WO2009009846A1

WO2009009846A1 - Fuel rail

Info

Publication number: WO2009009846A1
Application number: PCT/BR2008/000197
Authority: WO
Inventors: Fernando Lepsch; Marcos Melo Araujo; Rosalvo Bertolucci Filho; Alvaro Augusto Vasconcelos
Original assignee: Robert Bosch Limitada
Priority date: 2007-07-19
Filing date: 2008-07-08
Publication date: 2009-01-22
Also published as: BRPI0703129B1; BRPI0703129A2

Abstract

The present invention relates to a fuel rail (1 ) having two overlapping covers (2, 3) with heating elements (2.4) inserted inside said fuel rail. In order to obtain a higher fuel heating concentration, internal housings (2.5) are provided inside the fuel rail (1 ) to ensure that an adequately heated fuel is provided to an internal combustion engine.

Description

FUEL RAIL

The present invention relates to a fuel rail for heating fuel. Description of the Prior Art

There are several prior-art devices that enable fuel heating with a high specific heat of vaporization. In several applications, only one type of fuel needs to be provided to an internal combustion engine, because as widely known in this segment, the use of additional fuel as a means for starting the internal combustion engine that uses this type of fuel should be avoided Currently, the type of fuel with these characteristics, that is to say, which has faced difficulties to start up the engine is the alcohol (ethanol).

As known, there is a growing need for this type of fuel around the world, since in view of global warming alcohol seems to be the energy solution with the best cost-benefit ratio. In this sense, the use of alcohol in an optimized manner especially in low temperature regions that cause easy evaporation of the alcohol is highly desirable in the art.

The applicant itself has developed some devices and systems for optimized fuel heating, as can be seen, for instance, in publication WO 2006/130938. This document has successfully described the concentrated heating only of a portion of a fuel rail; and said heating does not waste the energy of the means used to heat the fuel. Further to the very concentrated heating, a height difference and the use of convection enable that only the fuel that has been heated reaches the internal combustion engine. Surprisingly, the abovementioned invention was not only capable of providing very suitable heating for starting up the engine but also promoting a very considerable emission reduction in the heating phase of the engine. This had not been accomplished in the prior art. It should be noted that the heating phase is the main responsible for highly harmful gas emissions to the atmosphere, because some devices are still not operating, such as, for instance, the catalyst, since they need to be heated for such.

Although said invention is technically very advanced, it still requires a less costly production process. This happens because, in spite of the advanced technology involved, often the invention does not reach the consumer market with aggressive prices, which affects its success in sales.

In the case of document WO 2006/130938, the geometric shape of this fuel rail requires several complicated manufacturing process steps.

In addition, since the bay of an internal combustion engine is a very small space, the designers are having difficulties in adapting the existing engine designs to the cited fuel rail.

Some of the prior-art fuel rails are of the tubular shape, onto which holes are made for fitting injection valves. Other types are bipartite, and by joining two overlapping covers, they enable the creation of a fuel rail under which holes are made for fitting injection valves.

A type of bipartite fuel rail (which is not so common) can be seen in Figure 1 , in which the two overlapping covers forming the fuel rail are clearly seen. To a first cover A is fitted a second cover B forming a hollow space between the two covers, which is later filled by the fuel. The fuel is supplied by means of a fuel inlet C which is in fluid communication with said hollow space. After entering the fuel rail itself, the fuel flows to the outlets D of the fuel rail to be injected into the internal combustion engine through injection valves E.

In spite of the brief description provided, there is no fuel heating in this type of fuel rail.

The two types of fuel rail manufacturing concepts have always coexisted, but each one has a different design. Objects of the Invention

A first object of the present invention is to provide a fuel rail that enables adequate fuel heating;

A second object of the present invention is to provide a fuel rail that enables further to adequate fuel heating, being of low production cost; A third object of the invention is to provide a fuel rail which in addition to heating the fuel and being of low cost, is of reduced geometric shape. Brief Description of the Drawings

The present invention will be described below in more details, based on an example of execution represented in the drawings. The figures show: Figure 1 is a front view of a prior-art fuel rail;

Figure 2 is an exploded view of the fuel rail according to the present invention;

Figure 3 is a perspective view of present invention partially mounted; Figure 4 is a perspective view of present invention mounted;

Figure 5 is a front perspective view of the present invention disclosing some of its internal details;

Figure 6 is a side view of the present invention disclosing some of its internal details; Figure 7 is a perspective view of one of the components of the present invention;

Figure 8 is a perspective view of one of the components of the present invention;

Figure 9 is a side view of the present invention disclosing some of its internal details;

Figure 10 is a side view of the present invention disclosing some of its internal details;

Figure 11 is an exploded view of the fuel rail according to the present invention disclosing some of its internal details. Detailed Description of Drawings

Figure 2 shows a bipartite fuel rail 1 , including the components thereof in an exploded view. The fuel rail body 1 is basically composed of a bottom cover 2 and a top cover 3, which are shaped in such a way as to enable them to fit so as to form a space between them. In this space the fuel flows to be later used by an internal combustion engine.

