WO2018158087A1

WO2018158087A1 - Method for manufacturing a fuel distribution and heating unit and fuel distribution and heating unit

Info

Publication number: WO2018158087A1
Application number: PCT/EP2018/053815
Authority: WO
Inventors: Tadeu Miguel Malago Amaral; Edson Valdomiro DE AZEVEDO JUNIOR; Heitor Moreira CAVALHIERI; Fabio Moreira; Fernando JUN YOSHINO
Original assignee: Mahle Metal Leve S/A; Mahle International Gmbh
Priority date: 2017-03-03
Filing date: 2018-02-15
Publication date: 2018-09-07
Also published as: BR102017004261A2

Abstract

The present invention relates to a fuel distribution and heating unit (10) and to the method for manufacturing that unit. The manufacturing method optimizes the time for manufacturing these units and such units may be used, for example, for cold starting, reduction of pollutant gas emissions, amongst other applications in internal combustion engines and motor vehicles. The manufacturing method comprises at least the steps of obtaining a first portion of the fuel distribution and heating unit and overinjecting a second portion of the fuel distribution and heating unit such that it is rigidly attached to the first portion of the fuel distribution and heating unit, the attachment between the first and the second portion of the fuel distribution and heating unit defining an internal region of the unit, comprising a supply gallery (24) connected to a fuel heating region (42) by means of a passage (22), and heated fuel passage channels (81) and an external region of the unit, comprising at least one fuel inlet opening (21), at least one heater housing (25) and at least one heated fuel outlet (31).

Description

"METHOD FOR MANUFACTURING A FUEL DISTRIBUTION AND HEATING UNIT AND FUEL DISTRIBUTION AND HEATING UNIT"

FIELD OF THE INVENTION

[001] The present invention relates to a method for manufacturing a fuel distribution and heating unit and to a fuel distribution and heating unit. The manufacturing method optimizes the time for manufacturing these units and such units may be used, for example, for cold starting, reduction of pollutant gas emissions, amongst other applications in internal combustion engines and motor vehicles.

BACKGROUND OF THE INVENTION

[002] The growing search for cleaner energy sources, in association with increasing demand for less polluting engines, has transformed the development of internal combustion engines. Currently, internal combustion engines use ethanol as a fuel, but persons skilled in the art are aware that satisfactory combustion of ethanol is dependent on its temperature. In this scenario of increasing use of ethanol, and in light of the problems that this fuel presents in terms of combustion at low temperatures, much has been done to develop auxiliary engine-starting systems.

[003] Alert to this situation, companies and researchers have already been developing electric heater solutions in order that the fuel should be heated at least to above its flash-point temperature, thereby providing better engine starting even on cold days. An example of the heating technology used is the heater known as a "glow plug". Originating from applications in diesel vehicles, this type of heater has the form of a metal rod and is placed in the fuel gallery, heating fuel prior to the latter' s injection into the engine or inlet port of the engine.

[004] This heating technology uses a high-temperature heater for rapid heating, which gives rise to the risks of the fuel boiling (if this occurs, vapour is injected instead of liquid fuel, causing engine failure) , overheating, an increase in internal pressures in components, leaks and, in more extreme cases, even fire or the melting of plastic parts. Other fuel heating technologies for cold starting have been created, but in the form of geometric structures and placed differently from the glow plug, some, for example, being incorporated into the fuel injection nozzle. As they have a small area of heat exchange with the fuel, all have hitherto worked at high temperatures and also present the risks of overheating and safety in the case of the glow plug-type heater.

[005] With a view to resolving the drawbacks and disadvantages arising from this cold-starting system, new systems were developed in which the usual heaters are replaced by a heating element of the "PTC thermistor" (positive temperature efficient thermistor) type, in conjunction with a high-efficiency heat exchanger. Such developments are disclosed in documents BR102015030039-5, BR102015024209-3 and

BR102015028621-7. Thus, placed between the inlet and the outlet of the heating device, the fuel enters in contact with the heat exchanger, which emits the received heat from its interior by means of the thermistor. By means of this system, the fuel is rapidly heated, using the low-surface-temperature PTC thermistor, automatically controlled by its inherent semiconductor doping, preventing the fuel exceeding a specified temperature (defined in the doping and method for manufacturing the PTC thermistor) and eliminating the inconveniences that previously arose. It should be noted that, although there are other PTC-type heaters in existence, such technologies, with PTCs on their own and without the use of high-efficiency heat exchangers, also require a high-surface-temperature PTC, which means there is still a need for electronic temperature- control hardware.

