Claims:We Claim:

1. A method for manufacturing a fuel tank (100) of a vehicle, the method comprising:
introducing, a polyolefin material into a mold of a rotational molding machine;
molding, the polyolefin material, at a first predefined temperature for a first predefined time, wherein the polyolefin material forms a first layer of the fuel tank (100) in the mold;
introducing, a polyamide material into the mold of the rotational molding machine having the first layer;
molding, the polyamide material at a second predefined temperature for a second predefined time, wherein the polyamide material forms a second layer over the first layer of the fuel tank (100) in the mold; and
cooling, the mold to form the fuel tank (100),
wherein the first layer is configured to provide rigidity and stiffness to the fuel tank (100) and the second layer is configured to resist fuel permeability of the fuel tank (100).

2. The method as claimed in claim 1, wherein the polyolefin material and the polyamide material are introduced into the mold in a powdered form.

3. The method as claimed in claim 1, wherein the polyolefin material is polyethylene.

4. The method as claimed in claim 1, wherein the polyamide material is Nylon, preferably Nylon-6.

5. The method as claimed in claim 1, wherein the first layer forms an outer layer (1) of the fuel tank (100).

6. The method as claimed in claim 1, wherein the second layer forms an inner layer (2) of the fuel tank (100).

7. The method as claimed in claim 1, wherein the inner layer (2) formed from the polyamide material resists fuel permeability at most of 2 g/m2/day.

8. The method as claimed in claim1, wherein the mold is air cooled for a predefined cooling time.

9. The method as claimed in claim 1, wherein the first predefined temperature is at least 100? and the second predefined temperature is at least 200?.

10. The method as claimed in claim 1, wherein the first layer and the second layer bond together without binding materials.

11. A fuel tank (100) for a vehicle manufactured by the method as claimed in claim 1, the fuel tank (100) comprising:
an outer layer (1) formed of a polyolefin material; and
an inner layer (2) formed of a polyamide material bonded with the outer layer (1).
12. The fuel tank (100) as claimed in claim 12, wherein a thickness of the outer layer (1) is at least 1mm.

13. The fuel tank (100) as claimed in claim 12, wherein the thickness of the inner layer (2) is at least 1mm.

14. The fuel tank (100) as claimed in claim 12, wherein the polyolefin material is polyethylene.

15. The fuel tank (100) as claimed in claim 12, wherein the polyamide material is Nylon, preferably Nylon-6.

Dated this 15th of March 2021
Gopinath Arenur Shankararaj
IN/PA – 1852
OF K&S PARTNERS
AGENT OF THE APPLICANT
, Description:TECHNICAL FIELD
Present disclosure, in general, relates to the field of automobiles. Particularly, but not exclusively, the present disclosure relates to a fuel tank of a vehicle. Further, embodiments of the present disclosure disclose a method for manufacturing a fuel tank of the vehicle.

BACKGROUND OF THE DISCLOSURE

Generally, vehicles employing internal combustion engines as a prime mover require fuel to operate. The fuel may be available at an external source and have to be stored in the vehicle to power the internal combustion engine. The fuel may be stored in fuel tanks which are provisioned in the vehicle. The fuel tanks are conventionally fabricated from metal, such as steel or aluminum. However, such fuel tanks cannot be manufactured with complex shapes and are generally rectangular is shape. This gives limitations in vehicle packaging especially for the underbody systems/ assemblies, where compact design becomes difficult. Further, the fuel tanks made from metals are heavy, due to which, load acting on the vehicle increases and thereby fuel efficiency of the vehicle decreases. Also, with passage of time, the fuel tank made from metals may degrade due to corrosion.

