a fuel inlet adapted to receive fuel from a high-pressure source, and at least one fuel outlet adapted to be connected to an inlet port of a fuel injector. The passage comprises at least one channel having a tortuous path for the fuel flow. At least one section of the channel varies in cross-sectional area over a predetermined length of the channel.
The main gallery or fuel rail has a fuel delivery passage that may be considered to have an alveolar design or structure. A tortuous path for the fuel flow has two or more deviations from a straight line and may have a winding form. The tortuous path for the flow of fuel provided by the channel in combination with the variation in cross-sectional area in at least one section of the channel provides a fuel delivery passage with which variations of the pressure of the fuel delivered to the fuel outlet and consequently to the fuel injector are reduced. The hydraulic behaviour of the fuel can be improved by use of an appropriately designed alveolar structure for the fuel delivery passage.
The cross-sectional area may be increased or reduced for a predetermined length of the channel. The cross-sectional area may be increased or reduced for a predetermined length of the section of the channel compared to the cross-sectional area of the channel adjacent the section or compared to the cross-sectional area of the channel in an adjoining portion of the section. This form makes use of Bernoulli's principle that an increase in the cross-sectional area of a pipe causes a decrease in flow rate and an increase in pressure of a fluid flowing in the pipe and vice versa. Consequently, the pressure of the fuel can be locally increased or decreased by selection of an increased or decreased cross-sectional area of one or more sections of the channel or channels of the passage.
The tortuous path for the flow of fuel may be provided by forming the channel such that at least one portion of the channel extends at an inclined angle to the entrance of the channel and/or to the exit of the channel provide a winding or twisting path for the fuel flow. The longest path of fluid through a curved pipe has the highest pressure and the lowest speed. The shortest path through the curve has the lowest pressure and the highest speed. In other words, when the path of a fluid in steady-state flow bends, the pressure on the outside of the bend is always higher than the pressure on the inside of the bend. The tortuous path provided by the channel provides a mechanism by which the pressure and speed of the fuel can be varied, also within the cross-sectional area of the channel.
In some embodiments, a plurality of sections with a varying cross-sectional area are spaced along the length of the channel. This arrangement may be used to further locally control the pressure and flow rate of the fuel within the channel. The sections of the channel or channels may each have a different cross-sectional area and shape and length in the direction of flow of fuel.
In some embodiments, the section comprises a chamber and a pipe section, the chamber having a larger cross-sectional area than the pipe section. The chamber may be substantially spherical, for example. Each chamber may include at least two openings, one connected to the pipe section and one connected to a further portion of the channel, for example a further pipe section. The pipe section may provide the inlet or outlet to the chamber. The openings may be arranged at an including angles to one another and provide a tortuous path for the fuel.
In some embodiments, the chamber includes more than two openings and may have two or more inlets and two or more outlets. This arrangement may be used to provide two or more alternative paths for the fuel. This arrangement may also be used to provide two or more paths which extend in different directions and which have different effects on the pressure and flow rate of the fuel as well as the direction of flow of the fuel.
The fuel delivery passage may deliver fuel to a single outlet, for example for an internal combustion engine having a single fuel injector. In some embodiments, the passage has a plurality of fuel outlets each being adapted to be connected to an associated inlet port of a fuel injector. The passage also includes at least one channel for each fuel outlet. In some embodiments, two or more channels extend into a fuel outlet. The pressure of the fuel in each channel may be different so that this arrangement may be used to deliver fuel to the fuel outlet with a spatially locally variable pressure or at a pressure averaged over the pressure delivered by each channel.
In some embodiments, the passage comprises a plurality of said channels that are interconnected at predetermined points and form a labyrinth of channels. The labyrinth of channels provides a single passage with which the pressure and flow rate of the fuel locally varies as a result of the tortuous or bending paths provided by the labyrinth and as a result of the local variation in the cross-section of the channels. The labyrinth of channels provides a plurality of fuel delivery paths from the fuel inlet to an output port of a channel associated with a fuel outlet. The number of channels may also be selected in order to optimise the hydraulic behaviour of the fuel delivery passage.
