PROCESS AND PLANT FOR PRODUCING A MODULAR STRUCTURE, IN PARTICULAR A CHASSIS FOR MOTOR VEHICLES AND A MODULE FOR SUCH CHASSIS

The present invention refers to a process and a plant for producing a modular structure, in particular a chassis for motor vehicles and a module for such chassis.

More in particular, the invention refers to a process and a plant for producing modules for a chassis or for a portion of chassis for motor vehicles made through 3D printing.

Still in particular, the invention refers to modules for a chassis or for a portion of chassis for motor vehicles made through 3D printing. Herein below, the term chassis will designate both a complete chassis and a portion of chassis, for example designed to be fastened to a chassis made of carbon fibre.

Processes and plants are known for producing chassis for motor vehicles made through metal components (mainly steel and/or aluminium) , first moulded and then electro-welded.

These first known chassis, however, have the problem that the high safety levels (crash test) reached thereby can be improved with difficulty in a meaningful way without burdening the vehicle mass .

This problem is solved by chassis for motor vehicles made of composite materials, like shells called CFRP (Carbon Fibre Reinforced Polymer) , or in a lesser way by chassis made of a mix of materials comprising steel and aluminium alloys, like the shells called "space frame", which guarantee high performances in terms of torsion stiffness and resistance to front and side impacts, even having a reduced weight.

These other known chassis, mainly the CFRP ones, however have the problem of a high production cost due to the complex manufacturing process, so that they are currently used only for particular uses (very high range motor vehicles and Motorsports) .

The need of making light-weight chassis for motor vehicles is given above all by the fact that in electric motor vehicles which, together with the hybrid ones, are in perspective a more and more important portion in worldwide circulating vehicles, the weight of the batteries imposes a sure and scarcely reducible increase of the mass, unless very low autonomy levels are accepted. Therefore, with the same work-load being transported and the same dynamic performances, a plus equal to about 25/35% of incremental weight is assigned with respect to vehicles equipped with endothermal motors.

Documents US-A1-2017/050677 and EP-A1-3 263 237 disclose prior art processes for producing chassis for motor vehicles.

Object of the present invention is solving the above prior art problems, by providing a process and a plant for producing a chassis for motor vehicles and a module for such chassis which guarantee:

competitive production costs and investments to start a new model with respect to currently used technologies used in medium/large series;

flexibility, with the chance of modifying vehicle sizes/characteristics without having to pay the high investments required by the need of new dies and with the chance of following technologic evolutions of batteries with smaller and smaller overall sizes, in favour of the increase of load volumes;

strongly reduced prototyping and industrializing times with respect to those of production processes currently adopted by the majority of shell manufacturers, and therefore quickness from the point of view of the Time to Market .

The above and other objects and advantages of the invention, as will result from the following description, are obtained with a chassis for motor vehicles and a module for such chassis as claimed in the independent claims. Preferred embodiments and non-trivial variations of the present invention are the subject matter of the dependent claims.

It is intended that all enclosed claims are an integral part of the present description.

It will be immediately obvious that numerous variations and modifications (for example related to shape, sizes, materials, manufacturing processes, arrangements and parts with equivalent functionality) can be made to what is described, without departing from the scope of the invention as appears from the enclosed claims.

The present invention will be better described by a preferred embodiment, provided as a non limiting example, with reference to the enclosed drawings, in which:

Figure 1 shows a perspective view of a chassis according to the present invention;

Figure 2 shows a perspective view pointing out the modules of a chassis according to the present invention;

Figure 3 shows a front view of a chassis according to the present invention;

Figure 4 shows a perspective view of two modules of a chassis according to the present invention;

Figure 5.1 shows a perspective view and a side view of an embodiment of two modules of a chassis according to the present invention; Figure 5.2 shows a perspective view and a side view of an embodiment of two modules of a chassis according to the present invention; - Figure 5.3 shows a perspective view and a side view of an embodiment of two modules of a chassis according to the present invention; Figure 5.4 shows a perspective view and a side view of an embodiment of two modules of a chassis according to the present invention; and

Figure 6 shows a perspective view of a tank for assembling a chassis according to the present invention.

With reference to the Figures, the chassis 10 for motor vehicles of the invention comprises at least one first module 11 and at least one second module 12, the first module 11 having a face with at least one first surface 15 complementary with a second surface 16 of a face of the second module 12, the first and second surfaces respectively comprising first 25 and second 26 interlocking elements, designed to be mutually interlocked to fasten the first module 11 and the second module 12, with the first surface 15 and the second surface 16 mutually abutted.

