Method for manufacturing a bicycle frame and bicycle frame

Abstract

A bicycle frame (10) is described, comprising at least one seat tube (12) and at least one downtube (14), the seat tube (12) being configured to support a seatpost, the downtube (14) being integrally formed as a single piece with the seat tube (12) at its lower end (16), and the downtube (14) being integrally formed as a single piece with the head tube (20) at its upper end (18). The frame (10) is made of carbon fiber reinforced polymer composite material. At the connection between the seat tube (12) and the lower tube (14), at least one housing (22) is formed in the frame (10), and the at least one housing (22) is formed directly from the material used to manufacture the frame (10). The at least one housing (22) includes at least one first cavity (24) for accommodating at least one corresponding electric motor (100, 102), at least one second cavity (26) for accommodating at least one torque sensor (104) and at least one corresponding crank assembly (106), and at least one third cavity (28) for accommodating at least one corresponding motion transmission mechanism (108) located between the electric motor (100, 102) and the crank assembly (106). A method for manufacturing the frame (10) described above is also described.

Description

Technical Field

[0001] This invention generally relates to a bicycle frame, and more particularly to a frame for so-called power-assisted bicycles or electric bicycles. The invention also relates to a method of manufacturing a frame for power-assisted bicycles or electric bicycles. It should be noted that, as used herein, a power-assisted bicycle refers to any vehicle having one (single wheel), two, three (tricycle), or more (four-wheeled, rickshaw, etc.) wheels, which is both powered by human muscle and equipped with at least one electric motor. Background Technology

[0002] As is well known, electric bicycles, or e-bikes, are conventional bicycles that utilize at least one electric motor, one or more batteries, and a series of sensors that detect data in real time related to the rotational speed of the crankset / pedal assembly and / or the torque detected on that crankset / pedal assembly. This data is typically encoded by an electronic control unit (ECU), which calibrates the additional support provided by the electric motor to the rider's movements according to predefined parameters.

[0003] Currently, the electric motor of a power-assisted bicycle, along with related components (battery, electronic control unit, sensors, cables, etc.), is housed in a separate housing from the bicycle frame. Therefore, the bicycle frame must be manufactured in a specific shape to accommodate the subsequent installation of the motor housing. Furthermore, the bicycle frame must be equipped with suitable attachment points for the subsequent installation of the motor housing. The motor housing, which must be designed separately from the bicycle frame, affects the rigidity and structural strength of the assembly consisting of the frame and motor housing.

[0004] Carbon fiber is known to be used in the manufacture of bicycle frames, whether for human-powered or electric bicycles. Among carbon fibers, a carbon fiber reinforced polymer composite material called CF-SMC (an abbreviation for "Carbon Fiber Sheet Moulding Compound") is also known. CF-SMC comprises thermosetting materials, which are mainly composed of unsaturated polyester resin, epoxy resin, inert filler, chopped carbon fibers, reinforcing fibers, and additives.

[0005] CF-SMC is manufactured using compression molding technology. This technology has been used in the automotive industry, but never in complex components such as motor housings for power-assisted bicycles. In fact, molding CF-SMC is very difficult for several reasons. First, the carbon and resin must flow in the correct proportions to every point in the mold for proper polymerization, thus giving the final part rigidity. This is especially challenging when the part has a complex shape, or when parts of varying thicknesses must be manufactured, such as for motor housings in power-assisted bicycles.

[0006] The unique characteristic of CF-SMC lies in its isotropy, meaning that the mechanical properties of CF-SMC are not dependent on a specific orientation. This is thanks to the CF-SMC manufacturing process. Resin-impregnated chopped carbon fibers are placed in a mold mounted on a hot plate press. The carbon and resin have no preferred orientation when placed, making the final product is isotropic. Therefore, the mechanical properties of the final product are similar to those of aluminum.

