Method for manufacturing a bicycle frame and bicycle frame

Abstract

A bicycle frame (10) is described comprising at least one seat tube (12), configured to support a seat post, and at least one down tube (14), which is integrally formed in one piece with the seat tube (12) at a lower end (16) of the down tube (14) and is integrally formed in one piece with a head tube (20) at an upper end (18) of the down tube (14). The frame (10) is manufactured with a carbon fibre reinforced polymer composite material. At least one casing (22) is obtained in the frame (10) at the connecting portion between the seat tube (12) and the down tube (14), and directly in the material the frame (10) is manufactured with, the at least one casing (22) comprising at least one first cavity (24) for housing at least one corresponding electric motor (100, 102), at least one second cavity (26) for housing at least one a torque sensor (104) and at least one corresponding crankset (106) and at least one third cavity (28) for housing at least one corresponding motion transmission mechanism (108) between the electric motor (100, 102) and the crankset (106). A method for manufacturing the above-mentioned frame (10) is also described.

Description

[0001] METHOD FOR MANUFACTURING A BICYCLE FRAME AND BICYCLE FRAME

[0002] The present invention generally relates to a bicycle frame and, in particular, a frame for a so-called pedal assist bicycle or e-bike. The present invention also relates to a method for manufacturing a frame for a pedal assist bicycle or e-bike. It

[0003] 5 is specified that, as used herein, a pedal assist bicycle refers to any vehicle with one (unicycle), two, three (tricycle) or more (quadricycle, rickshaw, etc.) wheels which is both powered by human muscle power and equipped with at least one electric motor.

[0004] As is known, a pedal assist bicycle or e-bike is a conventional bicycle to which at least one electric motor, one or more batteries and a series of sensors are applied which detect, instant by instant, the data relating to the rotation speed of the crankset / pedal assembly and / or the torque detected on such crankset / pedal assembly. These data are usually coded by an electronic control unit which calibrates, on the basis of predefined parameters, the additional support provided

[0005] 15 by the electric motor to the biker's action.

[0006] The electric motor of a pedal assist bicycle is, nowadays, housed in a casing separated from the bicycle frame together with the relevant accessories (battery, electronic control unit, sensors, cables, etc.). The bicycle frame must be therefore manufactured with a particular shape to take account of the later mounting of the

[0007] 20 motor casing. In addition, the bicycle frame must be provided with suitable attachment points for the later mounting of the motor casing. A motor casing having to be designed separately from the bicycle frame affects the rigidity and structural resistance of the assembly consisting of the frame and the motor casing.

[0008] The use of carbon fibre is known for manufacturing a bicycle frame, whether it is a “muscle” type or a pedal assist bicycle. Among the carbon fibres, a composite polymer material reinforced with carbon fibre called CF-SMC (acronym for “Carbon Fiber Sheet Moulding Compound”) is also known, which consists of a thermosetting material mainly composed of unsaturated polyester resins, epoxies, inert fillers, short and broken carbon fibres, reinforcing fibres and additives.

[0009] 30 CF-SMC is processed using a press compression moulding technology. This technology is already used in the automotive sector but has never been used for complex components such as a motor casing for a pedal assist bicycle. In fact, moulding CF-SMC is very difficult for several reasons. First of all, carbon together with resin must be able to flow to every point of the mould in the correct proportion, so as to polymerize correctly in order to give rigidity to the final component. This is particularly difficult when the shapes of the component are complex, or when components of variable thickness must be manufactured, as is the case with the motor casing for a pedal assist bicycle.

[0010] The particularity of CF-SMC is that it is isotropic, which means that its mechanical characteristics do not depend on a particular direction. This occurs thanks to its production process. The broken short-fibre carbon, impregnated with resin, is placed inside a mould mounted on a hot plate press. Carbon and resin do not have a preferential direction in placing themselves and this makes the finished product isotropic. The mechanical characteristics of the finished product are therefore similar to the characteristics of aluminium.

