Vehicle load-bearing structure

A vehicle load-bearing structure includes a cell made of composite materials and composed of a plurality of components joined to each other by at least one joining system to form a single structure; the cell is made up of a number n of components between 3 and 8, that is 3<n<8.

This application is the National Phase of International Application PCT/IB2017/057893 filed Dec. 13, 2017 which designated the U.S.

This application claims priority to Italian Patent Application No. 102016000130313 filed Dec. 22, 2016, which application is incorporated by reference herein.

TECHNICAL FIELD

This invention relates to a vehicle structure, and more specifically, a structure made of a composite material and intended for use as a “monocoque” for high powered, super sports cars.

BACKGROUND ART

As is known, monocoques of composite materials, in particular carbon fibre reinforced polymers, generally designed as single structures, have been developed for super sports cars in the horsepower range of approximately 500 HP to 1200 HP.

Most of the structures known as composite material “monocoques”, however, are in actual fact made up of different, separately cast components assembled using known fastening technologies to form a single structure.

The separate components, therefore, are first made and then assembled at a later stage to obtain the “monocoque” which constitutes a single rigid structure bearing the load of other parts of the vehicle.

Patent document EP2683535 in the name of the same applicant as the present, relates to a process for manufacturing composite material products, in particular shells, or cells, and roofs for monocoques of motor vehicles.

As may be inferred from that document, even modern monocoque solutions are made up of a plurality of components which are made and assembled in separate stages to form the single structure.

Prior art monocoques are therefore complex and their production involves a long and intricate chain of operations. Once the design of the structure as a whole has been completed, it cannot be modified owing to the large number of components needed to make it.

For example, if a monocoque for a rear engine car has been made, it has to be designed anew for a front engine car.

DISCLOSURE OF THE INVENTION

In this context, the main purpose of this invention is to propose a vehicle structure to overcome the above mentioned disadvantages.

The aim of this disclosure is to propose a vehicle structure which is easy to adapt to different vehicle configurations.

Another aim of this description is to propose a vehicle structure which is made up of a significantly reduced number of parts compared to prior art solutions.

The technical purpose indicated and the aims specified are substantially achieved by a vehicle structure comprising features as disclosed herein.

This description relates to a vehicle load-bearing structure intended for use as a monocoque for high powered, super sports cars (1000 hp and over), with two- or four-wheel drive, hybrid or internal combustion engine and two or four seats.

One aspect of this description consists in the reduced number of individual structural components, each of which is characterized by a single moulding direction, that is, a single direction of extracting the component from the mould.

In one embodiment of it, a vehicle load bearing structure comprises a cell made of composite materials, preferably carbon fibre reinforced polymers CFRP.

The cell comprises a number n of components between 3 and 8, that is 3<n<8 and at least one system for joining the components to each other to form a single structure.

In a first embodiment, the cell comprises a first component of composite material which may consist of a tub comprising at least a front wall, a rear wall, a first side wall, a second side wall and a bottom wall, together at least partly delimiting the vehicle interior, a second component of composite material which may consist of a front support joined at least to the front wall of the tub on the side opposite to the vehicle interior, a third component of composite material which may consist of a rear support joined at least to the rear wall on the side opposite to the vehicle interior, a fourth component of composite material which may consist of a first longitudinal member joined at least to the first side wall on the side opposite to the vehicle interior, a fifth component of composite material which may consist of a second longitudinal member joined at least to the second side wall on the side opposite to the vehicle interior.

In one embodiment, therefore, the cell is composed of a total of five components joined to each other.

The resulting vehicle structure is characterized by a high level of simplicity, made up of a small number of highly integrated parts, where many functional surfaces are obtained directly in the single operation of moulding the respective component. This feature can allow saving weight because there is no need for fastening elements such as screws, brackets or flanges, which are, for example, formed directly on the raw component leaving the mould.

According to one aspect of the description, the components do not have undercuts, which allows tooling to be greatly simplified, thereby saving on investments and reducing processing times through the use of short cycle time technologies, allowing savings on variable costs.

For the same rigidity, the structures thus obtainable can weigh up to 30% less and can be produced in 44% less time and at a cost which is 30% lower.

The monocoque preferably comprises an internal tub which defines the space intended for vehicle occupants, a front support which allows making a layered section and connecting the structure to the front frame, a rear support which also acts as a shock absorber for lateral and rear impacts and for connecting to a rear frame, two side elements—for example, the sills—which also have a structural function not only to absorb lateral impacts but also to transmit loads between the front and rear of the vehicle, and an upper element or assembly which acts, for example, as a roof and/or as a support for the windshield and/or as a support for the rear window.