[006] The solutions disclosed in documents BR102015024209-3, BR102014023292 -3 and PI 1005341-7 propose the use of a heating element in association with each of the injection nozzles of an internal combustion engine. These solutions involve high energy expenditure since they heat a large mass of fuel. Such systems are also costly in terms of the number of elements and the assembly of those elements.

[007] As seen above, the solutions shown involve the use of a heating system for each injection nozzle, which also makes the systems expensive and difficult to implement on a large scale. Thus, companies have developed systems that use traditional glow plugs inserted in the principal fuel supply gallery.

[008] One example of the use of a glow plug in the fuel gallery may be seen in patent application PI1100311-1, which discloses a fuel gallery provided with a glow plug heating element at each end thereof. Such glow plug elements heat the entire mass of fuel present in the principal supply gallery of the injection nozzles. The applicant for patent application PI1100311-1 uses a common fuel gallery with small adaptations at the ends in order to contain the glow plug elements. Document PI1100311-1 proposes heating the fuel prior to injection, but gives rise to unnecessary energy expenditure since it heats a mass of fuel much greater than that which will be injected in the initial moments of starting the engine. Furthermore, the heating implemented by this document occurs unevenly along the supply gallery since the heater elements are located at the ends of the gallery. Lastly, such a system does not address the thermal insulation of the heated parts. In other words, patent application PI1100311-1 relates to a mere juxtaposition of elements known in the prior art.

[009] Solutions have been developed with a view to reducing the price of fuel heater units, such as that proposed in document BR102016029084-8, which associates a single heater element with more than one fuel injection nozzle. The solution proposed by this document is shown to be suitable in terms of energy consumption and heating efficiency. However, the subject matter proposed by document BR102016029084-8 involves various parts that interact with one another in a complex assembly, the sealing and leaktightness of which require special welding methods. Such methods make manufacture of the product more expensive and may render its marketing non-viable.

[010] Thus, there is clearly a need for a product that is less costly in terms of its manufacture, with a view to making fuel heating and distribution systems more commercially competitive.

OBJECTS AND DESCRIPTION OF THE INVENTION

[011] Thus, an object of the present invention is to optimize the time for manufacturing a fuel distribution and heating unit.

[012] A further object of the present invention is to reduce the cost of manufacture of the fuel heating and distribution unit.

[013] A further object of the present invention is to improve the leaktightness of the heating and distribution unit without making this manufacturing step more expensive. [014] In addition, a further object of the present invention is to reduce the number of heating elements used in a fuel heating and distribution unit.

[015] A further object of the present invention is to make the process of heating fuel prior to starting the engine on colder days safer and more efficient.

[016] In addition, a further object of the present invention is to prevent fuel leaks in the fuel distributor unit.

[017] Leaktightness is an extremely important factor in these components, which operate with flammable fuels under adverse temperature conditions. The prior art, moreover, does not cover a manufacturing method that promotes effective, commercially viable leaktightness.

[018] In addition, the present invention has the advantage of achieving sealing and leaktightness in the heating and distribution unit and, furthermore, eliminating a step in the method for manufacturing said unit .

[019] One or more objects of the present invention mentioned above, inter alia, are achieved by means of a manufacturing method that improves the leaktightness of the heating and distribution unit and reduces the costs and time of production of these items of equipment.

[020] Specifically, the method for manufacturing a fuel distribution unit of the present invention comprises the steps of:

a) obtaining a first portion of the fuel distribution and heating unit; and

b) overinj ecting a second portion of the fuel distribution and heating unit such that it is rigidly attached to the first portion of the fuel distribution and heating unit.

[021] In this method, the attachment between the first and the second portion of the fuel distribution and heating unit defines: - an internal region of the unit, comprising a supply gallery fluidly connected to a fuel heating region by means of a passage, and heated fuel passage channels; and

- an external region of the unit, comprising at least one fuel inlet opening, at least one heater housing and at least one heated fuel outlet.

[022] The manufacturing method also includes the optional step of mounting a partition plate in the first portion of the unit before the step of overinj ecting the second portion of the unit, such that the partition plate separates the first and the second portion in the area of the partition plate or along the partition plate, respectively. To this end said partition plate can abut against the second portion and can be arranged recessed in the first portion, in particular can be embedded in the material of the first portion .