In a preferred way, the first surface 15 and the second surface 16 have the same shape and are mutually matching, at least partially, when the first module 11 is fastened to the second module 12, with the first 25 and the second 26 interlocking elements mutually interlocked.

Preferably, the chassis 10 for motor vehicles of the invention comprises a plurality of the first modules 11, and a plurality of the second modules

12, each of the first modules 11 having a face with a first surface 15 complementary with a second surface 16 of a face of at least one of the second modules 12, the first and second surfaces respectively comprising the first 25 and the second 26 interlocking elements, designed to be mutually interlocked to fasten the first module 11 and the second module 12, with the first surface 15 and the second surface 16 mutually abutted, in a preferred way at least partially matching.

In a first embodiment of the modules 11, 12 for the chassis 10 for motor vehicles of the invention shown in Figure 5.1, the first 25 and the second 26 interlocking elements are made with projecting elements and corresponding recesses made respectively on the first surface 15 and on the second surface 16 of the modules 11 and 12, the projecting elements and recesses having for example a circular or polygonal profile. For example, the first elements 25 have slightly convex surfaces to obtain a forced interlocking with the second elements 26; preferably, the second elements 26 have slightly convex surfaces, to increase the interference between the first 25 and the second 26 elements .

In a second embodiment of the modules 11, 12 for the chassis 10 for motor vehicles of the invention shown in Figure 5.2, the first 25 and the second 26 interlocking elements are made with projecting elements and corresponding recesses made respectively on the first surface 15 and on the second surface 16 of the modules 11 and 12, the projecting elements and recesses having a saw-teeth profile.

In a third embodiment of the modules 11, 12 for the chassis 10 for motor vehicles of the invention shown in Figure 5.3, the first 25 and the second 26 interlocking elements are made with projecting elements and corresponding recesses made respectively on the first surface 15 and on the second surface 16 of the modules 11 and 12, the projecting elements being composed of a projecting edge and the corresponding recesses being composed of a central recessed part.

In a fourth embodiment of the modules 11, 12 for the chassis 10 for motor vehicles of the invention shown in Figure 5.4, the first 25 and the second 26 interlocking elements are made with projecting elements and corresponding recesses made respectively on the first surface 15 and on the second surface 16 of the modules 11 and 12, the projecting elements and recesses having for example a honeycomb profile, for example hexagonal.

Obviously, other embodiments are possible with interlocking elements 25, 26 of a known type, for example known elements composed of surface peduncles made on the surface of the modules 11, 12 and designed to be mutuallly interconnected.

Preferably, the modules 11, 12 of the chassis 10 for motor vehicles are made by using a combination of pairs of first 25 and second 26 interlocking elements of a different type.

In a preferred way, the first 25 and the second 26 interlocking elements are made on a lateral longitudinal surface of the module 11, 12 for the chassis 10 for motor vehicles.

Another way of interlocking could be also possible, where a module has its two sides different one from the other, in order to interlock in a way in the first side (for example, with the element adjacent to the left or bottom) and in a different way in the second side (for example, with the other element adjacent to the right or top) .

In order to obtain a final structure of the chassis 10, which is monolithic and extremely rigid

(at torsional and flexural levels) , it is finally necessary to glue the first 25 and the second 26 interlocking elements and/or the first surface 15 and on the second surface 16 of the modules 11 and 12, through spreading with gluing substances of a known type, arranged on the surfaces to be joined immediately before assembling the modules 11 and 12.

Preferably, the gluing substance between the modules 11 and 12 is consolidated/reticulated through a heating operation of the structure with a suitable heating system of a known type.

The modules 11, 12 are designed to be assembled in an assembling tank 40, which will be explained below more in detail, and are made through 3D moulding, preferably through a battery of 3D printers, each one of which can work, if necessary, with a different material with respect to another one; for example, the modules 11, 12 are made of powder or filaments of nylon, CF, titanium, fiberglass, Kevlar, polyurethane, ABS reinforced with CF (chopped carbon) , Scalmalloy, and in general materials of a known type for 3D printing.

For example, for a motor vehicle having average sizes (length of 4.2-4.6 m; width of 1.7- 1.9 m; height of 1.5-1.7 m) and an average displacement (1.6 - 2.2 litres), chassis 10 composed of 40-80 modules 11, 12 can be assumed.

Since the majority of motor vehicles has a longitudinal plane of symmetry (as regards the structure of the vehicle chassis), it can be devised that the number of modules 11, 12 really and suitably different (in terms of composing materials and morphology) will be reduced to about half with respect to the above mentioned number.