According to one aspect of the description, the components, after being produced, are assembled together preferably thanks to specially made interface surfaces and fixed, for example, by gluing and/or co-bonding and/or rivets and/or screws or other method.

In one embodiment, the rear support may be made by assembling different absorption elements on a moulded element common to different types of cars.

That way, it is possible to make cars with different absorption properties using a single moulded element in combination with different absorption elements.

In one embodiment, the sills may be made using two half-shells, each with a single moulding axis. That way, it is possible to obtain a sill which is more robust thanks to the closed cross section and which can be glued or screwed to the tub without interposed flanges or the like.

According to another aspect of the description, the upper assembly can be broken down, for example, into two distinct elements, one internal and one external, both moulded in a single direction.

The assembly is more rigid, thanks to the closed cross section of the pillars and has a better surface finish on the inside.

According to one aspect of the description, the front support and the sills may be preformed so as to also constitute the front frame.

According to another aspect of the description, the rear support and the sills may be preformed so as to also constitute the rear frame.

According to one aspect of the description, this vehicle structure allows making two or more car types by modifying just some of the components of the assembly: for example, modifying the upper assembly allows obtaining a monocoque for a two-seater sports car or a roadster; modifying the front support and the sills allows obtaining a monocoque for a front engine car; modifying the sills allows obtaining a monocoque for a long-base car; modifying the rear support or the front support allows obtaining a monocoque for a car whose design is different from the original—for example, it is possible to obtain a monocoque for a GT car.

With reference toFIGS. 1, 2 and 3, the numeral100denotes a vehicle structure having a load bearing function; inFIGS. 1 and 3, the structure100is shown in exploded views for descriptive purposes.

The structure100preferably constitutes what is known as a “monocoque” for a super sports car, generally a car in the horsepower range of approximately 500 HP to 1200 HP, not illustrated.

In cars of this type, relevant to this specification, the monocoque is a single, rigid structure with load-bearing function and is preferably made of carbon fibre reinforced polymers, known in the trade by the acronym CFRP.

In alternative embodiments, other materials or other matrices or other reinforcement fibres may be used.

The structure100according to this description comprises a cell1is made up of a number n of components between 3 and 8, that is 3<n<8.

The cell1at least one system for joining the separate components to each other to form a single or monolithic structure.

The systems for joining the carbon fibre reinforced polymer components to each other are substantially known and not described in detail.

Generally speaking in this description, reference to components or elements joined to each other means the components or elements are joined by a corresponding joining system.

In these joining systems, the components can, for example, be glued, riveted or screwed to each other or joined by a method known as “co-bonding”.

In one embodiment, the cell1itself constitutes the entire monocoque of the vehicle.

With reference toFIGS. 1 and 3in particular, it may be noted that in one embodiment, the cell1is made by joining five components.

As mentioned above, the components are made preferably of carbon fibre reinforced polymers, individually moulded, but the use of other materials is also possible.

A first component2of the cell1consists of a tub which defines the interior101of the vehicle, that is, it delimits or identifies a space inside the vehicle, to be occupied by the driver and passengers.

The first component or tub2comprises a front wall3, a rear wall4, a first side wall5, a second side wall6and a bottom wall7.

The walls3,4,5and6extend from the bottom wall to define the structure of the tub2.

The first component2has a single moulding direction and does not have undercuts.

In this description, the expression “single moulding direction” is used to mean that the individual parts are made by a single movement of closing and opening a respective mould by means of a corresponding press without any further movements of accessory parts such as carriages or the like—that is to say, to mean that the individual parts do not have undercuts.

The cell1comprises a second component8consisting of a front support joined at least to the front wall3of the tub2on the side opposite to the interior101.

The second component or front support8contributes to creating a layered section of the front wall3to which a front frame for supporting other parts of the vehicle, such as, a front axle assembly, for example, is connected during the construction of a vehicle.

The second component8has a single moulding direction and does not have undercuts.

In one embodiment, the front wall3has an interface surface3a, on the outside of the interior101, for joining to the second component8.

Similarly, the second component8has an interface surface8afor joining to the first component2.

The first and second components2and8are joined by one of the aforesaid joining systems by means of the respective interface surfaces2a,8a.