[023] The present invention also provides a distribution and heating unit that comprises:

- a first portion; and

- a second portion rigidly attached to the first portion by means of overinj ection .

[024] The attachment between the first and the second portion of the fuel heating and distribution unit defines :

- an internal region, comprising a supply gallery fluidly connected to a fuel heating region by means of a passage, and heated fuel supply channels; and

- an external region, comprising at least one fuel inlet opening, at least one heater housing and at least one heated fuel outlet channel.

According to a preferred embodiment the at least one fuel inlet opening is fluidly connected to the supply gallery. Additionally, or alternatively, the fuel supply channels are fluidly connected to the fuel heating region and/or to the at least one heated fuel outlet channel.

[025] Preferably and advantageously, the fuel heating and distribution unit has a partition plate separating the first and the second portion of the unit in the area of the partition plate, or along the partition plate, respectively.

[026] As an alternative, the first portion of the unit is defined as an upper body originating from a thermoplastic injection process and a second portion of the unit is a base overinjected on a portion of the upper body, the upper body being rigidly attached to the base.

[027] Preferably, the heating and distribution unit has a heater housing in communication with a heated fuel supply channel, the heated fuel supply channel being in fluid communication with three fuel outlet channels .

[028] The aforementioned partition plate preferably abuts the second portion and preferably is arranged recessed and/or embedded in or at the first portion, preferably in such a way, that the partition plate is completely surrounded by the internal unit defined by the first and second portion. Furthermore, according to a preferred embodiment, in which the supply gallery is provided in the first portion, the partition plate can delimit at least a portion of the gallery and/or at least a portion of the fuel heating region at a side facing the second portion.

[029] According to a preferred embodiment at least two heated fuel outlet channels can be provided, said at least two heated fuel outlet channels are connected to the same fuel heating region via at least two heated fuel supply channels. Therefore, a single heating region is assigned to at least two outlet channels. [030] The unit also may comprise at least one electrical heating element cooperating with the fuel in the respective fuel heating region for heating said fuel in the respective fuel heating region. To this end, said heating element may be equipped with a heat exchanging or heating surface being in contact with the fuel to be heated in the fuel heating region.

BRIEF DESCRIPTION OF THE DRAWINGS

[031] These and other objects, advantages and technical and functional improvements to the method for manufacturing a fuel distribution and heating unit and the fuel distribution and heating unit will become apparent to persons skilled in the art from the appended schematic figures that illustrate a non- limiting preferred embodiment of the present invention.

[032] Figure 1 illustrates a perspective view of a first advantageous embodiment of the fuel distribution and heating unit as disclosed by the present invention. This first preferred embodiment comprises two heating elements associated with four injection nozzles.

[033] Figure 2 illustrates an expanded perspective view of the first advantageous embodiment of the fuel distribution and heating unit as disclosed in the present invention.

[034] Figure 3 illustrates a cross section passing through the central region of the fuel injection nozzle of the heating system of the present invention.

[035] Figure 4 illustrates a cross section passing through the central region of the heating element.

[036] Figure 5 shows the internal part of the upper body according to the first preferred embodiment of the present invention. [037] Figure 6 illustrates a sealing weld that may be used in any one of the embodiments proposed by the present invention.

[038] Figure 7 illustrates a perspective view of a second advantageous embodiment of the fuel distribution and heating unit as disclosed by the present invention. This second preferred embodiment comprises a single heating element associated with three injection nozzles .

[039] Figure 8 illustrates an expanded perspective view according to the second advantageous embodiment of the fuel distribution and heating unit as disclosed by the present invention. DESCRIPTION OF EMBODIMENTS OF THE INVENTION

[040] The invention is now described in relation to the appended figures. In the figures and in the description to follow, similar parts are denoted by identical reference numerals. The figures are not necessarily to scale, i.e. certain features of the invention may be shown on an exaggerated scale or in some schematic manner, and also details of conventional elements may not be shown with a view to illustrating this description more clearly and concisely.

[041] For the purposes of the present invention, the heating element 40 comprises at least one heating surface 41, where a heat source is capable of heating, in a controlled manner, the fuel in contact with said heating surface 41. There are diverse ways in which to promote such heating, which are non-limiting, and use of a unit with thermistor element plates (PTC) or an electrical resistance element is highlighted.

