Abstract:
The present invention refers to a fuel rail made of plastic material with a heating system ( 10,100 ). The said rail is applied, mainly, in the form of devices for aiding the cold start of engines which consume fuels whose specific vaporization heat is high, for example, alcohol. The fuel rail made of plastic material with a heating system presents reduced cost and weight and the same functional characteristics if compared to the fuel rails known by the state of the art, which are usually made of metal. Furthermore, the said fuel rail made of plastic material with a heating system presents internal compartments configured in such a manner that the slider sliders containing slide pins ( 51, 52, 53 ) of the injection mold can be easily removed, since there is no formation of negative faces.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention refers to an assembly which is constituted by a fuel rail made of plastic material with a heating system. The said rail is employed in cold start auxiliary devices of internal combustion engines which consume fuels with an elevated specific vaporization heat, for example, alcohol. 
         [0002]    In the last few years a great popularization of vehicles that use simultaneously more than one fuel has occurred, for example, gasoline and alcohol/ethanol. These vehicles, when they operate with alcohol as fuel, usually need an additional fuel tank dedicated to an initial injection of gasoline in order to start in cold climates. This is due to the fact that alcohol presents a high specific vaporization heat when compared to gasoline. Based on this physical-chemical limitation of alcohol and with the objective of eliminating the additional gasoline tank, vehicle manufacturers have developed cold starting devices for alcohol which aid the combustion process through the pre-heating of the fuel. 
         [0003]    A cold start device is generally fixed in a superior region of the engine block and is, as a rule, constituted by a fuel rail which has injection valves, elements for heating the fuel, ducts for the passage of fuel and their respective couplings. The said ducts of the rail, already known by the state of the art, are made of steel, especially, stainless steel. This is due to the fact that alcohol is highly corrosive. The fact that the ducts are made of metal elevates the production costs for the assembly, as well as, contributing to an increase in the vehicles weight. A fuel rail with heating from the state of the art can be verified, for example, from the document WO 2006/130938. 
         [0004]    Due to the problem of cost and weight cited above, it was necessary to develop alternative materials, especially, for the confection of ducts for said rail with a heating system. One of the alternatives is the use of a plastic material in place of metal, with the objective of significantly reducing costs and the total weight of the device associated with such change. 
         [0005]    This change presents, however, some drawbacks for its implementation. The first is related to the use of heating elements which reach, as a rule, temperatures which could damage the plastic material. A second difficulty is linked to the confection of the rail with a single piece of plastic material with a mold that allows maintaining its complex geometry resulting from its functional characteristics known by the state of the art and that, at the same time, allows a rapid and economical plastic injection process. 
         [0006]    In the state of the art there are no rails which aggregate, on one hand low cost and reduced weight of a rail made of plastic material and, on the other which manages to promote an adequate heating of the fuel. Such type of rail can be seen in document US 2009/199822 A1 which comprises different parts to be assembled together (which comprises security due to leakage of fuel) and also does not guarantee proper start-up of an engine when heating the fuel since due to its geometry will have to heat all the fuel inside the rail. 
         [0007]    It is worth observing that the production process for plastic material elements must be done, preferably, in a single injection step. Otherwise, a later fitting of several components must be undertaken, which can result in a loss of the confiability of the rail. It must be observed that the smaller the number of components, the greater the safety, since the chances of a fuel leak is smaller. 
         [0008]    The formation of a rail made of plastic material, preferably, in a single piece which attends to the complex geometry necessary to attain an ideal heating of the fuel is one of the objectives of the present invention. In the metal rails of the state of the art, what increases their total cost is the connection of its main external elements, constituted by a main tube and by two secondary ducts. This connection is made, generally, through a welding process, where entire metallic elements, of innumerous shapes, are united by a weld bead. It is interesting to observe that in the metal rail of the state of the art, in order to have a correct flow of fuel with adequate heating, it is necessary that the main tube is positioned in a substantially inferior part of the assembly. The shape of the heated rail of the state of the art can, therefore, interfere in the standard layout of an engine, eventually creating obstacles to its installation in the assembly line due to the difficulty of access for tools. 