[0007] Currently, carbon fiber bicycle frames are manufactured using autoclave technology, which has limitations in creating complex shapes, such as those required for motor housings in power bicycles. Furthermore, the carbon fibers processed in the autoclave are anisotropic. In fact, the sheets are layered with interwoven fibers to provide greater structural rigidity in critical areas. Therefore, laminated carbon is not as easily machinable as CF-SMC.

[0008] Prior art document WO 2022 / 153014 A1 discloses a frame for a bicycle, and more particularly a frame for an electric bicycle, which is manufactured by a conventional method of injecting thermoplastic or thermosetting materials. The frame is equipped with a compartment for a motor and a compartment for a battery.

[0009] Prior art document GB 5230155 A discloses a foldable modular bicycle that uses an electric motor inserted into a central module. The moving parts of the motor are housed in the central module, which serves as an interface with the front and rear modules that form the bicycle frame. Therefore, the central module must be attached to the other parts of the frame, namely the front and rear modules, and it also provides structural elements for the frame. Prior art document GB 5230155 A does not mention the type of material used to manufacture the bicycle, nor does it mention a method for manufacturing such a bicycle.

[0010] Neither prior art document WO 2022 / 153014 A1 nor prior art document GB 5230155 A discloses a motor in which its housing is formed directly within the frame during the frame manufacturing process. In prior art document GB 5230155 A, the housing for the motor is a modular component that must subsequently be attached to the rest of the bicycle frame. Prior art document WO 2022 / 153014 A1 discloses an electric bicycle of a known type manufactured using an injection molding method with thermosetting or thermoplastic materials.

[0011] Therefore, under current technological conditions, no bicycle frame (whether human-powered or electric) is manufactured using CF-SMC. Consequently, it is impossible to manufacture products resembling bicycle frames due to incompatible construction methods. Furthermore, to date, there isn't even an electric bicycle motor housing manufactured using CF-SMC. Existing methods of manufacturing carbon fiber bicycle frames using autoclaves cannot provide the geometry required to create functional motor compartments. For example, the housings for bearings and planetary reduction gear crowns cannot be produced using conventional lamination techniques. Summary of the Invention

[0012] Therefore, the object of the present invention is to provide a bicycle frame and a method for manufacturing the bicycle frame, which can solve the disadvantages of the prior art in an extremely simple, economical and particularly practical way.

[0013] In detail, the object of the present invention is to provide a bicycle frame and a method for manufacturing the bicycle frame, which allows for the production of electric bicycles with a fully integrated motor. This eliminates the need to manufacture custom frames for specific types of motors, as the motor housing and frame are made from a single shell.

[0014] Another object of the present invention is to provide a bicycle frame and a method for manufacturing the bicycle frame, which enables the frame to be endowed with significant rigidity and structural resistance, overcoming all problems that may be encountered during the assembly and use of the frame and motor. This is because there is no longer a need to arrange attachment points for the motor housing on the frame. Therefore, there are benefits in terms of aesthetics, structure, and component management.

[0015] Another object of the present invention is to provide a bicycle frame and a method for manufacturing the bicycle frame, which, along with the manufacturing method, allows the frame to take on any shape that is not possible using conventional carbon lamination techniques. By using CF-SMC, typical geometries of machined aluminum can be obtained, thereby creating a single frame and motor housing structure with unique mechanical and geometric properties. Therefore, a one-piece frame will be able to accommodate all components of an electric bicycle motor (electric motor, electronic control unit, reduction gear, pedal shaft, and sensors).

[0016] These objectives according to the invention will be achieved by providing a bicycle frame as described in the independent claims and a method for manufacturing the bicycle frame.

[0017] Further features of the invention are highlighted by the dependent claims, which are integral parts of this specification.

[0018] According to the present invention, the motor housing is directly bonded to the bicycle frame. The frame is manufactured using a specific production method: die forging of CF-SMC (“Carbon Fiber Sheet Moulding Compound”). The bicycle frame is proven to be a single component comprising the main housing of the electric motor, which not only houses the electric motor itself but also all the components necessary for operating the motor. The frame and motor housing are then die-forged together to form a single component.