[042] The manufacturing method proposed by the present invention for a fuel distribution unit comprises the steps of: a) obtaining a first portion of the fuel distribution and heating unit; and

[043] In this method, the attachment between the first and the second portion of the fuel distribution and heating unit defines:

- an internal region of the unit, comprising a supply gallery 24 connected to a fuel heating region 42 by means of a passage 22, and heated fuel passage channels 81 ; and

- an external region of the unit, comprising at least one fuel inlet opening 21, at least one heater housing

25 and at least one heated fuel outlet 31.

[044] The manufacturing method also involves the optional step of mounting a partition plate 80 in the first portion of the unit before the step of overinj ecting the second portion of the unit, such that the partition plate separates the first and the second portion .

[045] In a preferred embodiment, the first portion of the unit is an upper body 20 that is obtained by means of a preliminary step of thermoplastic injection, and the second portion of the unit is a base 30 overinjected on a portion of the upper body 20.

[046] The method for manufacturing the distribution and heating unit further involves an additional step of welding a seal 35 around the heated fuel supply channel 81.

[047] As may be seen in Figures 1 to 8, the fuel distribution and heating unit comprises:

- a first portion; and

- a second portion rigidly attached to the first portion by means of overinj ection . [048] The attachment between the first and the second portion of the fuel heating and distribution unit defines an internal region comprising a supply gallery 24 connected to a fuel heating region 42 by means of a passage 22, and heated fuel supply channels 81. Said attachment between the first and the second portion of the fuel heating and distribution unit also defines an external region comprising at least one fuel inlet opening 21, at least one heater housing 25 and at least one heated fuel outlet channel 21.

[049] As may be seen in Figures 2 and 8, in a preferred, advantageous embodiment the fuel heating and distribution unit of the present invention has a partition plate 80 separating the first and the second portion of the unit, which allows greater control in terms of the division of the internal regions in addition to more accurate dimensional control of the volume of the heated fuel supply channels 81, if defined by a recess in the partition plate 80, as may be seen in Figure 4.

[050] Alternatively, the first portion of the unit is defined as an upper body 20 originating from a thermoplastic injection process and the second portion of the unit is a base 30 overinjected on a portion of the upper body 20, the upper body 20 being rigidly attached to the base 30.

[051] In particular, the fuel heating and distribution unit 10 has a seal that is even more efficient when it comprises a sealing weld 35 around the heated fuel supply channel 81. Even more advantageously, this sealing weld 35 may be produced between the partition plate 80 and the upper body 20, or between the partition plate 80 and the base 30.

[052] In an advantageous embodiment of the present invention, the fuel heating and distribution unit 10 has two heater housings 25. Each heater housing 25 is in communication with a heated fuel supply channel 81 in fluid communication with two fuel outlet channels 31. This advantageous embodiment may be seen in Figure 6.

[053] Preferably, the fuel heating and distribution unit 10 has a heater housing 25 in communication with a heated fuel supply channel 81, said heated fuel supply channel 81 being in fluid communication with three fuel outlet channels 31. This preferred embodiment may be seen in detail in Figure 8.

[054] In an alternative embodiment of the present invention, the heated fuel supply channel 81 has a volume of between 0.02 ml and 0.12 ml.

[055] Images 1 to 6 reveal a first exemplary preferred embodiment for the fuel distribution and heating unit 10 of the present invention.

[056] As may be seen in Figure 1, the fuel distribution and heating unit 10 of the present invention comprises an upper body 20 fluidly connected to at least one inlet opening 21, at least one heater housing 25 and at least one heating element 40 comprising a heating surface 41 and a connector 43. Said heating element 40 is associated with the heater housing 25. The fuel distribution and heating unit 10 further comprises at least one fuel heating region 42. Said heating element 40, in particular said heating surface 41, cooperates with the fuel in the fuel heating region 42 in order to preheat the fuel before supplying the fule to a fuel infector (not shown) . Such a fuel injector can be inserted into a receptacle 90 provided at the second portion. The fuel distribution and heating unit 10 also has at least one base 30.

[057] Additionally in Figure 1, it is possible to note that the attachment between the heating element 40 and the heater housing 25 is provided by a locking element 60. Said locking element is of the resilient- element type and its use allows easy attachment of the heating element 40 to the heater housing 25, such that said heating elements 40 may easily be replaced when necessary. It should be pointed out that the attachment between the heating element 40 and the heater housing 25 may be achieved in a variety of ways. In a non- limiting manner, the use of a flange/screw system or, alternatively, the use of a male-type thread system in the heating element and corresponding female thread system in the heater housing 25 may be highlighted. Lastly, the presence is noted of installation members 29 associated with the base 30 in order to promote the attachment of the system of the present invention to an internal combustion engine, for example. Said installation members 29 may have an orifice in order that a screw can be used in the installation thereof.