With advent of technology, the metal fuel tanks have been replaced with polymeric fuel tanks. The polymeric fuel tanks are light and can be manufactured in complex shapes and sizes, at comparatively affordable expenses. This offers great design freedom while packaging/routing assemblies/systems. Further, the polymeric fuel tanks do not undergo corrosion and have a longer operational life. Conventionally, the polymeric fuel tanks are manufactured by employing a blow molding or rotational molding process. The blow molding process enables the fuel tank to be manufactured with single or multiple layers, while rotational molding process is useful for generally making single layer fuel tanks. Single layer rotational molded fuel tanks are common for diesel fuel, however gasoline fuel tanks have multiple layers and are molded using blow molding process. Gasoline tanks need to meet stricter fuel permeability requirements of at most 2 g/m2/day. This fuel permeability requirement cannot be met by single layer tanks and hence use of multi layers is essential. For example, the fuel tank may include a five-layer construction to achieve desired level of fuel permeability requirement. However, the blow molding process is expensive due to the high tooling cost, high processing cost and expensive raw material. Further, one of the materials in the multi layers is a barrier layer which is expensive and shortage of this material may pose serious concern. This barrier layer is responsible to meet the fuel permeability requirements.

Further, to overcome the drawbacks of the blow molding process, the fuel tanks may be manufactured using a rotational molding process. The rotational molding process involves a heated hollow mold which is filled with charge of material and then slowly rotated which causes the charge of material to soften and disperse and stick to the walls of the mold. However, the rotational molding process is restricted in terms of layers that may be molded which may be insufficient to restrict fuel permeability. Further, to this, there is no rotational molding material grade available which restricts fuel permeation.

The present disclosure is directed to overcome one or more limitations stated above or any other limitations associated with the conventional mechanisms.

SUMMARY OF THE DISCLOSURE

One or more shortcomings of the prior art are overcome by a method and device as claimed and additional advantages are provided through the method and device as claimed in the present disclosure. Additional features and advantages are realized through the techniques of the present disclosure. Other embodiments and aspects of the disclosure are described in detail herein and are considered a part of the claimed disclosure.

In one non-limiting embodiment of the present disclosure a method for manufacturing a fuel tank of a vehicle is disclosed. The method includes the step of introducing a polyolefin material into a mold of a rotational molding machine. The polyolefin material upon introduction into the mold is molded at a first predefined temperature for a first predefined time, where the polyolefin material forms a first layer of the fuel tank, which is an outer layer of the fuel tank. Further, a polyamide material is introduced into the mold of the rotational molding machine having the first polyolefinic layer. The polyamide material is then molded at a second predefined temperature for a second predefined time, where the polyamide material forms a second layer as an inner layer over the first polyolefinic layer i.e. the outer layer of the fuel tank in the mold after which the mold is cooled to form the fuel tank. The first layer is configured to provide rigidity and stiffness to the fuel tank and the second layer is configured to control and resist the fuel permeability of the fuel tank.
In an embodiment, the polyolefin material and the polyamide material are introduced into the mold in a powdered form.

In an embodiment, the polyolefin material is polyethylene.

In an embodiment, the polyamide material is Nylon, preferably Nylon-6 material.

In an embodiment, the first layer forms an outer layer of the fuel tank.

In an embodiment, the second layer forms an inner layer of the fuel tank.

In an embodiment, the inner layer formed from the polyamide material restricts the fuel permeability to meet the requirement of at most 2 g/m2/day.

In an embodiment, the mold is air cooled for a predefined cooling time.

In an embodiment, the first predefined temperature is at least 100? and the second predefined temperature is at least 200?.

In an embodiment, the first layer and the second layer bond together without any binding material.

In another non-limiting embodiment of the present disclosure, a fuel tank for a vehicle is disclosed. The fuel tank includes an outer layer formed of a polyolefin material and an inner layer formed of a polyamide material bond with the outer layer.

In an embodiment, a thickness of the outer layer is at least 1mm.

In an embodiment, wherein the thickness of the inner layer is at least 1mm.

The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

The novel features and characteristic of the disclosure are set forth in the appended claims. The disclosure itself, however, as well as a preferred mode of use, further objectives, and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiments when read in conjunction with the accompanying figures. One or more embodiments are now described, by way of example only, with reference to the accompanying figures wherein like reference numerals represent like elements and in which:

Figure 1 illustrates a sectional view of a fuel tank of a vehicle, in accordance with an embodiment of the present disclosure.