The shape of the channels and the overall passage may be arranged to damp out fluctuations in the flow and pressure of fuel to ensure that the pressure of fuel at each outlet is at the required level and with the minimal variation in the actual pressure.
In an embodiment, a main gallery is provided that comprises a fuel delivery passage according to any one of the embodiments described above. The main gallery may include a main body or structural body that provides the passage. In some embodiments, the main gallery may include a massive part whereby the channel or channels providing the passage are formed in the massive part such that the outer contour of the main gallery differs from the outer contour of the passage. In some embodiments, the main body is provided by support walls having an outer contour which substantially corresponds to the outer contour of the passage. In some embodiments, the main body includes a variable wall thickness such that the strength of the main body can be locally varied. For example, an area of the main body which is to have a higher strength or robustness, for example an area that supports a fixture, may have an increased wall thickness compared to an area of the main body which may have a lower strength.
In an embodiment, a fuel rail assembly comprising a main gallery according to one of the embodiments described herein is provided. The fuel rail assembly may also include one or more fuel outlets in fluid communication with the passage and one or more fixtures for mounting the fuel rail assembly to a vehicle, for example an engine block of the vehicle.
A method of fabricating a main gallery of a fuel delivery system for an internal combustion engine is provided, the method comprising building up a main body having a fuel delivery passage according to any one of the embodiments described herein layer by layer.
Additive manufacturing techniques may be used to build up the main body layer by layer. For example, the main body may be built up layer by layer using 3D (Three-dimensional) printing or Powder Bed Fusion or Directed Energy Deposition. The main body may be built up layer by layer by movement of the inkjet print head, laser or electron beam controlled according to a three dimensional model of the main body having the fuel delivery passage.
Embodiments of the present disclosure will now be described by way of example with reference to the accompanying schematic drawings, in which:

Figure 1: illustrates a cross-sectional view through a schematic arrangement of a main gallery with a fuel delivery passage,
Figure 2: illustrates a view of the fuel delivery passage fluid domain and fuel inlet, and
Figure 3: illustrates the complete fuel rail length of a fuel delivery passage fluid domain containing a multiplicity of channels.

Figure 1 discloses a cross-section through a schematic arrangement of a main gallery 2 for a fuel injection system of a direct injection internal combustion engine. The main gallery 2 provides a reservoir for fuel which is supplied to the fuel injectors.
Figure 1 illustrates a portion of a main gallery 2 having a fuel inlet port 4 adapted to be connected to a high pressure pump (not shown) through which fuel is supplied to the main gallery 2. The main gallery 2 has one or more outlet ports 6 adapted to receive an inlet port of a fuel injector (not shown).
The main gallery 2 has a fuel delivery passage 8 which provides a reservoir of fuel for the fuel injector or injectors. The fuel delivery passage 8 is formed so as to provide a multiplicity of channels 12. At least one of the channels 12 provides a tortuous path for the fuel. In other words, the path for the fuel provided by the channel 12 has two or more deviations from a straight line and may have a winding form. At least some of the channels 12 of the fuel delivery passage 8 are in fluid communication and provide a labyrinth passage having a plurality of possible paths 22 for the flow of fuel.
The fuel delivery passage 8 comprises an inlet chamber 10 adjacent the inlet port 4 which leads to the multiplicity of channels 12, of which some lead into one of the outlet ports 6. In the cross-sectional view of figure 1, four channel outlets 12 are in fluid communication with the inlet port 4 and two channels 12 are in fluid communication with the outlet port 6. However, the number of channels 12 in fluid communication with the inlet port 4 and outlet port 6 is not limited to four and two, respectively, and may vary.
The channels 12 of the fuel delivery passage 8 provide a labyrinth passage which has a variable cross-section along its length. In the particular example illustrated in figure 1, the channels comprise pipe sections 14 leading to enlarged portions providing chambers 16 having a cross-sectional area that is greater than that of the adjacent pipe sections 14. In this particular embodiment, the enlarged portions providing the chambers 16 are substantially spherical.