[058] Figure 2 shows the arrangement of the partition plate 80 between the upper body 20 and the base 30 forming the fuel distribution and heating unit 10. This image clearly shows, also, the arrangement of the heated fuel outlet channels 31 present in the base 30 and associated in a fluid manner with the heated fuel supply channels 81 present in the partition plate 80.

[059] Figure 3 illustrates a cross section passing through the central region of the heated fuel outlet channel 31, where it is possible to clearly note the base 30, which, via said heated fuel outlet channel 31, supplies heated fuel to a fuel injection nozzle fluidically associated with the heated fuel outlet channel 31. In this image, also, it is possible to note the heating element 40 fixed to the heater housing 25 by means of the locking element 60.

[060] Figure 4 more clearly shows the attachment between the heating element 40 and the heater housing 25, where it is possible to note the use of an upper sealing ring 61 that prevents fuel leaking from the fuel distribution and heating unit 10.

[061] Figure 4 also shows the path travelled by the fuel to be heated, said fuel flowing through the supply gallery 24 of the upper body 20 and into the fuel heating region 42 via a passage region 22 of said upper body 20. The fuel that flows through the fuel heating region 42 is then heated and leaves said fuel heating region 42 via the heated fuel supply channels 81 that convey the already heated fuel to the heated fuel outlet channels 31. It should be noted that the paths travelled by the heated fuel are dimensioned in order to contain the minimum fuel necessary for the initial instants of starting the engine, so as to prevent energy wastage and to minimize heating time.

[062] Figure 5 discloses the interior part of the upper body 20 according to the first embodiment proposed by the present invention. In this image it is possible to note the fluid communication between the fuel inlet opening 21 and supply gallery 24.

[063] Figure 6 discloses sealing weld 35 (shown in dot-dash line) around the heated fuel supply channel 81 so as to guarantee greater leaktightness and to prevent leaks of fuel, thereby providing one of the improvements proposed by the present invention.

[064] Figure 7 discloses a second way in which to embody the fuel distribution and heating unit 10 according to the present invention.

[065] In a manner similar to that of Figure 1, which represents the first embodiment, Figure 7 illustrates the fuel distribution and heating unit 10 of the present invention, which comprises an upper body 20 fluidically connected to at least one inlet opening 21, at least one heater housing 25, at least one heating element 40 comprising a heating surface 41 and a connector 43. Said heating element 40 is attached to the heater housing 25 and further comprises at least one fuel heating region 42. The fuel distribution and heating unit 10 also has at least one base 30. The difference in this second embodiment is the fact that there is a single heating element.

[066] Figure 8 is similar to Figure 2 of the first embodiment of the present invention, where it is possible to note the partition plate 80 arranged between the upper body 20 and the base 30 forming the fuel distribution and heating unit 10. This image clearly shows, also, the arrangement of the heated fuel outlet channels 31 present in the base 30 and fluidically associated with the heated fuel supply channels 81 present in the partition plate 80. This embodiment discloses the use of a single heating element 40 associated with three heated fuel outlets 31.

[067] It is obvious that the present invention offers countless advantages in relation to the prior art and offers a less expensive solution for manufacture, provided with enhanced fuel sealing.

[068] Thus, as persons skilled in the art will readily understand, numerous modifications and variations in the invention are possible in light of the above teachings without departing from the scope of protection thereof, as defined in the appended claims.

Claims

METHOD FOR MANUFACTURING A FUEL DISTRIBUTION AND HEATING UNIT, characterized in that it comprises the steps of:

a. obtaining a first portion of the fuel distribution and heating unit; and

b. overinj ecting a second portion of the fuel distribution and heating unit such that it is rigidly attached to the first portion of the fuel distribution and heating unit,

the attachment between the first and the second portion of the fuel distribution and heating unit defining :

- an internal region of the unit, comprising a supply gallery (24) connected to a fuel heating region (42) by means of a passage (22), and heated fuel passage channels (81); and

- an external region of the unit, comprising at least one fuel inlet opening (21) , at least one heater housing (25) and at least one heated fuel outlet (31) .

