FUEL TANK FOR HYBRID VEHICLE

FIELD OF THE INVENTION

The present invention relates to a hybrid fuel tank for motor vehicles describing a technical solution, at technological level, for the product and manufacturing process. It's a hybrid fuel tank designed to store all types of fuels in general, liquids and gases, which are used in the different markets.

The product shows high performance features in terms of useful capability, related weight, impermeability, and, not less important, being 100% recyclable and reusable taking into account the different work conditions, safety and environmental restrictions to which it is submitted.

In what refers to product design and related technological process, it presents itself as making the difference for various reasons such as using one of the energy sources of the transformation process to promote adhesion between bodies, metal and plastic, therefore obtaining a hybrid concept. PRIOR ART

A fuel tank can be divided into four subsystems, a tank for storing fuel, a filling system to allow refueling, a gas management system controlling the pressure inside the tank, and a system for pumping, filtering and measuring tank's level. A fifth subsystem (additive management system) may exist in the case of vehicles equipped with particulate filter in exhaust system.

The technical solution which is proposed in present invention applies to the fuel tank itself.

On the market, there are different constructive solutions, ranging from metallic solutions, polymeric ones to mixed solutions, these being the result of the interface between metallic structures and polymeric structures.

Despite these different technologies, the statutory requests are the same, i.e., whatever the technology used the fuel tank must resist to an internal pressure. Also the durability must be ensured in terms of years and/or Km. - PLASTIC

Regarding plastics solutions we find two types of technologies aiming to fulfill the evaporative emissions requirements: Monolayer or Multilayer. - Monolayer: This technology consists in a single layer of HDPE (high density polyethylene) which shapes the fuel tank and the filler piping. In order to decrease permeability and meet the Euro and LEV11 emissions regulations, where the last products are fluoridated;

Multilayer: In this case, it consists of a multilayer plastic with an additional barrier layer, which allows a considerable reduction in fuel tank hydrocarbon emissions and takes in account the most restrictive environmental demands of the Euro 5. Nowadays, there are already solutions with 6 different raw materials layers in order to meet the most stringent requirements in terms of evaporative emissions (PZEV) , and to reduce noise transmission due to fuel agitation during vehicle use (slosh test) .

The plastic technology presents quite interesting advantages for today's automotive industry. The manufacturing of very complex shapes and its easy adaptation to the surroundings make it very easy to design the product, which turns out to be restricted to the space left by other components. It also allows during the manufacturing process to execute appropriate channels to pass connection piping for the different components. The use of plastic as a basic raw material eliminates all problems related to corrosion given the interaction with fuel, water and other external agents. Even in what regards the action of gravel and other objects' projection on the lower part of the vehicle it is not necessary to incorporate anti-gravel materials or specific painting. The known ability of the plastic material to absorb energy in case of large deformations and/or impacts allows compliance with the requirements of rear and side crash, not raising significant problems.

However, the use of plastic as a technology for fuel tanks raises some questions. The used manufacturing process prevents the placement of components inside the tank, forcing to increase the number of outside openings for placement of valves and other connections.

The well-known lack of resistance of the material when submitted to continuously applied loads leads to a continuous deformation of the tank's bottom. Although it can be partially reduced by using metal straps, the remaining deformation is enough to degrade the information transmitted over time to the driver about the volume still available for use (the bottom face serves as a reference for reading the volume of fuel inside the tank) . Although the manufacturers of fuel tanks affirm and demonstrate the ability to recycle plastic with multilayer technology, the truth is that associated costs are too high for this industry and the availability of such a technology is not yet a reality. The hydrophilic characteristic of plastic also restricts the future use of this recycled material due to its prolonged contact with fuel and consequent absorption. The resistance to temperature requires specific measures. Given the fact that the fuel tank is mostly located in the lower region of the vehicle near the rear axle, the interaction with the exhaust line of the vehicle is constant. Since plastic material experiences deterioration to prolonged exposure to temperatures above 80 °C, it is mandatory the use of thermal barriers, normally plates made of aluminum or aluminized steel.