[0019] In the production process of the frame for manufacturing the integrated motor housing, a hot plate press is used, on which the half-shell of the mold is positioned. Material is placed inside the mold and then pressed. The correct combination of pressure and temperature on the half-shell of the mold allows the carbon fiber and impregnated fiber resin to flow to every point in the mold, thus forming the desired shape of the frame. The result is a frame that integrally incorporates the motor housing, a compartment for the battery, and all channels for the cables. The motor is then enclosed within the housing using a cover element that conforms to the frame.

[0020] In the production process of the frame used to manufacture the integrated motor housing, the frame is not manufactured using injection molding methods with thermoset or thermoplastic materials, but rather by die forging CF-SMC. This creates a motor with an all-carbon housing (including the central and side housings), whereas existing electric bicycle motors typically have housings made of aluminum or at most magnesium. Attached Figure Description

[0021] The features and advantages of the bicycle frame according to the invention and the method for manufacturing the bicycle frame will become clear from the following exemplary and therefore non-limiting description with reference to the illustrative drawings, wherein: Figure 1 This is a perspective view of a preferred exemplary embodiment of a bicycle frame according to the present invention; Figure 2 yes Figure 1 A side elevation view of the frame as seen from the right. Figure 3 yes Figure 1 An elevation view of the frame from the left side; Figure 4 yes Figure 1 Another perspective view of the frame also shows the components of the electric motor; and Figure 5 A preferred exemplary embodiment of the mold used in the method for manufacturing a bicycle frame according to the present invention is shown. Detailed Implementation

[0022] Special reference Figures 1 to 4 The figure shows a preferred embodiment of a bicycle frame according to the invention. The frame is generally indicated by reference numeral 10. Frame 10 is specifically designed for so-called power-assisted bicycles or electric bicycles and features an integral motor housing therein.

[0023] The difference compared to current electric bicycle frames is that current electric bicycle frames use attachments that typically include screws, pre-formed to receive a certain type of motor already available on the market. The motor is then attached to the frame via its main housing. In contrast, the frame 10 according to the invention does not have a motor attachment because the central motor housing is already manufactured together with the frame 10.

[0024] In detail, the frame 10 includes at least one seat tube 12 and at least one lower tube 14, the seat tube 12 being configured to support a seat post, and the lower tube 14 being integrally formed as a single piece with the seat tube 12 at its lower end 16. The lower tube 14 is also integrally formed as a single piece with the head tube 20 at its upper end 18. The frame 10 is made of carbon fiber reinforced polymer composite material.

[0025] At the connection between the seat tube 12 and the lower tube 14, at least one housing 22 is formed in the frame 10, and the at least one housing 22 is formed directly from the material used to manufacture the frame 10, the at least one housing 22 comprising: - At least one first cavity 24, the at least one first cavity 24 being used to accommodate at least one corresponding electric motor; - At least one second cavity 26, the at least one second cavity 26 being used to accommodate at least one torque sensor and at least one corresponding crank assembly; and - At least one third cavity 28, the at least one third cavity 28 being used to accommodate at least one corresponding motion transmission mechanism located between the electric motor and the crank assembly.

[0026] In an exemplary embodiment of the frame 10 shown in the accompanying drawings, the first cavity 24, the second cavity 26, and the third cavity 28 are separate from each other. However, it is conceivable that in other exemplary embodiments of the frame, these cavities may be incorporated into a single receiving portion, provided that the receiving portion is capable of accommodating all the main components of the electric motor for the electric bicycle, including or excluding the electronic control unit.