METHOD FOR MANUFACTURING A FUEL DISTRIBUTION AND HEATING UNIT according to Claim 1, characterized in that it comprises a step of mounting a partition plate (80) in the first portion of the unit before the step of overinj ecting the second portion of the unit, such that the partition plate (80) separates the first and the second portion of the fuel distribution and heating unit.

METHOD FOR MANUFACTURING A FUEL DISTRIBUTION AND HEATING UNIT according to either of Claims 1 and 2, characterized in that the first portion of the unit is an upper body (20) obtained by means of a preliminary step of thermoplastic injection and the second portion of the unit is a base (30) overinjected on a portion of the upper body (20) .

METHOD FOR MANUFACTURING A FUEL DISTRIBUTION AND HEATING UNIT according to any one of Claims 1 to 3, characterized in that it comprises an additional step of sealing welding (35) around the heated fuel outlet channel (81) .

FUEL DISTRIBUTION AND HEATING UNIT, characterized in that it comprises:

- a first portion; and

- a second portion rigidly attached to the first portion by means of overinj ection,

in that the combination of the first and second portion of the unit defines:

- an internal region comprising a supply gallery

(24) connected to a fuel heating region (42) by means of a passage (22), and heated fuel supply channels (81); and

- an external region, comprising at least one fuel inlet opening (21), at least one heater housing

(25) and at least one heated fuel outlet channel (31) .

6. FUEL DISTRIBUTION AND HEATING UNIT according to Claim 5, characterized in that the at least one fuel inlet opening (21) is connected to the supply gallery (24 ) .

7. FUEL DISTRIBUTION AND HEATING UNIT according to Claim 5 or 6, characterized in that the fuel supply channels (81) are connected to the fuel heating region (42) .

8. FUEL DISTRIBUTION AND HEATING UNIT according to any one of Claims 5 to 7, characterized in that the fuel supply channels (81) are connected to the at least one heated fuel outlet channel (31) .

9. FUEL DISTRIBUTION AND HEATING UNIT according to any one of Claims 5 to 8, characterized in that it comprises a partition plate (80) separating the first and the second portion of the unit.

10. FUEL DISTRIBUTION AND HEATING UNIT according to Claim 9, characterized in that the respective heated fuel supply channel (81) is defined by a recess in the partition plate (80) .

11. FUEL DISTRIBUTION AND HEATING UNIT according to Claim 9 or 10, characterized in that the partition plate (80) abuts the second portion and is arranged recessed and/or embedded in the first portion .

12. FUEL DISTRIBUTION AND HEATING UNIT according to any one of Claims 9 to 11, characterized in that the partition plate (80) delimits at least a protion of the gallery (24) .

13. FUEL DISTRIBUTION AND HEATING UNIT according to any one of Claims 9 to 12, characterized in that the partition plate (80) delimits at least a portion of the fuel heating region (42) .

14. FUEL DISTRIBUTION AND HEATING UNIT according to any one of Claims 5 to 13, characterized in that at least two heated fuel outlet channels (31) are provided which are connected to the same fuel heating region (42) via said heated fuel supply channels (81).

FUEL DISTRIBUTION AND HEATING UNIT according to any one of Claims 5 to 14, characterized in that the unit also comprises at least one heating element (40) cooperating with the fuel in the respective fuel heating region (42) for heating said fuel.

FUEL DISTRIBUTION AND HEATING UNIT according to any one of Claims 5 to 15, characterized in that the first portion of the unit is an upper body (20) originating from a thermoplastic injection process and the second portion of the unit is a base (30) overinjected on a portion of the upper body (20), the upper body (20) being rigidly attached to the base (30) . 17. FUEL DISTRIBUTION AND HEATING UNIT according to any one of Claims 5 to 16, characterized in that it comprises a sealing weld (35) around the heated fuel supply channel (81) . 18. FUEL DISTRIBUTION AND HEATING UNIT according to any one of Claims 5 to 17, characterized in that it comprises two heater housings (25) , each heater housing (25) being in communication with a heated fuel supply channel (81) in fluid communication with two fuel outlet channels (31) .

19. FUEL DISTRIBUTION AND HEATING UNIT according to any one of Claims 5 to 17, characterized in that it comprises a heater housing (25) in communication with a heated fuel supply channel (81) in fluid communication with three fuel outlet channels (31) .

FUEL DISTRIBUTION AND HEATING UNIT according to any one of Claims 5 to 19, characterized in that each heated fuel supply channel (81) has a volume of between 0.02 ml and 0.12 ml.