       SUMMARY OF THE INVENTION 
       [0009]    The present invention refers to a set which constitutes a fuel rail made of plastic material with a heating system. The said rail is applied, mainly, in devices for aiding the cold start of engines which consume fuels whose specific vaporization heat is high, for example, alcohol. The fuel rail made of plastic material with a heating system presents a reduced cost and the same functional characteristics if compared to the metal fuel rails with heating systems known by the state of the art. Further, the said fuel rail is made of plastic material with a heating system that presents an improved spatial arrangement of its elements, where its external shape and the internal compartments are configured in such a manner, that slide pins employed in the plastic injection process can easily be removed as a function of the absence of negative faces. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    The present invention will be described, as follows, in greater detail based on an embodiment represented in the drawings. The figures show: 
           [0011]    FIG.  1 —is a cross sectional view of a fuel rail made of metal known by the state of the art; 
           [0012]    FIG.  2 —is a perspective view of the fuel rail made of plastic material with a heating system of the present invention; 
           [0013]    FIG.  3 —is a left lateral view of the fuel rail made of plastic material with a heating system of the present invention; 
           [0014]    FIG.  4 —is a cross sectional view of the fuel rail made of plastic material with a heating system of the present invention; 
           [0015]    FIG.  5 —is a schematic cross sectional view of the fuel rail made of plastic material with a heating system of the present invention, showing the direction for the removal of the slider containing the slide pins in the plastic injection process; 
           [0016]    FIG.  6 —is a view of the fuel rail made of plastic material with a heating system with an emphasis on the superior secondary duct; 
           [0017]    FIG.  7 —is a view of an optional embodiment of the fuel rail made of plastic material with a heating system with an emphasis on the superior secondary duct. 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    A metal fuel rail  1  known by the state of the art is shown in  FIG. 1  in order to illustrate the main differences between the said rail and the fuel rail made of plastic material with a heating system  10  of the present invention shown in  FIG. 2  and especially in  FIG. 4 . In the rail  1 , it can be noticed that a main tube  2  presents itself arranged in an inferior portion of a superior secondary duct  5 . This geometric arrangement is necessary for the correct operation of the said rail  1 , and results, however, in a reduction in the useful space of the engine hood. This is due to the fact that for the installation/maintenance of the engine components it is necessary to insert corresponding tools in said space. Thus, with the main tube  2  in the shown position, the handling of the tools is made more difficult. If the main tube  2  was in a superior position, closer to the superior extremity of the superior secondary duct  5 , for example, to ease assembly, the heating process of the fuel would be compromised due to a necessary repositioning of orifice  8  which connects the main tube  2  with the superior secondary duct  5 . The orifice  8  being very close to the entry of the fuel sending element  9  hinders the transfer of heat, since the fuel would not travel a sufficiently long course exposed to the heating of the lance  4 . Another problem of the state of the art which can be observed in  FIG. 1  is the fact that in the pre-heating phase, where the discharge of fuel is substantially low or even zero/none, the heated fuel can undertake a return trajectory to orifice  8 , bearing in mind that its elevated temperature results in a lower density compared to unheated fuel, which would result in the heat exchange of fuel in the main tube. This occurs due to the fact that heat provided by the lance  4  is in a lower position if compared to the orifice  8 . In other words, the orifice  8  in not located in the most lower portion of the secondary duct  5 . 
         [0019]    Another problem shown in  FIG. 1  is in the shape and positioning of the fuel sending element  9 . This configuration for the fuel sending element  9  used for rails made of metal leads to the occurrence of negative faces  7 , in an injection mold, which makes impossible the production of a fuel rail made of plastic material with a heating system  10 , as a result of the impossibility of the removal of the slider containing the slide pin. 