[0027] As an example, such as Figure 4As shown, the electric motor may include a stator 100 and a rotor 102 in a manner known per se, both of which are housed in a first cavity 24 of a housing 22 integral with the frame 10. For example, a torque sensor may include a torque meter 104, which is housed in a second cavity 26 of the housing 22 integral with the frame 10. Again in a manner known per se, the crank assembly 106 may be integral with one or more toothed crowns 110 for chain connection to one or more flywheels (not shown). For example, the crank assembly 106 may be connected to a drive mechanism via a ratchet, and the drive mechanism may in turn be integral with the outer toothed crowns 110. Again, as an example, the motion transmission mechanism 108 may include a planetary reduction gear. As another example, an electronically operated gearbox can also be inserted into at least one of the first cavity 24, the second cavity 26, and the third cavity 28 of the housing 22 integral with the frame 10, thereby the gearbox's drive electronics can also be inserted into at least one of the aforementioned first cavity 24, the second cavity 26, and the third cavity 28 of the housing 22 integral with the frame 10.

[0028] Preferably, the material used to manufacture the frame 10 is a carbon fiber sheet molding composition or CF-SMC. The compounds used can differ and have different mechanical properties, resulting in slight variations in weight. Regardless, the manufacturing technique for the frame 10 remains unchanged: the frame 10 is actually manufactured using a hot plate press molding technique.

[0029] Also preferably, according to the exemplary embodiment shown in the accompanying drawings, the frame 10 includes at least one upper tube 30, which is integrally formed with the seat tube 12 and the lower tube 14 as a single piece, and the lower tube 14 is connected to the head tube 20. However, it is conceivable that the frame 10 may have different shapes depending on the intended use.

[0030] The frame 10 may also include two or more cover elements 32, 34 that enclose the housing 22 on both sides of the frame 10 and are made of the same material used to manufacture the frame 10. The cover elements 32, 34 contain the motor, sensors, and transmission mechanisms, with only the opposite ends of the crank assembly extending from the housing 22. At least one receiving portion 36 may be formed within the lower tube 14 for accommodating at least one corresponding battery (not shown) that supplies power to the electric motor and associated accessory components.

[0031] The method for manufacturing the frame 10 described above first includes a first step of drawing the frame 10 using a CAD ("Computer-Aided Design") system. The frame 10 is drawn using the CAD system such that it comprises at least one seat tube 12, at least one lower tube 14, and at least one head tube 20, the seat tube 12 being configured to support a seat post. The lower tube 14 is integrally formed as a single piece with the seat tube 12 at its lower end 16 and integrally formed as a single piece with the head tube 20 at its upper end 18.

[0032] Furthermore, by using a CAD system to draw the frame 10, at least one housing 22 is formed within the frame 10. This housing 22 is sized to accommodate at least one specific electric motor 100, 102, at least one specific torque sensor 104, at least one specific crank assembly 106, and at least one specific motion transmission mechanism 108, and the frame 10 has no undercut portion. Therefore, the frame 10 already includes the housing 22, which has the space required to accommodate the electric motor, motion transmission mechanism, and sensor.

[0033] The electric motor attached to frame 10 gives the designer considerable freedom to create the shape he or she prefers. This involves advantages both structurally—where a specific solution is required—and aesthetically. There is no particular type of frame to use. In fact, frames for city bikes, endurance bikes, XC bikes, trail bikes, downhill bikes, etc., can be covered. Any type of bicycle or other similar vehicle that can have an electric motor can be manufactured using frame 10 according to the invention. They can be “front-suspension” or “full-suspension” type bicycles, i.e., having only a front shock absorber, or having both a front and rear shock absorber, respectively.

[0034] After selecting the frame type, the next step is to draw the frame and integrate the most suitable electric motor. In the exemplary embodiment shown in the accompanying drawings, starting with a specific electric motor for an electric bicycle, a desired geometry is used so that the same components used to assemble a “single” motor can also be integrated with the frame 10 again. As mentioned above, since the frame 10 is not limited to having attachments for an external motor housing, the geometry can be changed according to design needs. Starting with the motor, a triangular frame 10 is then developed. Then, in the inclined tube 14, also referred to as the “lower tube,” a receiving portion 36 for one or more batteries is formed, which must be sized correctly to accommodate one or more batteries best suited to the selected electric motor type.