For the polymers to have chemical resistance to fuels and electrical conductivity capability for the elimination of static electricity it is required to add various additives to its basic formula, making them expensive .

Regarding the above, reference is made, for instance, to the American patent with publication N° US 2003019876768A1 and to German patent with publication N° DE 10139782A1.

- METAL

As regards the metallic solution, the type of raw material used is steel, which is preponderant in the product's definition. In today's market we find a wide variety of steels for the most different applications and needs. However, tanks manufacturing needs materials with high elongation capacity due to final geometry of the product and its manufacturing process (stamping and welding of semi-bodies) . One of the most commonly used steels is mild steel or very low-carbon steel . In this technology, the common thickness is between 0.8 to 1.0mm and the steel density is 7.85 kg/dm ³ , resulting in products weighting between 8 and 10 Kg for a useful volume of 50 liters. Comparatively to plastic products, metals have a smaller volume-to-weight ratio, i.e., plastics tanks are characterized by possessing greater volume for the same weight. This characteristic, or even disadvantage, of metal products is due to the necessity of flanges to allow joining together the two semi-bodies forming the fuel tank, resulting in a decrease of usable area and higher weights.

On average, a metal tank is normally 25% heavier than a plastic solution for the same volume. However, this value is just valid for the comparison of the tank itself. Nevertheless, as is referred by studies of the Strategic Alliance for Steel Fuel Tanks - SASFT, there are situations in which those positions are reversed due to the type of the manufacturing processes and additional packaging constraints, since the thermal protection and support handles parts are only necessary for the plastic solution.

The use of metals in metallic tanks construction raises a very important problem, the corrosion. The interaction of metal without protection with chemicals which are present in fuel originates global corrosion situations in a short period of time. Thus, the development and application of coatings on base material has become an unavoidable issue. Today's solutions for coatings are various and each time more complex due to the anti- corrosion requirements which are increasingly demanding. Coatings currently in use can be classified according to their chemical formula and application. Regarding the chemical formula we'll have metal coatings and organic coatings, and regarding the application we'll have pre- painted coatings and post-painted coatings.

Known as metallic coatings is the aluminized and the incorporation of chemical elements in metal alloys which allows meeting the requirements of corrosion despite of a higher associated cost. Coatings such as zinc, nickel and tin are widely used. Due to the increasingly restrictive rules for recycling and reducing the use of heavy materials, these coatings have fallen into disuse given its chemical basis. Other coatings have thus been developed.

Among organic coatings epoxy based, MAGNI is one of the success cases that has gained wide acceptance because of its high corrosion resistance (about 2000 hours in a salt spray test) and due to the absence of heavy metals in its constitution which are prohibited according to the new environment directives. Despite their cost, his presence eliminates the need of external painting for protection and the application of anti-gravel materials, what makes it irrelevant in the economic impact on final product . In regards to application, pre-painted coatings allow their application in raw material still in the coil or blank phase, turning the implementation easy and reducing overall costs. However, during the mechanical forming process, there is partial removal in areas of greater drawing and friction with the tool, and total absence of it in cutting faces. Still during the welding process, the coating is removed or even consumed due to the strong heat input. Its presence may reduce the materials weldability and electrical conductivity and produce intense fumes which may result in a lower final product quality. On the other hand, post-painted coatings not presenting the above problems have however a more complex manufacturing process, given the need of application on specific parts with complex geometries.

The use of this solution occurs mostly in the Japanese and South-American markets, mainly due to domestic production capability of their own brands in the first case, and to the technology of installed production capability in the second one. This technological solution has shown to take into account very important current requirements as low evaporative emissions and continuous recyclability of the set. The dimensional stability against temperature and humidity variations, the absence of deformation due to continuous application of loads over time, the more limited deformations due to the internal pressure action and the higher electrical conductivity of the material are some of the most important advantages of using metal .