         [0020]    On the other hand, the present invention can be seen in  FIG. 2 , where a main tube  11  of the fuel rail made of plastic material with a heating system  10  is shown. The tube  11  has the function of distributing the fuel along its length and supporting the fixation supports  14  and the secondary ducts which will be shown afterwards. It can be noticed that the tube  11  has a series of connections with superior secondary ducts  13  which comprehend heating elements  16 . The said heating elements  16  are responsible for the function of heating the fuel in the rail  10 . The elements  16 , which can be better seen in  FIGS. 3 and 4 , have a lance  4  which includes an internal resistance which dissipates electrical energy in the form of heat. Further, there is a base which serves not only for sealing the superior secondary duct  13 , but also to connect the source of electrical energy, this connection being done in an inferior extremity of said element  16  external to the rail  10 . It is possible to see also the fixing clamps  15  which have a shape compatible with their respective application in the slots  18  arranged spaced out along the entire radial region of the inferior extremities of the secondary superior ducts  13 . These clamps  15  have as their main function to permit the fixing of the heating elements  16  in the superior secondary ducts  13 . 
         [0021]    The fixation supports  14  of the rail  10  are arranged spaced out along the longitudinal length of the main tube  11 . These supports  14  can be fixed through fixation elements, for example, screws (not shown in the figure) applied in openings in its base, in such a manner that the rail  10  finds itself fixed to a superior region of the vehicle&#39;s engine block. The number of fixation elements  14  can vary according to the total length of the rail  10 , which depends on the spacing and the number of inferior and superior secondary ducts  13  and  19  applied. This variation can also occur according to the de-termination of the tolerable vibration limits for the rail  10 . 
         [0022]    In  FIG. 2 , the closing element  12  of the main tube  11  can be seen. Through this closing element the rod of the rail&#39;s injection process is removed. The closing  12  is undertaken in a further step to the rail&#39;s injection. 
         [0023]    The  FIG. 3  presents a left side view of the fuel rail  10  made of plastic material with a heating system, in which some important elements which compose the said rail  10  can be better seen. 
         [0024]    These elements are the superior secondary ducts  13  and the inferior secondary ducts  19 . The said inferior ducts  19  comprehend fuel injection valves  22  which will receive the heated fuel and inject it, in a pulverized form, in a combustion chamber. 
         [0025]    On the other hand the superior secondary ducts  13  have heating elements  16  which are responsible for the main function of the rail  10 , which is to adequately heat the fuel and ease the engine start. 
         [0026]    The fuel admission duct  17  is arranged in such a manner that it follows the angle of inclination of the main tube  11  and with that, eases the future fitting of the rail  10  to other engine components. 
         [0027]    There is still a connector  23  which serves for the connection of electrical energy to the fuel injection valve  22 . 
         [0028]      FIG. 4  presents a cross sectional view of the fuel rail made of plastic material with a heating system  10 , in which its internal compartments can be seen in greater detail. Further, the superior secondary duct  13 , the inferior secondary duct  19 , an internal duct  38 , the heating element  16  and the injection valve  22  can be seen, permitting the understanding of the rail  10  and the route taken by the fuel. This route begins in the fuel admission duct  17  (shown in  FIG. 3 ), then, the distribution of the fuel under pressure occurs along the entire length of the main tube  11 . This fuel flows through the orifice  34  to the internal duct  38  and is thus transported to the superior secondary duct  13 . The outlet of the duct  38  conducts the fuel to the base of the heating element  16 . At the end of this duct  38  a recess  72  (seen in  FIG. 7 ) is provided which makes the flow of fuel to be directed to an inferior region of the lance  4  opposed to the duct  38 . Thanks to this additional direction of fuel, the fuel is heated in an optimized manner through contact with the lance  4  until it reaches a fuel sending element  33 . By passing through the fuel sending element  33 , the fuel flows to the injection valve  22  which injects the pulverized fuel in the combustion chamber. 
         [0029]    It is important to note that the fuel sending element  33 , according to the present invention, does not present negative faces, as can be seen in on  FIG. 5 , bearing in mind that it is limited by the internal walls of the superior secondary duct  13 . Another detail to be noted is that the angle that the fuel sending element  33  makes with the internal wall  37  of the rail  10  possesses as its maximum limit the central axis of the injection valve  22 . This limit occurs due to the configuration of the slide pins, since these can be removed from where they entered during the injection process. 