[0035] After creating the desired geometry of frame 10, the next step is to manufacture the mold. Figure 5The mold shown as an example includes a first convex mold half M and a second concave mold half F, such that the first convex mold half M and the second concave mold half F can be connected to a press and have the shape of the frame 10 previously drawn using a CAD system. Preferably, the first convex mold half M is designed to be fixed to the upper part of the press, while the second concave mold half F is designed to be fixed to the lower part of the press. The mold can be made of aluminum; however, aluminum allows for the production of a relatively small number of frame components 10. Conversely, if a large number of components are intended to be manufactured, steel molds are recommended because they are more wear-resistant than aluminum molds. The mold can be made as a single piece, or pins can be used for more complex components. This also allows for the replacement of these pins when they wear out or when a specific shape needs to be changed, such as a cavity.

[0036] Several factors should be considered when manufacturing a mold. The first factor is the removal direction. If the intention is to manufacture a simple mold, it is important that the mold has only one removal direction. The removal direction is along the direction in which the mold opens. Since the press opens by moving vertically, the frame 10 must be designed so that the frame 10 does not get stuck in one of the mold halves, and the mold can open without problems or damage to the frame 10. Therefore, the frame 10 must not have any undercut portions. If these undercut portions exist, the mold will become quite complex.

[0037] Equally important is that the mold has an appropriate draft angle. This draft angle can vary between 1 and 3 degrees depending on the position. The draft angle refers to the angle that each surface of the first convex mold half M and the second concave mold half F must have relative to the press plane. The draft angle is used to remove the frame 10 from the mold. If the surfaces of the first convex mold half M and the second concave mold half F are completely perpendicular to the press plane, there is a risk that the frame 10 may not be able to be removed from the mold.

[0038] If the design of frame 10 includes one or more particularly complex surfaces and / or portions present on frame 10, excess material must be left in the mold. In this way, the particularly complex surfaces and / or portions of frame 10 can be manufactured in later stages, such as by subsequent material removal and / or machine tooling. In fact, unlike any carbon fiber part made by lamination, CF-SMC can be machined on a machine tool. Therefore, it is recommended to create a simplified “rough” part compared to the final geometry of frame 10, and then obtain the final geometry by removing material in one or more subsequent operations. In the exemplary embodiment shown in the figures, for example, the holes for mounting the cover elements 32, 34 that enclose housing 22 and the more complex geometry of frame 10 are manufactured according to this concept.

[0039] The thickness of frame 10 must also be considered. For the material to be evenly distributed within the mold, it is important that the thickness of the frame 10 to be manufactured is also uniform. Therefore, a relationship must exist between feasibility, mechanical resistance, and weight. If increased structural rigidity of frame 10 is required and desired, conventional woven carbon fiber layers can be alternated with short carbon fibers of CF-SMC. Similarly, to increase the structural rigidity of the frame, layers of Kevlar fiber or other suitable materials can be inserted.

[0040] When the mold is ready, carbon fiber reinforced polymer composite (CF-SMC) for manufacturing the frame 10 is prepared. The CF-SMC is then cut so that the material has the desired shape of the frame 10 previously drawn using a CAD system. In particular, the housing 22 is formed directly from the material used to manufacture the frame 10, such that the housing 22 includes: at least one first cavity 24 for accommodating at least one corresponding electric motor 100, 102; at least one second cavity 26 for accommodating at least one torque sensor 104 and at least one corresponding crank assembly 106; and at least one third cavity 28 for accommodating at least one corresponding motion transmission mechanism 108 located between the electric motor 100, 102 and the crank assembly 106.

[0041] Preferably, during the CAD drawing step, the frame 10 can be drawn to include at least one upper tube 30, which is integrally formed as a single piece with the seat tube 12 and the lower tube 14, and the lower tube 14 is connected to the head tube 20. The carbon fiber reinforced polymer composite material is then cut so that the material has the shape of the frame 10, which also includes the upper tube 30.