The fit between both covers 2, 3 is such that sealing is promoted in their side walls 2.1 , 3.1 , which are arranged along each respective cover and are responsible for forming said space when the covers overlap. For the fuel not to drain from fuel rail 1 , the seal between covers 2, 3 can be carried out by means of several types of manufacturing processes, such as, for instance, brazing; it is also possible to introduce a sealing element (joint) between covers 2, 3.

Connected to cover 3 is a fuel inlet 3.2 which receives pressurized fuel from a usual supply system. Thus, through this fuel inlet 3.2, is possible a fluid communication between all the fuel rail 1 interior.

Connected to the bottom cover 2 there are more components of fuel rail 1. Firstly, in the bottom face of cover 2, there are four fuel outlets 2.2 (there is an outlet for each internal combustion engine cylinder). In each fuel outlet 2.2 is retained an injection valve 2.3, which promotes fuel atomization / aspersion to the engine.

Therefore, the pressurized fuel that enters the fuel rail 1 flows from the fuel inlet 3.2 to each of the fuel valves 2.3. However, before entering the injection valves 2.3, the fuel goes through a concentrated heating in order to ensure that only the fuel that was heated enters the injection valves 2.3 and, with that, promotes the known advantages of injecting the heated fuel into the internal combustion engine. The heating is done by heating elements 2.4 that are perpendicularly inserted in the fuel rail in relation to each respective injection valve.

As already known in the art, heating all the fuel inside the fuel rail 1 should be avoided, because the power needed for adequate heating would be excessively high and technically unfeasible. Thus, in order to limit the fuel portion that receives a significant amount of heat from the heating element 2.4, a housing 2.5 is provided surrounding the heating element 2.4. This housing 2.5 forms an internal chamber (which is best described in the following figures), which is both in fluid communication with the fuel outlet 2.2 and with the space formed between covers 2 and 3.

This housing 2.5 is connected to the bottom of the bottom cover 2, as can be seen in Figure 3, promoting a sealing between the housing 2.5 and the bottom cover 2. In addition, the heating element 2.4 is inserted inside the fuel rail 1 and enters said chamber, that is to say, part of the heating element 2.4 is inserted inside the housing 2.5.

Hence, the fuel inside the fuel rail is forced to flow to the fuel outlet 2.2 only by means of a small passageway 2.6 of the housing 2.5, through which the heating element also enters the housing 2.5.

Figures 4 and 5 show the fuel rail 1 in its final mounted form and the latter also depicts some internal details thereof. Therefore, it is clear how the heating element 2.4 enters the housing 2.5 through the passageway 2.6. The fuel is confined in the internal chamber 2.7, before it flows to the fuel outlet 2.2, providing heat from the heating element 2.4 to the fuel that is only present in the internal chamber 2.7. Actually, heat transfer to the rest of the fuel present inside the fuel rail 1 is minimized, thus ensuring that virtually all the heat provided is directed to the fuel that will be used right afterwards by the internal combustion engine.

Heating occurs in a quite small fuel rail, facilitating the engine cowl design and, compared with the prior-art solutions, having lower costs and providing adequate and economically feasible heating.

In spite of the foregoing, a height difference between the fuel inlet in the internal chamber 2.7 (through passageway 2.6) and the fuel outlet

2.2 is very significant in the present invention. This is so, because through convection, the fuel with the highest temperature and the lowest specific mass tends to rise in the internal chamber 2.7. Thus, the side view of Figure

6 shows the fuel rail 1 horizontally positioned. This figure also depicts some internal details of the fuel rail 1.

The fuel passageway 2.6 inlet, through which the fuel enters the internal chamber 2.7, is at a lower position than the fuel outlet 2.2, thus providing fuel adequately heated to the injection valve 2.3. In other words, the fuel portion having the highest temperature rises inside the chamber 2.5 and is close to the fuel outlet 2.2 because of the convection phenomenon.

Moreover, to optimize the heat transfer between the heating element 2.4 and the fuel, the fuel passageway 2.6 can be moved to the side and lower portion of the housing 2.5. This arrangement is seen in Figure 7, in which a receiving element 2.8 of the heating element 2.4 is depicted. This receiving element 2.8 enables the heating element to enter the housing 2.5, and the fuel can also go through this receiving element. However, the main fuel flow to the internal chamber 2.7 is made possible by the passageway 2.6. Thus, the fuel enters the chamber 2.7 mainly through the passageway 2.6, which causes the fuel to enter the fuel rail in the lowest internal region thereof. This also prevents any portion of the heated fuel from leaving the internal chamber 2.7 and returning to the part of the fuel rail where there is unheated fuel.