[0011] Carbon bicycle frames are currently manufactured using the autoclave technique, whose characteristics are a limit in the creation of complex shapes, such as the shapes required for manufacturing a motor casing for a pedal assist bicycle. Furthermore, carbon processed in an autoclave is anisotropic. The sheets are in fact arranged in layers, intertwining the fibres in such a way as to provide greater structural rigidity in the points of interest. Laminated carbon is therefore not workable like CF-SMC.

[0012] Prior art document WO 2022 / 153014 A1 discloses a frame for a bicycle, in particular an e-bike, which is manufactured in a traditional way by injection of thermoplastic or thermosetting materials. The frame is equipped with a compartment for the motor and a compartment for the battery.

[0013] Prior art document GB 5230155 A discloses a foldable modular bicycle which uses an electric motor inserted in a central module. The moving parts of the motor are housed in the central module, which acts as an interface with a front module and a rear module that form the frame of the bicycle. The central module must be therefore attached to the other parts of the frame, namely the front module and the rear module, and also provides a structural element for such frame. In prior document GB 5230155 A there is no reference to the type of material used for manufacturing the bicycle, nor to the method for manufacturing such bicycle.

[0014] Neither prior art document WO 2022 / 153014 A1 nor prior art document GB 5230155 A disclose a motor whose housing is obtained directly inside the frame during the manufacturing step of the same frame. In prior art document GB 5230155 A the housing for the motor is a modular component that must be then connected to the remaining parts which form the bicycle frame. In prior art document WO 2022 / 153014 A1 an e-bike of the known type is disclosed, which is manufactured by using a thermosetting or thermoplastic material injection method.

[0015] At the current state of the art, therefore, no frames for bicycles (whether of the muscle type or e-bike) are manufactured in CF-SMC. Therefore, according to the current state of the art, it is not possible to manufacture a product similar to a bicycle frame as the construction methods are incompatible. Furthermore, to date, there is not even an e-bike motor casing which is manufactured in CF-SMC. The current methods for manufacturing carbon bicycle frames, which are carried out using an autoclave, do not provide the geometries necessary to create a functioning motor compartment. For example, the housings for the bearings and the crown of a planetary reduction gear shall not be produced by using a traditional lamination technique.

[0016] The object of the present invention is therefore to provide a bicycle frame and a method for manufacturing the same which are capable of solving the aforementioned drawbacks of the prior art in an extremely simple, economical and particularly functional way.

[0017] In detail, it is an object of the present invention to provide a bicycle frame and a method for manufacturing the same which allow for the production of electric bicycles with fully integrated motors. This eliminates the need to create customised frames for a particular type of motor, the motor casing and the frame being made from a single shell.

[0018] Another object of the present invention is to provide a bicycle frame and a method for manufacturing the same which enable to give the frame a significant rigidity and structural resistance, overcoming all the problems that can be encountered during assembly and use of the frame and motor. This is due to the fact that it will be no longer necessary to arrange the attachment points for the motor casing on the frame. There are therefore benefits in terms of aesthetic, in terms of the structure and also in terms of the management of the components.

[0019] A further object of the present invention is to provide a bicycle frame and a method for manufacturing the same which enable the frame to take on any shape, which are impossible to obtain with the traditional carbon lamination technology. Geometries which are typical of aluminium machined from solid shall be obtained by using CF-SMC, thus creating a single frame and motor casing structure with unique mechanical and geometric properties. The integrated frame will therefore enable all the components of an e-bike motor (electric motor, electronic control unit, reduction unit, pedal axle and sensors) to be housed therein.

[0020] These objects according to the invention will be achieved by providing a bicycle frame and a method for manufacturing the same as set forth in the independent claims.

[0021] Further features of the invention are highlighted by the dependent claims, which are an integral part of the present description.