The production plant of the chassis 10 for motor vehicles of the invention comprises, in a preferred way:

- at least one 3D printer for printing the modules 11, 12 of the chassis for motor vehicles; the tank 40 for assembling/containing the modules 11, 12 to be fastened, having an internal surface 46 designed to be coupled with the surface of the modules 11, 12 when they are fastened, mutually interlocked to make the chassis 10; the tank 40 will be a sort of cradle/seat inside which the chassis 10 is assembled, preferably automatically. The tank can in turn be preferably made of plastic material through 3D-moulded modules 41, 42 which are then assembled, with their division completely different from that of the chassis 10.

In a preferred way, "n" tanks 40 are provided for every type of chassis 10 to be mass-produced, depending on the parallelization of production flows, and therefore depending on the production volumes which have to be supported for such specific chassis.

The tank comprises (always made through 3D printing) fastening systems 45 to guarantee that at least the first module 11, 12 arranged on every side of the tank 40 (and therefore of the chassis 10 when manufacturing) can be fastened to the tank 40. For other modules 11, 12 of the chassis 10, fasteners to the tank 40 will presumably not be necessary, since the interlocking with the nearby modules 11, 12 already inserted (and fastened to the tank 40) will guarantee that each module 11, 12 is kept in the correct position. The fasteners 45 will then anyway allow, at the end of the assembling step, the disengagement of the finished chassis 10 from the preparation tank 40 (optionally the chassis 10 will in turn have hooks embedded for example in its four angles at the ends, to be able to be slung by a catching and lifting system made for such purpose; preferably, the tank 40 comprises a belting and blocking system of the modules 41, 42 composing the tank 40, to prevent them from going away during the chassis pressing step, described below more in detail.

At least one first automatic sub-station is also provided, comprising preparing/dosing and distributing means of a gluing substance, for distributing a pre-dosed amount of the gluing substance on the interlocking elements 25, 26 and/or on the surfaces 15, 16 of the modules 11, 12 to be fastened; preferably, the automatic substation comprises a pre-heating system for the gluing substance, for example through UV rays.

An automatic system is further provided, comprising pressing means, designed to keep pressed the surfaces 15, 16 of the modules 11, 12 to be fastened.

The following items are further provided:

a second sub-station comprising heating means of a known type, for heating/reticulating the gluing substance;

handling means of the modules 11, 12, for example a robot equipped with holding clamp; handling means of the assembling tank 40, for example known systems of the AGV type;

handling means of the chassis, for example a tackle/manipulator .

The process for producing the chassis 10 for motor vehicles of the invention preferably comprises the following steps:

a first step of 3D molding the modules 11, 12 of the chassis for motor vehicles, through at least one 3D printer, preferably with a battery of 3D printers;

a second step of cleaning and surface finishing the modules 11, 12, to remove burrs and residues from the molded pieces;

a third optional step of positioning, through an automated system, the modules 11, 12 of the chassis in corresponding storage trays, so that the modules 11, 12 are suitably oriented for a following step of catching the modules 11, 12 through handling means;

a fourth step of withdrawing, preferably from the storage tray of the modules 11, 12 and of transferring the modules 11, 12 by the preparing/dosing and distributing sub-station of the gluing substance, through handling means of the modules 11, 12, for example robots equipped with holding clamp;

a fifth step of distributing the pre-dosed amount of the gluing substance on the interlocking elements 25, 26 and/or on the surfaces 15, 16 of the modules 11, 12 to be fastened, through preparing/dosing and . distributing means of the gluing substance;

a sixth step of recognizing and of transferring the modules 11, 12 in the respective position inside the assembling tank 40, through recognizing means and handling means of the modules 11, 12, for example robots;

a seventh step of fastening some modules 11,

12 to the assembling tank 40, by means of a simplified fastening system integrated in the tank 40;

an eighth step of pressing/consolidating the modules 11, 12 to be fastened, through the automatic system comprising pressing means designed to keep pressed the surfaces 15, 16 of the modules 11, 12 to be fastened, so that the respective interlocking elements 25, 26 and/or surfaces 15, 16 mutually adhere, for example for a time of about 10 s and with an adequate pressure, by stably gluing themselves ;

a ninth optional step of handling the assembling tank 40 with the complete chassis for vehicles with every sub-part thereof towards the heating/reticulating station of the gluing substance, through the handling means of the assembling tank 40, for example through known systems of the AGV type;

a tenth optional step of heating the chassis for motor vehicles, for example for a time from 10' to 30' and at a temperature included between 70° and 130°C;

an eleventh step of fastening the fastening points of the four angular modules of the chassis for motor vehicles through handling means of the chassis, for example a hoist/manipulator, in order to detach the chassis for motor vehicles from the assembling tank 40;

a twelfth step of positioning of the chassis on a trolley/tray, through the handling means of the chassis, for example a hoist/manipulator ; a thirteenth step of re-positioning the assembling tank 40, through handling means of the tank 40, for example through known systems of the AGV type.