Each of the chambers 16 includes at least two openings 16a, 16b, providing one or more potential inlets and one or more potential outlets 18 extending in predetermined directions into a further pipe section 14 which continues the channel 12 of the passage 8. The openings 16a, 16b may be arranged in the chamber 16 so as to provide a bent path for the flow of fuel and together with further chambers 16 and pipe sections 14 a tortuous path 22 for the fuel.
The pipe sections 14 and chambers 16 can be connected to form a convoluted labyrinth for the channel or channels 12 which finally leads to the output port 6. The tortuous path 22 provided by the convoluted labyrinth and changes in the cross-sectional area of the channel 12 provided by the chambers 16 damp out pressure fluctuations of the fuel from the fuel pump and serve to ensure that the fuel arriving at the outlet port 6 is at the desired pressure and has a minimal variational fluctuation in the flow and/or pressure.
In some embodiments, fuel supplied to the outlet port 6 may take one of a number of different paths 22 through the labyrinth passage 8 due to the connections between the channels 12.
Referring now to figure 2, there is shown, schematically, the volume of the fuel delivery passage 8 in which fuel can flow and which provides the reservoir of fuel that is supplied to the fuel injectors. Figure 2 can be considered to illustrate a positive representation of the negative or hollow portion of the main gallery 2 which provides the passage 8 without the main body 24 of the main gallery 2. In this particular arrangement, it can be seen that the fuel in the inlet chamber 10 passes to a plurality of outlets 20 formed by pipe sections 14 forming a multiplicity of channels 12 into a single outlet port 6. In this arrangement, the chambers 16 are substantially spheres and have a plurality of inlets 14a and a plurality of outlets 14b. In this way, a plurality of channels 12 are formed interlinked in places by pipes 14 to form a labyrinth from the inlet chamber 10 which ultimately leads to four channel outlets 20 each connected to an associated one of the outlet ports 6 leading to the injectors.
However, the arrangement is not limited to four channel outlets 20 as illustrated in figure 2. One or more channel outlet ports 20 may be connected to an associated one of the outlet port 6. The length of the various pipe sections 14 and the cross-sectional area, or diameter of volume of the various chambers 16 can be substantially the same or can vary. In some embodiments, the position of the pipe section 14 and chamber 16 with respect to the outlet port 6 and/or with respect to the fuel inlet port 4 may determine its relative its dimensions. For example, chambers 16 which are located at a smaller distance from the outlet port 6 may be smaller than the chambers 16 which are located as a larger distance with respect to the same outlet port 6.
Figure 3 illustrates a view of a fuel delivery passage 8 showing one outlet port 6 intermediate the length of the fuel delivery passage 8. The passage 8 is formed of a multiplicity of pipe sections 14 and spheres providing chambers 16 which are linked together by pipe sections 14 to perform a complex labyrinth defining at least one channel 12. Some spheres 16 have four openings 16a, 16b and may be connected to provide at least one inlet, the remainder being outlets 18 in the direction of the flow of fuel. Some spheres 16 may have fewer openings 16a, 16b, for example two openings, or more than four openings. The diameter of the spheres may vary.
Although described as spheres 16 and pipe sections 14, it will be understood that the enlarged sections of the passage 8 or chambers 16 need not be spherical but could be just an enlarged section of pipe of a predetermined length and the cross-sectional shape of the individual pipes and enlarged sections may be varied to provide the precise guidance to the fuel flow required. Similarly, certain sections may be formed with a reduced cross-sectional area as required by the desired flow pressure patterns through the passage.
The main gallery 2 may be formed from a metal or alloy. The main gallery 2 with its fuel delivery passage 8 may be fabricated using additive manufacturing techniques. In additive manufacturing, a three-dimensional object is built up layer by layer in contrast to subtraction techniques in which a portion of a work piece is removed to form an object with the desired form. Additive manufacturing techniques may be conveniently used to produce a labyrinth of channels 14.