[0022] According to the invention, the motor casing is directly incorporated into the bicycle frame. A particular production method is used to manufacture this frame, namely the forging of CF-SMC (“Carbon Fiber Sheet Moulding Compound”). The bicycle frame turns out to be a single assembly comprising the main casing of the electric motor, which not only houses the same electric motor, but also all the components required for operating such motor. The frame is then forged together with the motor casing, obtaining a single assembly.

[0023] In the production process for manufacturing the frame with integrated motor casing, a hot plate press is used on which the half-shells of the mould are positioned. The material is placed inside the mould and then pressed. The correct combination of pressure and temperature of the half-shells of the mould enables the carbon fibre and the resin with which the fibre is impregnated to flow to every point of the mould, creating the desired shape of the frame. The result will be therefore a frame that integrates the motor casing and a compartment for the battery, as well as all the passages for the cables. The motor is then closed inside the casing using covering elements conforming to the frame.

[0024] In the production process for manufacturing the frame with integrated motor casing, this frame is not manufactured using a thermosetting or thermoplastic materials injection method, but rather by forging CF-SMC. A motor is thereby created with a full carbon housing (including central casing and side casings), while the e-bike motors according to the prior art usually have a housing made of aluminium or at most of magnesium. The features and advantages of a bicycle frame and a method for manufacturing the same according to the present invention will be clearer from the following exemplifying and hence non-limiting description, referring to the attached schematic drawings in which:

[0025] Figure 1 is perspective view of a preferred exemplary embodiment of a bicycle frame according to the present invention;

[0026] Figure 2 a side elevation view, from the right side, of the frame of Figure 1 ;

[0027] Figure 3 is another side elevation view, from the left side, of the frame of Figure 1 ;

[0028] Figure 4 is another perspective view of the frame of Figure 1 , also showing the components of an electric motor; and

[0029] Figure 5 shows a preferred exemplary embodiment of a mould to be used in the method for manufacturing a bicycle frame according to the present invention.

[0030] With reference in particular to figuresl to 4, a preferred embodiment of a bicycle frame according to the present invention is shown. The frame is indicated as a whole with reference number 10. The frame 10 is specifically designed for a so- called pedal assist bicycle or e-bike and has the characteristic of integrating the motor housing therein.

[0031] The difference compared to the current e-bike frames is that the latter are preformed for receiving a certain type of motor which is already available on the market, using attachments which usually consist of screws. The motors are then attached to the frame by means of their main housing. Conversely, the frame 10 according to the present invention has no motor attachments, as the motor central casing is already made together with the frame 10.

[0032] In detail, the frame 10 comprises at least one seat tube 12, configured to support a seat post, and at least one down tube 14, which is integrally formed in a single piece with the seat tube 12 at a lower end 16 of the down tube 14. The down tube 14 is also integrally formed in a single piece with a head tube 20 at an upper end 18 of the down tube 14. The frame 10 is made of a carbon fibre reinforced polymer composite material.

[0033] At least one casing 22 is obtained in the frame 10 at the connecting portion between the seat tube 12 and the down tube 14, and directly in the material the frame 10 is manufactured with, the at least one casing 22 comprises: - at least one first cavity 24 for housing at least one corresponding electric motor;

[0034] - at least one second cavity 26 for housing at least one a torque sensor and at least one corresponding crankset; and

[0035] - at least one third cavity 28 for housing at least one corresponding motion transmission mechanism between the electric motor and the crankset.

[0036] In the exemplary embodiment of the frame 10 shown in the figures, the first cavity 24, the second cavity 26 and the third cavity 28 are separated from each other. However, it is conceivable that in other exemplary embodiments of the frame these cavities may be brought together in a single housing, provided that this housing is able to contain all the main components of an electric motor for e-bikes, including or not an electronic control unit.