In the jargon of the trade, the second component8may also be called front flame trap.

The cell1comprises a third component9consisting of a rear support joined at least to the rear wall4of the tub2on the side opposite to the interior101.

The rear support, defined by the third component9, also preferably acts as a shock absorber for rear and lateral impacts.

The rear support also constitutes a portion of the cell for connection to a rear frame during the construction of the vehicle.

The rear frame is used, for example, to support and connect the rear axle assembly and the engine and gearbox assembly of the vehicle.

The third component9has a single moulding direction and does not have undercuts.

In one embodiment, the rear wall4has an interface surface4a, on the outside of the interior101, for joining to the third component9.

Similarly, the third component9has an interface surface9afor joining to the first component2.

The first and third components2and9are joined by one of the aforesaid joining systems by means of the respective interface surfaces2a,9a.

In the jargon of the trade, the third component9may also be called rear flame trap.

With reference toFIG. 4, it may be observed that in one embodiment, the third component9comprises a main element10, preferably moulded in carbon fibre reinforced polymer composite, and at least one absorption element10aassembled on the element10.

The element10agives the element10, hence the component9, predetermined shock absorbing properties.

This configuration makes it possible, for example, to make an element10which is common to a multiplicity of different vehicles and to which the necessary absorption properties are given by means of the elements10aaccording to the type of vehicle to be made.

In an embodiment not illustrated of the cell1, the second and third components8and9are made as a single component moulded preferably in carbon fibre reinforced polymers and in turn joined to the tub2.

That way, as will become clearer as this description continues, the cell1is defined by a total of four components which are joined to each other.

The cell1comprises a fourth and a fifth component11,12consisting of a first longitudinal member and a second longitudinal member, respectively.

In the jargon of the trade, the fourth and fifth components are called “sills” and allow absorbing lateral shocks and transmitting loads between the front and rear of the vehicle.

In a preferred embodiment, the sills have a closed main cross section.

With reference toFIG. 5, it may be observed that in one embodiment, the sills11and12, only one of which is illustrated, are each made up of a first and a second half-shell13,14which are coupled to each other.

Thus, the fourth and fifth components11and12have a closed main cross section, not illustrated in detail.

The sills11and12thus obtained are robust and can be glued or screwed directly to the tub2.

The first and second half-shells13,14of the fourth and fifth components11,12each have a respective single moulding direction and do not have undercuts.

With reference toFIG. 3, in one embodiment, fourth and fifth components11,12have an open main cross section.

Preferably, the sills11and12have a single moulding direction and do not have undercuts.

The fourth component or sill11is joined at least to the aforesaid first side wall5on the side opposite the interior101and the fifth component or sill12is joined at least to the aforesaid second side wall6on the side opposite the interior101.

In a preferred embodiment, the side wall5and the side wall6each have a respective interface surface5a,6a.

Similarly, the sill11and the sill12have respective interface surfaces11aand12a.

The tub2is joined to the sills11and12by means of the interface surfaces5a,6aand the interface surfaces11a,12aof the fourth and fifth components11,12.

The components11and12might also be joined to the tub2by means of flanges not illustrated.

It should be noted that based on whether the main cross section of the sills11,12is open or closed, the interface surfaces are modified accordingly in different ways.

More specifically, in the case where the sills11,12have an open cross section, as illustrated inFIG. 3, for example, the surfaces5aand6aof the walls5and6are preferably shaped to contribute to making a structure whose main cross section is closed once coupled to the respective sill.

In one embodiment, the cell1is thus defined by five components joined to each other, that is, by the tub2to which the front support8, the rear support9and the sills11and12are joined.

In a different embodiment, as mentioned above, the cell1is defined by four components joined to each other, that is, by the tub2to which the sills11and12and a fourth component, defined by the front support8and the rear support9co-moulded as a single part, are joined.

In an embodiment not illustrated, the second component8, together with the fourth and fifth components11,12constitute a unit having a pair of protrusions extending away from the first component and defining the aforementioned front frame.

In practice, the front support8and the sills11,12may be shaped or preformed so as to also constitute the front frame.

The structure100in this embodiment, while still being defined by a limited number of components, also integrates the front frame.

In one embodiment, the third component9, and the fourth and fifth components11,12constitute a unit having a pair of protrusions extending away from the first component2and defining the aforementioned rear frame.

In practice, the rear support9and the sills11,12may be shaped or preformed so as to also constitute the front frame.