An example of an additive manufacturing technique is 3D printing in which material is deposited suing a moving inkjet print head. A further example is powder bed fusion in which thermal energy from a laser of electron beam is used to selectively fuse powder in a powder bed. A further example is directed energy deposition in which thermal energy, for example from a laser, is used to fuse materials by melting them as they are deposited. The movement of the inkjet print head, laser or electron beam is computer controlled to build up an object, in this case the main body and the passage 8, layer by layer according to a three-dimensional model, such as a CAD (Computer Aided Design) model, of the main body and the passage 8.
In some embodiments, the passage 8 may be fabricated using two or more preformed parts including one or more apertures that are joined with a fluid tight seal to produce a tortuous path. One or more of the preformed parts may include a variation in cross-sectional area along its length.
In some embodiments, the outer contour of the main gallery 2 has a diameter or outer contour that varies along its length. For example, the main body 24 of the passage 8 may have localised thickness variations. For example, in regions which do not require such a high strength the wall thickness may be less that in regions which require a higher strength. This embodiment may be used to reduce the weight of the main gallery 2 and reduce material usage and/or to produce a localised increased strength.

Claims

A fuel delivery passage (8) for a fuel injection system for an internal combustion engine, the passage (8) including a fuel inlet (4) adapted to receive fuel from a high-pressure source, and at least one fuel outlet (6) adapted to be connected to an inlet port of a fuel injector,
wherein the passage (8) comprises at least one channel (12) having a tortuous path (22) for the fuel flow and at least one section (16) of the channel (12) varies in cross-sectional area over a predetermined length.
A fuel delivery passage (8) according to claim 1, wherein the cross-sectional area is increased or reduced for a predetermined length of the channel (12).
A fuel delivery passage (8) according to claim 1 or 2, wherein a plurality of said sections (16) are spaced along the length of the channel (12).
A fuel delivery passage (8) according to claim 3, wherein the sections (16) each have a different cross-sectional area and shape and length in the direction of flow of fuel.
A fuel delivery passage (8) according to any one of the preceding claims, wherein the section comprises a chamber (16) and a pipe section (14), the chamber (16) having a larger cross-sectional area than the pipe section (14).
A fuel delivery passage (8) according to any one of the preceding claims, wherein the chamber (16) is substantially spherical.
A fuel delivery passage (8) according to any one of the preceding claims, wherein the passage (8) has a plurality of fuel outlets (6) each being adapted to be connected to an associated inlet port of a fuel injector and at least one channel (12) for each fuel outlet (6).
A fuel delivery passage (8) according to claim 7, wherein two or more channels (12) extend to a fuel outlet (6).
A fuel delivery passage (8) according to any one of the preceding claims, wherein the passage (8) comprises a plurality of said channels (12) that are interconnected at predetermined points and form a labyrinth of channels.
A fuel delivery passage (8) according to claim 9, wherein the labyrinth of channels (12) provides a plurality of fuel delivery paths (22) from the fuel inlet (4) to an output port (20) of a channel (12) associated with a fuel outlet (6).
A fuel delivery passage (8) according to any one of the preceding claims, wherein the shape of the channels (12) and the overall passage (8) are arranged to damp out fluctuations in the flow and pressure of fuel to ensure that the pressure of fuel at each outlet (6) is at the required level and with the minimal variation in the actual pressure.
A main gallery (2) comprising a fuel delivery passage (8) according to any one of claims 1 to 11.
A fuel rail assembly comprising a main gallery (2) according to claim 12.
A method of fabricating a main gallery (2) of a fuel delivery system for an internal combustion engine, comprising:
building up a main body (24) having a fuel delivery passage (8) according to any one of claims 1 to 10 layer by layer.
A method according to claim 13, wherein the main body (24) is built up layer by layer by 3D printing or Powder Bed Fusion or Directed Energy Deposition.
A method according to claim 13 or claim 14, wherein the main body (24) is built up layer by layer by movement of the inkjet print head, laser or electron beam controlled according to a three dimensional model of the main body (24) having the fuel delivery passage (8).