As an example regarding the above, for the metal product, reference is made to the German patent with publication N° DE 102005016492A1 and to the American patent with publication N° US 6,360,765, which are based on joining together two metal halves using a welding process. SUMMARY OF THE INVENTION

The hybrid fuel tank for motor vehicles of this invention was developed to face the increasing dynamism of automotive industry, which releases new models at increasingly shorter periods of time, and taking into account the need to carry out a series of technical studies and rehearsals each time a new fuel tank concept is produced, that implying an investment in specialized human and financial resources, using innovative and versatile manufacturing processes.

Present invention refers to an innovative product, first of all because it combines most of the advantages of the two existing solutions, plastic and metal, eliminating the drawbacks of such solutions. The related manufacturing process presents simplicity combined with versatility, the latter being illustrated by the possibility of obtaining a wide range of fuel tanks using the same manufacturing process . The distinguishing features of this invention are based on a number of technical issues with major impact on the volume-to-weight ratio, and still in what refers to recyclability, reusability, resistance and impermeability.

Moreover, a set formed by upper and lower metallic semi-bodies is reinforced by upper and lower nonmetallic semi-bodies, made of polymeric material which can be applied by an injection process or thermoforming in order to provide greater rigidity to the final set.

The hybrid fuel tank for motor vehicles described in the present invention differs from the other already known, firstly because it presents a high rigidity in the areas of greater weakness, the flat areas, due to the reinforcement applied. Consequently it offers better results in terms of acoustic issues, i.e. noise, due to the shock of projected objects when the vehicles are in motion. This happens without an increase of the relative weight of the hybrid fuel tank for motor vehicles. On the contrary, it presents itself as having a weight below prior art tanks, and possessing differentiating volumes, which implies fewer stops for refueling; greater number of refueling procedures causes higher consumptions and gaseous emissions to the atmosphere.

The upper and lower metallic semi -bodies produced from metallic materials are submitted to surface treatment and have a reduced thickness comparing to the metallic solutions currently available in the market. They provide impermeability to the set and promote resistance against contact with aggressive environment.

The fact that this innovation uses a reinforcement outer layer with very low density adds a high strength to the set and eliminates problems such as buckling, or even the need of using straps in the case of plastic tanks, and/or ribs in the case of metallic tanks.

When compared to prior art, the hybrid fuel tank for motor vehicles described in this invention presents the following distinguishing features:

- Better performance at the evaporative emissions level. The product is 100% impermeable;

- Optimized volume- to- weight ratio;

- Absence of application of materials considered restricted ;

- Applied materials are 100% recyclable; and

- Resistance to working conditions during product life time such as corrosion, pressure, temperature, shocks and fire. BRIEF DESCRIPTION OF THE DRAWINGS

The description presented below refers to the accompanying drawings which are only given by way of reference without any limitative purpose, and wherein: - Fig. 1 is a sectional view of the hybrid fuel tank ;

- Fig. 2 is a sectional view of the fuel tank;

- Fig. 3 is a perspective view of the upper and lower semi -bodies, nonmetallic and metallic;

- Fig. 4 is a sectional view of the hybrid fuel tank ;

- Fig. 5 is a sectional view of the semi-bodies flanges, nonmetallic and metallic;

- Fig. 6 is a sectional view in which one can observe the mechanical interlocking members;

- Fig. 7 is a perspective view of the hybrid fuel tank .

Legend of reference numbers

hybrid fuel tank (1) ;

- upper metallic semi -body (2) ;

- lower metallic semi-body (3) ;

- upper adhesive film (4) ;

- lower adhesive film (5) ;

- upper nonmetallic semi-body (6) ;

- upper nonmetallic semi-body with ring (6.1);

- lower nonmetallic semi-body (7);

- upper hybrid semi -part (8);

- lower hybrid semi-part (9);

- flange of the upper metallic semi-body (10);

- flange of the lower metallic semi -body (11) ;

- flange of the upper nonmetallic semi-body (12)

- flange of the lower nonmetallic semi-body (13) mechanical interlocking "ma members ( 14 ) , and

- mechanical interlocking "female " members ( 15) .