[0037] By way of example, as shown in Figure 4, the electric motor may comprise in a per se known manner, a stator 100 and a rotor 102, both housed in the first cavity 24 of the casing 22 integrated into the frame 10. The torque sensor may consist, for example, of a torque meter 104, housed in the second cavity 26 of the casing 22 integrated into the frame 10. Again in a per se known manner, the crankset 106 can be integral with one or more crowns 1 10 for connection, by means of a chain, to one or more sprockets (not shown). For example, the crankset 106 can be connected to a drive mechanism by means of ratchets, while the drive mechanism can in turn be integral with the external crown 1 10. Again by way of example, the motion transmission mechanism 108 can comprise a planetary reduction gear. Again by way of example, an electronically operated gearbox can also be inserted in at least one of the first cavity 24, the second cavity 26 and the third cavity 28 of the casing 22 integrated into the frame 10, whereby the drive electronics of this gearbox can also be inserted in at least one of the aforementioned first cavity 24, second cavity 26 and third cavity 28 of the casing 22 integrated into the frame 10.

[0038] Preferably, the material from which the frame 10 is manufactured is a Carbon Fiber Sheet Moulding Compound or CF-SMC. The compounds used can be different, with different mechanical characteristics: this also results in slightly different weights. In any case, the frame 10 manufacturing technology remains the same: the frame 10 is in fact manufactured by using a hot plate press moulding technology.

[0039] Again preferably, according to the exemplary embodiment shown in the Figures, the frame 10 comprises at least one top tube 30, which is integrally formed in a single piece with the seat tube 12 and with the down tube 14 and connects this down tube 14 with the head tube 20. However, it is conceivable that the frame 10 can have different shapes depending on the intended use.

[0040] The frame 10 may also comprise two or more covering elements 32, 34, which enclose the casing 22 on both sides of the frame 10 and are manufactured from the same material the frame 10 is manufactured from. The covering elements 32, 34, contain the motor, the sensors and the transmission mechanism, only leaving the opposite ends of the crankset coming out of the casing 22. At least one housing 36 may be obtained inside the down tube 14 for housing at least one corresponding battery (not shown) for the electrical power supply of the electric motor and the relevant accessory components.

[0041] The method for manufacturing the frame 10 described so far first of all comprises a first step which consists in drawing the frame 10 by using a CAD (“Computer-Aided Design”) system. The frame 10 is drawn by using the CAD system in order to contain at least one seat tube 12, configured to support a seat post, at least one down tube 14 and at least a head tube 20. The down tube 14 is integrally formed in a single piece with both the seat tube 12, at a lower end 16 of the down tube 14 and the head tube 20, at an upper end 18 of the down tube 14.

[0042] Moreover, the frame 10 is drawn by using the CAD system in such a way that at least one casing 22, which is sized to house at least one specific electric motor 100, 102, at least one specific torque sensor 104, at least one specific crankset 106 and at least one specific motion transmission mechanism 108, is obtained therein, and in such a way that the frame 10 has no undercut portions. Consequently, the frame 10 already comprises therein the casing 22 which has the space necessary to house the electric motor, the motion transmission mechanism and the sensors.

[0043] The electric motor being attached to the frame 10 gives the designer much freedom of creating the shapes he or she prefers. This involves an advantage in both structural terms, in case particular solutions need to be adopted, and aesthetically. There is no particular type of frame to use. It is possible, in fact, to range from frames for city bikes, enduro, XC, trail, downhill, etc. Any type of bicycle, or other similar vehicle, that can have an electric motor can be manufactured using the frame 10 according to the invention. They can be “front” or “full” type bicycles, hence with only the front shock absorber, or both front and rear shock absorber, respectively.

[0044] Once the type of frame has been chosen, next step is drawing the frame, integrating the most suitable electric motor. In the exemplary embodiment shown in the figures, starting from a specific electric motor for e-bikes, the desired geometries are used in such a way that the same components as those used to assemble the “single” motor can also be used again for the motor integrated into the frame 10. As mentioned above, as the frame 10 is not bound to have the attachments for an external motor casing, the geometries can be varied according to the design needs. Starting from the motor, the triangle of the frame 10 is then developed. In the oblique tube 14, also known as “down-tube”, the housing 36 is then obtained for one or more batteries, which housing must be of the correct size to contain the battery or batteries most suitable for the type of electric motor chosen.