Additionally, because this passageway 2.6 is perpendicular to the axis of the heating element 2.4, turbulence is caused in the entry of the internal chamber 2.7 and a greater heat exchange is allowed.

Optionally, a second hole 2.9 can be seen in the upper part of the housing 2.5 (see Figure 8). This hole, although it provides fluid communication between the fuel that is more heated in the upper part of the chamber 2.7 and, therefore, enables heat exchange between the heated fuel and the unheated fuel outside said chamber 2.7, provides strength and efficiency for the operation of the fuel rail and the internal combustion engine. This is due to the fact that the part of the heated fuel is transformed into vapor and, as known in the art, it should be avoided that gas enters the injection valve 2.3 or is in contact with the heating element 2.4. In the first case, the fuel consumption in the engine can be hampered and, in the second case, the heating element 2.4 may become superheated. Thus, any gaseous portion that is not present inside the chamber

2.7 is expelled through the second hole 2.9, which is a kind of relief for low specific mass fluids, ensuring that the chamber 2.7 only contains liquid phase. Naturally, the area of this hole is previously calculated so that the heat exchanged therein is not excessively high so as to hinder the provision of duly heated fuel to the injection valve 2.3.

With a further objective of having a more compact fuel rail 1 to meet some extreme requirements of very small engine cowls, the heating element 2.4 can be farther moved towards inside the fuel rail 1 , more precisely to the housing 2.5. In this sense, the housing 2.5 needs to be slightly larger when compared to the described housing and consequently the volume of the chamber 2.7 is increased mainly in its upper portion. This need causes the heating element to be close (or even above) the height of the fuel outlet 2.2 (as can be seen in Figure 9). In fact, fuel that is not totally heated could enter the injection valve thus reducing the efficiency provided by the fuel rail 1. For this reason, an extension 2.10 of the outlet 2.2 is introduced inside the chamber 2.7 causing the fuel captured by the outlet 2.2 to be only the one in the upper portion of the chamber 2.7. Thus, it is ensured that, with an even smaller fuel rail in terms of external dimensions, adequately heated fuel can still be provided.

Finally, there are also internal combustion engine cowls that require that the heating electric connections are made in the upper part of the fuel rail. Figure 10 shows that the heating element 2.4 is displaced to an upper portion of the fuel rail 1. In this case, the housing 2.5 should have a fuel passageway 2.11 in its lower portion opposite to the heating element 2.4, so as to ensure that the fuel inlet in the chamber 2.7 is done from the bottom. The fuel passageway 2.11 can be seen in an exploded view of the fuel rail 1 in Figure 11 (Figure 10 also shows this detail). Therefore, the heated fuel flows to the outlet 2.2 being heated by the heating element 2.4.

In order not to have a fluid communication between the heated fuel and the unheated fuel, sealing should be provided between the upper part of the housing 2.5 and the heating element 2.4. Having described examples of the invention with reference to its preferred embodiments, it is to be understood that the scope of the present invention embraces other possible variations, being limited solely by the appended claims, including the possible equivalents therein.

Claims

1. A fuel rail (1 ) comprising:

- a top cover (3) connected to a bottom cover (2) in a sealing manner, wherein between said covers (2, 3) a space is formed for the fuel; - the top cover (3) or the bottom cover (2) has a fuel inlet (3.2), which is in fluid communication with said space;

- the bottom cover (2) comprises at least one fuel outlet (2.2), which communicates with an injection valve (2.3); characterized in that: at least one heating element (2.4) is provided, extending from inside the fuel rail, in which the heating element is substantially covered by a housing (2.5), which forms an internal chamber (2.7) between the heating element (2.4) and the housing itself (2.5), said internal chamber (2.7) communicating with the fuel outlet (2.2) and the space for the fuel. 2. A fuel rail (1) according to claim 1 , characterized in that the fuel outlet (2.2) is at a higher height than a fuel passageway (2.6,

2.11) of the housing (2.5).

3. A fuel rail (1) according to claim 2, characterized in that the fuel passageway (2.6, 2.11) is laterally arranged in the housing (2.5) in such way that as it enters the internal chamber (2.7) the fuel flows perpendicularly to the heating element (2.4).

4. A fuel rail (1 ) according to one of the preceding claims, characterized in that the fuel outlet (2.2) has an extension (2.10).

5. A fuel rail (1 ) according to one of the preceding claims, characterized in that the housing (2.5) has a second hole (2.9) in its upper end.

6. A fuel rail (1 ) according to one of the preceding claims, characterized in that the heating element (2.4) is inserted in an upper portion of the fuel rail (1).