Figure 2 is a flow chart of a method for manufacturing the fuel tank of Figure 1, in accordance with an embodiment of the present disclosure.

The figures depict embodiments of the disclosure for purposes of illustration only. One skilled in the art will readily recognize from the following description that alternative embodiments of the system and method illustrated herein may be employed without departing from the principles of the disclosure described herein.

DETAILED DESCRIPTION

The foregoing has broadly outlined the features and technical advantages of the present disclosure in order that the detailed description of the disclosure that follows may be better understood. Additional features and advantages of the disclosure will be described hereinafter which form the subject of the claims of the disclosure. It should be appreciated by those skilled in the art that, the conception and specific embodiments disclosed may be readily utilized as a basis for modifying other methods, processes, devices, assemblies, systems, and mechanisms for carrying out the same purposes of the present disclosure. It should also be realized by those skilled in the art that, such equivalent constructions do not depart from the scope of the disclosure as set forth in the appended claims. The novel features which are believed to be characteristics of the disclosure, to its system, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the present disclosure.

The terms “comprises”, “comprising”, or any other variations thereof, are intended to cover a non-exclusive inclusions, such that a mechanism, an assembly, or a device that comprises a list of components or steps does not include only those components or steps but may include other components or steps not expressly listed or inherent to such setup or device or method. In other words, one or more elements in a system or apparatus proceeded by “comprises… a” does not, without more constraints, preclude the existence of other elements or additional elements in the system or apparatus.

Vehicles employing internal combustion engines as a prime mover require fuel to operate. The fuel may be available at an external source and have to be stored in the vehicle to power the internal combustion engine. The fuel may be stored in fuel tanks which are provisioned in the vehicle. The fuel tanks may be manufactured with complex shapes and sizes. The polymeric fuel tanks are manufactured using rotational molding process. The rotational molding process involves a heated hollow mold which is filled with a charge of material. The mold is then slowly rotated which causes the charge of material to soften due to the heat and disperse and stick to the walls of the mold upon rotation. The mold after the heating process is cooled such that the softened material stuck to the walls of the mold solidifies and forms the required shape with the required rigidity and stiffness.

In accordance with various embodiments of the present disclosure, a method for manufacturing a fuel tank of a vehicle is disclosed. The method includes steps of introducing a polyolefin material into a mold of a rotational molding machine. The polyolefin material is then molded at a first predefined temperature for a first predefined time, where the polyolefin material forms a first layer which is the outer layer of the fuel tank in the mold. Further, a polyamide material is introduced into the mold of the rotational molding machine having the first layer. The polyamide material is molded at a second predefined temperature for a second predefined time, where the polyamide material forms a second layer, which is the inner layer of the fuel tank, over the first layer of the fuel tank in the mold after which the mold is cooled to form the fuel tank. The first layer is configured to provide rigidity and stiffness to the fuel tank and the second layer is configured to control and resist fuel permeability of the fuel tank.

Reference will now be made to the exemplary embodiments of the disclosure, as illustrated in the accompanying drawings. Wherever possible, same numerals will be used to refer to the same or like parts. The following paragraphs describe the present disclosure with reference to Figures 1 and 2.

Figure 1 is an exemplary embodiment of the present disclosure which illustrates a sectional view of a fuel tank (100) of a vehicle. The fuel tank (100) may be configured to be fit into all types of vehicles, including, but not limited to, a passenger vehicle, commercial vehicles, motorcycle, scooter, and any other requiring storage of fuel for operating an internal combustion engine as a prime mover, particularly vehicles running using gasoline fuel. The fuel tank (100) may be adapted to receive and contain fuel which may be at least one of petrol, diesel, CNG, LPG, hydrogen, ethanol, bio- fuels and any other fuel that may be employed to operate the internal combustion engine, particularly gasoline fuel. The fuel tank (100) may be manufactured with various shapes and sizes based on space availability within the vehicle and may have provisions to house sub-assemblies/systems on an external surface in particular on underbody of the vehicle.