[0045] Once the desired geometry of the frame 10 has been created, next step is making a mould. This mould, which is shown by way of example in Figure 5, consists of a first male half-mould M and a second female half-mould F, in such a way that the first male half-mould M and the second female half-mould F can be coupled with a press and have the shape of the frame 10 which has been previously drawn by using the CAD system. Preferably, the first male half-mould M is designed to be fixed on the upper part of the press, whereas the second female half-mould F is designed to be fixed on the lower part of the press. The mould can be made of aluminium, which however allows the production of a not particularly high number of frame components 10. Conversely, if a high number of components is intended to be made, the use a steel mould is advisable for its being less subject to wear compared to the aluminium mould. This mould can be made in a single piece, or using dowels for the more complex parts. This also allows these dowels to be replaced, if worn, or if there is a need to change a particular shape, such as a cavity.

[0046] Some factors should be taken into account when making the mould. A first factor is the direction of removal. If a simple mould is intended to be made, it is important that it only has one direction of removal. The direction of removal is the direction along which the mould opens. As the press opens by moving vertically, the frame 10 must be designed in such a way that it does not get stuck in one of the half-moulds and the mould can open without problems and without breaking the frame 10. Therefore, the frame 10 must not have any undercut portions. If these undercut portions were to be present, the mould would become considerably more complicated.

[0047] It is also important that for the mould to have an appropriate draft angle. This draft angle can vary between 1 and 3 degrees depending on the position. The draft angle refers to the inclination that each surface of the first male half-mould M and the second female half-mould F must have with respect to the press planes. The draft angle is used to remove the frame 10 from the mould. If the surfaces of the first male half-mould M and the second female half-mould F were perfectly perpendicular to the press planes, there would be the risk that the frame 10 could not be removed from the mould.

[0048] In the event that the design of the frame 10 includes one or more particularly complex surfaces and / or portions present on such frame 10, exceeding material must be left in the mould. In this way, particularly complex surfaces and / or portions of the frame 10 can be made at a later stage, for example through subsequent removal of material and / or machine tool processing. In fact, unlike any piece made of carbon by lamination, the CF-SMC can be machined on machine tools. It is therefore advisable to create a "rough" piece that is simplified compared to the final geometry of the frame 10, which will then be obtained through removal of material in one or more subsequent operations. In the exemplary embodiment shown in the Figures, for example, the holes for mounting the covering elements 32, 34 that close the casing 22 and the more complex geometries of the frame 10 are made according to this concept.

[0049] The thicknesses of the frame 10 must also be taken into account. In order for the material to be distributed evenly inside the mould, it is important that the thicknesses of the frame 10 to be made are uniform, too. There must therefore be a correlation between feasibility, mechanical resistance and weight. In the event that the structural rigidity of the frame 10 has to be increased, if so desired, conventional layers of woven carbon fibre to alternate with the short carbon fibres of the CF-SMC can also be used. Again in order to increase the structural rigidity of the frame, it is also possible to interpose layers of Kevlar or other suitable materials.

[0050] When the mould is prepared, a carbon fibre reinforced polymer composite material (CF-SMC) with which to manufacture the frame 10 is prepared. The carbon fibre reinforced polymeric composite material is then cut in such a way that such material has the desired shape of the frame 10 previously drawn by using the CAD system. In particular, the casing 22 is obtained directly in the material the frame 10 is manufactured with, so that the casing 22 comprises at least one first cavity 24 for housing at least one corresponding electric motor 100, 102, at least one second cavity 26 for housing at least one torque sensor 104 and at least one corresponding crankset 106 and at least one third cavity 28 for housing at least one corresponding motion transmission mechanism 108 between the electric motor 100, 102 and the crankset 106.