[0042] Preferably, during the CAD drawing step, two or more cover elements 32, 34 may also be drawn, which enclose the shell 22 on both sides of the frame 10 and are made of the same carbon fiber reinforced polymer composite material. The carbon fiber reinforced polymer composite material is then cut so that the material has the shape of the two or more cover elements 32, 34.

[0043] Preferably, during the CAD drawing step, the frame 10 can be drawn to also include at least one receiving portion 36 formed within the lower tube 14 for housing at least one corresponding battery supplying power to the electric motors 100, 102. In this case, the carbon fiber reinforced polymer composite material is then cut such that it has the shape of the frame 10 including the receiving portion 36.

[0044] At this stage, the cut material is placed in the second concave mold F, so that the material completely fills the mold. It is important that the material completely fills the molding volume. The total volume of frame 10, as well as the density and weight of the material used to manufacture frame 10, must be checked using a CAD system. These values ​​should increase by approximately 20% due to some material being discharged from the mold.

[0045] When the material is placed inside the mold, the mold can be closed. Importantly, the first convex mold half M and the second concave mold half F are matched and have the same temperature. At this stage, molding operations can be performed based on predefined values ​​for molding temperature, molding pressure, and pressing time to mold the frame 10. The success of molding depends on temperature, pressure, and pressing time. Pressure and temperature can be easily found in the material data sheet, while the pressing time must be obtained through empirical testing. Once the correct pressing time is determined, it can be reused for each subsequent molding of the same frame 10, provided it is performed under the same operating conditions.

[0046] The designer decides whether to include a method for removing frame 10 in the mold. The removal method is limited to forming a movable portion, such as a pin, in the mold, which allows frame 10 to be ejected when it is stuck in the mold. The pin can be moved by an operator. The presence of this movable portion is not essential, but it will certainly facilitate the production process if necessary. For example, without this movable portion, frame 10 may remain in the mold even with the correct draft angle.

[0047] It is recommended that the frame 10, still unprocessed after being removed from the press, undergo further processing, such as forming multiple cavities 24, 26, 28 with correct tolerances, for example, cavities for accommodating multiple bearings or components with complex shapes of planetary reduction gears. Additionally, holes are made for attaching cover elements 32, 34 to the housing 22. During these post-molding processes, other seats, such as seats for cable passage, can then be formed.

[0048] In the method for manufacturing frame 10, a carbon fiber sheet molding composition or CF-SMC containing chopped carbon fibers is used, which can produce an object with isotropic material properties. In fact, the fibers are randomly arranged within frame 10, giving the frame structural rigidity similar to that of aluminum components. This property allows for the manufacture of complex parts capable of withstanding multi-directional stresses.

[0049] Analysis of the frame 10 according to the invention using the finite element method (FEM) highlights the advantages of the motor housing 22, which is integral with the frame 10, compared to a housing separate from the frame and constrained to the frame by screw connections. Subjecting both designs to a total static load of 200 kg shows that the main stress areas remain unchanged, but the stress acting on the motor housing 22, which is integral with the frame 10, is significantly lower than the stress acting on the separate housing. Integrating the motor housing 22 with the frame 10 is advantageous not only for the frame attachment points but also for the stresses, which have proven well distributed on the side cover elements 32, 34 (fixed to the frame 10 by screws). These side cover elements 32, 34 bear stresses concentrated in their central portions, yet these stresses are lower than those on the corresponding cover elements of the separate housing.

[0050] In fact, the lower tension on frame 10 also means lower deformation. This lower deformation is advantageous in the specific case where the motion transmission mechanism 108 has cascaded reduction gears resting on one of the side cover elements 34. Indeed, by making the gears work in unison with each other, power transmission can be maximized, thereby improving the efficiency of the entire motion transmission mechanism 108, and also protecting the gears from premature wear that may be caused by improper use. It should be emphasized that the side cover elements 32, 34, as well as the frame 10 and the motor housing 22 integral with the frame 10, are made of CF-SMC.