In the illustrative embodiment, the fuel tank (100) is manufactured by a rotational molding process and includes an outer layer (1) formed by a polyolefin material. Further, an inner layer (2) of the fuel tank (100) is formed of a polyamide material, which is formed over the outer layer (1). That is, the inner layer (2) may be formed over the outer layer (1) with a strong cohesive bond. The polyolefin material in the outer layer (1) may be configured to provide rigidity and stiffness to the fuel tank (100) and resistance from foreign particles. Furthermore, the outer layer (1) may be non-reactive and retains the physical properties without any changes. The polyamide material in the inner layer (2) may be configured to contact the fuel stored within the fuel tank (100) and provide resistance to fuel permeability. Also, the polyamide material in the inner layer (2) adheres to the polyolefin material in the outer layer (1) when heated to form a cohesive bond.

Further, the outer layer (1) of the fuel tank (100) may have a thickness of at least 1mm and the inner layer (2) of the fuel tank (100) may have a thickness of at least 1mm.
In an exemplary embodiment, the polyolefin material may be a polyethylene. Further, the polyamide material is Nylon, preferably Nylon-6.

The rotational molding process for manufacturing the fuel tank (100) includes the use of a mold in which the raw materials are introduced to be molded. Further, the mold may be fixed in a rotational molding machine. The rotational molding machine may include a mechanism to accommodate the mold and rotate such mold in 3-directional axis. Furthermore, the rotational molding machine may be integrated or externally coupled with a heater to heat the mold. The rotational molding machine may also be positioned proximal to or include a cooling system to suitably cool the mold for producing the fuel tank (100).

To manufacture the fuel tank (100), the polyolefin material is introduced into a mold of a rotational molding machine. The polyolefin material may be in a powdered form. The mold of the rotational molding machine may be selected based on the size and shape requirement of the fuel tank (100) and the quantity of the polyolefin material being introduced into the mold. In an embodiment, the mold may be defined with an opening to introduce raw material into the mold and may be selectively opened and closed with a lid. Upon introducing the polyolefin polymer material, the mold is closed air tight. On closing the mold, the heater may be actuated. The heater is configured to heat the mold to a first predefined temperature such that, the polyolefin material in the powdered form may soften and attain a softened state capable of sticking along periphery of the mold. In an embodiment, the first predetermined temperature is selected based on softening point of the polyolefin material. Further, the rotational molding machine simultaneously rotates the mold during heating of the mold. This rotation happens in one or two or three directions based on the geometry of the fuel tank (100). The rotation of the mold enables the polyolefin material in the softened state to evenly distribute the polyolefin material over an inner surface of the mold. The heating and rotation of the mold with the polyolefin material within the mold is carried out for a first predefined time. The first predefined time is selected based on time required for the polyolefin material in the softened state and build desired thickness by evenly distributing the material over the inner layer (2) of the mold and form a first layer of the fuel tank (100). In an embodiment, the polyolefin material in the softened state may gradually solidify over such first predefined time to form the first layer of the fuel tank (100)

Further, after the first predefined time, the rotational molding process may be halted. After halting the rotational molding process, the polyamide material may be introduced into the mold of the rotational molding machine having the first layer. The polyamide material introduced into the mold may be in the powdered form. The quantity of the polyamide material introduced into the mold may depend on the dimension of the fuel tank (100) being manufactured. Upon introduction of the of the polyamide material the heater may be actuated. The heater may be configured to heat the mold to a second predefined temperature such that, the polyamide material in the powdered from softens and attains a softened state. In an embodiment, the second predetermined temperature is selected based on the softening point of the polyamide material. Further, the rotational molding machine simultaneously rotates the mold during heating of the mold. This rotation may happen in one or two or three directions based on the geometry of the fuel tank (100). The rotation of the mold enables the polyamide material in the softened state to evenly distribute over the first layer within the mold. The heating and rotation of the mold with the polyamide material within the mold is carried out for a second predefined time. The second predefined time is selected based on the time required for the polyamide material in the softened state and build desired thickness by evenly distributing the material over the first layer and form a second layer.