[0051] Preferably, during the CAD drawing step the frame 10 can be drawn to comprise at least one top tube 30, which is integrally formed in a single piece with the seat tube 12 and the down tube 14 and connects the down tube 14 with the head tube 20. The carbon fibre reinforced polymer composite material is then cut in such a way that this material has the shape of the frame 10 which also comprises the top tube 30.

[0052] Again preferably, during the CAD drawing step it is also possible to draw two or more covering elements 32, 34, which close the casing 22 on both sides of the frame 10 and are manufactured with the same carbon fibre reinforced polymer composite material. The carbon fibre reinforced polymer composite material is then cut in such a way that this material has the shape of these two or more covering elements 32, 34.

[0053] Again preferably, during the CAD drawing step the frame 10 can be drawn to also comprise at least one housing 36, obtained inside the down tube 14 for housing at least one corresponding battery for the electrical power supply of the electric motor 100, 102. In this case, too, the carbon fibre reinforced polymer composite material is then cut in such a way that this material has the shape of the frame 10 which also comprises the housing 36.

[0054] At this stage, the cut material is placed in the second female half-mould F in such a way that the mould is completely filled with the material. It is important that the moulding volume is completely filled with the material. The total volume of the frame 10, as well as the density and weight values of the material used for manufacturing the frame 10 must be checked by means of the CAD system. Since part of the material is expelled from the mould, the above-mentioned values should be increased by about 20%.

[0055] When the material is placed inside the mould, the mould can be closed. It is important that the first male half-mould M and the second female half-mould F match and have the same temperature. At this stage it is possible to carry out the moulding operation for moulding the frame 10, based on predefined values of moulding temperature, moulding pressure and pressing time. The success of the moulding depends on temperature, pressure and pressing time. Pressure and temperature can be easily found in the material data sheet, whereas the pressing time must be obtained by carrying out empirical tests. Once the correct pressing time has been identified, it can be replicated for each subsequent moulding of the same frame 10, as long as it is carried out under the same operating conditions.

[0056] It is up to the designer to decide whether or not to include a method for removing the frame 10 in the mould. A removal method is defined as the creation of a movable part in the mould, such as a dowel, which allows the frame 10 to be pushed out if it gets stuck in the mould. The dowel can be moved by the operator. The presence of this movable part is not essential, but it certainly facilitates the production process if necessary. For example, if this movable part is not provided, it is possible that the frame 10, even if it has the correct draft angles, remains inside the mould.

[0057] It is advisable that the frame 10 extracted from the press, still in its raw state, is then subjected to subsequent processing, for example to obtain the various cavities 24, 26, 28 with the correct tolerances, such as the cavities for housing the various bearings or the components of the planetary reduction gear, which has a complex shape. Furthermore, the holes are made for attaching the covering elements 32, 34 to the casing 22. In these post-moulding processes, other seats can then be obtained, such as the seats for the passage of cables.

[0058] Using a Carbon Fiber Sheet Moulding Compound or CF-SMC, which contains short broken fibre carbon, in the method for manufacturing the frame 10 enables to obtain an object whose characteristics are those of an isotropic material. In fact, the fibres are arranged randomly in the frame 10 and give the frame a structural rigidity as if it were an aluminium component. This characteristic makes it possible to manufacture complex pieces that can be subjected to multidirectional stresses.

[0059] The analyses of the frame 10 according to the invention with the finite element method (FEM) has highlighted the advantages of a motor casing 22 integrated into the frame 10 rather than a casing separated and constrained to the frame with screw connections. Subjecting both of these technical solutions to a static load of 200 kg in total has revealed that the main stress areas remain the same, but the stresses acting on the motor casing 22 integrated into the frame 10 are much lower than the stresses acting on a separate casing. Integrating the motor casing 22 into the frame 10 is advantageous not only for the frame attachment points but also for the stress which has proved to be very well distributed on the side covering elements 32, 34 (screwed to the frame 10). These side covering elements 32, 34 are subjected to stresses concentrated in the central part thereof, which however are lower than the stresses on corresponding covering elements of a casing separated from the frame.