The structure100in this embodiment, while still being defined by a limited number of components, also integrates the rear frame.

In the embodiment illustrated inFIGS. 2 and 3in particular, the structure100comprises an upper assembly15made of composite material—for example, carbon fibre reinforced polymers CFRP.

In one embodiment, the upper assembly15is moulded in a single part and in a single moulding direction.

The assembly15is joined to the cell1to define a single structure; the assembly15is joined to the cell1for example by gluing.

In practice, the monocoque of the vehicle consists of the cell1, which constitutes a bottom part, and the upper assembly15.

The assembly15comprises a covering element or roof16, a first and a second front pillar17,18and a rear unit19extending from opposite sides of the roof16.

The covering element16is joined to the cell1by means of the pillars17and18and the rear unit19at the wall3and the wall4of the tub2, respectively.

The assembly15is provided with engagement elements for connecting and joining to the cell1.

In an embodiment illustrated inFIG. 6, the upper assembly15comprises a first, internal element20, directed towards the interior101when the upper assembly15is joined to the cell1, and a second, external element21, disposed on the side opposite the interior101with respect to the internal element20when the upper assembly15is joined to the cell1.

The first, internal element20comprises an internal portion22of the first pillar17, an internal portion23of the second pillar18and an internal portion24of the rear unit19.

The portions22and23are connected to each other by a crosspiece25and to the rear portion24by respective joining elements26,27which can also be considered as extensions of the corresponding portions22and23.

The internal element20of the upper assembly15is moulded as a single part and in a single moulding direction.

The second, external element21comprises a covering element or roof28, an external portion29,30of the pillars17and18and an external portion31of the rear unit19.

The internal element21of the upper assembly15is moulded as a single part and in a single moulding direction.

Joining the elements20and21allows, amongst other things, obtaining a closed cross section for the pillars17and18, giving the pillars17and18greater stiffness compared to pillars with an open cross section.

In an embodiment not illustrated, the upper assembly15comprises a first and a second front pillar and a pair of crosspieces joining the pillars to define a frame for the windshield of the vehicle.

In that case, when the assembly is joined to the cell1, substantially at the front wall3of the tub2, the load-bearing body100of a two-seater car is defined.

In an embodiment not illustrated, the upper assembly15, besides the frame for the windshield, also comprises a rear unit for supporting the rear window of the vehicle.

In that case, when the assembly15is joined to the cell1, with the windshield frame joined substantially at the front wall3of the tub2and the rear unit joined substantially at the rear wall4of the tub, the load-bearing body100of a roadster is defined.

Making the structure100with a finite, limited number of components joined to each other makes the structure100easy to modify so that different types of cars can be made by changing only a few components of the entire structure.

Since the components of the structure according to this description each have a single moulding direction, the machinery used to make them is also relatively simplified.

For example, modifying the upper assembly allows obtaining, as mentioned above, a load-bearing structure for a coupé or a two-seater or a roadster.

Modifying the second, fourth and fifth components, that is, the front support and the sills in the example described, allows obtaining, for example, a load-bearing structure for a front engine car.

Modifying the fourth and fifth components, that is, the sills in the example described, allows obtaining, for example, a load-bearing structure for a long-base car.

Modifying the third component, that is, the rear support in the example described, allows obtaining, for example, a load-bearing structure for what is known as a GT.

As mentioned, the components are made of composite materials and obtained by moulding.

The preferred moulding methods, which give the components predetermined technical properties, include those known as “Resin Transfer Moulding (RTM)”, “Braiding” e “Prepreg”.

The production processes of these methods differ in the type of carbon fibre used, the respective interlacement and the chemical composition of the synthetic resin used.

In the RTM method, the rolls of carbon fibre are preformed and impregnated with a predetermined quantity of resin. They are then heat hardened while the component is in process.

Patent document EP2574449 in the name of the same applicant as the present addresses a development of this moulding method.

In the prepreg method, the rolls of carbon fibre are pre-impregnated with a liquid, thermosetting resin and must be stored at low temperature. Next, the rolls are laminated in moulds and hardened in an autoclave at suitable heat and pressure. Components made with the prepreg method guarantee a high quality surface finish and thus constitute the preferred solution for parts to be mounted in visible positions.

The braiding method is used to make tubular components for special applications such as, for example, structural pillars and the profiles of the bottom section; interlacing is accomplished by diagonally cross-linking the fibres in different layers.