DETAILED DESCRIPTION OF THE . INVENTION

The present invention describes a process for manufacturing a hybrid fuel tank (1) for motor vehicles, designed to store all types of fuels, liquid and gaseous, as can be seen in Figs. 1, 2 and 3. It further concerns a new technology and design for the product, taking into account the materials used in accordance with the technologies for the process of transforming and joining which, together intended to increase the performance of the tank, ensure the fundamental features of the product and process, and still adding new configurations which allow coupling several integrated components such as the level sensor pump, piping for connecting to the vent and filling tube, gases valves, amongst others.

The present invention further describes a hybrid fuel tank (1) for motor vehicles which, as a product, provides total impermeability, lower weight than prior art fuel tanks and corrosion resistance in contact with fuels.

The hybrid fuel tank (1) technical features refer to the permeability of the set, resulting in reduction of evaporative emissions to the atmosphere, to the average specific weight of products, that directly reduce fuel consumption of the vehicle, to corrosion resistance -related to the use of new fuels chemically more aggressive, and to adopted production technologies which are considered critical to the technical advancement in this type of products and are the only way to achieve improvements in its performance, responding more effectively to matters that are currently in discussion at a global level, such as pollution, environmental impact and consumption of petroleum products.

This innovative concept presents a strong interaction between materials which are completely different, providing differentiating features to the hybrid fuel tank (1) through the combination of their benefits and advantages.

Process for manu acturing a hybrid fuel tank (1)

The process for manufacturing a hybrid fuel tank (1) for motor vehicles designed to store all types of fuels in general, liquids and gases, comprises the following steps :

- forming the two upper and lower inner metallic semi-bodies (2, 3) with flanges (10, 11), as can be seen in Figs. 3, 4 and 5, which are mechanically obtained by stamping and clamping-plates , by hydroforming , or by means of air pressure and temperature, the joining of their flanges (10, 11) together being made by laser welding of solid state;

forming the two upper and lower outer nonmetallic semi-bodies (6, 7) with flanges (12, 13), thermally obtained by thermoforming ;

- applying an adherent material on the metallic surface of the inner semi-bodies (2, 3) in the form of adhesive films (4, 5);

- joining together the metallic semi-bodies (2, 3) and the nonmetallic semi-bodies (6, 7);

- joining together the flanges of the nonmetallic semi-bodies (6, 7), using an external heating source generated by an electric resistance inserted in a platform with the geometric shape of the respective flanges, hot plates, between 170 °C and 180 °C in case of using a thermoplastic polymeric material, HOPE, or reinforced composite material, which activates the interaction among particles of the nonmetallic semi-bodies (6, 7), in solid/viscous state, between 125 °C and 140 °C;

- applying compression forces to the heated areas and to the two hybrid semi -parts (8, 9) formed by the referred metallic (2, 3) and nonmetallic (6, 7) semi- bodies, and cooling them afterwards to room temperature.

In forming the two outer nonmetallic semi -bodies (6, 7) by thermoforming, it is resorted to as heat source:

- to the heating the two metallic semi-bodies (2,

3 )

to electrical resistances at temperatures between 150 °C and 170 °C, and air pressure, up to 10 bar, or vacuum of -1 bar, which is controlled with the help of molds with cooling channels for temperature control, up to 30 °C-40 °C.

The adherent material on adhesive film (4, 5), as can be seen in Figs. 1 and 2, for joining together the metallic and nonmetallic semi-bodies, is thermally activated through the thermoforming temperatures of the nonmetallic material, between 80 °C and 100 °C, coming from the temperature of the hot plates when the flanges (12, 13) of such nonmetallic semi-bodies (6, 7) are joined together, being the referred joining together performed by resorting to compression forces.