[0051] Therefore, it can be seen that the bicycle frame according to the present invention, and the method for manufacturing the bicycle frame, achieves the aforementioned emphasized objectives. A major advantage in terms of construction is that it eliminates the need for attachments on the frame for receiving the motor housing, thereby maximizing the integration of the motor housing with the frame.

[0052] Furthermore, combining the motor housing and frame into a single unit allows for maximum optimization of every space. Until now, all control components of an electric motor have been located around the same motor. The ability to forge the frame that includes the motor housing also allows the control components to be housed away from the electric motor, avoiding overheating and volume issues.

[0053] Another advantage lies in cost. Manufacturing a frame in an autoclave takes approximately 9 hours (including lamination and time in the autoclave). Furthermore, it requires a skilled operator. In contrast, a CF-SMC frame can be manufactured in a very short time, approximately 20 minutes. Moreover, the operator does not require special skills, as it only requires placing the material in the mold and starting the molding cycle.

[0054] Another advantage lies in weight. The CF-SMC frame, including the integrated motor housing, has an average weight of 2.5 kg.

[0055] However, this bicycle frame design is easily modified and varied, all falling within the same inventive concept; furthermore, all details can be replaced with technically equivalent components. In practice, the materials used, as well as the shape and size, can be arbitrary depending on the technical requirements.

[0056] Therefore, the scope of protection of this invention is defined by the appended claims.

Claims

1. A method for manufacturing a bicycle frame (10), wherein, The frame (10) includes at least one seat tube (12), at least one lower tube (14), and at least one head tube (20), wherein at least one of the seat tubes (12) is configured to support a seat rod, and wherein the lower tube (14) is integrally formed with the seat tube (12) at its lower end (16) and integrally formed with the head tube (20) at its upper end (18), the method comprising the following steps: - The frame (10) is drawn using a CAD system such that at least one housing (22) is formed within the frame (10) and the frame (10) has no undercut portion, wherein at least one housing (22) is sized to accommodate at least one specific electric motor (100, 102), at least one specific torque sensor (104), at least one specific crank assembly (106) and at least one specific motion transmission mechanism (108). - Manufacture a mold including a first convex half-die (M) and a second concave half-die (F) such that the first convex half-die (M) and the second concave half-die (F) can be connected to a press and the first convex half-die (M) and the second concave half-die (F) have the shape of the frame (10) drawn using the CAD system; - Prepare a carbon fiber reinforced polymer composite material for manufacturing the frame (10); - Cut the carbon fiber reinforced polymer composite material such that the material has the shape of the frame (10) drawn using the CAD system, such that at least one of the shells (22) is formed directly from the material used to manufacture the frame (10), and such that at least one of the shells (22) comprises: - At least one first cavity (24), at least one first cavity (24) is used to accommodate at least one corresponding electric motor (100, 102). - At least one second cavity (26), the at least one second cavity (26) being used to house at least one torque sensor (104) and at least one corresponding crank assembly (106). - At least one third cavity (28), at least one of the third cavities (28) is used to accommodate at least one corresponding motion transmission mechanism (108) located between the electric motor (100, 102) and the crank assembly (106). - The cut material is placed in the second concave mold (F) such that the material completely fills the mold; - The total volume of the frame (10) and the density and weight values ​​of the material used to manufacture the frame (10) are checked by the CAD system to ensure that the material completely fills the mold, taking into account that the values ​​increase by about 20% due to some of the material being discharged from the mold; - Based on preset values ​​for molding temperature, molding pressure and pressing time, a molding operation is performed to mold the frame (10).

2. The method according to claim 1, wherein, In cases where the design of the frame (10) includes one or more particularly complex surfaces and / or portions present on the frame (10), excess material must be retained in the mold so that the particularly complex surfaces and / or portions of the frame (10) can be manufactured in a later stage by subsequent material removal and / or machine tooling.