Advantageously, the process for producing the chassis 10 for motor vehicles of the invention allows having a WIP (Work In Progress) of this working reduced to a minimum, and allows having a JIT (Just In Time) production of what is necessary, when it is necessary, in a straightforward and integrated way.

Due to the adoption of 3D printing technologies (together with a robotization of the other operations) , a very high flexibility level can be obtained for the production lines of motor vehicles chassis, so that a really customized vehicle can be produced at competitive costs, even produced at will for the needs of a specific end customer, thing which nowwdays is made possible only for prototypes or very costly vehicles.

The present invention, as described above, can also provide for some improvements/integrations.

As regards the product: instead of simple interlocking, it can be possible to devise actual joints as

interconnecting items between the chassis elements: for example, through "key/lock" arrangements, where the element with a male end is interlocked with the element with female end through a traslation-rotation of the robot axle when assembling the two elements (or by manual operation) . Another variation can be composed of a sort of tapered joint (always with female on one side and male on another) , with a slight geometric interference of the elements, which can be obtained for example by drawing the tapered male element with a series (minimum one) of flexible tongues (always obtained with a 3D printing in order to be integral with the vertex end of the cone itself) so that their elasticity can be won by a pressure suitably exerted axially by the robot during the assembling stroke of the elements themselves (or by manual operation) : when the axial pressure of the robots stops, after a small rotation, the tongues will have been elastically engaged in the suitable recesses (obtained in the

production step in the end of the female element) , generating a very strong locking of the interconnection. It is clear that this solution can be made feasible only through the use of elastic enough materials (metallic or thermoplastic or composite materials) such as to allow making flexible tongues as described above (obviously, to be able to build what is

described with a 3D printing, the material of the tongues must be the same as that of the cone carrying the tongues) .

2. This type of interconnection systems, together with the use of adhesives, can be, for particular areas of the chassis (particularly stressed during use and characterized by restricted sections, for example the pillars of the roof) , a factor conferring a higher resistance to the normal interlocking already previously mentioned.

As regards the process: 1. the production speed can be increased up to four times by using up to four robots which work simultaneously on the four sides of the tank: by so doing (obviously in addition to increasing the number of 3D printers, the distributing units of the adhesives and the possible final ovens) . It is also possible to make a tank in reverse with respect to what has been described previously: namely, starting to assemble first on the bottom of the tank the upper part of the chassis, then the whole lateral/perimeter structure, and finally the lower part, namely the vehicle floor. Clearly, this tank would be equal in length and width to the other one, but much deeper. At the end of the assembling, the chassis will obviously have to be overturned. The advantage consists in that there would be more contrast in positioning the upper elements, obviously less for the lower elements: depending on the vehicle, one solution or the other could be convenient. Possibility of conferring to the tank supplementary degrees of freedom (vertical / lateral movement and rotations on the three axes) in order to optimize the work efficiency of the robots (or the manual operations) , reducing to a minimum the risk of mutual interference . Possibility of inserting thin sensors (with integrated batteries) to monitor micro-movements of the glued elements (this could be a 4D printing: namely 3D + an dynamic function, that ©# continuously checks over time the solidity and the stability of the structure ) . The sensors could be glued at the end of the assembling in the points of the chassis presumably more stressed astride contiguous elements to evaluate their relative micromovements. These sensors (if equipped with alarm) can interact with the driver (or the autonomous drive) to limit the vehicle (speed/max, maximum weight, linear and centrifugal acceleration, etc.) in order to contain it within the structural safety limits. An assembling process can also be devised which uses two tanks in parallel (and therefore simultaneously producing) : one for the upper chassis and one for the lower chassis, with an additional final assembling operation of the two macro-portions of chassis which would be joined with the external support of the lower tank only, after having discharged the upper chassis from its tank. This can allow optimizing the contrast reaction when assembling both portions of chassis and therefore a structurally optimum result, above all in case or particularly complex chassis (e.g.: it could be the case of SUV vehicles chassis) . Another variation could be the use of welding instead of gluing, obviously only for those chassis materials which allow such welding operation .