After the thermoforming of the nonmetallic semi- bodies (6, 7), they are submitted to a surface treatment by electric discharge, via plasma or flame, to increase surface tension and so making it possible the adhesion of the adhesive films (4, 5) .

The adhesive films (4, 5) in external areas of the metallic semi-bodies (2, 3) are applied by:

- pulverization; or

- dispersing, in viscous state, in the form of strands .

The fixation of the metallic semi-bodies (2, 3) with the nonmetallic semi-bodies (6, 7) can also be performed without the adherent materials (4, 5) when using:

mechanical interlocking "male" members (14) which are fixed in external areas of the metallic semi- bodies (2 , 3 ) ;

- mechanical interlocking "female" members (15) which are fixed in internal or external areas of the nonmetallic semi-bodies (6, 7) ;

- these interlocking members can be made of metal or plastic material .

Such fixation of the metallic semi-bodies (2, 3) with the nonmetallic semi-bodies (6, 7) can also be carried out using adherent materials (4, 5) and mechanical interlocking members.

In the thermoforming of the nonmetallic semi-body (6), an opening is formed shaped as threaded ring (6.1), as can be seen in Fig. 3.

The joining together of the metallic semi-bodies (2, 3) (these previously joined together) with the translucent nonmetallic semi-bodies (6, 7) is performed by means of a low power laser, 50 to 150 W, which gradually activates the adhesive films (4, 5).

The two hybrid semi-parts (8, 9) consisting in (2, 3) and (6, 7) are joined together by means of laser welding, by means of electrical resistance heating of the flanges, and using a consumable material, AlSi alloy, placed between the two flanges (10, 11) . PRODUCT

The hybrid fuel tank (1) consists of six integrated parts represented in Figs. 1, 2 and 3, the inner body, the intermediate elements and the outer layer.

The hybrid fuel tank (1) for motor vehicles which is intended to be protected is produced in accordance with the operations previously referred to. This tank comprises:

a set of two metallic semi-bodies (2, 3) , joined together by means of two flanges (10, 11) with dimensions between 5 and 10 mm, being the thickness of each referred semi -body between 0.8 and 1,5mm;

- a set of two nonmetallic semi-bodies (6, 7) , joined together by means of two flanges (12, 13), which act as structural reinforcement;

- an intermediate layer of adherent material in the form of film (4, 5) placed on the external surface of the semi-bodies (2, 3) to join together the inner metallic semi-bodies (2, 3) and the outer nonmetallic semi-bodies (6, 7) ;

mechanical interlocking members in the intermediate layer which promotes coupling between inner metallic semi-bodies (2, 3) and outer nonmetallic semi- bodies (6, 7) ;

the set of the two outer nonmetallic semi -bodies (6, 7) with the two inner metallic semi-bodies (2, 3) forming a hybrid product comprising two hybrid semi -parts (8, 9) . In the hybrid fuel tank (1) for motor vehicles, the metallic bodies (2, 3) are made from non-ferrous treated alloys, particularly aluminum alloys, and from coated or chromium/nickel steel.

The nonmetallic semi-bodies (6, 7) are made from composite or polymeric material, being translucent to allow the passing through of the laser beam to reach the adhesive film (4, 5), preferably in a material composed by having 20% of talc in HDPE configuration, with thickness ranging between 2.0 and 4.0mm.

The hybrid fuel tank (1) is provided with openings for placement and support of components such as valves and a ventilation system.

The hybrid fuel tank (1) further comprises:

- adhesive films (4, 5) thermally activated, which have a polymer, epoxy, water and/or aqueous base;

- mechanical locking members fixed to the outside of the metallic bodies (2, 3) , as can be seen in

Fig. 7, and to the inside area of nonmetallic bodies (6,

7) . As it will be apparent to an expert, various changes of detail are possible which however should be included within the scope of present invention.

The invention should only be limited by the spirit of following claims.