Furthermore, the mold after the second predefined time may be subjected to cooling. The cooling of the mold is carried out for a predefined cooling time. The predefined cooling time may be the time required for the first layer and the second layer in the softened state to solidify upon supplying cooling air. When the mold is cooled for the predetermined cooling time, the first layer and the second layer solidify and form the fuel tank (100). In an embodiment, the cooling may be carried out by cooling fans positioned proximal to the mold and cooling channels on the mold. Additionally, after cooling the mold for the predefined cooling time, the mold is removed from the rotational molding machine and opened to obtain the fuel tank (100).

In an embodiment, the first layer may be configured to provide rigidity and stiffness to the fuel tank (100) and the second layer may be configured to control and resist fuel permeability within the fuel tank (100).

In an embodiment, the first layer may form the outer layer (1) of the fuel tank (100) and the second layer may form the inner most layer (2) of the fuel tank (100).
In an embodiment, the inner most layer (2) formed from the polyamide material which restricts fuel permeability to at most of 2 g/m2/day.

In an embodiment, the first predefined temperature may be at least 100?. Further, the second predefined temperature may be at least 200?.

In an embodiment, the first predefined temperature and the second predefined temperature may have the same temperature when the temperature is above a softening temperature of both the polyolefin material and the polyamide material.

In an embodiment, the first predefined time is at least 10 mins and the second predefined time and the cooling time are greater than the first predefined time.

In an embodiment, the polyolefin material may be used as one of but not limited to polyethylene, polypropylene, and any other polyolefin material suitable for retaining shape and exhibiting the required rigidity and stiffness for the fuel tank (100).

In an embodiment, the polyamide material may be used as one of but not limited to Nylon-6, Nylon-11, Nylon-12, and any polyamide material capable of forming thermal bond with the polyolefin material and provide required resistance to fuel permeability.

In an embodiment, the first layer and the second layer, bond or form together without any binding material. For example, the polyamide material upon attaining the softened state distributes over the first layer consisting of the polyolefin material in the softened state. The flow of the polyamide material over the polyolefin material forms cohesive bonding between polyamide and polyolefin material and bonds the first layer and the second layer.

In an embodiment, the fuel tank (100) may be manufactured by rotational molding a single layer of the polyamide material having thickness of at least 1mm. In an embodiment, the fuel tank (100) may be manufactured by rotational molding a dual layer of the polyamide with polyolefin materials, each having thickness of the at least 1mm.

In an embodiment, the polyolefin material and the polyamide material in the softened state attains a viscous flow and displaces throughout the mold upon rotation of the mold.
Referring now to Figure 2 which is an exemplary embodiment of the present disclosure illustrating a flow chart of a method for manufacturing the fuel tank (100) of the vehicle.

The order in which the method is described is not intended to be construed as a limitation, and any number of the described method blocks may be combined in any order to implement the method. Additionally, individual blocks may be deleted from the methods without departing from the scope of the subject matter described herein. Furthermore, the method can be implemented in any suitable hardware, software, firmware, or combination thereof.

At block 201, the polyolefin material may be introduced into the mold of the rotational molding machine. The polyolefin material introduced into the mold may be in a powdered form. The rotational molding machine may be configured to rotate the mold in the 3-directional axis.

At block 202, the mold containing the polyolefin material may be heated to the first predefined temperature by the heater provisioned with the rotational molding machine for the first predefined time. The polyolefin material when heated to the first predefined temperature for the first predefined time forms the first layer of the fuel tank (100) in the mold.

At block 203, the rotation and the heating of the mold may be halted, and the polyamide material may be introduced into the mold of the rotational molding machine having the first layer.