3. The method according to claim 1 or 2, wherein, Where it is necessary to increase the structural rigidity of the frame (10) as required, conventional woven carbon fiber layers are used, alternating with short carbon fibers of the carbon fiber reinforced polymer composite.

4. The method according to any one of claims 1 to 3, wherein, The material is a carbon fiber sheet molding composition or CF-SMC.

5. The method according to any one of claims 1 to 4, wherein, The first convex die (M) is designed to be fixed to the upper part of the press, and the second concave die (F) is designed to be fixed to the lower part of the press.

6. The method according to any one of claims 1 to 5, wherein, The frame (10) is manufactured using hot plate molding technology.

7. The method according to any one of claims 1 to 6, the method comprising the following steps: - The frame (10) is drawn using the CAD system such that the frame (10) further includes at least one upper tube (30), the upper tube (30) being integrally formed with the seat tube (12) and the lower tube (14) as a single piece, and the upper tube (30) connecting the lower tube (14) to the head tube (20); and - Cut the carbon fiber reinforced polymer composite material so that the material has the shape of the frame (10) including the upper tube (30).

8. The method according to any one of claims 1 to 7, the method comprising the following steps: - Using the CAD system, draw two or more cover elements (32, 34) that enclose the shell (22) on both sides of the frame (10), and the cover elements are made of the carbon fiber reinforced polymer composite material; as well as - Cut the carbon fiber reinforced polymer composite material such that the material has the shape of two or more of the covering elements (32, 34).

9. The method according to any one of claims 1 to 8, the method comprising the following steps: - The frame (10) is drawn using the CAD system such that the frame (10) further includes at least one receiving portion (36) formed in the lower tube (14), the receiving portion (36) being used to receive at least one corresponding battery that supplies power to the electric motors (100, 102); as well as - Cut the carbon fiber reinforced polymer composite material so that the material has the shape of the frame (10) including the receiving portion (36).

10. A bicycle frame (10) manufactured by implementing the method according to any one of claims 1 to 9, the frame (10) comprising: - At least one seat tube (12), at least one of the seat tubes (12) being configured to support a seat rod; as well as - At least one lower tube (14), wherein at least one lower tube (14) is integrally formed with the seat tube (12) as a single piece at the lower end (16) of the lower tube (14), and at least one lower tube (14) is integrally formed with the head tube (20) as a single piece at the upper end (18) of the lower tube (14). The frame (10) is made of carbon fiber reinforced polymer composite material, and at least one housing (22) is formed in the frame (10) at the connection between the seat tube (12) and the lower tube (14), and the at least one housing (22) is formed directly from the material used to manufacture the frame (10), and the at least one housing (22) comprises: - At least one first cavity (24), at least one first cavity (24) is used to accommodate at least one corresponding electric motor (100, 102); - At least one second cavity (26), the at least one second cavity (26) being used to house at least one torque sensor (104) and at least one corresponding crank assembly (106); and - At least one third cavity (28), at least one of the third cavities (28) is used to accommodate at least one corresponding motion transmission mechanism (108) located between the electric motor (100, 102) and the crank assembly (106).

11. The frame (10) according to claim 10, characterized in that, The frame (10) includes at least one upper tube (30), which is integrally formed with the seat tube (12) and the lower tube (14) as a single piece, and the upper tube (30) connects the lower tube (14) to the head tube (20).

12. The frame (10) according to claims 10 to 11, characterized in that, The frame (10) includes two or more covering elements (32, 34) that enclose the housing (22) on both sides of the frame (10), and the covering elements (32, 34) are made of the material.

13. The frame (10) according to any one of claims 10 to 12, characterized in that, At least one receiving portion (36) is formed inside the lower tube (14), and at least one of the receiving portions (36) is used to receive at least one corresponding battery that supplies power to the electric motor (100, 102).

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