[0060] The fact that there are lower tensions on the frame 10 also means that the deformations are lower. In the specific case, where the motion transmission mechanism 108 has a cascade reduction of gears that rests on one of the side covering elements 34, the fact of having a lower deformation is a benefit. In fact, by making the gear wheels work in line with each other, it is possible to maximize the power transmission, thus increasing the efficiency of the entire motion transmission mechanism 108, and also to protect the gear wheels against premature wear that could result from incorrect conditions of use. It should be emphasized that both side covering elements 32, 34 as well as the frame 10 and the motor casing 22 integrated into it are made of CF-SMC.

[0061] It has thus been seen that the bicycle frame and the method for manufacturing the same according to the present invention achieves the objects highlighted above. The main advantage in terms of construction is that there is no need to provide the frame with attachments for receiving the motor casing, being it possible to maximize the motor casing integration into the frame.

[0062] Furthermore, having the motor casing and frame combined in a single body allows for maximum optimization of every space. To date, all the control components of the electric motor are located around the same motor. Being able to forge a frame that comprises the motor casing therein also allows for the control components to be housed far from the electric motor, to avoid overheating and bulk problems.

[0063] Another advantage is in terms of costs. It takes approximately 9 hours to manufacture a frame in an autoclave (lamination and time in the autoclave included). Furthermore, it is necessary to have a specialized operator. Conversely, a frame in CF-SMC can be manufactured in a very short time, namely approximately 20 minutes. Furthermore, the operator does not need to have particular skills, as it is only necessary to place the material in the mould and start the moulding cycle. Another advantage is in terms of weight. A frame in CF-SMC can weigh on average 2.5 kg, including the integrated motor casing.

[0064] The bicycle frame thus conceived is however susceptible of numerous modifications and variations, all of which falling within the scope of the same inventive concept; furthermore, all the details can be replaced by technically equivalent elements. In practice, the materials used, as well as the shapes and dimensions, may be any according to the technical requirements.

[0065] The scope of protection of the invention is therefore defined by the attached claims.

Claims

CLAIMS1. A method for manufacturing a bicycle frame (10), wherein the frame (10) comprises at least one seat tube (12), configured to support a seat post, at least one down tube (14) and at least one head tube (20), and wherein the down tube (14) is integrally formed in a single piece with both the seat tube (12), at a lower end (16) of said down tube (14), and with the head tube (20), at an upper end (18) of said down tube (14), the method comprising the following steps:- drawing the frame (10) by using a CAD system, in such a way that at least one casing (22), which is sized to house at least one specific electric motor (100, 102), at least one specific torque sensor (104), at least one specific crankset (106) and at least one specific motion transmission mechanism (108), is obtained within said frame (10), and in such a way that said frame (10) has no undercut portions;- making a mould consisting of a first male half-mould (M) and a second female half-mould (F), in such a way that said first male half-mould (M) and said second female half-mould (F) can be coupled to a press and have the shape of the frame (10) drawn by using the CAD system;- preparing a carbon fibre reinforced polymer composite material with which to manufacture the frame 10;- cutting the carbon fibre reinforced polymeric composite material, in such a way that said material has the shape of the frame (10) drawn by using the CAD system, in such a way that said at least one casing (22) is obtained directly in the material the frame (10) is manufactured with, and in such a way that at least said one casing (22) comprises:- at least one first cavity (24) for housing at least one corresponding electric motor (100, 102),- at least one second cavity (26) for housing at least one torque sensor (104) and at least one corresponding crankset (106),- at least one third cavity (28) for housing at least one corresponding motion transmission mechanism (108) between said electric motor (100, 102) and said crankset (106);- placing said cut material in said second female half-mould (F), in such a way that the mould is completely filled with said material;- checking by means of the CAD system the total volume of the frame (10), as well as the density and weight values of the material used for manufacturing said frame (10), in order to have the mould completely filled with said material, taking into consideration that said values should be increased by about 20% since part of the material is expelled from the mould;- carrying out the moulding operation for moulding the frame (10), based on predefined values of moulding temperature, moulding pressure and pressing time.