At block 204, the mold containing the polyolefin material formed as the first layer and the polyamide material may be heated to the second predefined temperature by the heater for the second predefined time. The polyamide material when heated to the second predefined temperature for the second predefined time forms the second layer over the first layer of the fuel tank (100) in the mold.

At block 205, the mold after the second predefined time is subjected to cooling for the predefined cooling time. The first layer and the second layer upon cooling solidifies within the mold and forms the fuel tank (100).

Further, experiments were conducted with the fuel tank (100) manufactured by the method as described in Figure 2 and the resulting physical parameters were noted as seen in Table 1 below.

Trial Material Inner layer Weight Outer layer
Material Thickness
(mm) (Kgs) Material Thickness
(mm)
1 Monolayer – (Single layered) Polyamide Polyamide (Nylon-6/Nylon-11) 1 0.6
2 Dual Layer - Polyamide
& Polyolefin Polyamide (Nylon-6/Nylon-11) 1 0.6 Polyethylene 1
3 Dual Layer - Polyamide
& Polyolefin Polyamide (Nylon-6/Nylon-11) 1 0.6 Polyethylene 2
4 Monolayer - Polyamide Polyamide (Nylon-6/Nylon-11) 1 1.8 ----

Table 1

Furthermore, tests were conducted with the fuel tank (100) manufactured by the method as described in Figure 2. A fuel permeation test was conducted where the fuel tank (100) was pre-conditioned by filling 90% of the fuel tank (100) with a reference fuel and kept at room temperature for 21 days. Upon completion of the test, the fuel permeability values was observed to be a maximum of 0.31gm/m2/24hrs. Additionally, an environment test was conducted by subjecting the fuel tank (100) to a maximum temperature of 85°C for 72hrs and a minimum temperature of -40°C for 24hrs and to humidity test at +40°C, at 95% RH for 72 hrs. After completion of the environment test no delamination and no deterioration of the fuel tank (100) was observed. Furthermore, a fuel compatibility test was conducted by filling the fuel tank (100) with gasoline at room temperature for 30 days. Upon completion of the test no deterioration or stickiness or delamination of the inner surface of the fuel tank (100) was observed.

In an embodiment, gasoline, or petrol fuel tank (100) that conventionally required five layers having a barrier layer to meet the fuel permeability requirement may be manufactured with two layers without the barrier layer.

In an embodiment, the capex cost, processing cost and tool cost for the fuel tank (100) may be lower than a blow molded tank.

In an embodiment, the fuel tank (100) does not require expensive barrier material to meet the fuel permeability requirement.

In an embodiment, the fuel tank (100) does not require any additive to bond the first layer and the second layer.

Equivalents:
Embodiments herein and the various features and advantageous details thereof are explained with reference to the non-limiting embodiments in the description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.

The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within scope of the embodiments as described herein.

Throughout this specification the word “comprise”, or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers, or steps, but not the exclusion of any other element, integer or step, or group of elements, integers, or steps.

The use of the expression “at least” or “at least one” suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the disclosure to achieve one or more of the desired objects or results.

Any discussion of documents, acts, materials, devices, articles and the like that has been included in this specification is solely for the purpose of providing a context for the disclosure. It is not to be taken as an admission that any or all of these matters form a part of the prior art base or were common general knowledge in the field relevant to the disclosure as it existed anywhere before the priority date of this application.

The numerical values mentioned for the various physical parameters, dimensions or quantities are only approximations and it is envisaged that the values higher/lower than the numerical values assigned to the parameters, dimensions or quantities fall within the scope of the disclosure, unless there is a statement in the specification specific to the contrary.

While considerable emphasis has been placed herein on the particular features of this disclosure, it will be appreciated that various modifications can be made, and that many changes can be made in the preferred embodiments without departing from the principles of the disclosure. These and other modifications in the nature of the disclosure or the preferred embodiments will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation.

Referral Numerals:

Reference Number Description
100 Fuel tank
1 Outer layer
2 Inner layer