         [0030]    The internal duct  38  has as its main function the improvement of the conduction of the flow of fuel in relation to what is already known in the state of the art, for example, as shown in  FIG. 1 . The flow of fuel coming from the main tube  11 , as a result of duct  38 , directly focuses on the base of the lance  4 , responsible for the transmission of heat to the fuel. This duct  38 , which is arranged internally in the superior secondary duct  13 , begins on an internal wall  37  of the superior secondary duct and extends until a point close to the base of the heating element  16 . Another internal duct  38  can eventually be used for the conduction of the fluid to the base of the lance  4  of the heating element  16 . The shape of the internal duct  38  can be circular of in the form of a circular segment. 
         [0031]    The injection valve  22 , which is in itself already known from the state of the art can assume varied shapes and is also shown in details in  FIG. 4 . The body of the valve  39  is arranged in a concentric manner to the inferior secondary duct  19 . 
         [0032]      FIG. 5  shows in a schematic manner the direction of the movement of the main injection sleeves containing slide pins of the injection mold responsible for the formation of the fuel rail made of plastic material with a heating system  10  during the piece&#39;s extraction process. It is worth remembering that for economic and leakage reasons the injection of the rail  10  must occur in a single step, being, therefore, the respective injection mold correspondingly complex. 
         [0033]    The slider with the slide pin  51  of the mold is responsible for the formation of the inferior secondary duct  19  and its removal from the injected piece occurs in a direction indicated by the arrow  55  in  FIG. 5 . This arrow  55  has an opposite direction in the closing of the mold with the insertion of the respective slider with the slide pin  51  when the mold is prepared for injection. It is important to note that the fuel sending element  33  is geometrically configured in a manner that permits the removal of the slider with the slide pin  51 . This becomes possible through the concentricness which exists between the axes of the fuel sending element  33  and the inferior secondary duct  19  in the rail of the present invention. 
         [0034]    The slider with the slide pin  53  is responsible for the formation of the main tube  11  and is removed in a direction  56 . The slider containing the slide pin  52  of the mold is responsible for the formation of the superior secondary duct  13  and is removed in the direction  54  during the process for the opening of the mold and the corresponding extraction of the injected piece. 
         [0035]    The rail of the present invention can be made of a single material, for example, a thermoplastic of the polyamide family, (for example, PA66), with or without the use of a reinforcement material, such as fiberglass, in quantities of 15 to 40%. It can also be done with a blend of thermoplastic materials or in co-injection with the employment of several thermoplastics (for example, PA, POM, PEEK, etc.), whenever this becomes necessary for reasons of mechanical or thermal resistance. 
         [0036]      FIG. 6  presents a view of the fuel rail made of plastic material with a heating system  10  that shows the superior secondary duct  13  in detail. In a first embodiment of the present invention, the surface  61 , where the exit of the internal duct  38  or internal ducts  38  occurs, is flat, that is, the flow of fuel as it reaches the end of the internal duct  38  will distribute itself in a uniform manner throughout the base of the heating element  16 . 
         [0037]      FIG. 7  presents a view of a fuel rail made of plastic material with a heating system  100  which shows the superior secondary duct  13  in detail. In a second embodiment of the present invention, the surface  71 , where the exit of the internal duct  38  occurs, presents a recess  72 , which permits that the flow of fuel in reaching the end of the internal duct  38  be directed, through the said recess  72 , to an inferior portion of the base of the heating element  16 . This makes the process of heating the fuel optimized, bearing in mind that it involves the lance  4  of the heating element  16 , travel-ling along a longer route and in this manner increasing the contact time between the fuel and the said lance  4 , which is responsible of the transmission of heat. The recess  72  can also exist on both sides of the surface  71 , that is, on the left and right sides in order to optimize even further the trajectory of the flow of fuel. 
         [0038]    Having described a preferred exemplary embodiment, it must be understood that the scope of the present invention includes other possible variations, not only being limited by the content of the appended claims, there included all the possible equivalents.