2. The method according to claim 1 , wherein, in the event that the design of the frame (10) includes one or more particularly complex surfaces and / or portions present on said frame (10), the exceeding material must be left in the mould, so that said particularly complex surfaces and / or portions of the frame (10) can be made at a later stage through subsequent removal of material and / or machine tool processing.

3. The method according to claim 1 or 2, wherein, in the event that the structural rigidity of the frame (10) has to be increased, if so desired, conventional layers of woven carbon fibre to alternate with the short carbon fibres of the carbon fibre reinforced polymer composite material are used.

4. The method according to any claims 1 to 3, wherein said material is a Carbon Fiber Sheet Moulding Compound or CF-SMC.

5. The method according to any claims 1 to 4, wherein said first male half-mould (M) is designed to be fixed on the upper part of the press and said second female half-mould (F) is designed to be fixed on the lower part of the press.

6. The method according to any claims 1 to 5, wherein said frame (10) is manufactured by using a hot plate moulding technology.

7. The method according to any claims 1 to 6, comprising the following steps:- drawing the frame (10) by using the CAD system, in such a way that said frame (10) also comprises at least one top tube (30), which is integrally formed in a single piece with the seat tube (12) and with the down tube (14) and connects said down tube (14) with said head tube (20); and- cutting the carbon fibre reinforced polymeric composite material, in such a way that said material has the shape of the frame (10) which also comprises said top tube (30).

8. The method according to any claims 1 to 7, comprising the following steps:- drawing by using the CAD system two or more covering elements (32, 34) which close the casing (22) on both sides of the frame (10) and are manufactured from the carbon fibre reinforced polymer composite material; and- cutting the carbon fibre reinforced polymer composite material in such a way that said material has the shape of said two or more covering elements (32, 34).

9. The method according to any claims 1 to 8, comprising the following steps:- drawing the frame (10) by using the CAD system in such a way that said frame (10) also comprises at least one housing (36), obtained inside the down tube (14) for housing at least one corresponding battery for the electrical power supply of the electric motor (100, 102); and- cutting the carbon fibre reinforced polymeric composite material, in such a way that said material has the shape of the frame (10) which also comprises said housing (36).

10. A bicycle frame (10) manufactured by implementing the method according to any claims 1 to 9, the frame (10) comprising:- at least one seat tube (12), configured to support a seat post; and- at least one down tube (14), which is integrally formed in a single piece with the seat tube (12) at a lower end (16) of said down tube (14) and is integrally formed in a single piece with a head tube (20) at an upper end (18) of said down tube (14), wherein said frame (10) is manufactured with a carbon fibre reinforced polymer composite material and wherein at least one casing (22) is obtained in said frame (10) at the connecting portion between said seat tube (12) and said down tube (14), and directly in the material said frame (10) is manufactured with, said at least one casing (22) comprising:- at least one first cavity (24) for housing at least one corresponding electric motor (100, 102);- at least one second cavity (26) for housing at least one a torque sensor (104) and at least one corresponding crankset (106); and- at least one third cavity (28) for housing at least one corresponding motion transmission mechanism (108) between said electric motor (100, 102) and said crankset (106).

11. The frame (10) according to claim 10, characterized in that it comprises at least one top tube (30), which is integrally formed in a single piece with the seat tube (12) and the down tube (14) and connects said down tube (14) with said head tube (20).

12. The frame (10) according to claim 10 to 11 , characterized in that it comprises two or more covering elements (32, 34), which close the casing (22) on both sides of the frame (10) and are manufactured with said material.

13. The frame (10) according to any claims 10 to 12, characterized in that at least one housing (36) for housing at least one corresponding battery for the electrical power supply of said electric motor (100, 102) is obtained inside said down tube

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